TRIUMFANNUAL REPORT SCIENTIFIC ACTIVITIES 1987CANADA’S NATIONAL MESON FACILITY O PER ATED AS A JO IN T V ENTU RE BY:UNIV ERSITY OF ALBERTA SIMON FRA SER U NIVERSITY U NIVERSITY OF V ICTORIA U NIVERSITY OF BRITISH COLUMBIAUNDER A CONTRIBUTION FROM TH E NATIONAL RESEARCH COUNCIL OF CANADA J U N E 1988, ■ 'MTRIUMFANNUAL REPORT SCIENTIFIC ACTIVITIES 1987TRIUMF4004 WESBROOK MALL VANCOUVER, B.C. CANADA V6T 2A3OURCEIZEDOURCEBAT HOBIOMEDICALLABORATORY42 MeV ISOTOPE PRODUCTION CYCLOTRONMESON HALLM 9 ( T T / j j )2 0 U i )MESON HALL EXTENSIONINTERIM RADIOISOTOPE LABORATORYNEUTRONACTIVATIONANALYSISTHERMAL M ESON HALLNEUTRON SERVICEFACILITY ANNEXF O R E W O R DIn my second and final year as chairm an of the TR IU M F Board of M anagem ent I have been able to appreciate m any of the qualities which drive this rem arkable project forward. These are excellent friends in O ttaw a and V ictoria, fine leadership, much hope and energy, and, above all, excellent science.The science is described in th is annual report. I t covers a wide range of im portan t research fields and continues to accum ulate its share of kudos. For exam ple, we were very pleased to note th a t in mid-1987 Professor Yam azaki received the Im perial Medal from the E m peror of Japan . He is apparen tly only the fourth Japanese physicist so honoured, and a m ajor portion of his citation perta ins to his m uon work a t TR IU M F.The vigorous steps forward of the cam paign for a KAON factory do count on friends in O ttaw a and V ictoria, and on their appreciation of the opportun ity which th is project provides for C anada. T he strong support of the B.C. governm ent emerged during the year. Jo intly O ttaw a and V ictoria explored foreign partic ipa tion w ith positive results. T he KAON project is now ready for construction approval by O ttaw a. We should also record here the action by our federal m inister, the Honourable Frank Oberle, in adding to T R IU M F ’s base two million dollars during the course of 1987.TR IU M F continues to abound in scientific leaders as is evident to anyone who reads th is report or visits the project. T he leadership is m anifested not only among the experim ental spokesmen from m any universities who have active program s at T R IU M F bu t also am ong those who use TR IU M F as a base for big experim ents abroad. It is these physicists who carry the m om entum of T R IU M F and will lead it on to the KAON project.P.A. LarkinC hairm an, Board of M anagem entT R IU M F was established in 1968 as a laboratory operated and to be used jo in tly by the University of A lberta , Simon Fraser University, the U niversity of V ictoria and the U niversity of B ritish Columbia. The facility is also open to o ther C anadian as well as foreign users.T he experim ental program m e is based on a cyclotron capable of producing three sim ultaneous beam s of protons, two of which are individually variable in energy, from 180-520 MeV, and the th ird fixed a t 70 MeV. The poten tia l for high beam curren ts - 100 fiA a t 500 MeV to 300 /j,A a t 400 MeV - qualified th is m achine as a ‘meson fac to ry ’.Fields of research include basic science, such as m edium -energy nuclear physics and chemistry, as well as applied research, such as isotope research and production and nuclear fuel research. There is also a biom edical research facility which uses mesons in cancer research and trea tm en t.T he ground for the m ain facility, located on the UBC cam pus, was broken in 1970. Assembly of the cyclotron sta rted in 1971. The m achine produced its first full-energy beam in 1974 and its full current in 1977.T he laboratory employs approxim ately 363 staff at the m ain site in Vancouver and 18 based a t the four universities. The num ber of university scientists, g raduate s tuden ts and support staff associated w ith the present scientific program m e is about 530.V ICONTENTSIN TR O D U C TIO N .............................................................................................................................................................. 1SCIEN CE DIVISION ........................................................................................................................................................ 3In troduction .......................................................................................................................................................................... 3Partic le Physics .................................................................................................................................................................. 5Spin correlation param eter A yy in n-p elastic scattering ................................................................................. 5A study of the decay x —► ev .................................................................................................................................... 5R adiative m uon capture w ith the T P C ............................................................................................................... 6M easurem ent of parity violation in p-p scattering ........................................................................................... 6M uonium -antim uonium conversion ....................................................................................................................... 8R atio of spin transfer param eters D t / R t in d(p ,n)pp quasielastic scattering ..........................................10Test of charge sym m etry in n-p elastic scattering a t 350 MeV .....................................................................11M easurem ent of K + —* x +v V ....................................................................................................................................12M easurem ent of K ~ —*Yy ..........................................................................................................................................15T he SLD experim ent ....................................................................................................................................................15Nuclear Physics and C hem istry ...................................................................................................................................... 17In itia l studies of the (n , p ) reaction on light nuclei ........................................................................................... 17Isovector giant resonances in 208P b (n ,p ) and 120S n (n ,p ) ............................................................................... 17Polarization transfer in the pp —* dir reaction .....................................................................................................18R elativ istic m edium effects a t in term ediate energies ........................................................................................ 18S tudy of the ( x + , x +x ~ ) reaction on 160 , 28Si and 40C a a t T n = 240 and 280 MeV ........................... 19T he EELL effect in 4He .............................................................................................................................................. 20Spin transfer m easurem ents in x + d —+j> + p .................................................................................................... 20Energy dependence of T20 and r 21 in x d elastic scattering ............................................................................ 22E xcita tion of “stre tched” particle-hole sta tes in charge exchange reactions.... ...........................................23Zero degree radiative capture of neutrons ............................................................................................................ 24Exchange effects in 0+ —» 0- inelastic scattering ...............................................................................................25A search for the te tran eu tro n ................................................................................................................................... 25Few-body physics via the x d break-up reaction .................................................................................................27Gamow-Teller streng th and giant resonances in 90Z r(n ,p ) a t 198 MeV .....................................................28Energy dependence of the charge asym m etry param eter A(T,r,6) in x d elastic s c a t te r in g .................. 28Study of 48T i(n ,p ) as a test of lifetime calculations for the double b e ta decay of 48C a .....................31Energy dependence of the (p ,n ) cross section for 13C and 15N .................................................................... 31M easurem ents of spin observables using the (p ,p '7 ) reaction ....................................................................... 33M easurem ents of the spin ro ta tion param eter Q as a test of Pauli blocking in proton-nucleusscattering ..........................................................................................................................................................................35Gamow-Teller s trength deduced from (n ,p ) and (p, n) reactions on 54Fe a t 300 MeV .......................... 37T he (n ,p ) reaction on 56Fe and 58Ni ......................................................................................................................39Elastic x ± p differential cross sections a t T n = 30 to 67 MeV ....................................................................... 39Q uasielastic scattering from 12C and 160 ............................................................................................................ 41M easurem ent of x ± d elastic scattering differential cross sections a t Tx = 30, 50 and 65 MeV .........41Nuclear wobble in the rare earth nuclei ................................................................................................................ 42Q uasielastic scattering of I s s ta te nucleons in light nuclei .............................................................................42T he spin-isospin response of 48C a and 9Be from the (n ,p ) reaction a t 200 MeV .................................. 43Research and developm ent studies w ith TISO L ................................................................................................ 44Com plete spin observables for quasielastic p roton scattering from 54Fe a t 290 MeV ...........................45N eutron-proton charge exchange am plitudes ...................................................................................................... 48A study of the Pauli blocking of Gamow-Teller transitions using the 70|72,74G e(n, p )70’72’74Ge reactions ........................................................................................................................................................................... 48T he np —> xd cross section very near threshold ..................................................................................................48Isovector 1+ —► 0+ transitions in the A = 6 system .......................................................................................... 50Strangeness in nuclei v ia the ( x + , K +) reaction ................................................................................................ 51Research in C hem istry and Solid-State Physics ........................................................................................................ 53Pionic chem istry ............................................................................................................................................................53M uon m olecular ions and ion-molecule reactions ...............................................................................................53High pressure m uon spin resonance in liquids .................................................................................................... 55Resolved nuclear hyperfine s truc tu re of anom alous m uonium in sem iconductors ...................................56M uonium in micelles .................................................................................................................................................... 58/xLCR spectroscopy of free radicals ........................................................................................................................ 59Reactions of m uonium w ith halogen ...................................................................................................................... 60M uon catalyzed fusion in HD and H 2+ D 2 gaseous m ixtures .........................................................................61Level crossing resonance of m uonium radicals in micelles ..............................................................................61M uonium and m uon sta tes via rf resonance ........................................................................................................ 62/xSR studies of sub- and supercritical fluids .........................................................................................................65M uon spin ro ta tio n studies of dioxygen and ethylene on silica powder ..................................................... 66p S R study of antiferrom agnetism and high-tem perature superconductivity ........................................... 67T heoretical program .......................................................................................................................................................... ..In troduction ....................................................................................................................................................................70Nuclear struc tu re .......................................................................................................................................................... 70Proton-induced reactions and scattering .............................................................................................................. 71Few-nucleon processes ..................................................................................................................................................72Pion physics ....................................................................................................................................................................73Kaon p h y s ic s ................................................................................................................................................................... 74Electron scattering ........................................................................................................................................................75Sym m etry breaking ...................................................................................................................................................... 76QCD and quark models ..............................................................................................................................................77Lattice gauge calculations ..........................................................................................................................................78Electroweak in teractions ............................................................................................................................................ 79M uon spin ro ta tion ...................................................................................................................................................... 80A PPL IE D PRO G RA M S DIVISION .............................................................................................................................81In troduction .................................................................................................................................................................... 81Biom edical program ......................................................................................................................................................8142 MeV cyclotron fa c i l i ty ............................................................................................................................................85R adioisotope processing (AECL) .............................................................................................................................85Positron emission tom ography (P E T ) .................................................................................................................... 86Beam line 2C and TR IM ............................................................................................................................................ 87M icrostructures and electronics ................................................................................................................................88C Y CLO TRO N DIVISION ................................................................................................................................................92In troduction ....................................................................................................................................................................92Beam p ro d u c t io n ........................................................................................................................................................... 94Cyclotron ..........................................................................................................................................................................96C yclotron developm ent ........................................................................................................................................96rf operation ............................................................................................................................................................101Inflector and correction plates ........................................................................................................................ 102E xtrac tion s y s te m s ..............................................................................................................................................102Vacuum ...................................................................................................................................................................102M ain m agnet power supplies ...........................................................................................................................102Elevating system ..................................................................................................................................................102Ion sources and injection system ...........................................................................................................................103P rim ary beam lines .................................................................................................................................................... 104Control s y s te m ............................................................................................................................................... 205Pro jects ........................................................................................................................................................................ ..A lternative ex traction system ................................................................................................................... 207500 f iA upgrade ............................................................................................................................................... 20830 MeV cyclotron ......................................................................................................................................... 209O perational services ................................................................................................................. 209EX PER IM EN TA L FACILITIES DIVISION .............................................................................................................223Introduction ................................................................................................................................................ 213E xperim ental support ................................................................................................................. 214Nucleonics and IAC ................................................................................................................................. 214D ata acquisition software ................................................................................................................. 215D etector f a c i l i ty ..................................................................................................... 216M W PC fa c i l i ty ’ ’ ’ ’ ’ ’ " ’ ” ’ ' ’ ’ ' ' ’ ’ ' ’ ^ ' ' ‘ ‘ ' ' ‘ ‘ ' ‘ 1 1 7Meson hall ....................................................................................................................................... 217M9 channel ..................................................................................................................................... 217M9 channel upgrade ............................................................................................................................... 217M il channel ................................................................................................................................... 218QQD spectrom eter ..................................................................................................................................... 218M15 channel ............................................................................................................................................... 220/zSR facility ....................................................................................................................................... 220Beam line IB ................................................................................................................................. 221P ro ton hall .......................................................................................................................................... 221Beam line 4B ................................................................................................................................. 221M R S 122A segm ented high-pressure gas cell for (n ,p ) for charge exchange experim ents ___ 123t i s o l ........................................................................................................................................................ ; ; ; ; ; 124D ual arm spectrom eter system /second arm spectrom eter ............................................................. 225Targets ..................................................................................................................................... 227Experim ental facilities engineering ................................................................................... 228A C C ELER A TO R RESEA RCH DIVISION ...............................................................................................................In troduction ........................................................................................................... 232Beam developm ent ................................................................................................................. 233C yclotron ............................................................................................................. 233P rim ary beam lines ............................................................................................................... 237Secondary channels ................................................................................................................. 238Beam line diagnostics ........................................................................................................... 239C om puting services ............................................................................................................................... 240KAON factory ................................................................................................................................. 241TEC H N O LO G Y AND ADM IN ISTRA TIO N DIVISION .................................................................................... 150In troduction ................................................................................................................................... 250Site services ................................................................................................................................... 251Safety program ....................................................................................................................... 252Building program ............................................................................................................................... 252Design Office ............................................................................................................................. 252M achine Shop ............................................................................................................................... 252P la n n in g ................................................................................................................................................................ ..Controls, electronics and com puting ....................................................................................... 253D a ta Analysis C entre ....................................................................................................................... 256A dm inistra tion ................................................................................................................................... 257I XA ccounting ............................................................................................................................................................ 157A dm inistrative d a ta processing ...................................................................................................................... 157M aterials m anagem ent ...................................................................................................................................... 158Personnel ................................................................................................................................................................ 158C O N FER EN C ES, W O R K SH O PS AND M EETIN G S ......................................................................................... 159ORGANIZATION ..............................................................................................................................................................161A PPEN D IC ESA. Publications ................. 164B. Users group ..............................................................................................................................................................172C. Experim ent proposals .......................................................................................................................................... 175xINTRODUCTIONBy the best indicators 1987 was a good year for TR IU M F and its science. A lthough the num ber of employed staff and the funding was exactly the same as for 1986 there was grow th in the num ber of exper­im ents perform ed, the num ber of users partic ipating in experim ents, the num ber of new proposals for ex­perim ents, the delivery of beam to experim ents, the num ber of papers published, the length of th is annual report and, probably, the num ber of m em bers of the public who toured T R IU M F and the coverage of TR I- U M F’s program by the various m edia. M ost of the brief accounts of research progress in this report speak for them selves and the reader is encouraged to browse.T he various activities of T R IU M F, as described in th is report, are in tended to convey how the project fulfills its national purpose. T his purpose has evolved. A lthough the purpose does not appear to be concisely articu la ted anywhere it probably includes all of the following:• to serve as a high-profile laboratory in fundam ental subatom ic science constitu ting C an ad a’s contribution to the world network of large accelerator facilities and aiming to achieve, in th is field, the highest in terna­tional s tandards of excellence• to provide, in subatom ic physics, a program of na tional significance easily accessible to scientists from across the nation• to a ttra c t people and ideas of the highest quality from abroad• to offer substan tia l opportun ities to g raduate s tu ­dent train ing• to act as a catalyst for high technology enterprises w ith appropriate technology transfer program sM any experim ents a t T R IU M F in 1987 carry on the trad itio n which has placed the project on the world m ap of subatom ic science over the past decade. The new work includes a significant leap forward in the search for transition of m uonium to antim uonium . This experim ent addresses the “sense of fam ily” among n a tu re ’s basic building blocks - the quarks and leptons - in enquiring how readily particles change into an­tiparticles. Next, the charge-exchange facility in TR I- U M F’s p ro ton hall now pours out im portan t publica­tions on how the quarks inside a neutron or proton flip over when a neutron or proton in teracts w ith a nucleus. T R IU M F ’s muon beam s have become im portan t tools for probing the properties of high-tem perature super­conductors and, generally, of m agnetism in condensed m atter.Spin-offs a t T R IU M F now abound. T he isotope pro­duction facility is doubling its sales annually. The trea tm en t of deep-seated tum ours w ith pions made great progress in 1987 and is approaching a stage at which national clinical tria ls for specific sites appear to lie ju s t ahead.T he T R IU M F cyclotron produced much beam in 1987 in spite of two m ajor “hiccups” in its perfor­mance. T he m ain rf transform er burned out in August necessitating a repair of more th an a m onth; the twelve jacks which lift the entire upper ha lf of the cyclotron m anifested a m ajor bearing problem which pointed to ­ward their m ajor overhaul in 1988. T he cyclotron is a very large and sensitive machine. Both the high qual­ity of its norm al operation and the strong response to m ishaps are a credit to the operations and m aintenance personnel of Cyclotron Division.Perhaps the greatest continuing source of excite­m ent a t T R IU M F in 1987 was the progress toward a KAON factory. The strong in terest and advocacy of the provincial governm ent of B ritish Colum bia - perhaps unparalleled in the recent annals of C anadian science - have placed th is pro ject on the threshold of construction funding. Development of the technical as­pects o f the KAON pro ject continued throughout the year bu t it was the political a tten tion which the project received which moved it forward.As counterpoint to the main them e of KAON for T R IU M F ’s fu ture we developed in 1987 a Five-Year P lan to guide the pro ject in the absence of a KAON facility. This plan, developed for the Advisory Board on T R IU M F (A BO T) of the N ational Research Coun­cil of C anada, would see m ajor upgrade of T R IU M F ’s present beam intensity and o f the various secondary beam lines. I t would see the p ro jec t’s NRC contri­bution grow by more th an 60% in five years to a new p lateau which promises to keep the project com petitive w ith the o ther meson factories of the world. Of course, the KAON pro ject would give T R IU M F a unique fa­cility of world-leading im portance for several decades. I t now appears th a t th is C anadian project will re­ceive strong support from o ther nations. The case for C anada has become especially compelling.T R IU M F has recently evolved in to a national fa­cility, under the guidance of A BO T. T he project was originally funded, in 1968, as a regional centre of ex­cellence. However, as the field achieved m ajor break­throughs in the 1970s and 1980s the im portance of T R IU M F ’s program s increased and the num ber ofpartic ipan ts from across C anada grew. The program now includes m ost of C an ad a’s subatom ic physicists. Therefore, the jo in t venture which operates TR IU M F is being augm ented. Several universities have been in­vited to jo in in a two-stage process. T he Universite de M ontreal and the U niversity of M anitoba have be­come associate m em bers en route to full m embership. The University of Toronto is an observer on T R IU M F ’s Board of M anagem ent. Looking a t the program of TR IU M F it clearly has, now, a national base of par­ticipants.The T R IU M F Board of M anagem ent has undergone some substan tia l changes. Peter Larkin concludes his service to the Board a t the end of the year having served six years concluding w ith two years of magnif­icent chairm anship. Like the salm on, on which he is a world expert, Peter Larkin has m any m echanism s tosteer his way unerringly through m urky w aters. Alan A stbury retired from the Board and was replaced by a prom inent engineer, Joseph Cunliffe. Karl Erdm an, who has served T R IU M F in alm ost every capacity, re­tired and was replaced early in the year by John W ar­ren, T R IU M F ’s first director and founding father. F i­nally, Morris Belkin was replaced by Denzil Doyle, a well-known technology transfer expert from O ttaw a. We record, w ith great sadness, M orris B elkin’s death in December. He was very helpful and generous to T R I­UM F over m any years and particu larly instrum ental in establishing the Shrum Fund for scientific exchanges w ith the W eizmann In stitu te . He offered a m emorable dinner cruise to T R IU M F and its foreign dignitaries on his large yacht on the occasion of the ten th anniversary celebration in Ju ly of 1986.2SCIENCE DIVISIONIN T R O D U C T IO NT he year 1987 was another excellent one for sci­ence a t T R IU M F. The num ber of proposals subm itted to T R IU M F continued to rise and reached the record num ber of 41 for the Decem ber m eeting of the EEC. In spite of some difficulties m ainly caused by rf prob­lems during the sum m er, the am ount of beam delivered during the year was also a record (331 m A h). During Ju ly we successfully ran for the first tim e w ith average beam curren ts of around 200 pA , double the original design goal of the T R IU M F cyclotron, for two weeks.In particle physics the m ost notew orthy achievement was the setting of new upper lim its for the conversion of m uonium in to antim uonium by E xpt. 304. This ex­perim ent uses a radiochem ical technique which, w ith the d a ta taken this year, will be sensitive to a branch­ing ra tio for th is conversion, forbidden in the standard model bu t allowed in some grand unified theories, of less th an 3 x 10~5. Further runs are planned in 1988 to increase the sensitivity.M ajor pieces of equipm ent were constructed and tested for im portan t experim ents a t Brookhaven (BNL 787) and the SLAC linear collider (SLD). C onstruction was com pleted for BNL 787, a B rookhaven-P rinceton- T R IU M F collaboration to search for the decay K + —► ir+ up w ith two to three orders of m agnitude increased sensitivity over previous m easurem ents. D ata-taking will commence a t the Brookhaven AGS in February 1988. M ost of the appara tus for SLD being m ade at T R IU M F is now com plete and in the process of being shipped to SLAC.T R IU M F ’s longstanding in terest in the N - N in ter­action a t in term ediate energies continued w ith a m ajor new experim ent (182) to m easure A yy in n-p scatter­ing to fu rther constrain N N phase shifts. D ata-taking was com pleted a t four energies. P relim inary results are now coming ou t from a m easurem ent of the ratio R t / D t (332) which finished da ta-tak ing in 1986.T he nuclear physics program in the proton hall con­tinued a t a very high level, w ith twelve im portan t ex­perim ents being com pleted on the (p ,n ) (n ,p ) CHAR- G EX facility. These experim ents covered a very wide range of interest, from searches for G T streng th in s-d shell nuclei such as 54Fe, to looking for giant isovector resonances in m edium and heavy nuclei, to tests of shell model lifetime calculations for double b e ta decay. T he C H A R G EX /M R S complex continued to provideT R IU M F with facilities for doing (p , p ' ) , ( p , n ) and (n ,p ) experim ents a t in term ediate energies which are unm atched anywhere else in the world.In the meson hall the m ain em phasis continued to be on pion scattering and break-up reactions on a polar­ized deuteron target. Experim ent 337 com pleted data- taking on m easurem ents of T20 and t2\ in nd elastic scattering, while E xpt. 331 m ade m easurem ents of the polarization transfer param eters Kt„ and K ss in the 7rd —► pp reaction. A t the end of the year measure­m ents of the vector analysing power of nd —+ pp were in progress in E xpt. 375. E lastic scattering cross sec­tions of pions on protons (E xpt. 394) and on deuteron (E xpt. 399) were also m easured.A nother notew orthy experim ent was 327, which studied the (7r+ , 7r+ 7r~) reaction on 160 , 28Si and 40Ca on M il . The QQD spectrom eter was used in coinci­dence w ith a large stack of p lastic scintillators to detect the outgoing pions.The pSR program continued to find new uses for muons as probes of m atte r. This year the em phasis was using m uons to probe the m agnetic properties of the new high tem pera tu re superconducting m aterials, the discoverers of which received this y ear’s Nobel prize. Groups from Bell Labs, U niversity of Tokyo and UBC have all been very active th roughout the year, under the general auspices of Expt. 469. The level cross­ing resonance technique continues to find m any appli­cations ranging from elucidating anom alous m uonium form ation in sem iconductors (E xpt. 367) to free radical chem istry (E xpt. 398). More trad itiona l areas of ^SR, such as high pressure /rSR in liquids (E xpt. 362) and reactions of m uonium w ith halogen gases (Expt. 420) con tinue to p rosper. T h e year fin ished on a fine no te w ith the first observation of the m uon spin echo phe­nomenon (E xpt. 449), which promises to have im por­tan t applications in condensed m a tte r in the future.The Theory group continued to play a v ital and stim ulating role in the work of the Science Division. As well as carrying ou t a w ide-ranging research pro­gram , the group is responsible for organizing our pro­gram of short- and long-term visitors. In teractions be­tween theory and experim ent, which are so successfully fostered by the Theory group, are essential to the long­term v ita lity of the experim ental program .3The contributions on individual experiments in this report are outlines intended to demonstrate the extent o f scientific activity at T R IU M F during the past year. The outlines are not publications and often contain preliminary results not intended, or not yet ready, fo r publication. Material from these reports should not be reproduced or quoted without permission o f the authors.4P A R T IC L E P H Y S IC SE x p e rim e n t 182S pin co rre la tio n p a ra m e te r A yy in n-p e lastic s c a tte r in g(W.T.H. van Oers, W.D. Ramsay, Manitoba)T he purpose of th is experim ent was to m easure the spin correlation param eter A yy in n-p elastic scattering to an accuracy of ±0.03 a t 220, 325 and 425 MeV over the angular range 50° to 150° in the centre-of-mass system . T he m easurem ent was carried out by scat­tering polarized neutrons from polarized protons in a frozen spin ta rg e t (FST ) and determ ining the asym­m etry w ith different n-p spin correlations.Polarized neutrons, produced a t the LD 2 ta rget in beam line 4A by transverse polarization transfer from polarized protons, were collim ated through the 9° port; the spin direction was ro ta ted to the vertical plane by two spin precession dipoles (Bonnie and Clyde). The recoil protons were detected in proton range counters consisting of time-of-flight s ta r t and stop counters and four delay-line cham bers. The scattered neutrons in coincidence were detected in 105 cm x 105 cm scintil­la to r arrays. The details of the experim ental set-up can be found in the U niversity of M anitoba In term ediate Energy Progress R eport, 1986, 1987. T he frozen spin target consisted of bu tanol beads contained in a 5 cm high, 3.5 cm wide and 2 cm thick rectangular box. In order to reduce the m ultiple scattering of the forward and backward scattered protons we had two orientar tions of the target. Initially for the angular range of 90°-150° (c.m .) the ta rg e t was set w ith its 3.5 cm side perpendicular to the neutron beam . For the the rest of the angular range (50°-90° c.m .) the target was ro­ta ted by 90° so th a t 3.5 cm side was along the beam direction.In order to select n-p elastic events from n-np back­ground we have form ed four kinem atic constraints, viz.:(1) Energy sum: Tp + Tn(2) Transverse m om entum sum:Pp sinOp cosp + Pn sin0„ cosn(3) O pening angle: 9P + 6n(4) C oplanarity: p + nIn calculating the opening angle the deflection of protons in the FS T m agnetic holding field is taken into account. By knowing the flux norm alized left (L ) and right (R ) counts one can then ex trac t the spin correla­tion param eter A yy as follows:a - 1 t * - 1* m” PB P r ( X + l )whereX 2 — (L++ + ^ — )(-ft++ + &— ) r<)\(£ + _ + L _ + )(R + _ + R _ + )Pb and Pp are the beam and ta rg e t polarizations, re­spectively. T he subscripts, + + ,H — , — h ,— , are four different com binations of beam (first index) and target (second index) spin orientations.T he m axim um target polarization obtained during the run was 82% w ith a m axim um decay tim e of 765 h. T he ta rg e t polarization as m easured by an NM R sys­tem is known to no b e tte r th an 4%, however, the present experim ent required th a t it should be known to an absolute accuracy of 2%. W ith th is in m ind we have perform ed an independent calibration of the NM R sys­tem using unpolarized protons a t the beginning and end of each d a ta taking run. An unpolarized beam of 500 MeV protons im pinged on a stack of graphite and produced protons by elastic scattering . T he protons scattered a t 9° passed through the neutron collimator and a superconducting solenoid (Superm an), which ro­ta ted the unw anted polarization of the secondary beam by 90°. T he protons scattered from the FS T were de­tected in pro ton range counters set a t 24°. The recoil protons were detected in the central region of the big scintillator arrays set a t 61°. Note th a t a t this an­gle and energy the p-p analysing power is very accu­rately known [Greeniaus et al., Nucl. Instrum . M ethods A 3 2 2 , 308 (1979)]. T hus by m easuring the asymme­try and knowing the analysing power we m easured the target polarization to the required accuracy.T he prelim inary d a ta for A yy a t 325 and 220 MeV are p lo tted in Fig. 1. The predicted values from differ­ent phase-shift analyses and nucleon-nucleon potentials are also shown. We also ex trac ted the analysing pow­ers over the same angular range a t all three energies.E x p e r im e n t 248 A s tu d y o f th e d ec ay tt —*■ ev (T. Numao, TRIUMF)T he m ain goal of the present experim ent is to im­prove the m easurem ent accuracy of the branching ratio R = (7r —* e v ) / ( i r —► p v) by a factor of three in order to provide a m ore stringent test of universality of weak interactions for different generations.The data-tak ing was com pleted in 1986 and about 3 x 1057r —► ev decay and 2 x 108 n-v-e chain decay events were recorded. Extensive analyses have been done in the areas of system atic d a ta calibration, scan­ning full d a ta sets and M onte C arlo sim ulations.5Angle (c .m .)b )Angle (c .m .)Fig. 1. (a) A yy a t 325 MeV, (b) A yy a t 220 MeV.A background-suppressed 7r —» ev spectrum has been exam ined for evidence of massive neutrinos [Azuelos et al., Phys. Rev. L ett. 56, 2241 (1986)] and other exotic particles [Picciotto et al., Phys. Rev. D, in press], A signal of the decay 7r —+ e v M , where M is a m ajoron or o ther neu tral boson escaping the detec­tor system w ithout any interactions, was sought in the 7r —► ev spectrum . Upper lim its of the branching ra­tio (90% C.L.) were obtained for hypothetical bosons in the m ass region 0-130 M eV /c2 and are shown in Fig. 2. T he decay ir —* e v v v was also sought in the sam e spectrum and an upper lim it 3.5 x 10-6 was ob­tained.E x p e r im e n t 249R a d ia tiv e m u o n c a p tu r e w ith th e T P C( G. Azuelos, TRIUMF)R adiative m uon capture (RM C) is a weak semilep- tonic process which is particu larly sensitive to the in­duced pseudoscalar form factor gp o f the hadronic cur­rent. T his experim ent is to m easure RM C on light nu­clei to investigate its possible renorm alization in the nucleus, and is a precursor to a m easurem ent of RMC on hydrogen (E xpt. 452). T he experim ent has been described previously (1986 annual report, p. 8); data-Fig. 2. Branching ratio lim its for r —► e v M process vs. mass of the M particle.taking was com pleted in May. M easurem ents have been m ade of RM C on calcium , oxygen and carbon; the photon energy spectra ob tained w ith a 1.0 m m thick Pb converter are shown in Fig. 3. Only the region of the spectrum above about 57 MeV is usable, due to the unavoidable background for brem sstrahlung of Michel electrons. D a ta have also been obtained on the various backgrounds (pion-induced, cosmic-ray, muon- decay brem sstrahlung) and contributions to the final system atic error. D ata analysis is well under way, in­cluding a full M onte Carlo of the experim ent based on the CERN program G EA N T. T he s ta tis tica l error on the RM C ra te for each nucleus is less th an 5%; the final system atic error is expected to be less th an 10%.E x p e r im e n t 287M e a s u re m e n t o f p a r i ty v io la t io n in p-p s c a t te r in g (J. Birchall, W.T.H. van Oers, Manitoba; G. Roy, Alberta)The parity-violating longitudinal analysing power A z arises from the interference of opposite parity am ­plitudes in p-p scattering . In general, A z (9) is ex­pressed as a linear com bination of parity-m ixed partia l wave am plitudes: [(1S0-3F>o), ^ T Y 1^ ) , C ^ V 3-^ ) • • •] in order of increasing angular m om entum , where the angular d istribu tion of each term is governed by the strong in teraction . T he relative strengths of each term are determ ined by m atrix elem ents of the weak me­son exchange in teraction and m ust be calculated using appropriate wave functions. T he weak meson-nucleon couplings hpp and h^f con tribu te to the lowest-order (1P0-3Po) te rm w ith approxim ately equal weight. In contrast, the (3 P 2 -1 D'l) which contributes significantly to A z above 100 MeV is alm ost entirely due to weak p exchange [Simonius, A IP Conf. P roc. 150 (AIP, New York, 1986), p. 185 and private com m unication].M easurem ents of A z a t 15 and 45 MeV [Kistryn et al., Phys. Rev. L ett. 58 , 1616 (1987) and references therein] have established the lowest partia l wave con­tribu tion as (1 .5 ± 0 .2 )x l0 - 7 . To date no interm ediate-Gamma Ray Energy (MeV)Gamma Ray Energy (MeV)Fig. 3. Photon energy spectra from RMC on calcium, carbon and oxygen.energy experim ent has been perform ed, and the higher partia l wave contributions are undeterm ined. A unique s itua tion exists a t 230 MeV, where the contribution of the lowest partia l wave vanishes [Simonius, op. cit.] in the expression for A z . T his is purely a strong in ter­action effect; the angular d istribu tion of the ( 15 o-3i ’o) term in tegrates to zero from 0 to 90° in the centre ofm ass a t 230 MeV, w ith no dependence on the values of the weak meson-nucleon coupling strengths. To an ex­cellent approxim ation a t th is energy, the longitudinal analysing power in p-p scattering m easures the (3P 2- l D 2) te rm alone, which in tu rn is dom inated entirely by the p exchange contribution. Thus, a m easurem ent of parity violation in p-p sca ttering a t 230 MeV affords a unique opportun ity to m easure hpp .An angular d istribu tion m easurem ent was originally considered preferable from an experim ental standpoint due to the extrem ely sm all predicted value [Simonius, op. cit.] of the to ta l asym m etry A z ~ 4 x 10~8, which resulted from the vanishing of the ( 1S’0-3Po) contribu­tion. A t the Sym posium /W orkshop on P arity Viola­tion in Hadronic Systems held a t TR IU M F in May it was determ ined th a t an ou tdated value of the anom a­lous isovector m om ent used in the calculation had re­sulted in a factor of two underestim ate of A z . Thus, a m easurem ent of A z a t 230 MeV to a precision of ± 2 x 10 - 8 , as has been achieved a t lower energy, will provide a significant constrain t on the weak p-nucleon coupling.To determ ine the parity-violating analysing power A z a beam of longitudinally polarized protons a t 230 MeV will be scattered from a liquid hydrogen target, and the helicity dependence of the to ta l elastic sca tter­ing cross section will be m easured. T he longitudinal analysing power can be m easured in two ways: by col­lecting the forw ard scattered protons in a large solid angle detector and norm alizing the scattering signal to the incident beam flux, and by m easuring the beam current to high precision before and after the liquid hydrogen target.T he P P IC noise tests discussed in last year’s progress report indicated th a t it is possible to mea­sure A z by both the scattering and the transm ission m ethods sim ultaneously, to com parable sta tistica l ac­curacy. Excluding the tim e required to perform control and calibration m easurem ents, the required statistical accuracy of ± 2 x 10~8 can be achieved by both m eth­ods in approxim ately 200 h of running tim e a t 500 nA, Pz — 0.8. Since the system atic errors in the two cases are very different, a com parison of the scattering and transm ission m ethods will provide a unique and invalu­able check on the experim ental results.In last year’s progress repo rt we reported tests of a beam position servo system which was able to hold the beam position fixed a t a given location. In October this year we tested a double loop system to hold the beam position fixed a t two locations simultaneously. We also tested a new higher curren t amplifier for the m agnetic beam deflection system .A pro to type scattering detector is shown in Fig. 4.It is a p lanar ionization cham ber filled w ith hydrogen7iFig. 4. Prelim inary design of a prototype ionization cham­ber scattering detector. Beam enters from the left.gas a t a pressure of 1 a tm . There is a central high voltage plane, in fron t and behind which is a sym m etric arrangem ent of sense planes a t ground po ten tia l to col­lect the charge released by protons travelling through the hydrogen gas. T he back plane is m ounted on a rigid back plate. T he prim ary proton beam passes through a central hole in the cham ber so as to avoid heating of the gas and scattering of protons from entrance and exit windows.T he m ost im p o rtan t system atic error in the m ea­surem ent of the parity-violating analysing power is due to the beam polarization no t being entirely parallel to its m om entum . T his is because an error is induced which is propro tional to the first m om ent of transverse beam polarization. It is therefore essential to be able to m easure the d istribu tion of the transverse com ponents of polarization across the beam profile.A pro to type design of a polarim eter to do th is is il­lustra ted in Fig. 5. T he polarim eter contains a carbon blade which is scanned across the beam . As the ver­tical blade moves across the beam two detectors (left, right) count the protons scattered from the blade. The left-right sca ttering asym m etry m easures the vertical com ponent of polarization of th a t p a rt of the beam in­tercep ted by the rod. A fter a horizontal scan the blade is ro ta ted by 90° and is scanned up-down through the beam . A pair of up-down detectors then measures hor­izontal com ponents of beam polarization. A novel fea­tu re of th is design is th a t the up-down and left-right de­tectors move w ith the blade. T his reduces system aticFig. 5. Sketch of the scanning polarim eter. The carbon blade is shown in the vertical position. The scattering de­tectors are contained in the ring downstream of the blade.errors in the m easurem ent of transverse polarization by two orders of m agnitude.E x p e r im e n t 304M u o n iu m -a n tim u o n iu m c o n v e rs io n (A. Olin, TRIUMF/Victoria)T his experim ent is a search for p,+ e~ —+ /r~e+ , a re­action forbidden by lepton num ber conservation. This process can arise na tu ra lly in theories w ith M ajorana neutrinos, especially if the neutrino masses are pro­duced via a coupling to a new lepton num ber violating Higgs particle.The experim ental set-up is shown in Fig. 6 . Muons from M15 are m oderated and stop near the back of a 10 m g /cm 2 th ick layer of SiC>2 powder w ith 7 nm par­ticle diam eter. T he therm alized m uonium (M u) atom s diffuse from the powder across a 2 cm vacuum gap to a 50 nm W O 3 layer evaporated onto a Mo foil. Con­verted fi~ then cap ture on W atom s to produce 184Ta. A pproxim ately 50% of the recoiling T a atom s rem ain in the foil, which is removed from the vacuum system after a 12 h exposure. In order to prevent the form ation of a surface layer on the W O 3 the evaporation is done in an antecham ber, and then im m ediately introduced into the UHV cham ber near the SiC>2. T his cham ber was m aintained a t a pressure of ~ 1 0 ~ 8. Three layers of m agnetic shielding were used to reduce the m agnetic field seen by the Mu to <10 mG.8y prompti. 1 i i i i I i i i i IUHV RoughingFig. 6 . Vacuum system for the muonium exposures.( 0 - 7 > {M X350 400 450 500 550 350 400 450 500 550KEV KEV^prom pt Tdelayed ’7/ )prom pt’7/delayed350 400 450 500 550 350 400 450 500 550KEV KEV7 prompt ^delayed ( ^ ’7/ )prompt’7/delayedi350 400 450 500 550 350 400 450 500 550KEV KEVFig. 7. Spectrum after counting a 0.45 m g/cm 2 W O 3 sur­face in which 130,000 n~ had been stopped. The 414 keV gam ma is characteristic of 184Ta. The effects of the var­ious coincidence requirem ents on signal and backgrounds are shown.KEV KEVFig. 8. Spectrum of WO3 surface exposed to muonium for 10 h.9T he efficiency of our appara tu s for detecting p~ has been m easured experim entally by exposing W O 3 sam ­ples to a carefully m easured flux of stopping p~ and detecting the resulting 184T a in our low-level counting appara tus. We show in Fig. 7 results for a 450 p g /c m 2 ta rget in which 130,000 fi~ had been stopped. The effect of the various requirem ents on both signal and backgrounds are clearly seen, and the rates observed confirm our initial estim ate of the relevant p + -capture yields. Background count rates have been m easured by exposing 12 p W foils to a p + beam . From this test we expect a background 414 keV count every 100 shifts. The count ra te from n a tu ra l radioactiv ity in the detector and shielding is less th an 1 count/40 shifts.T he emission of m uonium from silica powder was studied in an earlier run by stopping a beam of muons in a 13 m g /cm 2 powder layer inclined at 60° to the beam direction. T he stopping d istribu tion in the pow­der was varied by adjusting the beam m om entum , and the yields into the vacuum were m easured. The re­sults were incom patible w ith a simple diffusion model for the m uonium . However, a model where the muo­nium escapes from an agglom erate w ith an exponential tim e d istribu tion , and then diffuses between the grains, seems to give a good account of the vacuum yields, allowing ex trapo lation to different stopping distribu­tions.Surface monolayers depositing on the W O 3 surface could prevent the therm al m uonium from reaching the W atom s. We have studied the ra te of accretion of m onolayers on these surfaces a t SFU using X-ray pho­toelectron and Auger electron spectroscopy techniques. T he thickness of the surface layers was estim ated from the streng th of the carbon signal and the attenuation of the tungsten line. On the basis of th is m easurem ent we calculate th a t in 12 h a t a pressure of lx lO -8 10% of a monolayer will be deposited. In our appara tus we have achieved a vacuum of 2 x l 0~ 9, b u t typical opera­tion has been a t lx lO - 8 .We have com pleted 12 successful 12 h exposures of W 0 3 -coated foils. Figure 8 shows results of counting a ta rget exposed for 12 h for evidence of 184Ta. Based on these exposures we expect th a t th is m easurem ent was sensitive tor(/z+ e —► p e+ ) T(p —> evv)< 3 x 10-Further runs are planned to increase the sensitivity and to explore fu rther the vacuum m uonium mechanism.E x p e rim en t 332R a tio o f sp in tra n s fe r p a ra m e te rs D t/R t in d(p,n)pp q uasie lastic s c a tte r in g(C.A. Davis, Manitoba)T he ra tio of W olfenstein spin transfer coefficients dt (vertical-to-vertical spin transfer) and rt (sideways-to- sideways spin transfer) in quasielastic scattering from deuterium d(p, n)pp has been m easured a t four energies a t 9n = 9° (lab). As the ra tio can be determ ined in a m anner which is independent of the analysing powers of the polarim eters for m easuring the polarizations of the protons and neutrons, overall system atic norm al­ization errors are elim inated.The analysis of th is experim ent has been completed and the results are given in Table I. T he ra tio D t /R t for free np sca ttering has been corrected for deuteron D s ta te and final-state in teractions. D t / R t p lo tted as a function of energy and com pared to several present- day phase-shift predictions is presented in Fig. 9.P u ttin g these results into the C200, C300, C400 and C500 phase-shift solutions of A rn d t’s SAID program , we can make the following sta tem ents: T he values of e 1 and €3 are reduced, ej being com paratively flat (~ 4 °) over the 200-500 MeV region. 3S'i, 3D \ , 3 £>2 and es­pecially 1P’i are all affected, the rough area aroundTable I. Results for quasielastic dt/ r t and deduced D t/R t , where the final errors in D t/ R t also include an error due to uncertainty in knowledge of the ATn cut. The results have been corrected for target background.Tp(MeV)W (c.m.) (MeV)0„(c.m .)(deg)dt/rt(v a lu e )± (s ta t.)i(sy s .)D t/R t222.7 1986.2 160.98 0.0144±0.0064i0.0033 -0 .0190 i0 .0072324.1 2033.6 160.54 -0 .1 9 1 6 i0 .0 0 4 6 i0 .0 0 3 2 —0.2328i0.0057424.8 2079.6 160.11 -0.3380±0.0045±0.0050 —0.3731±0.0068492.1 2109.8 159.82 —0.4391±0.0085±0.0060 — 0.4892i0.010710Deduced free np from d(p,n)pp al 9 deg. n Lab. AngleEnergy (MeV)Fig. 9. The ratio D t / R t ■ Our d a ta (solid squares) are compared to the phase-shift predictions of A rndt (SM87, solid line), the Saclay phase shifts (in two energy regions, dash lines), and the BASQUE phase shifts (dot-dash line), all derived from SAID.300 MeV tending to be sm oothed out. There are, how­ever, large correlations, especially C(e\ x £3). We hope to reduce these correlations and fu rther improve the phase shifts by addition of our A nn and P d a ta which are being analysed now (see E xpt. 182, p. 5).E x p e r im e n t 369T e s t o f c h a rg e s y m m e try in n-p e la s t ic s c a t te r in g a t 350 M eV(W .T .H . van Oers, Manitoba; L.G. Greeniaus, TRIUMF)An experim ent sim ilar in m ost respects to our re­cently com pleted T R IU M F E xpt. 121 is being prepared for da ta-tak ing in the w inter of 1988-1989. The exper­im ent will m easure the difference in analysing powers A n and A p (where the subscrip t denotes the polar­ized nucleon) in neutron-proton elastic scattering at 350 MeV. Designed as a null m easurem ent, the exper­im ent will achieve an accuracy in A A — A„ — A p of ±0.0008 (or ±0.026° in the zero-crossing angle.O ur m easurem ent of A A a t the zero-crossing angle a t an incident neutron energy of 477 MeV has yielded A A = (37 ± 17 ± 8) x 10- 4 . This result should be com pared to the range of values from the m ost recent theoretical calculations of (21-74) x l0 ~ 4. These calcu­lations include (collectively) estim ates of contributions from direct electrom agnetic effects, the neutron-proton m ass difference in one-pion and p exchanges, and the isospin m ixing p°-u> meson exchange. Some other sm aller effects have also been evaluated. A lthoughthe various predictions are sim ilar in m agnitude, they differ significantly in their detailed predictions. The Iqbal, T haler and W oloshyn (IT W ) calculation [Phys. Rev. C 36, 2442 (1987)] is substan tia lly lower than those by Miller, Thom as and W illiam s (M TW ) [Phys. Rev. L ett. 56, 2567 (1986); Univ. of Adelaide preprint A D P-87-21/T40], Ge and Svenne (GS) [Phys. Rev. C 34, 756 (1987)] or Holzenkamp, Holinde and Thom as (HHT) [Univ. of Adelaide p reprin t A DP-87-21/T38]. HHT also predict a different energy dependence than the o ther calculations. T he differences between the theoretical predictions are the source of much discus­sion. In Fig. 10 the M TW , H H T and GS predictions a t 350 MeV are com pared. T he electrom agnetic term accounts for much of the M W T -G S difference. The M T W -H H T difference is due to the trea tm en t of the p and p°-ui term s. CSB experim ents sensitive to the region away from the cross-over angle can possibly dis­tinguish these la tte r term s and m ay be able to make a stringent test concerning the meson exchange picture of the N N in teraction a t short distances.T he 350 MeV m easurem ent will be perform ed in the m anner of the recently com pleted E xpt. 121. R ather th an m easuring the asym m etry difference directly, the angles a t which the asym m etry crosses through zero will be determ ined. T his difference between the zero- crossing angles is directly proportional to the difference in asym m etries a t th a t angle. Using th is technique we perform a null m easurem ent where the m ajority of pos­sible system atic errors cancel because the A„ and A p m easurem ents are m ade w ith exactly the same physical apparatus. T he only changes are to the polarizations on the beam and target.o >o to »0 »0 ISO 110Angle (cm)Fig. 10. Comparison of the A A angular distribution from M TW , GS and HHT. Differences are described in the text. The arrow shows the point where the analysing power crosses through zero. The angular range of the experiment is also shown.11T he solid angle for th is experim ent will be consider­ably larger th an for E xpt. 121. T his will allow us to choose an angle region th a t is asym m etric about the cross-over angle and to a ttem p t a m easurem ent where the in teresting p°-u> te rm is relatively large.T he new experim ent is essentially identical to the successfully com pleted pro ject a t 477 MeV. The m ajor differences com pared to E xpt. 121 are:1) Larger solid angle — increased event ra te w ith only a m arginal loss in discrim ination against back­ground. Trigger ra te due to (n , np) events will increase. We have recently ex trac ted the angular d istribu tion of the charge sym m etry breaking effect in the 477 MeV da ta . W ith the increased precision and larger angle range we should be able to distinguish the presence of the p°-u) m ixing term a t a level of about ±0.0015 in a bin of a few degrees.2) Wedge degrader removed — increased trigger ra te due to (n ,n p ) events which will be elim inated off line. Some analysis problem s will be elim inated. Fewer n- p elastic events will be lost due to reactions in the degrader.3) FST volume reduced to 35 cm3 and a rectangu­lar shape used. This m aintains the energy loss and m ultiple sca ttering of the protons a t the values of the previous experim ent.4) T he neutron beam will have higher intensity and polarization. T he la tte r reduces the tim e required to achieve a given precision and makes the two aspects of the experim ent m ore sim ilar.5) T he system will allow a secondary target to be viewed for control purposes and background checks.6) Incorporation of front-end intelligence — elimina­tion of (n ,np ) background due to the high anticipated trigger ra te . T h is will necessitate a J 11 processor in the CAM AC branch. T his is a result of our desire to increase the solid angle even m ore th an in E xpt. 121.M easu rem en t o f K + —*■ x+ vvB N L 787 ( B N L -P r in c e to n -T R IU M F c o lla b o ra t io n )(D. Bryman, TRIU M F/Victoria)The decay K + —*■ tt+ X ° (where is one or more light, neu tral, weakly in teracting particles) will be searched for a t the level < 2 x lO -10 in E xpt. 787 a t Brookhaven N ational Laboratory by a collabora­tion from BNL, Princeton U niversity and TR IU M F. K + —*■ 7r+ v v offers a unique testing ground for higher- order weak effects in the stan d ard model not dom i­nated by long-distance effects. Recent observations of bb m ixing could im ply a branching ra tio as high as 10-9 for K + —*■ ir+vv due to large mixing angles and a high m ass for the top quark. O bservation of a signal in th is region would serve to validate the standard modelw ith three generations and place severe constrain ts on its param eters.T he observation of an apparen t K + —► tt+vV sig­nal above 10-9 would serve as a d ram atic indicator of the presence of new physics. T he least exotic pos­sibility is the occurrence of add itional generations of neutrinos. O ther possibilities include the production of the supersym m etric partners of the photon, gravi­ton and the Higgs. In some versions of supersym m e­try the decay K + —► 7r+ 7 7 could occur a t almost the current experim ental lim it for K + —+ ir+uV which is 1.4 x 10- 7 . Any proposed in teraction which induces neu tral flavour-changing processes (e.g. technicolour) will also contribute to the K + —► tt+vv ra te . Conse­quently, a large window for possible new physics exists.T he experim ent will also be sensitive to o ther in­teresting decays such as K + —+ 7r+ 7 7 , K + —> pe, K + —► 7r+ e+ e~, K + —» 7r+ /r+ /i~ , K + —>■ p +vvV, K + —*• e+ 1/7 .Figure 11 shows the appara tus which is nearing com­pletion. The detector is designed to have a large geo­m etrical acceptance (27r sr) for the K + —► n + vV decay mode while m axim izing the rejection of background processes such as I<+ —* p +v ( K ^ ) , K + —* p +v y and K + —*• 7T+ 7r° ( K v 2) and others. Sensitivity for iden­tification of unaccom panied pions from K + —*■ tt+ vV is accomplished through m easurem ent of m om entum , kinetic energy, range, decay sequence 7r —* p —* e, and efficient rejection of b o th single photons and photons from 7r° decay.T he 800 M eV /c K + beam is b rought to rest in a 10 cm diam eter ta rg e t consisting of groupings of scin­tillating fibres 2 m m in d iam eter. T he decay pions pass through a cylindrical d rift cham ber which m ea­sures their m om enta in the 1 T m agnetic field w ith resolution a&p < 2%. T he pions then stop in a plastic scintillator range stack which also contains M W PCs. Each range stack counter is viewed from bo th ends by 2 in. pho to tubes read ou t by transien t digitizers. The digitizers record a com plete history of scintillator light o u tp u t as a function of tim e. T he to ta l energy of the decay pions will be m easured by sum m ing the pulse heights of the ta rg e t and range array elem ents w ith an anticipated resolution 7 photoelectrons/M eV deposited in all modules. Several m odules were tested in the TR IU M F meson beam . T he energy resolution for a 50 MeV elec­tron beam entering the centre of the m odule wasa_ _ 5.7%E ~ V E ( GeV) ‘This is com patible w ith a contribution from sampling fluctuations of 5% and from photostatistics of 2.5%.D uring the past year we bu ilt and tested the two endcap detectors. B oth encaps were installed in the m agnet a t Brookhaven and tested . From d a ta taken in the M ay run we conclude th a t a sam ple of K ^ events leaving ~ 60 MeV in one single m odule is adequate to m onitor the gain and relative balance of the module during data-tak ing . A special trigger is being imple­m ented for the fu tu re data-tak ing runs.Tw o options are being pursued for the construction of 500 MHz 8-b it transien t recorders: a FADC ap­proach a t BNL based on a new device m anufactured by Tektronix and a po ten tia lly low cost (<200/channel) device based on the developm ent of a gallium -arsenide charge-coupled device (CCD ) a t T R IU M F. The CCDs being fabricated on gallium arsenide by the TR IU M F group are of the buried channel variety. T he diode array consists of Schottky diodes.P ro to type CCD devices have been produced and are undergoing m easurem ents. The devices have 64 charge buckets which would allow storage for 128 ns a t 500 MHz. I t is intended eventually to produce a 128- bucket device. The in itia l device has exhibited charge transpo rt over a frequency range of 1 to 500 MHz. A new m icrostructure labora to ry for production of the CCDs was bu ilt a t T R IU M F. Developm ent of ancil­lary logic, supervisory and FASTBUS digital readout are also in progress a t T R IU M F in collaboration with M icrotel Pacific Research C orporation.T he beam counter system consists of several scin­tillators, two scin tillator hodoscopes, three planes of M W PCs and a Cerenkov counter. All b u t the la tte r were bu ilt a t T R IU M F. T he M W PC s use a fast C F 4 gas m ixture and special hom e-built hybrid electronics including the post am plifier/d iscrim inator system built for the central drift cham ber.In the past year the d a ta acquisition system was first used for extensive testing of the drift cham ber at TR IU M F. It was la ter tested a t BNL during the May run. The original 2-crate system was extended to a 10 FASTBUS crate front-end system . M uch effort has also gone into commissioning and developing testing m ethods for FASTBUS crates full of pipeline TDCs.A t present we are developing a system for filter­ing d a ta prior to tap ing using the Ferm ilab Advanced C om puter Program . A nother A C P system will per­form off-line analysis a t T R IU M F. T he first step was to install a three-node m ultiprocessor system . Extensive hardw are tests were done to understand the function­ing of the system . Software was developed to allow processing of the d a ta gathered last M ay as well as analysis of the drift cham ber test data .W ork has proceeded on reconstruction routines for the various detector subsystem s. Extensive analysis of the d a ta collected last M ay is under way. T he gen­eral off-line analysis program called K O FIA has been released to all partic ipa ting in stitu tions and is being m aintained on six VAXes across the continent by the T R IU M F group. M uch effort has gone in to properly docum enting the program .A custom system for m anagem ent of all calibration d a ta needed by the detector has been developed. Con­tro l and m onitoring of all d rift cham ber param eters is now operational via a CAM AC p a th separate from the d a ta acquisition pa th . T he VAX-based d a ta acquisi­14tion program has been significantly improved.T he E787 m agnet was com pleted in April and the field was m apped by a T R IU M F group. Following the one-week May test run detector assembly has contin­ued through to the present w ith com pletion scheduled for December. F irst beam is expected for E787 during the period Jan u ary to June 1988.M e a s u re m e n t o f K ~ —* Y 7B N L 811 (B N L -B o s to n -C a s e W e s te rn -N e w M ex ico - T R IU M F -U B C c o l la b o ra t io n )(B.L. Roberts, Boston; D.F. Measday, UBCT his experim ent is studying the in teractions of low- energy kaons w ith hydrogen. In January -F eb ruary d a ta were ob tained on the reactions K ~ p —*■ A7 and K ~ p —► E 7 a t rest. The detector was a superb new N al crystal m anufactured by BICRON. It consists of a central core 26.7 cm in diam eter, 56 cm deep, sur­rounded by a four-piece annulus which takes the di­am eter to 49.5 cm. This detector was tested a t the M IT -B ates Linac and found to have a resolution of1.8% a t 330 MeV (which is a factor of 3 b e tte r than TIN A ). T he technological trick is to ensure th a t the central core has an extrem ely uniform response to a 6 MeV 7 -ray source (±0.2% over the front 35 cm).W ith this crystal it was relatively easy to separate the captive 7 -rays to bo th the A and E°. Previ­ous experim ents had not clearly observed these 7 -rays bu t had a ttem p ted to ex trac t the A7 peak from the background w ith debatab le success. T he results are ju s t com patible w ith the calculations of W orkm an and Fearing described in the Theory section.In a second phase of the experim ent the LAM PF crystal box has been moved to Brookhaven and is now installed in the beam line. T his device consists of 396 individual crystals (w ith 432 photo tubes) and can determ ine the position and energy of medium -energy photons. T his detector was needed in order to study the weak radiative decay A —► n j which is of great in­terest in understanding the weak in teraction properties of the strange quark.In O ctober the A PC of Brookhaven approved a fur­ther 1000 h for th is experim ent and a run is planned for M arch-A pril 1988. T R IU M F has contributed mainly to the detectors, including the p lastic scintillators. A UBC studen t (A .J. Noble) is s ta tioned perm anently at Brookhaven and will be using the A —+ 717 d a ta as his thesis project.T h e S L D e x p e r im e n t(A. Astbury, TRIUMF/Victoria)Im pressive progress have been m ade during 1987 in the commissioning of the S tanford linear collider(SLC). No fundam ental problem has been uncovered which would prevent SLC from ultim ately achieving the design lum inosity of 6 x 1030 cm -2 s- 1 .In M arch bunches of electrons and positrons m et a t the in teraction point, and the m achine was declared completed a t a cost of $115.4 M US. A beam size of 5 p m diam eter was m easured a t the o u tp u t of the north arc (e_ ) in July. Subsequently the south arc was tuned, and in Septem ber e+e~ collisions were observed with ~20 p m d iam eter bunches. T he M ARK II detector was installed in O ctober, and it is anticipated th a t da ta collection will commence in April 1988 a t the rate of ~ Z Q s/day.T he m agnet steel and coil of the SLD detector have been erected close to the in teraction point of SLC. The dewar for the barrel liquid argon calorim eter (LAC) was delivered to SLAC in Septem ber and is currently prepared for m odule insta lla tion to commence during January 1988.The T R IU M F /U B C /V ic to ria group had built 60 out of its quo ta of 75 electrom agnetic m odules for the bar­rel LAC by the end of the year. The production in the meson hall extension should be finished during Febru­ary 1988.The modules are tested by subjecting them to high voltage in air, and m easuring the current drawn. The banded m odule m ust sustain 3000 V and have a to ta l current drain of <1 p A in dry air. T he p ro to type mod­ule produced in liquid argon a clean signal for cosmic- ray muons, well separated from the electronic noise, w ith the collected charge close to the predicted value (Fig. 12).EM co sm ic sp e c tru m (E2) 4 .0 kVqVt channelFig. 12. Histogram of charge collected from a single channel of the prototype module.15During production high standards of cleanliness and quality control have been essential to ensure uniform ity in the final p roduct. T he instrum enta tion developed in the group has been invaluable in achieving these goals. Fully au tom ated system s interfaced to PC s have been bu ilt for m easuring tile sizes, tower capacities, and m onitoring the current drains of individual towers.T he T R IU M F /U V ic engineers have assum ed full re­sponsibility for the design of the “cryogenic earthquake snubbers” which pro tect the SLD LAC in the event of a m odest quake. A p ro to type is under construction and will be tested early in 1988.T he group has assum ed responsibility for the design and building of a device capable of m onitoring the pu­rity of the liquid argon of the LAC during the operation of the SLD detector.T he T R IU M F /U B C /U V ic group continues to play a very active role in the developm ent of software for the experim ent. In particu lar, the co-ordination of all the calorim etry software and the M onte Carlo simu­lation of hadron showers are the responsibility of the C anadian group.T he group have taken responsibility for developing the system th a t will test the electronics resident on the dewar prior to installation . T his electronics digitizes the charge on each tower and produces a m ultiplexed signal of 160 towers on a single optical fibre. This arrangem ent significantly reduces the cost of cables for the 41,000 channels o f the calorim eter.16N U C L E A R P H Y S IC S A N D C H E M ISTR YE x p e r im e n t 266I n i t ia l s tu d ie s o f th e (n ,p ) r e a c t io n o n l ig h t n u c le i(K.P. Jackson, TRIUMF)T he prim ary purpose of E xpt. 266 was to provide precise calculation of the (n,p ) reaction as a probe of B q T , the d istribu tion of Gamow-Teller s treng th for isospin-raising transitions. T he accurately known f t values for the /3~ decay of 6He, 12B and 13B to the ground s ta tes of the daughter nuclei provide ideal op­portun ities for th is calibration. Analysis of m easure­m ents of the (n,p) reaction a t 0° on 6Li, 12C and 13C a t E n — 198 MeV has been com pleted and the results accepted for publication in Physics Letters B.E x p e r im e n ts 268 , 434Iso v e c to r g ia n t re so n a n c e s in 208P b (n ,p ) a n d 120S n (n ,p ) (M. Moinester, TRIUMF/Tel-Aviv;B. Spicer, Melbourne; S. Yen, TRIUMF)D uring M ay d a ta were taken for the 208P b (n ,p ) reaction a t 458 MeV and for the 120S n (n ,p ) reac­tion a t 298 MeV. Together w ith the previous d a ta3>01SuCO£XaX 0b 2 n AX100 20 40Excitation Energy (MeV)Fig. 13. The 458 MeV 208P b (n ,p ) d a ta at average scatter­ing angles of 2 .0°, 3.4°, 5.7° and 8.2°. The dashed lines are an estim ated background to the peaks.for E xpts. 268 and 376 [208P b (n ,p ) and 90Z r(n ,p ) at 198 MeV], these d a ta form a comprehensive d a ta set to study the energy- and A -dependence of isovector spin giant resonances in heavy nuclei. Figure 13 illus­tra te s the 458 MeV d a ta for Pb. T he absence of any prom inent forw ard-peaking s tructu res indicates th a t the G T is largely Pauli blocked. T he sharp peak at 5 MeV excitation in 208T1 is identified as the T> spin dipole on the basis of its angular d istribu tion and cross section (see Fig. 14) and on the basis of RPA predic­tions for the excitation energy [Krm potic et al., Nucl. Phys. A 342, 497 (1980); A uerbach et al., Phys. Rev. C 30, 1032 (1984)]. T he broad peak centred about 15 MeV is ten tatively associated w ith the T> spin isovector m onopole predicted to lie a t 13.5 MeV ex­citation [Auerbach et a l , op. cit; Klein, private com­m unication]. T he presen t large s ta tis tica l uncertainties for the 15 MeV peak do not allow a significant com par­ison of its angular d istribu tion shape w ith calculations. The off-line analysis of the 298 MeV 120S n (n ,p ) da ta is still in progress. T he spin dipole is strongly excited. The 120Sn(n, p) d a ta also exhibit a feature which might be the spin isovector m onopole b u t which is less prom i­nent th an in 208P b (n ,p ) because the spin dipole is less thoroughly Pauli blocked in 120Sn th an in 208Pb.198.4 MeV 458.4 MeV SGD R E = 0 - 6 .3 MeV0CM (degrees)Fig. 14. Angular distributions of the 5 MeV peak and back­ground under the peak for the 208P b (n ,p ) d a ta at both 198 and 458 MeV. The solid curve is a DWIA calculation, based on dipole wave functions containing simple linear superpo­sitions of all possible 1 hio lp - lh spin dipole configurations.170 30 60 90 120 150 180Deuteron c.m. angleFig. 15. Dependence upon centre-of-mass reaction angle of the change in €is , the sin^ com ponent of polarim eter azim uthal d istribution, normalized to change in Px , the sideways polarization of the beam.E x p e r im e n t 300P o la r iz a tio n t r a n s f e r in th e pp —* d r r e a c tio n(D. Hutcheon, TRIUMF)T he m edium resolution spectrom eter and its focal plane polarim eter (F P P ) were used to m easure the po­larization of deuterons from the reaction pp —► d r a t 507 MeV. T he quan tity of g reatest in terest in resolv­ing am biguities of p a rtia l wave am plitudes is K ss, the transfer o f vector polarization to the deuterons from a sideways-polarized pro ton beam .We have m easured azim uthal () distribu tions of scatterings in the F P P a t seven pp —► d r reaction an­gles. These were Fourier analysed to ex trac t el3, the coefficient of the sin te rm (norm alized to e0 = 1 ) f° r proton beam polarization in the + X and —X direc­tions. T he polarization dependence ( A e i s) / ( A P X) is p lo tted in Fig. 15. T his quan tity is proportional to the p roduct o f K ss and the vector analysing power of the F P P ; there is an additional contribu tion from one of the com ponents of tensor polarization, <21- In the coming year we will m easure the polarim eter analysing powers using the polarized deuteron beam of SaturneII. T his will allow q uan tita tive com parison of our d a ta w ith various p a rtia l wave am plitude fits or calculations.E x p e r im e n t 319R e la tiv is t ic m e d iu m e ffec ts a t in te rm e d ia te e n e rg ie s (D.K. McDaniels, Oregon)An im p o rtan t developm ent has seen the introduction of a relativ istic trea tm en t of proton-nucleus scatter­ing s ta rtin g from a D irac phenom enological approach.Im petus for th is theoretical approach was provided by the successful description of the analysing power A y and the spin ro ta tion function Q for the elastic scat­tering of 500 MeV protons by 40 Ca. T his approach was pu t on a firmer basis through the developm ent of a relativ istic impulse approxim ation (RIA). These ap­proaches suggest th a t the proton-nucleus optical po­tentials involve large a ttrac tiv e Lorentz scalar and re­pulsive vector contributions. I t is im portan t to extend these com parisons to inelastic sca ttering processes. In­elastic scattering to the continuum a t interm ediate en­ergies which is dom inated by quasielastic scattering provided a useful way to m ake the com parison with recent RIA calculations.RIA calculations involving strong scalar and vector fields have enjoyed a m easure of success in describing elastic p roton sca ttering a t 200 MeV and above. To extend the use of these calculations to inelastic sca tte r­ing Horowitz and Iqbal [Phys. Rev. C 33, 2059 (1986)] have recently calculated spin observables for quasielas­tic p roton scattering in the RIA. T he RIA approach for quasifree scattering is based on a covariant form of the am plitudes describing the N N in teraction while the scattering is described th rough the use of the Dirac equation. In the nuclear m edium the strong scalar and vector po ten tia ls enhance the lower two compo­nents of the 4-com ponent D irac wave functions. In the trea tm en t of Horowitz and Iqbal th is enhancem ent is param etrized by an effective m ass M* which can be calculated in an eikonal model. Q uasielastic scattering to the continuum is an a ttrac tiv e problem to study be­cause it minimizes the nuclear s tru c tu re dependence of final states. By focusing on the spin observables a t the m axim um of the quasielastic peak, m ultiple scattering and distortion effects are fu rther minimized.We have m easured differential cross section and analysing power d a ta for the inelastic scattering of 290 MeV protons by a 208P b target using the polarized beam and MRS facility a t T R IU M F. A broad range of excitation energy (0-160 MeV) has been studied over the 4°-26° angular range. A t the largest angles up to three different m agnetic field settings for the MRS were needed to cover an excitation energy range which included the quasielastic peak. T he incident protons were scattered from a 51 m g /cm 2 208Pb target. Beam intensity (1-5 nA) was m easured w ith a Faraday cup. T he beam polarization was m onitored by a polarim eter in the beam line.The RIA trea tm en t is expected to do a good job of describing various spin m easurem ents a t the quasifree peak since the reaction m echanism will be a single-step process. Analysing powers m easured in the present ex­perim ent are shown in Fig. 16. T he A y (9) value a t each angle was obtained by averaging the spectrum over a18# L(deg)Fig. 16. Analysing powers for the quasifree peak obtained w ith 290 MeV protons scattering from 208 Pb. The two dashed curves correspond to relativistic impulse approxi­m ation predictions for effective mass values of M* — M and M* = 0.83 M . The open squares show the free surface response predictions.5 MeV interval of excitation energy centred a t the loca­tion of the quasifree peak. The location of the quasifree peak was calculated using relativistic kinem atics plus an energy shift. T he RIA predictions for M* = M (M = nucleon mass) and 0.83 M are shown on the figure. T he au thors of the RIA trea tm en t obtained a value of M* = 0.83 M on theoretical grounds. In the RIA model the effective m ass M* is proportional to the average scalar field stren g th S , v ia M * — M + S. These d a ta support an effective m ass M* = 0.77 M if the trend of the calculation continues.E x p e r im e n t 327S tu d y o f th e (7r+ , 7r+ 7r_ ) r e a c t io n o n le O , 28Si a n d 40C a a t T*- = 2 4 0 a n d 280 M eV(N. Grion, INFN Trieste)T h e m easu rem en t o f th e (jr"*", ) reac tio n on le Oa t 280 MeV was com pleted during the Ju ly -A ugust in­tense beam period. A dditional m easurem ents to com­plem ent the d a ta from the 1986 runs were taken in or­der to m ore com pletely cover the allowed phase space. Results from the 1986 run have been published [Grion et al., Phys. Rev. L ett. 59, 1080 (1987)].T he T R IU M F QQD spectrom eter was used to detect the outgoing ir~ in the energy range of 35-110 MeV at lab angles of 50°, 80° and 115°. The CARUZ was used to detect the 7r+ in coincidence w ith the QQD and de­tected pions covering lab angles from 22.5-127.5° on the opposite side of the beam from the QQD. The CARUZ is a large solid angle device (0.20 sr) con-Fig. 17. The measured trip le differential cross section shown as a function of the ir~ energy for a CARUZ central angle of 50° and a QQD angle of 80° compared to theoret­ical predictions of Oset and Vicente-Vacas.structed prim arily from a stack of five scintillators. It measures the energy of the pion by stopping it in the scintillator m ateria l and m easuring the to ta l light out­put. T he pion tim e of flight is also m easured and in com bination w ith the energy inform ation and d E /d x from the first scin tillator in the stack enables the easy m ass-separation of pions from electrons and protons. The CARUZ m easures pions w ith energies in the range of 8-60 MeV w ith a resolution of b e tte r th an 2 MeV. A paper describing the characteristics of the CARUZ in more detail has been accepted for publication in Nucl. Instrum . M ethods.Analysis of the 1987 d a ta has no t yet been fully com­pleted bu t results are consistent w ith those from the analysed 1986 d a ta . T he theoretical model of Oset and Vicente-Vacas [Nucl. Phys. A 454, 637 (1986)] provides the m ost com plete description of the experim ental ob­servables available in the lite ra tu re and describes many of the observed features in the data . A full-length pa­per in collaboration w ith Oset and Vicente-Vacas de­scribing the full set of experim ental m easurem ents is being w ritten.The m easured fourfold differential cross sections d4T al dTw+ dCln+ dTw-dClw- were in tegrated over the energies and angles of the 7T+ 7r- pairs extrapolating to unm easured p arts of the phase space. The mea­sured to ta l cross section for the reaction is found to be 2.95 ± 0 .45 //b in good agreem ent w ith the full the­oretical model m entioned above. Partia lly integrated cross sections can also be com pared to the model. Fig­ure 17 shows the trip le differential cross section in­tegrated over 7r+ angles in the CARUZ com pared to predictions of the model. T he dashed curve represents the prediction when the renorm alization of the ou t­going real pions (or equivalently, the binding of theseC o in c id e n c e (7t+,7t )_. i i i ie =+ 80 ’± 3'e w+=- 50 ±28’2 0 0 -T (MeV)7T —19oaMteNx>+kHTJikH-O+kcT3lkcb•oFig. 18. The measured energy distribution of the x + in the CARUZ for the CARUZ a t 50° and the QQD at 50° accepting in the energy range of 60-110 MeV compared to the model predictions.the binding of these pions in the nuclear m edium ) has no t been included while the full line includes the bind­ing effect. T he inclusion of the binding constitutes the full model which describes the to ta l cross section. Note th a t all quantities are given in the laboratory frame.T he energy spectrum of detected 7r+ particles for one subset o f the d a ta is shown in Fig. 18. The curves have the sam e m eaning as in Fig. 17. The full cal­culation fails to reproduce to m easured energy d istri­bu tion which is peaked a t much lower energies than the model results T he failure is not serious and likely sim ply points to the lack of including a full trea tm en t of the inelastic reactions th a t the exiting pions can un­dergo. T he m odel includes absorption in the final sta te b u t no t inelastic scattering.E x p e r im e n t 329T h e E E L L e ffec t in 4 H e(Y.M. Shin, Saskatchewan)Inspired by the success of the EELL (Ericson- Ericson-Lorentz-Lorenz) effect in describing inelastic pion scattering for 0+ s ta tes in 12C [e.g. Lee et a i , Phys. L ett. 174B , 147 (1986)], we have undertaken a sim ilar investigation of the 20.1 MeV 0+ s ta te in 4IIe. Differential cross sections for 50 MeV pions incident upon a 1.7 cm thick liquid 4He ta rg e t were m easured using the T R IU M F QQD spectrom eter a t lab angles of 30°, 45°, 60°, 117.5° and 120°. No peaks correspondingto the 20.1 MeV s ta te were observed, thus placing an upper lim it of 3 pb /sv for each of the above angles. The upper lim its were due to backgrounds from m ultiply scattered elastic and deep inelastic pions from target walls and fram es th a t rem ained even after tigh t cuts on target position and thickness, tim e of flight of pions to ta rget, tim e of flight of pions through the QQD, various optical functions [0o- f ( 6 f ), Xq90, y ^ o ] andm om entum differences from W C4 and W C5. Em pty target runs showed th a t the rem aining backgrounds rem ained flat in the vicinity where the 20.1 MeV sta te should be. Only theoretical calculations w ith appre­ciable EELL param eters, such as elastic scattering pa­ram eter, transition am plitude param eter of (1.5,1.5) or (2 .0,2 .0), are consistent w ith the above experim ent lim its, as shown in Fig. 19.E x p e r im e n t 331S p in t r a n s f e r m e a s u re m e n ts in it + d —> p + p(G. Jones, UBC)An intensive program of spin-dependent m easure­m ents of the p + p —*■ d + x reaction has been directed in recent years to the experim ental determ ination of a unique set of am plitudes for th is reaction. M ost of this work has involved the m easurem ent of spin-correlation param eters ob tained by bom barding a polarized pro­ton target w ith a polarized p ro ton beam . It has been clear, however, th a t additional m easurem ents depend­ing on the deuteron spin are required before a unique am plitude determ ination can be obtained. T he first of these were i tn analysing power m easurem ents, carried ou t (for the inverse reaction) by utilizing a polarized deuteron target. T he m ost com prehensive set was pro­vided by the K arlsruhe group a t SIN. T he o ther m ea­surem ents required are the spin transfer param eters.Cw<6Fig. 19. Theoretical calculations for 28.1 MeV sta te in 4He using charge density and charge transition density.Coincidence (7t+,7t“)- + 50 ’± 3*e_ . « —5 0 ’±28 'T (MeV)20KINEMATIC CORRELATIONS Corbon angle (unfiltered)2 0 0 t - -i--------- rANGULAR CORRELATION COPLANARITYFig. 20. Polar and azimuthal (coplanarity) angular corre­lations for the rrd —► 2p reaction using 205 MeV pions.A lthough these have been known to be extrem ely im­p o rtan t in constraining the allowable partial-w ave am ­plitude fits, they have experim entally been the m ost challenging to perform .O ur approach to m easuring the spin transfer param ­eters has also utilized the inverse reaction, nam ely the determ ination of the polarization of one of the ou t­going protons when the pion is absorbed on a polar­ized deuteron ta rge t. To th is end, a p roton polarim e­ter has been constructed , a polarim eter sim ilar in de­sign to those developed a t SIN and LA M PF, involving use of a carbon analyser w ith m ulti-w ire drift cham­bers before and after the carbon to provide the nec­essary tra jec to ry inform ation. T he production of pro­ton pairs from background reactions associated w ith pion absorption in the nuclear ta rg e t m ateria l was distinguished from the reaction of in terest by impos­ing appropria te kinem atic constrain ts on the two pro­ton events. Figure 20 shows the po lar and azim uthal (coplanarity) angular correlations resulting when the deu terated target was employed, while the lower curves in each case indicate the corresponding quality ob­tained using a norm al hydrogenated target instead. It is clear th a t the jo in t im position of cuts on these two d istribu tions reduces the background contam ination to the level of a few per cent. In order to reduce the am ount of d a ta stored on m agnetic tape, a front-end processor (SEN J - l l S ta rb u rst) was employed to re­jec t any events associated w ith a scattering angle in the carbon of the polarim eter by less th an 6°. Fig­ure 21 dem onstrates the effectiveness of this system for elim inating the large num ber of “stra igh t-th rough” events which would otherwise have sa tu ra ted the d a ta acquisition system . B oth Figs. 20 and 21 were ob­tained for incident pions of 205 MeV kinetic energy. The d a ta analysis algorithm s have been tested on a set of unpolarized ta rg e t runs. One im portan t checkO 'co120 4 0 -4 0 -120 --200-20 -12 -4 4 12X angle20Carbon angle (filtered) 200 c---------rFig. 21. Two-dimensional plots of proton scattering an­gle in the 7 cm thick carbon analyser of the polarimeter. The “unfiltered” events are a sample of those events satisfy­ing cuts based only on reaction kinematics. The “filtered” events are the result when a > 6 ° scattering angle is imposed by the J ll-S ta rb u rs t.°6.0 8.8 11.6 14.4 17.2 20.0T H E T AFig. 22. Proton polarization resulting when an unpolarized deuteron target is employed. The polarization is plotted against the scattering angle in the carbon analyser. The solid lines are the angle-independent least squares fits to the data.21for system atic errors is the requirem ent th a t the cal­culated polarization is independent of the scattering angle of the proton in the carbon of the polarim eter. Figure 22 shows such a result for the unpolarized ta r­get. For th is reaction a nonzero “norm al” polarization is expected (equal to the analysing power of the inverse pion p roduction reaction). However, no “sideways” po­larization can result from such a reaction. Some side­ways polarization will, however, develop as the proton precesses while travelling through the m agnetic field surrounding the polarized target. Development of the d a ta analysis algorithm s to account for th is precession is currently under way. M easurem ents relating to the spin transfer param eters Ki„ and K , s were m ade w ith the target polarized (vector polarized to greater than 30%) a t pion energies of 105 (K t , only), 140, 180, 205 and 255 MeV. Because of constrain ts imposed on the emerging protons by the m echanical struc tu re of the polarized ta rge t, the K t a m easurem ents (which em­ployed a longitudinally polarized ta rge t) were taken w ith the polarim eter s itua ted a t an angle correspond­ing to 30° (c.m .s.), whereas the corresponding angle for the K , s m easurem ents (using the target in a sideways orientation) was 90°.E x p e r im e n t 337E n e rg y d e p e n d e n c e o f T20 a n d 7-21 in vd e la s tic s c a t t e r in g (G.R. Smith, TRIUMF)D ata acquisition and analysis for E xpt. 337 has been com pleted during the course of the year. A draft of the final publication has been prepared and is being circu­lated to the collaboration. T his final publication ad­dresses the energy dependence of the tensor analysing powers T20 and 7-21 for 7rd elastic scattering. M ea­surem ents of T20 were ob tained for pion bom barding energies of 180, 220 and 256 MeV. M easurem ents of 7*21 were obtained for pion bom barding energies of 134 and 220 MeV. Six-point angular d istribu tions were ob­ta ined for the T20 m easurem ents, and twelve-point an­gular d istribu tions were acquired for the m easurem ents of 7*21- T he results are com pared w ith th ree-body cal­culations where effects relating to pion absorption are seen to play an im portan t role.O ur previous work in th is area includes m easure­m ents of T20 a t 134 and 151 MeV [Phys. Rev. Lett. 57, 803 (1986)], m easurem ents of 7*21 a t 180 MeV [Phys. Rev. C 35, 2343 (1987)], and m easurem ents of pzz [Nucl. Instrum . M ethods A 254, 263 (1987)]. To­gether w ith the current results, these d a ta provide a system atic basis for com parison to theoretical predic­tions over the (3,3) resonance region.M easurem ent of a given spin observable Tkq is ac­com plished by choosing an appropriate orien tation ofthe deuteron spin alignm ent axis, such th a t the contri­bu tion of o ther spin observables is elim inated or m in­imized. M easurem ents of T20 are perform ed in an ex­perim ental configuration w ith longitudinal ta rget mag­netic field. This orientation results in a clean, simple expression for T20 which involves only the polarized and unpolarized nd elastic cross sections of excitation so th a t there is little mixing w ith o ther possible one-particle- one-hole configurations. For charge exchange nucleon scattering [(p, n), (n ,p)] a t m edium energies stretched sta tes are excited alm ost exclusively by the isovector- tensor p a rt of the nucleon-nucleon in teraction . Thus stretched sta tes have a very simple particle-hole struc­tu re and are excited in (p, n) or (n ,p ) reactions princi­pally by a single p a rt of the nucleon-nucleon force; for these reasons the ir excitations in (p, n) and (n ,p ) reac­tions provides an opportun ity to explore the nucleon- nucleus in teraction in a s itua tion relatively free from com plications.The specific transitions th a t we studied were 12C (n ,p )12B (4",4 .5 M eV)[^d5/ 2,7rp3/12] 28S i(n ,p )28A l(6~ ,5.17 M eV )[i//7/2, i r d j / j 120S n (n ,p )12OIn(10“ , ~ 0 .0 M eV)[i//iu / 2, 7rg~f\]T he 10“ streng th populated in the S n (n ,p ) reac­tion appears to be concentrated in a single sta te , pre­sum ably because the neutron excess places b o th the neutron-particle and proton-hole orb its near the nu­clear Fermi surface.E x p e r im e n t 352Z ero d e g re e r a d ia t iv e c a p tu r e o f n e u t ro n s(G .W .R . Edwards, Alberta)In Decem ber 1986 E xpt. 352 ( “ZERCO N ” ) moved to the MRS CHARGEX facility for its zero degree cross- section m easurem ent of the p ( n ,y ) d reaction. An LH2 ta rget cell, ad justable between 4 and 6 cm, was con­structed which allowed the placem ent of th in (0.01 in.) plastic scintillators directly on the walls surrounding the cold gas and the viewing of these scintillators (one upstream and one dow nstream of the ta rge t) through two periscope-like air guides. T h is arrangem ent was designed in order to provide a clean signal th a t an event producing a deuteron had occurred in the target cell, and to remove the substan tia l background from (n ,d ) reactions on carbon which had proven a problem when ZERCON was running on the 4A line. T he other m a­jo r problem associated w ith the earlier ZERCON runs, the lack of a resolution capable of clearly separating the p ( n ,7 )d reaction from the m uch more probable p(n,7r°)d reaction, was expected to be solved by the sm all energy spread (<1 MeV) of the neutron beam produced in the CH A RG EX facility (from 7Li(p, n )7Be on a 220 m g /cm 2 Li ta rge t) and by the use of the MRS, a spectrom eter w ith good resolution and well-known properties.In Decem ber 1986 runs a t energies 240 MeV and 300 MeV were attem pted . T he th in scintillators which were supposed to reduce the background under the (71, 7 ) peak perform ed poorly during th is run , and as a result the usefulness of the 300 MeV d a ta is some­w hat dubious. T he 240 MeV ( n ,7 ) peak while sitting on a large background, provides a point of overlap with the Mainz d a ta set, w ith s ta tis tica l errors in the neigh­bourhood of 6-7% (after background subtraction).In A ugust ZERCON resum ed running a t energies of 360 MeV, 410 MeV (in terrup ted by the A ugust prob­lems w ith the T R IU M F rf transform er and completed240 50 100 150 200MomentumFig. 25. The num ber of deuterons from the reactions np —► dy and np —* dw° at 410 MeV are shown as a function of focal plane position for a full target (upper panel). Below is shown the yield from an em pty-target run, normalized to the same beam flux.in O ctober) and 460 MeV. In the in terim the light- gathering efficiency of the LH2 interior scintillators had been considerably increased by an im proved periscope geom etry and by the sanding of the back of these scin­tillators. T he runs a t these energies were quite success­ful. T he na tu ra lly lower background a t the higher ener­gies, combined w ith the stringent condition imposed by the interior scintillators, reduced the background sub­traction problem to an easily m anageable size, and the resolution of the spectrom eter kept the (n, 7 ) peak well separated from the (d, ir°) peak. Enough counts were accum ulated a t each energy to provide 5% statistics after the double norm alization of p(n, 7 )d to p(n , 7 r ° ) d and p ( n ,7r°d to p (n ,p )n (required because the accep­tance of the MRS was not sufficient to include both the (n, 7 ) and elastic scattering peaks a t the energies above the pion production threshold). Figure 25 shows the results of the prelim inary analysis of the 410 MeV data .E x p e r im e n ts 3 5 5 /4 5 9E x c h a n g e e ffec ts in 0+ —► 0- in e la s tic s c a t te r in g (J. King and D. Frekers, Toronto)T he 0+ —► 0“ transitions are of special im portance in the study of the in teraction of interm ediate-energy pro­tons w ith nuclei. In nonrelativ istic im pulse approxim a­tion calculations one finds the analysing power A y — 0 under tim e reversal invariance if only the direct te rm is included. However, the exchange term does not vanishunder tim e reversal, and therefore a finite A y measures the exchange p a rt o f the in teraction.Also, in a longitudinal-transverse representation for the in teraction t m atrix , we find the transverse term s vanish for the 0+ —► 0~ transition , which m eans th a t the spin-orbit p a rt of the in teraction does not con­tribu te . A nd since the central te rm is expected to be weak, the cross section should be determ ined m ainly by the m agnitude of the tensor p a rt of the interaction.We have m easured d a /d f l and A y a t E p = 200 MeV for the T = 0 0+ —► 0“ transition in 160 using both solid oxide targets and a “waterfall ta rg e t” . For the description of our d a ta a microscopic optical potential, which gives good fit to the elastic scattering d a ta , has been used in DW IA calculations w ith bo th the Ham­burg density-dependent (DD) poten tia l and the 1985 Love-Franey (LF) effective in teraction . T he results are shown in Figs. 26 and 27. A lthough the tensor compo­nent of the interaction dom inates in bo th cases, neither calculation gives a satisfactory description of the data.A relativ istic trea tm en t is quite different to nonrela­tivistic calculations in the sense the nonvanishing val­ues for the analysing power of the 0+ —» 0“ transition cannot be related anym ore to only the exchange parts of the in teraction . We have perform ed a relativistic calculation (D REX ) using the im pulse approxim ation w ith expicit exchange included. As can be seen from Fig. 28 the results underestim ate the cross section by roughly a factor of 2.5, although the shape of the cross section as well as of the analysing power is significantly b e tte r described.Refinements of the DD and D REX calculations are in progress and a m easurem ent a t Ep = 400 MeV is presently under analysis. A much b e tte r understand­ing of the tensor com ponent of the nucleon-nucleon in teraction is in sight.E x p e r im e n t 365 A s e a rc h fo r th e t e t r a n e u t r o n(T. Gorringe, UBC and Queen Mary College)We have used the pion double charge exchange (DCX) reaction 4H e(7r_ , 7r+ )4n to search for the pro­duction of te tran eu tro n s (nuclei containing four neu­trons and no protons). We searched for An bound by 0 to 3 MeV (the upper bound being set by the ab­sence of the decay sHe—>4H e+ 4n), using the TRIU M F tim e projection cham ber and a high pressure helium gas target. T he experim ent was perform ed on the M9 channel a t tt~ incident energy of 80 MeV, over an an­gular range from 50° to 130°. The acceptance and m om entum resolution for 50 MeV 7r+ were determ ined studying the elastic sca ttering Tr^He [see Fig. 29(a)], Careful investigation of the ra te dependence of these2510° 10°" 0 8 16 24 32 400c.m. (deg)8 16 24 32 400c. m. (deg)Fig. 27. Same as Fig. 26, but for DD interaction.Fig. 26. Cross section and analysing power for the 0+ —♦ 0~ ,T = 0 transition in leO with the 1985 LF interaction. The dashed (dotted) curve is the tensor (central) contri­bution and the solid curve is the sum of centra and tensor contribution.Fig. 28. Cross section and analysing power from a relativistic calculation. For the dashed curve the results have simply been scaled by 2 .5 .0c.m. (deg)2640 60 80 100 120 140 160 180 7T momentum (M eV/c).40 60 80 100 120 140 160 180 7T+ momentum (M eV/c).Fig. 29. (a) Measured 7r+ m om entum spectrum from4H e (r_ , 7r+ ) at 170 M eV /c (80 MeV) and 6 = 50°-130°, after all cuts and flask background subtraction. Arrows in­dicate the region corresponding to bound te traneutron pro­duction w ith the experim ental resolution, (b) Measured 7r+ momentum spectrum from 4He(7r+ , 7r_ )4He elastic scatter­ing at 128 M eV/c (50 MeV). The mom entum resolution is 11 M eV/c (99% . Two targets were available, w ith areal densities of 224 m g /cm 2 and 405 m g /cm 2. Explicit m easurem ents of the sm all back­ground from quasifree nd elastic scattering on carbon were m ade using graphite slab targets.The relative differential cross sections were calcu­lated from m easurem ents of the nd elastic scattering yield, the num ber of incident beam particles (counted d irectly), the com puter efficiency (typically 99%), the correction for m ultiple particles in the beam burst, and the pion fraction of the incident beam f n . T he s ta ­tistical uncerta in ty associated w ith the relative cross sections was < 1% for each sequence.T he pion fraction of the incident beam /* (see Ta­ble II) is the largest correction to the d a ta which is sensitive to the incident beam polarity. Considerable a tten tion was given to an accurate determ ination of this correction. D uring each run, the e± contam ina­tion of the incident beam was acquired sim ultaneously w ith the 7r± d d a ta , by digitizing a tim ing signal from a capacitive probe in the T R IU M F proton beam line w ith respect to a scin tillator in the M i l beam. A separate m easurem ent of the incident beam fraction was m ade after the experim ent, by lim iting the phase space of the incident beam using slits in the TR IU M F cyclotron, such th a t the w idth of the incident beam buckets was ~ 0.6 ns, instead of the usual 2.5 ns. This m ade it possible to separate 7r± , /r± , and a t each of the bom barding energies studied in th is experim ent. A typical spectrum (obtained using the narrow beam bucket) showing the separation of ^ ± , /i± , and e± at T ,r=180 MeV is presented in Fig. 31. Table II sum m a­rizes the results of the beam fraction studies w ith the narrow beam bucket m easurem ents.A T ( n s e c )Fig. 31. The T O F spectrum of particles down the M il channel is shown for positive (1) and negative (b) polarities at T,r=180 MeV. From left to right the peaks correspond to pions, muons and electrons or positrons. The separation between the pion and electron peaks is 5.7 ns.A t T w= 143 MeV the results from two sequences of A (T W,9) m easurem ents from the present experim ent agree nicely w ith each other. T he d a ta reflect a flat angular d istribu tion of A(143, 9) w ith values ~ -1.5% . The results from th is experim ent are, however, incon­sistent w ith those from an earlier study a t LAM PF, which consist of values around + 1 to + 2% in this an­gular region [M asterson et al., Phys. Rev. L ett. 47, 220 (1981), Phys. Rev. C 26, 2091 (1982), Phys. Rev. C 30, 2010 (1984)]. The difference is more th an can be accounted for by the experim ental uncertainties.The results of the LA M PF experim ent are, however, dependent on the detailed n ^ p cross sections th a t were used to normalize their ic*d da ta . T heir original valuesTable II. The constituents of the incident pion beam are tabu lated at each of the energies studied in this experi­ment. The num bers refer to the ratio of particles of a given type to the to ta l num ber of particles of all types. The m easurem ents were obtained using rf-referenced TO F and a 0.6 ns wide proton beam bucket as discussed in the text.Tn(MeV)Polarity fn U h143 7T* 0.977 0.018 0.0057r“ 0.887 0.011 0.102180 7r+ 0.986 0.012 0.0027r“ 0.942 0.008 0.050220 7T+ 0.990 0.007 0.0027T_ 0.970 0.006 0.025256 7T+ 0.995 0.005 0.0017T_ 0.985 0.005 0.00929of A(Ttt , 9) a t bo th 143 and 256 MeV were based on the d a ta of Bussey et al. [(Nucl. Phys. B 58, 363 (1973)], used in conjunction w ith the com puter code SCA TPI. Since publication of the LA M PF CSB pa­pers, there have been several recent 7r± p cross section m easurem ents published, including one from this group [Brack et al., Phys. Rev. C 34, 1771 (1986)] which em­ployed techniques sim ilar to those used in the present experim ent. These new ir^p m easurem ents were un­dertaken to resolve discrepancies observed in the ex­isting 7r±p d a ta base. R. A rnd t generated a new set of irN phase shifts (SP87) based on these d a ta as well as m any of the o ther d a ta sets. The 7r± p cross sec­tions calculated from the SP87 phase shifts were used to renorm alize the LA M PF data . T heir 143 MeV d a ta changed considerably, yielding values of A(143,0) th a t were predom inantly negative and in substan tia l agree­m ent w ith the d a ta of the present study. We stress th a t the present experim ent is an absolute m easure­m ent of A (T W,9 ) requiring no norm alization to ir^p da ta . There rem ains some sem blance of a controver­sial bum p in the renorm alized LA M PF d a ta a t about 110 ° bu t it is not sta tistica lly significant and there is no evidence for such a bum p in the present da ta . T he agreem ent between the A(143, 9) m easurem ents of th is experim ent and those of the LA M PF experi­m ent when norm alized to the recent 7r± p d a ta from T R IU M F shows in ternal consistency between all three of these m easurem ents.T he electrom agnetic p e rtu rba tions which break charge sym m etry are simple in principle, yet there are no m ethods to include them exactly in calculations of the sca ttering of a particle on a com posite system. M ost m ethods make use of the global param eters C m and C r in Eq. (2) as a m easure for CSB. Non-zero val­ues of C m or C r indicate CSB. Here, we take the (+ + ) and (+ ) param eters to be best known. T hen first keep­ing Mo and To fixed, we scan C m and C r regions by varying M _ and T _ . We also consider an alternative To value to see its influence. The specific combina­tions of param eters we have investigated are tabu la ted in Table III.Obviously, the range of inpu t param eters can only be lim ited if the d a ta fall w ithin the spread of the pre­dicted A (T W,9) , and if the spread is large com pared to the experim ental uncertainties. These conditions are m et only for Tn= 143 MeV. T he results for A(143,6) are displayed in Fig. 32. T he present calculations w ith C r= 3 .5 or 2.5 MeV all predict positive values of A(143, 9) regardless of the value of Cm - Only the pre­dictions for C r= l-2 MeV produce the negative A(143, 9 > 60°) values observed experim entally. The shape of the predictions is such th a t it is difficult to describe sim ultaneously the older, forward angle LA M PF d a ta0 20 40 60 80 100 120 140 160 1800 c.m. ( d e g )Fig. 32. The T,r=143 MeV d ata from the present exper­im ent (solid symbols) are shown, as well as the renorm al­ized older LAM PF d ata (open symbols). The present cal­culations are shown for C r= 3 .5 MeV (solid curves) and C r= 2 .5 MeV (dashed curves). For a given choice of Cr successively more positive A{Tn ,0) values are predicted as C m assumes the values 4.5, 3.5 and 2.5 MeV. The dash- dotted curves correspond to solutions 7 (upper curve) and 8 (lower curve) from Table III.and the predom inantly backw ard angle d a ta of the present experim ent. Given the problem s discussed above concerning the ir^p renorm alizations and rad ia­tive corrections to the older d a ta , we prefer param ­eter set eight from Table III, which appears to pro­vide the best description of the d a ta from the present experim ent a t th is bom barding energy, even though the (renorm alized) LA M PF d a ta are slightly under­predicted.Table III. The resonance param eters used for the calcula­tions shown in Fig. 32 are shown. All numbers are in MeV. Fixed values are M+ + = 1231.1, M+ = 1230.5, Mo=1232.5, r ++ = 111.5 and r+ = 113 .5 MeV.______________________Solution C m Cr M - To F_1 4.5 3.5 1234.9 115.7 113.32 3.5 3.5 1233.9 115.7 113.33 2.5 3.5 1232.9 115.7 113.34 4.5 2.5 1234.9 112 .6 114.35 3.5 2.5 1233.9 112 .6 114.36 2.5 2.5 1232.9 112 .6 114.37 4.5 1.2 1234.9 112 .6 113.08 4.5 1.2 1234.9 115.7 112 .030E x p e r im e n t 378S tu d y o f 48T i(n ,p ) as a te s t o f life tim e c a lc u la t io n s fo r th e d o u b le b e t a d e c a y o f 48C a(R. Helmer, W.P. Alford, Western Ontario)T his experim ent is a test of a specific calculation [Brown, in Nuclear Shell Models (W orld Scientific, Sin­gapore, 1985), p .42] of neutrino mass. T he calculation was based on the m easured lifetim e lim its for the dou­ble b e ta decay of 48Ca, and as a byproduct it predicts the d istribu tion of Gamow-Teller s treng th in the in ter­m ediate nucleus, 48Sc. Utilizing the well-known cor­respondence between Gamow-Teller streng th and the cross section for charge exchange reactions at low mo­m entum transfer [Goodman et al., Phys. Rev. Lett. 44, 1755 (1980)], we have m easured th is d istribution w ith the 48T (n , p )48Sc reaction using the TR IU M F charge exchange facility [Helmer, Can. J . Phys. 65, 588 (1987)]. T he first four ta rgets in the target box [Hen­derson et al., Nucl. Instrum . M ethods A 257, 97 (1987)] were T i02 powder contained between m ylar foils, and the fifth was a T i m etal foil. A CH 2 ta rget in the fi­nal position provided the cross-section norm alization through the known H (n ,p ) cross section [Arndt and Soper, S cattering analysis interactive dial-in (SAID) program , phase shift solution SM 86 , V irginia Polytech­nic Inst. & S ta te Univ., unpublished]. The experim ent was carried out a t 200 MeV, and d a ta were taken at three angles, 0°, 6° and 12°.Figure 33 shows the results of a prelim inary anal­ysis of the d a ta from the T i foil. The spectrum wasE> in ‘‘S c (MeV)Fig. 33. The 48T i(n ,p )48Sc spectrum at 0°. The dashed lines represent Gamow-Teller strength extracted from this experiment; the solid lines are from the calculation of Brown.fitted w ith a series of peaks whose shape reflected the known response of the detection system . T he dashed lines represent the Gamow-Teller s tren g th ex tracted at the given excitation energies. Based on the m easured angular d istribu tion , the streng th a t higher excitation is m ostly dipole and higher m ultipo larity transitions. T he solid lines are the predicted d istribu tion [Brown, op. cit.] of Gamow-Teller streng th based only on one partic le-one hole excitations. I t is clear th a t the calcu­lation fails com pletely to describe the data . Including m ore com plicated configurations spreads the strength som ewhat from the single dom inant s ta te shown here, b u t there is still poor agreem ent w ith experim ent.The spectra from the powder targets have recently been ex tracted , and the sum of all the spectra have been fitted as above. The fitted transitions are shifted in m inor ways in s treng th and position from those shown in the figure. A DW IA calculation which will allow us to estim ate how much nonGamow-Teller s trength is present in each transition is in progress.F inal results should be available soon, bu t the m ajor conclusion is th a t th is particu lar calculation [Brown op. cit] of the neutrino m ass is very likely in error.E x p e r im e n t 379E n e rg y d e p e n d e n c e o f th e (p, n) c ro ss se c tio n fo r 13 C a n d 15N (W .P . Alford, Western Ontario)We have studied these reactions in order to in­vestigate the anom alously large ratios of 0)UCOw c :bCMX)43 2 1 04321043 2 1 043 2 1 04 3 2 1 0• T " ' I I t-------------- 1—54Fe(n,p)54Mn 298 MeV. 0 deg.2.5 dec.H 1------- 1------- 1------- h5 deg.H------- 1------- 1------- 1------- h-8 deg.H 1------- 1------- 1------- 1—12 deg.» I-10 0 10 20 30 40 60Ex (MeV)Fig. 40. 54F e(n ,p )54Mn cross section for five angles between 0° and 1 2 °.were grouped in to 1 MeV bins and a m ultipole de­com position was done for each one. This consisted of a least squares fit using angular distributions gen­erated by the d istorted wave impulse approxim ation. Shapes for angular m om entum transfers of L = 0, 1 and 2 were used. T he results of th is decom position for 0° are shown in Fig. 41. Note th a t the peak a t low E x is indeed m ainly A L = 0 , characteristic of the G T res­onance. T he in tegrated cross section up to 10 MeV of excitation is 16.9 ± 1.1 m b /sr . T he G T component of this is 12.9 ± 1.2 m b /sr, including an error of ±5% on the A L = 0 fraction. T he value of a(0°)/B(GT), the ra tio of 0° cross section to /?-decay streng th was also calculated w ith the D W IA . A value of 3.4 was ob­tained. T his gives a resu lt of B(GT+) = 3 .8 ± 0 .4 ± 0 .6 where 0.6 is the uncerta in ty from the calculation of370 5 10 15 20 25 30 35 40EX (MeV)Fig. 41. M ultipole decomposition for the S4F e(n ,p )54Mn reaction at 0°.cr /B (G T). Bloom and Fuller predict B ( G T + ) = 10.29 for a simple model which includes only transitions from the f 7/ 2 p roton shell to the f 5/ 2 neutron shell. If one particle-one hole excitations are included, they get B ( G T + ) = 9.12. T he m easured strength is there­fore only 0.41 tim es the predicted strength . M uto has done a sim ilar calculation and obtains the same results [Nucl. Phys. A 451, 481 (1986)]. However, he also ex­tends the m odel to include two particle-tw o hole exci­ta tions in the paren t nucleus. T his reduced the pre­dicted stren g th to B { G T + ) = 7.35, still a factor of two too large. A uerbach et al. have done RPA calcu­lations for 60Ni which have shown th a t the predicted streng th is reduced by a factor of two w ith respect to the simple shell model. T his would give an RPA value of B ( G T + ) = 5.15. These results are sum m arized in Table V.54Fe(p, n )54CoD ata were ob tained for six angles between 0° and 15°. These are shown in Fig. 42. Again, we note the forward peaked G T resonance below 13 MeV. Excita­tion of the isobaric analog sta te is greatly reduced at th is beam energy and makes only a sm all contribution to the peak a t £»2 MeV. T he sam e procedure was used here as for the (n ,p ) d a ta and the result of the m ulti­pole decom position is shown in Fig. 43. The A L = 0 cross section below 13 MeV is 3 3 .7 ± 2 .0 m b /sr. Using the value of cr /B (G T ) = 3.4, we get B ( G T ~ ) = 9.4 ± 0.6. T his is com pared to the simple shell model pre­diction of 16.29, im plying a quenching factor of 0.58.Table V. Summary of the predicted and measured B (G T + ) values for the 54Fe(n, p )54 Mn reaction.Experim ent Bloom and FullerMuto RPAsimplelp-lh2p-2h3.8±0.4±0.610.299.1210.299.367.355.15Ej (MeV)Fig. 42 . 54Fe(p, n )54Co cross section for six angles between 0° and 15°.3864Fe(p,n)MCo, 300 MeV\b i___ i___ i i i i i i0 5 10 15 20 25 30 35 40Ex (MeV)Fig. 43. M ultipole decomposition for the 54Fe(p, n )S4Co reaction at 0°.R apaport et al. [Nucl. Phys. A 410, 371 (1983)] have also m easured B ( G T ~ ) . They found B ( G T ~ ) = 7.8 ± 1.9 a t 160 MeV. We can combine these results w ith our (n ,p ) d a ta to test the G T sum rule: B ( G T ~ ) — B (G T + ) = 3 ( N - Z ) = 6 for 54Fe. We find 67% or 93% of the sum rule. These results are sum m arized in Table VI.Table VI. Comparison of the two (p , n) results and their effect on the sum rule.(n,p) (P, n) sum ruleVetterli 3.8±0.4±0.6 9.4T0.6 5.6±0.9R apaport 7.8A1.9 4.0±2.1Further work is needed on the calibration of cr /B (G T) a t 300 MeV in order to verify our result th a t the sum rule value has essentially been seen in 54Fe. This is the subject of E xpt. 490.E x p e r im e n t 384T h e (n,p) re a c tio n on 56Fe a n d 5SNi (K.P. Jackson, TRIUMF)T he d a ta for th is experim ent, a study of the dis­tribu tion of Gamow-Teller s trength 5 (G T + ) in 56Mn and 58Co, was ob tained in May. T he prim ary m oti­vation was the need for experim ental guidance in es­tim ating the ra tes for capture of energetic electronson nuclei in this m ass range during the gravitational collapse of a massive star. These weak interaction rates play a significant role in the hydrodynam ics of stellar collapse and the subsequent supernova explo­sion. P rior to the existence of the T R IU M F facility the m ost detailed estim ates of these ra tes were based on the shell model calculations of B ( G T +) by Bloom and Fuller [Nucl. Phys. A440, 511 (1985)]. Analysis of the 54F e(n ,p )54Mn d a ta revealed th a t in this case the relative d istribu tion of the predicted strength coincides well w ith the d a ta bu t th a t the m agnitude of the cross section is over-predicted by a factor of 2.4±0.5 [Vetterli et al., Phys. Rev. L ett. 59 , 439 (1987)]. Since one re­sult does not establish system atic behaviour and since the isotopic abundances of 56Fe and 58Ni are large, the present experim ent is regarded as an im portan t exten­sion of this investigation.The targets used were of natFe (91.7% 56Fe, 5.8% 54Fe) and enriched 58Ni (on loan from Los Alamos). A ngular d istribu tions were recorded a t 6p = 0o,3 ° ,6 ° ,1 0 o and 15° w ith neutrons incident a t E n = 198 MeV. A lthough the shapes of the spectra a t 0° re­semble bo th the predictions and th a t recorded for 54Fe, the d a ta analysed on line suggested th a t the Gamow- Teller resonance (G T R ) is m ost prom inent on 58Ni. The final analysis of these d a ta is in progress and re­sults are expected shortly.E x p e r im e n t 394E la s tic ir^p d if fe re n tia l c ro ss se c tio n s a t T„ = 30 to67 M e V (R.A. Ristinen, TRIUMF/Colorado; D.R. Gill, TRIUMF)During recent years an effort has been m ade a t the meson factories to resolve discrepancies in the pion- nucleon d a ta base. In particu lar, a group from Boul­der, Vancouver and Regina has m easured 7r± p elastic cross sections a t energies between 67 and 139 MeV and a t laboratory angles of 63° to 155° (E xpt. 322) [Brack et a l , Phys. Rev. C 14, 1771 (1986)]. A pro­posal to extend these m easurem ents to lower energies was first presented to the T R IU M F E xperim ents Eval­uation C om m ittee in Ju ly 1986. T he com m ittee rec­om m ended a prelim inary feasibility study of the exper­im ental m ethod, which was perform ed in Septem ber 1986 during the period of reduced beam intensity. A second presentation of the proposal a t the December 1986 EEC m eeting, including those prelim inary results, was approved, and the experim ent was perform ed in May and June of this year. The d a ta analysis is now under way, and all results reported here are of a strictly prelim inary nature.The experim ent was run a t incident pion energies of 30, 45 and 67 MeV, a t several scattering angles be-39Fig. 44. A rrangem ent of scintillation counters for simul­taneously measuring np elastic cross sections at six pion scattering angles. Event definition is S i -T ■ t 1 • 7t2 with software cuts on pulse am plitude in T and on (T — 7r2) T O F. M l and M2 are m onitor counters.tween 40° to 140°, using an active CH target. The beam spot on the ta rg e t was defined by an upstream scin tillator (S I) of dim ension 2 cm x 4 cm. Six pion counter telescopes detected scattered pions a t six an­gles in coincidence w ith recoil pro ton signals in the ta rg e t (Fig. 44).Several active targets of different thickness were used, each typically a few m illim etres thick. The ta r ­get angle relative to the beam was set so th a t the re­coil pro ton tra jectories were in the plane of the ta r ­get. T hus any one ta rg e t angle corresponds precisely to only one sca ttered pion angle. For nearby scattered pion angles a sm all fraction of the recoil protons is lost through either the front or back target surface. Since d a ta were gathered sim ultaneously a t six scat­tering angles, the ta rg e t angle was chosen to minimize the to ta l num ber of protons exiting the surface of the ta rge t. These surface losses have been calculated, bu t as an independent check sim ultaneous m easurem ents were m ade w ith two different targets, of thickness Ti and T-j, set a t the sam e angle in a sandwich configu­ration . The difference betw een the observed yields Vj and Y2 produces a differential cross section:w ith K a constant. T he recoil pro ton escape frequencyis the sam e from the surface of either ta rget and thus sub trac ts out, b u t a t some cost in s ta tis tica l precision. As a final check on our ability to resolve the surface effects, the angle of the sandw ich ta rg e t was varied while keeping the rem ainder of the set-up untouched. T he effect of transverse straggling of protons through the surface of the ta rg e t is sm all and will be evaluated by M onte Carlo m ethods.M onte C arlo techniques will also be used to evaluate the influence on m easured cross sections of pion decay and m ultiple scattering of b o th pions and protons in the target and the o ther elem ents of the experim en­ta l set-up. For positive pions a t the larger scattering angles, where the sca ttering cross sections are large, d a ta were collected using several ta rg e t thicknesses, so th a t com parison w ith M onte C arlo calculations will en­sure th a t these calculations are correctly describing the m ultiple scattering and pion decay effects.Yields are extracted from ta rg e t ADC vs. pion de­tector T O F dotp lo ts (Fig. 45), subject to a pion de­tector T O F vs. ADC cut and to a cut on the par­ticle T O F between the production ta rg e t and SI, which elim inates muon- and electron-induced events. These cuts are im p o rtan t for the dow nstream ta r­get because these spectra contain quasifree absorp­tion events b o th from the upstream target and the graphite proton absorber between the targets, since both targets operate in transm ission mode. The to­ta l experim ental uncertain ties are typically as small as ±5% due to the highly accurate determ ination of the num ber of scattering centres in the solid66.8 fieV dual ta r g e ts RI24 f i n BFig. 45. Dot plot of the target (T2) ADC vs. 7t2 TDC used to extract np elastic scattering yields. The scatter­ing angle is 60°. The box surrounds the rrp elastic events. The diagonal stripe is caused by pion absorption events in T l and in the graphite absorber, and is not present in T l spectra. Carbon elastic events are at the lower end of this stripe; 12C(x, 2p) events form the continuum .40RUN 124. 66. 8 MEV9cmFig. 46. Preliminary results are plotted along with the published results of Brack et al. (solid dots). The curve is from SM86. Open squares are data from T l and open cir­cles from T2. The T2 data have been corrected for incident- pion energy loss in T l and in the absorber. The error bars on the open points reflect only statistical uncertainties.target and a directly m easurable acceptance geom etry for the pion counters. S tatistical uncertain ties con­trib u te about ha lf of th is to ta l. The beam structu re a t TR IU M F allows T O F and ADC identification of each particle incident on the target. Thus determ ination of muon and e± contam ination of the beam and of the fraction of the rf buckets delivering two or m ore pions to the target is very accurate. The related uncertain­ties contribute about one-third of the to ta l. The re­m ainder of the experim ental uncertain ty is due to con­siderations of solid angle, nuclear reactions in the ta r ­get, pion decay, ta rg e t thickness, com puter dead time, spread in beam energy, and scattering angle.Prelim inary cross sections have been obtained only a t T ,r = 66.8 MeV. These d a ta are in good agreem ent w ith the d a ta of Brack et al., op. cit. (see Fig. 46) and lay well below the SAID SM 86 phase-shift prediction of A rndt and Roper [SAID on-line program ], which does not include the d a ta of Brack et al.. We em phasize th a t these results are prelim inary, as the d a ta analysis is only about 1% com plete, and M onte C arlo calculations have not been done.E x p e r im e n t 397Q u a s ie la s tic s c a t t e r in g f ro m 12C a n d 16 O(T.E. Drake, Toronto)This experim ent received 12 shifts of polarized beam tim e in February. W ith only transverse polarization available a t th a t tim e, we m easured the spin trans­fer observables £>„<„, D s's , D]'s and P(9) a t 420 MeVfor inclusive quasielastic p ro ton scattering from 12C and 160 a t 24° using the MRS focal plane polarim e­ter. R esults are com pared to a relativistic-im pulse- approxim ation calculation where the N N interaction assumes the M * effect due to strong nuclear poten­tials. We note th a t P is quenched from the free value as predicted by the RIA calculation w ith M* = 0.86 M . This may be the clearest relativ istic signature since P is sim ply related to the scalar and vector am plitudes and the enhanced lower com ponents of the D irac wave functions. On the o ther hand our m easured D$is for 12C and 160 lies well below th a t predicted by the full RIA calculation. T his is suggestive of lim itations due to the nuclear m a tte r local density approxim ation and the local form used for the relativ istic am plitudes. De­tails are discussed in a p reprin t. W ith the longitudi­nally polarized beam recently m ade available we expect to extend the m easurem ents to include D sn and Din for both target nuclei in an upcom ing experim ent.E x p e r im e n t 399M e a s u re m e n t o f x e l a s t i c s c a t te r in g d if fe re n tia l c ro ss se c tio n s a t Tn = 30, 50 a n d 65 M eV(G.R. Smith, TRIUMF; R.A. Ristinen,TRIUMF/Colorado)A proposal to m easure absolute cross sections for ir^d elastic sca ttering a t low energies was approved in July. T he need for these x ^ d m easurem ents arises be­cause of the lack of such d a ta in the low-energy region for both 7r+ and x _ , because of questions concerning a bum p in the charge asym m etry param eter angular d istribu tion reported by Balestri et al., [Nucl. Phys. A 3 9 2 , 217 (1983)], because of the u tility of these cross sections in the acceptance calibration of m agnetic spec­trom eter system s, especially for x _ , and because of the fundam ental im portance of the xd in teraction to theo­retical trea tm en t of m ore general pion-nucleus systems. In fact, there have not yet been any angular distribu­tions reported for absolutely calibrated m easurem ents of x ± d elastic scattering from any of the meson facto­ries.In O ctober the in itia l phases of this experim ent were com pleted during two weeks of running during a period of reduced beam intensity. The prim ary proton beam was in the range of 30-50 fiA. A com plete set of elas­tic scattering d a ta was acquired for x + d and x _ d at 65 MeV and a lim ited d a ta set was obtained for both polarities a t 50 MeV.The experim ent utilized an active CD scintillator- ta rget to catch the recoil deuterons in coincidence with scattered pions detected in pion counter telecopes. The m ethod was essentially identical to th a t employed in the recently com pleted T R IU M F E xpt. 394, which41Run 19. firm C. 65 tleV p i+ .d .Fig. 47. A histogram of events in the active target ADC in coincidence w ith pions scattered at 1 1 0 ° in the labora­tory. The peak at channel 720 is due to recoil deuterons in the target. The peak near channel 150 is due to pion elastic and inelastic scattering from carbon in the target. The background under the deuteron peak is mostly due to deuteron break-up.m easured ir^p elastic scattering , and which is de­scribed elsewhere in th is report. The experim ental technique relies on the fact th a t recoil nuclei from pion scattering on 12C leave a sm all pulse height in the ta r ­get ADC. P ro tons from irp elastic scattering , however, produce a characteristically large pulse height in the target ADC. T he thickness of the CD scintillator was 200 m g /cm 2. A sam ple h istogram of the pulse height in the target scintillator is shown in Fig. 47, where the elastic deuteron peak is seen on a continuum from deuteron break-up events. D ata analysis is not yet suf­ficiently com plete for differential cross sections to be reported , bu t it does appear th a t the sta ted goals of the experim ent will be achieved a t 65 MeV. D ata will be taken for the lower energies when another run can be scheduled on M13, and when th inner CD targets arrive from the m anufacturer.E x p e r im e n ts 405 , 428N u c le a r w o b b le in th e r a r e e a r th n u c le i(D. Frekers, Toronto)Recently a new collective mode of nuclear excita­tion has been discovered in the rare earth nuclei [Bohle et a l , Phys. L ett. 137B , 27 (1984); ibid. 148B , 260 (1984)], where p ro ton and neutron deformed fluids are believed to perform ro ta tiona l oscillations against each o ther (nuclear “scissor” , or nuclear “wobble” ). In this picture the lowest excitation constitu tes an isovector M l transition whose B ( M 1) value is dom inatedby convective current contributions. T he excitation is the ro tational analogue of the electric giant dipole res­onance, bu t occurs a t considerably lower energies (be­tween 3 and 4 MeV). To assess the spin contam ination of the nuclear wobble we have perform ed a measure­m ent w ith interm ediate-energy protons scattered from the two ro ta tional nuclei 156G d and 164Dy. This exper­im ent is im portan t, since it tests the predicting power of various theoretical models (RPA, IBA-2, two-rotor- model).In Fig. 48 we show a spectrum of 164Dy (a) and 156Gd (b) for the scattering angles of 3.5°, 4.1° and 5.1° taken w ith 200 MeV incident protons. For 164Dy we observe 4 sta tes a t 2.52, 2.65, 3.14 and 4.6 MeV [labelled 1,2,3,4 in Fig. 48(a)] whose angular depen­dence is consistent w ith an M l transition . Only the sta te a t 3.14 MeV is observed in low-energy e~ scat­tering [Bohle, op. cit.] which is believed to be the isovector M l sta te in question. O ur m easured strength for th is s ta te is unexpectedly large and points to a spin contam ination of about 50%, in clear contrast to presently favoured IBA-2 predictions. Conversely, the sta te a t 3.08 MeV in 156G d is not observed w ith an upper lim it of 10 ^ b /s r and points to a predom inantly convective excitation (the faint s ta te appearing a t this energy has not an angular d istribu tion indicative for an M l transition). In a recent RPA calculation using sym m etry-restoring in teractions for K n = 1+ isovector v ibrations perform ed for a num ber of rare earth nu­clei, Nojarov and Faessler [1987 p reprin t, Tubingen] show th a t the m agnetic dipole transitions have pre­dom inantly o rb ita l M l character in all cases, except for 164Dy. A leading spin-flip configuration [541] 1/2 —► [541]3/2 (2/ 7/2 —► I/111/ 2) is present only in this nucleus.In E xpt. 428 we have extended our investigations to the p /-sh e ll nuclei 56Fe and 54Cr where sim ilar low- lying isovector M l transitions have been found in e~ scattering. These d a ta are presently being analysed.E x p e r im e n t 409Q u a s ie la s tic s c a t t e r in g o f Is s ta te n u c le o n s in lig h t n u c le i(C.A. Miller, TRIUMF)In early February 8 shifts of polarized beam were used to acquire analysing power d a ta for quasielastic scattering of protons deeply bound in the I s shell of 160 . T he purpose is to test for a nucleon density de­pendence of the p-p am plitudes. T he kinem atic con­stra in ts afforded by m easuring the m om enta of both final-state protons make it possible to select knockout of deeply bound protons and hence em phasize the nu­clear interior to a gra ter ex ten t th an is possible with42a)b ) 300250=200CO•g 150 is 100 cCJ50»«Gd(p.p') 6=3.5° 3.08 MeV156 Gd(p,p’) 0 =4.1 3.08 MeVB6 Gd(p.p’) 6=5.1*3.06 MeV0 50 100 150 0 50 100 150 0 50 100 150channel channel channelFig. 48. P roton spectra taken at 200 MeV incident energy for the target n u c le i164Dy (a) and 156Gd (b) at various scattering angles. The states labelled 1 , 2, 3 and 4 are possible M l states at 2.52, 2.62, 3.14 and 4.6 MeV. The sta te at 3.08 MeV observed in e~ scattering for 156Gd is weak and possibly contam inated by a neighbouring sta te with nonzero angular momentum.inclusive quasielastic m easurem ents. Also, restricting the experim ent to s-sta te knockout removes any un­certainty in the in terp re ta tion of the d a ta arising from effective polarization of the struck p ro ton in p sta tes due to the effect of distortion in the final-state chan­nels.The MRS was used to detect the high-energy scat­tered proton while a crude spectrom eter consisting of the PACM AN dipole w ith four “vertical d rift” cham­bers detected the coincident proton. The ra ther poor resolution of the PACMAN spectrom eter was ade­quate to distinguish I s from lp shell knockout. The beam energy was chosen to be 500 MeV where a rela­tivistic model [Horowitz and Iqbal, Phys. Rev. C 33, 2059 (1986)] for the density dependence predicted the largest effect on the analysing power.D a ta were acquired a t three angle pairs and are presently being analysed. P relim inary indications are th a t in kinem atic conditions where the analysing power is m axim um , it is substan tially reduced from the free value, as predicted by the relativ istic model. T he re­duction appears to be much larger th an is observed in inclusive quasifree scattering.I t is p lanned to continue th is investigation in 1988 w ith the first m easurem ent of sp in-transfer observables in an exclusive quasifree scattering experim ent.E x p e r im e n t 411T h e sp in - iso s p in re s p o n s e o f 48C a a n d 9B e f ro m th e (n ,p ) r e a c tio n a t 200 M e V (R .G . Jeppesen, SFU;O. Hausser, SF U /TR IU M F ; K.P. Jackson, TRIU M F)E xperim ent 411 was run after we were able to bor­row a costly 48C a ta rg e t from Los Alamos. Unfor­tunate ly th is 9.4 g “m etallic” ta rget (four foils of about 110 m g /cm 2 each) consisted largely of the hy­droxide, and the d a ta obtained are of lim ited value. T he original p lanned five angles were reduced to three (#m r s = 0°, 6° and 12°) in order to get b e tte r sta tis­tics. 9Be and BeO foils were run in the sam e stack as the 48C a so good d a ta were ob tained for 9Be and 160 a t the three angles.Figure 49 shows the 48C a ta rg e t spectrum a t 0M r s = 0°. The overwhelming peak a t about channel 2300 comes from charge exchange on hydrogen contam ina­435000-4000-n 3000■4-»a3§2000-10 0 0 -**Ca ta rg e th y d ro g e nc o n t a m i n a t i o n4000 8000 XF (channel)12000 16000Fig. 49. Zero degree (n ,p ) spectrum from the 48Ca ta r­get. The large peak in channel 2300 is due to hydrogen contam ination in the target. The shaded region shows the background this peak gives due to the tail on the incident neutron beam.tion in the target. Since the incident neutron beam is not m onoenergetic th is peak also contributes a back­ground under the d a ta a t higher excitation; th is back­ground is indicated by the shaded region in Fig. 49. This is a su bstan tia l background bu t it is also well un­derstood from m easurem ents on C H 2 targets. We also have background from the th in beryllium foils th a t en­cased the 48C a ta rg e t and from oxygen contam ination of the target. T he form er is easily accounted for since we know the thickness of the windows and since the 9B e(n ,p ) cross section was m easured. We hope to de­term ine the am ount of oxygen contam ination by look­ing for low-lying 16N sta tes which should be resolved from the 48C a(n ,p ) because of the lower Q-value.Figure 50 shows the spectra obtained for 9B e(n ,p) and 160 ( n ,p ) a t 0m r s = 0°. T he 9Be d a ta will be used to look a t the ra tio of zero degree cross sec­tion to B (G T ) for a s ta te which has a B ( G T ) nearly two orders of m agnitude sm aller th an those studied in E xpt. 266. T he large fluctuations in cr(0° ) /B ( G T ) seen in the (p, n) reaction were not observed in (n ,p) (E xpt. 266), and it would be interesting to see if the p roportionality holds for sm all B ( G T ) ’s. The angular d istribu tion , though ra th e r sparse, should tell us if the peak has the expected L = 0 shape.Analysis is currently under way, w ith careful con­sideration being given to background sub trac tion both in the 48C a d a ta and in the 9Be d a ta where the G T peak is a t about the sam e Q -value as 12C (n ,p ) from the m ylar foils of the ta rg e t box.XF (channe l )XF (channe l)Fig. 50. Zero degree (n ,p ) spectra from 9Be (top) and 16O (bottom ). Neither is corrected for the tail on the incident neutron beam. The peak at channel 6400 in the 9B e(n,p) spectrum is the G T sta te of interest. The peak at chan­nel 5600 in the 160 ( n ,p ) spectrum is a 2~ sta te at 0.1 MeV of excitation.E x p e r im e n t 421R e s e a rc h a n d d e v e lo p m e n t s tu d ie s w ith T IS O L(J.M. D ’Auria, Simon Fraser)T his experim ental program involves the use of the new on-line isotope separato r (TISO L), the proto­type of the vertical ISOL device proposed for the m a­jo r ISAC (ISO L /accelerator) facility for nuclear as­trophysics [Nucl. Instrum . M ethods B 2 6 , 151 (1987)]. The general objectives of the present program are to develop and use the TISO L facility to address scientific and engineering questions of im portance to the ISAC facility and to assess the usefulness of TISOL (or an upgraded version) as a general facility for physics re­search (nuclear, atom ic, condensed m a tte r and surface physics).A general technical description of TISO L and its per­form ance in an off-line position above the beam line 4A shielding blocks was presented in the 1986 annual re­port and elsewhere [Nucl. Instrum . M ethods B 2 6 , 143 (1987)]. Recent developm ents are given in the Experi­m ental Facilities section of th is report, p. 124.44T able V II. R esu lts of T ISO L experim en t.Radioisotope T1/2 Yield Target/ion source ISOLDE yield(atom s/s//iA ) (a to m s/s/^A )Sum m ary of on-line results:potassium-38 7.4 mo 2.8 X 10® (2 g)potassium-38 7.4 mo 5 x 10® (1 g/ cm 2)potassium-38 7.4 mo 1.6 x 10spotassium-43 22 h -potassium-44 22 mo 2.2 x 10 ® (1 g/cm 2)potassium-45 17 m 5.6 x 10s (1 g/cm 2)sodium -21 22 s -sodium-24 15 h -sodium-25 59.6 s 8 x 104(2 s)sodium-25 59.6 s 3 x 105 (1 g/ cm 2)sodium-26 1.09 s -ScO /C - rhenium surface 8 x 10 7Ti - rhenium surface(3g) 1.4 x 109Ti - plasm a source(40 g /cm 2)T i - rhenium surface 1.4 x 109Ti - rhenium surface 6 x 10®T i - rhenium surface(40 g /cm 2) 1.7 x 10®T i - rhenium surface (40 g /cm 2)T i - rhenium surface 1.5 x 107Ti - rhenium surface 5.5 x 10®ScO /C - rhenium surface 9 x 107Ti - rhenium surface(10 g /cm 2) 9 x 107Ti - rhenium surface(40 g /cm 2) 2 x 10®Summary of off-line results:Beams produced Ion sourcesRb, Ca, K, Na Heated surface - W, Re, P t, TaAr, Xe Plasm a (Bernas-Nier type)Over the last twelve m onths as p a rt of th is experi­m ental program the TISO L facility has been installed onto beam line 4A and used successfully both on line (w ith the proton beam ) and off line. In a series of weekly runs using unpolarized protons both a surface ion source (w ith either Re, Ta, P t or W m etals as ioniz­ers) and a p lasm a source (Bernas-N ier type), designed by the group a t the Foster R adiation Lab, McGill Uni­versity, have been used. A sum m ary of the observed radioisotopes and yields is displayed in Table VII.E x p e r im e n t 431C o m p le te s p in o b se rv a b le s fo r q u a s ie la s tic p r o to n s c a t te r in g f ro m 54Fe a t 290 M e V(0 . Hdusser, SFU/TRIUMF; R. Abegg, TRIUMFM easurem ents of com plete sets of observables (dif­ferential cross sections d a /d f t , induced polarizations P and spin ro ta tio n functions Q ) have played a cru­cial role in arriving a t a satisfactory quantita tive de­scription of elastic p roton scattering . A t present impressive agreem ent w ith experim ent can be ob­tained using either relativ istic (D irac) or nonrelativis­tic (Schrodinger) dynam ics (see E xpt. 382). In the successful relativ istic calculations of elastic nucleon- nucleus sca ttering by Horowitz and M urdock the opti­cal po ten tia l is obtained by folding the N N t-m atrix w ith the (relativistic) nuclear ground s ta te density dis­tribu tion . T he t-m a trix assumes pseudovector n N cou­pling and explicitly includes exchange. Pauli blocking and binding energy effects which are particu larly im­p o rtan t for heavier nuclei a t energies below 400 MeV are included by reducing the optical potentials with a density-dependent Pauli blocking factor determ ined from relativ istic nuclear m a tte r calculations.In the sim ilarly successful nonrelativistic calcula­tions of von G eram b et al. ground s ta te densities from electron scattering and the N N G -m atrix (again in­45eluding explicit exchange) are used to produce the op­tical potentials. Pauli blocking and other m edium ef­fects are included in the density-dependent G -m atrix , a m ore consistent procedure th an adopted in the rela­tiv istic calculations.Inclusive inelastic p ro ton sca ttering experim ents are of high curren t interest. Near the peak of the quasielas­tic continuum (energy transfer u> = q2/ 2M )) spin ob­servables are expected to be ra ther insensitive to nu­clear s tru c tu re details and to d isto rtion effects. The nonrelativ istic calculations of quasielastic scattering [(see, for exam ple, Sm ith and W allace, Phys. Rev. C 32, 1654 (1987); Sm ith, private communication] pre­dict the free N N values a t the peak and deviations observed are then likely the resu lt of either the collec­tive nuclear response or of m odifications of the N N in teraction in the m edium . Because of a richer choice of independent spin observables (there are seven for quasielastic scattering com pared to two for elastic scat­tering) proponents of D irac phenom enology [Horowitz and Iqbal, Phys. Rev. C 33, 2059 (1986); Horowitz and M urdock, preprint] hope to ob tain evidence for the strong scalar and vector po ten tia ls in the nuclear m edium and constrain ts on o ther pieces of the rela­tiv istic N N in teraction .T he experim ental conditions of E xpt. 431 were cho­sen to com plem ent the only existing com plete set of observables for 500 MeV quasielastic proton scattering from 208Pb a t a m om entum transfer q — 1.75 fm - 1 [Carey et a l , Phys. Rev. L ett. 53, 144 (1984)]. A t the lower energy of 290 MeV five spin observables are pre­dicted to be sensitive to relativistic m edium effects (at 500 MeV only A y and P differ from the free values). D istortion and Pauli blocking effects are expected to be more significant a t lower energies. The sm aller mo­m entum transfer (q = 1.36 fm - 1 ,0 iab = 20.05°) was chosen to introduce some sensitivity to the nuclear re­sponse function. T he present experim ent is thus well suited to guide the developm ent of a consistent and com plete theory of quasielastic p roton scattering sim­ilar to the ones already existing for elastic scattering .T he experim ent was the first one to use the longi­tud inally polarized beam which was m ade possible by the addition of two superconducting solenoids in the vault section of beam line 4 (see instrum enta tion sec­tion). The three com ponents of the beam polarization were carefully m onitored using in-beam polarim eters in beam lines 4A and 4B which differ by a 15° bend. D ur­ing the longitudinal (/) running period the transverse com ponents were typically 1% or less. T he sideways (s) polarized beam was produced by ro ta tin g the norm al (h) com ponent through 90° using a superconducting solenoid ju s t upstream of the in-beam polarim eter in beam line 4B. By reversing the incident beam polar­0 20 40 60 80 100v (MeV)Fig. 51. Differential cross sections (top) and spin-transfer cross sections (bottom ) for inclusive proton scattering of 290 MeV protons from 54Fe a t 20°. The theoretical curves represent relativistic (solid lines) and nonrelativistic (dashed lines) calculations explained in the text. The sys­tem atic uncertainty in the cross section was estim ated to be less than ±5% .ization and the po larity of the solenoid current four separate d a ta sets were ob tained which allowed us to exactly cancel effects o f th e sm all 1-co m p o n en t in th e beam . T he transverse com ponents of protons scattered a t 20° from a 94 m g /cm 2 th ick 54Fe target were deter­mined using the focal plane polarim eter (F P P ) of the MRS. Because of the vertical bend of the spectrom eter p a rt of the longitudinal com ponent after scattering (/') is precessed into the norm al plane of the F P P and all three com ponents of the scattered pro ton could thus be m easured.The norm al (n) beam was also used to m easure cross sections and analysing powers. In Fig. 51 the cross sections (35 0.40.20.00.8. 0.6 n=T0.4 0.2 0.0 0.8 % 0.6 0.4 0.2 0.001“ I 1-----1---- rn r-I— I— 1..4— I - I I I I* i i-t - i - • I ' I I I I_J I I I 1 I I I I_u (MeV)20 40 60 80 100CO (MeV)Fig. 52. Com plete spin observables for inclusive proton scattering of 290 MeV protons from 54Fe a t 20°. In addition to the theoretical curves explained in the caption of Fig. 51 we show free N N values (dotted lines) as explained in the text.gas. T he nonrelativ istic calculation includes two-step contributions and a sophisticated semi-infinite slab re­sponse w ith lp artic le -lh o le and 2particle-2hole RPA correlations. D ensity-dependence of the N N interac­tion is, however, ignored, and Fermi m otion is sim­ulated sim ply by trea ting the hard scattering in the Breit fram e. In bo th calculations d istortions of incom­ing and outgoing waves are trea ted realistically m ak­ing use of elastic sca ttering d a ta previously obtained at TR IU M F. The cross sections for the broad quasielastic peak are in good agreem ent w ith both calculations, the experim ental w idth is, however, larger th an the theo­retical w idth, especially th a t o f the relativ istic model. The observed spin-transfer strength is shifted towards larger energy transfers th an predicted.T he spin transfer coefficients D u 1, D n n , D aai, D taiand —D si / which are equivalent to the W olfenstein pa­ram eters A ! ,D , R, A and —R 1 are shown in Fig. 52 to ­gether w ith the induced polarization P and analysing power A y . Corrections for the sm all polarization com­ponents of the incident beam are included. The ex­perim ental errors include the uncertain ties in all three beam polarizations, errors in the spin precession an­gle th rough the MRS dipole, and s ta tis tica l errors in the polarizations m easured w ith the F PP . In addition to the theoretical curves described previously we show quasifree param eters (do tted lines) which take nuclear Fermi m otion into account. T he experim ental spin ob­servables show w ithout exception a pronounced slope versus energy transfer. T he slope in D nn and P is well reproduced by the nonrelativ istic RPA slab response which pushes S = 0, T = 0 streng th to lower A y or47energies. In cases where the RPA slab response pro­duces the wrong sign of the slope (for D U' and D,,>) th is may be a ttrib u ted to the use of the Breit frame. In the relativ istic calculations which explicitly include Fermi m otion averaging these slopes come out cor­rectly. O ur d a ta contain evidence for m edium effects included in the relativ istic calculations by an effective nucleon m ass M * = 0.87M . M ost pronounced is the effect for P and A y , a lthough there is some sensitivity in the o ther observables w ith the exception of D nn.We conclude th a t a satisfactory theory of quasielas­tic is still lacking. From the results shown in Fig. 52 we identify as the essential ingredients of such a theory the self-consistent inclusion of Fermi m otion averaging, of m edium m odifications of the N N in teraction , and of a realistic nuclear response function.E x p e rim e n t 433N e u tro n -p ro to n charge exchange a m p litu d es(C.A. Miller, TRIUMF)M ost m easurem ents done w ith the T R IU M F nucleon charge exchange facility have the goal of exploring nu­clear s tru c tu re using n-p charge exchange as the probe. Gamow-Teller nuclear transitions are excited by the spin-flip p a rt of the in teraction while Fermi transi­tions are excited by the nonspin-flip p a rt which is much sm all and im precisely known in the T R IU M F energy region. E xperim ent 433 has the goal of refining our knowledge of th is probe in two distinct aspects.T he unique capability of the facility to m easure rel­ative cross sections w ith high precision is exploited in the com parison of (n ,p ) on hydrogen and deuteron targets (in the form of polyethylene). The 7Li(p, n) reaction provides the alm ost m onochrom atic neutron beam . Because D ( n ,p ) a t very sm all m om entum trans­fer m ust leave the residual diproton in a pure singlet s ta te , only the spin-flip p a rt of the in teraction can con­tribu te . I t is hoped th a t a second-order G lauber calcu­lation as developed by Bugg and W ilkin [Nucl. Phys. A 4 67 , 575 (1987)] can be used to in terp ret the relative yields from the two reactions in term s of the strength of the sm all nonspin-flip am plitudes which contribute only in the H {n ,p ) or elastic case.T he second phase of the experim ent is directed to ­ward im proving the precision of our knowledge of the absolute differential cross section for n-p elastic charge exchange. T he novel technique involves combining the precise m easurem ent of the ratio of the cross sections for D { n ,p ) and H (n ,p ) as described above w ith an­other m easurem ent of their product. The la tte r quan­tity is determ ined from the yield of the double scatter­ing process D(p, n ) following by H (n ,p ) . Charge sym­m etry is invoked to relate the D (p , n) and D (n , p) crosssections. The crucial experim ental po in t is th a t an ab­solute m easurem ent of a p roduct of two cross sections is ha lf as sensitive to the system atic errors lim iting the u ltim ate accuracy. T hus 2% uncerta in ty in the abso­lu te yield from the double scattering process should re­su lt in a 1 % determ ination of the H {n ,p ) elastic cross section. This will be a su bstan tia l im provem ent over the uncertain ties in the existing d a ta which range up to 5% or m ore a t 200 MeV.A lm ost all of the d a ta have been recorded for this experim ent and analysis is proceeding well. The only m easurem ent rem aining to be done is a check on the degree of C D 2 ta rg e t degradation during exposure to the prim ary proton beam . This will be done using proton elastic scattering from deuterium a t relatively small angles w ith diffuse illum ination of the target.E x p e rim en t 438A s tu d y o f th e P au li b locking o f G am ow -T eller t r a n ­sitions using th e 70’72’74Ge(ra,p)70,72’74G a reac tio n s (M.C. Vetterli, Simon Fraser; K. P. Jackson, TRIUMF)E xperim ent 438 is a study of the effect of Pauli blocking on Gamow-Teller streng th using the reactions 7°,72,74Qe(n p)70,72,74Qa x h e 70Ge case has an al­lowed transition from the p3/ 2 pro ton shell to the p 1/ 2 neutron shell. However, in 72Ge and 74Ge, the p 1/ 2 orbital is full and th is transition is blocked. G T tran ­sitions are possible only if one-particle-one-hole and two- particle-tw o-hole excitations are included. This is shown in Fig. 53.D a ta have been collected for 70Ge and 72Ge a t 0°, 3°, 6°, 10° and 15°. The beam energy was 200 MeV. The expected reduction in G T streng th was seen in the on­line spectra. D ata for 0° and 3° are shown in Fig. 54. One sees clearly th a t there is streng th in 70Ge around channel 11500 which is absent in 72Ge. Furtherm ore, a com parison of the 0° and the 3° 70Ge spectra shows th a t th is s treng th is consistent w ith A A =0 angular mo­m entum transfer which is characteristic of a G T transi­tion. T he peak in channel 10500 for both nuclei is due to hydrogen contam ination from counter gas and win­dows. Since the G T cross section for 72Ge was small, it was decided not to do the 74G e(n ,p ) reaction until the d a ta on the o ther two isotopes are analysed. Off-line analysis is in progress.E x p e rim en t 466T h e np —^ wd cross sec tio n v e ry n e a r th re sh o ld (D. Hutcheon, TRIUMF)Near the threshold of the pp° <-*■ ttd reaction the only m easurem ent of cross section is th a t of Rose [Phys. Rev. 154, 1305 (1967)], who observed the reaction of48countscountscountsXFK XFKFig. 54. On-line spectra for the 70,72G e(n ,p )70,72Ga reactions at 0° and 3°. The low-energy peak around channel 10500 is hydrogen contam ination from the counter gas and windows. There is clearly more strength in 70 Ge than in 72 Ge, as expected. Furtherm ore, a comparison of the 0° and 3° spectra shows th a t this strength is L = 0, characteristic of G T transitions.4970,72,74G eIICMFig. 53. Simple shell model structure of the germanium iso­topes. The 39/2 neutron pair is present only for 74 Ge, while the px/2 neutron pair is present in both 72,74 Ge. The pos­sible Gamow-Teller transitions are indicated by the large arrows. Transition 1 is allowed for 70 Ge and blocked for 72,74Ge. Neutron particle-hole excitations out of the p i/2 shell (labelled A) would open this channel in the la tte r nu­clei. Transitions 2 and 3 are blocked in all three nuclei to first order. A dm ixture of the (p3/2)2( / s /2 )2 configura­tion (B) in the germ anium ground state , coupled with the particle-hole excitations of the type labelled C, would lead to allowed G T strength to the / 5/2 neutron shell.of low-energy pions stopping in a deuterium bubble cham ber. These d a ta are of in terest because (1) the effect of x N S -wave rescattering is seen w ith mini­m al “background” , from A excitation, and (2) there is a h in t of a resonance a t c.m. energy 3 MeV above threshold. T he T R IU M F CH A RG EX facility, w ith its high-resolution neu tron beam , allows a study of the N N —► dx process to w ithin 1 MeV (c.m .) of threshold w ith none of the problem s of a beam of very low-energy pions: we use a liquid hydrogen ta rg e t and detect only the deuterons from the reaction np —*■ d x ° . Norm al­ization is provided by pro tons from np —+ p n , which are detected in the m edium resolution spectrom eter (M RS) together w ith the deuterons.We were able to m easure np —*■ dx° yields a t nom i­nal (neutron) beam energies of 275, 276, 278, 280 and 289 MeV during a 7-shift run in O ctober. Background was negligible even a t the lowest energy, thanks to veto and trigger scintillators m ounted in the cryostat and separated from liquid hydrogen by windows only 50 p m thick. T his is evident in the on-line sca tterp lo t (Fig. 55) obtained a t a nom inal energy of 280 MeV in less th an two hours’ running. Final analysis will require a b e tte r knowledge of the acceptance and dis­persion of the MRS th an has been needed by previous experim ents; the necessary calibrations are scheduled for Jan u a ry 1988.■oo-g, 3200cqoo jr.. .T ; ■r . .Si1:-: :S• ./:i:•- o £ 20 zUJO? 15 o z ote-10\ 208Phh \\\ v ? 1 w \ \ ^ \ \ \ \89yA SINGLE PARTICLE STATESJ FROM BROOKHAVEN U*,K*) DATA -a WOODS-SAXON A POTENTIAL(V0 = 29.34 MeV, r0 * 1.08 fm, o = Q6fm)I I I I------, , y ^ 5>"°C0\ \ \ \ " f 4\ \ \ x *\ \ \ * x \ \ \28,SiR«r0 Al/3(l + f/r|A 2;’3) 0.427 fm2Is\ \w■s>» - \ld* V \' \ _ X 50 ps) p S R signal a t the bare m uon Larm or frequency. Upon ad­dition of a sm all concentration of a reac tan t gas (X) though, the signal assumes a two-com ponent relax­ation described byS ( t ) = ( A / e ~ Xjt + A se~ x , t )cos(wD)t + D) ,as shown in Fig. 58. T his is understood in term s of a simplified reaction m echanism involving com peting reactions: charge exchange w ith the reactive dopant to form m uonium (w ith ra te &C[X]), muon transfer to produce diam agnetic X M u+ (w ith ra te fct [X]), and “quenching” reactions w ith the m oderator (w ith ra te fc,[M]) preventing M M u+ from reacting further:A l u + X+ + M [MMu+]* + X < 7 ^l > X M u + + MMMMu+Since m ost reactan ts will not charge exchange w ith a ground sta te M M u+ , the in itia l m olecular ion m ust be in an excited s ta te , and reactions w ith the m oderator are identified as quenching of th a t excited state.Only the charge exchange channel provides depolar­ization, so the am plitude of the fast relaxing signal is given by A j / A s = &c[X]/(&t [X]+&?[M]). However, the fast relaxation ra te A/ is ju s t the depletion rate of the [MMu+]* ion; Xf = (kc + fct )[X]-t-&?[M]. Thus a plotCD 3OH = (10.3±0.5) x 10~4 CH 3OD = (53.8±1.0) x 10" 4 CH 3OH = (71.5±1.0) x 1(T 4(These are norm alized to C H 2 a t 129 x 10- 4 .)Because C D 3OH + CH3OD do not add up to CH3OH, it is clear th a t the deuterium is not an in­ert specta to r bu t steals some pions. A sim ilar transfer effect was observed in m ixtures of brom odecane and carbon tetrachloride. More com plete d a ta on th is sys­tem will be taken during our next run.E x p e r im e n t 340M u o n m o le c u la r io n s a n d io n -m o le c u le r e a c tio n s (D .J. Arseneau, UBC)Over the past four years E xpt. 340 has m easured the reactions of the m olecular ions HeM u+ , NeM u+ and A rM u+ form ed by stopping positive muons in the respective gas m oderator (M = He,Ne,Ar). These ionsTime (fj.s)Fig. 58. The /rSR signal from 4514 molec cm -3 of NO in 800 Torr N2 . The relaxing signal has an am plitude of only 0.059 and there is virtually no nonrelaxing component.530 5 10 15 20 25 30[C2H4F2] (10* m olec/cm 3)Fig. 59. A ra te plot for the reaction of difluoroethane with HeMu+ at 133 C. The slope gives a rate of 9 x 10 -10 molec4.0 5.0 6.0 7.0 8.0 9.0r V2 (io~2 k-^2)Fig. 60. The tem perature dependence of \ f for difluo- roethane and acetaldehyde, bo th in helium. Although the rates are plotted against T -1 2^, they do not m atch the ADO predictions.of Ay vs. [X] gives a stra igh t line w ith slope kc + k t and in tercep t &9[M], as shown in Fig. 59. W hat is not clear from the m echanism shown above is th a t both the charge exchange and m uon transfer reactions proceed from an initial cap ture of X on the m olecular ion. Thus k c + k t — ^capture when the capture is the lim iting rate. T he cap ture m echanism is easily analysed theoretically, and m any simple models exist for predicting its rate, particu larly the ADO theory.Over the past year we have w rapped up E xpt. 340 w ith m easurem ents of tem pera tu re dependences of these ion-molecule reaction rates, tests of the depo­larization m echanism , tests of quenching, and a brief search for m olecular ions in m olecular gas m oderators.The reactan ts for the tem perature-dependence m ea­surem ents were chosen to have large dipole m om ents in order to m axim ize variations in reaction ra te as the tem pera tu re was varied. U nfortunately, the two w ith the largest dipole m om ents, acetonitrile and ni- trom ethane, give respectively no fast relaxation and a very sm all one, providing no test of the applicability of the ADO theory (though the n itrom ethane result agrees w ithin its broad lim its). T he other tem peratu re dependences were very surprising though. B oth ac­etaldehyde and difluoroethane showed much stronger tem pera tu re dependences th an the T 1/2 predicted by an ADO trea tm en t, giving negative high tem peratu re lim its on the capture ra te constant. These trends are illustra ted in Fig. 60. A lthough only prelim inary anal­ysis has been done, the dram atic tem pera tu re depen­dences are clear and indicate as-yet unelucidated pro­cesses a t work.Previously, we were in some doub t as to the depo­larization m echanism for reactions w ith nitric oxide (NO). This was of some concern because NO exhib­ited the only unam biguous reaction w ith the A rM u+ molecular ion. NO has a low ionization po ten tia l allow­ing charge exchange even from deeply bound molecular ion states, and it forms the param agnetic ion N O M u+ which could provide depolarization independent of the charge exchange channel. M easuring the zero field pSR spectra of bo th NO in Ne and Xe in Ne revealed th a t the depolarization m echanism in b o th cases is likely m uonium form ation. This is because A j was reduced by a factor of two in b o th m ixtures, reflecting the frac­tion of m uonium th a t is depolarized in zero field.We investigated quenching by adding Ar to N20 /N e , N O /N e and X e/N e m ixtures. Q uenching w ith Ar re­duces the Xe reaction ra te , leaves the NO reaction un­changed, and increases the N 20 reaction ra te while de­creasing the am plitude. T he first result was not unex­pected because we have come to the conclusion th a t Xe undergoes sequential reactions no t lim ited by simple ion-molecule capture. The o ther resu lts were in com­plete accord w ith our previous understanding . N20 has an ionization poten tia l of 12.89 eV and can only charge exchange w ith an excited NeM u+ ion, while NO, w ith an ion po ten tia l of 9.25 eV, can react w ith a ground sta te NeM u+ ion. T hus, quenching of the ex­cited sta te has no effect on the NO reaction bu t com­petes successfully w ith charge exchange in the case of N20 .Finally, we found evidence for the form ation of molecular ions in nitrogen, bu t not in m ethane. Ad­54dition of NO to nitrogen resulted in spectra as shown in Fig. 58, indicating the presence of N2M u+ . No re­laxing signals were observed for sim ilarly doped CH 4 , supporting the belief th a t the diam agnetic signal in gaseous hydrocarbons is the result of hot a tom reac­tions yielding diam agnetic molecules such as MuH.E x p e r im e n t 362H igh p re ssu re m u o n sp in reso n an ce in liquids(P.W. Percival, Simon Fraser)E xperim ent 362 was conceived to explore the possi­b ility of m uonium chem istry studies of liquids a t high pressures. Following developm ent of the apparatus, m ost effort was directed tow ards the m easurem ent of m uonium decay rates as a function of pressure in aque­ous solution. A paper on th is subject has been ac­cepted for publication in the jou rnal R adiation Physics and Chem istry. O ther aspects of the experim ent have been transferred to E xpt. 450— ^S R studies of sub- and supercritical fluids.T he high-pressure cell and fittings are m ade of beryllium -copper alloy, h ea t-trea ted for m axim um strength after m achining. A schem atic representa­tion is given in Fig. 61. The cell is pressurized with a 7 kbar hydraulic hand pum p charged w ith paraffin oil and connected via stan d ard non-m agnetic stainless- steel high-pressure tubing. A floating piston communi­cates the applied pressure to the liquid sam ple, which can be in direct contact w ith the cell body if non- corrosive, or else encapsulated in a deform able plastic vial. T he muon window is 2.5 m m thick and 12 m m in diam eter. T he whole appara tus has been tested up to 4 kbar, bu t the f iS R experim ents were lim ited to 2 kbar for safety reasons.To ensure a good muon stopping d istribu tion , the beam (M20A backward m uon channel, nom inal m o­m entum 88 M eV /c) was collim ated to 10 m m andCollimatorMuonBeamNN P CHydrostaticZZZJpressureScintillators1 5 cm ,I 1 1 1 JFig. 61. Schematic representation of the high-pressure cell and scintillator arrangem ent.scattered m uons were vetoed by a scintillator w ith a 10 m m hole in front o f the window. Decay positrons were detected by two scintillator telescopes, one placed above and the o ther below the cell. Tests w ith various standard sam ples (alum inum , ferric oxide, w ater, car­bon tetrach loride and 50% m anganous n itra te in wa­ter) show th a t 90±3% of the incom ing muons stop in the sam ple region, and only 10% in the cell walls and window.M uonium decay rates were m easured for pure wa­ter, aqueous solutions of sodium n itra te (0.29 mM and 0.58 mM ), and aqueous solutions of potassium perm an­ganate (0.050 mM and 0.10 m M ). Oxygen was purged from the liquids by bubbling w ith nitrogen. //SR his­togram s containing 10-15 million events were accumu­lated for each of the positron telescopes. M uonium re­action rates (Am ) are sum m arized in Table IX. TheseTable IX. Pressure dependence of m uonium reaction rates in aqueous solutions.Sample P /k b ar A m /ps 1 dlnAjvrdp/kbar0.29 mM NaNOa 0.0011.002.000.62 (8) 0.78 (8) 1.12(13)0.30 (8)0.58 mM NaNC>3 0.0011.002.000.83(10)1.11(15)1.49(19)0.29 (9)0.05 mM K M n 0 4 0.0011.002.000.88(15)0.63(15)0.65(14)-0.16(13)0.10 mM K M n 0 4 0.0012.002.17(23)1.71(20) -0.12 (7)rates represent the m ean of the experim ental decay rates determ ined from the two histogram s, corrected for a contribu tion (Ao, typically 0.3 fts- 1 ) due to en­vironm ental effects. Figure 62 shows how the reaction rates change w ith pressure. For ease of comparison the rates for each sam ple are p lo tted relative to the atm ospheric pressure value.T he pressure dependence of reaction rates provides valuable inform ation on the transition sta te of a chem­ical reaction. T he volume of activation is defined byA V t = - R T ( d ln k /d P ) Tand is in terpreted as the difference in p artia l molar volume between the transition s ta te and the separated reactants.55Pressure/ kbarFig. 62. Pressure dependence of relative muonium reaction rates in aqueous solutions of sodium n itra te (o 0.29 mM, • 0.58 mM) and potassium perm anganate (□ 0.050 mM, ■ 0.10 mM).T he reactions of m uonium w ith NO 3- and MnC>4- were found to have activation volumes of —7.1 ± 1.5 cm 3m ol- 1 and +3 .1 ± 1.6 cm 3mol~ \ re­spectively. These volumes can be com pared w ith —5 cm 3m ol_1 and + 2 cm3m ol_1 for activated and diffusion-controlled reactions of hydrogen atom s. The isotope effect supports the concept of local order of the w ater molecules around each H or Mu atom in so­lu tion . T he larger cavity occupied by Mu has been dem onstrated in m olecular dynam ics sim ulations per­form ed a t NRC O ttaw a by M.L. Klein et al.E x p e r im e n t 367R esolved n u c lea r h y p erfin e s t ru c tu re o f anom alous m u o n iu m in sem ico n d u c to rs(R .F . Kiefl, TRIUM F; T.L. Estle, Rice)In terest in m uonium centres in sem iconductors arises because they are simple defects whose electronic struc­tures are closely related to those of hydrogen and the fact th a t there have been no reported observations of isolated param agnetic hydrogen in a sem iconductor (see note added a t the end). T he so-called anomar lous m uonium centre (or Mu*), which has been seen in bo th the elem ental group IV and com pound group III-V m aterials, has a sm all anisotropic muon h f in ter­action, axially sym m etric about a < 1 1 1 > crystalline axis. Several conflicting models for the s truc tu re ofMu* have been proposed, two receiving considerable theoretical study. In one, Mu* is a substitu tional muon (trapped a t a vacancy) w ith an overall charge of + 2e (in the group-IV m aterials) and in the o ther it is a neutral in terstitia l located a t a bond centre.T he m ajor objective of E xpt. 367, to distinguish these models, has been acheived in the past year. The electronic struc tu re of the Mu* centre has been deter­m ined in b o th GaAs, a group III-V m ateria l w ith the zinc-blende crystal struc tu re , and Si, a group IV m ate­rial w ith the diam ond crystal struc tu re . In GaAs the nuclear hyperfine (nhf) s tru c tu re of Mu* was resolved using the technique of level-crossing-resonance (LCR) spectroscopy, which was pioneered a t TR IU M F. These results clearly dem onstrate the power of th is m ethod for determ ining nuclear hyperfine structu re of muo­nium centres in solids. T he largest n h f interactions are for a single G a and a single As on the < 1 1 1 > sym­m etry axis as predicted from the bond-centred (BC) model of Mu* in the zinc-blende s tru c tu re group III-V crystals. On the o ther hand the results were incon- isten t w ith the vacancy model. More details may be found in a recent publication [Kiefl et al.. Phys. Rev. L ett. 58, 1780 (1987)].Resolving the nuclear h f s tru c tu re of Mu* in Si was more challenging th an in GaAs because of the low (4.7%) isotopic abundance of 29Si. T his was offest by the fact th a t the results in Si are of far greater im por­tance because(1) D etailed theoretical calculations on Mu* have only been a ttem p ted on the elem ental m aterials Si and diam ond.(2) In Si there is inversion sym m etry about the bond centre. Consequently the BC model, which predicts there should be two electronically equivalent Si neigh­bours, can be tested w ith v irtua l certainty.(3) The role of hydrogen in crystalline and am or­phous silicon is far m ore im p o rtan t from a technologi­cal aspect th an th a t of hydrogen in GaAs.It was necessary to modify our experim ental ap­proach for the Si experim ent. In particu lar since the LCRs due to 29Si were expected to be small, thus re­quiring high sta tistics, it was not feasible to do a blind search for the LCRs as had been done in GaAs. Instead we a ttem p ted and succeeded in resolving the weak 29Si lines in the m uon spin ro ta tion (//SR) frequency spec­tra in transverse m agnetic fields of 5-50 m T. This has the advantage of not requiring a search although the event ra te is considerably lower th an in an LCR exper­im ent. In th is field region the m uon precessional fre­quencies of the Mu* centres having a nearest neighbour (NN) 29Si are split by a few MHz and have an average position shifted relative to the m ain lines, correspond­ing to centres where all NN nuclei are 28Si (sp in=0 and56432130 H-------L-* i------------1------------i----------- 1----------- 1----------- b0 10 20 30 40 50 60FIELD (m T)FREQUENCY (MHz)Fig. 63. The muon frequency spectrum in Si w ith a field of 23.5 m T aligned along a < 100 > crystal direction. The small satellite lines, indicated by arrows, are due to Mu* centres which have one nearest-neighbour 29 Si on the < 1 1 1 > sym m etry axis.Fig. 64. The m agnetic field dependence of the /rSR fre­quencies in Si w ith the field aligned along the < 100 > crystal direction. The solid (dashed) curves are predicted if none (one) of the nearest-neighbour nuclei on the sym­metry axis is 29 Si.4644x 42cn403836343293.3% abundan t). One of the fiSR frequency spectra is shown in Fig. 63.T he frequencies of the satellites give estim ates of the nuclear h f param eters, which were used to find the LCRs. Figure 64 shows the Mu* precessional frequen­cies versus m agnetic field for H || < 100 > . The ob­served and pred icted positions for the two m ain Mu* frequencies, i.e. those for which there are no NN 29Si are given by the solid curves, where the m uon h f pa­ram eters are Ajj1 = -16.82 MHz and A ± = -92.59 MHz. From the locations of the LCRs [72.0(2) m T and 653.9(5) m T for 0=90° and 418.9(3) m T for 0=0°], one of which is shown in Fig. 65, we obtained 29Si h f pa­ram eters of Ajf = -137.5(1) MHz and A \ = -73.96(5) MHz, assum ing the nucleus lies on the < 111 > symme­try axis. Using these nuclear and m uon h f param eters, exact diagonalization of the Mu* spin H am iltonian in­cluding one NN 29Si gives the dashed curves of Fig. 64. The agreem ent between the observed satellite frequen­cies and those predicted from the LC R results, plus the absence of any unexplained lines for fields above about 5 m T, dem onstrate th a t the nucleus in question is on the sym m etry axis. T he m easurem ents of the satellite frequencies alone (open squares in Fig. 64) yielded less precise h f param eters and were not accu­rate enough to determ ine the sign of A" . However, these estim ates were essential in finding the LCRs. A t the lowest fields (below 5 m T ) and for 0=70.5° a few additional lines were observed which were separated from the m ain lines by <1 MHz. These can be ex­plained by 29Si a t a fu rther neighbour site w ith an effective isotropic 29Si param eter of —20 MHz. Wehave recently m easured the corresponding LCRs due to these more d istan t neighbours and established th a t they are indeed due to the six next nearest Si neigh­bours.The num ber of equivalent Si neighbours on the sym­m etry axis can be deduced from the to ta l am plitude of the satellite lines relative to th a t in the two m ain lines. In particu lar the ra tio between the to ta l am plitude in the satellite lines and m ain lines is n / / ( 1 — / ) , where n is the num ber of equivalent Si neighbours responsible for the sp litting and / is the isotopic abundance ofFIELD (m T)Fig. 65. The high-field level-crossing resonance for Mu* in silicon for those centres whose sym m etry axes are at 90° to the field. The resonance occurs at a field where the muon transition frequency is m atched to th a t of a 29 Si nearest neighbour.5729Si. The spectrum taken a t 23.5 m T (see Fig. 63) is the best for illustra ting th is since the broadening due to sm aller nhf in teractions is negligible (the m easured dam ping ra te is A=0.19 /is- 1 ) and yet the 29Si lines are well resolved from the m ain lines. For one or two equivalent neighbours, which are the only possibilities for neighbours on the sam e < 1 1 1 > axis, the ra tio of am plitudes is expected to be 0.0493 or 0.0986, respec­tively. T he m easured ratio , 0.109(8), confirms th a t the splittings arise from 29Si nuclei a t two equivalent neigh­bour sites on the sym m etry axis. T he am plitudes of the 29Si LCRs are also consistent w ith two equivalent neighbours.From the m easured 29Si h f param eters one can esti­m ate the s and p atom ic spin densities usingr/2a 2 = i(A |f + 2 A l ) / A {r (1)^ 2 = i ( 4 - ^ l ) / 4 ree (2)where free denotes the values for the free a tom are known negative. This yields s and p spin densities of t]2a 2=-|-0.0207 and f72/?2= + 0 .186 for each of the two Si neighbours. The two NNs therefore account for a to­ta l spin density of 0.413, leaving a substan tia l am ount on fu rther neighbours. Assum ing sp3 orb itals and six sites, the sm aller splittings seen below 5 m T would ac­count for a to ta l spin density of 0.10 , leaving a large p a rt still unobserved. T hus the spin density is signif­icantly delocalized. T he spin density on the NN nu­clei has considerably m ore p-character th an an sp3 hy­bridized orb ita l, as also found for Mu* in GaAs. This suggests a large relaxation of the these nuclei away from the bond centre, as predicted from structu re cal­culations on BC m uonium .T h ere are on ly tw o sites for th e m u o n co n s is ten t w ith the observed inversion sym m etry - the bond centre and the hexagonal site. (Note th a t the vacancy associated model is incom patible as is any model involving a single im purity.) Only the bond-centred model has predicted all of the qualita tive features of our observations and is supported by detailed s tru c tu re calculations. These re­sults establish beyond any reasonable doubt th a t Mu* in Si is in te rstitia l m uonium located a t the bond cen­tre. We conclude th a t the m ost stable site for atom ic hydrogen or m uonium in covalent sem iconductors is at, or close to , the bond centre. We predict th a t im planted protons will in troduce a deep electronic level probably in the gap between the top of the valenceband and b o t­tom of conduction band. In Si the unpaired electron wave function is considerably more delocalized th an in GaAs.Note added: Since w riting th is report Gordeev et al. from Leningrad have reported the observation of anom alous hydrogen in Si by p ro ton im plantation . Its electronic s truc tu re is alm ost identical to th a t pre­dicted from our results on Mu* in Si.E x p e r im e n t 371 M u o n iu m in m ice lles(D.C. Walker, UBC)Long-lived m uonium atom s are produced in wa­ter containing low concentrations of solutes to which micelles are added in these /uSR experim ents. For some solutes (ethyl form ate, t-bu tano l and 2-propanol) the ra te of reaction between m uonium and solute is micelle enhanced by four orders of m agnitude, bu t for some the enhancem ent is only about ten-fold (styrene, benzene and naphthalene) and for others there is no enhancem ent (m ethylcyanoacetate, N,N- dim ethylacetam ide and a-cyclodextrin). 2.-propanol is the solute which shows the largest m easured enhance­m ent so far, because it can be obtained sufficiently pure for > 104-fold changes in ra te to be observable by /iSR (techniques which require the spin relaxation to fall near to the m uon’s lifetime of 2 /is).Micelles are composed of the ordered am phiphlic molecules th a t form biological m em branes. One aspect of these studies is to explore the effect of m em brane boundaries on the kinetics of elem entary reactions of species such as m uonium . A particu larly interesting result has been found w ith acetone. This solute appar­ently has two reaction paths, one of which is enhanced much more th an the o ther by micelles. Acetone shows a M u-radical by “add ition” (observed using LCR-/tSR) in pure w ater bu t no t in the presence of micelles. Evi­dently, localization by micelles has altered the branch­ing ratio , thereby allowing us to exploit micelles into selecting one reaction channel over another.T he m ost im portan t role of micelles is their solu­bilization of w ater-insoluble organic m aterials. These can now be studied a t enhanced rates w ith w ater as the source of m uonium (in hydrocarbons m uonium is gen­erally too short-lived) and will perm it nearly unlim ited scope to the study of m uonium chemistry.M uonium is also being used here to em ulate the re­actions of its heavy isotope, hydrogen. T he la tte r can­not be studied itself in these system s because it reacts too rapidly (100 tim es faster th an m uonium ) w ith the hydrocarbon chains of the su rfac tan t molecules which form the micelles.58E x p e rim e n t 398//L C R sp ec tro sco p y o f free rad ica ls(P. W. Percival, Simon Fraser)The application of m uon level-crossing spectroscopy (//LC R ) to the study of free radicals has been a re­sounding success a t TR IU M F. T his new technique com plem ents conventional m uon spin ro ta tion (//SR) studies of m uonium -substitu ted radicals by providing inform ation on the hyperfine coupling of nuclei other th an the m uon. New areas of research have been opened up, not only on the isotope effects o f muon substitu tion , bu t also problem s of more general in ter­est in chemistry, where the m uon is a passive probe. Some exam ples are briefly sum m arized below. They indicate the o u tp u t o f more th an five weeks of highly productive beam tim e received by E xpt. 398 during the year.1) Previous studies of the m uonium cyclohexadienyl radical have been extended to the 13C labelled species, which was studied in dilute solution in cyclohexane. Figure 66 shows the //LC R spectrum in the field re­gion where the 13C resonances appear. There are four 13C resonances, corresponding to the four m agnetically inequivalent carbons in the radical:A (C 6) = -34.1(1) MHzA (C 6)A (C l) = A(C5) = 39.6(1) MHz A(C2) = A(C4) = -35.2(1) MHz5h h A(C3) = 54.0(1) MHzThe carbon hyperfine coupling constants are directly related to the unpaired electron spin d istribu tion , in­terest in which has m otivated m any (unsuccessful) a t­tem pts to determ ine these coupling constants by ESR spectroscopy. This study has been accepted for publi­cation in Chem ical Physics Letters.2) T he study of proton and m uon hyperfine coupling constants of the te rt-b u ty l radical (CH 3)2C C H 2Mu (described in the 1986 T R IU M F A nnual R eport) has been com pleted. In particu lar, m easurem ents of the m uon coupling were extended to the solid sta te , re­vealing a discontinuity in the tem pera tu re variation at the phase change (Fig. 67). In the liquid, the lowest energy p a th for m ethyl ro ta tion is though t to involve sim ultaneous inversion of the pyram idal carbon skele­ton. M ost likely, the inversion is inhibited in the solid.3) T he 13C hyperfine coupling constant of the trigo­nal carbon in te rt-b u ty l has been m easured as a func­tion of tem peratu re. P relim inary d a ta analysis sug­gests th a t the coupling passes through a m inim um asMAGNETIC FIELD (TESLA)Fig. 6 6 . P a rt of the /iLCR spectrum of ^C eH eM u.the tem pera tu re is raised, in keeping w ith a non-planar equilibrium configuration of the carbon skeleton.4) //LC R and /iSR m easurem ents of the m uonium ethyl radical MUCH2CH 2 have been m ade over a wide tem pera tu re range (20-150 K) in solid and liquid ethy­lene. This study parallels th a t of the te rt-b u ty l radical described in 2. above. T he prim ary aim is determ ina­tion of the barrier to ro ta tio n of the substitu ted m ethyl group. P relim inary analysis shows th a t the barrier is higher in ethyl th an in te rt-bu ty l, and there is no dis­continuity a t the phase change (Fig. 68).5) The study of MUCH2CH 2 also includes measure­m ents on gaseous sam ples of ethylene a t various pres­sure between 1 and 15 atm . T he //LC R spectra were as expected, bu t m ost surprising was the successful detec­tion of the radical by transverse field //SR (see example in Fig. 69). Previous experim ents by Dave G arner of TR IU M F in collaboration w ith Em il R oduner a t SIN were restric ted to pressures of 25 a tm and up. Since the m echanism of radical form ation was assum ed to be simple addition of a near therm al m uonium atom to an ethylene molecule, it was expected th a t a t low pres­sures the ra te of reaction would be too low for coherent precession of the m uon spins in the radical product.In addition to the in teresting question of the form a­tion m echanism, the gas-phase ethyl study also con­tribu ted valuable d a ta on spin relaxation in this rad­ical, and m otional correlation tim es were determ ined for each gas pressure. Spin relaxation d a ta have also been accum ulated for the isotopically labelled radicals M uCD 2C D 2 and M u13CH 213C H 2. These gas-phase radical studies were so successful th a t a comprehen­sive new proposal (E xpt. 500) was subm itted to the EEC a t the December m eeting. E xperim ent 398 will continue w ith the study of radicals in the condensed590 50 100 150 200 250 300 350Temperature / KFig. 67. Tem perature dependence of hyperfine frequencies in (CH3)2CCH2Mu.140-hfc/MHz120-100 -80-60-160-|-60--70» « > > ■A^(CH2Mu)-« A(CH2Mu)> Ap(CH2Mu)|A p(-CH2)— I------- 1-------- 1--------1--------1--------10 50 100 150 200 250 300Temperature / KFig. 68 . Tem perature dependence of hyperfine frequencies in MuCH2CH2.phases.6 ) D eta iled m e asu rem en ts have been m ade o f the /tL C R signal am p litu d e s o f th e tw o rad ica ls fo rm ed from pyrogallo l (1 ,2 ,3 -trihyd roxybenzene) in aqueous so lu tio n . T h e c o n c en tra tio n s s tu d ied were in th e mil- lim olar an d sub -m illim o lar range , co rrespond ing to rad ica l fo rm a tio n ra te s in th e 1 0 6 to 1 0 5 s - 1 range. C onven tiona l p S R is lim ited to rad ica ls fo rm ed on the picosecond tim e-sca le (assum ing m u o n iu m as p recu r­sor).7) S tu d y o f th e ^ L C R sp e c tra o f rad ica ls fo rm ed from th io p h en e has con tinued . T w o rad ica ls were clearly identified , as w as found earlier for fu ran . Fu- ra n w as th e n s tu d ied in d ilu te so lu tio n in cyclohexane,200 psig EtheneFrequency (MHz)Fig. 69. Fourier transform fiSR spectrum of gaseous MuCH2CH2.an d it was found th a t th e re la tiv e rad ic a l yields were q u ite d ifferent from those in th e p u re liquid . A n in ­te re s tin g possib ility , w o rth y o f fu rth e r ex p lo ra tio n , is th a t th e tw o rad ica ls are fo rm ed from d ifferent p re­cursors. T h e question o f rad ic a l fo rm a tio n w as also pu rsu ed w ith b en zo th io p h en e . A w ea lth o f signals w as d e tec ted , b o th w ith conven tional /iS R an d w ith LC R . So far, six d is tin c t rad ica ls have been te n ta tiv e ly iden­tified.E x p e r im e n t 420R ea ctio n s o f m u on iu m w ith h a logen(I. Reid, UBC)T h e m easu rem en t o f th e r a te co n s ta n ts o f m uon ium reac tio n w ith th e halogens F 2, C I2 , an d B r2 in the m id-seventies a t th e L aw rence Berkeley Lab (LBL) an d T R IU M F w as a p ioneering w ork in th e ap p lica­tio n o f /iS R to chem ical k ine tics. T hose d a ta spanned a lim ited te m p e ra tu re ran g e an d w ere o f lim ited pre­cision due to th e p rim itiv e s ta te o f th e /zSR facilities available a t th e tim e . N onetheless, th is w ork spaw ned considerab le th e o re tic a l a t te n t io n because , n ex t to th e classic H 3 system , th e hydrogen iso tope-halogen reac­tio n s are th e s im p lest a tom -m olecu le reac tions , an d ki­ne tic iso tope effects have alw ays p layed a cen tra l role in e lu c id a tin g th e chem ical dynam ics. In th e in te rv en ­ing decade new co m p u ta tio n a l techn iques have been devised to ca lcu la te rea c tio n r a te co n s tan ts , m ost no­ta b ly th e v a ria tio n a l tr a n s itio n s ta te th e o ry o f T ru h la r an d co-w orkers. In ad d itio n , a new ab in itio p o te n tia l60energy surface has been calculated for the B r2 reac­tion, and new experim ental d a ta are available on the H analogue reactions. These developm ents coupled w ith the great im provem ents in pSR facilities m oti­vated E xpt. 420 to extend the precision and tem pera­tu re range of these m easurem ents.The new d a ta are displayed in Fig. 70, along w ith the original d a ta and some recent theoretical compu­ta tio n s due to T ruh lar and co-workers. The agreem ent between the two d a ta sets is excellent except in the case of brom ine where there is about 40% difference. This discrepancy is explained by the system atic error in tro­duced to the LBL d a ta by the use of published vapour pressure curves (which were subject to a wide varia­tion) to com pute the brom ine concentration, whereas a precision capacitance m anom eter was employed in the present experim ent to m easure the brom ine concentra­tion directly. T he negative slope and negative acti­vation energy for the brom ine reaction is unexpected and as yet unexplained - only room tem peratu re com­pu ta tions or d a ta for the analogous H atom reaction are available. Possibly, the brom ine reaction has zero barrier and a strongly a ttrac tiv e potential.T he theoretical curve shown in the figure for flu­orine is in good agreem ent w ith the data ; both ex­perim ent and theory show strong quantum tunnelling as evidenced by the curvature in the A rrhenius plots. The poorer agreem ent between theory and experim ent for the chlorine and brom ine reactions probably arisesTem perature (K) 222 167 133Br2111 95Mu +theorypresent experim ent (E420) ' old experim ent (LBL)old experim ent (E35) present exper iment (E420)-i1 -Mu + F2theoryold experim ent (E35) present experim ent (E420)theory: S teckle r, T ruhlar, G arre tt, Int. J. Quantum Chem., 20 (1986) 495.0.21.5 3.0 4.5 6.0 7.5 9.01000/T em pera ture (K)10.5Fig. 70. Arrhenius plot comparing theoretical, old and new experim ental ra te constants for Mu + halogen reactions.from deficiencies in the po ten tia l energy surfaces used in the com putations. T ruhlar and co-workers (M in­nesota) are currently a ttem p tin g to improve the com­pu ta tions on these reactions.I t was intended to ob tain d a ta a t tem peratu res up to 500 K b u t, contrary to advice we obtained, the target vessel reacted w ith the halogens a t elevated tem pera­tures. T his led to an extensive research program m e to develop a ta rg e t vessel which is inert to the extremely reactive halogens a t elevated tem pera tu res and quan­titive assay techniques to m onitor the halogen concen­tra tion . W hile nickel is widely used to contain fluorine, /zSR restric ts us to the use of nonm agnetic m aterials. After much experim entation, copper electroplated with nickel appears to be a satisfactory m aterial. A target vessel is now under construction and, if off-line tests prove satisfactory, it will be used to extend the mea­surem ents to 500 K during beam in February.A publication is in p reparation .E xp er im en t 440M u on ca ta ly zed fu sion in H D an d H 2 + D 2 gaseou s m ix tu res (K . A n io l, C alifornia S ta te L A )In December we ran our m uon catalyzed fusion mea­surem ent on M13. This is the first tim e th a t such a m easurem ent has been perform ed on th a t channel. T he incident m uon flux a t 61 M eV /c is large enough to make the experim ent possible even in spite of the trem endous flux of electrons and pions. Hardware se­lection of the m uons was accomplished through a com­bination of scin tillator threshold cuts and fast coinci­dence tim ing relative to the capacitive probe. Further work on the channel, such as use of the m id-plane ab­sorber, m ight enhance the usefulness of M13 for nega­tive muons.In th is particu lar set-up we employed a new gas ta r­get and different gases and substan tia lly different elec­tronics as com pared to our earlier runs on M20. We measured H2+ D 2, H 2+ D 2+H D , H2+ H D and pure H2 gases. O ur on-line results for the gam m a-ray yield for the fusion p + dp —*-3He-py + p is in agreem ent with the earlier tem pera tu re dependence th a t we saw in Expt. 230. The off-line analysis will be done a t Cali­fornia S ta te U niversity in Los Angeles.E x p e rim en t 447L evel-crossing reson an ce o f m u on iu m radicals in m ice lles(K. Venkateswaran, TRIUMF)T he developm ent of the m uon level crossing tech­nique (LCR) coupled w ith the effects of micelles on m uonium reaction rates in solution prom pted this61study of free-radical reactions in micelles.The first d a ta for th is experim ent were taken on channel M15 in June. Radicals form ed by m uonium (M u) addition reaction w ith solutes localized in mi­celles were observed for the first tim e. These solutes included acrylam ide, benzene and styrene in CTAB micelle. F igure 71 shows the LCR spectra a t a [so­lute]: [micelle] of 3:1 w ith the [micelle] = 6.0 x 10-5 M.A cetone was studied in order th a t it can be used as a co-solute w ith benzene, to determ ine where Mu prefers to locate in a micelle [the m icellar surface (Stern layer) or the core]. A cetone was chosen also because enhance­m ent of the M u decay ra te was seen (E xpt. 371) when it was localized in the micelle. Its LCR position (m ethyl p ro ton resonance) has already been determ ined [Hem­m ing et al., Chem . Phys. L ett. 128, 100 (1986)]. Q uite unexpectedly, no Mu radical was observed even a t lo­cal concentrations of 0.1 M acetone in the micelle. In order to test w hether the Mu radical forms in a hydro­carbon environm ent (sim ilar to the m icellar interior), a 30% acetone/n-hexane m ixture was studied. Fig­ure 63 shows th a t, indeed, the radical does form in m ixtures w ith n-hexane as well as w ater. Unlike H atom s which abstrac ts a hydrogen from acetone Mu adds to the oxygen on the carbonyl. B ut when local­ized a t micelles the (CH a)2 CO Mu radical form ation is probably superseded by a reaction in which Mu ab­strac ts a H from the m ethyl group of acetone to give MuH (not observable by LCR).Shifts in the resonance positions [Figs. 72(a)-(c)] of +280 G in w ater and —115 G in hexane can be a t­trib u ted to a solvent effect on the m uon-electron hy­perfine in teraction. The higher the degree of hydrogen bonding, the lower is the hyperfine coupling constant An, as restriction of free ro ta tion of the O-M u bond about the C-C axis occurs. Using A ^ = 22.0 MHz [Hill et al., J . C. S. Faraday Trans. 1,81, 43 (1985)] we calculate the proton hyperfine coupling constant A jfp in w ater to be 55.5 MHz. T his value of A h /3 is very close to th a t ob tained in neat acetone [Heming et al., Chem . Phys. L ett. 128 , 100 (1986)], showing th a t there is no solvent effect on th is param eter. We have determ ined a value of 29.4 MHz for A ^ for acetone in hexane solution.We have shown th a t radical yields (Pr ) as deter­m ined from LCR linew idths and am plitudes to be in excellent agreem ent w ith the values obtained from con­ventional T F -p S R m easurem ents. D etails on this ap­plication of the LCR technique can be seen in a forth­coming publication.E x p e r im e n t 449M u on iu m an d m u on s ta te s v ia r f reson an ce(S.R. Kreitzman, UBC)Experim ent 449 is devoted to the developm ent of rf resonance techniques for the study of muon spin ro ta tion /re laxation /resonance . Progress to date can be conveniently categorized by considering param ag­netic m uonium -bearing system s ap art from diam ag­netic m uon sta tes. Param agnetic m uonium states are characterized by a bound m uon-electron “light hydrogen”-like s ta te th a t in teracts strongly w ith neigh­bouring nuclei th a t have nonzero m agnetic moments. T he m ajor in teraction is usually the electron-nuclear hyperfine in teraction (NHI), which can easily range from 10 to 300 MHz. Conversely diam agnetic muon sta tes behave like bare muons which experience dipolar interactions from other nuclei or from localized elec­trons residing on the host nuclei. In the context of th is report only nonm agnetic hosts are considered and the interaction streng th between the m uon and its dia­m agnetic host never exceeds 1 MHz. In a ttem pting to develop /zSR rf techniques we have focused on sys­tem s th a t clearly fall into one or the o ther of the above categories.Param agnetic system sTw o canonical param agnetic system s have been in­vestigated. T he first is a test system in which one finds more or less free vacuum-like m uonium since the host, fused Si0 2 , has a very sm all n a tu ra l abundance of nuclei w ith spin. The second case is th a t of the m uonated free radical CgHg-Mu. This system displays a weak hyperfine coupling between the unpaired elec­tron and the muon and strong NHI w ith the nuclei in the molecule. Ordinarily, strong NHI would prevent any inform ation about the details of th is coupling from being experim entally accessible. However, for the case of weak muon hyperfine coupling, an LCR experim ent can yield the basic NH interactions. In those cases where the muon HI is large, the LCR technique is no longer feasible (since the relevant transitions occur in too high afield) and the experim enter, in the past, had to accept th is lack of inform ation about the NHI. The m uonium rf resonance technique is designed to circum­vent this situation ; it is the analog of “wide-line” ESR, bu t carried ou t in low fields. T he d a ta presented in the CgH6-M u system sim ulates well the s ta te of affairs th a t one expects to find in “norm al m ounium ” type systems w ith strong NH interactions.M uonium rf resonance is fundam entally stra igh tfor­ward. T he experim ental configuration is th a t of a longitudinal field /iSR study w ith the m uon’s initial polarization parallel to the field. An rf field is then62ACHYLAMIDE IN CTABLon g itu d ina l Magnetic Field (Gauss)BENZENE IN CTABL o n g itu d ina l Magnetic Field (Gauss)STYNKNE IN CTABLo n g itu d in a l Magnetic Field (Gauss)Fig. 71. LCR spectra of acrylamide, benzene and styrene in CTAB micelle a t [mic] = 6.0 x lO - 5 M with three solutes per micelle on average.SOX A CTTONE/n -HZXAXT600 600 1000 1200 1400 1600 1600 2000 2200 2400ACTTONE NEAT600 600 1000 1200 1400 1600 1600 2000 2200 2400SOX ACTTONE/TATBRLongitudinal Magnetic Field (Gauss)Fig. 72. LCR spectra of (a) 30% acetone/n-hexane, (b) neat acetone and (c) 30% acetone in water.63Fused Quartz RF resonance in 9 GaussRF Frequency in KHz Fig. 73. The effect of rf power broadening on the degener­ate Mu trip le t transition in low fields.used to induce m agnetic transitions between sta tes whose field-dependent sp litting is equal to th a t of the applied rf frequency. These transitions are detected as a loss of asym m etry in the direction of initial polariza­tion. By sweeping the rf frequency one can m ap out the absorption spectrum of the system . Such a spectrum is shown in Fig. 73 for fused quartz in an external field of 9 G. T he three superposed figures show the effects of increased rf power on the linew idth. A t higher fields the spectrum of vacuum Mu becomes more complex w ith the single low frequency line sp litting into two. These two “trip le t” lines are shown in Fig. 74. TheFused Quartz Mu RF resonance at 150 GaussR F Fr eq ( M H z )Fig. 74. The two normal m uonium trip le t transitions at 150 G.C6H6 RF s c a n 90 G a u s sRF Frequency (KHz)Fig. 75. rf spectra of CeH6-Mu in 90 G between 20- 145 MHz. Both m ajor lines are basically 1 - 2 transitions but with the direction of the “dom inating” proton reversed.225 MHz bandw idth of the power amplifier is the cause of the dim inished intensity above th a t frequency.T urning now to the Ce6H6-M u data , a 20-145 MHz spectrum in 90 G is shown in Fig. 75. The spectrum is typical of a M u system coupled to several nuclei through NH interactions w ith one of the coupling con­stan ts dom inating. T he sp litting of the two m ajor line groupings is approxim ately one-half the hyperfine cou­pling of the dom inating nucleus, while the fine struc­tu re yields inform ation on the sm aller NH param eters. Normal m uonium system s, for exam ple those occurring in alkali-halide hosts, should also be very am enable to this technique along the sym m etry directions, and this is indeed foreseen to be the m ajo r application of this type of resonance.Diam agnetic system^S R in diam agnetic system s w ithin a host contain­ing several nuclei and and m uon diffusion is quite often experim entally difficult to unravel. T he vast array of experim ental tools available to N M R have not been available for the pS R experim entalist. O ur work in resonance applications for diam agnetic system s is di­rected predom inantly a t two basic questions. Is the muon moving (and if so how fast), and w hat nuclei contribute to the local field experienced by the muon (im plying detailed m uon site inform ation). We have addressed the first problem by developing a m uon spin echo (M USE) spectrom eter. T he first SE spectrum we obtained is shown in Fig. 76. Once again the experi­m ental configuration a t 0 is th a t of a LF geometry w ith the in itia l polarization along the field. A 90°64LaF3 po lyxta l 9 0 x - 1 .5 r - 180y Spin Echo Muon Ind irec t Echo in LaF3 via F lourine RF Pulse90x cen terQJEE>NV) ~ 1 atm . The only exceptions to th is s ta tem en t were in Xe and CCI4, both heavy (and “spherical” ) gases which con­com itantly are very inefficient m oderators for slowing down the Mu atom , thus giving rise to an enhanced probability for depolarization [see Senba et al., Hyp. Int. 32, 795 (1986)].This la tte r topic was the focus of Expt. 185, in which we looked a t the to ta l polarization in Xe at pressures up to 6 a tm , and la ter, as p a rt of E xpt. 450, a t pres­sures up to 60 atm . A t the present stage of the da ta analysis it appears th a t there is a true “missing frac­tion” of polarization in Xe, w ith Ptot = 0.8 only. The reason(s) for th is are no t clear bu t may indicate the form ation of a M u.Xe Van-der-W alls type of complex. This m ight also explain the large missing fraction seen by Kiefl et a l in the condensed phase [J. Chem. Phys. 74, 308 (1981)].T he s itua tion described above for gases is in marked65contrast w ith th a t in the condensed phase, where miss­ing fractions of ~20% are invariably seen and moreover P (D ) is typically about 0.6 vs. ~0 .2 in the gas, w ith the Mu fractions about 0.8 in the gas phase a t pres­sures near 1 a tm . T his s itua tion prom pted our in ter­est in investigating the d istribu tion of muon polariza­tion in gases a t their critical densities, the subject of Expt. 450. This experim ent is being carried out using surface muons a t pressures up to 60 a tm and up to ~200 a tm using the backw ard muon beam on M20A. In terest has been focused on C 2H6 to date, since this has a critical tem pera tu re of only 32 C and a criti­cal pressure of only 48.2 atm . A t tem peratu res above Tc (it is not possible to liquefy the gas a t this condi­tion) there is a very sm ooth change of both P ( M u ) and P (D ) w ith increasing pressure, the la tte r increasing bu t the form er decreasing. T his kind of behaviour sug­gests th a t reactive collisions during the slowing-down process (hot a tom chem istry) are m ainly responsible for the yields seen. R adiation-induced spur encoun­ters may be playing then a ra th e r m inor role. On the o ther hand, there are indications th a t there is a de­crease in P tot w ith increasing pressure, which could be explained by a spur model of spin exchange encoun­ters. There has long been a continuing debate over the relative m erits o f ho t a tom and spur encounters in the condensed phase [see, for exam ple, W alker Muon and m uonium chemistry (CUP, Cam bridge, 1984) and references to work of Percival et al. contained therein].In a recent run on M15 we explored ehtane a t tem ­peratu res and pressures both below and above TC,P C and found essentially no difference in the am ount of Mu or of m uons in D environm ents seen. W hile pre­liminary, th is result strongly suggests th a t there is no phase difference in m easured values of P t ot and again supports a “hot m odel” of m uonium form ation. This result and certain ly the in terp re ta tion , though, need confirm ation from studies in o ther gases. Such work is under way, particu larly in XCe, where the afore­m entioned missing fraction in the gas phase a t high pressures is of considerable interest.E xp er im en t 461M uon sp in ro ta tio n s tu d ie s o f d ioxygen an d e th y ­lene on silica po w d er (R.F. Marzke, Arizona State)T he goal of th is experim ent is to study the in ter­action of m uonium w ith molecules of gases adsorbed onto the surface of finely divided silica (Si0 2 ) powder, a common cata lyst-supporting m aterial. In E xpt. 391 (concluded last year) it was found th a t a new type of silica powder, then under study by M uSR for the first tim e, exhibited negligible Mu relaxation over the tem ­pera tu re range 20-300 K, after gentle heating to re­move physisorbed w ater. This behaviour was in sharp contrast to th a t of all previously used silica powders, and w ith the availability of such m agnetically “clean” m ateria l M uSR studies were undertaken th is year with sm all am ounts of two adsorbates on the silica surface, oxygen and ethylene. These represent the two m ain types of Mu in teraction encountered in the gas phase, nam ely spin exchange and chemical reaction. It was anticipated th a t inform ation about diffusion of Mu on or near the silica surface would be obtained especially from the oxygen studies.Results for Mu relaxation by O 2 adsorbed onto ex­trem ely pure, high-surface-area SiC>2 are indicated in Fig. 78, for the tem pera tu re range 20-320 K and at 13 ppm oxygen coverage. T he dependence of the rates upon O 2 coverage a t fixed tem pera tu re appears to be linear, as expected. However, the tem pera tu re depen­dence of the rates a t fixed concentrations also appears to be linear between 208 and 100 K. T his tem perature dependence is a t variance w ith those of m ost studies of the scattering of a mobile probe spin (such as Mu) by dilute param agnetic im purities in solids, liquids and gases. In particu lar, the gas-phase results of Mikula, G arner and Flem ing [J. Chem . Phys. 75, 5362 (1981)], while not entirely inconsistent w ith a linear tem pera­tu re dependence, appear to support the T 1/ 2 behaviour arising from expected velocity-independent O 2 sca tte r­ing. T hus it appears from our present work th a t the scattering of Mu by O 2 on the silica surface is veloc­ity dependent. I t is also clear th a t physisorbed O 2 is strongly param agnetic. Corollary m agnetic suscepti­b ility studies are planned to fu rther investigate this la tte r observation are planned.Temperature (K)Fig. 78. Relaxation ra te of muonium in EM O ptipur silica, w ith dioxygen physisorbed at 13 ppm coverage.6 6E x p e r im e n t 469f iS K s tu d y o f a n t i f e r ro m a g n e t is m a n d h ig h - t e m p e r a tu r e s u p e rc o n d u c t iv i ty(I.E . Brewer, UBC)T he recent discovery of superconductiv ity a t the anom alously high tem pera tu re of Tc « 90 K in the perovskite Y B a2C u3 0 r (6.9 < x < 7.0) has stim u­lated theorists to explore new m echanism s for super­conductivity. Several such theories involve frustra ted antiferrom agnetic couplings between copper a n d /o r oxygen ions in the C u 0 2 planes th a t these m aterials have in com m on w ith the slightly lower-Tc perovskite Lai.85Sro.i5Cu04-« • It was therefore in teresting to learn, bo th from neutron diffraction and from ^t+ SR and susceptibility m easurem ents, th a t the (insulating) paren t com pound L a2C u0 4 _{ exhibits antiferrom ag­netic (A FM ) order below a Neel tem pera tu re TN th a t depends critically upon the oxygen deficiency 6 (TV increases w ith increasing 6), lan thanum stoichiom etry a n d /o r doping of Sr for La. For instance, we have found th a t replacing L a2 by L a1.9sSr0.02 reduces Tjy from around 250 K to less th an 15 K.Similar AFM ordering was discovered in the oxygen- deficient Y B a2C u3 0 x m ateria ls (insulating for x < 6.3) by /i+SR m easurem ents a t BOOM and TR IU M F [N ish idaet al., Jpn . J . Appl. Phys. 26 , L1856 (1987)], bu t it has proved difficult to detect the AFM order by either susceptibility or neutron diffraction. One of the im portan t results from E xpt. 469 in 1987 was a careful study of the com petition between antiferrom agnetism and superconductiv ity in Y B a2C u3 0 a; as a function of x. In particu lar we were able to show th a t the absence of a susceptibility cusp is due to the strong dependence of TV upon x, which is inevitably heterogeneous in any sample. The weakness of the AFM neutron diffraction Bragg peaks is probably due to the sm all m om ent per Cu ion com bined w ith a relatively short range of the AFM order.T he sam ples used in these m easurem ents were sin­tered powders of Y B a2C u3Ox prepared a t the Uni­versity of B ritish C olum bia (by W .N. H ardy from Physics, A .C .D . C haklader from M etallurgy and their co-workers) by two ra th e r different m ethods. In the “quench” m ethod, sam ples were heated in controlled atm ospheres of oxygen a n d /o r argon and allowed to equilibrate to the oxygen content determ ined by ther- m ogravim etric analysis (TG A ) on test samples, using as a reference neutron diffraction results from Argonne which show th a t as the oxygen content x is decreased oxygen atom s are selectively removed first from the CuO “chains” , leaving the C u 0 2 “planes” essentially in tac t down to x — 6.0 where the “chains” are fully de­oxygenated. T he sam ples were then dropped directlyinto liquid nitrogen and tran sp o rted under argon to TR IU M F for /i+ SR experim ents. In the “slow anneal” m ethod, a “m other b a tch” of Y B a2C u3 0 a, powder was pressed into discs and annealed in pure 0 2 a t 450°C for 24 h, a procedure which produces fully oxygenated sam ples w ith x = 6.95 ± 0.05 (where the uncertain ty is not in the reproducibility of the endpoint, bu t in its absolute value, which has been reported in the lit­eratu re to have fixed values ranging between 6.9 and7). T he requisite am ount of oxygen was then removed from each sam ple a t tem peratu res between 420° C and 460°C using a helium-cooled wand in a closed system. Next each sam ple was held a t a constant tem perature of fts420°C for 24 h in order to allow any gradients in x to be dissipated. Finally the rem aining 0 2 was suddenly removed from the cham ber and the sample cooled in a few seconds to room tem perature. The re­su ltan t slow-annealed sam ples should have a far more homogeneous oxygen d istribu tion th an the quenched samples. I t is im portan t to note th a t, while the ab­solute x values are uncertain by as much as 0.05, the relative x values in such a series of sam ples are known to b e tte r th an 0.01.As observed earlier, the m ost oxygen-deficient sam ­ples (2: ss 6.0) revealed a strong Z F-/i+SR precession signal in the AFM sta te , corresponding to a local field B\oc ranging from about 300 G a t low tem peratures down to about 150 G ju s t below the m ean TV of about 360 K. The sm all m agnitude of 5 ioc com pared to other oxide insulators indicates a sm all m om ent per Cu ion - even sm aller th an in La2C u0 4 _$ - and is in itself an im portan t result. However, the m ain focus of the present experim ent was a careful determ ination of the m agnetic ordering tem pera tu re.This is seen m ost easily from T F -/i+ S R experim ents in low applied field: if B ext < Bioc (as for the 84 G field used in these m easurem ents) then the am plitude of the precession signal a t the frequency corresponding to the applied field reflects only th a t fraction of the sam ple which has not ordered m agnetically - i.e., the param agnetic fraction. Any m uon in an AFM region “sees” a com pletely different local field, upon which the applied field is in effect a random pertu rbation . T he easily m easured TF-/Z+SR precession asym m etry is thus a convenient, quantita tive, norm aliable mea­sure of the param agnetic fraction. This is illustrated in Fig. 79, which shows T F -/i+ S R tim e spectra for T > TV (circles) and for T < TV (crosses). From such m easurem ents are ex tracted the param agnetic fraction as a function of tem pera tu re for various samples with different x, exam ples of which are displayed in Fig. 80.T he onset of AFM order is accom panied in each case by a small negative frequency shift (6u^/i/0 ~ —1%) and an increased relaxation ra te (T2-1 ~ 0.1 —0.3/is-1 )67YBa,CU,0* in Weak TFEE>>to^ 5005.9 6.0 6.1 6.2 6.3 6.4 6.5, 6.6Oxygen Form ula Content (x)Fig. 81. Dependence of the mean Neel tem perature Tn upon the oxygen content x in Y BajC usO *. Squares denote quenched samples; circles denote slow-annealed samples. The slow-annealed samples w ith x = 6.348 and x = 6.400 also have sharp superconducting transitions at Tc = 25 K and Tc — 32 K, respectively.1 1 —^' ------ r v --- ' ... T... ' *b-- — $—$- ♦-• + - B -.... .1— . L 1 1 A . . .and then ordered m agnetically below Tn = 10 K and Tjv = 5 K, respectively. T he p + SR “signatures” of the SC and AFM transitions are easily distinguished, the former giving huge negative frequency shifts and re­laxation rates while the la tte r causes a T F asym m etry loss. T he onset of AFM order in the presence of SC in these two sam ples is accom panied by a dram atic less­ening of the large negative SC frequency shift, which suggests th a t m ateria l which was SC relinquishes its superconductivity to become AFM .The m ost in teresting em pirical question, of course, is w hether these sam ples a t the borderline between AFM and SC are merely heterogeneous, so th a t part of the sam ple can be SC while another p a rt ig AFM, or w hether the sam e m ateria l can be sim ultaneously AFM and SC (as is certainly the case for analogous m aterials containing m agnetic rare earths, bu t would be surprising for a system in which both AFM and SC are believed to be m ediated by the sam e electrons!) or whether, as we suspect, a region which is SC a t 20 K “tu rns off” its superconductiv ity to become AFM at 2.5 K. A more detailed analysis using «^+ SR may be able to resolve th is question unambiguously.69T H E O R E T I C A L P R O G R A MIn tro d u ctio nT he Theory group a t T R IU M F exists to provide, first, a focus for theoretical research and, second, a group of active researchers who are interested in the physics relevant to the present experim ental program and the proposed KAON factory. As befits a labora­tory w ith as wide a range of activities as TR IU M F the in terests of the Theory group are quite broad, includ­ing /iSR, proton-nucleus interactions, meson-nucleus in teractions, m eson-photon-baryon reactions, nucleon structu re , la ttice gauge calculations, grand unification and weak in teractions. P a rt of th is research involves working directly w ith the experim entalist on particu ­lar experim ents and the developm ent of new facilities; p a rt w ith m ore general physical understanding; and p a rt w ith form al theoretical developments. I t is th is b readth of in terests th a t allows the Theory group to be of benefit to T R IU M F in both the short and long term s.The Theory group has four perm anent staff m em ­bers: H .W Fearing (group leader), B.K. Jennings, J .N . Ng and R.M . Woloshyn. In addition we have re­search associates and long-term visitors. During this year our research associates have been G. Belanger (to Septem ber), P. B lunden, M. B utler (from Septem ber), M. Celio (to Septem ber), T . D raper, C. Geng (from Decem ber), M .J. Iqbal (from M ay), E .J. K im (from December) and R. W ittm an . O ur long-term visitors have been X .D . Jiang (from Septem ber), J .A . Niskanen (from Septem ber, jo in tly w ith UBC) and F. S tancu (to April). Five g raduate students, G. C outure, S. Fortin, J . Kopac, G. Pari, and R. W orkm an, are being su­pervised by Theory group members. In teractions and collaborations are also m aintained w ith theorists from the nearby universities.In addition to the ir research program s the theorists take an active p a rt in laboratory com m ittees includ­ing: the Long-Range P lanning C om m ittee (B.K. Jen­nings), the C om puter Facilities a t TR IU M F (CFAT) C om m ittee (R .M . W oloshyn), the ad hoc Com m ittee on Particle Physics a t T R IU M F (J.N . Ng), the Kaon Factory Steering Com m ittee (J.N . N g),and the Senior Prom otion Com m ittee (H .W . Fearing). O rganization of the T R IU M F sem inars is also handled by the T he­ory group (R .M . W oloshyn and P. Blunden). Three of the T R IU M F theorists have adjunct professor s ta ­tus a t the associated universities, J .N . Ng a t the Uni­versity of British Colum bia and B.K. Jennings and R.M . W oloshyn a t Simon Fraser University. Two mem­bers of the Theory group have also been involved with teaching: B.K. Jennings a t the U niversity of British C olum bia and J.N . Ng a t the U niversity of M anitobaand three, H.W . Fearing, B.K. Jennings and J.N . Ng, are supervising g raduate studen ts a t the University of British Columbia.The sem inar program and the sum m er theoretical visitors program have brought a large num ber of vis­iting theorists to T R IU M F. Following is a list of such visitors for the year:P. Alons R. A rndt P. A sthana N. Auerbach W . Bentz M. Beyer L. Brekke A. Brown H.C. C hiangE.D. Cooper W . Dickhoff J . Eisenberg R. FiebigA. Gal H. H arari P. Herczeg J . Hewett C. Horowitz S. K ahanaF. K hanna Y. Kim S. K um ano V. Kuzmin C. LamAs usual the Theory group has been very active and we briefly describe below specific research projects un­dertaken during the year.N u clear stru c tu reR ela tiv is tic H a r tre e -F o c k fo r fin ite nuclei (P.G. Blunden, M.J. Iqbal)R elativistic Hartree-Fock calculations have been per­formed for finite nuclei, w ith an in teraction based on the exchange of < r , u j , p and -it mesons. An extensive com puter code has been developed which solves the coupled integro-differential equations for the baryon and meson fields numerically. The meson coupling constants are ad justed to sa tu ra te nuclear m atte r at the em pircal binding energy and density. Reasonable results for the binding energies, densities, rm s radii and single-particle energies of finite nuclei are then ob­tained. We are now investigating in detail the use of re­alistic one-boson-exchange po ten tia ls and the effect of nuclear correlations on the H artree-Fock ground state.F. Lehar D. Lichtenberg T . Londergren R. M alaney O. Maxwell B. M cKellarD. M urdockE. OsetJ . P arm ento la J . P asupa thy M. RhoA.S. R inat T . Rizzo J .R . Shepard R. Sm ithN. de Takacsy M .J. Vincente-Vacas S. W allace W . W ilcoxB. W ildenthal L. W iletsD. W ilkinson A. W illiam s70T h e r e la t iv is t ic r a n d o m p h a s e a p p ro x im a tio n(P.G . Blunden; P. McCorquodale, SFU)We have exam ined the collective modes of closed shell nuclei in a random phase approxim ation based on the fully relativ istic H artree-Fock ground s ta te . W ith a residual in teraction fit to the bulk properties of nu­clear m atte r, and used to determ ine the wave function of the ground s ta te system , reasonable results for the negative parity spectra of light nuclei are obtained.P r o to n in d u ced reaction s and sca tter in gR e la t iv is t ic tw o -b o d y p r o p a g a to rs(E.D. Cooper, McGill; B .K . Jennings)One of the problem s th a t has plagued relativistic calculation (nucleon-nucleon, nucleon-nucleus, pion- nucleon) is the lack of a good two-body propagator. The propagators usually used have such defects as not giving the correct p ropagator in the nonrelativis­tic lim it, no t giving the correct lim it when one of the masses is large or not trea ting two identical particles equivalently. We have recently developed a relativis­tic p ropagator which cures these problem s. S tarting from ju s t about any relativ istic two-body propagator ours is ob tained by the elim ination of all short-range structu re . As noted previously [Cooper and Jennings, Nucl. Phys. A 4 5 8 , 717 (1986)] th is procedure gives the exact result for a one-body problem . This new propagator has m any desirable features. I t cures the problem s m entioned above as well as helping keep the soft pion theorem s in 7r-nucleon scattering . Since it has no short-range s tru c tu re it is also expected to be valid for com posite objects like nucleons.R a d ia tiv e m u o n c a p tu r e in n u c le i in a r e la t iv is t ic m e a n fie ld th e o ry(H .W . Fearing; G.E. Walker, Indiana University)Much a tten tio n has been directed recently to rel­ativistic descriptions of nuclear reactions and to so- called Dirac effects. Such discussions are often fram ed in term s of a relativ istic m ean field theory in which a nucleon is presum ed to move under the influence of very strong effective scalar and vector potentials gen­erated by the m ean field of the o ther nucleons. In an infinite m edium the wave functions of such a system are ju s t the usual plane wave solutions of the Dirac equation except th a t the free nucleon mass m is re­placed by a sm aller effective m ass m * . T hus effort has been devoted to looking for effects of this m* in a va­riety of nuclear processes, in electron scattering and in ordinary nonradiative m uon capture.R adiative m uon capture has as yet no t been exam ­ined, though there are two effects which suggest th a t m* effects m ight be im portan t there. In the first place it is known from nonrelativistic calculations th a t the im portan t sensitivity to the weak in teraction induced pseudoscalar coupling gp comes via term s 0 ( p / m ) so th a t replacing m by m* m ight enhance th is sensitivity. A second, and probably com peting effect, arises be­cause the usual G oldberger-Treim an relation predicts th a t gp is proportional to m.To investigate these effects we are engaged in a pre­lim inary calculation of the capture process in an infi­n ite nuclear m edium . T hus the usual relativistic ra­diative m uon capture opera to r for the proton [Fearing, Phys. Rev. C 21, 1951 (1980)] is being evaluated in a Fermi gas model using the plane wave sta tes obtained in the relativistic m ean field theory. If a strong sen­sitivity to m* is found, the in tention is to extend the calculation to m ore realistic nuclear wave functions ap­propriate for finite nuclei.N u c le a r m e d iu m effec ts o n iso v e c to r s p in flip a n d n o n -sp in f lip n u c le o n -n u c le u s in te r a c t io n (P.G . Blunden, M .J. Iqbal)We considered a model of isovector spin flip (VaT) and non-spin flip (VT) in teractions based on one- and two-pion exchange. In the fram ework of this model we calculated the effects of Pauli blocking and in-m edium scalar and vector interactions on VT and VaT. It was shown th a t the density dependence of VT is stronger th an th a t of VaT, leading to an increase of the ratio |R < tt(0 )/It(0 )| w ith increasing density, as observed ex­perim entally . T his is the first work to exam ine the effect of scalar and vector interactions on VaT and VT.Iso v e c to r D ira c o p tic a l p o te n t ia ls a n d n u c leo n c h a rg e e x c h a n g e r e a c tio n(M .J. Iqbal; J.I.Johannson, S. Hama, H. Sherif, Alberta)T he isovector p a rt of Dirac optical poten tia l for nucleon-nucleus scattering was calculated using a fold­ing model approach based on the relativ istic N N T- m atrix . We explicitly took into account the exchange and Pauli-blocking effects. We have com pared these potentials w ith those obtained in the RIA. These po­tentials are then used in a relativ istic DW BA calcula­tion of the am plitudes for the charge exchange (p, n) reaction leading to the isobaric analog sta tes in nuclei. Good agreem ent is obtained w ith the cross section and analysing power d a ta for reactions on 48Ca, 90Zr and 208Pb nuclei.S tu d y o f th e (p , dx) r e a c t io n o n n u c le i(M .J. Iqbal; J. Niskanen, T RIU M F -U BC )Study of the proton-induced pion production on71the nuclei, A (p ,ir )B , has been of great in terest in interm ediate-energy nuclear physics. Theoretical s tud ­ies have shown th a t the proton-induced pion produc­tion from the nuclei goes th rough a t least 2-nucleon mechanism . It has been argued th a t the basic reaction m echanism involved in the A(p, ir)B reaction is the two-body pp —► dir reaction. Evidence of th is comes from the com parison of the analysing power A y for the two reactions a t the appropria te kinem atics and final s ta tes. T he two analysing powers look rem ark­ably sim ilar in shape and m agnitude. Therefore, for an understand ing of the proton-induced pion produc­tion on the nuclei, and o ther sim ilar reactions, it would be n a tu ra l to study the effect of the nuclear m edium m odifications on the reaction pp —► dir.T he reaction pp —► dir will be modified in the nu­clear m edium due to the following effects: 1) The in itia l-sta te distortions of the incident proton beam, 2) Fermi m otion of the bound nucleon in the target nu­cleus, 3) final-state distortions of the outgoing pion and deuteron, and 4) possibility th a t the quasi-deuteron wave function is different from the free deuteron wave function. T he sim plest reaction to study pp —► dir is the reaction A (p ,d ir)B . We can look a t th is reaction asA + P i = ( A - i y + {p*i +p*)->d* + 1T* + B * - * d + i r + B .A t the present stage of understanding we have con­siderable confidence in our understanding of the initial and the final-state d istortions. T hus the theoretical inpu ts necessary to study A(p ,d ir)B reaction are well understood. T he experim ental study of this reaction will help in understanding how the basic two-body re­action is modified in the nuclear environm ent. This work is in progress.F ew -n u cleon p rocessesO ff-shell n o n u n i ta r i ty a n d th e L o v e-F ra n ey in te r a c t io n in p r o to n - p r o to n b r e m s s t r a h lu n g(H. W. Fearing; M.H. Macfarlane, Indiana University)The Love-Franey in teraction is a pseudopotential which has been extensively used in a variety of nucleon- nucleus calculations. By pseudopotential one means an effective in teraction so constructed th a t its on-shell Born approxim ation m atrix elem ents reproduce the known nucleon-nucleon on-shell T -m atrix . Off-shell T- m atrix elem ents can then be generated sim ply by tak ­ing m atrix elem ents using off-shell wave functions and such off-shell m atrix elem ents are used in practical cal­culations. However, there is no reason in principle why such off-shell m atrix elem ents, derived from a purely on-shell interaction , should bear any relation to off-shell m atrix elem ents calculated from some physically realistic two-nucleon poten tia l. In fact it has recently been shown th a t such m atrix elem ents violate off-shell un itarity [M acfarlane and Redish, Univ. of M aryland preprin t #88-060].It is thus of in terest to apply the Love-Franey in ter­action to a process, nam ely pro ton-pro ton brem sstrah­lung, where it has recently been shown th a t off-shell effects are im portan t in reproducing the analysing pow­ers [Kitching et al., Phys. Rev. L ett. 57, 2363 (1987); Fearing, Nucl. Phys. A 4 6 3 , 95 (1987)]. Since non­u n itarity m anifests itself in altered phases for the off- shell am plitudes, one m ight expect th a t the analysing powers, which depend on interferences of am plitudes, m ight be particu larly sensitive. T his analysis is now well under way and results are expected shortly.B r e m s s tr a h lu n g c a lc u la t io n s fo r a v a r ie ty o f c o -o rd in a te sp a c e n u c le o n -n u c le o n p o te n t ia ls(H .W . Fearing, K. Rajagopal)Recent calculations of p ro ton-pro ton brem sstrah­lung [Workman and Fearing, Phys. Rev. C 34, 780 (1986); Fearing, Nucl. Phys. A 4 6 3 , 95 (1987)] when com pared w ith new experim ental d a ta for the analysing power [Kitching et al., Phys. Rev. L ett. 57, 2363 (1986)] have shown th a t m odern potentials such as the Paris or Bonn poten tia ls do a good job of re­producing the d a ta and indicate clearly for the first tim e in th is process th a t off-shell effects are necessary to describe the results. A rem aining puzzle, however, is why the various po ten tia ls tried seem to give such sim ilar results. A lthough some explanation for this comes from the fact th a t the po ten tia ls tried are also very sim ilar off shell, i t is still of in terest to explore a variety of o ther potentials. To th is end we have ex­tended the original calculation which was done in mo­m entum space so th a t it can handle an a rb itra ry co­ord inate space po ten tia l. Three such poten tia ls were then considered. One was one of the Argonne poten­tials [W iringa et a l , Phys. Rev. C 29 , 1207 (1984)] obtained by fitting the nucleon-nucleon data . A nother was obtained from a quark-based model [Beyer and W eber, Phys. Rev. C 35, 14 (1987) ] and the th ird was a po ten tia l [Ray, Phys. Rev. C 35, 1072 (1987)] generated again by fitting data .Surprisingly the results using these potentials show great similarity, even though in isolated p artia l waves there are differences in the off-shell behaviour. In fact it appears th a t sim ilar results are obtained from all nucleon-nucleon poten tia ls which fit the elastic phases, have a proper one-pion tail, and have some interm e­d iate range a ttrac tio n param etrized by particle ex­change, conditions m et by all of the potentials we have tried. More detailed exam inations suggest th a t there72may be some significant cancellations which tend to wash ou t certain kinds of differences and suggest also th a t neu tron-pro ton brem sstrahlung m ight be more sensitive to such differences. These results are being explored further.P io n p h ysics7r+ -p ro to n b re m ss tra h lu n g : A covarian t ap p ro ach(R. Wittman)W ith the pressing need for models of hadronic sub­struc tu re and u ltim ately for QCD to make contact w ith as m any “well determ ined” observables as is possible, a continuing experim ental and theoretical effort ex­ists to ex trac t the A(1232) diagonal as well as tra n ­sition electrom agnetic observables. For this reason, the original suggestion of K ondratyuk and Ponom arev [Sov. J . Nucl. Phys. 7, 82 (1968)] to consider radia­tive 7r+p scattering as a m eans of deducing the di­agonal A ++ m agnetic m om ent continues to encour­age new brem sstrahlung m easurem ents [TRIUM F pro­posal for E xpt. 446] and new phenomenological mod­els. Recently, the (M IT) model of Heller et al. [Phys. Rev. C 35 , 718 (1987)] has become the first calcula­tion (explicitly containing the A -isobar) th a t respects gauge invariance, unitarity , and the soft photon limit as well as considers a dynam ical trea tm en t of the irN A vertex function. T heir work stresses the need for dy­nam ical consistency between the elastic and radiative processes— indeed the definition of a m agnetic m om ent of a strongly decaying particle dem ands th is consis­tency.As an a lternative to the M IT model, I have investi­gated a model in which the 7r+ - p elastic and radiative processes are trea ted on the same dynam ical footing w ithin a relativ istic K -m atrix approach. T he approach is constructed in a form th a t form ally resembles a four­dim ensional sca ttering theory to allow a more physi­cal or in tu itive illustra tion of the underlying dynamics. Such a model m ight be considered as the sim plest phe­nomenological approach available th a t respects gauge invariance, un itarity , the soft photon lim it and Lorentz invariance. T his approach, although sim pler in some respects to the M IT approach, allows the advantage of retain ing the full covariant s truc tu re and fram e inde­pendence of all expressions. Therefore, the boosting of am plitudes or of vertex functions is avoided.This K -m atrix model seems to fit the d a ta as well as the M IT model, especially in the sen­sitive region. T he curves of Fig. 82 correspond to three values of the A ++ m agnetic m om ent given by P a+ + /a E y bu t have subsequently found and corrected an error and now ob tain results very similar to ours. [See the following contribution.] O ur results have now been subm itted for publication [Workman and Fearing, TR I-PP-87-78].R ad ia tiv e K ~ c a p tu re in hyd ro g en(Y.S. Zhong, Beijing; A.W. Thomas, Adelaide;B.K. Jennings; R.C. Barrett, Surrey)The cloudy bag model has proven to be a productive model for describing low-energy properties of baryons. In particu lar it has done a good job on various meson-baryon sca ttering problem s. One of its m ore in terest­ing conclusions is th a t the A(1405) is prim arily a I<- nucleon bound s ta te ra th e r th an a three-quark state. A lthough the A(1405) is only 30 MeV below the K - nucleon threshold there are indications the A(1405) is not a good B reit-W igner resonance so extrapolating from 1405 MeV to threshold is not triv ial. I t is there­fore of in terest to investigate various properties of the AT-nucleon system . One reaction where there promises to be experim ental d a ta is the radiative decay of kaonic hydrogen. We have calculated the branching ra tio for the decays K ~ p —► A y and K ~ p —► E°y in a chiral SU(3) version of the cloudy bag model. T he calculated branching ra tio for Ay is 1.9 x 10~3, in agreem ent with existing experim ental d a ta while the branching ratio for E °y is 2.3 x 1 0 -3. I t is expected th a t there will soon be experim ental d a ta from Brookhaven to com­pare w ith th is value.S tu d y o f th e re a c tio n K d —► Any (H.W. Fearing, R.L. Workman)A nother few-body kaon reaction K d —*■ A n y is also being studied as a logical extension of the work on K p —* Ay . I t is of in terest for the inform ation on the low-energy A - N in teraction which one m ay ob­ta in by looking a t the photon spectrum a t the high- energy end, ju s t as the neutron-neutron scattering length was ob tained by looking a t the photon spec­tru m in ird —► nn y . We have s ta rted w ith an effective in teraction derived as described above for the reaction K ~ p —*■ Ay supplem ented by term s proportional to the initial p roton m om entum which are necessary because of the deuteron bound s ta te . T his operator is then evaluated between deuteron and final-state scattering wave functions. A nother com plication is the possibil­ity of additional channels in which, say, a E produced in the radiative process is transform ed to a A in the strong rescattering process.We have exam ined sensitivities of the photon spec­tru m to different deuteron wave functions, including both S and D s ta tes, to the m om entum -dependent term s, to the o ther possible channels, and to the ef­fective range in the rescattering. I t tu rns out th a t all of these effects have little influence on the shape of the photon spectrum near the endpoint, which ap­pears to depend prim arily on the A-nucleon scattering length. T hus a m easurem ent of th is shape should give inform ation on th is scattering length. One can clearly see differences between the no rescattering case and a case involving a realistic estim ate of the rescattering. To distinguish details of the rescattering , however, will require kaon beam s much b e tte r th an currently avail­able, such as those possible a t the proposed TRIU M F KAON factory.75T his work has been described in detail in a thesis [W orkman, UBC Ph.D . thesis, (1987)] and is being w ritten up for publication.E lectro n sc a tter in gP a rity -v io la tin g w eak n e u tra l c u rre n t effects in e lec tro n sc a tte r in g (P.G. Blunden)Parity-vio lating weak neu tra l effects in nuclei have been exam ined in order to look for favourable nuclear transitions which could be m easured experim entally w ith polarized electrons. C onsideration has been given to the effects of isospin mixing in N — Z nuclei and to parity adm ixtures from the hadronic interaction. It is conceivable th a t in these transitions one may be able to study aspects of nuclear stru c tu re which cannot be obtained otherwise.M eson exch an g e c u rre n ts in quasie lastic e lec tro n s c a tte r in g (P. Blunden, M.N. Butler)There has been a great deal of work done on the im portance of meson exchange curren ts in quasielastic electron scattering . However, m ost of it has been in the nonrelativ istic regim e for reasons of simplicity, b u t the experim ents deal w ith kinem atics which are definitely relativistic in na tu re . T his can be especially im por­ta n t when one is looking a t the large energy transfer side of the quasielastic peak, near the pion production threshold. Here the pion p ropagator is alm ost on shell, and a nonrelativ istic approxim ation to the propagator cannot properly account for the physics.We in tend to tre a t the meson exchange currents due to one-pion exchange fully relativistically, s ta r t­ing w ithin the fram ework of a relativ istic Fermi-gas model. From there we hope to extend our calculation to use relativistic-H artree-Fock wave functions for the ta rg e t nuclei. B oth inclusive and exclusive scattering processes will be exam ined.S y m m e tr y b reak in gS tro n g C P -v io la tio n in th e SU (2) S kyrm e m odel(R. Wittman, R.M. Woloshyn)It is known th a t instan ton effects can produce a C P-violating effective in teraction of the type = —9(g2/3 2 n 2) F ■ F in QCD. This has physical consequences such as allowing a strong C P-violating t N coupling (gwlqN ). Such a coupling can provide a m echanism for the neutron electric dipole mom ent D n [Crewther et al., Phys. L ett. 8 8 B , 123 (1979)]. One approach th a t can relate the QCD 9 param eter to g^NN or to D n is to consider a low-energy effectiveLagrangian of the type constructed by Di Vecchia and Veneziano [Nucl. Phys. B 1 7 1 , 253 (1980)]. In addi­tion to the chiral sym m etry breaking mass term s, this Lagrangian contains the large NcoiOUr lim it rem nant of the QCD 9 term . Schnitzer [Phys. L ett. 1 39B , 217 (1984)] has considered such an effective Lagrangian in the context of skyrm ion solutions to ex trac t the 9 de­pendence o f g wNN. A crucial aspect of Schnitzer’s ex­trac tion depends on em bedding the “Skyrme ansatz” into SU(3) flavour; we find th a t gwNN vanishes for the SU(2) flavour scheme, even when a scalar flavour sin­glet field (representing the rj meson) is included in the norm al SU(2) soliton as Uo = exp[iS(r)] exp[iF’( r ) r - r ] . We are interested in identifying the special feature of SU(3) which allows a nonzero gwjqqq and understand­ing if it is indeed a physical aspect of the original QCD Lagrangian.E ffect o f p ro to n -n e u tro n m ass d ifference on charge sy m m etry b reak in g in n e u tro n -p ro to n sc a tte r in g (M.J. Iqbal, J. Thaler, R.M. Woloshyn)There is a renewed in terest in the study of the charge sym m etry breaking in the p ro ton-neutron elas­tic scattering due to a recent experim ent perform ed a t TR IU M F [Abegg et a l , Phys. Rev. L ett. 56, 2571 (1986)]. The m ajor contribution to CSB arises from the proton-neutron m ass difference. We have calcu­lated, for the first tim e, the nucleon m ass difference contribution to charge sym m etry breaking (CSB) in neutron-proton scattering in a relativ istic form alism based upon a covariant represen tation of the N N am ­plitude. The CSB am plitude was separa ted into two term s: a piece which involves the on-shell charge sym ­m etric T -m atrix w ith CSB arising due to effects in ex­ternal wave functions, and a te rm involving off-shell T -m atrices w ith CSB associated w ith m ass difference effects in in ternal nucleon propagators. We found th a t m ost of the CSB arising from the neutron-pro ton mass difference comes from the la tte r term [Iqbal et a l, Phys. Rev. C 36, 2442 (1987)].C h arg e sy m m etry b reak in g in th e N N force (J.A. Niskanen, TRIUMF-UBC; A.W. Thomas, Adelaide)Charge sym m etry (and isospin conservation) is known to be only approxim ate. Its breaking (CSB) due to hadron mass differences, electrom agnetic effects and meson mixings may have roots in the underlying quark s tructu re , no tab ly the quark m ass differences. Careful studies of CSB (as difficult as they may be experim en­tally) ought to result in constrain ts on hadronic in­teractions com plem entary to the sym m etry-conserving case, e.g., in com parisons of quark m echanisms with meson exchanges. A t the very least one should find76new constrain ts on some coupling constants (such as the rjN N coupling) also otherwise difficult to get. Re­cently [Niskanen and Thom as, A delaide preprin t AD P- 87-2/T30; Niskanen et al., A delaide p reprin t ADP-87- 20/T37; and Niskanen and Thom as, A ustr. J . Phys., in press)] the effect of the A(1232)-isobar has been in­corporated in to CSB in the N N in teraction and in the reaction np —+ dir0 on the sam e footing as the nucleon effects. A particu la r im portance of the ip*0 (rf ir°) mix­ing was observed. T his work will be continued.C harge sy m m e tr y b reak in g in th e rea ctio nnp —► dir0 (M .J. Iqbal; R. Dymarz, S. Hama;F.C. Khanna, H. Sherif, Alberta)T he contribu tion to the charge sym m etry breaking (CSB) in p ro ton-neutron elastic scattering comes from class IV type forces alone. For more complex reactions both class III and class IV type forces will contribute to CSB. T he sim plest reaction of th is type is np —+ dir0. In the absence of the CSB forces th is reaction is related to the pp —► dn+ reaction, which is well understood. This reaction is an excellent source for studying CSB effects coming from ir°-rj m ixing and m ass differences between different isospin sta tes of the delta. In these calculations we use a relativistic form alism to gener­ate bo th the charge sym m etric and charge sym m etry breaking am plitudes. T he calculations are well under way and results are expected in the w inter of 1988.C on trib u tion o f th e charge sy m m etry break ing forces to en ergy d ifferen ces in m irror n uclei(P.G. Blunden, M .J. Iqbal)C ontribu tions to energy differences in m irror nuclei and to the scattering length differences were evalu­ated from class III and class IV type charge sym m e­try breaking (CSB) potentials. We considered p°-u mixing, 7 r ° - r ; m ixing, one- and two-pion-exchange con­tribu tions. We have shown th a t the previous claims o f la rg e c o n tr ib u t io n s to th e e n e rg y d iffe ren ces d u e to two-pion-exchange diagram s are not correct. Po ten­tials which were consistent w ith the scattering length differences and w ith recent CSB p-n elastic scatter­ing d a ta were found to contribute about 150-250 keV to the energy differences in m irror nuclei [Phys. Lett. B 1 9 8 , 14 (1987)].Q C D and quark m od elsT h e q u a rk -g lu o n /h a d ro n p h ase tra n sitio n and its effects on p rim ord ia l n u c leo sy n th esis(M .N. Butler; R .A . Malaney, Caltech; M .-C. Chu, M IT)There has been a surge of in terest in the struc tu re of the phase transition between quarks/g luons andhadrons after the Big Bang. If the phase transition is first order, and a t a low enough tem peratu re, then drastic changes take place, producing heavy elements in the Big Bang, and conditions allow the universe to be com pletely closed by baryons. No new, exotic dark m atte r is necessary. A t present la ttice gauge calcula­tions do no t seem to give a definitive answer on the natu re of the phase transition , and it is not likely th a t they soon will. We are currently studying phenomeno­logical models of QCD to see which m ight be better suited for th is sim ulation. A t present the dual su­perconductor model of QCD seems to give the best approach to the problem . Using th is model we are perform ing a calculation to study the dynam ics of the phase transition , it is hoped determ ining the transition tem perature, order and free-energy behaviour for the two phases.T h ree-g lu on a n n ih ila tio n o f D -w ave quarkonium(G. Belanger; P. Moxhay, Colorado)Formulas are ob tained for the three-gluon annihila­tion rates of 3D quarkonium states. For the T (1D ) the w idths of 3D j —► 3g are estim ated to be 2.2, 0.26 and 1.1 keV for J = 1 ,2 ,3 . T he smallness of these rates as com pared w ith the expected electric-dipole rates of ID —+ I P + 7 ~ 10-30 keV is favourable for observing the I D in electrom agnetic transitions of the T(3S').Q uark m o d el for b aryon -an tib aryon an n ih ila tion(J .A . Niskanen, TRIU M F-U BC )A ttem pts to understand low-energy baryon-anti­baryon annihilation a t the quark level are tim ely be­cause of experim ental breakthroughs a t the low-energy an tipro ton ring (LEAR) a t CERN , and are likely to be relevant for the fu ture KAON factory as well. So far the models have had less th an perfect success. One can hardly consider the annihilation m echanism un­d e rs to o d , if o n ly 60-80% of th e e x p e r im e n ta l a n n ih i­lation cross section is reproduced w ithout added phe­nomenology [Green and Niskanen, Prog. P a rt. Nucl. Phys. 18, 93 (1987)]. A pure rearrangem ent into three mesons is certainly insufficient and the additional two- meson annihilation needs an effective operator to an­nihilate a quark-antiquark pair in the hadronic interi­ors. The natu re of th is opera to r is not clear, bu t may be crucial in producing enough annihilation. A widely used vertex is the 3To one w ith vacuum quantum num ­bers, a simple “one-body” operator. T he problem with th is vertex is th a t the relative o rb ita l angular momen­tu m of the quark-an tiquark pairs (in the final-state mesons or in the annihilation vertex) is directly linked to the relative baryon-antibaryon angular m om entum L. Therefore two p-wave mesons in the final sta te (one77could be 3P 0) produces two B B m om entum operators (~ V ) , which often m ust be coupled to a to ta l 5 -s ta te (especially in the 5 -s ta te annihilation). The resulting V 2 opera to r causes nodes in the (separable) B B optical po ten tia l decreasing it [Niskanen op. cit.]. In particu ­lar, in 5 -sta tes annihilation rem ains only as roughly half of the un ita rity lim it. One would expect more like ~100% . As a way to get around the difficulty of the nodes, the 35 i (gluon) two-body opera to r was a t­tem pted for the 5-waves, w ith the sam e streng th as the 3P 0 [Niskanen, A IP Conf. Proc. 150 (AIP, New York, 1986), p. 406]. A possible justification for this may be the nonpertu rbative na tu re of gluon exchanges a t low energies: if the 3Po sim ulates a m ulti-gluon ex­change m echanism , then the m echanism w ith one more gluon (w ith gluon quan tum num bers) should be as im ­p o rtan t. This 5-wave opera to r does not bring along ex tra nodes, and a m arked increase (up to about 90% of the un ita rity lim it) was ob tained in the 5-wave an­nihilation. W ork is going on to find if a sim ilar im­provem ent can be found also for P-waves. One m ight expect so, because new im portan t final sta tes will be possible, nam ely 5-wave and p-wave meson in a rela­tive p -sta te which cannot be reached by a single 3Po operator.L a ttice gau ge ca lcu la tion sH ea v y m eso n d eca y co n sta n ts(T. Draper, R.M. Woloshyn; K.F. Liu, Kentucky;W. Wilcox, Baylor)Decay constan ts of vector and pseudoscalar mesons were calculated using quenched quan tum chrom ody­nam ics on the lattice. T he vector meson decay con­s ta n t ca lcu la ted u sing th e W ilson schem e for la ttic e ferm ions is in good agreem ent w ith experim ental val­ues. Pseudoscalar meson decay constants were cal­culated for bo th the W ilson and staggered fermion schemes. For pseudoscalar mesons containing unequal mass valence quarks no indication was seen, in the lim it th a t the heavier quark m ass becomes large, of the falloff in the decay constan t predicted by nonrela­tiv istic quark m odel argum ents.P io n e lec tr ic form factors(T. Draper, R.M. Woloshyn; W. Wilcox, Baylor;K.F. Liu, Kentucky)We extended earlier num erical work on pseudoscalar electric form factors from the com putationally sim pler case of SU(2) colour to the physically more relevant case of SU(3). The sim ulation regularized pa th in te­grals by using a space-tim e grid, or lattice, to reduce the quark-gluon degrees of freedom to a num ber di­gestible by a supercom puter; in the present work a m odest am ount (abou t 60 h) of CRAY 2 resources were consumed. Valence ferm ions were incorporated via the W ilson scheme, which exactly preserves gauge invari­ance and discrete sym m etries such as C P T ; however, the space-tim e discretization explicitly breaks Lorentz invariance (which is recovered as the space-tim e mesh is m ade finer). T he effects of dynam ical fermions (the “sea” ) had to be neglected (the “quenched approxim a­tion” ). Lattice pseudoscalar masses were tunable by an ad justable inpu t param eter and, for technical rea­sons, were lim ited to values above the ir physical ones (to which extrapolations are to be m ade.)The com putation of m eson-current-m eson three- point G reen’s functions was reduced, by a sequential source technique, to the s tan d ard evaluation of two- point functions. Im proved error reduction m ethods allowed us to see system atic deviations, a t large Q 2 (four-m om entum transfer squared), from the theoreti­cally anticipated vector dom inance relation for the pion form factor. This need no t be regarded as physical, for we saw small bu t significant deviations from the con­tinuum relativ istic dispersion relation. T his is presum ­ably an artifac t of the coarseness of the la ttice which can be im proved w ith increased com puter resources.As a by-product, we have learned th a t pionic ener­gies for given inpu t m om enta can be extracted from two-point functions a t much sm aller la ttice tim e sepa­rations th an previously though t. T his will appreciably reduce the size of the la ttice required for those inter­ested in looking a t propagators and m atrix elem ents as nonzero m om enta (which is necessary to keep hadrons on shell). Indications are th a t th is will allow us to ex tract a signal for hadrons in a nonzero-m om entum fram e, which is desirable since th is probes sm aller Q 2. This should m ake a fu tu re study of nucleon form fac­tors feasible, w ith only a reasonable increase in com­pu ter resources.N uclear a x ia l v ec to r cou p lin g(R.M. Woloshyn; K.F. Liu, Kentucky)T he m atrix elem ent of the axial vector current, g^, and the ra tio F / D are being calculated in quenched la ttice QCD. The calculation is done using the W ilson scheme for la ttice fermions. A t values of the hopping param eter near «cr, gJ4 and F / D are subject to very se­vere sta tistica l fluctuations and a direct m easurem ent of these quantities in the physical region of u- and d- quark masses is not feasible. However, ex trapolating from heavier quark mass, where the num erical simula­tion is stable, gives « 1.1. I t is also verified th a t the correct value for gA is ob tained in the numerical sim ulation in the s ta tic lim it (very massive quarks).78E lectrow eak in teraction sE ffect o f th e A(1232) on sp ec tru m an d asym m etry in rad ia tive m u on ca p tu re on th e p roton(H. W. Fearing; D .S. Beder, UBC)In view of the current T R IU M F experim ent on ra­diative m uon capture on the proton and of in terest in using this process to ex trac t a precise value for the weak in teraction induced pseudoscalar coupling con­stan t gp we recently exam ined some contributions of the A(1232) to the photon spectrum in this reaction. In th is work, now published [Beder and Fearing, Phys. Rev. D 3 5 , 2130 (1987)], we found th a t the A changed the spectrum by am ounts of the order of 7-8% . Such effects, while no t large, will still be necessary to obtain a precision result for gp.We now have extended th is calculation in several ways. F irst we consider an improved description of the A TV 7 vertex which properly generates both m agnetic dipole and electric quadrupole couplings as determ ined from fits to pion photoproduction data . T his new ver­tex makes very little difference in the radiative muon capture results, thus validating our original simplified approxim ation. Second we exam ine the m agnitude of the A(1232) effects for various values of gp to see if there is a correlation between the size of these effects and the value of gp. Generally the size of these con­tribu tions tu rn out to be p re tty much independent of gp except for some very in teresting sensitivities in the currently unm easurable singlet spin com bination. Fi­nally we additionally consider the photon asym m etry, to see if there is any increased sensitivity there to such effects, and find th a t there A effects are very small. These extensions of our previous calculations are cur­rently being w ritten up for publication.L e p to n -v e c to r le p to n m ix in g s a n d u n i t a r i ty b o u n d s(D. London, G. Belanger, J.N . Ng)Vector leptons (TV, E ) are present in bo th Eg and SU(18) unified theories. We derive linear relations be­tween the masses of these vector leptons and ordinary leptons and their m ixing angles. The am plitudes for processes such as E +E —► boson pairs are calculated. The m ass mixing angle relations are crucial in free uni­ta rity considerations. Unlike the case of fourth genera­tion leptons no bounds from p ertu rba tive un itarity can be p u t on the masses of the vector leptons.A n o m a lo u s m o m e n ts o f W b o so n s in b ro k e n s u p e r- s y m m e tr ic m o d e ls (G. Couture, J.N . Ng; J.L. Hewett, T.G. Rizzo, Iowa State)T he contributions to the anom alous m agnetic dipole and electric quadrupole m om ents of the W bosons inbroken supersym m etric-standard model are calculated. It is found th a t supersym m etry is no t likely to induce anom alous m om ents larger th a n 0 .1 % which is smaller than the upper bound of the contribution from the standard model.A x io n s in S U (2 )x U (1 )x U p < } (1 )x U m (1 ) a n d ra re d ec ay s (J.N . Ng; X .D . Jiang, TRIU M F)Recently Peccei, Langacker and Y anagida con­structed an extension of the stan d ard model w ith two additional global U (l) sym m etries. If the breaking of these U ( l ) ’s are a t the sam e scale it leads to M ajorana neutrinos and axions w ith masses in the range of a few eV or less. We are calculating the ra te of /i —» ea and H —♦ e ja as a probe of the sym m etry-breaking scale in th is class of models.T h e r a r e d e c a y K —* t j j (J.N . Ng, J. Iqbal, S. Fortin)This process is well known to be GIM suppressed and hence is sensitive to the heavy quark masses. We cal­culate the contribu tion of th is by focusing on the short d istance effect. T he effective s —► d y j Lagrangian is constructed using a novel nonlinear gauge which sim­plifies the calculation trem endously. The calculation of the lowest-order QCD correction is under way. This process is not only po ten tia lly im portan t in looking for new physics such as heavy quarks bu t also an impor­ta n t background reaction to the K —> -kvV experim ent.F in i te iV = l s u p e r s y m m e tr ic th e o r ie s(X.D . Jiang, X .J . Zhou, Beijing)Any N = 1 supersym m etric Yang-Mills (SYM) the­ory which is finite a t one loop is also autom atically finite a t two loops. However, analyses of three loops supergraphs have shown th a t two-loop finiteness which autom atically keeps the gauge superfield renorm aliza­tion is also finite a t three loops and so gauge /^-function vanishes a t th is level b u t the m a tte r field self-energy does have a three-loop infinity. All above discussions are based on an im plicit assum ption th a t all Yukawa couplings in the theories are p roportional to the gauge coupling constan t g. In general Yukawa couplings may be Taylor series in g. In th is respect, recently some people propose an algorithm to construct finite IV =1 SYM theories to all orders by fine tun ing the coeffi­cients of the Taylor series of Yukawa couplings. Using th is algorithm we fu rther investigate the conditions of finite 7V=1 SYM theories and ob tain a large class of finite in all orders IV=1 SYM theories of representa­tions of all classical groups based on our previous work of two-loop finite SYM theories.79M u on sp in ro ta tio nM a g n e tic p r o p e r t ie s o f h ig h -T c s u p e rc o n d u c to r s(M. Celio; T. Riseman, UBC; J. Kossler, Williamsburg)T he recent discovery of superconductiv ity a t tem per­atures close or above th a t of liquid nitrogen (~ 90 K) in a num ber of ceramic oxides has led to an extraor­dinary num ber of m easurem ents on these com pounds. T he m uon spin ro ta tion (^SR ) group a t TR IU M F has been am ong the first to apply th is spectroscopic tech­nique to investigate the m agnetic properties of these ceramics, in particu lar to study the tem pera tu re de­pendence of the London penetra tion depth A [Aeppli et al., Phys. Rev. B 3 5 , 7129 (1987); H arshm an et al, Phys. Rev. B 3 6 , 2386 (1987)], and to detect antifer­rom agnetic ordered states.T he analysis of m ost of these experim ents is based on the determ ination of the m agnetic field d istribu­tion inside the probes, which tu rns out to be a diffi­cult task due the fact th a t these superconductors are bo th granular and anisotropic. Basically, one has to solve the anisotropic London equations w ith appropri­ate boundary conditions in the interm ediate s ta te , i.e., where the applied field H (H ci < H < R c2) enters the superconductors as an array of vorteces. A de­tailed analysis of the field variation between the vorte­ces yields an explicit d istribu tion which is m apped into the m easured ^iSR line shapes. F irst com pari­son of the theoretical models w ith the d a ta leads to London penetra tion depths of about 1250 and 600 A for L a i.85Sro.i5C u 04 and Y B a2C u30 7 _«, respec­tively.M u o n iu m s ta te s in s e m ic o n d u c to rs(M. Celio; R. Kiefl, UBC; T. Estle, Rice)In the past m onths m uon level-crossing resonance spectroscopy has been successfully applied to describe the electronic s truc tu re of the anom alous m uonium s ta te (Mu*) in several sem iconductors. In particular, experim ents on GaAs and G aP [Kiefl et a l , Phys. Rev. L ett. 58, 1780 (1987)] and silicon [Kiefl et a l , subm it­ted to Phys. Rev. Lett.] have brought support to arecently proposed model in which Mu* is a neutral in­te rstitia l located close to the centre of the GaAs bond or between two silicon atom s along one of the < 111 > axes, respectively.The theoretical analysis of these experim ents was carried ou t by solving a model spin H am iltonian in­cluding the nuclear hyperfine tensor (nh t) as a param ­eter. D irect com parison of the theoretical sim ulations w ith the m easured spectra has revealed th a t the nht is axially sym m etric along one of the < 111 > crystal axes and has allowed us to determ ine the value of the nuclear hyperfine in teractions in GaAs, G aP and sili­con. Finally, from these results we got estim ates for the spin densities on the nearest atom s, which are of extrem e in terest in the field of hydrogen-like defects in semiconductors.S p in r e la x a t io n e ffec ts in m u o n le v e l-c ro ss in g e x p e r im e n ts(M. Celio; H.K.Yen, UBC; B.D. Patterson, Zurich)A few years ago I developed a model to describe the spin relaxation of m uonium in solids and liquids. The model, which is based on a m aster equation approach, was applied successfully to the analysis of yi/SR experi­m ents in KC1 [Celio, Helv. Phys. A cta 60, 600 (1987)], bu t had to be solved only by a tedious num erical pro­cedure.In the last m onths we have shown th a t the same model can be derived w ithin the fram ework of the Red- field theory, which allows a deeper insight in to the physics of the problem and leads to analytical solu­tions. Moreover, the sam e idea has been applied to describe relaxation effects in cases where a m uonium atom is used in level-crossing experim ents. In this case as well, analytical expressions for the field depen­dence of the various relaxation rates could be obtained. These results are currently being com pared w ith ^S R m easurem ents on free radicals and it is hoped we will be able to determ ine characteristic param eters, such as correlation tim e and typical in teraction strengths, which describe the dynam ics of the processes under investigation.80APPLIED PROGRAMS DIVISIONIN T R O D U C T IO NThere has been steady progress in A pplied Program s developm ent as well as regular support of the day-to- day group effort. For instance, the pion radiotherapy group trea ted 29 patien ts and as well upgraded the fa­cility in antic ipation of 200 /iA beam line 1 operation. The radioisotope p roduction team has maximized the production of isotopes from the CP-42 cyclotron and has also in troduced new radiopharm aceuticals to their product line. T he P E T group has developed U C- labelled dopam ine receptor agents while continuing to supply 18F-labelled com pounds. D etailed design has begun on a large volume positron emission tom ograph. The gallium -arsenide m icrostructures laboratory has developed and tested the operational characteristics of their GaAs CCDs and has begun a collaboration w ith M icrotel Pacific Research to use the devices in nucleon­ics applications. T he usefulness of TR IU M F for topics outside of pure nuclear and particle physics is becoming m ore apparen t and im portan t. T he progress described in this section is a m easure of the a tten tion paid to the Applied Program s.B IO M E D IC A L P R O G R A MAfter the repairs of last year, the pion radiotherapy program resum ed vigorous activities in 1987. A new rad io therapy technician was added to the team for the ex tra patien t load. Tw enty-nine p atien ts were treated for the year, bringing the to ta l num ber trea ted to 144, which includes 83 brain tum ours, 53 pelvic tum ours and 8 others. A list of p a tien t trea tm en ts for 1987 is shown in Table X. For the past year the cyclotron ou tp u t was reliable and stable w ith very little delay in our scheduled trea tm en ts. Only a week or so of beam tim e was lost tow ards the end of A ugust due to the failure of the transform er in the T R IU M F rf system. On the o ther hand, the hardw are on the M8 channel perform ed so well th a t no t a single trea tm en t day was lost due to M8 channel failure for the entire year.Early in Jan u ary we were presented w ith two brain patien ts w ith tum ours righ t in front of the brain stem . In order to sharpen the d istal fall-off in the depth dose profiles to reduce doses to these vi­ta l s truc tu res for these patien ts, it was decided to reactivate the m om entum -defining blades th a t were installed in the M8 channel. These m om entum blades were initially designed for the m odulation of the pion depth dose profiles using dynam ic controlduring beam delivery. However, the use of these blades led to a general reduction in pion flux, which in tu rn increased the trea tm en t tim e required. In 1980 the present range shifter was constructed, which can be used to generate the uniform depth dose curvesTable X. Summary of TRIU M F pion patien t treatm ents for 1987.Run Patient Fractionfinished/intendedTotaldaysDose/ fraction (x - rad)Jan 87-1 brain 15/15 22 24087-2 brain 15/15 20 22087-3 brain 15/15 20 22087-4 pelvis 14/15 19 22087-5 brain 15/15 18 220May- 87-6 brain 15/15 19 220Jun 87-7 brain 15/15 18 22087-8 brain 15/15 18 24087-9 brain 15/15 19 22087-10 brain 15/15 20 24087-11 brain 15/15 20 22087-12 brain 15/15 20 22087-13 naso­pharynx9/10 10 200Jul- 87-14 pelvis 15/15 26 223Aug 87-15 brain 15/15 19 22087-13 naso­pharynx8/10 13 20087-16 brain 7/15 9 22087-17 brain 7/15 9 220Nov- 87-18 brain 10 /10 12 200Jan 87-19 brain 15/15 17 23087-20 brain 15/15 20 23087-21 brain 15/15 17 23087-22 brain 10 /10 23 25087-23 brain 11/15 15 22087-24 pelvis 12 / 12 23 25087-25 brain 15/15 23 23087-26 pelvis 12 / 12 24 25087-27 pelvis 15/15 24 23087-28 brain 2/15 2 23087-29 brain 15/15 28 22081required w ithout losing any pion flux. The use of the m om entum slits was therefore discontinued. By 1987 the o u tp u t of the cyclotron had reached 160 fiA, so we felt th a t we could then afford to sacrifice some pions to produce depth dose curves w ith a sharper fall-off, which the range-shifter is unable to generate.A lthough the use of collim ators can sharpen the field edge considerably, it has not been possible to have col­lim ators for all of our p a tien ts in the past several years. T his is largely because the conventional collimators have to be custom m ade (i.e. non-recyclable) and often cannot be m achined in tim e before the commencement of trea tm ents. In Ju ly a recyclable variable-size col­lim ator was constructed . It is m ade up of hundreds of sm all pieces of copper and plexiglas 0.25 in .2 rods th a t are packed together in rasters. For a given patien t the trea tm en t field outlines are first digitized using a graphic tab le t into a com puter, which calculates and plots a plan for the configuration of assembly of these copper and plexiglas rods. These collim ators can be adjusted to produce different field sizes as trea tm en t of a p a tien t progresses, and a t the end of the tre a t­m ent it can be taken ap art and reassembled for the next pa tien t.W ith the developm ent of such a versatile collim ator, a large variety of trea tm en t plans were devised to con­form m uch closer to the shape of the tum our. In order to verify these special plans, an au tom atic film densito­m eter scanning system was developed in la te July. The system is based on a sm all m echanical scanner which moves a film in 2D so th a t the optical density over the whole film can be read by a m icrocom puter. Using a stack of films sandw iched between pieces of plexiglas and using the axial depth dose m easurem ents from an ion cham ber, the com plete 3D dose profiles of tre a t­m ent fields can be displayed and com pared w ith those calculated in a plan. Before the developm ent of this system the dose profiles had to be m easured m anually using the densitom eter and hence only a few strateg ic points in the field could be verified.In the middle of the sum m er run there was a week or so of 200 pA for the purpose of testing various com­ponents for the operation of the T R IU M F cyclotron. Since our trea tm en t operation is largely dose-rate de­pendent, th is offered our team an excellent opportu­n ity for testing the adequacy of our present system for operation a t higher pion flux. A t 200 f iA the rad ia­tion background in the trea tm en t room during patien t set up was 30% higher and hence staff had to work at higher efficiency to reduce the tim e of exposure. On the o ther hand, the m echanical scanning system , which includes the couch and the range shifter, had to be in m otion for a longer fraction of tim e during each patien ttrea tm en t. All these were carefully m onitored during th a t special 200 n A period and it was concluded th a t the present staff and equipm ent would be capable of handling this forthcom ing higher flux operation.Our “new” com puter, an S-140 D a ta General, ar­rived in Septem ber. W ith the help of the TRIU M F com puter support group it was installed before the com m encem ent of the November run, replacing the ag­ing Nova II com puter which had been working fa ith ­fully for over 14 years bu t unfortunately had only 32K of core memory, severely lim iting the size and com­plexity of our control software. Several of the periph­erals, such as disc drive and video m onitor, will soon be upgraded to enhance the perform ance of this new com puting system.The year 1987 also m arks the fifth year after the com m encem ent of our deep-seated tum our radiother­apy program . T his enables us to compile some survival statistics. A com plete analysis of p a tien t response was made in July, and some of the results are presented as follows:1) The brain studyT he characteristics of the brain patien ts and the trea tm en t results are shown in Table XI, Figs. 84, 85 and 86.From these results it is clear th a t younger patients have significantly b e tte r survival th an patien ts of 50 years or older. On the o ther hand, survival appears to be im proving steadily w ith increasing dose. For these patien ts no dose-related acute reaction has been ob­served during trea tm en t. In general, the quality of life after pion trea tm en t is superior to th a t after conven­tional rad iation . Several p a tien ts were able to return to full em ploym ent after pion therapy.2) The pelvic studyT he results of pelvic trea tm en ts are shown in Ta­ble X II, Figs. 87 and 88.It appears th a t local control is b e tte r w ith dose greater th an 30 Gy, w ith p rosta te cancer having the best response. For bladder tum our the control ra te is about 40%. In particu lar, one of the first bladder pa­tien ts trea ted in A ugust 1982 can now be regarded as cured as she has passed the fifth year m ark w ithout any recurrence of her cancer.82SURVIVALT able XI. C h arac te ris tics of 62 b ra in p a tien ts tre a te d w ith pions.0.800 -0 .6000.4000.2000.0 + 0Sex Male 40 Female 22Age <50 years 15 >50 years 47Karnofsky score <70 21 >70 41Pathology* Grade 3 27 Grade 4 33Surgery Biopsy 22 Resection 40Site Frontal 17 Parietal 22Occipital 3 T em poral/o ther 20Presenting Seizures 13 I.C .P 14Symptoms Focal 26 O thers 9C T type Solid 25 Cystic 24SymptomMixed 7 N /S 6duration (m onths) Median 2 Range 1-18*2 ungraded patients.Fig. 84. Planned escalations of pion dose.1982 - 1986L1 ..I1P= 0.002...j< 49 yrs.> 50 yrs. -•100 200 300TIME400 500Fig. 85. Survival and age.1.000.800 -0.600 -0.400 -0.2000.0I "l **T"I!. x : 17.5 G y and 40 Gy Photons A • x : 25.5 G y and 20 Gy Photons B x : 30 - 36 G y Cp -0 .0 6100 200 300TIM EFig. 86 . Survival and dose.400 50083T able X II. Age, histology and stag ing ch arac te ris tics for 45 p a tie n ts tre a te dw ith e.c. for pelvic m alignancies.Colo-rectum P rostate BladderP atien t numbers 18 20 7Age (years) Median 64 72 68Range 42-86 53-78 60-76Tum our H>O'D0D O S E C G r a y ) D O S E C G r - a y DFig. 92. (a) Survival of V79 Chinese ham ster cells after exposure to X-rays (A ) or neutrons produced by 100 MeV p —* Be (■). Cells irradiated at 0°C. Solid lines represent fits to the expression S = exp(—crD—/3D2) for the full dose range, 0-13 Gy. (b) Survival of V79 cells after low doses of X-rays (A ) or neutrons (■). Details as for (a). Solid lines represent fits to the expression S = exp(—« D -/? D 2) for the low dose range only, 0-4 Gy.1) T he 787 drift cham ber system was com pleted dur­ing the year and was shipped to Brookhaven during the sum m er. T he system comprises about 2000 head amplifiers and associated support electronics, e.g., post amplifiers, shapers, discrim inators and electro­mechanical equipm ent. The group developed ampli­fiers w ith broadband and dynam ic range as presented in Fig. 93. The system was developed a t T R IU M F and the m anufacturing was done a t Pachena L td. w ith as­sistance from the T R IU M F design team .2) T he developm ent of the GaAs CCD signal pro­cessing electronics commenced in the fall of 1987 and work proceeds. T he GaAs CCDs were m ade a t the 64 pixel level and devices were used to develop the signal processing electronics. These devices are currently be­ing modified and the project is proceeding in to its next phase during early 1988.The original m otivation for the GaAs CCD work was to develop fast electronics for 7r+ identification in the Brookhaven E xpt. 787 system . A signal is cap tured in the CCD w ith a tim e base of about 2 ns/p ixel and then presented to a stan d ard silicon flash ADC a t a ra te of several hundred ns/p ixel on dem and. Since the CCD is an in tegrated m icrocircuit, the system production cost is reduced to a range where several thousand channel system s can be produced.a) OUTPUT SIGNAL FOR 100 mV behind lpF_i i i i i i i I i_b )OUTPUT SIGNAL FOR 1 mV behind lpF- I I I I I I I I L-Fig. 93. O utput response of preamplifier into 50 fl for a (a) 10-13C input and (b) 10~14C input, (c) Crosstalk at the ou tput to adjacent channel for a 10 ~ 13 input.89Two versions of 64 pixel CCDs are under develop­m ent. The first uses a l p gate w idth for charge trans­po rt and the second uses a 3 p gate w idth w ith a cerm et layer. T he la tte r is preferred since potential charge trap s are minimized as shown in Fig. 94. The CCDs have been produced in the TR IU M F m icrocir­cuits laboratory and a com parison of an inpu t signal w ith the CCD o u tp u t is presented in Fig. 95. T he de­vices have been operated a t frequencies between 1 GHz and 1 MHz. T ransient digitizer system s using these CCDs are under developm ent now.3) The construction of the p lanar GaAs detector commenced during the last quarter of the year and initial positive results were obtained w ith alpha- and X -ray sources. T he GaAs detector uses an active 20 p epitaxial layer for charge collection. The charge de­posited in the layer is drifted to collection wells w ith fields as presented in Fig. 96. This experim ent, an M.Sc. thesis topic, is the first step in the development of pixelized charged particle detector systems.L a b o ra to ry facilitiesD uring th is year the laboratory acquired a Varian 200 kV ion-im planter. Also during the year some pa­ram eter (electrical) m easuring equipm ent for device characterization was acquired. T his equipm ent is be­ing commissioned. T he new equipm ent will be used to in troduce F E T stuctu res into the T R IU M F m icrocir­cuit library, thus allowing fu rther circuit in tegration. The group has also been awarded an NSERC S tra te ­gic G ran t to develop two-phase CCDs in GaAs. The laboratory is com m itted, therefore, to device develop­m ent as well as system developm ent using the devices produced in the T R IU M F m icrocircuits laboratory.Fig. 94. E lectrostatic potential maxim um within the CCD channel as a function of position. Energy troughs within the interelectrode gaps are minimized w ith a resistive gate structure or a very narrow gap, resulting in improved device operation.SQUARE WAVE INPUT_ nnnui miiniiTmnmnniTiiHiltllllnniiiTIME DELAYED AND PIXELIZED OUTPUTFig. 95. High-frequency analogue operation of a 32 pixel 4-phase GaAs CCD at approxim ately 100 MHz. The upper trace depicts the input signal and the lower trace depicts the resultant delayed («300 ns) ou tpu t signal.90PixelizedDetectorStructure(not to scale)f l§ in q I D R IFT —• 100 - 5000 micron* ------Schottky drift electrodes1I1iFig. 96. A section of the GaAs particle detector test structure and a calculated field map. The substrate-epi interface is assumed to act as a pn junction. The solid T-shaped structures are 6 ;im wide ohmic sense strips. The squares at upper right are bond pads (100 /im on a side) to which drift voltages are applied.91CYCLOTRON DIVISIONIN T R O D U C T IO NThe cyclotron perform ed reliably during the first half of the year, w ith records achieved in beam production, beam intensity, high dee voltage and lower rf leakage in the beam cavity. T he benefits of recent installations, such as the replacem ent of eight resonator segments w ith b e tte r cooled and more stable units of new de­sign, w ith substan tia lly improved rf diagnostics, were obvious. T he availability of a higher accelerating volt­age a t the dee gap and of a new, m ore stable and in­tense H “ cusp volume source in the new 300 kV ter­m inal m ade it possible to deliver 200 f iA during a one- week-long production test, and to dem onstrate 400 //A peak current in a pulsed beam test a t 50% du ty cy­cle. T he vacuum im provem ent resulting from increased H 2 pum ping through four newly installed cryopum ps (16,000 £/s to ta l) , in com bination w ith the reduced num ber of tu rns required for acceleration due to the higher accelerating voltage, will allow increasing beam production current by m ore th an 20%, w ithout increas­ing cyclotron beam losses.D uring the second half of the year the reliability of beam production and the ra te of progress toward improved cyclotron perform ance could not be m ain­ta ined a t previous high levels. F irstly, a series of an­noying breakdow ns and failures in the rf power am pli­fiers caused increased downtim e. Failures occurred in the in term ediate power amplifier, in the transm ission line and in the o u tp u t power combiner. A pparently un­related , these all occurred a t brief intervals from each other, pointing ou t the need for improved fau lt diag­nostics and controls w ithin the system . R f testing at above routine power levels was suggested as a measure of preventive m aintenance. However, this requires ded­icated cyclotron tim e, preferably during shutdowns, in conflict w ith the necessity of reducing peak energy con­sum ption in shutdow n periods to minimize operating costs.Problem s culm inated a t the end of A ugust when the high voltage transform er feeding the rf system was found shorted to ground. The breakdown was a ttrib u ted to the equipm ent having reached its esti­m ated lifetime, as explained in the report from the RF group. The transform er, a 15-ton 3250 kVA 6-phase outdoor un it, was lifted from site on the day following the breakdow n, taken to a local m anufacturer for struc­tu ra l im provem ent and com plete rebuilding, and rein­stalled and tested on site w ithin less th an one m onth. T he fall shutdow n was advanced so th a t overall loss of beam production was lim ited to a few days. Neverthe­less, the event was disruptive to the experim ents on the floor and to the beam schedule.A second m ajo r problem occurred towards the end of Septem ber during the shutdow n in a tank lid-lowering operation. One of the 24 jacks supporting the upper tank and m agnet s truc tu re developed a sudden failure. T he lower bearing which is a spherical roller th rust bearing failed, allowing the jacking shaft to drop by 13 mm. A fter inspection another un it showed th a t fail­ure of its bearing was im m inent. B oth jacks were re­moved and rebuilt. T he spherical roller bearings were replaced w ith fail safe ball th ru st bearings, and hard­ened jou rnal sleeves were in troduced to react to side loads. T he repair was com pleted w ithin the tim e al­lo tted for the shutdow n and did not cause disruption in beam schedule. Ideally, bearings should have been replaced in all 24 jacks to prevent the dangerous failure mode from occurring in any other un it during possible fu ture lid-raising operations. Due to lack of replace­m ent parts and in order not to interfere w ith the beam production schedule, th is could no t be done during the fall shutdown.To minimize risks it was decided not to lift the lid until the spring 1988 shutdow n unless absolutely re­quired for beam production . R f resonator tip align­m ent and tun ing were in progress when the failure oc­curred in Septem ber, and one or two lid-up iterations were still required in order to reach a stable electro­m agnetic configuration. The resonator tun ing could not be com pleted and the system was left to operate in a slightly unstable and m arginal mode for the rest of the year.Considering the above, it is astonishing th a t the yearly in tegrated production current equalled the record (331 m A h) achieved in 1985. T he to ta l num ­ber of beam production hours was 5194 (see Fig. 97). The reliability factor, defined as hours produced, di­vided by hours scheduled, was 88.5%, about the same as in 1985 and 1986. These results could not have been achieved w ithout the com m endable dedication of operators and of m any other groups and individuals.Substan tia l progress was achieved in key m ajor projects. The Ion Source Injection System group (ISIS) com pleted the insta lla tion and commission­ing of the cusp volume source (13) in the new 300 keV term inal and achieved beam tunes along the 50-m-long injection line corresponding to inten­sities of 2 mA a t the inflector entrance. A t the sam e tim e the new high-intensity optically pum ped92W 1 3 0 - M l l -j - L - i - l- i - i . I I I I I I I I I I [ I I I 3 9 0D 120 ~E 6 .OK 7, . “ 360C/1O : ' c m AHrs/Yr ® 100% 3X 110 5.5K O |||m AH rs/0.25Yr 330 O- : 7 0 / \ ^ i70pA> 100 - 5 .OK D / \ ® 100% 300 ^C E s- / \ 0 - W 0 i a4 « d Ob a/ aaFig. 97. Beam charge delivered and hours of operation over the past twelve years. Milestones in extracted peak are also indicated. The histogram shows the charge delivered per m onth.polarized ion source (14) was assembled in the term inal and the connecting injection line com pleted and ready for cyclotron injection a t the beginning of 1988. P ro­ton currents of 5 f iA , w ith up to 80% polarization, are expected up to 500 MeV during 1988. Higher currents of a t least 30 pA are planned for the following years.The A lternative E x traction Task Force demon­stra ted 90% H~ transm ission through an extracting electrostatic deflector, holding +55 kV, positioned at 450 MeV. A 66 pA peak current was ex tracted w ith 1% du ty cycle. T he separation between transm itted beam and circulating in ternal orbits was about 12 mm, enough to insert a 1-cm-wide cooled m agnetic septum . T he design of the septum m agnetic channel to be in­serted to fu rther separate the outgoing H _ beam from the internal circulating orb its was also completed. Fea­tures of the design are m inim al m agnetic interference w ith in ternal orbits, adequate m echanical rigidity and stability, efficient w ater cooling, rad iation resistance and rem ote handleability. In a parallel effort, the “aux­iliary accelerating cavity” or “r f booster” , which will facilitate H - ex traction and allow reducing cyclotron beam losses by a factor of two to three in the high- energy region, was designed, pro to typed and tested at in term ediate power levels.T he newly form ed “500 //A upgrade” task force was successful in dem onstrating the peak current reported above. Figure 98 shows the history of record cw inten­sities and record pulsed beam peak intensities so far achieved. It is in teresting to note th a t cw current and peak current had, in the last few years, about the same upper lim it. T his could have been in terpreted as ev­idence th a t the m axim um curren t was lim ited a t low energies by inadequate source efficiency or by space charge. Establishing the 400 pA curren t lim it in the pulsed mode has clarified th a t the ion source is not the lim iting factor and th a t space charge is not a problem in the 200-400 pA region. T herm al dam age and radia­tion lim itations have to be overcome in various systems in order to raise routine production currents further. Systems include vertical injection line, central region, extraction foil and supporting m echanism s, beam line m agnets, vacuum seals, ta rget areas and TN F. The task force will address the rem aining problem s in col­laboration w ith the T2 Upgrade task force and with the Rem ote H andling group, w ithin the guidelines and resources established by the next Five-Year Plan.A nother m ajor project aim ed at im proving stability, beam quality and beam reproducibility, as well as al­lowing fast switchover between polarized and unpolar-5.5K 3.5K Ocog2. £.5 K /§1/ / H rs/Yr m AHrs/YrA rs/0.25 r2 0 8 jjA © 100%3170u100%225pA © 10%2 0 5 p A © 10%150 uA 170}jA © 93500 - 450 - ^ 4 0 0 -30 MeVBeam particle protonExternal beam intensity >200 /iAIt was the feeling of a num ber of T R IU M F personnel th a t since all the specialized design skills are available a t TR IU M F, a cyclotron m eeting these requirem ents should be bu ilt locally. A sm all study group was there­fore set up to develop a cyclotron conceptual design and make cost and m anpower estim ates for its con­struction.A high-intensity, low -em ittance H~ ion source is the key to the design of a h igh-current cyclotron for iso­tope production . T he conceptual design th a t evolved during th is study, therefore, is na tu ra lly based on the very successful high-intensity H~ cusp ion source tech­nology recently developed a t T R IU M F. A source ca­pable of H~ curren ts up to 5 mA w ith a normalized em ittance of 0.357T m m .m rad would be used in this case.T he cyclotron itself would be a four-sector compact design w ith 45° rad ial ridge hills, as illustrated in Fig. 107. Two dees located in opposite valleys operate in 0 mode a t 44 MHz, the second harm onic of the orbit frequency. Coaxial stubs to resonate the dees a t the operating frequency pene tra te the yoke through four 20 cm diam eter holes. To m ain tain m agnetic symme­try there are four add itional holes through the yoke in the unoccupied valleys. Tw o of these holes in the lower yoke would be used as vacuum pum p ports, while the o ther two in the upper yoke allow convenient installa­tion and operation of two stripper foil mechanisms for sim ultaneous extraction of two external beams.The design illustra ted minimizes the cyclotron hard­ware around the m id-plane where it m ight be activated by spilled beam , thu s m aking servicing easier.Unlike m any sm all cyclotrons, the final rf power am­plifier is not close coupled to the dees. Instead, the entire 50 kW rf system is located outside the cyclotron vault for easy access and m aintenance. A 15 cm flex­ible coaxial line connected to the drive loop near the end of one of the coaxial stubs delivers the rf power to the dees.Some principal param eters of th is prelim inary con­ceptual design are given in Table XIV.O P E R A T IO N A L SERVICES ElectricalDuring 1987 the ac power supply system s required only regular m aintenance. T he only exception was the air circuit breaker to the rf transform er. Inspected after the rf transform er failure, it was found th a t its arc chutes were severely dam aged and needed replacem ent.109BEAMLINEFig. 107. 30 MeV H cyclotron TRIU M F design.110T able X IV . P rin c ip a l p aram eters o f the T R IU M F 30 MeV H cyclotron.H~15-30 MeV >200 fiA external H~ cusp source 2overall diam eter 2.18 mweight 36 tonnepole diam eter 1.33 mNo. of sectors 4hill gap 4 cmvalley gap 18 cmRave 1.45 TRhill 2.18 Tpower 27 kWfrequency 44 MHzpower 36 kWBeam ionenergybeam current ion sourceNo. of external beamsT heir service life was 8000 operations vs the expected life of 12,000. They were replaced in the fall shu t­down, and bo th m ain m agnet and rf breakers, and re­lated protection devices, serviced. To more evently dis­trib u te the cum ulative num ber of operations between them , the breakers were interchanged. The m ain m ag­net transform er was inspected and coolant sam ple tests indicated norm al conditions.T he energy consum ption for the site am ounted to51.5 G W h. The peak power dem and in the year was 9069 kVA w ith a power factor of 0.96.MechanicalT he air-conditioning system for the control and com­pu ter rooms was studied and the enthalpy controller found to be acting in reverse. T his device selects ou t­side or re tu rn air depending on which of the two has a lower heat content. Selecting 100% outside sum m er air would m ean im possibly high conditioning loads. This was corrected and the air supply rebalanced in the com puter room to reflect the relocation of heat sources. One of the existing acoustic walls was removed to aid air circulation, and Venetian blinds were installed to cut down the light entering the m aster control room.Remote handlingR outine operationsR outine rem ote handling procedures were performed much as usual. In the cyclotron m ajor responsibil­ities included the installa tion of four new resonator segm ents, the electrosta tic deflector for the alternative extraction test, replacem ent of the gate valve in beam line 4, and bo th the high-energy and back-up beam spill m onitors. In the beam lines typical requests were for the installation or exchange of com ponents and re­pairs due to vacuum or water leaks.DevelopmentSeveral im provem ents were im plem ented, and new techniques were developed in the course of the year. In the cyclotron the first two diagnostic devices can now be rem otely removed and reinstalled for servicing - the new first tu rn rad ial flag in the second resonator quadran t, and the new low-energy probe commissioned in the fall. T he installation of the cyclotron shadow shields, repeated once or twice each shutdow n, is now possible from the Rem ote H andling operations room. As a result the rad iation doses to personnel are re­duced.A m ajor effort is directed tow ards developing the capability to rem otely cut openings in the 22 m m thick cyclotron lid and floor to enable installation of new ports for the rf booster in 1988.In the beam lines several com ponents were re­designed and upgraded for b e tte r perform ance and ease of installation. The vacuum box w ith modified flanges in the front end of the M 8 channel, the M il septum m agnet box upstream flange, and the relocation of the beam line 4 vault section are typical examples.I l lH o t cells Liquid helium plantT he dem and on com ponent servicing continued a t an increased level, and the work proceeded smoothly. L ater in the year the hot cell was cleaned ou t and de­contam inated in p repara tion for cell relocation. The m odular cell was then moved to the meson hall ex­tension, and an independent crane rail s truc tu re for servicing the en tire ho t cells facility was erected. The hot cell is now fully operational.The liquefier required m ajo r unscheduled m ainte­nance twice in the year, once due to oil contam ination and once due to a helium leak into the cryostat. These problem s m ade it necessary to purchase liquid from outside sources on two occasions, and also liquid had to be purchased to satisfy dem and in excess of capac­ity. A to ta l of 4500 t was purchased as liquid out of a to ta l of 55,595 I delivered.112EXPERIMENTAL FACILITIES DIVISIONIN T R O D U C T IO NSeveral m ajor projects were com pleted during 1987 which provide new capabilities in the experim ental fa­cilities available a t T R IU M F or enhance existing ones. In the p ro ton hall the pro ject to produce longitudi­nally polarized p ro ton beam s on beam line 4B was the m ajo r activity. D uring the spring shutdow n the two superconducting spin-precision solenoids were in­stalled in the rearranged vault sections of the beam line. T he solenoids were successfully commissioned, and using the new polarim eters in beam lines 4A and 4B the production of polarized protons in any of the three directions (horizontal, vertical or longitudinal) was dem onstrated and the first experim ents using this facility were run.T he MRS spectrom eter had a busy year and the com pletion of the vacuum vessels and beam dum p, together w ith the new open-sided quadrupole on the spectrom eter, now perm its high resolution scatter­ing experim ents down to 2.2°. O ther im provements in shielding and detectors have m ade currents up to 500 nA possible when operating in the CHARGEX mode.T he TISO L (test isotope separator on-line) facil­ity was installed on beam line 4A during the spring shutdow n. T he facility consists of a target/ion-source front-end followed by a QQD analysis system . Sepa­rated beam s of radioactive heavy ions were produced using the 500 MeV pro ton beam and different ion source configurations were tested . T he beam from T I­SOL is now being ben t th rough a fu rther 90° and trans­ported to an area where more shielding exists. This will allow the facility to be used for an initial physics program as well as for source developm ent studies.T he second arm spectrom eter (D A SS/SA SP) design continued to be developed th roughou t the year and by year-end the detailed design of the dipole was well under way. T he SASP spectrom eter, once installed, will essentially com plete a diversified nuclear physics facility in the proton hall. In addition to the longitu­dinal polarization project com pleted th is year, other com ponents which make up th is unique facility are the 4B tw ister which allows the beam to be dispersed in the vertical direction for m om entum m atching, the MRS spectrom eter w ith a focal plane polarim eter and the nucleon charge exchange facility which enables the spectrom eters to be used for (n , p ) and (p, n) studies.Over in the meson hall significant progress was m ade on the superconducting m uon channel project on M9 which is a collaborative effort between T R IU M F andthe University of Tokyo. T he com pressor building was com pleted and the com pressor, cold box and associated services installed. In itia l tests on the refrigeration sys­tem were carried ou t using a dum m y load. M any of the TR IU M F-supplied beam line com ponents are de­livered or well along in fabrication. The solenoid will be shipped here from Jap an next April a t which time the installation of the beam line will begin.T he /iSR facility project is now com plete w ith the delivery and commissioning of the dilution refrigerator which is capable of operation down to about 10 mK. O ther item s constructed as p a rt of th is facility include the Om ni and O m ni' spectrom eters, the high field ap­para tu s and some specialized rf equipm ent. Some of the exciting developm ents in th is area are described elsewhere in th is report. The M20 channel was im­proved for ^S R research, w ith the replacem ent of the high voltage supplies on the dc separator w ith new 400 kV supplies w ith considerably b e tte r stability.W ith the com pletion of studies for the RM C exper­im ent using the rf separated beam on M9, the rf sep­ara to r was removed for im provem ents and the short dc separator installed in its place to provide a clean surface m uon beam . T he Chicago m agnet was disas­sembled in p reparation for the RM C experim ent.T he QQD spectrom eter was used in a large number of experim ents, in m any cases in conjunction w ith an­other detector arm for coincidence experim ents. A new high ra te cham ber developed by the detector group was tested on the M i l channel a t ra tes to 30 M H z/cm 2 and has been used successfully a t the dispersed focus in the channel as an active slit. I t is planned to replace the front-end cham ber on the QQD w ith one of these high ra te cham bers. O ther plans include the use of the PACM AN m agnet as a high acceptance spectrom ­eter for use in low cross-section experim ents. Also in progress are feasibility studies on a new large accep­tance detector (CLASS) for pion experim ents based on a superconducting split pair solenoid.In o ther experim ental support activities progress was m ade on the new VAX-based d a ta acquisition sys­tem for the MRS although there are still some pieces of the software to be developed before initial testing early in the new year. The In strum en ta tion Pool could not be funded a t as high a level as desired, pu ttin g some constrain ts on the beam scheduling and lim iting the num ber of new m odules which could be brought in for evaluation. The meson hall service annex extension (MESA) area of the detector facility was improved with113the addition of a gas shack for counter gas d istribu tion and the clean room was used for several m onths for the stringing of the Brookhaven 787 drift cham ber. The m ain floor of the M ESA was the site of the calorim eter construction for the SLD detector.Both polarized targets were used for a num ber of experim ental runs during the year. T he polarization direction of the deuterium target was ro ta ted to the vertical from the previous horizontal directions. The liquid deuterium neutron production target will be re­placed w ith a new ta rg e t flask which will allow opera­tion a t higher p ro ton currents.In addition to engineering on the projects already m entioned the Engineering group was kept busy w ith a num ber of experim ental support projects, such as m odifications of the PACM AN and Chicago m agnets, a new w ater door for beam line 4A and im provements to beam line 1A. Several m em bers of the E xperim ental Facilities Division were m em bers of a task force which prepared a repo rt on the upgrade of the meson hall ta rg e t sta tions and beam lines for 500 pA operation.All com ponents for the 80 m long HERA transfer line were com pleted a t TR IU M F and shipped to H am ­burg during the sum m er. Except for the commission­ing work a t DESY th is p ro ject is now complete.E X P E R IM E N T A L SU P P O R TN ucleon ics a n d IA CA to ta l of 170 new m odules were added to the In­s trum en ta tion Pool database during 1987, of which the Pool purchased 82. T his is the lowest num ber acquired since 1980.T he repo rt of the Decem ber 1986 Long-Range P lan­ning Com m ittee recom m ended th a t the Instrum enta­tion Pool funding be restored to 1985/86 levels and also placed a high priority on the hiring of an additional technician. However, due to the fiscal restra in ts the In­strum en ta tion Pool was funded a t the lowest level since 1983 and no additional personnel were hired. T he In­strum en ta tion Pool nucleonics upgrade m ajor project received zero funding for 1987/88, as in the previous year. Therefore, no progress was m ade in the evalua­tion or acquisition of program m able trigger logic m od­ules; nor were any additional CAM AC parallel branch highway system s im plem ented.A W ork S tudy studen t perform ed a site-wide inven­tory of the Pool m odules early in the year. Tw o-thirds o f the 4500 m odules on the database were found and their location codes updated on the database. This al­lowed easier reallocation of m odules during the year. To enhance the security of the In strum enta tion Pool repair and storage areas, the locks on the doors werechanged. Experim enters now have to ob tain a key from the m ain control room for access outside norm al work­ing hours. T his has greatly reduced the num ber of undocum ented w ithdraw als of modules from the Pool.Nucleonics requests continued to be a constrain t on beam scheduling. D uring unpolarized beam periods over 95% of the Pool m odules were typically in use. This is the highest level of usage of any m ajor North Am erican In strum enta tion Pool.M. Comyn and W . Miles a ttended the Pool Heads’ A F R E P m eeting a t Brookhaven N ational Laboratory from June 1-15. The m eeting began w ith inform ative one-day visits to LeCroy C orporation and Phillips Sci­entific and a half-day visit to Jorw ay C orporation. The rem ainder of the week was spent a t BNL discussing m atters of m utual concern to the Pools. Q uality con­tro l problem s were discussed in detail as they have been of im m ediate concern to the T R IU M F Instrum entation Pool over the last year.The m ajor evaluation undertaken during the year was the selection of a new Pool S tandard NIM bin and power supply to replace the obsolete 200 W B.L. Packer NB-10/1002 com bination. The LeCroy 1403/1002A, Grenson 7N /V U 5/N PU -11, Grenson 6N /V U 3/N PU -8A , Ortec Black M ax 4001C/4002E and Tennelec T B 4/T C 911 Turbo units were tested and com pared w ith the B.L. Packer NB-10/1002. E lectri­cal and therm al operating characteristics were studied extensively and the overall s tandards of electrical and mechanical engineering were com pared. T he Tennelec un it was first evaluated during a visit to T R IU M F by Tennelec Inc. personnel in June. Extensive discussions w ith the Tennelec engineer, b o th during and after the visit, resulted in m odifications to T R IU M F specifica­tions and im proved perform ance of the un it. After equally exhaustive testing of all of the units, the Ten­nelec un it was considered to be equal to or superior to the others w ith regard to perform ance and, due to novel electrom echanical engineering, easier to m aintain and repair. The T B 4/T C 911 Turbo delivers 336 W dc, 451 W to ta l including 115 V ac. I t was therefore de­fined as the new Pool S tandard . A fter acceptance of the first production un it in November, ten of an or­der for tw enty un its were delivered in December. Once in service these new NIM bins should relieve an acute shortage th a t has existed for the last two years.T he other new Pool S tandard defined in 1987 was the Jorw ay M odel 71B-1 O ptions 2 and 3 Type A- 2 M aster or A uxiliary C rate C ontroller w ith M ailbox M emory and LAM Mask options.A TRIU M F-designed Prescaler NIM m odule was evaluated and im provem ents suggested. A second pro­to type w ith revised, enhanced specifications was under final assembly a t the end of the year.114Several m odules were loaned for use in TR IU M F- related experim ents off site during the year. All re­quests were considered under the new guidelines sug­gested by the In strum en ta tion A dvisory Com m ittee and adopted by T R IU M F a t the beginning of the year.Technical sem inars related to new products were ar­ranged during the year w ith presentations by represen­tatives of Tennelec Inc, Tektronix and LeCroy Corpo­ration .Data acquisition softwareT he year’s progress on com pleting the outstanding p arts o f the VAX software for the new VAX-based MRS CAM AC d a ta acquisition system was slower than an­tic ipated due to the unexpected departure of the only program m er working on the project, in April, and her eventual replacem ent in O ctober. Despite the loss of m anpower significant progress was m ade on com plet­ing the ou tstand ing p arts of the general software sys­tem and beginning a new PC -w orkstation project. An­o ther VAX-11/750 was added to the ranks of the d a ta acquisition com puters to service users in the M il area of the meson hall.The ou tstand ing software item s a t the end of 1986, nam ely a shareable, dynam ic histogram system and a graphics system to display the histogram s, were com­pleted th is year and subject to extended tests. T he his- togram m ing system provides for the dynam ic creation, filling and deletion of histogram s and their storage in VAX disc files. In addition the system allows on-line histogram d a ta to be obtained by any other VAX pro­cess, for display on graphics devices. T he A tari graph­ics display system , developed by Ron Jeppesen, was in­corporated in to the acquisition software to provide for the display of histogram s a t a significantly higher ra te th an w ith existing display software packages. In his design the h istogram d a ta is tran sm itted to the A tari personal com puter, which then transform s it in to the usual display form w ith axes, titles and d a ta values, etc. I t is possible to ob tain a screen dum p of the A tari display by a ttach ing an HP Laserjet p rin ter to the par­allel po rt of the A tari.T he VAX M ULTI system from Ferm ilab was m odi­fied and interfaced to our buffer m anagem ent scheme, used to transfer d a ta between all analysis processes in the VAX host. The m odifications took only a few days and will give the present group of R SX /M U LTI users a fam iliar environm ent to work w ithin when the new system becomes operational in 1988.A pro ject to investigate the u tility of PC s as a graph­ics w orkstations for the MRS d a ta acquisition system was begun in the spring. T his project is complemen­ta ry to the A tari-based graphics system bu t is intended to reach higher display speeds a t lower VAX C PU -tim efor colour displays. A PC -A T clone was purchased with a 30 Mb disc, an ATI EGA com patible display adap­tor, a 3Com E therlink card for E th ern e t attachm ent, Turbo Pascal and D E C ’s D ECnet-D O S. A Turbo PAS­CAL program was designed w ith a VMS DCL-like com­m and interface th a t em ulated the com m ands available to users of the VAX-based d a ta acquisition system , for the display of graphics. T he PC was attached to the site-wide E thernet and is recognised as a DECN ET node by several VAXes. The program establishes a D EC N ET connection to a server program on a VAX and uses the link to ob tain display d a ta from VAX analysis program s, in real tim e. T he d a ta are form at­ted and displayed in colour on the PC . Screen dumps will be available by return ing the screen bit-m ap to the VAX for printing on a laser printer. A t year’s end the PC software was essentially com plete bu t for test pur­poses the VAX software re tu rned self-generated display d a ta ra ther th an true h istogram d a ta from an analy­sis task . T he com pletion of th is la tte r task will take place after extensive testing of the two software compo­nents. Tests dem onstrate th a t the continuous repeti­tive display of a 1000-channel h istogram on the PC can be achieved every 1.5 s (a d a ta transfer ra te of about 2000 by tes/s) and imposes a C PU load of 4%. The equivalent d a ta transfer ra te (approx 19.2 K bits/s) to a term inal requires 40% of the CPU tim e due to the natu re of RS232 interface boards. This confirmed the expected display rates for the pro ject and the expected reduction in CPU usage for displays. The scope of the project will now be widened to encompass more func­tions expected from a w orkstation software package, such as d a ta storage and retrieval, curve fitting, inte­grations, etc.Two papers were presented to the IE E E Real-Time C om puter Conference in M ay covering the graph­ics w orkstation concepts and the buffer m anagem ent scheme for analysis process on the VAX. A nother pa­per was presented to the IE E E Nuclear Science Sympo­sium in O ctober on the TW O TR A N d a ta acquisition language used in the S ta rbu rst front-end processor of the VAX.On the hardw are front the present TPC750::VAX- 11/750 was moved from the T P C shack to the M il counting room as the VAX host for meson hall exper­im ents in the M 13/1B /M 11 areas. I t was equipped w ith a System C rate-based CAM AC system compris­ing a high powered crate, a VAX PTI-11 interface, an AMC-11 unibus DMA transfer un it and an M X-CTR- 3 System C rate controller. A S tarbu rst, its SCI inter­face, a branch coupler and one crate on a 30 ft branch highway were also added to provide a test system for the front-end electronics. A H P Laserjet p rin ter was added to the TPC 750:: for com patability w ith other115VAXes on site. In November the d a ta acquisition sys­tem was installed on the TPC750:: for a one week test on th is host. T he tests revealed d a ta transfer problem s between the S ta rbu rst and the VAX which have been traced to hardw are faults.A micro VAX system was purchased for the d a ta ac­quisition needs of the RM C experim ent. T his was equipped w ith a tapedrive and 300 Mb disc, sim ilar to all o f the three o ther d a ta acquisition system VAXes.In conjunction w ith Peter G reen a specialized ver­sion of the d a ta acquisition system is being prepared for the MRS spectrom eter. The specialized version will relieve users from program m ing standard forms of analysis required by m ost MRS experim ents and pro­vide h istogram s of relevant param eters of in terest to users. Users will in teract w ith a continuously running analysis program via a term inal server program . Us­ing the term inal server program users will be able to modify the analysis perform ed on MRS events and to view the results of histogram m ing the analysed data. A t year’s end the software was well advanced and tests should be an tic ipated early in the new year.In the meson hall a version of the d a ta acquisition system will be prepared to resemble MULTI and in ter­ested experim enters will be coerced in to using the new system .O u tstand ing a t year’s end is the debugging of Sys­tem C rate hardw are involved in d a ta transfer between the S ta rb u rst and the VAX. W ith th is out of the way an operational system can be pressed into service.Detector facilityT he new MESA area of the detector facility is now fully operational. T he gas shack, m ixers and distribu­tion piping is in place. T he testing area on the m ain floor is already fully occupied, w ith several experim ents awaiting space to install and test their equipm ent. T his area will expand in size in early 1988 when the calorim eter construction for the SLD is finished. On the second floor the clean room has been used by m any groups, and has been particu larly useful for the assem­bly and stringing of the drift cham ber of E xpt. 787 a t Brookhaven. T he office space is now fully occupied and a new te rm ina l/com pu ter system has been installed.T his year we have bu ilt m ore th an 200 scintillation counters of m any types and sizes including 30 scintilla­tors for o ther C anadian laboratories. The construction of wire cham bers and p arts for wire cham bers also in­creased th is year to a to ta l of 26.A spectrom eter was purchased and refurbished and has already helped to determ ine the optical quality of light guides used in our detectors. I t will also help to determ ine the optical properties of scintillators pur­chased in the future.Fig. 108. Development work on the fast chamber.T he developm ent activities of our group have in­creased significantly. We have finished construction and initial testing of a very fast gas p roportional wire cham ber (Fig. 108). T his device was operated in M il a t a ra te of 70 MHz w ith efficiencies of about 90%, making it one of the fastest wire cham bers in exis­tence. I t operates w ith a gas m ix ture of C F 4 and isobutane and uses an individual wire readout PCOS system . T his cham ber is now installed as a sem iper­m anent feature in the F2 focus of the M i l channel, and construction of three more sim ilar cham bers for use in o ther secondary channels and in E xpt. 787 at Brookhaven is under way.Extensive studies have been done regarding the ag­ing process in gaseous detectors. T his is a very im­p o rtan t problem , especially in laboratories w ith high intensity machines or where particle fluxes are very high. T he topic has been neglected in the past bu t is now flourishing in several laboratories, and it is related to our efforts w ith the fast cham ber m entioned above. A bench-testing device w ith several sim ilar one-wire cham bers is being used for m easuring the dam age in­duced by high fluxes as a function of gas m ixture, gas gain, gas ra te and m aterials contained in the chamber. Several analyses are used to establish the type of dam ­age and to understand the process involved. Results from th is work and from the fast cham ber tests have been presented a t th is year’s Nuclear Science Sympo­sium. In order to improve our work on wire cham ber damage, we have w ritten and presented, together w ith T E O Research Company, an industria l g ran t request which would allow us to ob ta in a gas chrom atograph and mass spectrom eter, as well as pay the operating costs of th is device and others to fu rther th is research.Work on position-sensitive photom ultipliers and fi­CATHODES0 5cm1—1—1_1_1_1I I< "2 I ,0.76m m -*) [* - 2 T —' H - 5 2 " m CATHODEIZJAm ..................................... ..........................................................2 0 11mAN0DES -----------------------------------”f~_____________________ ANODESCHAMBER I CHAMBER 264 WIRES 32 WIRES116bre scintillators which began some years ago is con­tinuing and one of us has visited the m anufacturers of these devices in Jap an early th is year.We have begun work on a Bragg Curve spectrom e­ter. These devices are drift cham bers for heavy ions, allowing the determ ination of mass and energy sim ulta­neously by m easuring to ta l ionization and track length. These new devices are very useful for some of the ex­perim ents done now a t TR IU M F, and our first pro­to type has already operated successfully, m easuring 5 MeV a-partic les w ith a 80 keV resolution FW HM .This year we in stitu ted two im portan t changes in our charging procedures. We have elim inated the labour costs o f m anufacturing wire cham bers which now makes the process the sam e as for scintillation counters. However, in either case we would expect the experim ental group to pay for manpower if ad­ditional personnel have to be hired to carry out the work. On the o ther hand, we are now charging the us­age of gas obtained from the detector facility (w ith the exception of T R IU M F-supported facilities) for exper­im ents a t T R IU M F. This has reduced som ewhat the gas wastage and we hope it will induce conservation m easures (gas recirculation system s, etc).These two changes have had several consequences. F irst, the budget is now a b e tte r reflection of the costs of detector construction and operation, b o th to T R I­UM F and to the users. Second, it gives the user af­fordable wire cham bers which has already shown in an increased request for cham ber construction, strain ing the m anpower of our group.M W P C facilityT he m ajor activ ity during the first quarter of 1987 was the construction of cham bers for Brookhaven E xpt. 787. We constructed three p lanar cham bers for beam m onitoring and assisted w ith stringing the cen­tra l drift chamber.A second large pro ject th is year was the construc­tion of 4 delay line readout wire cham bers for the QQD spectrom eter. For th is project we developed the abil­ity to produce large p rin ted circuit boards so th a t the cham ber fram es could be fabricated in one piece in­stead of aligning several sections together. We can now produce 60 cm x 90 cm pc boards.Three p ro to type drift cham bers were constructed for the radiative m uon capture (RM C) group. Also for RM C the four large T P C veto drift cham bers were restrung. We have raised the ceiling of a section of the clean room so th a t the RM C drift cham ber can be s trung vertically. T his will allow us to use crim p pins to hold the wires instead of soldered connections.Cleaning and repair of the MRS front-end cham bers continues to be an ongoing project. O ther projectswere fabrication of a delay line readout for a mi- crochannel p late, repair of broken wires in E xpt. 331 cham bers, fabrication of a p ro to type VBCS cham­ber, stringing wire planes for H ERA profile m onitors and assembly of a high-pressure wire cham ber for the charge exchange facility.M E SO N HALLM 9 ch an n el1987 m arked the end of an era for the M9 channel. In May the last beam was taken by the T P C facility, com pleting d a ta and calibration runs for radioactive m uon capture on nuclei (E xpt. 249) and the search for te traneu trons by 4He(7r~7r+ )4N (E xpt. 365). Fol­lowing a short period of studies w ith cosmic-rays the work began to dism antle bo th the detector and the M9 channel.On the detector side the T P C itself and all the trig­gers were removed from the Chicago m agnet so th a t work could begin on m odifying the m agnet. Changes to the m agnet include increasing the gap, reconfigur­ing the coil, adding holes to the end p late for light guides, and rebuilding one of the 200 kW power sup­plies. This is in p reparation for the installation of a new drift cham ber, w ith trigger system and liquid hy­drogen target being developed for a study of radiative m uon capture on hydrogen (E xpt. 452).On the channel side the first steps were taken to­wards the new two-legged M9 upgrade, one leg of which incorporates the superconducting solenoid from the University of Tokyo. The rf spectrom eter was re­moved to begin work on a new tran sm itte r and control system . Most of the channel outside the beam line 1A shielding was removed and replaced by a tem porary short extension incorporating the short dc separator which was used for surface muons as well as some ion beams.W hen the m ajor work on the M9 upgrade is under­taken next spring and sum m er, one leg will replace the old M9 and incorporate the rebuilt rf separator relo­cated to optim ize cloud m uon beam s in the m om entum range 60-70 M eV /c required for E xpt. 452 in the re­built Chicago m agnet. T he second leg will produce low m om entum polarized fj,~ using the new superconduct­ing solenoid. T his m ajo r project is reported elsewhere.M 9 ch an n el u pgradeThis has been a very busy year for the M9 upgrade project. T he compressor building was completed and the compressor, supplied by M YCOM of Japan , was installed and grouted in place. The Sulzer cold box ar­rived in May and was placed close to its final position117on the meson hall floor. P rior to th is installation the M i l cabling and w ater services were moved to a new north-south service corridor. T he high pressure refrig­eration piping interconnecting the compressor and cold box was installed, pressure tested and registered. All control and interlock connections between the refriger­ato r elem ents were m ade.In itia l te s ts of the refrigeration system were carried out in Septem ber w ith engineers from Sulzer, MYCOM and Nippon Sanso in a ttendance. D uring these tests the solenoid was replaced by a dum m y load supplied by the U niversity of Tokyo. The system m et or ex­ceeded all of its design cooling requirem ents and op­erated very sm oothly. U nfortunately, during the 72 h acceptance test it was discovered th a t the cold box was being plugged and th a t th is was due to a high water content in the helium gas. T he source of th is w ater re­m ains unknow n; however, after much effort the system gas and com ponents have been dried and a successful 72 h test is expected to take place in Jan u ary 1988.The solenoid being constructed by the M itsubishi Electric C orporation was delayed due to funding and scheduling problem s. However, all of the m ajor com­ponents were fabricated th is year and assem bly and testing are expected to take place in early 1988 and the solenoid should be delivered in April.T here has been significant progress on the rem ainder of the beam line during th is year. A new optics design was com pleted for the A leg (rf separator leg) in which the separato r was moved upstream to make the op ti­m um separation range 60-70 M eV /c (Fig. 109). The design and fabrication of all m ajor com ponents is well under way. T he fabrication and assembly of the front- end doublet is now substan tially complete, the new extraction bender for the B leg has been constructed and field m apped, the A leg trip le t m agnets are being modified and the existing B i m agnet has been removed from the beam line for required m odifications. In ad­dition, the six quadrupoles for the B leg trip lets have been designed and ordered for delivery in April 1988.T he vacuum system design is now substan tia lly com­plete and m any of the associated vacuum boxes have been designed and fabricated . In particu lar, a pro­to type length of S tar pipe was successfully fabricated. T he control and interlocking of the vacuum system will be done using a M odicon Program m able Logic Con­tro ller which has been installed a t the 264 ft level in the meson hall. T he interlock logic has been w ritten and there rem ains to program the controller.T he m ajo rity of the rad ia tion shield required for the new beam line was designed during th is year. T he de­ta iled design of bo th steel and concrete shielding blocks was com pleted and it is expected th a t bids for their fabrication will be solicited early in the new year.This project will continue on a very tig h t schedule tow ard an installa tion date beginning in April of 1988.M i l ch an nelM il has operated well th is year w ith a busy sched­ule. T he largest blocks of tim e were utilized by po­larized deuterium ta rg e t users, w ith E xpt. 331 (Spin transfer in the nd —► pp reaction) utilizing beam in May and June, and E xpt. 375 (Few-body physics via the 7rd break-up reaction) in December. Experi­m ent 403 (pion absorption on 6Li,12C) com pleted data- taking w ith runs in Jan u ary and July.Shorter blocks of tim e were used by E xpt. 327 ((7r+ ,7r+ 7r_ ) reaction on 160 , 28Si and 40Ca), Expt. 443 (7T+d —► n ~ T +pp), E xpt. 328 (M ulti-nucleon modes of pion absorption in flight on 3He and 4 He) and Expt. 395 (Search for a dibaryon in d(x~ , tt+) X .The channel com ponents ran reliably th is year. New pancake coil sections were installed early in the year in the coils of the dipole 11B2 due to a pin-hole water leak which caused a ground fau lt failure in the previous year.Q Q D sp ec tro m eterNumerous experim ents were successfully perform ed on the QQD spectrom eter during the course of 1987. Many of these experim ents m ade use of a second arm in coincidence w ith the QQD. For the (7r,27r) experi­m ents the second arm consisted of a large solid angle stack of scintillators and wire cham bers dubbed the CARUZ. For another experim ent, involved in a search for a i r N N bound s ta te , the second arm consisted of a small, twelve-element scin tillator stack. The QQD was installed in beam line IB for an experim ent with incident protons as well. R eports on these and other applications of the QQD appear elsewhere in th is re­port.Im provem ents to the QQD itself consisted prim arily of the developm ent of fast wire cham bers for the spec­trom eter front-end. A pro to type cham ber was built and operated directly in the pion beam a t rates exceed­ing 40 MHz for a five-week period w ith no noticeable degradation of perform ance. T he cham ber is read out wire by wire using the PCO S system . The wire spac­ing in th is cham ber is 0.8 m m . A cham ber of th is type will be used in the QQD W C1 position. Installa tion is expected early in 1988, and will allow QQD operation a t higher beam intensities and more forward angles.Also in 1988 we expect to replace the aging trig­ger scintillators dow nstream of the spectrom eter focal plane. Furtherm ore, plans are in m otion for the im ­provem ent of the PACM AN spectrom eter for use in low cross-section pion experim ents. These improve-118BEAMLINE IAFig. 109. Layout of the superconducting muon channel on M9 and modifications to the rf separator leg.119m ents consist of the acquisition of larger focal plane wire cham bers to m atch the larger pole-face gap, new front-end wire cham bers, a helium enclosure, and air pads to facilitate angle changes.Finally, design and feasibility studies are in progress on a novel pion spectrom eter facility, CLASS, which will be used for fu tu re pion experim ents on M i l and M13.M l 5 ch an n elT he only significant developm ent undertaken on the M15 channel in 1987 was to tune for p " between 22 and 29 M eV /c a t the request of Expt. 304 (M uonium - antim uonium conversion). N eutron background stud­ies of the various surface muon channels indicated th a t M15 is the optim al channel for E xpt. 304, if it can deliver even a m odest flux of \i~ for calibra­tion purposes. T he perm anen t m agnet quadrupoles of M15 and the lack of po larity switches on the re­m aining 21 m agnets create some obstacles. How­ever, a tune established by changing the polarities of only 6 m agnets (the four benders, of course, and the quadrupole in the m iddle of each bender pair) gave about 90% of the flux achieved w ith all m agnet po­larities changed (except for the perm anent magnets!): about 3000 s-1 a t 28.5 M eV /c w ith 100 / iA prim ary beam . M easurem ents w ith a so lid-state detector indi­cated th a t the optical quality of the beam was sim i­lar to the positive m uons of M15 in term s of m om en­tu m dispersion, resolution, spot size, etc. This flux is w ithin a factor of two of w hat is expected w ithout the com plication in troduced by the perm anent m agnet quadrupoles.M15 operated w ith high reliability in 1987. A bout 10 h of beam were lost due to an in te rm itten t ground fau lt in the B3 m agnet, which fortunately is easily ac­cessible. T he exact location of the fau lt was never iden­tified, bu t the electrical isolation of the coil leads and headers was improved and appears to have cured the problem . T he very th in (1.5 n) fixed separator win­dow failed due to an im proper venting. This event presented the opportun ity to exam ine these windows for aging and no beam was lost, as this occurred dur­ing a shutdow n. No visible deterioration due to ra­diation , vacuum or heat rad ia ted from the hot sepa­ra to r cathode was apparen t after over 18 m onths of service by th is window. Some im provem ent in cool­ing the transform er diodes of the separator m agnet power supplies was required for sustained operation a t 95% of the design o u tp u t for 90° m uon spin ro ta ­tion; these supplies have perform ed well since being modified.jtSR. fa c ilityThe /iSR facility pro ject was s ta rted in 1984 to de­velop specialized facilities for n SR experim ents on the M15 and M20 channels. T he m ain item s in the facility are the dilution refrigerator (D R ), the O m ni and Omni' spectrom eters, the high field appara tu s, the residual gas analyser and the rf apparatus.The dilution refrigerator (D R) has been commis­sioned and the first experim ents have begun. The DR has a base tem pera tu re of 7 m K which allows studies on m agnetism and diffusion in a tem pera tu re region which are of fundam ental im portance in solid-state physics. For exam ple in the first experim ent com pleted in late December we were able to show for the first tim e th a t the diffusion of the positive m uons in copper slows down below 50 mK. This new and surprising result will be used to test K ondo’s theory on the diffusion of light in terstitia ls in m etals.A 7 T superconducting m agnet, purchased from an equipm ent g ran t from NSERC, will be the heart of the new high field appara tu s. I t is scheduled to arrive on site early in 1988. A t T R IU M F the development of level crossing resonance as a spectroscopic tool in chemical physics and solid-state physics has been pio­neered, using a m agnet borrow ed from the University of Tokyo. The results from T R IU M F were the high­light of the Fourth In ternational Conference on Muon Spin R otation in U ppsala, Sweden. T he new m agnet will give us more th an twice the m agnetic field capabil­ity of the old spectrom eter and will operate a t a small fraction of the cost. T his ap p ara tu s will be used to fully exploit th is new technique to ob tain inform ation on free radicals and hydrogen in sem iconductors not accessible through other conventional techniques.In recent m onths the positive m uon has been shown to be an ideal microscopic probe of in ternal fields in high tem pera tu re oxide superconductors. The new high field appara tus will also play an im portan t role in studying m agnetic penetra tion depths and critical fields of these exciting and technologically im portan t new m aterials.Two m ultipurpose spectrom eters Om ni and Om ni' have now been commissioned and are being used rou­tinely in m ost of the condensed m a tte r physics and chem istry experim ents a t T R IU M F. These spectrom ­eters feature conventional Helm holtz coils and a very adaptab le array of p lastic scintillation counters which can be configured to perform m ost types of muon spin ro ta tion experim ents.M uon rf resonance is a novel and exciting new m ethod to probe electronic s tru c tu re of m atter. A high-powered rf amplifier, purchased from an NSERC equipm ent grant, has been commissioned and is in the120tria l stages. One of advantages of the technique, which is of great in terest to the chem ists as well as physicists, is th a t it allows one to study sta tes of the m uon which form too slowly to be observed by conventional muon spin ro tation .Fundam ental aspects of chemical reactions are being studied in the gas phase using muon spin ro tation . One of the im portan t new technical im provem ents in these experim ents has been the incorporation of a residual gas analyser purchased from the /iSR facility account. This provides a precise and direct m easurem ent of the gas m ixture. I t should be noted th a t o ther (non^SR ) users such as the Targets group and E xpt. 304 have also used th is device.All of the original goals of th is m ajor project have been com pleted except for some developm ents noted above which are being supported by NSERC funds. A m ajor concern, however, is the lack of technical sup­port to effectively operate and m ain tain th is equip­m ent.B eam lin e IBThere were no m ajor additions to the beam line hardw are in 1987, b u t existing appara tus was used in two novel configurations:1) A secondary deuteron beam of good m om en­tu m resolution was produced using beam line IB as a m agnetic channel. D euterons were produced via the pp —*• dir+ reaction, in a C H 2 foil, separated from the prim ary beam by a first beam line bending m agnet, and fu rther analysed in the final bender of the beam line. T he beam was used by E xpts. 190 and 301 to measure reaction losses of deuterons stopping in Nal detectors.2) The QQD spectrom eter was installed for the first tim e in BL1B cave, for E xpt. 460. Fortunately, it proved possible to shoehorn the QQD in to the area w ithout having to remove either the LH2 superstruc­tu re or the “steelhenge” of shielding around the neu­tron irrad iation facility.P R O T O N H A L L Beam line 4BT he m ajor activ ity in 1987 was the installation and rearrangem ent of beam line com ponents to provide longitudinal polarization in beam line 4B. T he ini­tia l studies had shown th a t two 2.4 T m superconduct­ing solenoids and a “ro ta tin g ” quadrupole 4VQ3 were needed to produce com plete longitudinal polarizationin beam line 4B. “R o ta ting” quadrupole m eans th a t for a specific longitudinal tune th is quadrupole will be ro ta ted about the beam axis to a certain angle to ac­com m odate the appropria te phase space ro tation .A t th a t tim e there was no space available to install the two superconducting solenoids and it was clear th a t the vault section of beam line 4 had to move an addi­tional 5° to make the necessary room. This in tu rn m ade it necessary to redesign and rebuild the extrac­tion 4 stripping m echanism .D uring the fall shutdow n of 1986 the vault section of beam line 4 was disassembled. F irst the bender 4VB1 was moved to its new location. A fter th a t, rebuild­ing of the line continued tow ard the com bination m ag­net which was heavily shielded to reduce the radiation fields in the work area. A new pneum atically driven wire cham ber m onitor 4VM2 was installed. A new quadrupole was used in the assem bly of 4VQ3 and its ro ta ting mechanism. The poles of this quadrupole were aligned to high accuracy prior to installation. Again due to space restrictions a C -shaped steering m agnet th a t carries the vault beam blocker in its vacuum ves­sel was designed. To increase steering capability a novel 4-pole steering m agnet was installed upstream of 4VQ3. A lthough the superconducting solenoids were ordered early on it was clear from the beginning th a t they would not be on tim e for the fall 1986 shutdown. Therefore, beam line 4 resum ed operation w ithout them . New extraction p o rt properties were established and new theoretical tunes were produced. Indications are th a t they are adequate a t the higher energies while there appear to be discrepancies a t the lower energies. These discrepancies are determ ined by sta rting w ith a theoretical tune and m easuring the resolution using the MRS and then im proving the tune empirically by changing the quadrupole fields. T he causes of these discrepancies are not yet fully known.In the spring shutdow n of 1987 the two supercon­ducting solenoids were installed (see Fig. 110). Two vault shielding blocks were modified to create a small gap for the lines transferring cryogens from outside the vault to the solenoids over a distance of about 17 m. T he installation was followed im m ediately by the com­missioning of the solenoids which showed th a t they will exceed the in itia l specifications. T he rem ote control system was tested and proved satisfactory. Two new polarim eters, one in beam line 4A and one in line B, now allow the determ ination of all com ponents of po­larization. During operation of beam line 4B two com­ponents (norm al and sideways) are m onitored contin­uously. W ith the task com pleted on tim e and within the budget the new facility now allows the production of longitudinally polarized proton beam s on beam line 4B. All o ther modes of operation of beam lines 4A121Fig. 110. T h e two superconduc ting solenoids in sta lled on beam line 4 for long itud ina l po lariza tion .and 4B have been m aintained. T he first experim ent (E xpt. 431) to successfully use longitudinally polarized protons finished its da ta-tak ing run in November 1987.M R SThe proton spectrom eter system , still known as the M RS, has had another busy and productive year. This is evidenced by the num ber and variety of MRS m ea­surem ents described in the Science section of th is re­port. D em ands for unpolarized beam tim e on the nucleon charge exchange configuration of the facility (CHARGEX) have become a t least as pressing and those for high- resolution operation w ith polarized beam . There have been continued efforts tow ard m ax­im izing the efficiency and productiv ity of the facility.P ro ton scattering m easurem ents a t the smallest scattering angles now enjoy an energy resolution sim­ilar to th a t available a t larger angles 100 keV or bet­ter. T he com pletion of the vacuum vessels and well- shielded beam dum p associated w ith the new open­sided quadrupole m agnet for the spectrom eter now al­lows a central spectrom eter angle as sm all as 4°, result­ing in the edge of the acceptance being a t 2.2°. Since the quadrupole position is the sam e as in large angleconfiguration, the optics rem ain optim ized for resolu­tion and solid angle acceptance. T he bora ted water shielding tank for the beam dum p reduces the room background from therm al neutron capture, to which the delay line wire cham bers in the focal plane po­larim eter are particu larly sensitive.T he efficiency of the front-end cham bers in the pres­ence of large fluxes has been improved w ith the con­struction and installation of additional new electron­ics. Previously, the m ost significant constra in t was the 170 ns pulse pair resolution of the 4291B drift cham ­ber TD Cs. This particu lar factor has been elim inated by the new a lternating routers designed and built at T R IU M F. They share the signals from each wire alter­nately between two T D C channels. To take advantage of this, the pulse-shaping filter networks were modi­fied to perm it triggering a t least on every second beam burst. The result was more th an a factor 2 reduction in the inefficiency a t high ra tes of the wire planes sep­arating the CHARGEX (n,p) ta rget layers.In com bination w ith add itional collim ation on the beam-sweeping dipole, these im provem ents have made it possible to use a beam in tensity of 500 nA at 200 MeV or 100 nA a t 460 MeV w ith single-plane ineffi­ciencies less th an 1%. Also, the program m able prom pt122O R signal available from the routers have m ade it pos­sible to retire some obsolete m odules from the event- trigger electronics.The high-resolution solid angle acceptance of the spectrom eter was increased by the installation of m ag­netic shim s along the edges of the dipole pole faces. Such additions, called Rose shims, are norm ally fas­tened to the pole faces. In the case of the MRS, th is is impossible because of the unfortunate design of the vacuum vessel. I t was found empirically th a t they would work alm ost as well inside the vessel if they were displaced fu rther from the pole edge. It was found th a t a pair of shims, each 1/16 in. thick by 1/2 in. wide, when properly positioned would extend the uniform field region of the dipole by several centim etres a t each edge. T his results in an increase in useful solid angle acceptance of approxim ately 25% a t negligible cost.The software system for d a ta acquisition, known as DACS, continues to evolve despite the aging com puter hardw are upon which it is based. In addition to a variety of user conveniences, im provem ents include a substan tia l increase in the ra te a t which d a ta may be transferred from the CAM AC electronics system .T he code for the CAM AC front-end processor has been rew ritten to take advantage of the pipelining fea­tu re installed in the branch driver some years ago. The system can now read 700 typical MRS events per sec­ond w ith event losses due to dead tim es less th an 50%.This th roughpu t exceeds the bandw idth of the 1600 BPI m agnetic tape system which is capable of only 280 events per second. W ork is proceeding on imple­m enting an E therne t link to the MRS VAX so th a t d a ta may be recorded on high-density tape.A seg m en ted h ig h -p re ssu re gas cell for (n,p) charge exchange ex p e rim en tsThe E xpt. 474 group has constructed and tested in beam a high pressure gas ce ll/detector which serves as a secondary target in the (n , p ) C H A llG EX facil­ity a t the MRS. The prim ary m otivation for building th is cell was the m easurem ent of (n , p ) cross sections for gaseous isotopic targets of 82Kr and 130Xe which m ight explain the re ta rd a tio n of the experim entally observed rates in double /? decay. As a first test of the system we have observed the 20N e(n ,p )20F reac­tion a t E n = 198 MeV and angles of 0° and 6°. This reaction, which involves a less expensive isotope, is in­tended to verify the system atic variation of Gamow- Teller s trength across the (sd) shell predicted by large- scale shell model calculations. O ther proposals involv­ing gaseous targets of 3,4He and 15N have been sub­m itted to the December session of T R IU M F ’s Experi­m ents Evaluations Com m ittee.The gas cell is shown schem atically in Fig. 111. The neutron beam from the prim ary 7Li(p, n )7Be reactionFig. 111. Schematic side view of the high-pressure gas cell used in the m easurem ent of the 20N e(n ,p )20F reaction.123enters the cell from the righ t through a 0.5 m m thick stainless steel window. The h it p a tte rn from five ac­tive detectors (V ,A ,B ,C ,D ) are used to subdivide (n,p) reactions occurring in different p arts of the cell. Each wire cham ber consists of 16 vertical wires separated by 2 m m . T he horizontal positions are determ ined to an accuracy of 4 m m (the wires are joined in pairs at present) and com pared to the traceback from the s tan ­dard front-end wire cham bers dow nstream of the gas cell. T he detector gas consisting of a m ix ture of 90% Ar and 10% C O 2 a t 295 psi absolute flows through the gas box a t a typical ra te of 150 cm3 S T P per m inute. The operating voltage of the counter gas was determ ined to be 4.90 kV a t 295 psi and 1.68 kV a t 15 psi. D etector efficiencies of typically 99% have been observed.The two 3.8 cm long in ternal gas cells containing the isotopic gas are herm etically sealed from the counter gas w ith 25 p th ick welded stainless steel windows. A positive differential pressure of 7 psi above th a t of counter gas ensures a positive curvature of the win­dows.T he incident neutron flux is continuously m onitored using (n ,p) reactions in two C H 2 foils sandwiched be­tween the extrem e detector pairs (V,A) and (C,D). As already adopted in the CHARGEX set-up for seg­m ented solid targets, accurate cross sections relative to th a t for the well-known elem entary H(ra,p) reaction are obtained.T hree separate runs have been used a t each angle to separate the spectral contributions of reactions from the isotopic gas in the cell, and from background pro­duced by the solid m aterials in cell windows and de­tector planes, and by the counter gas. For the two background runs the gas box and the inner cells were filled w ith counter gas a t the sam e pressures of 295 or 15 psi absolute, respectively. From the on-line spec­t ra ob tained in early Jan u ary 1988 peaks arising from Gamow-Teller transitions in the 20N e(n ,p )20F were clearly identified.TISOLA sm all p ro to type isotope separator has been in­stalled onto beam line 4A (in the proton hall) and used successfully to ex trac t separated radioactive heavy ion beam s produced w ith test 500 MeV proton beam . This test isotope separato r (TISOL) is used to perform re­search and developm ent studies related to the proposed accelerated radioactive beam s facility as well as appro­p ria te applied and nuclear physics studies.TISO L has been designed and constructed to pro­duce separated (A,Z) radioisotopic heavy ion beam s at TR IU M F. It consists of a thick ta rg e t/io n source front end which operates a t a high tension of up to 20 kV followed by a vertical m agnetic analysis system com­posed of two m agnetic quadrupoles and a vertical 90° dipole to bring the ex trac ted beam s above the shield­ing blocks. An elevation view of the installed TISOL facility is presented in Fig. 112 (the section after the first focus will be installed in 1988), while a plan view of the TISOL area on beam line 4A including the con­tainm ent room is shown in Fig. 113.CABLE TR A Y SFig. 112. Elevation view of the installed TISOL facility.Fig. 113. P lan view of the TISOL area showing the con­tainm ent area.CO N TR O LS POWERCONTROLS RACKS \ELECTROSTATIC B/LTAPE \BOX \ I > - -■FOCUSH.V.TRUNKDIPOLEB L4A J T 0 1CRYOPUMP JJI J - j[ [D s DIAGNOSTIC SERVICESO.OrtI 1SOL 6.1 mEXP. AREAFARADAY CAGE B ' ^ ' K B ' HIGH,H .V . TRUNK124T he m ilestones for the TISO L facility in 1987 were installa tion on to beam line 4A (M ay), operation off line to produce ion beam s of Rb, Ca, K, and Na us­ing a heated rhenium surface ion source, and then to produce ion beam s of 38K (7.4 m) and 25Na (59 s) in­dicating successful operation of the TISO L facility in an on-line mode w ith the 500 MeV proton beam. Fol­lowing a series of runs w ith th is lim ited type of ion source, a (Bernas-N ier type) p lasm a ion source, de­signed and bu ilt together in collaboration w ith scien­tis ts from M cGill (Foster R adiation L aboratory) and ISO CELE (O rsay), was installed and successfully used both in an off-line and an on-line mode. M easured yields of various radioisotopes ex trac ted as ion beam s a t the focus of the TISO L facility are presented else­where in th is annual repo rt (E xpt. 421).T im e was devoted in 1987 to designing and build­ing an extension to the ion beam line TISO L to allow the beam to be bent 90° and refocused a t a position where more shielding exists. T his would allow exper­im ental m easurem ents while the pro ton beam is on, such studies now inhibited by the neutron flux near the first focus. T his extension is composed entirely of electrostatic elem ents and is expected to be installed early in 1988. This would com plete the first phase of the TISO L facility and allow it to be used to prop­erly m easure and optim ize yields for a wide range of radioisotopes of varying im portance, while assessing w hat im provem ents would be required to upgrade for a sta te of the a rt physics program .Dual arm spectrometer system /second arm spectrometerDuring 1987 the second arm spectrom eter (SASP) moved closer to becom ing a reality. The spectrom e­ter will be located a t the 1AT2 location on beam line 4B, and will be able to operate sim ultaneously in a co­incidence mode w ith the existing MRS spectrom eter. T he nuclear reactions which can be studied w ith such a system are (p, Ip) , (p, nx ) , ( p , p ' n ) , etc in the energy region from 200 to 500 MeV. T he energy resolution of such a dual arm spectrom eter system (DASS) would be on the order of 160 keV. This type of experim ent is not yet possible to do anywhere else in the world. In addi­tion the SASP spectrom eter could also be used by itself to expand the current experim ental program s studying the (p , 7r), (p, n) , and ( n , p ) reactions. The large size of the solid angle and m om entum acceptance of the in­strum ent will greatly improve the d a ta rates for these reactions.T he upda ted design specifications of SASP are given in Table XV and an illustration of the D A SS/S ASP facility is shown in Fig. 114. The curren t specifications listed in the tab le are now very close to those of theT able XV. SA SP specifications.Designed central momentum 660 M eV/cMaximum central mom entum 759 M eV/cM omentum acceptance — 10% to +15% A p/ pSolid angle at —10% Ap/ p 11.2 msr— 5% A p/ p 13.0 msr0% A p/ p 13.5 msr+ 5% A p/p 12.8 msr+10% A p/p 11.6 msr+15% A p/p 10.0 msrResolution at 660 M eV/c(FW HM ) (with 2 m r multiplescattering a t focal plane) 0.02% A p/pD /M 4.70 cm /%Flight path a t 600 M eV/c 7.02 mAngular acceptance:bend plane ±103 mrnonbend plane ±42 mrFocal plane tilt 44.3°Total bend angleOOCT>Angular range 14°-156°Angular resolution(1 mm beam spot with nofront-end chamber 2 mrMaximum target spot size(full acceptance)vertical 10 cmhorizontal 4 cmMinimum opening anglewith MRS 40°with the beam line 14°finished instrum ent as the design is now quite hard­ened.T he design of SASP is bu ilt around a dipole w ith wedged pole pieces resem bling the opening of a clamshell from which the dipole derives its nam e, the “clam shell” . There are in addition two quadrupoles in front of the clamshell w ith shaped pole faces to induce high-order m ultipoles to correct for unw anted optical aberrations. The configuration of the design is referred to as a QQ -Clam . T he m inim um opening angle be­tween the MRS and SASP is 40°. T his opening angle w ith the MRS is achieved by a novel design which al­lows SASP to ro ta te on its own set of circular tracks entirely independent of the MRS pivot. The quads are fixed in place by an overhead cantilever support which allows the quads to pass over the MRS fram e w ithout interference.T he ability to detect protons up to 340 MeV will make the spectrom eter useful as p a rt of the ( n , p ) / ( p , n ) facility. Using SASP instead of the MRS will increase the solid angle of the detector from around125A ZIM U THALIGNM ENTROLLERSL-P O S IT IO NINDICATORFig. 114. Elevation view of the proposed DASS (dual arm spectrom eter system).PROTON HALL ROOF ''■5 .1 m FROM CLAM SHELL EXIT115. Sketch of the detector array at the exit of SASP.TOP SCINTILLATOR OR fERENKOV1262 m sr to 13.5 msr. T he effective target area will also increase by about a factor o f 4 (the SASP target area measures approxim ately 10 cm vertical x 4 cm hor­izontal). For (n , p ) physics, the com bination of both factors m eans th a t the d a ta ra te for the (n , p ) reaction using the SASP spectrom eter could be 27 tim es the d a ta ra te using the MRS.T he large solid angle and the large beam spot accep­tance are notable features of the SASP design. How­ever, o ther features should be noted as well such as the 2 m r sca ttering angle resolution which is possible w ithout using a front-end cham ber (FE C ), the small second-order aberrations involving source position, and the sm all D /M (5 cm%) ratio . T he ability to dispense w ith a FEC will allow b e tte r use of the intense polar­ized beam .T he detector system for the SASP can be concep­tually separated into two basic subsystem s: the tra ­jecto ry m easurem ent and the trigger definition. The tra jec to ry will be determ ined by three vertical drift cham bers (VDC) near the focal surface and an op­tional front-end drift cham ber (FE C ). The trigger will be defined by several plastic scintillators for the d E / d x and T O F , some drift cham ber planes and a Cerenkov counter for the fast pion identification. The design of m ost of the system is determ ined by the envelope of tra jectories emerging from the exit o f the dipole which is shown in Fig. 115 superim posed on a layout of the detector package. T he detector system encompasses the m om entum range from —10% to +15% of the cen­tra l m om entum .T he three VDCs and the FEC will be based on the design of sim ilar devices currently operating on the MRS. The basic event trigger will be a coincidence between the 6-paddle scintillator hodoscope and the upper scintillator. I t will be augm ented by a prom pt signal derived from a selectable region of the E-plane in the lower VDC and, if desired, a p rom pt signal from the FEC.In 1987 an application to NSERC for to ta l funds re­quired to build SASP received thorough reviews from two outside referees as well as an on-site visiting com­m ittee. T he reviews were all strongly unanim ous in favour of the project. U nfortunately NSERC did not have the funds to support the application. S tarting next fiscal year it is anticipated th a t T R IU M F will now a ttem p t to build the SASP dipole, s tand and quadrupoles. T hus NSERC is being asked for funds to purchase the SASP instrum entation such as wire cham bers, counters and fast electronics. In the m ean­tim e the detailed design of SASP is proceeding. It is expected th a t the dipole design can go out for bids in the first quarter of 1988. The current schedule forSASP (dependent on funding) has the spectrom eter as­sembled and ready for com m issioning on Jan . 1, 1990.T he proceedings of the D A SS/SA SP workshop held M arch 17-18, 1986 are now available as TR IU M F re­port TRI-86-1. Copies can be supplied on request.TA R G ETS Polarized Targets(1) Large frozen spin targetThe ta rg e t was operated in beam line 4C for three runs of Expt. 182 in January , M arch and June. Pro­ton polarizations of 80% were routinely obtained with polarizing tim es of four to six hours. T he decay times a t 40 m K and 0.25 T holding field were 500 h for pos­itive polarization and 400 h for negative polarization. Following the June run the ta rg e t was removed from the proton hall and set up in the CRM lab for some repairs and testing aim ed a t decreasing the polarizing tim e w ithout significantly increasing the decay rate in frozen spin operation.(2) Polarized deuteron targetT he target was operated in M i l for two runs of E xpt. 331 during Jan u ary and June. In these runs the target polarization was either longitudinal or trans­verse sideways w ith respect to the incoming pion beam and m axim um polarizations of +33% and -4 2 % were achieved.Following the June run the target was removed from M il . T he superconducting m agnet was ro ta ted to the vertical field configuration, perm itting a vertically po­larized target. T he refrigerator was modified to allow a target ladder to be m ounted in the microwave cavity. This allowed one the ability to place either the po­larized target or a dum m y ta rg e t in the beam , w ith a changeover tim e of about five m inutes. D uring dummy target running the polarization could be kept frozen w ith a decay tim e constant of about 200 h. This ta r­get was operated in M i l for E xpt. 375 during Decem­ber. M axim um polarizations achieved were +28% and —35%. These are less th an those achieved for longitu­dinal polarization, presum ably because in the vertical configuration mode the ta rg e t extends into more inho- mogeneous regions of the m agnetic field.A target basket and N M R could have been fabri­cated to allow protons to be polarized in the target, this being required by E xpt. 441 in Jan u ary 1988. Tar­gets a t 4.2 K indicated th a t a reasonable therm al equi­librium signal could be achieved using the NM R system from the large frozen spin target.127Cryogenic Targets(1) Liquid deuterium neutron production targetT he ta rg e t was operated for the three runs of E xpt. 182 carried ou t in the first ha lf of the year. The target has a serious cold leak during s ta rt-u p which causes the insulation vacuum pressure to rise alm ost to the po in t where the ta rg e t will not operate. Exten­sive leak checking a t room tem peratu re has revealed nothing.Fabrication of the new ta rg e t flask, intended for use a t 5 n A, is nearing com pletion and will be installed in February 1988. I t is hoped this will cure the insulation vacuum problem s.(2) Liquid hydrogen targetsT here are three liquid hydrogen targets a t TR IU M F, w ith services to opera te these targets perm anently in­stalled in BL4A, BL4B, BL1B, M il , M13 and M20. T he targets were operated for a to ta l of six experi­m ental runs during the course of the year, using either liquid hydrogen or liquid deuterium .Late in the year design work for a new liquid hy­drogen ta rg e t for the RM C experim ent recommenced. T he refrigerator and the bulk of the vacuum system com ponents required have been ordered.(3) Liquid helium targetT his ta rg e t can be operated w ith either helium-3 or helium -4 in M i l or M l3. D uring the course of the year it was operated for three experim ental runs in these two beam lines.EXPERIMENTAL FACILITIES ENGINEERING Magnets and beam linesIn the spring shutdow n the two superconducting solenoids m ade by Cryogenic C onsultants were in­stalled and commissioned to com plete the beam line changes required to achieve longitudinal polarization in beam line 4.During the year work has continued on the TISOL beam line. T he perm anent m agnet sextupole was re­ceived from K rupp and built in to the E C R source. W ork has continued on the design of an electrostatic beam line which will bend the particles into the hori­zontal plane. Some com ponents of this extension have been fabricated. A new w ater door has been designed and ordered for the entrance into beam line 4A to re­duce neutron levels originating a t the LD 2 target. This will be installed in January 1988Considerable effort has gone into the M9 supercon­ducting m uon channel. T he compressor sta tion and transfer piping has been installed and tested togetherw ith the controls in p reparation for the solenoid op­eration next spring. T he new M9Q1 has been com­pleted and tested as has the dipole M9BB2. Six 12-inch quadrupoles M9BQ3-8 w ith square probes have been ordered for delivery in the 1988/89 fiscal year. The new steel and concrete shielding blocks to com plete the in­sta lla tion are currently being designed. Vacuum boxes, beam pipes and slit box designs are all completed and these com ponents are being fabricated.W ork has continued th roughout the year on the D A SS/SA SP dipole and prelim inary ideal field d istri­bution by up to 1% were studied and found to be cor­rectable by software corrections in the Ray trace rou­tines. Deflection studies using a F in ite Elem ent anal­ysis showed a reduction in the dipole gap of 0.0006 in. due to m agnetic forces and 0.001 in. due to vacuum forces.T he effects of rose shims and field edge contours were investigated to reduce the weight. I t was not possible to reduce the weight below the 100-ton crane limit, w ithout com prom ising the design. The prelim inary drawings have been sent to prospective suppliers for com m ents on tolerances and m anufacturing m ethods prior to going to final tender early in 1988. Concep­tu a l designs for the front-end quadrupoles have been proposed bu t these rem ain to be detailed.The PACMAN m agnet stan d was modified for two proton hall experim ents and its gap has now been in­creased to 30 cm for experim ent by using removable shims. The stand has been modified for th is new height.The Chicago m agnet has been disassembled and the end plates sent ou t for m odification in p reparation for the RM C experim ent.On the M20 channel new high voltage supplies have been installed for the dc separator. T he supplies are 400 kV, 1 mA Glass m an. These are voltage and cur­ren t regulated and should be much m ore stable than the previous units. Full rem ote control will allow com­puter conditioning during m aintenance periods. The separator vacuum controls are also being upgraded.The M9 channel is in a tem porary s ta te due to the M9 rebuild in progress bu t has the short dc separator installed a t F2 w ith slits and a trip le t downstream . T his arrangem ent is optim ized for providing a clean surface m uon beam .On beam line 1A therm ocouple tem peratu res of 22 m agnets have been supplied to the central control sys­tem . Also, 5 vacuum flanges in the 1AT1 and 1AT2 areas have had therm ocouples installed for improved diagnostics. A section of beam line upstream of 1AT2 (including a window) has been redesigned and will be installed in spring 1988.128Fig. 116. Beam line equipment provided by TRIU M F being in­stalled at DESY.H E R A tra n sfe r lineAll com ponents supplied by T R IU M F on behalf of IP P were delivered to H am burg in Ju ly and Septem ­ber. The m agnets and beam m onitoring sta tions were installed in the tunnels (Fig. 116) in Septem ber. Com­pletion of the vacuum tube and commissioning will take place in early 1988.Earlier in the year all 20 quadrupoles, 2 dipoles and 8 X -Y steering m agnets for the beam line were assem­bled and field m apped. All m agnets m et the necessary specifications. The wire harp m onitors and their actu­ators were assembled in beam m onitoring sta tions and tested . Except for the commissioning work a t DESY th is project, in itia ted in 1985, is now complete.T2 ta rg e t u p g ra d eA task force chaired by A. O tter prepared a report on the upgrade of the T2 target sta tion for 500 f iA op­eration which was presented to the December m eeting of the Long R ange P lanning C om m ittee. The central m andate of the task force was to make a conceptual engineering design study and cost estim ate for the up­grade of the ta rg e t sta tion and secondary channels a tT2 bu t it was found th a t there were additional changes to beam line 1 and the T l ta rget area needed for 500 /zA operation and these were included as well.Several new design concepts were considered for the target shield and arrangem ent of the first elements of the beam lines. Figure 117 shows the present arrange­m ent and Figure 118 shows one of the proposed ar­rangem ents for the m agnets and other com ponents.It was established th a t developm ent work m ust pre­cede a final detail design. T his would establish better rad iation-hard vacuum seals, alternative m agnet de­signs, be tte r beam line diagnostic devices, higher cur­rent targets, etc. T he experim enters should establish the required arrangem ent of beam lines a t an upgraded target and w hether the existing channels should be re­produced w ith larger acceptances or new channel de­signs considered. T he task force concluded th a t M8 should be redesigned w ith a horizontal plane exit from the ta rg e t to ease the servicing problem s.Improved shielding and rem ote handling techniques are required to cope w ith higher rad iation levels and air activation problem s. A new hot cell capable of ac­cepting m agnets is necessary.For 500 i iA operation the whole of beam line 1A in the meson hall should be rebuilt from the vault wall to129Fig. 117. Present arrangem ent of the T2 target area.P e o R S S E .P A S fc E X B L V T Y P e . 'c ‘- V A O IU W TUBE. W IT U FLAKJfiiES BCTWtevJ CC>MPO*J^ nJTS»Fig. 118. One of the proposed arrangem ents of the T2 target area.130the T N F. The schedule and cost estim ates reflect this recom m endation. I t was considered th a t a t least one year of developm ent work would be necessary before a detail design could be sta rted . T he detail design procurem ent and installation would require 3.5 years w ith a six-to-nine m onth installation schedule.T he cost was estim ated to be $13,590,000, including developm ent, new com ponents and 60 m an years of professional and technical manpower.Magnet developmentA m ongst the m any m agnets surveyed and tested were 18 quadrupoles and some steering m agnets for the HERA transfer line a t DESY. The new portab le survey equipm ent was used for the first tim e, to survey in situ a t Brookhaven the large 787 solenoid m agnet. Fabrica­tion of the two longitudinal polarization superconduct­ing solenoids was com pleted and they were installed and commissioned in beam line 4A. They have been cooled down and run several tim es now bu t there are still some problem s in the cooldown procedure which need to be resolved. Several studies were completed on increasing the gap of the Chicago m agnet and of pu ttin g rings of holes in the end caps.Calculations were com pleted on the design of a triplesuperconducting solenoid system , w ith a cold iron yoke for the optically pum ped ion source. A contract has been let w ith Oxford Instrum ents to m anufacture th is m agnet. The schedule for the superconducting solenoid being m anufactured by Cryogenic C onsultants for the fiSR group is about a year late.Pole tip field calculations and engineering design for the Q1 and Q2 m ultipoles for the SASP spectrom e­ter were com pleted, b u t recent changes to the speci­fication for these m agnets may m ean they have to be redesigned.Further cryogenic heat transfer m easurem ents were com pleted to see if a superconducting surface would have a zero em issivity and to test for the proxim ity ef­fect. T he superconducting surface m easurem ents were spoiled by vacuum problem s and will be repeated. We found no evidence of the proxim ity effect a t 4.2 K down to an approxim ate distance of a th ird of a millimetre. In sum m ary our m easurem ents indicate th a t between 77 K and 4.2 K it is best to not use any layers of su­perinsulation bu t to have m inim um em issivity surface which can be as close together as tolerances will al­low. This m eans th a t superconducting m agnets can be m ade bo th cheaper and more com pact. We are working on some other ideas to improve the design of superconducting m agnets and expect to try these out on a sm all superconducting solenoid next year.131ACCELERATOR RESEARCH DIVISIONIN T R O D U C T IO NA lthough activ ity th is year has been dom inated by the KAON Factory there have been other im portan t achievem ents too - acceleration of 400 pA current in the cyclotron w ith an im proved ISIS tune, dem onstra­tion of 90% ex traction efficiency for H_ ions a t 66 pA equivalent cu rren t, and the first operational use of the fibre-optic link to UBC.For the KAON Factory, th is has been a good year, s ta rting w ith the approval of the project in principle by the governm ent of B ritish C olum bia (a com m itm ent to fund the buildings and tunnels a t $87 M) and fin­ishing w ith good news about the prospects for foreign contributions to the funding.T he governm ent of B.C. has given strong support to the project th roughou t the year. Prem ier Van- der Zalm and the m inisters responsible (a t first the Hon. Grace M cC arthy and la ter the Hon. S tan Ha­gen) have em phasized th a t it is the province’s highest p riority am ong possible federal projects for B.C. The Prem ier personally launched a Public Awareness cam­paign w ith a “G ala Evening” in Septem ber, prem iering a special prom otional video and triggering the flood of le tters which is reported to be deluging O ttaw a.On the federal side the M inister of S tate for Science and Technology, the Hon. Frank Oberle, has agreed to a jo in t federal-provincial study of in ternational fund­ing, additional provincial and university partic ipation and economic benefits. A Steering Com m ittee was set up to oversee th is a t the deputy m inister level, and a C anadian delegation was appointed to travel abroad exploring the po ten tia l for foreign financial support. A first set of visits by th is group has revealed the pre­paredness of a t least four countries to consider signifi­cant contributions to the construction cost. Mr. Oberle him self invited other nations to partic ipa te in a speech to the O ECD in Paris.On the technical side a full-scale m agnet power sup­ply circuit has been assembled using m agnets from the dism antled B ritish NINA synchrotron to test the dual­frequency concept. A full-scale p ro to type rf cavity is also under construction. T heoretical studies have in­cluded the effect of space charge on longitudinal mo­tion in the A ccum ulator and Booster, the use of helical snakes for polarized beam in the Driver, and the design of a 99.9% efficient slow extraction system for the Ex­tender. T he la tte r system , requiring 3 extraction ele­m ents, is incom patible w ith the reference lattice; race­track designs seem to be feasible and would provide150 m long stra igh t sections w ith in the sam e circum­ference, w ith some advantages for the C and D rings as well. A secondary beam design study has shown th a t the use of rf separators may be advantageous for 3-6 G eV /c kaon beam s. M ajor studies have also been com pleted on the KAON Factory control system and on various aspects of p ro ject m anagem ent.A num ber of technical consultants jo ined us during the sum m er and a very useful KAON Factory Accel­erator W orkshop was held in A ugust. M ajor topics discussed included rf system s, vacuum pipes and rf shields, and space charge and painting . The workshop also led to an agreem ent on closer collaboration be­tween the LA M PF and T R IU M F accelerator design groups. In itia l topics are P S R commissioning and rf cavity design. A good s ta r t was m ade during the fall w ith rf m easurem ents a t Los Alamos and several rf m eetings, and partic ipa tion in P S R commissioning runs.On the cyclotron a record high current of 420 /zA (50% du ty factor) was achieved w ith the help of a new ISIS tune, com puted to take account of the ex tra space charge. T he observation of a space charge effect - en­ergy broadening - w ith in the cyclotron is also reported in a separate m easurem ent. In support of the 500 /iA upgrade, a comprehensive review of the central region has begun, to include space charge and th ird harm onic operation. One contribution already com plete is an upgrading of the com puter codes which analyse low energy p robe d a ta . T h e G O B L IN code is also being upgraded to take account of electric focusing of the dee gaps more accurately. A num ber of MSU codes have been im plem ented and used in prelim inary de­sign studies for a 30 MeV H _ cyclotron. The possibil­ity of accelerating polarized and unpolarized beam s to 500 MeV sim ultaneously has been explored and various schemes analysed.A new m ilestone was reached in tests of H~ ex­traction from the cyclotron when 90% efficiency was achieved in passing a 66 f iA equivalent beam through the electrostatic sep tum (the rem aining 10% being stripped and safely ex tracted as protons upstream of the septum ). Progress has also been m ade in design of the m agnetic channels.Beam line studies included the use of beam line IB for deuterons, the design of new proton lines for can­cer therapy, studies on the new M9 channel for ra­diative m uon capture, and the resolution of some tu n ­132ing problem s w ith the LA M PF stopped-m uon channel. Beam Line D iagnostics developm ents included testing a p ro to type scanning m onitor, analysing the coating observed on M W IC H arp wires, various calibrations, and design of a test facility to be installed on beam line 4B. A capacitive pick-up is being considered for m easuring beam curren t a t the TN F.C om puting Services have p u t considerable effort into supporting the now ubiquitous A tari; installation of the rem ote PAXC shelf has provided sixteen 9600 bd ports to UBC, m aking the first regular operational use of the optical fibre link; another fibre pair has been successfully tested a t 1 M bd for the TR IU M F arm of BCnet; real-tim e displays have been developed for the cyclotron control room to show the effects of tr im coil tun ing on particle phase and vertical beam profile; and a secretarial tra in ing program m e has been provided in LATEX and has proved popular and successful - as exemplified by th is report.Eleven papers were presented in February a t the In­ternational W orkshop on H adron Facility Technology in Santa Fe. Ten papers were presented a t the P a r­ticle A ccelerator Conference in W ashington, D .C ., in M arch. In addition a num ber of presentations were m ade to the Accelerator P lanning C om m ittee, which had its first m eeting a t the end of July, and to the C anadian A ccelerator Conference which had its fourth m eeting a t T R IU M F in Septem ber.B E A M D E V E L O P M E N T C y clo tro n ISISA new record of 420 pA equivalent (50% du ty factor) was ex tracted from the cyclotron. This was achieved using the new high in tensity “cusp” source (a t 1 mA) and tran sp o rt line. T he tran sp o rt line consists of four m atching quadrupoles followed by a periodic section. The com puter code T R A N S O P T R was used to find strengths for the m atching quads. Profile m onitors confirmed th a t the calculated settings indeed m atched the beam to the periodic channel. T R A N SO PT R is m ore useful in th is application th an TR A N SPO R T since it is capable of finding fits in the presence of space charge forces. A t an in tensity of 1 mA, space charge has a significant effect on the beam optics: it depresses the phase advance per cell in the periodic section to 76 from 90.Space charge neu tralizationT he H _ beam from the cusp source has been used to study space charge neutralization a t 15 keV. Em it-tance figures have been m easured as a function of back­ground gas pressure a t either end of a d rift region. The d a ta show th a t for a pressure of a few 10~7 Torr, the neutralization is near 90% while for pressures greater th an 10-4 Torr there is overcom pensation, i.e. a net focusing effect occurs.Inflector m atchingW ith an ion source em ittance of b e tte r th an 0.27T m m -m rad (norm alized) it is, in principle, possible to achieve a m om entum spread of the ex trac ted beam of 0.06% full w idth. In fact, during high intensity run­ning, we have never achieved a spread b e tte r th an 0.2% in beam line 4; values of 0.3% are more typical for sp lit ratios (BL4 c u rre n t/B L l curren t) less th an 10- 5 . This m eans th a t the em ittance of the beam circulating in the cyclotron is m ore th an an order of m agnitude worse th an th a t of the beam from the source. Em it­tance growth occurs in the spiral inflector because of the strong coupling between the two transverse sub­spaces and because of the en try of the beam into the cy­clotron m agnetic field. Moreover, if the injected beam is not m atched to the cyclotron eigen-ellipse, a very large em ittance increase will occur because particles a t different rf phases take different am ounts of turns to reach extraction. W ith a view to redesigning the optics in the region ju s t before the inflector, we have begun a study on minim izing em ittance growth due to these three effects.Central regionThe installation of a second im proved low energy probe (L E I) in the Septem ber shutdow n provided an additional probe for centring work in the central re­gion. M easurem ents were m ade of the inner lim it of travel for the probe (as it was installed in the tank) to ensure accuracy of the rad ial position m easurem ents in the first few tu rns. T he d a ta for th is probe has been included in the cyclotron VAX program s, which aid the centring of the beam in the first 10 tu rns. In addition, these program s have been upgraded to be less sensitive to noise when determ ining the location of the peaks in the tu rn pa tte rn , and the ability to delete or add peaks interactively has been added.A program of central region calculations, required to support the goal of 500 pA operation has been de­veloped. The aim of these calculations is to examine the beam dynam ics of the central region for possible im pedim ents to operation a t 500 pA , and to examine the consequences of such operation on the cyclotron, and on the beam delivered to the users. Some of the item s in the program include:• effects of space charge on the cyclotron acceptance,133• bunching in the ISIS line,• effects of increased dee-voltage (in particu lar on the tim e structu re in BL1A),• effects o f 500 n A operation on A p / p in BL4B,• use of cooled slits in the central region at high current,• studies of unbunched operation,• th ird harm onic operation,• reduction of beam dynam ics related spills in the cyclotron.Short-term beam stabilityT he proposed KAON Factory accum ulates the T R I­UM F beam over periods of 20 ms. During each period the beam is steered to populate different regions of phase space. Should the beam be absent, or should significant in tensity fluctuations occur for periods of, say, 1 ms then the final accum ulated d istribu tion may be significantly d istorted.T he beam curren t in beam line 1A was m easured by em ploying dc restoration and filtering to the signal from a capacitive probe. T he amplifier rise and fall tim e was 25 //s. D ata were taken for sam pling periods of 4 (is, 100 /is and 1 ms synchronized to the ISIS beam pulser. In tensity ripple of ~1% was observed. Deep dropouts lasting ~ 50 ms occurred roughly once every 5 m in (Fig. 119); operators felt th a t these were due to steering changes th rough the ISIS skimmers. P lasm a oscillations were induced in the ion source bu t no fluctuation in ex tracted beam curren t was seen at frequencies less th an the 25 ps resolution.Revised stripped beam trajectoriesD uring the spring shutdow n the vault section of beam line 4 was ro ta ted 5° about the com bination m ag­net in order to provide a longitudinally polarized beam facility. T he location of the beam line 4 stripper foil positions was recalculated and the operating transfer m atrix param eters of the new beam line rem easured. In addition the field outside exit horn 2, which was m easured for the A lternative E xtraction Systems Task Force, was incorporated into the STR IPU B C program and new calculations m ade for beam line 2B extraction between 100-200 MeV.Cyclotron orbit codesThe general o rb it tracking code GOBLIN has been thoroughly reviewed. Some historical irrelevancies were removed, some errors in logic corrected, and some useful new features were added. Proper docum entation is alm ost com plete. In addition, up to 10 user-defined (R,0) windows have been added. T heir im m ediate useT I M E ( n s )Fig. 119. Example of a beam dropout originating in the ion source or injection system. The beam was steady at 137 f iA for more than 5 min before this event.is to model the behaviour of ex traction elem ents. Each window region m ay contain local electric and m agnetic fields th a t are defined by a user-w ritten subroutine. As well, the R-K in tegration step size m ay be varied w ithin a window to accom m odate rapidly varying fields.A cross com parison was m ade of the revised GOB­LIN calculating orb its in the MSU K500 cyclotron field for 30 M eV /am u 12C 3+ and SPR G A PZ calulating or­bits in the T R IU M F field. T he difference in the cal­culation of the rad ial position a t any azim uth was less th an 0.05 m m . T he height of a 25 m m vertical oscilla­tion differed by 0.15 m m . T his was ascribed to different procedures used for the in terpolation in the m agnetic field, and the calculation of the field derivatives.Simultaneous polarized and unpolarized beamsA prelim inary study was m ade of the feasibility of running the cyclotron in a m ode where polarized and unpolarized beam s are interleaved. Since the present cyclotron operating lim its are set by average current considerations, increased facility use could perhaps be achieved by running polarized and high intensity un­polarized beam s sim ultaneously. I t should be noted th a t these schemes do no t increase the available beam tim e, b u t ra ther allow the possibility of trad ing unpo­larized running in beam line 4 for polarized running in th a t beam line. T hus to proceed w ith such a scheme it would be necessary to show th a t there is a much larger dem and for polarized tim e th an unpolarized tim e.Tw o different tim e structu res were identified. The first would involve interleaving on a bunch-to-bunch basis, the second on a m uch longer tim e scale, say, a millisecond. The selection of the sw itching frequency134Fig. 120. Com puted median plane shifts as each of the seven deflectors is switched on in turn.is lim ited a t the low frequency end by, am ong other things, the therm al ra ting of the targets and the s trip ­ping foils. A t the high frequency end it is lim ited by such considerations as the tun ing tim e of the bunches. Therefore a sw itching frequency in the range of a few kilohertz to a few hertz is preferred. M ethods th a t would interleave bunches were also exam ined. In this case the fifth harm onic operation of the cyclotron m eans th a t the only possible bunch sequences are pp b lank pp or pp b lank pp. These would bo th result in a 20% reduction in du ty factor. Also such a scheme would require an rf deflector in the cyclotron tan k and an rf deflector in the ISIS line, b o th of which would be costly and difficult devices to build. For these reasons the low frequency switching is preferred.The separation of the two beam s a t extraction would be done by shifting the polarized beam off the m edian plane of the cyclotron. T his could be done in a num ber of ways, bu t to avoid degrading the beam quality the best m ethod would be using a vertical electric deflec­to r in front of the stripping foil. Fig. 120 illustrates th a t a m edian plane displacem ent of > 0.2 in. can be achieved w ith an electric field of 15 kV /in . extending over 4° azim uthally a t the ex traction radius. By using a set of seven overlapping plates, extending from r = 230 in. to r = 300 in., beam s in the operating range of 200-480 MeV could be extracted . Design of such a resonant deflector does no t appear to be a very difficult technological problem .If, in the fu ture, the scheduling of beam tim e could benefit from such a system , then fu rther work would be necessary to determ ine the optics required a t the location of the ISIS deflector. T he details of this study are presented in TRI-DN-87-32.Alternative extractionExperim ental testsA fu rther set of experim ents using the v r = 1.5 res­onance driver and the electrosta tic deflector w ith pos­itive deflecting voltage were perform ed in the spring of 1987. The layout of the equipm ent in the cyclotron vacuum cham ber was the sam e as for the measure­m ents reported in previous years. T hey had been af­fected by a dam aged insu lator lim iting the maxim um voltage on the resonance driver and by a broken drive m echanism for the electrostatic deflector which con­strained the position of the sep tum to a less th an op­tim um m im inum in density. T he m easurem ents were m ade w ith a 0.66 p A beam a t 1% du ty factor (peak intensity of 66 pA) . A rad ial scan w ith the differential probe HE2 (Fig. 121) shows the beam intensity mod­ulation produced by the resonance driver, the gap in the beam caused by the sep tum protection foil and the septum itself, and the deflected beam let representing about 90% of the to ta l circulating beam . The DCD m axim um voltage was +55 kV, b u t m aintaining this proved to be more difficult as the tests progressed. The tranm ission m easurem ents w ith electrostatic sep­tu m alone and pro tection foil removed allowed us to estim ate an effective septum w idth of 0.5 mm.Im provem ents to the electrostatic deflectorT he sep tum of the electrosta tic deflector is m ade of tensioned m etal strips 0.25 in. wide, spaced 0.05 in. ap art to ensure flatness and uniform ity. Originally, m olybdenum strips cut by an electron beam technique were used. The edges were found to be very sharp,Fig. 121. Differential and integral probe scans made at the exit of the electrostatic channel. The curve D I / D R is the current seen on a 1.25 mm finger. This drops to zero in the shadow of the septum and rises as the finger intercepts the extracted beam let.135explaining the observed high electron current load to the DCD originating from field emission. A two- dim ensional relaxation code was used to investigate th is problem and the results showed th a t a strip ge­om etry w ith an edge radius of curvature of 0.04 m m would give a peak field of 0 .2 x l0 6 V /cm . This is well below the field emission criterion of between 106 and 107 V /cm . C onsequently stainless steel foils w ith well- polished edges were installed and have operated a t much higher voltages.M agnetic channelThe field produced by the m agnetic channel has been calculated by m eans of the three-dim ensional code GFUN. T his code includes effects of iron w ith varying perm eability. I t was shown th a t th is has little effect on the details o f the field produced by the channel; how­ever, the code was retained for B iot-Savart calculations because the program struc tu re allows coils of compli­cated shape to be described in term s of model segment param eters. C alculations m ade in planes above or be­low the channel were com pared to fields calculated by expansion of the m id-plane field. T he aim was to test the range of validity of the expansion in the steep gra­dients o f the channel. Large local discrepancies were traced to two errors in GFU N routines applicable to racetrack coils. One error was corrected and the other circum vented by the use of an alternative description of the coil geom etry. The field and expansion now agree to w ithin 0.2 m T.O rbit calculations in the now-accurate fringe field showed a vertical beam excursion of 15 m m . This was sufficiently gradual so as not to d istort the em it- tance b u t is too large to be acceptable. Consequently a coil w ith a revised, sym m etric design has been pursued (Fig. 122).The trim coil conductors were moved closer towards the cyclotron centre to reduce the d B z3 / dr com ponent a t the vr = 3 /2 resonance. T he relative strengths of the sep tum coil and cancellation coil were balanced to minimize the field gradient in the fringe field and also w ithin the channel to provide an acceptable change in em ittance ellipse shape. H orizontal phase space is stretched by 20%, while vz is reduced from a m inim um 0.2 w ith no channel to 0.16 w ith the channel powered. T he vertical equilibrium orb it shifts by <2.5 m m for a 6.3 m m vertical displacem ent of the channel and the phase slip is not m ore th an 3° in the fringe field of the channel.Two-dim ensional calculations were perform ed to de­term ine the m echanical specifications for m anufacture. T he positioning of the sep tum conductors near the me­dian plane is the m ost im p o rtan t param eter and the tolerance on horizontal position w ith respect to eachPLANEOF0) ASYMMETRICFig. 122. Cross section through the septum coil of the magnetic channel showing the service bridge arms, (a) Old asymmetric coil, (b) new sym m etric design w ith 20% re­duction in vertical extent.of the o ther conductors is 0.5 m m in order to avoid excessive local B r fields.Beam dynam ics of ex trac tionThe beam optics associated w ith the beam crossing the fringe field of the cyclotron and passing into the exit horn has been investigated w ith GOBLIN. In one scheme four m agnetic channels were used to lead the H_ beam into the ex traction line (Fig. 123). In the initial study the m agnetic channels were assum ed toFig. 123. Trajectory of the extracted H~ beam, showing the magnetic channels (MC1-4) and the auxiliary accelerating cavity (AAC2).BRIDGEFEEDTHROUGH"*^ B E A M/ B 0 T T 0 MBRIDGE136add no gradients or B r com ponents to the existing cy­clotron field. Several particles were tracked through the channels and exit horn II. T he particles defined a rad ial and vertical em ittance of 2tt m m -m rad each w ith an energy spread of ± 0 .7 MeV. S trong radial defocusing forces were observed as the beam crossed the m ain m agnet excitation coil. T he addition of a strong (20 m T /cm ) radially focusing gradient in the fourth m agnetic channel precom pensates th is defocus­ing force. Some additional focusing will be required dow nstream of the exit horn to help m atch the beam to the transfer line to the post-accelerator. This work m ust now be combined w ith a design study on the h igher-strength m agnetic channels to determ ine w hat gradients are possible and also co-ordinated w ith the design of the transfer line.P rim a ry b ea m lin esD eu te ro n p ro d u ctio n on b ea m lin e IBEarly th is year a group of experim enters required a deuteron beam on beam line IB . T heir goal was the de­term ination of nuclear reaction losses when deuterons were stopped in scintillation detectors. T he optics of the beam line were revised and, w ith a crude produc­tion m echanism, a 294 MeV deuteron beam was pro­vided. T he success of the experim ent and the agree­m ent between theoretical and experim ental d a ta led to the proposal for the production of a cleaner deuteron beam on the beam line.I t is proposed th a t a th in CH 2 ta rget be located in a m onitor box upstream of the first dipole in the Vault section of beam line 1. W ith th a t dipole set to trans­m it deuterons to beam line IB , upstream quadru- poles are adjusted to focus the prim ary proton beam on a beam -stop located in a m onitor box dow nstream of the dipole. The subsequent quadrupoles and (two) dipoles are tuned to tran sm it the secondary deuteron beam to the 1BT1 target location. Because the deuterons have slightly higher m om entum th an the secondary protons, the la tte r may be stopped in a second beam blocker located a t a focus between the two dipoles. For a 0.5 m m C H 2 production target the calculated flux of 294 MeV deuterons a t the 1BT1 target is 8 8 /s /n A of prim ary beam ; th a t of 200 MeV deuterons is estim ated a t 3 8 /s /n A of prim ary beam.P o ssib le p ro to n th erap y b eam lin esT he success of the pion therapy program a t T R I­UMF has led to a renewed request for a study of the feasibility of a pro ton therapy beam line. Such a study was begun in m id-year and is continuing. A lthough ini­tia l ly aim ed a t the trea tm en t of eye m elanom a (whichwould require beam s of 70 MeV or less), provision of a beam whose upper energy is in the region of 250 MeV is being investigated.For lower energy beam s (<120 MeV), the existing beam line 2C is ideal. Such beam s can readily be ex­trac ted into the beam line IB cave w ith no changes to the beam line configuration. (Indeed, th is beam line is currently being used in prelim inary studies of the use­fulness of high-energy neutrons in therapy.) Assuming a trea tm en t facility for eye tum ours sim ilar to th a t at Harvard and SIN were available, a su itable beam line to th a t facility would require only the addition of a quadrupole doublet and safety and m onitoring items.Provision of higher-energy beam s which would be available on dem and to a trea tm en t area is somewhat more difficult. One possibility which has been consid­ered is the use of beam line 2B. It has been shown th a t proton beam s of energies between 100 MeV and 200 MeV can be ex tracted from this port. However, beam line 2B is located between beam lines 2C and 2A and the la tte r is the ex trac tion port from which the KAON factory will be fed. It is not yet clear th a t extraction of the H~ beam to the KAON factory is com patible w ith extraction of variable energy beam s from extraction port 2B. Were th is possible, however, several schemes have been devised by which beam s ranging from 70 MeV to 200 MeV could be directed to one location in the beam line IB cave.Because of the uncerta in ty of the requirem ents for extraction of beam to the KAON factory, consideration is also being given to the ex traction of a beam of energy fixed between 200 MeV and 250 MeV; this beam would then be degraded to the energy required for treatm ent. In addition , because of the conflict w ith physics exper­im ents in the IB experim ental area, schemes are being developed to deliver proton beam s to an external ther­apy facility.H " e x tr a c tio n on b ea m lin e 2AThe original design for beam line 2A was based on the assum ption of the extraction of a proton beam . W ith the decision to feed the KAON factory w ith an H _ beam it becam e necessary to redesign th is beam line because extraction properties of H _ ions differ from those of protons and electric stripping of the H~ beam in beam line dipoles now becomes a problem. T his year calculations of the properties expected of the extracted H~ beam becam e available and redesign of the beam line began. In order to avoid the extracted H _ beam striking either the yoke of the cyclotron or one of the jacks used to lift the vacuum tank , a mag­netic channel is placed inside the ex traction horn. Two schemes, one in ternal and one external to the vault, were found to tran sp o rt the beam to the Accum ulator137ring. These are shown in Fig. 124. Each of these de­signs provides a doubly achrom atic beam a t the exit of the second dipole.T he m erit of the in ternal line is th a t it does not in­terfere w ith physics experim ents in the beam line IB area. Further, it requires fewer elem ents and is there­fore less costly. On the o ther hand, the first dipole of the beam line m ust be of a design such th a t the jacking post m ay be cleared. In addition, should the extraction energy be raised above (the design energy of) 450 MeV, the dipole fields, and not their lengths, m ust be increased because of the lack of space in the vault. T h is will increase beam loss caused by elec­tric stripping. The beam line which passes through the vault wall in to the IB experim ental area has more com ponents b u t there is sufficient space available th a t the lengths of the dipoles can be increased should the ex traction energy be raised. T hus beam loss from elec­tric stripping m ay be kept low. However, installation of th is beam line would clearly restrict, if not prohibit, experim entation in the present IB target room.Because of these objections an a ttem p t has begun to design a beam line of which the first section passes through the m agnet yoke a n d /o r between it and the jacking post. T he m erit of such a beam line is th a t significantly smaller bend angles are required to direct beam to the A ccum ulator. T hus bo th the dipoles and their fields can be sm aller reducing bo th beam spill from electric stripp ing and cost.T he region in the horn area required by the m agnetic channels in the configurations shown in Fig. 124 covers the region required for ex trac tion of all bu t 200 MeV from extraction po rt 2B. An extraction line for beam line 2A which passes th rough the m agnet yoke would, in principle, allow sim ultaneous ex traction from each of beam lines 2A, 2B and 2C.S econ d ary ch an n els M 9 ch an nelThe proposed M9 channel has two legs. One leg con­ta ins a superconducting solenoid for the production of a low-m om entum polarized negative-m uon beam. T he other leg coincides w ith the present M9 after the present B2 and contains an rf separator used to de­liver a clean cloud beam to the T P C a t 77 M eV/c. T his leg will in fu tu re be used m ainly for radiative m uon capture in hydrogen. A lower m om entum of 65 M eV /c tu rns ou t to be advantageous. The rf sep­a ra to r has to be placed fu rther upstream in order to ob tain the proper time-of-flight relationships between electrons, pions and m uons a t 65 M eV /c. A tune has been m ade for a new layout for th is situation whichFig. 124. Possible transfer lines to the Accum ulator ring.gives as good beam characteristics as the layout re­quired for 77 M eV /c.S to p p e d m u on ch an n el at L A M P FThe stopped m uon channel a t LA M PF was origi­nally designed to produce decay m uon beam s and was la ter adapted for the tran sp o rt of surface muons. The channel will now be used for the M EGA rare decay ex­perim ent which aim s to bring the branching ra tio for the decay /r —* e+~f down to the 10-13 level. A high- quality surface m uon beam is required. Therefore, a big effort was m ade to understand the optics of the channel a t a high level of sophistication. Recent tu n ­ing runs in parallel w ith our theoretical calculations have now advanced the understanding of the channel to the point th a t one can sim ply set the m agnet cur­rents to the theoretical values in order to ob tain a small beam spot a t the final focus. T his is possible for two different tunes. T he experim ental spot sizes agree w ith the theory. However, the experim ental m om entum bite for one of the tunes seems substan tia lly sm aller than the theoretical prediction.T he influence of the in terplay of the proton beam and the shape of the p roduction ta rg e t has also been investigated. I t was found th a t proper positioning of the proton beam can improve the in tensity by 30%. However, in th is case about 15% of the proton beam misses the target. A fu tu re effort to decrease the size of the proton beam on the target will therefore be useful and will increase the in tensity even more. At present there are about 108p + / s for a 1 mA proton beam.138Fig. 125. Sketch of scanning wire mechanism.B E A M L I N E D I A G N O S T I C S S can n in g p rofile m on itorT he m easurem ent of the secondary emission current from a wire or blade scanned through a beam can give a more accurate description of beam profiles th an the sta tic harps currently employed. A suitable m echa­nism, which fits into existing m onitor boxes, is shown in Fig. 125. An alum inum blade, 10 m m long and 0.25 m m wide, gave profiles w ith a spatia l resolution of0.5 m m and electrical noise equivalent to <1 nA beam current. T he noise was reduced to th is level by utilis­ing R G 174/U coaxial cable inside the m onitor box to elim inate electrostatic noise generated by wire flexing, and by removing bias wires adjacent to the signal wire and replacing them by a sta tionary ring before and af­ter the blade to provide a clearing field. 60 Hz noise was cancelled by the use of shielded tw in-ax cable and a balanced differential amplifier. A 60 Hz filter could not be used since a 300 Hz bandw idth was required. The m echanism illustra ted in Fig. 125 has operated in the beam line on several occasions and on the bench under vacuum for 5 x 105 cycles.For the more intense beam currents the blade was re­placed by a 0.125 m m gold-plated m olybdenum wire. Profiles were m easured a t beam intensities of 150 pA. T he first scans thus m ade displayed a broad base un­der the expected narrow peak. T he behaviour of the background is much more strongly affected by the bias voltage and is ascribed to low energy (~100 eV) ions from residual gas, which will be collected by the wire w ith 100% efficiency. Profiles taken as the beam line pressure was allowed to rise (Fig. 126) confirmed th a t the beam com ponent stays the sam e while the back­ground rises. These studies also show th a t the clearing field from a 300 V bias is necessary a t the usual oper­ating pressure.For the case where harps cannot readily be replaced for some tim e a software program has been w ritten which scans the beam across a single s ta tionary wire. Provided th a t the beam is sm all enough to be steered clear of the wire on bo th sides, a profile m easurem ent may be obtained. U nfortunately th is can only be done a t relatively low currents to avoid excessive spill. D ata have been obtained a t ~ 10 pA intensity.R ad ia tion effectsT he wires of the harps eventually develop a coat­ing in a tim e which is proportional to beam exposure and general radioactive environm ent. T he coating ap­pears to act as an insulator, charging up and deflecting ions to neighbouring wires. A scanning electron mi­croscope was used to ob tain X-ray spectra of the wire and coating. Samples of gold-plated tungsten wires showed a 7 p m deposit of chlorine and silica. Gold- p lated m olybdenum wires showed a 3 p m deposit of alum inum , chlorine and tin .A gas-filled ion cham ber s itua ted ju s t outside the cyclotron vacuum tan k and used as a backup to the scraper-foil spill m onitor eventually showed a resis­tance to the flow of the working gas, which was 90%R E L A T I V E U I R E D I S P L R C E M E N T ( c m )Fig. 126. Scanning wire beam profiles at different gas pres­sures. The lower trace was taken w ith +350 V at less than 15 mTorr, the upper trace w ith +200 V at 18 mTorr, 3 pA cw beam.139argon and 10% carbon dioxide. W hen the ion cham­ber was removed for servicing it was found th a t cop­per gas lines and brass fittings were encrusted w ith a blue-green deposit which im peded gas flow. A naly­sis showed the presence of beryllium , indium , zinc and cobalt. T he encrusta tion is assum ed to be enhanced by the beam -induced breakdow n of carbon dioxide into chemically active carbon monoxide or O J • D uring the next running period helium will be tried as a working gas, since radiolysis p roducts are less severe. I t may be necessary to flush such a m onitor clear of helium before doing any leak checking in the vicinity of the m onitor during m aintenance periods.E q u ip m en t d ev e lo p m en t an d te s t fac ilityT he developm ent of be am -diagnostic concepts and their engineering design has been retarded by the lack of adequate “w ith beam ” test facilities. This, in tu rn , has reflected on the ease of operation of the cyclotron. To date, tests of low-intensity devices have been con­ducted a t 4BT1; these are affected by experim ents at 4BT1 and by installa tion of the solenoid. H igh-current equipm ent is developed in beam line 1A between 1AM6 and 7, and here high rad iation levels and lack of access slow progress. In addition o ther groups, e.g. beam lines, vacuum , are affected by equipm ent installation and removal.A facility has been designed for installation in beam line 4A which will provide a controlled environm ent and basic facilities for general equipm ent development. Beam line 4A was chosen since, to date, access is fre­quently available for periods of several days, there is a long section of unoccupied space between the last dou­blet and 4AM8 (the old FE R FIC O N location), and the line and dum p have the ability to handle 10 pA.The vacuum vessel size can accom m odate the beam - sensing head of the largest existing m onitor and also the T 1 /T 2 production target vessels. A rap id pum p- ou t would perm it fairly frequent venting, a controlled gas leak and window valves would allow operation at pressures from atm ospheric to ~ 1 0 -6 Torr. There is provision to install coils to provide 50 G fields, per­m anent feedthroughs and cabling for therm ocouples, 32-way RG174, tw isted pairs, HV bias a t <1 kV and 6 kV and possibly optical fibres, also for water-cooling and heating coils. T he aim is also to provide perm a­nent amplifiers, m ultiplexing, etc. connected to the CYCVAX serial-CAM AC highway.L ine d en sityA T D C and TR IM A C have been installed in the meson hall to give convenient display in the C ontrol Room of the beam distribu tion w ithin an rf pulse. Thestan d ard inpu t is from the T l Cerenkov; however, the electronics are located adjacent to the fan-out of sec­ondary channel and other rates. T he inform ation pro­vided has been available for m any years bu t required the set-up of a TAC and PH A in the Control Room. The cyclotron VAX is being used un til the Control Room micro VAX is operational. T he TRIM A C rou­tines also replace those HLL routines in the Eclipse com puter displaying the secondary channel rates, and are expandable.C O M P U T I N G S E R V IC E S H ardw areC urrently TR IU M F has a t least 8 H P-Laserjet p rin t­ers. T heir proliferation is due to m any factors, but m ainly their low cost (<$2500), their high quality, and the availability of software which allows the full in­tegration of graphics w ith Tr X. T he success of the A tari 1040ST personal com puter a t T R IU M F (now es­tim ated a t 50 units) has also m ushroom ed due to its low cost (<$1000 for a com plete system ) and its versa­tile graphics term inal em ulating software (ST640) w rit­ten a t TR IU M F. Some of the secretarial staff prepare tex t for T^X docum ents off-line on their A tari and then transfer the tex t to the VAX cluster for processing and printing on the laser printers.To enhance colour graphics hardcopy support a 180 dpi 7 colour inkjet p rin ter, the H P-Pain tjet (<$1200), has been added to the array of graphics de­vices and is predicted to enjoy the sam e success as the H P-Laserjet.A rem ote PAXC shelf connected via one pair of the three-pair optical fibre cable has been installed allow­ing 16 bidirectional 9600 bd term inal connections be­tween T R IU M F and the UBC C om puting C entre. The reliability of the optical fibre cable has been good ex­cept for the costly breakdow n of some of the inferior splices th a t were m ade in the original installation. The proposed B C net linking the three B.C. Universities, T R IU M F and the Advanced System s In stitu te adja­cent to BCIT. has been funded and should be com­pleted by mid-1988. It will provide for 2.048 M baud (T -l) E thernet-to -E thernet links. M odem tests over a pair of the optical fibres connecting T R IU M F to UBC have already been successfully conducted. The “bridge” equipm ent will be installed next spring. This link will replace the M TSM O V E facility w ith high speed DECNET-like support.Softw areT he use of Tj^X a t T R IU M F has continued to ex­pand to the po in t where, after some in itia l tra in ing by140the C om puting Services group, it is now regularly used by some of the secretarial staff. For simple docum ents, letters, etc., the AES is still preferred, b u t for docu­m ents laden w ith form ulae and tables T^X is preferred.U pdated docum ents in TgX form at of the extensively enhanced versions of RELAX3D, PLOTDATA, OP- DATA, G P L O T , ED G R , ST640, and REPLAY were produced. These new style docum ents are published as T R I-C D -Y Y -# # (C om puting Design notes). The off-the-shelf availability of these high quality docu­m ents, although burdening the C om puting Services group w ith m any hours a t the copy machines, has had a positive im pact on the popularity of these utilities (some of which are invoked >1000 tim es/m on th on the local VAX cluster) bo th a t T R IU M F and dozens of re­search in stitu tes world-wide.Extensive upgrades were m ade to the VAX graphics editor ED G R , the general p lo tting program PLO T­DATA and the vector m anipulation program OP- DATA. An inpu t d a ta recall shell was also w ritten and interfaced to the above program s, allowing users to re­call previously typed inpu t in the sam e way as is cur­rently available in VAX DCL. T his feature will consid­erably reduce the num ber of keystrokes in using these highly in teractive program s.Support for several new graphics devices such as D E C ’s LN03+, SE IK O ’S GR-1105, T ektronix 4207/9, Im agen’s laser p rin ter, and H P ’s P a in tje t were w ritten.M isce llan eou sT he ST640 graphics term inal em ulating software for the A tari, w ritten a t TR IU M F, also provided for high speed (3-10 tim es faster th an using the conventional graphics routines) display of one- and two-dim ensional histogram s. Only the d a ta are sent to the A tari, the graphics processing and display being done locally. This has tu rned the A tari into a prim itive w orksta­tion supporting on-line d a ta acquisition system s and the off-line high speed replay of d a ta tapes.ACCSIM , a program to sim ulate the beam dynam ­ics of synchrotrons, was developed and docum ented. Moliere and nuclear scattering , longitudinal m atching of beams, and space charge effects were included. It accepts the DIM AD form at of the machine definition. A range of injected beam distribu tions is supported. S catterp lo t and loss checking a t user-specified ring lo­cations is allowed. Studies of an in ternal target for the KAON factory E ring, the longitudinal phase-space stacking for the A ring, and the injection and losses in the Los A lam os P S R were undertaken using ACCSIM .A repo rt com paring the analytic, num erical (using RELAX3D and T R IW H E E L ) and the lim ited experi­m ental study of an electron beam probe for ion beam diagnostics was also produced.Very good progress has been m ade th is year, both in technical studies and in the cam paign for funding. The m ost im portan t factor has been the B.C. provincial governm ent’s strong support for the pro ject as its top priority am ong federal projects and the centrepiece of its hi-tech developm ent strategy. In February the B.C. cabinet gave the project form al approval in principle;i.e. agreem ent to fund the civil works ($87M) provided the federal governm ent funds the technical equipm ent. T he province also agreed to support a $10M one-year study on a cost- shared basis.T he province’s efforts have been led by Prem ier Van- der Zalm and the m inisters responsible for science and technology, a t first the Hon. Grace M cCarthy, and la t­terly the Hon. S tan Hagen. In Septem ber the Prem ier launched a Public Awareness cam paign w ith a “gala evening” a t a downtown Vancouver hotel, helped by a 15-minute prom otional video, a new publicity book­let, our new scale model com plete w ith flashing lights, some cases of specially labelled “KAON P ro jec t” wine and the brass section of the Vancouver Symphony Or­chestra. A subsequent letter- w riting cam paign has proved very successful, w ith thousands of letters being sent to federal m inisters. These activities have been co­ord inated by a provincial desk officer and a full-time consultant and secretary.Good progress has also been m ade in gaining the support of o ther provinces. A m eeting of the National, Provincial and Territorial Science M inisters in Vancou­ver in M arch to sign the new national policy on sci­ence and technology was preceded by vigorous brief­ings of the provinces by T R IU M F users and potential industria l suppliers. Once in Vancouver the m inisters were trea ted to a tou r of T R IU M F in the afternoon, and a B.C. governm ent video featuring TR IU M F in the evening following the P rem ier’s dinner in honour of John Polanyi and A lan A stbury. T he Prem ier and Mr. Hagen have continued these contacts a t subsequent interprovincial m eetings.On the federal side the M inister of S ta te for Science and Technology, the Hon. Frank O berle, has agreed to a jo in t federal-provincial study of some rem aining questions:in ternational contributions for the fundingadditional university and provincial involvementeconomic benefitsThese studies are being supervised by a Steering C om m ittee composed of the presidents of NRC and NSERC, Larkin Kerwin and A rt May, and Mr. Ha­gen’s D eputy M inister, Isabel Kelly. A C anadian dele­gation, consisting of G .C . H anna, E .W . Vogt, and rep­resentatives of NSERC and the B.C. government, wasK A O N FACTO RY141also appointed to explore the po ten tia l for foreign par­tic ipation in the funding. D uring the fall the team visited appropria te governm ent officials in the Federal Republic of Germany, Italy, Jap an and the U.S.A. Each country agreed to consider financial involvement in construction, w ith a particu larly strong com m itm ent from Germ any. T he way appears to be clear for ne­gotiations over the am ounts, which are hoped to to ta l a t least $100 million. In addition countries such as Belgium, B rita in and the People’s Republic of C hina have expressed in terest in partic ipa ting in experim ents and providing experim ental equipm ent. Mr. Oberle himself, in a speech to the O ECD nations in Paris in O ctober, s ta ted “We are anxious to seek and develop other jo in t ventures” , giving as an exam ple "... in ter­national partnersh ip in the construction of the KAON Factory” .N otable visitors to T R IU M F this year in connection w ith the KAON Factory have been Prem ier Vander Zalm, Hon. S tan Hagen, the B.C. C abinet Com m it­tee on Economic Development, provincial m inisters re­sponsible for science, m em bers of the Prim e M inister’s N ational Advisory Board on Science and Technology, m em bers of the B.C. P rem ier’s new Science Council, a delegation of regional directors general representing various federal m inistries in Vancouver, mayors of vari­ous lower m ainland m unicipalities, the governors of the Vancouver B oard of Trade, the B.C Provincial Recov­ery C om m ittee, and the W 5 crew from CTV. A nother visitor was the leader of the O pposition, the R t. Hon. John T urner, who tab led a sta tem en t in the House of Com m ons supporting the project, and in a speech in Richm ond prom ised to build it if the Liberals won the next election.On the technical side a very successful KAON Fac­tory A ccelerator W orkshop was held from 4-6 A ugust. A large contingent from Los Alam os jo ined individuals from CERN , C halk River, Ferm ilab, R utherford and Science A pplications (San Diego) for a 3-day review of three areas of the design:rf system svacuum pipes and rf shieldsspace charge and paintingA m ajor r f topic was the problem of rf cavity par- asitics and the ir th rea t to beam stab ility when driven by “kicker voids” (em pty buckets). For fixed shunt im pedance per cavity it is desirable to minimize the num ber of cavities and m axim ize their voltage gain. T his would favour the use of perpendicularly biased microwave ferrite, as a t Los Alamos, although several tests rem ain to be done on their cavities.On vacuum pipes the im portan t conclusion was reached th a t ceramic pipes probably offer a b e tte r so­lu tion th an any m etal design for the 10 Hz m agnets inthe Driver, ju s t as for the 50 Hz Booster. No agreem ent was reached on the best type of rf shield - m etallized stripes or wire cage.One injection option is not to pain t in energy, thus leaving the bucket centre em pty, saving the cost of en­ergy ram ping and reducing the num ber of stripping foil traversals by stored protons. W hether such an annular d istribu tion would rem ain stable, however, rem ains to be seen.One fru it of the workshop was agreem ent to a ttem pt a closer collaboration between the LA M PF and T R I­UM F accelerator design groups. Poten tia l areas are or­b it dynam ics (both theoretical and experim ental w ith PSR commissioning), m agnet power supplies, vacuum pipe design and rf. T R IU M F could design and build (a t cost) low level and driver electronics, while LAM PF could make their cavity available for T R IU M F tests. T he collaboration got under way very prom ptly w ith an R F W orkshop a t Los Alam os on 3 Septem ber and some days of m easurem ents on the Los Alamos cavity, for which it was shown th a t a high Q could be m ain­tained down to the lowest frequency required by T R I­UM F. In itial beam commissioning runs on the PSR have involved studies of H° stripp ing in the injection foil and of dispersion around the ring.A six-m onth study of the KAON Factory control sys­tem has been com pleted w ith the help of two visitors from CERN. A com prehensive review was carried out of both hardw are and software options and a weighty report is now available.UMA Spantec L td. was awarded a contract for a project m anagem ent study to repo rt on organization, m anagem ent procedures and breakdow n of the project into engineering packages. Prequalification subm is­sions were also solicited from interested companies in order to assess w hich w ould be p o te n tia lly capable of contributing to the design and construction of the KAON Factory.O rbit d yn am ics TrackingA tracking study was carried out for the Booster ring to determ ine its dynam ic apertu re in the presence of higher-order error fields. E stim ates for the error fields were ob tained from design studies for the dipole mag­nets, done a t T R IU M F, and from existing TR IU M F 8 in. quadrupoles. T he m agnitude of the error fields determ ined in th is way was about 3 -5 x lO -4 relative to the bending field in the dipoles and 1 -2 x lO -3 rela­tive to the pole-tip field in the quadrupoles. The error fields were sim ulated as th in m ultipoles in the com­pu ter code DIM AD. A test particle was traced around the ring for 200 tu rns and the phase-space distortion142a t an inspection po in t was recorded.For the high-intensity working point, vx , vy — 5.23,7.22, the acceptance of the ring was found to be about 1.5 tim es the beam em ittance a t injection, ex ,ey — 1407r m m -m rad, 627r m m -m rad, while for the working poin t anticipated for acceleration of polar­ized protons, vx , Uy = 5.23, 4.22, it was ju s t equal to th a t em ittance. T his reduction can be explained by the larger peak value of the vertical (3 function for the reduced vertical tune. The reduced acceptance exceeds by far the expected em ittance for polarized beam , about 257T m m -m rad. Figure 127 shows the dis­tribu tion in vertical phase space for the high-intensity tune. Synchrotron oscillations were included in the tracking runs; no detrim ental effect due for instance to synchrobetatron coupling was observed.short m agnets bending horizontally restore the orbit to create the stra igh t device th a t is necessary for energy- independent operation . As for a continuous helix, the beam excursion is p roportional to 1 /n while the length increases only proportional to y/n, where n is the num ­ber of tw ists. T hus the o rb it excursion can be reduced by adding m ore tw ists w ithout paying too much for additional length of the snake. In general, snakes with 2 or 3 tw ists are bo th shorter and have less orbit ex­cursions th an the Steffen snake, m aking them espe­cially a ttrac tive for applications a t lower injection en­ergy. For the Driver, a three-tw ist snake is 10.6 m long and has about 9 cm orb it excursion a t 3 GeV, to be com pared w ith 11.5 m length and about 15 cm or­b it excursion for the Steffen snake. Figure 128 shows the m agnet array and the o rb it excursions for a one- tw ist snake. We have designed a sim ilar device for the European H adron Facility, where the higher injection energy of 9 GeV keeps the orbit excursion a t 3.5 cm for a three-tw ist snake.222 2 22 1 2 11 1 1 11 2 11 22 11 2 2 1 1 22 2 1 211 12 1 22 1 11 2 1 2 2 11 222 11 22 1 2 2 2 1 2 1 1 2 1 2 221 2 2 111 2 111 1 2 2 1111 2 222 22 2 2 2 2 2 2 2 2 2 22 2 2 22 2 2 2 222 2 1 111111 1 2 2 1211 111111111 111 1111 122221 222 1 1 2 1 “22 2 1122 2 12 1 22 2 1 1 2 11 1 22 2 112 222 1122 11 111 11 222 " 2111 1 211122 11 22 211 222 2 1 22 11 11222 2 11 2222 222 2 2 111 11 1 11111 11122 2 2 2 1 11111112 2 22 22 22 2 222 22 2 2 2 2 2222 222 2SIDE VIEWTOP VIEWmmmmmrnH 225° 135° 45 ° - 4 5 ° -HFig. 128. O rbit and m agnet array for a one-twist discrete helical snake. The angles indicate the angles of tilt about the beam axis. The spin is ro tated by 114.5° in each of the 4 snake magnets. The first and last m agnets are horizontally bending orbit restoring magnets.Fig. 127. Vertical phase-space distribution for the Booster at vx , v y = 5.23, 7.22. Particle 1 was at the nominal em it­tance, particle 2 a t ex , Zy — 209x mm-mrad, 937T mm-mrad.PolarizationIn an effort to improve the preservation of polariza­tion in the Driver ring further, a novel Siberian snake has been designed. T he new snake exhibits smaller orbit excursions th an the m ost common design up to now, th a t due to K. Steffen from DESY. The design is based on the helical snake first m entioned by Der­benev and K ondratenko and la ter reinvented by E.D. C ourant. T he continuous helical m agnet of th is snake has been replaced by a series of ordinary bending m ag­nets th a t are tilted by 45° about the beam axis. TwoThese are snakes of the first kind, ro ta ting the spin by 180° about the longitudinal axis. A lthough the axis of ro ta tion can be varied som ew hat by changing the an­gle of t i l t of the m agnets, it is not possible w ith this device to construct a m ulti-tw ist snake of the second kind w ith a rad ial axis of spin ro ta tion , or a snake with an axis of ro ta tion of 45°. Therefore, since published snakes w ith axes of ro ta tion differing from the longi­tud inal axis have excessive o rb it excursions, a pair of orthogonal snakes w ith low o rb it excursions is not yet available and one single snake has to be used. This implies th a t the direction of polarization will always be in the horizontal plane.T he spin ro ta to r w ith tilted m agnets has significance beyond the construction of Siberian snakes. In a study for the electron-positron storage ring P E P a t SLAC, we have designed such a spin ro ta to r to achieve longitudi­nal polarization a t one of the in teraction points. Be­ing basically one-half of a tw o-tw ist snake, the helical143i11 1 i 1 i 'DISTANCE (m )Fig. 129. Lattice functions of a racetrack lattice for the Driver. The maxim um value of the b e ta function in the straight section was arbitrarily chosen to be 100.ro ta to r is considerably shorter th an the HERA “m ini” ro ta to r while a t the sam e tim e it exhibits sm aller or­b it excursions. Furtherm ore, the ro ta to r creates less radiative depolarization in the ro ta to r m agnets them ­selves as m easured by its figure of m erit, £2d, where I is the length and d the “depolarizing weight” .LatticesTo make it easier to incorporate an ultra-low-loss slow -extraction system into the Extender lattice, more flexible a lternative lattices have been investigated for the large rings. A racetrack la ttice appears to be the op tim al choice since it offers long stra igh t sections for sep ta and beam scrapers w ithout interference from dipole m agnets. However, it was desired to m aintain the im aginary transition energy of the present design as well as the to ta l length, which is constrained to be22.5 tim es the extraction radius of the T R IU M F cy­clotron. In addition, the stra ig h t sections should be as flexible as possible to perm it tun ing of the la ttice func­tions for optim um ex traction . The new la ttice would be used for the C-, D-, and E-rings since they share a common tunnel.The la ttice proposed has 24 FO D O cells per arc, com pletely filled w ith bending m agnets and tuned to a phase advance of 5.27T. There are six superperiods per arc, each consisting of four cells w ith the central and the outside focusing quadrupoles tuned to create the m odulation in the dispersion function th a t pushes the transition energy to infinity. Some m odulation of the b e ta function has to be accepted because the bend­ing radius has no sim ilar periodic structu re . However,the m axim um values of the b e ta function and the eta function are lower th an in the old lattices, allowing the apertures to be reduced. Figure 129 illustrates the la ttice functions for one-quarter of the machine.W ith the arcs being un it sections, the stra igh t sec­tions are dispersion free. They are employed to tune the m achine and are flexible enough to allow the work­ing point to be varied over 2 un its in b o th the hori­zontal and the vertical planes while keeping the be ta functions a t reasonable values. Also, they provide the space necessary for rf cavities, extraction elem ents and Siberian snakes. D ispersion in the stra ig h t sections can be fine tuned by slightly varying the phase advance in the arcs.P ro to n in je c t io n /e x tr a c t io nProject injectionFor the controls study m entioned elsewhere in this report, the tim ing precision necessary for accelerator injection and extraction has been estim ated. Any tim ­ing error transla tes in to a deviation of the central mo­m entum of the injecting ring from the m om entum of the beam due to the varying m agnetic field in the ac­celerators. Due to the sinusoidal m agnet cycle the m om entum error is approxim ately p roportional to the square root of the tim ing error. In order to keep the m om entum error less th an 1% of the m om entum bite of the beem , the precision of the injection and extraction windows of the Booster has to be b e tte r th an 15 ps, while for the slower cycling Driver 100 ps are allowed for the same fractional m om entum error.Slow extractionUsing our slow -extraction code SLEX, it could be shown th a t, in achrom atic ex trac tion mode, the tran s­verse em ittance of the beam can be less th a n 0.5tt mm- m rad. This value is solely determ ined by the chro- m aticity of the la ttice functions a t the position of the extraction septum and the residual m achine chrom atic- ity. The du ty factor is about 80% for uniform beam distribu tion and a nonlinear tune shift program .C urren tly the slow -extraction system is undergoing a com plete review in view of its being a m ajor source of loss and of rad iation dose in existing machines. Ex­trac tion losses are also difficult to localize, since the sep ta are several m etres long and represent large-area sources. We have therefore a ttem p ted to redesign the extraction system , aim ing a t losses of the order of 10- 3 , one order of m agnitude down from the present design. A t th is level the use of a pre-septum is necessary in order to avoid too strong dem ands on the m ain elec­tro sta tic septum . T he pre-sep tum would provide only144to calculate transverse and longitudinal rms em it­tance for the accum ulated beam-120 -7 2 -2 4 24 72 120X ( m m )Fig. 130. Horizontal phase space a t position of the pre­septum . The ft function is 100 m, a is —2. The 0.5 m long septum is located 50 mm from the centre of the beam.• utilize the (3 x 3) transfer m atrices from DIMAD to describe the transverse m otion of particles from cavity to cavity and between injection point and cavities• produce sca tter plots o f the accum ulated beam at any elem ent in the ring as specified in the DIMAD lattice definition• perform loss checking against specified apertures a t various locations in the ring• to generate gaussian d istribu tions for the injected beam ; through a generalized m ethod a range of d istribu tion types, from uniform to elliptical to gaussian, is now supporteda very sm all kick to the beam , b u t would significantly cut the losses on the m ain septum . O ptions for the pre-septum include an u ltra th in and quite short elec­tro sta tic wire septum and a novel“massless” septum m ade from perm anen t m agnets according to a design of K. Halbach. An investigation of a 0.5 m long wire septum w ith 10 fim thick wires indicates th a t such a device could have an effective thickness of less than 12 fim, m ainly due to differential heating. The wires would heat up to about 500° if carbon fibres are used. Even if the full beam were steered in to the septum the tem pera tu re of the wires would rem ain below the m elting point. T he septum would operate a t a modest field of about 5 kV /m m , requiring 100 kV for a gap of 20 mm.In order to model an extraction system using this device the SLEX code has been extended to be able to sim ulate extraction system s w ith m ultiple septa. Ex­trac tion losses (particles h itting the pre-septum ) were found to be about 0.19% over the full length of the septum . Figure 130 shows the horizontal phase space a t the position of the pre-septum . SLEX is now used to define the optical properties of the extraction sec­tion and the influence of chrom atic aberrations on the extraction efficiency.T he additional p re-septum cannot be incorporated in the reference la ttice for the Extender ring. A race­track la ttice has been developed w ith extrem ely flex­ible stra igh t sections to accom m odate the extraction system and is described elsewhere in th is report.H ~ accu m u la tio nT he accum ulation sim ulation program ACCSIM has been modified to:P S R collaborationOne aspect of the TR IU M F-L A M PF collaboration in KAON factory studies is T R IU M F involvement in the commissioning of the Los Alamos P ro ton Storage Ring. T his ring accum ulates 800 MeV protons from the LA M PF linac over a period of ~0 .1 to 1 ms and ex tracts the stored beam over one tu rn , 0.36 /is, direct­ing the ex trac ted beam to the ta rg e t of a pulsed neu­tron facility. A t present, commissioning efforts are di­rected tow ards understanding the details of beam loss mechanisms which occur during accum ulation and to identify possible instabilities which may arise when the operating intensity is raised from the present 1 .2 x l0 13 p ro tons/pulse (30 n A a t 15 Hz) to the design aim of ~ 4 x l 0 13 ppp. T he la tte r corresponds to a circulating beam of 20 A.Several T R IU M F scientists and engineers partici­pated in the developm ent work over two visits of 1.5 weeks during the fall. Besides becom ing acquainted w ith the instrum enta tion and perform ance of the PSR, our in itia l involvem ent has led to:• the operation of the T R IU M F program s D IPLO T and ACCSIM on the M PX VAX cluster a t LANL and some calculations w ith P S R param eters• a calculation showing th a t the im aginary p art of the im pedance (due to space charge) will far ex­ceed the real p a rt (due to equipm ent) a t the de­sign intensity, prom oting recom m endations th a t the injection procedure try to reduce local peaks in charge density and th a t the rf voltage be in­creased• an approxim ate m easurem ent of the dispersion around the ring145• m easurem ents utilizing a diode detector and a m ixer detector w ith a bandpass-filtered inpu t to determ ine the su itab ility of processing stripline and capacitive pick-up signals a t low frequency (2.8, 8.4 and 11.2 MHz) in order to provide infor­m ation on the position of the accum ulated beam.Longitudinal dynamicsW ork has centred upon im proving the com puter code LONG ID , which models synchrotron longitudinal dynam ics in the presence of space charge. L0N G 1D is used to sim ulate beam s in the T R IU M F KAON factory. M ilestones were m odelling of injection into the A-ring, m ore realistic modelling of the internal space-charge force, and m odelling of dam ping loops to suppress beam oscillations. Sim ulation of acceleration (from 0.44 GeV to 30 GeV) in the Booster and Driver rings w ith a full in tensity beam (1013ppp) shows no beam loss. T he required peak accelerating voltages in each ring are 660 kV and 2550 kV, respectively. The study of beam accum ulation in the A-ring (from T R I­UM F) is incom plete. T he off-energy injection scheme, designed to reduce stripping foil traversals, produces an annular ensemble in phase space. In the presence of longitudinal space charge LONG ID shows th is en­semble to be unstable: transform ing into an oscillating charge d istribu tion , as shown in Fig. 131. No beam is lost, bu t an halo is generated. Energy ram ping schemes have been found to stabilize the d istribu tion by filling in the annulus, bu t a t the cost of double the beam scattering a t the injection foil.Magnet power suppliesStudies have continued on bo th theoretical and ex­perim ental fronts. A prelim inary design for the bias supplies for the Booster and Driver m agnet rings was generated. B oth power supplies will be based on a 12-pulse thyristor-contro lled design w ith the Booster power supply requiring a transisto r pass bank for ripple attenuation . C om puter sim ulations have shown th a t effective isolation of the pulsed load from the ac grid is feasible w ith the grid seeing m ore or less a constant load. Design proceeded to define the pulse-forming network needed to make up for losses in the resonant circuit. O rders were placed for the required HV sup­ply and other m ateria ls required for the tests. This will enable us to close the control loop and will be a m ore accurate sim ulation of the actual power supply system required. Inform ation was also generated for the controls task force relating to the required control points, num bers of devices and their characteristics.Four NINA m agnets have now been placed in their test configuration in the p ro ton hall extension and arein the process of being provided w ith cooling water. T he test circuit is being wired. A solid-state switch for capacitor switching has been purchased. C ircuit boards for the capacitor sw itch have been laid ou t and are in the process of being assembled. Low-power tests to determ ine the resonant frequencies of the test facil­ity are about to commence. These are to be followed by high- power tests running open loop to characterize system param eters.Beam instabilitiesThe KAON Factory proposal specifies a gap of 5 consecutive em pty buckets in the synchrotrons to allow for injection and extraction kicker m agnet rise tim e. A circulating beam w ithou t gaps has Fourier com ponents only a t harm onics of the rf frequency. W ith a kicker gap, there are Fourier com ponents a t all harm onics of the revolution frequency. These Fourier com ponents will strongly excite the rf cavity parasitic resonances which in tu rn will strongly excite coupled-bunch insta­bility modes. T he sm aller the kicker gap, the less se­vere is the problem . Kickers w ith faster rise are there­fore very desirable. Assum ing th a t kickers w ith rise tim es <30 ns will not be developed, it will be neces­sary to reduce the im pedances of the parasitic cavity modes to the level of a few kfi.RF cavity developmentT he new rf cavity reference design, which was estab­lished last year as a result of the rf model work, is a double-gap d rift-tube cavity w ith parallel-biased ferrite tuners to vary the frequency from 46 MHz to 62 MHz. T his cavity, w ith air dielectric tuners, is presently be­ing fabricated in the m achine shop w ith the help of ou t­side contractors. In the m eantim e Los A lam os has ob­tained prom ising results from a single-gap cavity w ith perpendicularly biased ferrites to vary the frequency from 50 MHz to 60 MHz. In order to keep our options open the m agnetizing circuit of the T R IU M F cavity and the Los Alamos cavity were bo th analysed and a power supply specification was prepared for each sys­tem .A t the KAON Factory A ccelerator W orkshop held in Vancouver in A ugust the rf working group discussed, am ong other subjects, a com parison of parallel-biased NiZn ferrites w ith perpendicular-biased microwave fer­rites. Perpendicularly biased ferrites appeared to be favoured on alm ost all counts except for ac biasing which seems to be more difficult in the perpendicularly biased case and could m ean a m ore expensive power supply since the m agnetizing circuit is less efficient. In view of our in terest in perpendicularly biased ferrites it was suggested th a t a T R IU M F /L os Alam os collabora-146Oongif ubinal Qfjasp Sparp Bongitubinal B^asp Sparp Eongitubinal Bfyasp SparpO O 04I Iaona is 11in /ft 131 n2 5w o o8 Ai i i i | i i i i | t i t i - f T T T T j - r i v r f cm -£O 12C + 12C [completed], R. Abegg, L.G. Greeniaus, D.A. Hutcheon, C.A. Miller (TRIU M F),J.M. Cameron, W .K. Dawson, C.A. Moss, G. Roy, H. Sherif, J. Uegaki, H. Wilson (Univ. o f Alberta), C.A.Davis (Univ. o f Manitoba)196. M easurem ent of pionic X-rays in 23Na, 24Mg and 27A1 [completed], A. Olin (TR IU M F -U niv. o f Victoria), J.A. M acdonald, T . Numao (TRIU M F), G.A. Beer, G.R. Mason (Univ. o f Victoria), B. Olaniyi (Univ. o f Ife), P.R. Poffenberger (Univ. o f Manitoba)197. A precise m easurem ent of the Lamb shift in muonium in the 2S sta te [letter of intent], J.H. Brewer, A. Fry,J.B. W arren (Univ. o f British Columbia), R. Kiefl, C. Oram (TRIU M F)181198. n-p to ta l cross section in pure spin states [letter of intent], D.A. Axen, F. Entezam i, C. W altham (Univ. o f British Columbia), J.A . Edgington (Univ. o f London, QMC), M. Comyn, G. Ludgate (TR IU M F ), L.P. Robertson (Univ. o f Victoria)199. A study of low energy pion absorption in 3He [completed], J. Alster, A. A ltm an, D. Ashery, L. L ichtenstadt, M.A. Moinester (Tel-Aviv Univ.), R.R. Johnson (TR IU M F -U B C ), B. B arnett, W. Gyles, H. Roser, R. Tacik (Univ. o f British Columbia), D.A. Gill, J.S. Vincent (TRIU M F), K. Aniol (California State Univ. LA), S. Levenson (Northwestern Univ.)202. Nuclear radii m easurem ents in the A ~ 20 region [completed], T .E . Drake, R. Sobie (Univ. o f Toronto),A. A ltm an, M.A. Moinester (Tel-Aviv Univ.), B. B arnett, J. Coopersm ith, K.L. Erdm an, W. Gyles, R. Tacik (Univ. o f British Columbia), R.R. Johnson (TR IU M F -U B C ), G.A. Beer (Univ. o f Victoria), E.W . Blackmore,D. Gill (TR IU M F ), A. Olin (TR IU M F -U niv. of Victoria), S. M artin (KFA Jiilich), C. W iedner (Max Planck Institu t)203. Inelastic pion scattering on neon isotopes [completed], T .E . Drake, R. Sobie (Univ. o f Toronto), A . A ltman, M.A. Moinester (Tel-Aviv Univ.), B. B arnett, J. Coopersmith, K.L. Erdm an, W. Gyles, R. Tacik (Univ. of British Columbia), R.R. Johnson (T R IU M F - UBC). E.W . Blackmore, D. Gill (TRIU M F), S. M artin (KFA Jiilich), C. W iedner (M ax-Planck-Institut), B.H. W ildenthal (Michigan State Univ.)204. Strong in teraction shift and w idth in pionic 22Ne atom s [completed], G.A. Beer, G.R. Mason (Univ. o f Victoria),A. Olin (TR IU M F -U niv . o f Victoria), T .E . Drake, R. Sobie, (Univ. of Toronto), B. Olaniyi (Univ. o f Ife)205. Tensor analysing power in pion deuterium scattering [active], L. Dallin, K. Itoh, Y.M. Shin (Univ. o f Saskatch­ewan), B. B arnett, K.L. Erdm an, W. Gyles, R. Tacik (Univ. o f British Columbia), R.R. Johnson (T R IU M F - UBC), E.W . Blackmore, D.R. Gill, G.D. W ait (TRIU M F), G. Lolos (Univ. o f Regina), K. Aniol (California State Univ. LA), T .E . Drake (Univ. o f Toronto), S. M artin (K fA Jiilich)206. A study of (p ,n ) and related reactions [completed], D.H. Boal, J.M. D’A uria, R.G. Korteling (Sim on Fraser Univ.), K.P. Jackson (TRIU M F), R. Helmer (Univ. o f W estern Ontario), R.E.L. Green (Los Alamos National Lab)207. 48Ca(p', p ') 48C a ( l+ ) [completed], R. Abegg, D.R. Gill C.A. Miller (TRIU M F), J.M. Cameron (Univ. o f Alberta), P. Kitching (TR IU M F -U niv. o f Alberta), C.A. Davis (Univ. o f Manitoba), J. Coopersm ith, (Univ. o f British Columbia), R.R. Johnson (TR IU M F -U B C ), G. Berg, S. M artin (K fA Jiilich), J. L isantti (Univ. o f Oregon), M.A. M oinester (Tel-Aviv Univ.), R. Santo (M iinster Univ.)208. Proton-proton brem sstrahlung [completed], P. Kitching (TR IU M F -U niv. o f Alberta), P.W. Green, M. Hugi, M. Michaelian, G.C. Neilson, W .C. Olsen, D.M. Sheppard,* J. Soukup, J. Uegaki, J. Wesick (Univ. o f Alberta), R. Abegg, H.W . Fearing, L.G. Greeniaus, D.A. Hutcheon, C.A. Miller (TRIU M F), N. Stevenson (Univ. of Saskatchewan)2 1 1 . The neutron and gam m a-ray correlation in the x “ and captures in medium-heavy nuclei [completed], T .J . Hallman, Y.K. Lee, R. Levin, L. Madansky, E. M cIntyre (Johns Hopkins Univ.), G.R. Mason (Univ. of Victoria), K.S. Kang (Neung Univ.), B. Olaniyi (Univ. o f Ife)212. In search of a tredecabaryon resonance [completed], R. Abegg, K.P. Jackson, C.A. Miller (TR IU M F ), D.H. Boal, J.M. D’Auria, R.G. Korteling (Sim on Fraser Univ.), R.E.L. Green (Los Alamos National Lab), R. Helmer (Univ. o f W estern Ontario)213. Absorption at rest of ir~ in 4He and 6Li [completed], G. Cernigoi, N. Grion, G. Pauli, R. Rui (IN F N and Univ. di Trieste), R. Cherubini (National Lab o f Legnaro-Univ. di Padova), D.R. Gill (TR IU M F ), W. Gyles (Univ. of British Columbia)215. Inclusive (p ,p) spectra [completed d a ta taking], R.E. Segel, A. Hassan, S.M. Levenson (Northwestern Univ.), P. Gumplinger, A.W . Stetz, L.W. Swenson (Oregon State Univ.), K.P. Jackson (TRIU M F), P.P. Singh (Indiana Univ.), J. Tinsley (Univ. o f Oregon)216. Investigation of spin-flip resonances and energy dependencies of com ponents of the Love-Franey interaction [completed], F.E. Bertrand, E.E. Gross, D .J. Horen, T .P. Sjoreen (Oak Ridge National Lab), J. L isantti, D.K. McDaniels, J. Tinsley (Univ. o f Oregon), L.W. Swenson (Oregon State Univ.)217. Low-energy, electrom agnetic pion form factors [completed d a ta taking], J.-M. Poutissou (TR IU M F ), P. Gum p­linger, D. Ila, A.W . Stetz (Oregon State Univ.), M.D. Hasinoff (Univ. o f British Columbia), T . Mulera, V. Perez-Mendez, A. Sagle (Lawrence Berkeley Lab)218. Pion production from 12C and 10B with polarized protons of 350 MeV [completed], G. Lolos (Univ. o f Regina), R.R. Johnson (TR IU M F -U B C ), G. Giles, G. Jones, B. M cParland (Univ. o f British Columbia), D. Ottewell, P. W alden (TR IU M F ), R.D. Bent (IUCF), W. Falk (Univ. o f Manitoba)182219. The chem istry of pionic hydrogen atoms [completed d a ta taking], D. Horvath (Central Research Inst, fo r Physics, Budapest), D.F. Measday, S. Stanislaus (Univ. o f British Columbia), M. Salomon (TRIU M F), K. Aniol ( California State Univ. L A )220 . T em perature dependence of the spin exchange cross sections between muonium and alkali m etal [completed],D.J. Arseneau, D.G. Fleming, M. Senba (Univ. o f British Columbia), D.M. Garner (TR IU M F )221. Search for evidence of a delta-nucleus interm ediate sta te in proton elastic scattering [completed d a ta taking],C.A. Davis, W .P. Lee, W .T.H . van Oers (Univ. o f Manitoba), H.O. Meyer (IUCF), P. Schwandt (Indiana Univ.), K.P. Jackson (TRIU M F), H.W. Roser (Univ. of British Columbia)223. The 2H(p, 2p) reaction and m om entum distributions of the deuteron [completed d a ta taking], H.P. Gubler, W.P. Lee, W .T.H . van Oers (Univ. o f Manitoba), C.F. Perdrisat (College o f William and Mary), J.M. Cameron (IUCF), M.B. Epstein, D .J. M argaziotis (California State Univ.), H. Postm a (Technical Univ. Delft), A.W. Stetz (Oregon State Univ.), R. Abegg (TRIU M F)224. Inclusive pion scattering from light nuclei [completed d a ta taking], K.G.R. Doss, I. H alpern, M. Khandaker,D.W. Storm (Univ. o f Washington), J.F . Amann (Los Alamos National Lab)225. Search for isovector properties of IBA nuclei [deferred], J. Alster, J. L ichtenstadt, M. Moinester (Tel-Aviv Univ.), G. Azuelos, D.R. Gill (TRIU M F), R.R. Johnson (TR IU M F -U B C ), B.M. B arnett, W. Gyles, H. Roser, R. Tacik (Univ. o f British Columbia), S. M artin (KFA Jiilich), R. Sobie (Univ. o f Toronto), K. Aniol (California State Univ. L A )226. Study of neutron-proton transition am plitudes in 14C using 50 MeV pions [completed d a ta taking], R.R. Johnson (TR IU M F -U B C ), H. Roser, R. Tacik (Univ. o f British Columbia), K. Aniol (California State Univ. LA), J. Alster, J. Lichtenstadt, M.A. Moinester (Tel-Aviv Univ.), G. Azuelos, D.R. Gill (TRIU M F), S. M artin (KFA Jiilich), R. Sobie (Univ. of Toronto), H.W. Baer (LAM PF)227. E lastic and inelastic scattering of polarized protons from 10B [completed d a ta taking], P.R. Andrews, S.M. Banks, P. Lewis, V.C. Officer, G.G. Shute, B.M. Spicer (Univ. o f Melbourne), C.W . Glover (IUCF)229. Pion double charge exchange a t low energy in the T P C [completed d a ta taking], D.A. Bryman, M .J. Leitch,I. Navon, A. Olin, P. Schlatter (TR IU M F -U niv. o f Victoria), A. Burnham , M. Hasinoff (Univ. o f British Columbia), G. Azuelos, J.A. Macdonald, T . Numao, J.-M. Poutissou, J. Spuller (TRIU M F), P. Depommier, R. Poutissou (Univ. de Montreal), M. Blecher, K. Gotow (V P I and State Univ.), M. Dixit, C.K. Hargrove, H. Mes (National Research Council), M.A. Moinester (Tel-Aviv Univ.), H. Baer, M. Cooper (LAM PF)230. Muonic molecule form ation rates in HD gas [completed d a ta taking], K. Aniol (California State Univ. LA), F. Entezam i, D.F. Measday, C. V irtue (Univ. of British Columbia), D. H orvath (Central Research Inst, fo r Physics, Budapest), M. Salomon (TRIU M F), J. Smith (Univ. o f Surrey), S.E. Jones (Idaho National Engineering Lab),B.C. Robertson (Queen’s Univ.)231. Studies of light pionic atoms [completed], G.A. Beer, G.R. Mason, G.M. Marshall (Univ. o f Victoria), A . Olin (TR IU M F -U niv. o f Victoria), J.A. Macdonald (TRIU M F), E. K lem pt (Johannes Gutenberg Univ., Mainz), C. Wiegand (Lawrence Berkeley Lab), K. Wetzel (Univ. o f Portland), W .C. Sperry (Central Washington Univ.),B.H. Olaniyi (Univ. o f Ife)232. Muon K night shifts in metals [completed d a ta taking], J.H. Brewer, E. Koster, D. Llewelyn-Williams (Univ. of British Columbia)233. Vector analysing power and spin transfer param eters for the d —*■ pp reaction [active], E.G. Auld, P. Couvert,G. Jones, B. M cParland (Univ. o f British Columbia), R.R. Johnson (TR IU M F -U B C ), D. Ottewell, P. Walden (TR IU M F ), G. Lolos (Univ. o f Regina), W. Falk (Univ. o f Manitoba)234. Study of simple features of the A(p, w ~)A + 1 reaction in the (3,3) resonance region [completed d a ta taking], R.D. Bent (IUCF), G .J. Lolos (Univ. o f Regina), G.E. Walker (Indiana Univ.), P. Couvert, G. Giles, G. Jones,B. M cParland, W. Ziegler (Univ. o f British Columbia), J. Iqbal, P. Walden (TRIU M F), W .R. Falk (Univ. of Manitoba)236. (p ,p ') reactions in nuclei [completed], R.E. Azuma, T .E . Drake, J.D. King, S.S.M. Wong, X. Zhu (Univ. of Toronto), K.P. Jackson, S. Yen (TRIU M F), A. Zaringhalan (Bell Laboratories)237. Proton-nucleus in teraction [completed], R.E. Azuma, T .E . Drake, J.D. King, S.S.M. Wong, X. Zhu (Univ. of Toronto), S. Yen (TR IU M F )238. Inelastic proton excitation of low-lying nuclear sta tes for Ep — 200-500 MeV [completed], R.L. Auble, R.E. Bertrand, E.E. Gross, D.J. Horen, G.R. Satchler, T .P. Sjoreen (Oak Ridge National Lab), D.K. McDaniels, J. Tinsley, J. L isantti (Univ. o f Oregon), L.W. Swenson (Oregon State Univ.)183239. Muon spin relaxation studies of spin glasses and random spin systems [completed d a ta taking], Y .J. Uemura (Brookhaven National Lab), J.H . Brewer (Univ. o f British Columbia), K.M. Crowe (Lawrence Berkeley Lab),T. Yamazaki (Univ. o f Tokyo), Y. Miyako, K. K atsum ata (Univ. o f Hokkaido), Chikazawa (Muroran Inst, of Technology)241. T em perature dependence of reaction rate constants for muonium addition reactions in liquid phases [completed],K.L. Cheng, R.L. G anti, Y .C. Jean (Univ. o f M isssouri-Kansas City), D.C. Walker (Univ. o f British Columbia),J.M . S tadlbauer (Hood College), B.W. Ng (W inona State Univ.)242. Radiochemical study of the (p, t + ) reaction on bism uth [completed d a ta taking], J. D ’A uria, M. Dombsky (Sim on Fraser Univ.), T . R uth (TRIU M F), T . W ard (IUCF), A. Yavin (Tel-Aviv Univ.)243. Energy and angle dependence of the 6Li(7r+ ,3He)3He reaction [completed], G. Huber, G .J. Lolos, S.I.H. Naqvi,Z. Papandreou (Univ. o f Regina), E.G. Auld, P. Couvert, G. Jones, B.J. M cParland (Univ. o f British Columbia),R.R. Johnson (TR IU M F -U B C ), D. Ottewell, P.L. Walden (TRIU M F)244. p + spin relaxation in Y9C07 and ternary magnetic superconductors [completed], E .J. Ansaldo (Univ. of Saskatchewan), C.Y. Huang (Los Alamos National Lab), J.H. Brewer, M. Senba (Univ. o f British Columbia),K. Crowe (Univ. o f California, Berkeley), S.S. Rosenblum (Lawrence Berkeley Lab), D.R. Harshm an (AT& T Laboratories)245. Muon spin rotation studies of unsupported and supported platinum catalysts [completed], W.S. Glausinger,R.F. Marzke (Arizona State Univ.), E. Ansaldo (Univ. o f Saskatchewan), J.H. Brewer, S. K reitzm an, D. Noakes,M. Senba (Univ. o f British Columbia), R. Keitel (TRIU M F), D.R. Harshman (A T & T Laboratories)246. The double charge exchange reaction a t T = 50 MeV on l s O using the QQD spectrom eter [completed], E.W. Blackmore, D.R. Gill (TRIU M F), R.R. Johnson (TR IU M F -U B C ), K.L. Erdm an, H. Roser, R. Tacik (Univ. o f British Columbia), A. A ltm an, M.A. Moinester (Tel-Aviv Univ.), S. M artin (KFA, Jiilich), C.A. Wiedner (M PI, Heidelberg), T. Drake, R. Sobie (Univ. o f Toronto), T .G . M asterson (Univ. o f Colorado)247. Precise m easurem ent of muon decay asym m etry param eter S [completed d a ta taking], J. C arr, G. Gidal (Lawrence Berkeley Lab), A. Jodidio, K.A. Shinsky, H.M. Steiner, D. Stoker, M. Strovink, R.D. Tripp (Univ. o f California, Berkeley-LBL), B. Gobbi (Northwestern Univ.), C .J. Oram (TR IU M F )248. A study of the K+-e+i>e decay [completed d a ta taking], J.A. Macdonald, T . N um ao, J.-M . Poutisisou (T R I­UMF), D.A. Bryman, A. Olin (TR IU M F -U niv. o f Victoria), M.S. Dixit (National Research Council) 5249. Radiative muon capture on hydrogen with the T P C [succeeded by 452], G. Azuelos, J.A. M acdonald, T . Numao,J.-M. Poutissou, J. Spuller (TRIU M F), G. Bavaria, P. Depommier, H. Jeremie, L. Lessard, J.P. M artin, R. Poutissou (Univ. de Montreal), D.A. Bryman (TR IU M F -U niv. o f Victoria), M. Leitch, I. Navon, P. Schlatter (Univ. o f Victoria), A. Burnham , M.D. Hasinoff (Univ. o f British Columbia), M. Blecher, K. Gotow (V P I &State Univ.), M. Dixit, C.K. Hargrove, H. Mes (National Research Council), J. Bailey (Yale Univ.) 6250. Charge-exchange coincident w ith X /gam m a-rays in pionic phosphorus [completed d a ta taking], J.M . Bailey (Yale Univ.), G.A. Beer, G.R. Mason (Univ. of Victoria), D.F. Measday (Univ. o f British Columbia), A. Olin (TR IU M F -U niv. o f Victoria), M. Salomon (TRIU M F), P.R. Poffenberger (Univ. o f Manitoba)251. Coincident optical and X-ray transitions in muonic helium [deferred], J.M. Bailey (Yale Univ.), C .J. Oram (TRIU M F), G.M. M arshall (Univ. o f Victoria), J.D. Silver, D.N. Stacey (Oxford Univ.)252. Excitation of giant multipole resonances in sd-shell nuclei via medium energy proton inelastic scattering [com­pleted], F.E. B ertrand, C.B. Fulmer, E.E. Gross, D.J. Horen, T .P. Sjoreen (Oak Ridge National Lab), J. Lisantti, D.K. McDaniels, J.R. Tinsley (Univ. o f Oregon), L.W. Swenson (Oregon State Univ.), T .A . Carey, K.Jones, J.B. McClelland, S. Seestrom-Morris (Los Alamos National Lab)254. Total reaction cross sections on nuclei in the 50-80 MeV range [completed], E. Friedman (Hebrew Univ. Jerusalem), D. Gill (TRIU M F), R.R. Johnson (TR IU M F -U B C ), M. Rozon (Univ. of British Columbia), J. Lapointe (Univ. de Laval), A. A ltm an (Tel-Aviv Univ.)255. A study of pion absorption on two nucleons, each from a different shell, through the 180 (7r+ , 2p )16N reaction [succeeded by 328], A. A ltm an, D. Ashery (Tel-Aviv Univ.), R.R. Johnson (TR IU M F -U B C ), H. Roser, R.Tacik (Univ. o f British Columbia), D.R. Gill, U. W ienands (TRIU M F), K. Aniol (California State Univ. LA),C.A. W iedner (M PI, Heidelberg), T . Drake, R. Sobie (Univ. o f Toronto), N. Grion (IN F N Trieste)257. Pion radiative capture in 3He and 15N [deferred], D.F. M easday, F. Entezam i, M.D. Hasinoff, S. Stanislaus (Univ. of British Columbia), M. Salomon, J. Vincent (TRIU M F)258. Radiative decay of the 8 resonance [active], D.F. M easday, F. Entezam i, S. Stanislaus (Univ. o f British Columbia), M. Salomon (TRIU M F)184260. The reaction of muonium w ith hydrogen peroxide in w ater [completed], J.A . B artlett, J.-C . Brodovitch, S.-K.Leung, K.E. Newman, P.W. Percival (Sim on Fraser Univ.)261. Muon spin rotation of param agnetic solutions [completed], J.A. B artlett, J.-C . Brodovitch, S.-K. Leung, K.E. Newman, P.W . Percival (Sim on Fraser Univ.)262. M uonium -radical form ation mechanism [completed], D.C. Walker (Univ. o f British Columbia), Y. Miyake (T R I­UMF), R. G anti, Y.C. Jean (Univ. o f M issouri-Kansas City), J.M. S tadlbauer (Hood College), Y. K atsum ura (Univ. o f Tokyo), D. Livesey (Univ. o f New Brunswick), R. C atterall (Univ. o f Salford), B.W. Ng (W inona State Univ.)263. The pion-nucleus interaction [completed], T .E . Drake, R. Schubank, R .J. Sobie (Univ. o f Toronto), R.R. John­son (TR IU M F -U B C ), D. Gill (TR IU M F )264. The proton-nucleus interaction [completed], R.E. Azuma, L. Buchmann, T .E . Drake, J.D. King, L. Lee, S.S.M.Wong, X. Zhu (Univ. o f Toronto), C.A. Miller, S. Yen (TRIU M F)265. The (p , n ) reaction as a probe of isovector effective interactions at TRIUM F energies [completed], W .P. Alford,R.L. Helmer (Univ. o f W estern Ontario), R.E. Azuma, D. Frekers (Univ. o f Toronto), J. D ’A uria (Sim onFraser Univ.), O. Hausser (TR IU M F -SF U ), K.P. Jackson, S. Yen (TRIU M F)266. Initial studies of the (n ,p ) reaction on light nuclei [completed], K.P. Jackson, S. Yen (TRIU M F), W .P. Alford,R.L. Helmer (Univ. o f W estern Ontario), J.M. D’Auria (Sim on Fraser Univ.), O. Hausser (TR IU M F -SF U ) 17267. Isovector T> transitions in ( fp ) shell nuclei studies by the (n ,p ) reaction [deferred], O. Hausser (TR IU M F - SFU), J. D ’A uria (Sim on Fraser Univ.), K.P. Jackson, C.A. Miller, S. Yen (TRIU M F), A . A ltm an (Tel-Aviv Univ.), W .P. Alford, R.L.Helmer (Univ. o f W estern Ontario), I.S. Towner (Chalk River Nuclear Labs)268. Enhancem ent of 1 + states in 208Pb (n,p): A search for the A [active], K.P. Jackson, C.A. Miller, S. Yen (TRIU M F), O. Hausser (TRIU M F -SF U ), W.P. Alford, R.L. Helmer (Univ. o f W estern Ontario) 17269. Inelastic pion scattering from 30Si a t Tn —* 50 MeV [deferred], C.A. W iedner (MPI, Heidelberg), K. Erdm an, B.Forster, R. Tacik (Univ. o f British Columbia), A . A ltm an (Tel-Aviv Univ.), D.A. Gill, U. W ienands (TRIU M F),T. Drake, R. Sobie (Univ. o f Toronto)270. Test of charge sym m etry by a comparison of ir~d —> nn with 7r+ d —► pp [completed d a ta taking], A.D. Eichon,J. Engelage, G .J. Kim, A.A. M okhtari, B.M.K. Nefkens, J.A. W ightm an, H .J. Ziock (U C LA), R.R. Johnson (TR IU M F -U B C ), G. Jones (Univ. o f British Columbia), A . A ltm an (Tel-Aviv Univ.), W .J. Briscoe, C.J.Seftor, M.F. Taragin (George Washington Univ.), T .E . Drake (Univ. o f Toronto), D.R. Gill (TRIU M F), J.R. Richardson (TRIU M F-U C LA), P. Truol (Univ. Zurich), K. Aniol (California State Univ. L A )271. Study of isovector giant resonances via the (n ,p ) reaction at 200 and 500 MeV [deferred], P.R. Andrews, S.M.Banks, P.B. Foot, B. Lay, P. Lewis, V.C. Officer, G.G. Shute, B.M. Spicer (Univ. o f Melbourne)272. Transverse spin flip probabilities in 24Mg( p ,p ‘) and 48C a{p ,p ') [completed], O. Hausser (TRIU M F-SFU ),R. Abegg, K.P. Jackson (TRIU M F), W .P. Alford (Univ. o f W estern Ontario), C.A. W iedner (M PI, Heidelberg),T.E . Drake (Univ. o f Toronto), J. Lisantti, D. McDaniels, J. Tinsley (Univ. o f Oregon)273. Triplet p~p absorption in H2 gas [letter of intent], J. Bailey (Yale Univ.), G. Azuelos, C. Oram (TRIU M F), J.Brewer, K. Erdm an (Univ. o f British Columbia), K. Crowe (Univ. o f California, Berkeley)274. Singlet final s ta te in te rac tio n in th e pp —*■ pnir+ reaction [com pleted], E .G . A uld, P. C ouvert, G. Jones, W .Ziegler (Univ. o f British Columbia), W. Falk (Univ. o f Manitoba), P. Walden (TRIU M F), G. Lolos (Univ. of Regina)275. Muons in, and muonium from, vanadium [completed], J. Bailey ( Yale Univ.), J. Brewer, J.B . Warren (Univ. o f British Columbia), G. Marshall (Univ. o f Victoria), D. Garner, R. Kiefl, C. Oram (TR IU M F ), A . Olin (TR IU M F -U niv. o f Victoria), D. Harshman (A T & T Laboratories)276. Diluted m agnetic semiconductors [completed], E .J. Ansaldo (Univ. o f Saskatchewan), J. Bailey (Yale Univ.),J.H. Brewer, S. Kreitzm an, D. Noakes, M. Senba (Univ. of British Columbia), R. Keitel (TRIU M F), K.M.Crowe (Univ. o f California, Berkeley), J. Furdyna (Purdue Univ.), Y .J. Uemura (Brookhaven National Lab),T.L. Estle (Rice Univ.), D. Harshman (A T & T Laboratories)277. The branching ratio of the rare decay tt° —* e+ e~ [completed], M.D. Hasinoff, C. W altham (Univ. o f British Columbia), D.A. Brym an (TRIU M F-U niv. o f Victoria), E. Clifford (Univ. o f Victoria), G. Azuelos, T . Numao,J.-M. Poutissou (TR IU M F ), P. Depommier, H. Jeremie, R. Poutissou (Univ. de Montreal), C.K. Hargrove,H. Mes (National Research Council), B. Robertson (Queen’s Univ.), T .A . Mulera, V. Perez-Mendez (Lawrence Berkeley Lab), M. Blecher (Virginia Polytechnic Inst. & State Univ.), A.W . Stetz (Oregon State Univ.)185278. Inelastic scattering of 30 and 50 MeV n+ projectiles from the 0+ sta te in 12C [completed], L. Buchmann,T .E . D rake, L. Lee, R .J. Sobie (Univ. of Toronto), D.R. Gill, B. Jennings (TRIU M F), R.R. Johnson (TR IU M F - UBC), N. de Takacsy (McGill Univ.),279. Non-analog pion single charge exchange to ta l cross section on r Li at low energies [completed], B.J. Dropesky,G.C. Giesler, R.E.L. Green, M .J. Leitch, Y. Ohkubo, C.J. O rth (LAM PF), A . Olin (TR IU M F -U niv. o f Victo­ria), R.G. Korteling (Sim on Fraser Univ.)280. Study of giant isovector spin resonances via the (p ,n ) and (n, p) reactions at 350 MeV [deferred], A. Altman,J. A lster, N. Auerbach, M.A. Moinester, S. Wood, A.I. Yavin (Tel-Aviv Univ.), O. Hausser (TRIU M F -SF U ),A. Moalem (Ben-Gurion Univ.), W .P. Alford (Univ. of W estern Ontario), A. Klein (Univ. o f Georgia)281. Investigations of pion absorption reactions 6Li,12C (x± , X \ ) X 2 [completed], G. Huber, G .J. Lolos, S.I.H. Naqvi,V. Pafilis, Z. Papandreou (Univ. o f Regina), D. Gill, D. Ottewell, P.L. Walden (TR IU M F ), E.G. Auld, G.Jones (Univ. o f British Columbia), R.R. Johnson (TR IU M F -U B C ), X. Aslanoglou (Florida State Univ.)282. Exchange effects in 0+ —> 0_ inelastic scattering [completed], R.E. Azuma, L. Buchmann, T .E . Drake, D.Frekers, J.D. King, S.S.M. Wong. X. Zhu (Univ. o f Toronto)283. (Combined with 295)284. A study of the decays 7r+ —*■ e+ e- e+ i' and 7r+ —► e+v~/ [deferred], M. Blecher (Virginia Polytechnic Inst. &State Univ.), D.A. Bryman (TRIU M F-U niv. o f Victoria), E. Clifford, P. Schlatter (Univ. o f Victoria), M.Dixit, C.K. Hargrove, H. Mes (National Research Council, G. Azuelos, T . Numao, J.-M. Poutissou (TRIU M F),P. Depommier (Univ. de Montreal), A. Burnham , M.D. Hasinoff, C. W altham (Univ. o f British Columbia), T.Mulura, V. Perez-Mendez (Lawrence Berkeley Lab)285. Elastic scattering of pions by 3,4He for pion energies between 20 and 50 MeV [completed], K.M. Crowe, C.A.Meyer (Univ. o f California, Berkeley), D.R. Gill, D. Healey, U. W ienands (TRIU M F), R.R. Johnson (T R IU M F - UBC), A. A ltm an (Tel-Aviv Univ.), N. Grion (IN F N Trieste)286. Q uantum diffusion of muons and muonium [active], K.M. Crowe (Univ. o f California, Berkeley), J.H. Brewer,S.R. K reitzm an, M. Senba, D.L1. Williams (Univ. o f British Columbia), R. Keitel (TR IU M F ), E .J. Ansaldo (Univ. o f Saskatchewan), J. Bailey (Yale Univ.), K. Nagamine (Univ. of Tokyo), D. Harshm an (A T & T Labo­ratories), D.P. Spencer (Univ. o f Chicago Medical Center)287. M easurem ent of parity violation in p-p scattering [active], J. Birchall, C.A. Davis, N.E. Davison, W .P. Lee, P.R. Poffenberger, W .D. Ramsay, W .T.H . van Oers (Univ. o f Manitoba), W .J. McDonald, G. Roy, G.M. Stinson (Univ. o f Alberta), J.D. Bowman (Los Alamos National Lab) 6288. Muonium reaction rates on surfaces [completed], R. Keitel (TRIU M F), J.H. Brewer, D.N. Noakes, M. Senba (Univ. o f British Columbia), K. Nagamine (Univ. o f Tokyo), E .J. Ansaldo (Univ. o f Saskatchewan), D.R. Harshm an (A T & T Laboratories)289. Studies of positive muon states in alkali halides and other insulators by advance /