TRIUMF: Canada's national laboratory for particle and nuclear physics

Annual report scientific activities, 1980 TRIUMF Jan 31, 1982

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TRIUMFANNUAL REPORT SCIENTIFIC ACTIVITIES1980MESON FACILITY OF:UNIVERSITY OF ALBERTA SIMON FRASER UNIVERSITY UNIVERSITY OF VICTORIAUNIVERSITY OF BRITISH COLUMBIA JANUARY 1982TRIUMFANNUAL REPORT SCIENTIFIC ACTIVITIES1980TRIUMF4004 WESBROOK MALL VANCOUVER, B.C. CANADA V6T2A3E X IST IN GPROPOSEDMl 3 (u/p)Ml 1 (tt)M20(y)BATHOBIOMEDICALLABORATORYBLlB(p)FUTURENEUTRONTHERAPYFACILITIESMESON HALLCHEMISTRYANNEXb2 MeV ISOTOPENEUTRONACTIVATIONANALYSISTHERMAL NEUTRON FAC ILITY\  INTERIM RADIOISOTOPE LABORATORYPRODUCTIONCYCLOTRONBL2C(p) BL1AFOREWORDSeveral impressive projects were brought to fruition during 1980. Of noteworthy mention for expanding TRIUMF's capabilities is the successful completion of the Mil fast pion channel for physics research and beam line 2C for radioisotope research.For the first time over 100,000 yAh of proton beam (3.6 mg of protons) was produced by the cyclotron to satisfy both the pure and applied research programs and, with beam line 2C, the cyclo­tron has now demonstrated its capability of routinely extracting three independent beams of differing energies and intensities: a Canadian first and testament to the dedicated efforts of TRIUMF staff. The increasing tempo of the research programs can be measured by the necessity of purchasing a VAX 11/780, to expand the computing power available to experimenters at the main site.TRIUMF was honoured in early spring by a visit of H.R.H. the Prince of Wales who ceremonially initiated the flow of radioiso­topes from the recently completed hot cells of the Atomic Energy of Canada Ltd. (AECL). The hot cells will allow the safe prepa­ration of radiopharmaceuticals from cyclotron-produced radioiso­topes for worldwide distribution to complement AECL's reactor- based products. The applied program scored further noticeable successes during the year as the number of 100 runs increased and commissioning began on radioisotope production facilities on beam lines 1A and 2C.During the year several TRIUMF scientists gave substantial support to two new proposals for Canadian science projects, namely MARIA, a heavy ion synchrotron at the University of Alberta, and CHEER, a high energy electron-proton collider at Fermilab in the U.S.A.If funded the former will be used predominantly for medical research and the latter for high energy particle physics research.H.E. FetchChairman of the Board of ManagementvTRIUMF was established in 1968 as a laboratory operated and to be used jointly by the University of A1 berta, Simon Fraser Uni­versity, the University of Victoria and the University of British Columbia. The facility is also open to other Canadian as well as foreign users.The experimental program is based on a cyclotron capable of pro­ducing three simultaneous beams of protons, two of which are in­dividually variable in energy, from 180-520 MeV, and the third fixed at 70 MeV. The potential for high beam currents— 100 pA at 500 MeV to 300 pA at 400 MeV— qualified this machine as a 'meson factory1.Fields of research include basic science, such as medium-energy nuclear physics and chemistry, as wel 1 as applied research, such as isotope research and production and nuclear fuel research. There is also a biomedical research facility which uses mesons in cancer research and treatment.The ground for the main facility, located on the UBC campus, was broken in 1970. Assembly of the cyclotron started in 1971. The machine produced its first ful1-energy beam in 1974 and its full current in 1977-The laboratory employs approximately 280 staff at the main site in Vancouver and 14 based at the four universities. The number of university scientists, graduate students, and support staff associated with the present scientific program is about 245-v iCONTENTSPageINTRODUCTION 1OPERATION AND DEVELOPMENT OF CYCLOTRON 3Cyclotron Operation 3Cyclotron Development 7RESEARCH PROGRAM 12Introduction 12Particle Physics 147T p ny 14Radiative capture of pions in deuterium 14Transfer effects for stopping tt- in H2-D2 mixtures 15np differential cross section 16Aoj and Aaj_ between 200 and 520 MeV 16Measurement of the it + ev branching ratio 16Muon capture 17The time projection chamber 20Test of charge-symmetry in n-p scattering 22Measurement of the n parameter in muon decay 22Nuclear Physics and Chemistry 23Pi scattering 23Studies of fragments emitted from proton interactions with complex nuclei 24Pion production by proton bombardment of hydrogen and other light nuclei 26Pionic X-rays in light targets 29Bound muon decay in nuclei 29Proton elastic scattering 30p" capture in fissile nuclides 31Studies of (p,d) reactions in nuclei 31Spin-spin interaction 33Elastic scattering of protons from 3He 34Study of two-nucleon correlations in 3He 35Neutral pion production 35Giant resonances 362H(p,y)3He and 3H(p,y)1+He 36Proton-induced reactions on 9Be 37Measurement of the spin rotation parameter R in p-^He elastic scattering 38Quasi-elastic scattering 38A comparative study of the reactions 2H(p,d7r+)n and 3He(p,tir+ )p 39Research in Chemistry and Solid-State Physics 42uSR i n soli ds 42Mu formation and reaction dynamics in the gas phase 49Muonium chemistry in liquids 53Muoniurn formation 55Backward muon reactions 56Applied Program 58Biomedical program 58Isotope production 59Positron emission tomography 60Radioisotope production 61Novatrack 63Theoretical Program 64v i  iPageBEAM RESEARCH AND DEVELOPMENT 78Introduction 78Cyclotron 78Primary Beam Lines 8lSecondary Channels 83Beam Diagnostics 86Computing Services 87CYCLOTRON SYSTEMS 88Ion Source and Injection System 88RF System 89Vacuum System 90Remote Hand ling 91Safety 91Controls 93EXPERIMENTAL FACILITIES 98Introduction 98Meson Hall 98RF Separator 98M9 Extension with dc Separator 98M 11 Channe1 100Thermal Neutron Facility 101Neutron Spectrometer 102Proton Ha 11 102MRS Software Development 102MRS Hardware Development 103Beam Line 4C 103VauIt 104Beam Line 2C 1 04Targets 104Computing Support 105MWPC Faci1i ty 106Superconducting Solenoid Magnet System 107Experimental and Beam Line Magnets 107Liquid Helium Supply 107CONFERENCES, WORKSHOP AND MEETINGS 108Second International Topical Meeting on Muon Spin Rotation (ySR2) 108TRIUMF Muon Physics/Facility Workshop 109TRIUMF Users Group Annual General Meeting 109ORGANIZATION 111APPENDICESA. Pub 1i cat ions 1 1 4B . Users Group 1 1 9C. Experiment Proposals 121vi i iINTRODUCTIONDuring 1980 TRIUMF continued to provide beam for many types of experiments and to develop and improve experimental facilities and ac­celerator components. The integrated current delivered was 110 mAh, just short of the tar­get of 120. New funds, though very welcome and desperately needed, have caused the building program to become continuous with the attendant disruption and downtime for some facilities. The radiochemistry annex was completed and extensions to the proton hall and office building were begun. Prelim­inary plans for major new service buildings such as an extension to the cyclotron vault for the removal and repair of cyclotron com­ponents by remote handling techniques were developed.The winter shutdown ended February 16, with polarized beam available to experiments on beam lines IB and 4B, while work continued on new installations on beam line 1A. Ap­proximately 1100 of the 4250 h of beam time provided to experiments, or 26%, was with polarized beam. This division, similar to previous years, was for the first time caused more by the schedule for construction and equipment installation than by demand. Cyclotron availability dropped marginally to 84% from 88% in the preceding year due in part to a higher rate of component failures and approximately equally due to an increased number of mains-power interruptions. At the beginning of December, a series of major component failures forced a decision to cease delivery of beam to experiments for the remainder of the year. The need for an in­crease in scheduled maintenance and increased emphasis on the program to develop components with increased reliability has been recog­nized and a departure from the exponential growth of delivered beam was planned for 1980 to allow time for developments in remote handling and component reliability. Several goals were, however, achieved on the road to high-intensity operation. Transmis­sion of beam to and through the cyclotron was improved, with an attendant decrease in the residual radioactivity level of the cyclotron. Trials of a liquid helium cryo- pump showed that gas stripping of the H" beam can be appreciably reduced. A brief run with 170 pA delivered to beam line 1A showed that this line can be operated safely at such currents.The extraction of three beams from thecyclotron, one a low-energy beam to serve the new beam line 2C, has been shown to be a routine mode of operation, and the ability of the ion source and injection system to pro­vide the necessary increase in injected beam is established. The need for greater pion intensity for cancer therapy has created the demand for a devoted target and beam line, difficult to provide without compromising plans for expansion of the basic research program. An ingenious combination of strip­per foil development and machine tuning has shown that two beams may be extracted into beam line lAwith spatial separation suffi­ciently large that extraction of one of them into a dedicated line by a septum is simple.In spite of the heavy program of cyclotron and facility development, TRIUMF personnel have found time to aid other laboratories, principally in the preparation of proposals for the new accelerators, CHEER and MARIA.The development of experimental facilities continued throughout the year, the major accomplishment being the installation of the fast pion beam line Mil at target 1AT1 on beam line 1A. Commissioning was not com­plete at the end of the year because of a larger than normal number of start-up prob­lems, many of which stemmed from the septum magnet. M 9 , with its DC separator, produced 'pure' muon beams with little downtime. A RF separator is under construction to replace the DC separator, increasing muon beam in­tensity by a factor of two. Development of the time projection chamber to use this beam proceeded rapidly throughout the year with complete commissioning expected soon. An 8 cm3 polarized proton target was commis­sioned for the nucleon-nucleon program and work has begun on the construction of a 40 cm3 frozen spin target for the charge- symmetry experiment. These and other cryo­genic targets as well as the liquid helium cryopump for the cyclotron demand a reliable source of liquid helium and a liquefaction system was therefore installed.A committee was established to advise manage­ment on solutions to several problems which had been identified in the general area of data collection and on-line display and manipulation as well as data analysis. It was decided to restrict sharply the variety of equipment to be supported by TRIUMF in order to improve service to experiments. AVAX 11/780 was ordered to provide a central data facility with links to many experiments.The advent of the time projection chamber and the beginning of two experiments to mea­sure muon decay parameters with greater pre­cision and the continuation of a precision determination of the pion decay branching ratio marked a swing to particle physics on many of the secondary beam lines, though the demand for beam time for pSR and related experiments was unabated. Nuclear physics and nuclear chemistry programs continued from the preceding year with much new data being pub 1i shed.The applied science program accelerated throughout the year due in part to the in­creased number of high-intensity (100 pA) runs. Several patients were radiated at the pion therapy unit with only one exposure reduced because of machine failure. 123x from the cesium spallation target was delivered to many hospitals, and pilot runs for production of pure 123l from a sodium iodide target on beam line 2C were success­ful. Laboratory quantities of several other isotopes were produced and a number of radiopharmaceuticals were synthesized. Con­struction of a positron emission tomograph (PET) for use at UBC's Imaging Research Centre was undertaken and a laboratory in the chemistry annex was assigned for commis­sioning the instrumentation and initial ex­periments. The 500 MeV isotope production facility was installed in beam line 1A in front of the thermal neutron facility, and several pilot production runs were performed. Unfortunately, the facility causes sufficient scattering and power loss in the beam to reduce seriously the thermal neutron flux in the TNF, with consequent negative effects on the Novatrack activation analysis program.TRIUMF was host to two meetings during the year. A workshop on muon physics and facilities in August was saddened by news of the death of Mike Pearce, one of the founders of TRIUMF. Immediately following the work­shop over 100 scientists from around the world gathered to participate in the Second International Topical Meeting on Muon Spin Rotation at UBC. The third conference in this series is tentatively scheduled for Japan in 1982.The TRIUMF Board of Management, the governing body of the joint venture called TRIUMF by the four founding partners (the University of Alberta, Simon Fraser University, the Univer­sity of Victoria and the University of British Columbia), elected Dr. H.E. Petch as Chairman. The University of Victoria has changed its representation on the Board:Dr. C.S. Picciotto was named to fill the vacancy following the death of Dr. Pearce. After Dr. E.V. Vogt's resignation from the Board, the University of British Columbia nominated Dr. K.L. Erdman to replace him. Changes in Operating Committee membership: J.M. Cameron succeeded G. Roy as the Univer­sity of Alberta's senior member and was replaced by Dr. G.A. Moss as alternate member. The University of British Columbia nominated Dr. M.K. Craddock to replace Dr. G. Jones as senior member and Dr. J.H. Brewer as alternate member. The Experiments Evaluation Committee met twice during 1980 to consider new proposals and review progress on previously approved experiments. The scientists and management at TRIUMF wish to thank retiring members Dr. E.M. Henley,Dr. J.-M. Poutissou and Dr. L. Yaffe for pro­viding their expertise to the committee. We welcome Drs. R.D. Amado and K.P. Jackson as new members of EEC.Financial support for TRIUMF increased from several sources. The National Research Council, the Natural Sciences and Engineering Research Council and the Universities Council of British Columbia (Building Fund) have pro­vided increased funds and further increases are projected as shown in the following table. That TRIUMF continues to receive in­creased grants in a period of severe budget restrictions indicates approval of its pro­grams and its productivity.Mill ions of dollars 1979/80 1980/81 1981/82NRC (capi tal andoperating 9-54 13-50 16.84NSERC (experiments) 1.67 1 .85 2.1UCBC (buildings) - 1-9 4.9**0f the $4.9 M about $2 M is expected to be used in 1981/82, the balance will be spent in 1982/83.2OPERATION AND DEVELOPMENT OF CYCLOTRONCYCLOTRON OPERATIONThis year marked the planned end of exponen­tial growth in the integrated beam from the cyclotron. The goal of 120 mAh was nearly reached with 110 mAh extracted.The shutdown, scheduled for the installation of Mil and the 500 MeV irradiation facility, was extended by four days, and beam operation recommenced on February 16. The work in beam line 1A continued for ten more days un­til February 27 when full facility operation commenced.Beam production was stopped on June 2k for almost two weeks for development and mainte­nance work in parallel with the shutdown of the experimental halls. Construction work started on the proton hall extension to the west, with limited operation during normal working hours resuming on July 7 for a period of almost three weeks. A four-day shutdown was planned for the end of October. This allowed commissioning of new sections of the central controls systems and for extensive maintenance, minor improvements and minor repairs. At the end of November major equip­ment failures occurred, and when quick repairs proved unsuccessful, it was decided to cancel beam production for the month of December. The cyclotron was in operation before Christmas.The operational record is shown in Figs. 1 and 2 and in Table I. Cyclotron availabil­ity in the year was 83-7%, four per cent lower than in 1 9 7 9, and beam was injected for only k8.k% of the yearly total (58.3% in 1979). The main reasons for the worsening of performance were both external and in­ternal. In the former group were interrup­tions and/or transients on the main AC, which caused several substantial delays in site operation, and the construction work in the proton hall. The latter causes resulted from cyclotron systems failing: the insu­lators on the electrostatic inflector- deflector system deteriorated and were re­placed; the main magnet power supply failed following changes to its stabilization circuitry. Most beam time was lost at the end of November when extensive damage to the RF resonator segments required opening the cyclotron and lengthy repairs. As a result the RF system was the major contributor to cyclotron downtime (2 k % ), surpassing ISIS (23.k%) and magnets (10.8%). This is reflected in Fig. 3, where the lower curve (downtime divided by scheduled operating time) indicates the cyclotron reliability in 1980.Figure k indicates the desirable trend in three of the most important operational19 8 0O TH E RSERVICESC O N T R O L SM A G N E TV A C U U MR FI S I S&P O L IS IS168140zo5  120ix ina. 100 O2  80  <LU“  60  u.O40  20 0wccXFig. 1. Operating record fo r  1980.WEEK NUMBER IN 1980Fig. 2. Hours o f  beam operation per week.3Table I. Summary of machine performance 1980.hoursScheduled operating time 7032.0Scheduled maintenance 670.ABeam ava i1ab1e A2A8.2Unpolarized 315A.OPolar i zed 109A.2Cyc1ot ronDevelopment A23.ATuning 365.2Operator training 19.7Beam 1i ne 1ATuning and development 120.3Experiment 2A59.8pA hours 107 A72.0Beam 1ine IBTuning and development 108.0Experi ment 553.5Beam line 2CTuning and development 10.5Exper i ment 30.9pA hours 121.0Beam 1i ne AATun i ng 38.1Experiment 708.8pA hours 1681.0Beam line ABTuning and development 127.9Experiment 1A96.3Beam 1i ne ACTuning and development 190.8Exper iment 258. AIntegrated current 109 27A.0Downt i me 1035.1Cont rols 8 2 .ASafety 5.3ISIS + POL ISIS 2A1 .7Magnets 112.25RF 2A8.7Vacuum 78.05Probes A.8Serv i ces 52. A5Other 208.A5parameters: the total charge delivered(«110 mAh, planned not to exceed 120 mAh), the magnitude of the residual radiation field at the cyclotron centre, and the ratio of the two (lower curve). The latter indicates the total beam transmission in the cyclotron was higher than in previous years due to improved diagnostics, development of better tunes, and greater skills of the cyclotron operators.A new low energy (70-90 MeV) beam line, 2C, received beam for commissioning of the beamFig. 3. Cyclotron u t iliz a t io n  showing (1 ) beam operation per year (hours) and (2) downtime divided by scheduling operating time (%).line elements and the experimental 123I tar­get. Three simultaneous beams were routinely extracted from the cyclotron.Beam tim e a lloca tionBeam operation was scheduled for a total of A02 twelve-hour shifts, 115 of which were polarized {23% ). The number of shifts scheduled to individual experiments is shown i n Table II.>-b->h"O<-I<39COFig. 4. Microompere-hours per year and residual a c tiv ity  in  the cyclotron since f i r s t  beam.ATable II. Beam time to experiments 1980.Area/ Beam Line Exper i ment Short Title SpokesmaniNumber of 12-hour shifts scheduledP polarized beamCYCLOTRON - Development M.K. Craddock 46.5 + IPG. Dutto- Operations M. Zach 1BEAM LINE 1A - Tuning & development G.H. Mackenzie 13P. ReeveBEAM LINE 2C - Development J. Vincent 2BEAM LINE 4A - Tuning & development G. Dutto 2.5BEAM LINE 4B - Tuning & development G.H. Mackenzie 6and MRS D.A. HutcheonBEAM LINE 4C - Tuning & development G. Dutto 6M8 61 B i omed i cal L.D. Skarsgard 148.5 @ 30 yA73 @ 100 yAM9 - Channel commissioning J.A. Macdonald 260 Muonium in insulators J.B. Warren 3571 ySR T. Yamazaki 2489 y fi ss ion S . Ka p 1 a n 22104 TPC D.A. Bryman 39C.K. Hargrove127 Pionic deuterium G.A. Beer 48.5137 Li fet i me of y+ R. Siegel 10138,139 Muons in Ge and AZ K. Crowe 47-5149 Muon phase transitions M. Doyama 10154 Muoni um in soli ds J. Brewer 12160 Muon studies of magnetic C. Huang 14superconductorsMl 3 1 ir-scatter i ng R. Johnson 17-59 i r ” p  - y  y n D.F. Measday 2052 tt ■> ev D.A. Bryman 10760 Muonium in insulators J.B. Warren 2671 ySR T. Yamazaki 2480 Pionic X-rays R.M. Pearce 1111 1 i t ”  absorption C. Cernigoi 22118 (ir,2n) on light nuclei R.R. Johnson 43134 ri parameter in muon decay K.M. Crowe 16.5138,139 Muons in Ge and A£ K.M. Crowe 4145 tt ”  capture in 165Ho and Y . Lee 9181TaM20 70 ySR in soli ds J. Brewer 971a ySR T. Yamazaki 571b ySR T. Yamazaki 878,154 Muonium in metals and T. Yamazaki 7sol ids J. Brewer88 Total muon capture T. Yamazaki 21122 ySR in cobalt B.D. Patterson 19.5147 Gaseous muonium D.G. Fleming 60150 Backward muon reactions P. Percival 79157 Muon i um chemi stry D. Walker 72.5BEAM LINE IB 10 it  production G. Jones 107-5P87 Proton radiography E.W. Blackmore 6 + 2PBEAM LINE 2C ~ Tests and production J.S. Vincent 4.55BEAM LINE AA _ Tun i ng G. Dutto 2.51 1 High neutron nuclides J.M. D'Auria 8A8 Ferficon 1.M. Thorson 377 123I production J.S. Vincent 28.5115 Pion production J.M. D'Auria 3117 Light fragments R. Green 8.51A2 Fragments R.G. Korteli ng 151A3 Recoi1 K.P. Jackson 38- Isotope production B.D. Pate ABEAM LINE AB - Tun i ng G.H. Mackenzie 5- MRS G. Rogers 10D.A. Hutcheon86 Scattering from Ca + Pb J.M. Cameron IIP99 (p,d) reactions J. K'allne 5103 Spin dependence G. Roy 16P113 (p,p) at 3He at backward G.A. Moss 1 IPangles11A (p,2p) in heli urn W.T.H. van Oers 30117 Light fragments R. Green 812A Giant resonances F. Bertrand 20131 (p,y) on 3He and 6Li A.W. Stetz 15-5 + H P1A2 Fragments R.G. Korteling 81 AA Polarized pd reactions J.M. Cameron 1 + 7.5P152 p - ^He elastic scattering G.A. Moss 3155 (p,2p) in lt0Ca P. Kitching 5 + 12P158 pd -* diT+ J.M. Cameron 17-5162 X^ray production by p B. Johnson 13BEAM LINE AC 130 (p,p) scattering D.A. Axen 16 + A5.5P6CYCLOTRON DEVELOPMENTThe upgrading of the cyclotron system toward more reliable beam production and new beam capabilities continued gradually through 1980 with emphasis given to improved energy reso­lution, higher average current and new ex­tracted beams. The peak currents obtained in 1979 were confirmed and new schemes of polarized beam formation were investigated.H ighe r energy re so lu tionThe AE/E = 1/1000 'medium energy resolution beam' was available to experimenters during the second part of the year. Although this mode of operation still requires extensive assistance by beam physicists, the set-up time has been reduced from 20 to 6 h .Operator training has begun. Instructions have been written and operator set-up will soon be routine.The ultimate goal of an energy spread of 100 keV at all TRIUMF energies implies single turn extraction up to 520 MeV. An energy resolution of 100 keV has already been demon­strated at 200 MeV and single turn extraction has been achieved up to 250 MeV. To achieve the ultimate goal, work proceeded toward the following three requirements:1) beam phase stability of ±2°;2) RF voltage stability of ±25 ppm; and3) flat-topping of the RF fundamental wave form with the addition of a third harmonic component.Note that the achievement of these goals is also beneficial for purposes other than 100 keV operation: for example, the stability of the split ratio between extracted beams and other features, such as external beam emittances and halos, which depend on the internal beam geometry. A constant beam phase is desirable for some of the time-of-f1ight spectrometers. In addition, operation with the third harmonic will be beneficial for high intensity operation since it will increase the cyclotron acceptance while re­ducing internal beam spills.During 1980 highest priority was given to the stabi1ization of the beam phase. The stabiliza­tion scheme uses three simultaneous software loops based on signals derived from the main magnet field and from the extracted beam phase. Long-term (~5 min) drifts in the magnetic field were reduced from ±10 ppm to ±3 ppm using the signal from a cyclotron NMR probe,which was found to survive the effects of radiation for a period of six months. Work to improve the sensitivity of this probe and to decrease the radiation damage to the front-end electronics is in progress. To correct for faster fluctuations in the mag­netic field, the RF frequency was adjusted to follow these drifts, keeping the beam phase constant. Two parallel loops were used here. In the first, the voltage in­duced in an outer trim coil was digitally integrated to produce the required error signal in a fast (10 Hz) loop. In a second loop (0.3 Hz), the beam phase signal ob­tained from a capacitive probe installed in beam line 1A, with the high frequency com­ponents removed, was used to provide the error s i gnal.The combined action of the three feedback loops is shown in Fig. 5- The beam phase on an external beam line, the time of flight through the machine and the integrated EMF of trim coi1 5^ are recorded versus time. A phase stability within ±2° was achieved and maintained for a period of ~2 h. For opera­tional purposes ( z2k h) the stabilization loops are being implemented with dedicated CAMAC-based microprocessors. Phase signals from polarimeters or other adequate counters will be used instead of the capacitive probe signal when extracting low intensity polar- i zed beams.Work continued on the internal phase measur­ing system, which uses the 1 kHz structure of the beam to separate beam phase informa­tion from high levels of RF pickup on the probes. A quadrature detection method is used to track fluctuations in the beam time profile which are induced by instabilities in the RF voltage. For the external capaci­tive phase probes, a fast beam integrator was developed for the front-end electronics, thus allowing the zero cross discriminator to be replaced with a constant fraction di scrimi nator.The jitter in the time of flight in Fig. 5 is mainly due to fluctuations in the RF voltage. At the time of these measurements the voltage stability was worse than ±2/1000. This was due to the fact that spe­cial rigid tip connections between resonator panels, which were designed to reduce resonator vibrations, had to be removed in order to eliminate the possibility of RF cross currents in the beam gap. Special connections designed to provide rigidity and at the same time proper electric contact at75°PHASE2 jisecT.O.F5 ppMTC54FEEDBACK OUT FEEDBACK INFig. 5. E ffec t o f  software feedback loops on the beam phase, time o f  f l ig h t  and magnet f ie ld  (as measured by trim  c o i l  #54).the tips have been designed and will be in­stalled during the spring 1981 shutdown. The RF voltage stability should then again be better than ±1.5 x 10-1+, as previously demon­strated. For further improvements, feedback from a beam position sensor may be used to regulate the RF voltage.The progress on the third harmonic amplifier is reported in detail in the RF report. By the end of the year the commissioning of the amplifier was well in progress. (At the time of writing this report, the amplifier was successfully tested to full power into the dummy load.) It is expected that the third harmonic amplifier will be tested in the main cavity at full power during 1981.H igher average in te n s ityThe total beam charge delivered during 1980 was 110 mAhwith 73 twelve-hour shifts being dedicated to 100 yA operation. This allowed several biomedical experiments to take place. In a typical mode of beam production (aimed at satisfying the requirements of the medical users while maintaining the total integrated current at acceptably low levels) the beam current was raised to 100 yA during mornings for patient irradiation, and reduced there­after to 20-30 yA for the physics users. Although the time required to increase and reduce the current between 30 and 100 yA was only of the order of one or two hours, this mode of operation was found undesirable bythe physicists due to discontinuity in ex­perimental set-up conditions.It is planned to increase the total yearly integrated current to 300 mAh in the next few years. At present the major limitation to an immediate increase derives from the requirement of keeping the residual activity levels in the cyclotron tank and around the extraction beam lines low. A detailed man- dose prediction study completed for all regions inside the vault indicated that in­creasing the yearly integrated current to 300 mAh would provide a five-fold increase in residual activity if present conditions are extrapolated (Fig. 6). The vault-dose study resulted in the following strategy:1) Most of the developments and improve­ments in the tank and around the front-end sections of the beam lines should be com­pleted within the next three to four years, before the activation levels reach satura­tion. This will include modifications and additions aimed at realizing the cyclotron's full capability and improvements for relia­bility and the remote handling of components. The radiation exposures required for these developments should decrease in three to four years, and exposures required for maintenance should be reduced by at least a factor of two as a result of appropriate i mprovements.Fig. 6. Predicted radiation levels at the centre o f  the cyclotron vacuum tank (with shadow shields in ) assuming a two-month shutdown per year and an integrated beam o f  300,000 vAh/year a fte r  1983.2) Another reduction (by at least a factor of two) in exposures will be obtained by re­ducing beam losses in the cyclotron tank.This requires that most of the high intensity operation be performed at 450 MeV extraction energy. The beam current will have to be increased by about 50% in order to maintain the same pion production rate in the meson channels but the electromagnetic stripping loss, which is at present the main contribut­ing factor to the tank activation, will be reduced from ~9% to ~2% of the total beam current.Various steps were taken toward the implemen­tation of this strategy. A cyclotron mechan­ical engineering group was formed to re­evaluate all components from a point of view of reliability and handleabi1ity. The design effort included the new resonators, cooling headers, probes and new extraction mechanisms. The front ends of the 1A and 4A beam lines were redesigned to be compatible with remote handling and with higher radiation levels.On the other hand a detailed analysis of the various contributions to beam spills in the tank was performed. Previous calculations for both electromagnetic and gas stripping were compared with measurements,and the esti­mate of the overall reduction in residual activity, achieved by extracting at lower energies, was based on measured vacuum par­tial pressures and measured pion production rates.The contribution of gas stripping at a nitro­gen-equivalent stripping pressure of 5 x 10-8 Torr was found to be ~7% of the total beam current or ~2.5% of the total beam power. At 450 MeV gas stripping therefore becomes a substantial fraction of the total loss andgood vacuum conditions become mandatory.All significant air, nitrogen and water leaks must be eliminated immediately after their occurrence to maintain the vacuum at the 5 x 10-8 Torr nitrogen-equivalent pres­sure, achievable wiith the present pumping system. At this level hydrogen appears to be responsible for about 60% of the total gas stripping. A 25,000 i / s e c  liquid He cryopump, installed in the tank and tested for short periods, was found to reduce the hydrogen partial pressure by a factor of three. It is expected that the operational implementation of this pump, which still requires modifications for long-term relia­bility, will reduce the beam loss due to gas stripping from 2.5% to about 1.5%, and the total beam loss at 450 MeV from 4.5% to 3-5% of total beam power. It is assumed in these considerations that all stripping due to poor beam tuning or to poor injected emittance conditions will be avoided.Further details on this analysis are con­tained in the Beam Development section (p. 78).Reliable operation at 450 MeV requires, in addition to optimum vacuum conditions, higher injected beam currents and good reproducible beam tunes in the cyclotron and along beam line 1A. Work has proceeded in both. By the end of the year the high in­tensity source and the tune for 450 MeV were available for operational use.The progress on the reliability and remote handleabi1ity of components inside and out­side the tank is described in the group reports. By the end of the year several modifications for easier remote handling were introduced in the vault section of beam line 1 and in the resonator system. The design and construction of the new resonat­ors progressed during the year, although progress was not as great here as had been hoped for due to manpower and work shop 1imitat ions.The study of various phenomena related to the tuning of the resonating cavity was carried out and several tuning shifts were used by the RF group. The low RF impedance of the beam gap in the region of resonator segments 7 and 8 is deemed to be responsible for most of the RF coupling between RF gap and beam gap, causing leakage and heating effects. Various solutions were proposed to alter the geometry in this region (for instance, corrugated panels or resonator segment extensions). It was decided to9study the feasibility of these solutions in a 1:2 scale model, which was designed and is being constructed.Beam extrac tionThe situation for the beams extracted from the machine can be summarized as follows (see Fig. 74, p. 78):Beam line 1 and beam line 4 are used for pro­duction on a routine basis, although modifi­cations for high intensity have been proposed and will be introduced in the vault sections during the spring 1981 shutdown.Beams with currents up to about 4 yA were extracted from the 2C port at energies of ~70 and ~100 MeV using stripping foils insertable at different discrete radii. A conceptual design of a movable stripping foil, which will allow the energy to be varied continuous­ly between 70 and 100 MeV, has been developed.By the end of the year the front end of the line including the combination magnet, a quadrupole doublet and a switching magnet was assembled in a separate set-up area. This system was aligned with respect to supporting positioning frames, tested for remote handle- ability and was ready for installation during the spring 1981 shutdown.The conceptual design for the front end of beam line 2A (a 400-500 MeV, high intensity beam line feeding a proposed third experimen­tal area and/or kaon factory) was finalized and detailed design has begun. The stripping foil mechanism was designed in detail and various components were ordered.A special stripping foil on beam line 1, with two fingers separated radially, was prepared in order to obtain a beam, with two components occupying different regions in phase space. Proper focusing will separate these compon­ents spatially and allow the introduction of a special septum to direct the beams to dif­ferent users. This special mode of operation would direct 100 yA toward 1AT2 for the physics users and 20-30 yA toward a special station in the medical annex for a high angu­lar acceptance pion channel.H ighe r peak in te n s itie sThe final goal is approximately 500 yA beam at 500 MeV which will be available for limited periods of time to medical or physics users. Continuous operation at these intensitiesshould be available at 450 MeV, provided the exposure requirements of maintenance were low enough to allow it. There are other im­portant reasons for increasing the injected peak current:1) The extraction of a substantial(<100 yA) fraction of beam at 70-100 MeV for isotope production on beam line 2C will become possible.2) Higher intensities (up to 100 yA) will be achieved on the 1:5 selector mode, where four out of five beam bunches are suppressed in order to increase the time separation between bunches from 43 to 2 1 3 nsec.3) It will be possible to reduce the in­jected beam emittance or the time duration of the beam bunches even further, with reduced spills and halos, and gain more reliable 100 yA operation as a consequence. One could envisage raising the current through the medium energy resolution defin­ing slits with enough current to be able to operate a medium energy resolution beam and meson production simultaneously.4) 400 yA will become available at 400 MeVfor continuous extraction (from beam line 2A) and may be used for injection into a kaon factory or other post-accelerator.There is no electromagnetic stripping, therefore no additional tank activation, by extracting at 400 MeV. Simultaneously100 yA would be extracted down beam line 1A.During the first part of 1980 the 150 yA capability of the cyclotron was reassessed with a test run lasting a few hours. Cool­ing problems in the 1AT2 target area, which previously had been limiting the 150 yA test to a few minutes, appeared to be solved. Tests to higher dc currents, requiring an extension of the licence from the Atomic Energy Control Board, were temporarily dis­continued. However, the work aimed at im­proving the H" source continued in the laboratory.The model source test stand was improved through the installation of a new optics box to study the emittance and the characterist­ics of the 12 keV beam. In addition, a 25 kV power supply to explore higher extrac­tion voltages, and a filament power supply with a feedback system stabilizing the arc current, were installed and commissioned. As a result of these improvements, systematic studies were possible and an almost10immediate consequence was a factor of two in­crease of the beam current through the very small acceptance slits used for 100 pA opera­tion (0.1 5it mm-mrad in both directions).i.2 mA were transmitted through these slits. At the beginning of 19 81 a current of 650 pA, which is compatible with 200 to 300 pA extracted, was maintained at the en­trance of the main machine for several hours in a stable manner.Extracting 500 pA to the TNF in a dc mode will require a new TNF target system, with forced convective cooling of the target. The conceptual and detail design of this system has started, and it is expected to be installed and tested by spring 1983 -H igh in te n s ity  po la rized  beamsAt present the polarized beam operation is limited to a few hundred nanoamperes of ex­tracted beam current and precludes any signi­ficant use of the meson channels and the beam for applied programs. In view of the contin­uing and increasing demand for polarized beam operation at higher polarized currents, and for simultaneous production of 20-30 pA cur­rents for meson physics and applied programs, it was decided to explore the possibility of developing at TRIUMF a high intensity H" ion source called I PH IS (intense polarized H- ion source).A number of possibilities were considered.It was concluded that a scheme proposed by L.W. Anderson of the University of Wisconsin [Nucl . Instrum. Methods 16 7 , 363 (1979)] appeared to be the most promising technique for satisfying TRIUMF's future requirements.This type of ion source would use circularly polarized light at 589. 6 nm (sodium D1 line) from a high power dye laser to polarize a sodium vapour target. Protons, at 5 kV, passing through a sodium vapour will, with a relatively large probability, pick up a polarized electron through the charge ex­change reactionH+ + Na -v H° + Na+ .The electron will maintain its polarization provided that this reaction takes place in a strong magnetic field. Calculations indicate that very substantial beams will result from today's high power lasers and an intense proton source. The zero-cross Sona tech­nique, presently employed in the TRIUMF Lamb-shift type polarized source would then be used to produce an atomic hydrogen beam with a nuclear polarization. A second charge exchange between this beam and a sodium vapour would produce a beam of polar­ized H". Currents of 50 pA to 60 pA from the source are predicted.This scheme is being explored simultaneously at LAMPF and KEK. Close contact is being kept with these laboratories. In view of the fact that TRIUMF is actually the laboratory which could profit most from the new source, due to the H~, full duty cycle, simultaneous high intensity and polarized beam require­ments, it was decided to give high priority to the investigation of this source through an experimental model study. During the year orders were placed for a number of com­ponents which have long delivery times. It is hoped that assembly of the prototype source can begin in May 19 81.RESEARCH PROGRAMINTRODUCTIONThe availability of the cyclotron in 1980 (8*+%) was approximately the same as the pre­vious year. However, this year marked the end of exponential growth in the integrated beam extracted from the cyclotron, with only a 50% increase (from 83,000 yAh to 110,000 yAh) over 1979- This situation will continue until the cyclotron and primary beam lines are upgraded to allow them to be maintained by remote handling techniques.A new beam line, denoted beam line AC, was installed in the proton hall, commissioned and used by the BASQUE group in conjunction with TRIUMF's first polarized target (a second is under construction for the charge symmetry experiment). The beam line was used to transport femtoamperes of high quality polarized beam to the target for total cross- section measurements. In the meson hall the dc separator was used for the first time on M9 and produced transversely polarized muon beams for ySR experiments. The Mil, fast pion channel neared completion.With the current interest in dibaryon reso­nances the BASQUE group began their program to determine the inelastic components of the nuc1eon-nuc1 eon scattering matrix by measur­ing the spin-dependent total cross sections Act|_ and Aay at seven TRIUMF energies. The results will be compared to previous measure­ments at the ZGS which were at variance with the prediction of the BASQUE group's phase- shift analysis. Measurements below the pion production threshold must agree with phase- shift analysis as there is zero inelasticity. A study of the spin dependence of pp -* pntr+ will be undertaken to help further determine the inelasticity parameters.Polarized beam was again in great demand, with 30% of the available experimental time devoted to this mode of operation. In the meson hall the (p,ir) group used their im­proved detector system to measure the angular distribution of da/dfi and Ay in 9Be(p,ir+ ) 10Be and 9Be(p,Tr-) 10C to low-lying states, at several energies. In the proton hall several groups are now regularly using polarized beam in nuclear physics experiments. The differ­ential cross section and polarization were measured for lead at several energies and were shown to be at variance with a second- order KMT multiple scattering predictionwhich successfully describes higher-energy data. The study of da/dfi and P (p,d) in light nuclei shows a j-dependence for the orbital of the picked-up neutron. In addi­tion do/dn, P and D were measured to the ground and second excited state by scattering polarized protons off beryllium and observing the polarization of the outgoing proton (for D) . In the lighter nuclei da/dfi and P were measured at several energies and over a wide angular range for 3He(p,p)3He and 2H(p,y)3He. Cross sections for the inverse of the better reaction are still in disagreement by a factor of 1.5 and have been interpreted as a possible feature of time-reversa1 invariance.The secondary channels for pion and muon ex­periments were fully utilized, with prelim­inary results becoming available for ir-p-> yn at 27.A and 39-3 MeV, and a more precise (2x world present) measurement of the ratio (tt_d -* nn) : (tt d -+ ynn) . The latter experi­ment is part of a series of checks on the Bruckner-Serber-Watson relations for low- energy pions. The pion scattering group mea­sured the ratio of cross sections for 26Mg: 21*Mg, 7li :6 L i and l:lB:12C to extract neutron radii. The latter result was seen to have an energy dependence which was ascribed to an incorrect description of absorption in the optical potential. For stopping pion experi­ments, the energy and width of 2p-ls transi­tions in isotopes of boron, carbon and neon were measured. Late in the year a sample of the rare isotope 36S was obtained and the 3d-2p transition observed. The 2p level energy shift and width will be extracted from the data.Muons continued to be both a useful tool in particle and nuclear physics research in addition to themselves being intrinsically interesting particles to study. Last year problems in the precise measurement of the muon lifetime were eliminated allowing one group at TRIUMF to undertake the largest single survey (58 elements) of muon lifetimes in solids. Strong isotope effects were ob­served in muon capture on Li, B and 0 but none were seen in C. Last year an 18 nsec component was observed in muon cap­ture by the finite nuclide 238U. A repeat of the experiment tagging each captured muon by the observance of the muonic K X-ray gave no evidence for the 18 nsec component while12reproducing known prompt-to-delayed yield ratios and lifetimes. However, it was ob­served that prompt fissions were missing when fissions were correlated with K X-rays. An experiment to measure the q parameter (one of the parameters in the Michel spectrum) in muon decay received its first beam time this year. Several more experiments are scheduled to run in the near future investigating the intrinsic properties of the muon and the validity of the electroweak interaction.The research under way in 1980 using muons for studies of chemistry and solid-state physics was as rich and varied as in previous years. As usual no attempt will be made to summarize or describe all of the diverse ex­periments carried out, but those involving muonium formation are topical. The first ob­servations of muonium formation in the liquid and solid phases of Ar, Kr and Xe were made and high formation fractions were measured. Epithermal muonium was also observed leaving a thin gold foil irradiated by p+ , but no quantitative estimates of the yield were made. For the muonium-to-antimuonium conver­sion experiment, muonium was generated using silica powder on collodion films and allowedto diffuse into the surrounding vacuum. The result of Gm u M u' < ^2 Gperm| represents a con­siderable improvement on the existing measurements.The theory group, bolstered by local univer­sity staff, research associates and a healthy number of short- and long-term visitors, made many contributions to the areas of research under way at TRIUMF. In particular, the recent interest by experimental groups and theorists in A's in nuclei and pion produc­tion has resulted in investigations of the ird, NN and NNir systems using the known elas­tic NN phase shifts as input data. Further­more, an extension to the MIT bag model has succeeded in reproducing Gpn (q2) well. Also a study of the possible areas of research at a kaon factory began with an investigation of ZN interactionsand Z hypernuclei.Finally some spin-off from theoretical nuclear physics came when a rate of 21 x 10-3Lf cm6/sec was calculated (in impulse approximation) for the recombination of atomic hydrogen, compared to a recent measurement at the University of British Columbia of 28 x I0~31+ cm5/sec.13PARTICLE PHYSICSE xperim ent 9 n~ p ■* nyAn initial run has been completed on a study of the reaction tt"p -> ny using the M 13 chan­nel. The Nal crystal TINA was used to detect the y-rays produced by a tt" beam incident on a liquid hydrogen target. The pion energies were 27 .k MeV and 39-3 MeV (in the centre of the target). The energy resolution of TINA was quite adequate to separate the capture y-rays from the more prolific y-rays from the decay of neutral pions produced in the charge exchange reaction (ir-p -*■ n°n) .The analysis of the charge exchange reaction at 2 7 - MeV has been hampered by a small percentage of tt- which stop in the target and produce a y-ray background which is magnified by the fact that every stopped pion produces a y-ray whereas less than ]% of passing pions produce a y-ray. There are indications, how­ever, that this background can be subtracted30 90 120ANGLE (CM)150 160Fig. 7. Angular d is tribu tions fo r  the reaction ir~p -* ny at T  ^ = 27.4 MeV and 39.3 MeV. The cross sections have been converted via deta iled balance to the values fo r  the time reversed reaction yn it-p. The curves correspond to the m ultip le analysis o f  Smith and Zagury (S&Z) and the ca lcu lations o f  Woloshyn (RW) and Blomqvist and Laget (BL).without too serious an impact on the accuracy of the determination of the charge exchange scattering length.The capture reaction has been analysed satis­factorily at both pion energies, and prelim­inary results for the differential cross section are given in Fig. 7- The results (plotted as cross sections for yn -> ir-p) are compared with calculations by Woloshyn and by Blomqvist and Laget, and the agreement is satisfactory. The disagreement with the multipole analysis of Smith and Zagury is not understood. The total cross sections (for yn -»- ir"p) are given in Fig. 8, compared to previous data as well as to the calcula­tion of Blomqvist and Laget. The present results are in excellent agreement with the calculations and are considerably more accurate than the previous experiments. The main advantage has been the simplicity of the technique.Further runs are envisaged when Mil becomes operational in the summer of 19 81. This method should give excellent results up to a pion energy of 100 MeV and could be useful up to 150 MeV as long as the energy resolu­tion of TINA can be kept at the value obtained in a recent ir+ -> e+v experiment.E xperim ent 41aR adiative capture  o f p io n s  in deuteriumThis experiment was part of a series of checks of the Bruckner-Serber-Watson rela­tions for low-energy pions. This particular measurement was of the S-ratio for stopped pions in deuterium where:S _ m (tt~d -> nn)<o(ir”d ■+ ynn)Negative pions are stopped in a high pres­sure gas target and the number of gamma- rays which are produced is measured in the large Nal crystal TINA. Pions are also stopped in hydrogen gas in order to cali­brate the detection efficiency of the arrangement.The analysis of the data has been completed and the result is 2.83 ± 0.04, which is a factor of two more precise than the best existing measurement. A paper has been prepared and submitted for publication.]kFig. 8. Total cross sections fo r  the reaction yn -*■ ir~p compared to the ca lcu la tion  o f  Blomqvist and Laget. A l l  the illu s tra te d  experi­ments were on the time reversed reaction w-p -* yn.u) (MeV)E xperim ent 140Transfer e ffe c ts  fo r s topp ing  n~ in H2-D2 m ix tu resIt has been observed by several experimenters, when negative pions are stopped in a mixture of hydrogen and deuterium, that the pion is liable to be transferred to the deuterium. In liquids this effect appears to be quite large and about half of the pions can be transferred. One series of measurements has been completed in gas mixtures using a high pressure gas target, and it has been found that up to 20% of the pions can be transferred, which con­firms an earlier Russian measurement. The transfer probability Q is plotted in Fig. 9against the deuterium concentration for H2-D2 mixtures and appears to reach an asymp­totic limit of 20%. The effect is indepen­dent of pressure. The curve marked PP is a fit to the data obtained by Petrukhin and Prokoshkin [Sov. Phys.-JETP 29., 2Th (1969)].It seems that the most likely explanation for the discrepancy is that an HD molecule captures negative pions in a unique way, and quite differently from H2-D2 mixtures. We are therefore preparing to manufacture some HD gas in order to investigate the capture probability as a function of pressure in this exotic gas.Fig. 9. The transfer probab ility  from hydrogen to deuterium fo r  a it- stopping in  a R2-T)2 gas mixture The e ffe c t is  independent o f  pres­sure in  the experimental range o f  10 to 100 atm. The curve is  a f i t  to the results o f  Petrukhin and Prokoshkin.15E xperim ent 26 np d iffe re n tia l cross sectionOff-line analysis of the neutron proton dif­ferential cross-section data proceeded throughout the year. Data were taken over the c.m. angular range 10° to 180° and at the four energies 220, 330, ^30 and 500 MeV. In addition measurements of the np total cross section and of the reactions np ■* dir0 , np -> nnir+ and np -> ppw- have been analysed. This work provided the basis of two Ph.D. theses that were successfully defended during the course of the year. The final data are presently being prepared for publi­cation.E xperim ent 130hoT and AoL betw een 200 and 520 MeVHaving commissioned the new low intensity beam line 4C and the polarized proton target, the BASQUE group mounted two experiments to measure pp spin-dependent total cross-section differences: using transversely polarizedbeam and target, Aaj = a(+f) - a(t+), and with longitudinally polarized beam and tar­get, Ao|_ = a( t )  - cr(^).Measurements made at the Argonne ZGS had aroused interest in the possible existence of dibaryon resonances, in apparent dis­agreement with phase-shift predictions derived from previous BASQUE and world data. Therefore, measurements were undertaken across the available energy range of TRIUMF with particular attention being paid to systematic errors.A conventional transmission method was used.A monitored flux of 3 x 105 polarized pro­tons per second were incident on the polarized target within a 10 mm diam beam spot. The beam was accurately centred on the cylindrical polarized target volume (15 mm diam by 2k mm long). The beam pol­arization was monitored by a polarimeter in beam line k l\ . The polarization of the tar­get material— 35% butanol, 5% water plus EHBA dopant— was calibrated by detecting elastic scattering asymmetries from protons in the target and monitored independently by an NMR system. The transmitted beam was detected in the transmission array consist­ing of six circular scintillators plus two downstream efficiency counters.Systematic checks related to beam focusing, alignment and intensity, plus spin reversal1I 51 , ,400 500 MeVi *iiIi i______i_______ i200 300 400 500 MeVFig. 10. Spin-dependent to ta l arose sections in  pp e la s tic  scattering over the TRIUMF energy range, which includes the pion production threshold (290 MeV).of beam and target, were performed. Prelim­inary results for Aaj and Act(_ are shown in Fig. 10. The results are still subject to an overall normalization correction. Off­line analysis is continuing.Experim ent 52M easurem ent o f the n -*• ev branch ing  ra tioFurther measurements of the branching ratio^ _ T (it ->- ev + ir -> evy)T (tt -> yv + tt -* pvy)were undertaken at TRIUMF this year. They were intended to provide a detailed check of the Weinberg-Sa1 am model concerning electron- muon universality, which yields a firm pre­diction of this ratio at the 0.3% level.The method makes use of the uniform efficien­cy of the large Nal(T&) ('TINA') crystal to separate the 70 MeV electrons (e^) i n it •* ev decay from the 0-53 MeV electrons (ey) due to the tt -> pvy and eveVy chain. The experimen­tal configuration is shown in Fig. 11, where­in it's stopped in the scintillator sandwich in the target B3-B7 and subsequent decay electrons were detected in TINA. The measuredAaTmb1086420AcrLmb-12-16-20-24-28200 30016T1B 3 -B 7B8MWPC1 -3Fig. 11. tt -*■ ev apparatus configura tion . The t\+ beam stopped in  s c in t il la to rs  B4-B6 and the decay positrons were detected in  TINA a fte r  triggering  T1T2T3.ratio is independent of such experimental parameters as solid angle and absolute number of tt stops.Several improvements over previous measure­ments were made. The experiment was run on the Ml 3 tt/p channel, which has a momentum resolution of about 1% and small spot sizes of about 2 cm. 75% of the tt beam stopped in the middle scintillator (1/16 in. thick) of the target. The loss of decay y's from the target was negligible and the great majority of electrons triggering TINA were from the target area, and collimators were unnecessary.Significant improvements were made in the processing of the signal from the TINA crys­tal by passively adding the dynode signal into a preamplifier, followed by amplifica­tion into a precision ADC. A resolution of 5.5% was found for the ew monoenergetic peak, enhancing the separation of the e ^ 1s from the eu Michel edge over previous measurements.The response function of TINA was measured as a function of energy in July, together with a test set-up of the irev measurement. Final data were taken in the period of late August to early November in which approxi­mately 30,000 tt -*■ ev events were recorded. Figure 12 illustrates an electron spectrum from this run. The e^ electrons were well separated from the e ^ .Tests are currently being performed on the data to gain a full understanding of the systematic effects on the branching ratio.Fig. 12. Electron spectrum o f tt -»• ev and it -* p -*■ e decays.E xperim ent 88 M uon captureAs indicated in last year's annual report the systematic problems inherent in the precise measurement of muon lifetimes were investi­gated and eliminated by a careful study of the free y+ lifetime. The main problems concern the proper unbiased electronic treatment of both muon and electron pile-up and the determination of the background con­tribution. The final configuration of the electronic logic produced a reasonable value for the y+ lifetime, which was measured to be 2 1 9 7 - 0  ± 0.7 nsec (in good agreement with the accepted value of 2197-120 ± 0.077 nsec) and it is now possible to make routine measurements of y~ lifetimes to accuracies of about 1 nsec.During 1979 and 1980 the group has utilized the low contamination 'backward muon' beam from the M20 channel to measure lifetime values (and hence capture rates) for 58 ele­ments including four pairs of separated isotope targets. This represents the larg­est single survey undertaken by any group and eliminates the systematic uncertainties when comparing measurements made by different groups.Table III gives a summary of our results.An accuracy of 0.5-1.0% was obtained for the capture rates in most elements. Several of the results are particularly interesting. Strong isotope effects were observed in Li,B and 0; however, no isotope effect was observed for carbon. This is in disagree­ment with the predictions of the Primakoff theory (which uses the Pauli principle and the closure approximation), but in agreement with the more recent predictions of Desgrolard which uses the impulse approxima­tion and shell model wave functions to cal­culate the major partial capture rates.17Table III. Results of lifetime measurements. (Mean lifetimes of TRIUMF are determined by electron and neutron spectra.) (Lifetime in nanoseconds)z Element Mean Life (TRIUMF)Capture Rate (xl0‘ s'1)Mean Life (Others1)Mean Life (TRIUMF-neutron)3 Li-6 2177.0+2.0 4.1810.45 xlO'2 2175.310.4(* )Li-7 2188.3±2.0 1.8110.45 xlO'2 2186.810.4(* )4 Be 2162.1+2.0 7.3510.45 xlO" 2 2153 195 B-10 2070.7+3.0 2.8110.07 xlO'2 2082 +6B-ll 2096.1±3 .0 2.2210.07 xlO’2 2102 166 C 2026.3±1.5 3.8810.05 xlO'2 2034 14C-13 2029.1±3 .0 3.7710.07 xlO"27 N 1906.8+3.0 6.93+0.08 xlO" 2 1927 1138 0 1795.4+2.0 10.36+0.04 xlO"2 1812 1100-18 1844.0±4.5 8.8010.15 xlO-29 F 1462.7±5.0 0.229+0.003 1454 120 1472 12511 Na 1204.0±2.0 0.37710.001 1190 120 1165 11412 Mg 1067.2+2.0 0.48410.002 1070 1313 Al 864.Oil.0 0.705+0.001 665 1414 Si 756.Oil.0 0.87110.002 767 1215 P 611.2il.0 1.18510.003 635 12 615 1716 S 554.7il.0 1.35210.003 558 12 549 1517 Cl 560.8i2 . 0 1.33310.006 540 120 541.512.019 K 435.Oil.0 1.84910.005 410 120 431.613.020 Ca 332.7il. 5 2.55710.014 343 1321 Sc 316.6i2.5 2.71110.025 ------ 319 1422 Ti 329.3il. 3 2.590+0.012 , 328 1423 V 284.5i2.0 3.069+0.025 274 1524 Cr 255.3i2 . 0 3.47210.031 267 13 251 1325 Mn 232.5i2 . 0 3.85710.037 229 1426 Fe 206.Oil.0 4.41010.024 205.711.327 Co 185.8il.0 4.94010.029 185.211.528 Ni 156.9il.0 5.93210.041 157.211.729 Cu 163.5+1.0 5.67610.037 163.610.830 Zn 159.4il.0 5.83410.039 161.611.032 Ge 166.5il. 0 5.56910.062 167.411.833 As 152.9il.0 6.104+0.043 153.811.4 151.712.034 Se 163.5il.0 5.68110.037 163.011.2 159.012.035 Br 133.3il.0 7.06910.056 129.516.038 Sr 134.Ii2 . 5 7.02210.139 130.112.3 132.712.040 Zr 110.Oil.0 8.66310.083 110.810.841 Nb 92.711.5 1.03610.018 xlO 92.311.142 Mo 99.611.5 0.96110.015 xlO 103.710.747 Ag 87.Oil.5 1.10710.020 xlO 88.510.748 ca 90.711.5 1.06010.018 xlO 90.610.849 In 84.611.5 1.14010.021 xlO 84.810.850 Sn 92.111.5 1.04410.018 xlO 90.111.051 Sb 94.111.7 1.021+0.019 xlO 91.711.1 91.012.052 Te 103.211.0 0.927+0.009 xlO 105.5+1.2 103.712.053 I 83.411.5 1.15810.021 xlO “ 86.110.7 85.312.056 Ba 96.611.5 0.99410.016 xlO 94.410.758 Ce 83.311.0 1.16010.014 xlO 84.410.7 82.012.060 Nd 77.512.0 1.25010.033 xlO 78.510.864 Gd 81.811.5 1.18210.022 xlO 80.111.066 Dy 78.811.1 1.22910.018 xlO68 Er 74.411.5 1.30410.027 xlO ------74 W 78.411.5 1.23710.024 xlO 74.011.179 Au 74.311.5 1.30710.027 xlO 72.610.5 71.012.080 Hg 76.211.5 1.27410.026 xlO 76.211.581 Tl 70.011.5 1.39010.031 xlO 70.610.9 68.012.082 Pb 75.411.0 1.28810.018 xlO 74.610.6 74.012.083 Bi 74.211.0 1.31010.018 xlO 73.310.492 0-238 84.6+1.5 1.14510.021 xlO 81.512.0( **) 78.412.0l),Eckhause et al.Nucl.Phys.81,575(1966)* ,Bardin et al,Phys.Lett.79B,52(1978)**,Hashimoto et al,Phys.Lett.62B,233(1976)18<0.310.300.290.28n N =l26. 1N -20N -50.-ON• 0.27 0.26 0.25N=28V  /** I  4•  * Kr.  > Z -3 6/n=82 • 'J1*5>W.VVXeZ=54RnZ -8 6•  Odd - Z « Even -  Z10 20 30 40 50 60 70 80 90ATOMIC NUMBER ( Z )Fig. IS. The neutron excess vs. atomic number. This excess term is  named the Pauli exclusion term by Primakoff.10 x100Rc £p* Z 'N i(N -3 0 ) .N b(^ 5 2 ) 'UJcc.DC3aoa.xUJaUJa3aUJ<rrP r(N *8 2 )Le ffn*/ArCaV! \fn■ tt/*•tIIIa?\KrZ=36♦XeZ -5 4_JL•  O d d -Z* Even -  Z I I L10 20 30 40  50 60  70 80 90  ATOMIC NUMBER ( Z )Fig. 14. Reduced capture rates vs. atomic number. This graph is  adapted from Kohyama and F u fii ( TRIUMF preprin t TR I-PP-79-41).The large capture rate in 93Nb, an odd-Z nucleus, has been confirmed by our experi­ment. This had been interpreted as the result of an ultra-high magnetic field (1016 G) which might cause a quenching of the Cabibbo angle. However, the odd-proton nuclei, Sc, Ga and Pr, also show large cap­ture rates. Since these nuclei also have neutron numbers close to magic numbers, the capture rates seem to be correlated with nuclear structure. The correlation can be explained by Figs. 13 and 14. In Fig. 13 the neutron excess versus atomic number (Z) is shown. The neutron excess embodies the Pauli exclusion principle in the Primakoff formula. Figure 14 clearly indicates oscil­lations in the experimental reduced capture rates which are correlated with the nuclear shells as shown in Fig. 1 3 . In order to avoid this nuclear structure effect the even-odd effect has been examined between Z=45 and 55 and also between Z=64 and 6 8. Figure 13 suggests that in these regions the structure effect is small. Although the odd-Z nuclei show slightly larger capture rates than the even-Z nuclei, the increase is not as large as that expected from the vanishing of the Cabibbo angle [Suzuki,Ph.D. thesis, UBC (1980)].There have been no theoretical calculations on the effects of nuclear structure on the total muon capture rates. However, an ex­periment by Fricke e t  a t . [SIN Annual Report 1979, page C31] has measured the nuclearcharge radii of the Mo and Sr isotopes and suggests that the nuclear charge radius of 9^Mo is larger than that of 92Mo > which has a magic neutron number. From this result it appears that protons in a nucleus which has a magic neutron number are more tightly bound. However, when the number of neutrons moves away from the magic number, the bind­ing force becomes weaker and the proton radius increases. Since the total capture rate is proportional to (Zgff)4 , a small change in the charge radius can produce a large change in the capture rate.The hyperfine effect in muon capture can be studied by measuring the time distribution of the neutrons emitted after capture. In a test measurement a large hyperfine effect in 19F (Fig. 1 5) was observed. The hf transition rate was measured to be (6 . 7 ±1 .8) x 1 0 6 sec-1, in good agreement with Winston's value, (6.2 ± 1.8) x 106 sec-1.An accurate measurement of the neutron time spectrum is planned for 1981 using two new liquid scintillation detectors (NE213).The muon decay-time spectrum carries not only information about nuclear capture rates but also information about atomic capture ratios (the fraction of the initial muon ensemble orbitally captured onto the different atoms). Our results for atomic capture ratios in various oxides which were reported in the 1979 annual report have now been published [Phys. Lett. 95B, 202 (1980)].19Fig. 15. Byperfine e ffe o t in  the case o f y~ capture in  F.The electron loss inside the target has been studied in 1980 using a Monte Carlo program. Another experimental improvement during 1980 has been the redesign of the veto counter and target holders in order to reduce the carbon background. Further measurements in 1981 will investigate the effects of the dif­ferent oxidation states on the atomic y" capture rates and the hyperfine effects on the nuclear capture rates.E xperim ent 104The tim e p ro je c tio n  cham berDuring the past year the time projection chamber (TPC) system was assembled and tested using cosmic rays, and pions and muons from the M9 beam at TRIUMF. Significant test and background data were obtained, and an initial run was taken to search for y- -* e~ transi­tions. Considerable effort has gone into development of on-line and off-line software, Monte Carlo calculations, magnetic field mapping and shimming, trigger system and electronics development in preparation for the proposed experiment. Work on design of improvements to the TPC for future experiments has also begun.The first intensive tests of the TPC were carried out in April in studies of the decays tt+ -> e+vj y+ -v e+veVy and y" -+ e~veVp. In the first series of measurements a tt+ beam of momentum 70 MeV/c was brought into the Chicago magnet through a telescope of beam scintillators and stopped in a target of balsa wood with dimensions 8.5 cm diam, 20 cm long (balsa was chosen because it has approx­imately the desired density of ~ 0 .2 g/cm3). The target was followed by a 'stop veto' counter constructed with 0.6 cm thick scin­tillator using an air lightguide.The trigger system used for fast detection of the decay electrons following tt+ stops consisted of a set of 6 inner scintillators surrounding the target and a set of 8 large outer scintillators arranged to cover the 6-sector regions of the TPC. The inner scintillators were also used to reject incom­ing particles which scattered out of the target.The discriminator-logic unit used for handling the 144 TPC anode wire array was produced at TRIUMF and commissioned during the year. This system enables the applica­tion of the correct anode wire gating patterns, as determined by the trigger coun­ters, to the anode and cathode ADC systems.It also allows the outer-radial TPC anode wires to be included in the trigger logic. This will be done for the purpose of gaining increased solid angle acceptance by enabling the trigger system to detect particles which travel from the target directly through the end caps.In order to obtain the momentum, three spatial co-ordinates are determined for each of up to 12 track segments detected by the end cap proportional wires (pw). The co­ordinate along the beam axis is determined from the time of drift between the firing of the inner scintillator and detection by the pw which in turn also gives the radial co­ordinate. The position along the pw wire is determined by finding the centroid of the induced charged distribution in the cathode pads which lie above the pw.A generalized off-line analysis program has been developed to read the data from tape, organize it, apply gain corrections for each of the cathode pad amplifiers, apply criteria to select only valid single-track segments and determine the centroid positions. Tests are also applied on the sum of the cathode amplitudes relative to the anode amplitude to determine the validity of the data. The momentum is determined by a helix fit to the accepted track segments. A positron momen­tum spectrum obtained in a short run is shown in Fig. 16. As discussed below, the momentum resolution for electrons is expected to be considerably better.20MOMENTUM ( MeV/c )Fig. 16. The momentum spectrum o f  electrons from the reactions v+ e+\ie and ti+ -*■Experimental studies were made to optimize operating conditions of the TPC with runs at various values of anode high voltage, drift plane voltage, magnetic field and gas flow. Measurements were also made at various rates of stopping tt+ . These data are still being analysed. Preliminary results indicate that the average position resolution for 70 MeV/c positrons was cr ~  700 pm along the anode wi res.Experimental tests with cosmic rays have shown that the position resolution depends critically on the angle at which the track crosses the TPC anode wires. This effect is due to non-uniformities of the electric field in the neighbourhood of the TPC anode wires.It results in the expectation that tracks due to positrons will have position resolution significantly higher than those due to elec­trons. Average position resolutions of a 300 p have been observed in cosmic-ray data with wire crossings at preferred angles equivalent to those expected for 100 MeV/c elect rons.Monte Carlo calculations have been improved to simulate realistic data produced in the TPC. Effects included involve cathode charge distribution, angular dependence, overall acceptance under various operating condi­tions, trigger efficiency, collision losses, bremsstrahlung, multiple scattering, diffu­sion and drift velocity.During the past year extensive mapping and some shimming of the field in the Chicago magnet has continued. The main results indicate that drift displacements due to non­uniformities in the magnetic field should be <100 p over ~38% of the TPC volume. Figure 17shows a contour plot of the maximum dis­placement in the r-<j> plane for tracks drift­ing from the centre plane region.In order to reduce detection of random tracks in the TPC a system has been developed to use the knowledge of the trig­ger track's slope and position to gate the TPC anode wire signals at the time of arrival of the drifting track segments. The electronics for this sequential gate generator (SGG) has been designed and con­structed by a joint NRC-Carleton effort. It will be completed and tested in 1981. It is designed to produce the proper timing gates within about 500 nsec of the passage of the particle.In other developments, a N2 laser has been tested which is capable of producing suit­able ionization tracks in gases for calibra­tion of the TPC. In collaboration with the TRIUMF electronics group, the development of an improved readout scheme for the TPC has begun. The system, which will be con­structed initially to operate on our proto­type TPC, is based on the use of fast ADC's to enable detection of mu 11iparticle events. As of September all components designed for the y e experiment, with the exception of the electronics for the trigger wire chambers, were at TRIUMF.Fig. 17. The deviation o f  the pos ition  measurement in  the r<f> plane due to variations in  the magnetic f ie ld .21E xperim ent 121Test o f charge-sym m etry in  n-p sca tte ringIsotopic spin invariance or charge indepen­dence was the first internal symmetry pos­tulated in elementary particle physics. It states that the neutron and the proton are two degenerate states of the nucleon. Iso­topic spin invariance is broken by the elec­tromagnetic interaction. Charge symmetry is a lesser symmetry because it only involves a rotation in isospin space over 180°. Charge symmetry states that observables are un­affected by changing neutrons into protons and protons into neutrons. Thus, the neu- tron-neutron scattering length and effective range are equal to the proton-proton scat­tering length and effective range after correcting for electromagnetic effects, e.g., the static Coulomb interaction. Similarly, the polarization of the neutron in scattei ing unpolarized neutrons from protons equals the polarization of the recoiling proton.The planned experiment will measure analy­sing powers instead of polarizations by scat­tering polarized, respectively unpolarized, neutrons from an unpolarized, respectively polarized,proton frozen spin target. The neutrons are produced at 9° by a LD2 target bombarded by a polarized, respectively un­polarized, proton beam from the same ion source. The experiment will determine the difference AA in the analysing powers at the cross over angle (~7l° cm at 500 MeV) where the analysing powers change sign. Designed as a null measurement requiring no absolute polarization standards, the experi­ment will measure the difference in cross­over angle to an accuracy of 0.05° giving an accuracy in AA of one part in 103.The past year has seen a great deal of activ­ity in instrumentation design and construc­tion: two large neutron counter arrays, delay line chambers, proton range counters, proton beam polarimeter and energy monitor, proton beam profile and position monitors.In addition, TRIUMF site efforts have been directed towards providing the experiment with a new superconducting solenoid (for proton spin precession) a dipole magnet (for neutron spin precession), and the fro­zen spin target, as well as refurbishing the LD2 target. Testing of the various instru­mentation items has begun and will continue during l98l with assembly of the complete experimental set-up scheduled for early 1 9 8 2.Experim ent 134M easurem ent o f the rj param eter in  m uon decayExperiment 13^, designed to measure the n parameter in the decay of the muon, received beam time in August.The electron spectrum from muon decay was observed with an axial focusing magnetic spectrometer. The momentum resolution is better than 3%. The data obtained are presently being analysed and compared to trajectory calculations. The statistics ob­tained so far are not yet sufficient for an accurate determination of n and the under­standing of the different types of background and contributions from the analysis of the data obtained.22NUCLEAR PHYSICS AND CHEMISTRYE xperim ents 1, 118 Pi sca tte ringThe experimental program has continued to be dedicated to low-energy pion nuclear physics. tt" elastic scattering ratios have been studied for isotopes of magnesium and lithium, and a short run was undertaken to demonstrate the feasibility of using M 13 for good resolu­tion proton coincidence experiments.Figure 18 shows 26’24Mg cross-section ratios. This magnesium data shows the beginning of the influence of the shape diffraction minima changes. As the energy increases or as the nuclear size increases this minimum begins to move into the angular distribution. The determination of rms radii by studies of this minimum has been attempted with resonance energy pions. These higher-energy experi­ments have been largely unsuccessful. To interpret this data completely one must study how the diffraction minima affect radius determi nat ions.0cm (d e9 )Fig. 18. t[~ e la s tic  scattering ra tio  fo r  2(}Mg and zkMg at = 50 MeV.The 6,7Li ratios as shown in Fig. 19 require a rms radius difference that has a larger neutron radius for 7Li than for 6Li. How­ever, the calculation is complicated by the necessity of including the k77 keV first ex­cited states into the calculation.The tt+-11B-12C ratio results give a proton radius difference that has possibly an energy dependence as can be found in Table IV. That is unacceptable. A reason for this may be a dependence that has not been included cor­rectly in the potential. In particular, the absorption terms are very dominant at low energies for ir+ scattering and are just be­ginning to be included in a fundamental way. Absorption has in the past been included as a term depending on Pnucleus wh°se strength was determined by either tt mesic X-ray data or by fitting a set of elastic scattering data. In principle, one should also include an absorption term that includes an isovector (N-Z)/A dependence. An energy dependence may thus appear in -rr+ scattering cross-section ratios from absorption effects that will not appear in it- scattering.Data have been taken on the reactiontt+ + 11+N -* 12C + 2p at T^ = 30 MeV. The dataFig. 19. it- e la s tic  scattering ra tio  fo r 7L i and 6L i at = 50 MeV.23Table IV. ir+ elastic scattering ratio results for l:lB and 12C.a38.6 MeV 47.7 MeVColorado - global 2.401 ± 0.017 2.360 ± 0.010Colorado - best fit 2.360 ± 0.022 2.349 ± 0.010Colorado weighted mean 2 . 3 8 5 2.355Colorado overall 2.370MSU - global 2.391 ± 0.034 2.344 ± 0.016MSU - best fit 2.389 ± 0.026 2.354 ± 0.012MSU weighted mean 2.390 2.350MSU overal1 2.370LT 2.380 ± 0.010 2.350 ± 0.005Combined mean 2.358 ± 0.021< r 2 > i / 2  1 2 C < r 2 > l / 2  n B 0.072  ± 0 . 0 2 1aCharge density rms radii (in fermis) for relative to a 12C rms charge radius of 2.44 fm determined by various optical model calculations. The un­certainties shown were determined in the fitting procedure. The final uncertainty is just the standard deviation of the ten combined values.at the 'deuteron' opening angle as shown in Fig. 20 resemble stopped (Tr- , 2 n )  data and 90 MeV (tt+ ,2p). The interpretation is that when kinematics similar to the absorption on deuterium is used the reaction yield can be determined by the ttD -*■ 2p cross section coupled to the coefficients of fractional parentage. The off-deuteron angle cross sec­tions remain to be studied.The M13 30 MeV pion flux has been increased by a factor of about 3 by using a 1 cm waterpion production target and extracting pions from the p+p ■+ ttD reaction. It is intended to use a 3 cm water target for the experimen­tal running to give a xlO enhancement of 30 MeV 7r+ flux. A side benefit is that the intrinsic resolution of this reaction com­bined with the angular acceptance of the channel gives a beam resolution of about 300 keV for Ml 3- In addition, we have received intrinsic germanium telescopes from a Canadian source so that our solid angle has been increased by its inclusion in the apparatus. The resolution as well may i mprove!RESIDUAL NUCLEUS EXCITATION ENERGY (MeV)Fig. 20. lkN(T\+,2 p )l2C residual nucleus exc ita tion  spectrum.Experim ents 3, 117, 142S tud ies o f fragm ents e m itte d  from  p ro ton  in te rac tionsw ith  com p lex nuc le iThe time-of-f1ight data of the general survey portion of the program (Expt. 3) has been analysed. A rapidity analysis of these Ag(p,fragment) measurements indicates that the data for all fragments of 4 < A < 24 can be fitted by assuming they are emitted iso- tropically from sources moving in the direction of the beam at velocities depending on the fragment and the value selected for the re 1 ativistica11y invariant cross section. However, the values of these emitting source velocities show that a major fraction of the cross section for most fragments cannot be from the decay of an equilibrated 'compound nucleus' near the target mass. The same result is obtained when an evaporation calcu­lation is performed. This calculation24120100erlii800.10.010.0010.10.010.001approximate kinematic limit i i I i100 150 200 250 3 0 0measurements= 17 MeVFig. 21. The (p,2p) measurements on Be. Data and kinematic l im it  calculations are fo r  the case Ep =300 MeV, Qq = -90 ± 2.5°.predicts that almost all {>30%) of the cross section for fragments above carbon is the result of non-evaporative processes.Refinements of initial direct knock-out models of fragment emission [Boal and Woloshyn, Phys. Rev. C 20^ , 1878 (1979)] have led to a 'snowball model1 [Boal e t  a l .  , to be published, Phys. Rev. C] in which the emitted fragment is formed by the coalescence of nuc­leons produced by the subsequent interactions of an initially struck nucleon. Initial agreement is gratifying although isotopic variations have yet to be included in the calculations and tested against the experi­mental results.The high purity Ge detector telescope designed to measure the energy spectra of the light fragments (A < 8) out to their kinemat­ic limits (Expt. 117) was constructed and tested with sources. Unfortunately, the lack of a data acquisition system for the major part of the year, while a new system based on a PDP 11/34 was being assembled, prevented any measurements from being made. It is anticipated that the program will obtain data early in the new year now that the data system is operational.Initial measurements were made on the study of coincidences between a high energy forward- going proton, believed to be the scattered incident proton, and a backward trigger pro­ton or fragment (Expt. 142). PredictionsFig. 22. Preliminary summed energy spectra fo r  the (p,2p) reaction on Be with 300 MeV p. Curves have been drawn through data points which were binned in  5 MeV increments. Typical s ta t is t ic a l e rro r bars from the data used are indicated at various places. No corrections have been included fo r  the response function o f  the detectors which w ill  increase the high end and decrease the low end o f  the spectra by a fa cto r o f  approximately 2.of the snowball model and related calcula­tions suggested an enhancement slightly below the QTBS angle for the (p,2p) reaction on Be. This was at variance with the results of measurements by Franckel e t  a l . at 800 MeV.A Be(p,2p) measurement was made at 300 MeV using the University of Alberta systems at 4BT1 . Telescopes of plastic and Nal detector systems were used to survey a much wider range of angles and energies than in the measurements at 800 MeV. Preliminary analy­sis indicates that the distribution of for­ward protons associated with a large angle trigger proton has a rather large angular and energy plateau(eQTBS _ > + 20 ; Em jn < Ep .£ El im J t) *Superimposed on this continuum is a peak at the upper energy range but with a smaller angular range (0QJBS = » + 10°). The peakdisappears when the backward trigger proton energy is above 95 MeV. Portions of the data and these results are shown in Figs. 21 and 22. These results also indicate that the maximum is shifted above the QTBS angle.This may indicate that multiple scattering is a larger problem than initially anti ci pated.25It is interesting to speculate that the peak in the energy spectra is due to the interac­tion in which there is only one nucleon to carry off the recoil momentum of the emitted proton whereas the continuum is the result of two or more nucleons in the recoil jet. With this in mind, Fig. 21 indicates the kinematic­ally allowable regions for the one-nucleon recoil jet mechanism. Whether the fact that the peak region extends beyond the limit for E" = 17 MeV is significant, or even if the one-nucleon jet explanation is appropriate, is yet to be verified. A more likely expla­nation is that the peak is entirely due to coherent or near coherent recoil after a con­ventional P 3 / 2  proton knockout reaction. The region in which the peak is discernible then corresponds almost exactly to events with recoil momenta < 300 MeV/c.E xperim ent 10Pion p ro d u c tio n  by p ro ton  bom bardm ent o f hydrogenand o the r l ig h t n u c le iAfter the assembly and commissioning work of 1979, 1980 was a year of data-taking with minor improvements made to the detector sys­tem and target chamber. The spectrometer (a 65 cm Browne-Buechner spectrograph re­named the Captain Cook Bicentennial spectrom­eter 'Resolution') for analysing pion- reaction-product momentum uses a simple 3- counter trigger for event definition and 3 helically wound proportional chambers to define the pion trajectory. The spatial resolution of the chambers is better than 1 mm, and the overall energy resolution of the spectrometer should be better than 300 keV. The laboratory angular range of Resolution is from 45° to 135°, and the acceptance is 3 msr.The Geneva wheel target changer has been re­placed with a more precise target ladder which allows six separate target locations to be set remotely. A beam profile monitor has also been installed inside the target chamber. The spatial resolution of the monitor is 1 mm in both the horizontal and vertical directions. Typical beam spots that we have been able to attain are 5 mm and 1.5 mm FWHM in x and y, respectively.A number of minor problems associated with the system were encountered and corrected, namely the amplifiers on the wire chambers needed to be modified, and some broken wires had to be repaired. The chamber system wasfound to be very sensitive to the quality of the cyclotron beam tune, in that a beam halo not even discernible on the wire monitors caused significant changes to the background levels in the experimental area and hence to the leakage current in the wire chambers.This problem was partly resolved by extra shielding and careful attention to fine details of the beam-tuning procedure.The better energy resolution (<500 keV) at certain times in 1979 was not obtainable on a routine basis because of the intrinsic resolution of the cyclotron's extracted beam. Because 10Be has more clearly separated ex­cited states (at a resolution of 1 MeV) than does 13C, it was decided to concentrate our data-taking with a 9Be target.For the 9Be(p,ir+ ) 10Be reaction, complete sets of data of the angular distribution for do/dfi and Ay were taken at incident proton energies of 225 and 250 MeV and sel ected angles at 200 MeV to overlap our previous results. The pion energy spectrum obtained is shown in Fig. 23. A selection of the analysing power data is shown in Fig. 24.The (p,ir+ ) transitions to the g.s. and low levels of excitation are consistent with our data at Tp = 200 MeV [Auld e t  a t . ,  Phys. Rev. Lett, k ] , 462 (1978)] confirming the charac­teristic dip in Ay near 0C-nif = 60°. The transitions to the higher excited states (not measured before) show different characteris­tics, however. The analysing power associ­ated with the 7-5 MeV state shows some energy dependence, whereas that of the 9-5 and and 12.0 MeV states (not shown on Fig. 24) are generally negative throughout the angular range very much like the continuum.For the 9Be(p,ir-) 10C reaction, the first measurements of Ay for the ground state transition were measured at 200 MeV by this experiment and at the IUCF [Sjoreen et at., Phys. Rev. Lett. 45., 1769 (1980)], and for the higher excitation levels of 10C (3.35, 5.28 and 6.6) by this experiment at proton energies of 200, 225 and 250 MeV [Lolos et at., Proc. 5th Int. Conf. on Polarization Phenomena in Nuclear Physics (AIPCP#69, in press)]. A sample of the results is shown in Fig. 25. The transition to the 10C (g.s.) has an analysing power which changes from negative 0|_ < 55° to large positive values for 0|_ > 80° with little variation with pro­ton energy. The values of Ay for transitions to 10C (3-35) and 10C (5.28) also show mini­mal dependence on proton energy; however,269B e(p ,T r+)10Be500.0 550.0 600.0 650.0 700.0PION KINETIC ENERGY (MeV) ( x « ) '1)Fig. 23. Pion k in e tic  energy spectrum fo r  3Be(p,-n+)l0Be at 225 MeV and 6^(la b ) = 65°..4.2 0 , - . 2  - . 4  - .6  -.8 - 1 .0.4.20- . 2- . 4- .6- . 8- 1.0.4.20- .2- .4-.6- . 8.4.20-.2- .4-.6- .8- 1.0Tp=250MeV 6 .0  MeV: A {5Tp-250 MeV 7.5 MeV: |  :: !}fIl jTp-250 MeV- G.S. T1T+X\  i  T I ; i j  t iTp-250 MeV 3.37 MeV5 I: , - 5  :iTp-225 MeV- 6 .0  MeV:Tp-225 MeV|  7.5 MeV -V 1 :Tp-225 MeV. G.S.; ^ : X1 1 1 1 1 1 1 1Tp-225 MeV 3.37 MeV5 5  ^ I -V  :0 20 40 60 80 100 120140160 0 20 40 60 80 100120140160du-(lab) tJ^ -Oab)Fig. 24. tions to 10Be.thevs. e^Clab) fo r  sBe(p,it+) 10Be: Transi- g .s . , 3.37j 6.0 and 7.5 MeV states o fFig. 26. Background reduction o f  the (p ,^ rj spectrometer system, r f  and Cl in  spectrometer telescope; (b ) same data a fte r  dE/dx,BIN NUMBER(a) Timing spectrum between cyclotron  t im e -o f-f lig h t and track d e fin itio n  cuts.2728Fig. 25. Av vs. B^Ciab) for 9Be (p, t\~ )1 °C: transitions to the g.s., 3.35, 5.25 and 6.6 MeV states ofthe 10C (6.6) state shows a large variation with incident proton energy.Our ability to reject non-pionic background events in the spectrometer system is shown in Fig. 26. Figure 26(a) shows a timing spec­trum between the cyclotron RF signal and counter in the spectrometer telescope.Figure 26(b) shows the same sample of data after dE/dx; time-of-f1ight and track defini­tion cuts are applied. The total background not associated with pions varied from <2 pb/MeV-sr at 200 MeV to <15 pb/MeV-sr at 250 MeV incident proton energy.A full summary of all the data for (p .tt1) analysing powers is being published in the proceedings of the 5th International Conference on Polarization Phenomena in Nuc­lear Physics [Auld, AIPCP#69, in press).Plans for 1981 include the completion of the 12C (p ,it) reaction at 225 and 250 MeV and the study of the 10B and le0 (p,ir) reaction.Experim ents 80, 127 P ion ic  X-rays in  lig h t targetsData-taking for graduate theses associated with this ongoing survey of pionic X-rays in light atoms was completed in 1980. Data reduction is in progress on the most recent measurements, and several papers are in preparation. The pionic (and muonic) 10»i:lB results on 2p-ls transitions have been accepted for publication in Nuclear Physics, and the pionic 12>13C results will be sub­mitted shortly. The latter measurement provided data for the Master's thesis of Alan Fry. Analysis of the pionic 16>180 data is nearly complete, as is Chris Sayre's Master's thesis which describes the oxygen measurements in detail. Analysis of pionic Ne data, which had sufficient resolution and statistical accuracy to permit extraction of shifts and widths for both 20Ne and 22Ne, is complete and a paper is in preparation.Results of recent pionic X-ray 2p-ls measure­ments are given in Table V .In December a 30 mg sample of 35S, obtained on short-term loan, was placed in a He- filled vessel designed to provide stopping signals for low density gas measurements, and the 3d-2p pionic transition was success­fully observed. 2p level shifts and widths are being extracted and will be published shortly.The high pressure (<10 atm) gas target to be used in measurements of the shift in pionic deuterium and hydrogen K X-rays was con­structed and tested along with backed beryl­lium windows capable of operation at maximum target pressure. Preliminary runs with He gas confirmed the assumed stop rate on the M9 channel. The Si(Li) triplet was success­fully operated at beam currents of 100 yA.Table V .  Results of recent pionic X-ray 2p-ls measurements.Spec i es Energy(keV)Wi dth (keV)10b 65.901 (13) 1.776 (30)n B 65.120 (26) 1.719 (80)12c 93.287 (AA) 2.66 (12)13C 92.227 (27) 2.59 (11)20Ne 239.30 (17) 15.60 (A9)22Ne 231.61 (95) 12.A (3-1)E xperim ent 83Bound m uon decay in nuc le iThis experiment seeks to measure the energy spectrum and energy dependence of the asym­metry of decay electrons following y” decay from bound atomic orbits. In the spring of l979 a time-differential analysis method using the MSR technique was employed for C,T i , Cu and Pb targets and the preliminary results were reported in the 1979 TRIUMF Annual Report. The data are in excellent agreement with Huff's calculations except for the low-energy region below «15 MeV where a significant background, having the target y~ lifetime component, cannot be eliminated. Future measurements with a separated y- beam should improve the low-energy data.During 1980 this experiment did not receive any beam time. Instead the group has worked on the calculation of the radiative correc­tions to the e+ spectrum for free y+ decay which is specific to the experimental geom­etry and method (Nal = y and e+ detector). During measurements of the decay spectra the y+ decay spectrum and asymmetry were also measured as a check of the experimental tech­nique. These data were analysed for the Michel parameters p and 6 which were deter­mined quite accurately due to the high sta­tistical accuracy. However, the radiative29corrections which were employed in the anal­ysis assumed that most of the emitted photons would be detected. Since a Nal detector (with 100% efficiency for both e+ and y's) was used in this experiment, it is not pos­sible to use the standard radiative correc­tion formulae and the radiative corrections must be calculated using Monte Carlo techn i ques.The shapes of the energy spectra with or without photons detected have been discussed by D. Berghofer (Ph.D. thesis, UBC, 1979). According to his analysis, the p parameter in the Michel spectrum was determined to be 0 . 7 2 for the positron spectrum with no photons detected.effect is negligible. On the other hand, in the high-energy region, the correction is large for latter geometry.Since the theoretical expression for the dif­ferential asymmetry has a denominator which is the Michel energy spectrum, it is possible that these radiative corrections might pro­duce a large effect in the low-energy region of the asymmetry spectrum (where we have been unable to fit our data). The calculation of the radiative correction formulae for the asymmetry term itself is presently being undertaken by J. Ng at TRIUMF. His expres­sions will be included in our Monte Carlo program to produce the theoretical asymmetry spectrum.Figure 27 shows how the original Michel spectrum changes in shape due to the energy loss in the target, the electron telescope counters and the Nal entrance window. The average energy loss is about 6 MeV for our geometry. In Fig. 28, the amplitude of the radiative corrections to the zero'th order Michel spectrum as a function of the summed energy of the detected positrons and photons is shown for two different solid angles for the photon detection. In the low-energy region the radiative correction is signifi­cant for the case of our geometry with a limited photon acceptance; however, for a geometry with a large photon acceptance thex10-2aLU2* 30 <ZtroW 20 (- zin >  uiu.Oa. 10 tu m  Z  => zOBSERVED /i OR.SFRVFD - V «_ MONTE CARLO RESULTS _?A I AFTER ENERGY LOSS•  N O  P H O TO N  _0 ALL PH O TO N S  BSERVE  A O UR G EO M ETRY /*  /* /• //• /♦ //• /- ♦ * /♦  /  THEORETICAL♦  /  SPECTRUM. *  /  BEFORE ENERGYA •o♦LOSS/-L^ I_____0 10 20 30 40 50OBSERVED ENERGY ( MeV )E xperim ent 86 Proton e la s tic  sca tte ringExperiment 86, which is studying proton el­astic scattering from calcium and 208Pb nuclei, received ll shifts of polarized beam in 1980. Cross section and analysing power data were obtained at 300 MeV using the medium resolution spectrometer (MRS) in the small angle mode, and a few points in the 200 and 400 MeV angular distributions repeated.These data and ones collected previously were all reduced to final results in off­line replay of data tapes, leaving acquisi­tion and replay of large-angle 300 MeV data as the sole remaining part of the experi­ment.10oGC Ui Q. 01RADIATIVE CORRECTIONS TO THE ZEROTH ORDER MICHEL SHAPEO ALL P H O T O N S  OBSERVED A O U R  G EO M E TR YAAA AvO-nQi-10O o A_L10 20 30 40ENERGY ( MeV )50Fig. 27. The e ffe cts  o f  energy loss and photon detection.Fig. 28. Radiative corrections fo r  d iffe re n t geometries o f  photon detection.30Fig. 29. Comparison o f  second-order KMT predictions  with data fo r  p + 208Pb e la s tic  scattering at 400 MeV. The broken lines are obtained using the theore tica l neutron matter d is tribu tion  o f  Negele (5.65 fm rms rad ius); the so lid  lines are fo r  an adjusted three- parameter Gaussian d is tribu tion  (5.42 fm rms radius).The 400 MeV 208Pb data have been compared with the predictions of a second-order KMT multiple scattering calculation. The results shown in Fig. 29 were obtained using the same neutron matter distribution that best fitted the 800 MeV LAMPF data. Reproduction of the data by the KMT model is not as satisfactory as at 800 and 1000 MeV; some improvement in prediction of analysing powers is seen if the real central part of the optical poten­tial is made less attractive than at the nuclear surface. Hartree-Fock calculations, starting from the Dirac equation for the proton, predict optical potentials for which the real central part is attractive at the surface and less attractive or even repulsive in the nuclear interior. Such Dirac- Hartree calculations have been done for cal­cium, and are in good agreement with the experimental results.E xperim ent 89capture in fis s ile  nuc lidesResults on measurements of the absolute fission yields following y~ capture, prompt- to-delayed yield ratios, and y - fission life­times in 2 35U and 238U have already been published [Ahmad e t  a l . ,  Phys. Lett. 92B, 83(1980)]. Absolute yields were obtained by stopping muons in efficiency-calibrated fis­sion chambers and by tagging true muon stoppings in the target material through the detection of the muonic K and L X-rays in coincidence with the stop.A further run was undertaken in March 1980 to investigate the possible 18 nsec short component in the time distribution of y"238U that was observed in our 1978 run and to determine precisely the specific atomic transitions responsible for prompt fissions. To this end a new 238U fission chamber with design identical to our 235U chamber was constructed and an improved preamplifier was used. Three large 5 in. x 6 in. Nal (Tl) detectors were used to detect the muonic X-rays. The 238U chamber was later cali­brated at the Chalk River Nuclear Laboratory. From our 1980 run, the absolute fission yields obtained following y - capture using the Ka coincidence technique are consistent with the published values. Prompt-to-delayed yield ratios and lifetimes are also consis­tent, with the exception that there is no evidence of the 18 nsec component in the y” 238U new data. Our present results are given in Table V I .The time correlation between muon-induced fission and muonic X-rays has been measured.It is observed that prompt fissions are all missing when fissions are correlated with K X-rays. Results of X-ray coincidence measurements indicate that in 235U about (1.04 ± 0.31)% prompt fissions per y" stop originate due to 2p-ls (El) dipole nonradia- tive transitions, whereas (0.70 ± 0 .2 7 ) 1 are due to 3p- ls (El)dipole nonradiative and 3d-1s (E2) quadrupole nonradiative transi­tions. For 238U, (O .38 ± 0.09)% prompts per y" stop are due to 2p-ls (El) and (0.26 ± 0.08)% to 3p- ls (El) and 3d-ls (E2) nonradi­ative transitions. These data will form part of S. Ahmad's Ph.D. thesis.E xperim ents 99, 144S tud ies o f (p,d) reac tions  in  nuc le iExperiment 99 and its successor (Expt. 144) are continuing the study of (p,d) reactions in the nuclei ^He, 12C, 13C, 150 and 1+0Ca.The final cross section and analysing power angular distributions for 13C(p,d)12C at 200 and 400 MeV, along with DWBA calculations made at the University of Colorado, have been submitted for publication. The analysing31Table VI. Results of fission yields and lifetimes of 235U and 238UMeasurements 2 33U 2 3 8 (jMean 1i fet i me (ns)Prompt £. . . . .n r •; fission yield Delayed 'Delayed fission yield per y~ stop ( Prompt fission yield per y“ stop (3 Absolute fission yield per p” stop Prompt fission " K X-ray , 0 s Prompt fissionPrompt fission " L X-ray ,0*Prompt fission 0Prompt fission * 2-1NR per y" stop [2p— 1s (El)]Prompt fission *  3-1NR per \i~ stop [3d-1 s (E2)"|L3p-ls (El)J71 .6 + 0.6 77-2 + 0.40.133 + 0.006 0.093 + 0.00513.1 + 2.6 6.9 + 1 .01 .7^ + 0.36 0.64 + 0.1014.8 + 2.6 7.5 + 1 .00 + ] k 9 + 960 + 13 60 + 101 .0 k + 0.31 0 . 3 8 + 0.090.70 + 0.27 0.26 + 0.08NR - non-radiative.power data are oscillatory and show a j-dependence for the orbital of the picked-up neutron.Replay of the 200 MeV 160(p,d) data taken in 1979 is complete. Figure 30 shows the differential cross section and analysing power angular distributions for the ground state and first excited state group at about 6.2 MeV. As in the case of 13C(p,d), the analysing power data show much more structure than the differential cross sections and are apparently more sensitive to spin-dependent components of the interaction. As a by-product of the background subtraction from the water tar­get, 12C(p,d) data of moderate statisti­cal accuracy were also obtained.Eight shifts of 4He(p,d)3He data were taken at 200 and 400 MeV from June 5_9; replay of the data tapes is now complete. One shift of unpolarized beam time in July was used to measure 4He(p,3He)d and ltHe(p,1+He)p at 400 and 500 MeV in order to extend the (p,d) data back in scatter­ing angle and to provide normalization checks to existing p-4He elastic scatter­ing data. Theoretical work is under way at the University of Colorado to fit the ^He and 150 data sets.Fig. SO. D iffe re n tia l cross section_and analysing power angular d is tribu tions fo r  le0 (p ,d )l50 at 200 MeV fo r  the ground and f i r s t  excited  states.0.30.1- 0.1-0.3-0.5(deg)+t +(deg)0.50.30.1- 0 . 1-0.3++++A * ’32Experim ent 103 Spin-sp in  in te rac tionThe differential cross section, analysing powej^ and depolarization parameter D in 9Be(p,p0)9Be elastic scattering were measur­ed at 225 MeV. Simultaneously cross section and analysing power data were obtained in 9Be(p,p2)9Be (2.429 MeV) scattering to the first excited state. The data were analysed using the optical model and the Dirac- Hartree model, and an estimate was obtained for the strength of the spin-spin tensor term in the former.The cross section and analysing power mea­surements were performed using the TRIUMF polarized proton beam and the medium resolu­tion spectrometer (MRS). The depolarization parameter D was obtained by measuring the polarization of the outgoing protons, through the relationship Pout = (P + DP i n )/(1 + APjn) when P;n = beam polarization.P(polarization) = A(analysing power) in the 9Be(p,p0) reaction. The outgoing proton polarization was measured with a polarimeter mounted at the focal plane of the MRS. This focal plane polarimeter consisted of a nar­row carbon second scatterer which only "saw" the elastically scattered protons, and two scintillators to detect the double scattered protons. This polarimeter was calibratedFig. 31. 9Be(p,pQ) elastic; scattering cross section.using the 12C(p,p)12C reaction. The mea­sured analysing power was +0.54, and the efficiency was 1/2%. The experimental re­sults are shown in Figs. 31 through 35.Deviation of D from unity in elastic scat­tering requires a mechanism to flip the spin of the protons. Such mechanisms are: compound nuclear effects, quadrupole spin- flip effects, and spin-spin interactions in the optical potentials. At intermediate bombarding energies, compound nuclear effects should be very small, so these are ignored. Quadrupole spin-flip effects can be estimated by using the rotational model for the 9Be ground (3”/2) and the strongly excited (5~/2) state at 2.429 MeV. With DWBA, we obtain:D(quadrupole spin-flip) =1 _ Z  g i nelastic _9 CTelastic inelasticwhere Sjne]astjc (quadrupole) = quadrupole spin-flip probability.Using the experimental values for O j n e ] a s t ; c  and CTelastic’ we obtain values for D shown in Fig. 35. These values deviate from unity by less than 2%, and hence the quadrupole spin-flip contribution can also be ignored. Therefore, we are left with only a spin- spin term in the optical potential as a viable spin-flip mechanism in this reaction.The elastic and inelastic scattering cross sections and analysing powers were fittedFig. 32. ^Be(p,p2) cross section.33Fig. 33. 9Be(p,p0) analysing power.with the optical model and the Dirac-Hartree model. The theoretical curves are shown along with the data in Fig. 31. Calculations for D were performed by adding a tensor spin- spin term in the optical model of the form:Uss = - J  Vst Ft (r) t3(a*r) (l_-r)-l] .These calculations for Vst = 1.6 MeV are shown in Fig. 35. We obtain a good fit toFig. 34. 9B e (p ,p a n a ly s in g  power.the data, and thus we have demonstrated the need for a spin-spin term in the optical potent i a 1.E xperim ent 113 E las tic  sca tte ring  o f p ro to n s  from  3HeStudies of the elastic scattering of protons from the very light nuclei have as main ob­ject i ves:1) to provide a sensitive testing ground for multiple scattering theories used in analy­ses of proton-nucleus scattering,2) to determine the sufficiency of the nucleon-nucleon scattering amplitudes, as extracted from nucleon-nucleon elastic scat­tering data, in analyses of proton-nucleus scattering using multiple scattering theories, and3) to study specific nuclear structure and nuclear reaction mechanism information, e.g. the admixture of small components to the ground state wave function, the formation of intermediate A's.With this aim, a program of measuring the 3He(p,p)3He differential cross section and analysing power angular distributions from extreme forward to extreme backward angles at four energies between 200 MeV and 5 l5 MeV has begun. The experiment uses the Uni­versity of Manitoba liquid 3He cryostat3420"  40"  60"  80"  100"  120"  140"  160"  180"ecm (degrees)Fig. 36. (a ) Analysing power in  p3He e la s tic  scattering at 515 MeV; (b ) the e la s tic  d iffe re n tia lcross section.placed at the scattering chamber of the medium resolution spectrometer. Target thicknesses of up to 120 mg cm-2 are being used. Both scattered protons and recoiling 3He particles are observed by the spectrom­eter. Preliminary differential cross sections and analysing powers are shown in Fig. 36.Experim ent 114S tudy o f tw o-nucleon co rre la tions  in 3HeIn a (p,2p) experiment there is sufficient kinematic information t<j determine separate­ly the vector momentum P (recoil) and total energy E (recoil) of the recoiling system (assuming that the incident proton interacted with only one nucleon). If the kinematics are chosen so that P (recoil) = 0 and if the recoiling system consists of only two nuc­leons, e.g. as in 3He(p,2p)pn, then E (recoil) can be used to calculate the relative momen­tum of the two nucleons in their own centre- of-mass system. The Fourier transform of this distribution is the two-particle wave function. A comparison of this wave function with the single particle wave function yields the two-particle correlation function.With this objective a study has been made of the 3He(p,2p)pn reaction with coplanar sym­metric and asymmetric geometries. Data were obtained at 250 MeV at the angle pairs30°-30°, 35°-35°, 38°-38° and bO°-bO° , and at bOO MeV at the angle pairs 30°-30°, 3^°- 3 b ° , 37°-37°, bO°-bO°, and 37°~b5° ,  3b°-b2° , 30°-38° and b 0 ° - b 7 ° ■ The range of momenta of the recoiling proton-neutron system is from zero to 600 MeV/c. Data reduction is in progress.E xperim ent 115 N eutra l p ion  p ro d u c tio nThe aim of this experiment was to measure the total reaction (angle-integrated) cross section for the production of 210Po from 209Bi over an incident proton energy range from 62 to A80 MeV. Direct production of this nuclide comes from a combination of (p,y) and ( p , tt° )  processes over this range. Experimental details are presented in previous annual reports (1978, 1979)- Figure 37 displays the observed yield of 2l0Po, measured to an error of about ±15%- The onset of the (p,ir°) process is clearly observable above the threshold energy (130 MeV) for this process. Extrapolation and subtraction of the (p,y) contribution above threshold can provide an estimate of the total (p ,tt°) cross section, populating bound states of 210Po.35II (.?,▼*) Tv*ecSwov-P1 _______ I I  I________I_______ I________I___100 200 300 400 500Proton Energy (MeV)Fig. 37. Total reaction cross section fo r  the pro­duction o f 210Po from 209Bi via the (p ,y ) and (p,-n° channeIs.E xperim ent 124 G iant resonancesExperiment 124 had two runs in 1980— one in May and one in October. Angular distribu­tions were obtained for 80Ni (4-20°), 208Pb (6-20°) and 238U(6-l6°). Two short periods, with a dedicated machine, were used for special purposes.In May, George Mackenzie and the operations group were able to deliver a beam current of H O 3"1* protons per second down beam line 4B. This enabled the MRS to be run at 0° and directly observe the raw beam. A possible source of data contamination was found by do i ng this.In another short dedicated run we were able to improve the resolution of the MRS from the usual ~1 MeV to ~500 keV, again with the aid of George Mackenzie and operations.With this resolution it was possible to finally obtain necessary angular distribu­tions on several low-lying excited states in 60Ni and 208Pb.E xperim ent 131 2H(p,y)3He and 3H(p^y)4HeThe principal interest in these reactions is the study of high-momentum-transfer reaction in simple nuclear systems. It is hoped that the absence of problems with rescattering in the final state will make it easier to examine the basic reaction mechanisms than i the analogous pion production reactions. Anunderstanding of the mechanism of proton capture reactions at intermediate energies could in turn make it possible to use these reactions to study the high-momentum com­ponents of nuclear wave functions.The experimental technique is to detect the photon in a lead glass Cerenkov detector in coincidence with the recoil nucleus in a detector consisting of a multiwire propor­tional chamber to measure angles, a thin plastic scintillator and a thicker (plastic or Nal) detector to stop the particle. This system allows complete separation of the (p,y) events from the more numerous (p,ir°) events, as shown in Fig. 38\We have completed measurements of 2H(p,y)3He and have obtained angular distributions of cross section and analysing power for centre-of-mass angles from 30° to 140° at 200, 350 and 500 MeV. In addition a short run was made at 450 MeV to measure the cross section and analysing power at 60°,75° and 90° and cross sections were measured at 60° to 105° at 300 and 400 MeV.Figure 39 summarizes our results at 200 MeV and compares with another recent result at 200 MeV. The agreement with the results of a quasi-deuteron model is excellent.Figure 40 compares the results of many groups which have studied this reaction and its time inverse 3He(y,p)2H. While all results agree approximately on the decreaseFig. 38. A p lo t o f  number o f  counts against re c o il  angle and energy fo r 3He p a rtic les  showing the clean separation o f  (p ,y ) events (A) from (p ,v ° ) events (B).360 * 3 0 '  6 0 * 9 0 * 120*  1 5 0 * 180*6y  (c.m.)Fig. 39. A summary o f  the data from th is  experi­ment a t 200 MeV and a comparison with the data o f  Frascaria e t at. The so lid  line  shows the pre­d ic tion  o f  the quasi-deuteron model o f  Prats.in cross section as bombarding energy is in­creased, the photodisintegration results above 200 MeV equivalent proton energy are about a factor 1.5 below the proton capture cross sections. While Fig. 40 demonstrates some errors in normalization, these cross sections have recently been interpreted as a possible indication of the failure of time-reversal invariance.In 1981 we plan to measure the 3H(p,y)‘+He reaction using tritiated titanium foils as targets and the same detection system.Experim ent 143P ro ton-induced reactions on 9BeExperiment 143 involves simple measurements of the energy and angular distribution for the particle-stable nuclei emitted when a thin beryllium target is bombarded by pro­tons at energies in the range from 200 to 500 MeV. The objectives of the experiment and details of the measurements made are summarized in the 1979 Annual Report.Replacement of the original data acquisition system used by the SFU group was completed in December with the installation of a 'site-standard' PDP 11/34 computer. Despite20010050toJOcc?b a■o |t > 2010B y /  pd, 0p / y  3He =  60°1y  He3 — pd $ Argan et al. f  O’Fallon et al. J Hegerath et al. pd —*- He3 y  J Heusch et al.^ Nefkens et al. §  PresentI I_L _L _l_ _L200100502010I I1----- 1----- 1----- 1—0 ,,/p d , 0p / y 3He = 9 0 °y  He3 —*• pdf  Argan et al.|  O’Fallon et al.J  Hegerath et al.pd — He3 yJ Heusch et al.^  Nefkens et al.5  PresentPI—L100 200 300 400 500 600 700 100 200 300 400 500 60 0  700Ep in MeVFig. 40. A comparison o f  the resu lts o f  many groups at 60° and 90° centre-of-mass angle, using both the proton capture and photodisintegration reactions.37the progressive and ultimately complete failure of the original PDP 15 some limited data were obtained in 1980. Completion of the data acquisition for this experiment is anticipated within the coming year.Measurements were made of the elastic scat­tering of protons from 9Be with large momentum transfer (0.6 < q < 1.1 GeV/c) at incident energies of 225, 329 and k33 MeV. The data at 225 MeV and the lowest values of momentum transfer will overlap with that of Expt. 103 using MRS. The primary purpose of these data is to form the basis of a detailed comparison of the dependence on incident energy and momentum transfer of the (p,p0), ( p , tt) ,  (p,Nir) and (p,2p) reactions. They are also valuable for comparison with recent measurements at IUCF on 12C and 13C illustrating the importance of measurements at high momentum transfer [Meyer e t  a t . ,  Phys. Rev. C 23, 616 (19Sl)] .With protons incident at 329 MeV, angular distributions have been measured in the range 10° £ 0 £ 100° for recoiling 3He, ^He, 6He, 6L i, 7L i , 8Li, 9Li, 7Be, 9Be and 10Be with energies in the interval 21 < E <25 MeV. The results for 9Be and 8U  suggest the importance of sequential processes in reactions resulting in mu 11ipartic1e final states.E xperim ent 152M easurem ent o f the sp in  ro ta tion  param eter Rin p -  4He e la s tic  sca tte ringThe measurement of the spin rotation para­meter R in p-9He scattering will complete our elastic scattering studies of this sys­tem by providing an experimental determina­tion of another independent observable. The need for this independent observable becomes clear if one wishes to provide further tests of the validity of assumptions in either a multiple scattering theory or a potential model theory of proton-nucleus scattering.We are already aware of three potential model theoretical calculations which predict rather different behaviour for the Q. para­meter, even though they each fit da(0)/dfi and A y (0) with about the same degree of success.Using the MRS with its focal plane polari­meter would appear to be an attractive way to measure R until one examines the dramatic kinematic effects for scattering protonsfrom a nucleus as light as helium-A into a reasonable solid angle. With an acceptance of « 3 5  msr at A0° in the lab, kinematic broadening alone would spread the elastic scattering peak to about 12 MeV FWHM. In­cluding the effects of the large size of the helium target cell and differential energy loss in the cell, calculations showed that the elastic peak could be expected to be as broad as 16 MeV FWHM at the focal plane polarimeter target. Without any cor­rection, this situation would mak.e the MRS unusable, since (1) the inelastic events from break-up processes would not be adequa­tely separated and (2) the size of the focal plane polarimeter target would have to be made unacceptably large.A test run has been performed with unpolar­ized beam which showed that kinematic broad­ening could be partially corrected for by introducing a CH2 wedge shaped degrader just in front of the wire chamber which defines the MRS acceptance. The pitch or slope of the wedge was adjusted to compensate for the kinematic spread of the scattered protons from the target. The results indicate that the MRS can accommodate a double scattering measurement from a light nucleus with the use of such a wedge.Polarized beam to measure R is scheduled for the spri ng of 1981.E xperim ent 155 Q uasi-e lastic  sca tte ringThis experiment is investigating deep hole states (in particular the lp states) in tf0Ca by means of the reaction Lt0Ca(p,2p) 39K.The measurement of j-dependent analysing powers should help in distinguishing between P 3/2 and P 1/2 states. The experiment was set up in the spring of 1980 using the MRS to detect one of the outgoing protons and an array of six Nal scintillation detectors to detect the other proton. Five shifts of unpolarized beam were used to tune up the apparatus and twelve shifts of polarized beam were used for taking data. During the run the resolution in separation energy of the knocked-out proton was observed to bel.3 to l.5 MeV. It may be possible to improve this slightly during the off-line analysis, which is now proceeding. A pre­liminary compaction and sorting of the data has been completed. The characteristics of the MRS have been extensively investigated38using the large amount of p,p elastic scat­tering data and d(p,2p)n data acquired for calibration purposes during the experiment. The final stage of the analysis has now begun and should be complete by the summer of 1981 .E xperim ent 158A com parative s tudy  o f the reactions 2H(p,dn + )n and 3He(p,tn + )pThe reaction 2H(p,dtT+ )nIn the study of 2H(p,dir+ )n we have measured the deuteron momentum and angles 6d ,iJ;d with the MRS, as well as the pion angles with an array of fourteen 2-counter tele­scopes. Figure 4l is a schematic of the ex­periment. The deuteron and the pion were identified by TOF-dE/dx. Hence the final state is completely determined if one assumes the unobserved particle to be a neutron; the assumption is entirely warranted at 500 MeV, as two-pion production is negligible. For each event then, we calculate the following quant i t i e s :Pit ’ Pn - |P”Pd~PTrl> ®n> ^n> ^dir’ ^mr anc  ^ *-pirwhere p, pd and p^ are the beam, deuteron and pion momenta, MdlT, Mn are the invariant masses of the dir and nTr systems in the final state, and tp7r is the invariant, four- momentum transfer squared between the beam proton and the pion.The cross section for the reaction is a differential of order 5 in the five variables defining the final state______________d5g______________ _____ d2od(sined)di|jd d C s i n e J d ^  dpd = d2fid d2n7Tdpd 'However, as we expect that the impulse approximation is good at least in the small neutron recoil region, these variables are not the interesting ones. The impulse ap­proximation (iA) gives for the d5a cross section an expression of the formd5o / ' |2/dq\CMdfid dpd = Pn \dfi/pp+d7ywhere the pp -* dw cross section is to betaken at the collision energy s = Mdir andmomentum transfer tp1T. Recently, Stetz has developed a formalism that greatly simpli­fies the data analysis of such an experiment as the present one. He suggested that the proper variables to use were the relativis- tic invariants sd7T = Mdir, tp7r = ( p - p j 2 where the p's are four-vectors and u = (md“Pn)2 = mn + md “ 2Enmd - crosssection written in terms of these variables has the formd5a Mdw p£M—  ~  7) 7-y -y  r  xdsd7T dtpiT dn d<(> d^ 6irmd -p|p-pd |x (% f) M2 (u)\dt/p p-J-d ttwhere M2 (u) is the nuclear vertex function, here for the virtual disintegration d->-p+n, which is proportional to |^(pn) |2 , and 6 and14 telescopes betw. 24 and 96 -pion counters -each counter 4H'x41-3 with veto Va" thick2H(p,dir+)n 506 MeV expt. 158210 mgcrrf2 CD2 or 195mgcm-2 Cend b e a m IVfe v a cu u m p ip e2.5mgcm'2 polyethylene MRS entrance scintill. 2 MWPC (small angle configuration)Fig. 41. Arrangement fo r  2H(p,d-n+)n measurements.39neutron recoil momentum (MeV/c)10r  6nI=5 sCM10“710,-84 THIS EXPERIMENT 2H(p,d1r)n + 2H(e,e'p)500MeV (Sacley) o 2H(p,2p)600MeV (SREL)+ +V.\v50 100 150neutron recoil momentum (M eV/c)F i g .  4 2 .  E x p e r i m e n t a l  v a l u e s  o f  M 2 a s  a  f u n c t i o n  o f  n e u t r o n  F i g .  4 2 .  N u c l e a r  m o m e n tu m  d i s t r i b u t i o n  d e d u c e d  f r o mr e c o i l  m o m e n tu m . t h i s  e x p e r i m e n t  c o m p a r e d  t o  p r e v i o u s  e x p e r i m e n t s .\p a re  angles which can be expressed in terms of ipd and ipu. Should the IA be entirely sufficient for the kinematic domain in which the reaction is being studied, M2 would de­pend exclusively upon u, and not tp^,Mn7r or 6n . Based on a previous study of this reaction by Lo e t  a l . at 800 MeV, it would be expected to find deviations from the IA already at the low value of the neutron recoil pn > 200 MeV/c.Preliminary results for this experiment for neutron recoil momenta pn < l50 MeV/c are in accordance with the predictions of the IA.As an example, Fig. A2 shows the dependence of M2 on pn for a variety of settings of the spectrometer angle and magnetic field. All the data seem to follow a common curve.When these data are used to extract <f>2 (pn), the deuteron momentum distribution, the results are shown in Fig. A3, which also shows the same momentum distribution as ex­tracted from (e,e'p) and (p,2p) measurements. All measurements are seen to be consistent, except perhaps at the highest values of pn .The reaction 3He(p,tir+ )pIn this case a strong final state interaction is expected in the pir+-system, which has iso­spin I = 3/2, and therefore is boosted by the (3,3) resonance. We started with 2H(p,dir+)n because in this case the IA graph is mani­festly dominant, and because final state interactions in the nir+-system must be very weak, as the isospin is I = 1/2, and thus does not allow any role for the (3,3) reso­nance. In the 3He-case, it is not obvious that the IA approximation graph will be dominant, as the pion is supposed to be pro­duced in the interaction of the incoming proton with a quasi-deuteron, or the bound np-part of 3He. Since the initial proposal was written, the group became aware of the results of a study by Tatischeff e t  a l . of the inclusive reaction 3He(5,t)X for forward t's and 850 MeV protons. The missing mass spectra obtained in this experiment show a well developed peak at Mx = 1.23 GeV, the mass of the a(3,3) resonance; this result has been interpreted as evidence for X = A+ + ; with the impulse approximation then this would be a A spectator which may have pre­existed in 3He. However, a study of the kinematics of this reaction shows that simultaneously with Mx = M/\, the recoil pro­ton can have zero recoil momentum in the lab; an impulse approximation calculation of the expected cross section for this process is 30% smaller than the measured cross sections,AOand the recoil spectrum corresponding to the data has a shape compatible with the single particle momentum density of 3He. The Tatischeff e t  a l .  experiment thus confirms our expectation that the impulse approximation dominates the 3-body pion production on 3He.The kinematical region to be studied inExpt. 158 with 3He target will provide exclu­sive cross sections at recoils between zero and 200 MeV/c and for a number of recoils within this interval with an invariant mass of the p—tt system in the range 1.12 to 1.28 GeV. These data will then allow a detailed study of the final state interaction in the p-ir system over the (3,3) resonance.RESEARCH IN CHEMISTRY AND SOLID-STATE PHYSICSE xperim ents 71, 78, 138, 149, 154 I*SR in so lid sMuoni um in solids (Experiments 138, 154)Crystalline quartz (Expt. 154). In the 1979 annual report we described our evidence for a very weakly perturbed vacuum-like spin Hamiltonian for p+e- atoms in a-quartz crys­tals, whose effective hyperfine coupling was found to be slightly anisotropic due to an electrostatic interaction between the Mu electron and the lattice, transmitted to the muon via the magnetic dipole-dipole coupling between the muon and electron spins. The effective spin Hamiltonian can be written%  = geyb?-f - gyyyI*B + ?*A-I (l)where yg is the Bohr magneton, yy ^s the muon magneton, S i s  the electron spin, I is the muon spin, B is the magnetic field, and A is a matrix hyperfine coupling.The early data were taken with a weak ap­plied magnetic field; from these results it was predicted that a 'pure quadrupolar oscil­lation' should be apparent in longitudinal muonium spin relaxation experiments at zero magnetic field (zf-MSR). This has been seen.At 5-6 K three frequencies were observed:1.7 ± 0.1, 6.2 ± 0.1 and 7-9 ± 0.1 MHz. The observed frequencies do not depend on temp­erature from 5-80 K. We conclude that the spin Hamiltonian (l) cannot have A symmetric or even uniaxial. Instead, a completely ani­sotropic spin Hamiltonian is necessary. In zero external field this Hamiltonian has the form^  = A llSx Ix + A 2 2 Sy Iy + A 33SZ IZ ^where Ajj, A2 2 and A 33 are the three princi­pal values of a 3 x 3 matrix describing the hyperfine coupling and defining the x, y and z d i rect ions.From a set of orientations and the amplitudes of the observed frequencies it is possible to determine the angles of the principal axes of the matrix with respect to external crystal axes. The result of a preliminary calcula­tion on the orientation where the crystal c-axis is parallel to the initial muon spin polarization gives principal axes at 94 ± 5°and 111 ± 5° from the c-axis. The analogous angles for H atoms in quartz are known to be 90° and 114°. -It can therefore be concluded that muonium and hydrogen occupy the same type of site in quartz.Above about 75 K the Mu atoms 'hop' between sites, causing the relaxation rate first to increase, following an Arrhenius law with an activation temperature of about 700 K, and then to decrease due to motional narrowing, with an apparent activation temperature of about 1200 K. This behaviour (and the fits to the Arrhenius laws) are shown in Fig. 44. The single frequency (0.4 MHz) 'quadrupolar oscillation' observed for T > 220 K is due to a motionally average uniaxial hyperfine i nteraction.Fused quartz (Expt. 15*0. In fused quartz Mu 'freezes' below 75 K and exhibits only rapid relaxation due to the random distribu­tion of hyperfine perturbations from different freezing sites (see Fig. 45).The asymmetries of the Mu and y+ precession signals were also measured at various temperatures in fused quartz. No tempera­ture dependence was found, in marked con­trast to the variation seen in water ice at low temperature. The asymmetries were, respectively, a(y+) = 0.056(3) and a(Mu) = 0.107(2), indicating a fraction f+ = 0.207(15) in diamagnetic states and a frac­tion f° = 0.793(20) forming Mu. There is little or no 'missing fraction' in fused quartz; i.e., all the muons seem to be accounted for either in Mu or in the y+ signal. This suggests that the fraction forming diamagnetic bonds (which then appear as y+ ) is differentiated at high energy, e.g., by epithermal bond-breaking and 'hot atom' reactions at energies in the many-eV reg i o n .Silicon and germanium (Expt. 138). Work at TRIUMF in 1980 emphasized the importance of studying crystals grown under a variety of conditions. It is clear that the practice of classifying semiconductors according to the typeness and net concentration of elec­trically active impurities is inadequate for the purpose of understanding the muoni­um states. We expect that electrically neutral impurities such as substitutional carbon, oxygen and silicon and interstitial42Fig. 44. Exponential relaxation  rate o f  Mu in  crysta lline  quartz as a function o f  temperature. Low-temperature points (c ir c le s )  are from f i t s  to relaxing enve­lope o f  o s c illa t io n s ; high- temperature points (tr ia n g les ) are from f i t s  to  an exponential longitudinal relaxation function.T Temperatur* (*K)hydrogen can be important in their effects on the formation and subsequent evolution of the muonium. These impurities, introduced in part from the surrounding crucible and at­mosphere during growth, are in fact present in much larger quantities in our purest samples than are the electrically active i mpuri t i e s .With this in mind we have undertaken a study of the crystals listed in Table VII. Although these samples represent only the very initial phase of our study there are already some conclusions that can be drawn:1) The asymmetry of the muonium signal is not strongly dependent on the growth param­eters of the crystal. Although much more work will be needed in order to discover the trends which may exist, our first results show no gross differences among the samples.Mu IN FUSED QUARTZ VS TEMP @ 10 GTEMPERATURE ( K )Fig. 45. Exponential relaxation rate o f  Mu in  fused quartz as a function o f  temperature.2) The relaxation rate of the muonium pre­cession is dramatically larger in the one dislocation-free sample studied, ttk98-5.5- Other information about this type of crystal is presented below.Two features are known which occur always and only in dislocation-free hydrogen-grown germanium: an acceptor level at Ev + 0.08 eV and the appearance upon suitable etching of small hemispherical etch pits rather than the large rectangular dislocation etch pits seen in dislocated material. The acceptor level is attributed to a divacancy-hydrogen complex V2H; it reacts with free hydrogen in the lattice according to V2H + H V2H2 . The presence of vacancy clusters, the etch pits, and the broadening of the shallow acceptor energy levels all indicate that these com­plexes act as point stress centres. It is thus plausible that the observed increase in the muonium relaxation rate is due to strain broadening of the hyperfine spectrum. We are currently investigating a number of other samples to determine whether the fast relaxa­tion is uniquely associated with dislocation- free hydrogen-grown crystals.Measurements were also made on a large ultra- pure, dislocation-free silicon crystal. No diamagnetic p+ signal was seen at low temperature, suggesting that the small y+ signals seen in earlier experiments may have been due to muons stopping in cryostat walls, etc. (a misfortune eliminated here by using surface muons). The temperature dependence of Mu relaxation is consistent with other data.43Table VII. Muonium relaxation in germanium.Crystal Net impuritiesb Mu relaxation ratenumber3 Type cm"3 Atmosphere Crucible at 20 Kc (usee"1)344-3.8 P 1.7 x 10n h 2 Graphi te + quartz0.18 ± 0.04564-17.8 n 1 X 10n h 2 Graphi te 0.19 ± 0 .0k564-4.2 P 3 x 1010 h 2 Graph i te 0 .7 k ± 0.07A98-5-5d P 2 X I011 h 2 Quartz 3.8 ±0.1)5A90-12.0 P 2.7 x 1011 h 2 Graphi te + quartz0.26 ± 0.03495-10.5 P 3 x 1011 n 2 Graphi te + quartz0.51 ± 0.04519-9.0 P 1.3 x 1011 d 2 Quartz 0.45 ± 0.05aThe first number identifies the crystal and the second number is the distance ^in cm of the sample from the seed end of the crystal.1ectrica11y active impurities only.Exponential relaxation was assumed since the statistics are not sufficient to ^discriminate between exponential or gaussian relaxation.Dislocation-free crystal.Magnet i sm (Experiment 71)Spin q 1 asses. Using zero-field muon spin re­laxation (ZF-pSR) techniques, more data have been taken on the dilute CuMn and AuFe sys­tems. Below Tg fast depolarization results from a static Lorentzian local field distri­bution, leaving 1/3 of the polarization intact where the local field is parallel to the muon spin; this residual fraction then relaxes more slowly due to fluctuations of the dipole moments. By measuring the rate of this depolarization as well as the 'motional narrowing1 effects of faster fluctuations above Tg, it is possible to extract the spin correlation time Tq as a function of tempera­ture in a range from 10~5 sec to 10-11 sec (a wider range than has been achieved by other means). For heat-treated samples, tc varies smoothly with T right through Tg ; for quenched samples a slight discontinuity of slope is evident. Thus the ZF-pSR method is very sensitive to the microscopic homogeneity of the sample. Such curves are shown for a number of samples in Fig. b6 below; in the right-hand plot the temperature has been normalized to the spin-glass temperature Tg for each sample.These features are consistent, in general, with the experiments on neutron spin echo, transverse-pSR, EPR, NMR, Mossbauer effect and imaginary part of ac-susceptibi1ity. The loss of NMR spin echo signal around 0.7 Tq can be understood as the dynamical effect ofkbspin fluctuation in the psec region (cf. NMR frequency in MHz region) observed by ZF-pSR.ZF-pSR was also studied in an amorphous co­balt a 1uminosi1icate glass insulator exhibit­ing spin-glass behaviour. Similar tempera­ture dependence of the average correlation time was observed, but strong evidence was seen for a large distribution in values at different sites at the same temperature. An experiment at 20 mG fields failed to show the field-dependence claimed in early suscepti­bility measurements on such glasses; indepen­dent studies have now confirmed that no such effect exists.Anti ferromagnet ic CoClp'ZHpO. CoC12 ’2H20 has a crystal structure of monoclinic symme­try (space group C2/m) and is made of poly­meric - CoCl2 - chains parallel to the c-axis which are held together by relatively weak hydrogen bonds. In the antiferromagnet­ic phase (TN = 17.5 K), proton NMR has been studied by Narath. It was shown that all proton sites are magnetically equivalent, and the observed frequency at zero external field corresponds to an internal field at the pro­ton site of b .2 kG for T + 0 K. The tempera­ture dependence between k and 16 K of this field can be described by(H(0) - H (T )) ~  Ts -5 (p-NMR) . (])We studied a sample of Co C 12 *2H20, consisting of several small single crystals aligned along their c-axis, using surface p+_  10'Id210LdCCCEOui i t— n-- 1—AuFe (1 at.%)1i -n t9 ru>'oA  / \v\TT \ V -1 \ 55fc-£5 3 1V)\ 1 Ii1 T9 1_i-- L i 1 14 6 8 10 12 14TEMPERATURE (K)Hext'°«O ••  V- w ▼t 9 AuFe1 . 1 af.% »1.4 “ *■k/ * • 9 1 o' h °CuMnl.l at.% • (quenched)r\ \ >\ °\ 0.8 •• o (slow cooling) _: p ^  ...... -< T  7/k  c /  0i i i iT-Tg -|1 1 1 106 1.0 1.4Tg/TL8Fig. 46. The corre la tion  time i a o f  d ilu te -a lloy  spin glasses measured by ZF-vSR.Fig. 47. Temperature dependence o f  the 2 \iSR frequencies in  the anti ferromagnetic phase o f  CoCl2-2H20 (TN = 17.5 K).Fig. 48. Log-log p lo t o f  v (o )-v (T ) vs. log (T ) fo r  the same data as in  Fig. 47. The dashed lin e  shews the p-NMR resu lt.Fig. 49. Temperature dependence o f  the relaxation  rate 1/T2 above Tpi (transverse external f ie ld  o f  120 G).(4.1 MeV) from the TRIUMF M9 channel in the EAGLE apparatus.Figure 47 shows the temperature dependence of the y+ internal precession frequencies in the antiferromagnetic phase at zero external field. Clearly, two frequencies correspond­ing to 2.73 and 2.83 kG are seen. Between 4 and 17 K we obta i n(h (0) - H(T)) ~  T4 (p+SR) ( 2 )as it is illustrated in Fig. 48. In compari­son, the p-NMR law (1) is also plotted in Fig. 48. Each of the y+ precession signals carries an asymmetry of~0.02.A second fraction of p+ , not precessing, was identified by looking at the forward-back­ward decay. The signal corresponds to an asymmetry of~0.1, displaying a longitudinal relaxation rate of ~0 .2 5 MHz which seems to be temperature independent.Measurements in gypsum (CaSOi* • 2H20) have shown that a fraction of the y+ replaces protons of the crystal water. If this would happen also in CoCl2 *2H20 these y+ should all experience the same internal field. The magnitude of this field could well differ from the proton field due to an isotope ef­fect in the bond length, but there would be no reason for a frequency splitting. Very surprising is the different temperature dependence in the NMR and ySR frequencies. Even if the y+ do not replace protons, the sublattice magnetization is expected to re­flect always- the same temperature dependence.Another possibility is that the observed fre­quencies correspond to a two-frequency pre­cession of muonium. In this case the hypei—  fine frequency can be calculated: v0 = 1.015 GHz. The dependence of the split­ting on some local field should then be quadratic. Our data is not good enough to distinguish between a linear or quadratic behaviour. On the other hand, measurements above T|v| have shown no indication for a muonium formation.A transverse external field of 120 G along the c-axis has been applied to study the re­laxation rate above T^. Figure 49 shows that 1/T2 is proportional tov 1 / 2t -t n ' • (3)The zero field longitudinal relaxation has also been determined indicating T j ~  T2 over the investigated temperature region. Future studies in one big single crystal of CoCl2 ,2H20, in which the orientation depen­dence can also be investigated, should allow a more definite interpretation of the data.Knight shift in Sb and Sb Sb is a semimeta1 (ne = 5-5 x 10-19 cm-3) and crystallizes in a rhombohedral (3m), A7 crystal structure. We used a single crystal probe and implanted conventional y+(~89 MeV/c) from the TRIUMF M20 channel in the VARIAN apparatus.Figure 50 shows the frequency shift Av up to about 8.8 kG for the external field parallel and perpendicular to the c-axis. Writing the Knight shift in the form: K = Kjso + Ka x (3 cos20-l), we obtain: Kjso = 0 .880% and Kax = 0.209%. The dependence of Av on the external field is clearly linear and seems to reflect the property of a real Knight shift.We also studied an alloy Sb is also a semimetal (ne = 2.9 x 1017 cm-3) and Knight shift measurements showed no sig­nificant effect. We investigated the alloy at 18 K between 3.4 and 7-6 kG. In this region the frequency shift depends linearly on the field, leading to: K;so = 0.81% and Kax = 0.09%, but— and this is most striking—Fig. 50. Frequency^shift Av as a function o f  the external f ie ld  fo r  c-ax is  orientations pa ra lle l and perpendicular to the applied f ie ld .46a field-independent shift of Av = -0.2 MHz has to be added. This would show that, at zero external field, a hyperfine field of — 15 G is present at the y+ site and could indicate a y+-induced magnetic state. Before such a conclusion can be drawn, it is neces­sary to investigate also the field region between 0 and 7>.k kG. It is still possible that deviations from the linear behaviour occur at lower fields.The Knight shift in Sb is not well understood but it seems feasible to obtain more conclu­sive information, investigating Sb-alloys with other semimetals.Muon diffusion and trapping (Experiments 78 and 1^9)Single crystal A&Cu?% (Expt. 78). The y+ depolarization rate in AH is very close to zero between temperatures of 0.03 and 300 K. This indicates a fast y+ diffusion process even at low thermal activation, e.g., a band motion. Introducing impurities or defects into the lattice, these centres locally dis­tort the crystal geometry and the y+ preferably localize around them: the y+ diffusion is trap limited.A single crystal sample of AHCu2% was inves­tigated by means of positive surface y+(A.l MeV) from the TRIUMF M9 channel, using the EAGLE apparatus. The AH lattice has been analysed by X-ray diffraction and the extern­al magnetic field was applied roughly paral­lel to the <110> crystal orientation.Figure 51 shows the y+ relaxation rate A as a function of temperature. Up to about 18 K, A is almost temperature independent and starts to decrease at higher temperatures due to the motional averaging of the nuclear dipole fields. Our results are in contrast to measurements performed by other groups. The data seem to depend strongly on the Cu con­centration and the distribution of the Cu atoms inside the AH host lattice. In our particular sample the Cu atoms are supposed to be precipitated in layers (Guinier Preston zones) and presently efforts are undertaken to clarify the Cu structure by means of transmission electron microscopy.Figure 52 shows the Arrhenius plot of the y+ jump rate 1 / t c  between 22 and 2 0 0  K. Since a temperature-activated diffusion process em­pirically leads to an exponential dependence of the jump rate on temperature, one usually obtains a straight line in the ArrheniusAl Cu 2%  »mgk c ry fto l. 6 4  GAUSST ( t( )Fig. 51. u+ relaxation rate A as a function o f  the temperature in  AlCugx- A Gaussian (T < 18 K) o r a motionally narrowed (T > 18 K, a = 0.224 MHz) damp­ing have been assumed.representation. The obvious deviation from this behaviour in Fig. 52 suggests that the activation energy Ea itself is temperature dependent (and/or the pre-exponential factor). The potential energy between adja­cent interstitial sites, located within the strain fields of the Cu centres, can be shifted by an amount AE. As soon as the average AE is bigger than the band width of the y+ motion, trapping occurs. DependingA) Cu 2% ting le  crystpl, 6 4  GAUSS5 00 1• * -♦ARRHENIUS p l o t♦♦6■ • -•♦♦... . 1 1 . 1 ■ I 1 .  -♦10 15 2 0  2 5  3 0  3 5too '/TOOFig. 52. \i+ jump rate l/ iQ obtained from motionalnarrowing f i t s  vs. inverse temperature.k7on the y+ thermal energy, different-depth trapping potentials can be probed. At low temperatures (Fig. 52), the obtained activa­tion energy is Ea ~  44 K and goes up to approximately the value measured in pure Cu at high temperatures. The y+ smoothly samples the transition between the region of an al­most undistorted A5, lattice and the Cu impur i t i es .Trapping of y+ at vacancies and dislocations in alumi num (Expt. 78). Annealed 99-9995% pure aluminum sheets (0.5X25X25 mm3) were quenched from 600 K, 550 K and 500 K into a cooled HC£-water mixture (200 K), properly treated to remove residual acid, and kept in liquid nitrogen. Two sheets (1 mm total thickness) of aluminum are more than enough to stop the surface muon beam from the M9 or M 13 muon channel at TRIUMF.The zero field method was used in the present work: time-spectra of positrons emitted for­ward and backward with respect to the direc­tion of the initial polarization of the muon beam were combined to produce the relaxation functions in the specimens.The depolarization rate in the case where muons move very fast and are trapped in a time negligible compared with the depolariza­tion time is 0.185 ± 0.004 ysec-1, which is close to the theoretical value 0.20 ysec-1 for a muon at the centre of an undistorted vacancy in aluminum at zero external field.By fitting the trapping theory to depolariza­tion rates for various quench temperatures and measurement temperatures, both the acti­vation energy for muon hopping in the perfect A I  lattice (0.039 ± 0.015 eV) and the activation energy for vacancy formation (0.68 ± 0.03 eV) are extracted. The latter compares well with an accepted value from positron annihilation experiments (0.69 eV).It seems, then, that the trapping of muons at vacancies in A& is well understood and can be used as a prototype for other studies or even as a way of measuring unknown vacancy concentrations.Work is now proceeding toward an equivalent comprehensive description of muon trapping by dislocations and other types of well- characterized defects.The depolarization rate in the annealed samples is a decreasing function of tempera­ture below 300 K, suggesting a rather low binding energy of the muon to trapping sites(presumably dislocations) or a rapid motion of the defects themselves; the latter would imply that ySR can provide a means of direct­ly measuring the mobility of defects in metals— a capability of considerable utility.Nons to i ch i omet r i c metal hydrides (Expts. 149, 78). The zero-field relaxation of muons was studied as a function of temperature in ZrH(2-x) and V(2+x)H. Evidence was seen for a hydrogen sublattice vacancy-jump mechanism for muon diffusion with activation energies of 0.31 eV and 0.020 eV for ZrH2 and V2H, respect i vely.Amorphous metals (Expt. 149). The two metal­lic glasses studied have quite different magnetic properties. Co78Si10B 12 shows ferromagnetism in both amorphous and crystal­line phases at room temperature. By con­trast, a-Ni7gSijq B i2 is paramagnetic at room temperature, but the crystalline phase is ferromagnetic. What is even more interesting is that the curie temperature of a-Ni78Si10Bj2 is said to be lower than 77 K. Unfortunately, the detailed magnetic properties are unknown to date.Our main questions about these metallic glasses were thus the following: 1) what isthe effect of the paramagnetic-to-ferromagnet- ic phase transition of a-Ni78Si 10B 12 at low temperature on the muon spin relaxation;2) are positive muons depolarized by the ferromagnetic precipitated phase in the an­nealed a-Ni78Sijq B j2 ; and 3) what is the effect of the structural disorder on the dif- fusional motion of positive muons in a-Co78S ii qB 12•Amorphous samples were prepared as stacks of about 100 foils (2 0x30x8 mm) cut from thin ribbon specimens. Such relatively thin sam­ples were made practical by the use of a 4.1 MeV 'surface muon1 beam from which all posi­tron contamination had been removed by the M9 dc separator. Using the zero-field method, the forward/backward asymmetry of decay positrons emitted from initially polar­ized positive muons was measured for a-Ni78Si 10B 1 2 and the annealed sample (750 K x 30 min).The fitted exponential depolarization rate JL for a-Ni78Si 18B 12 decreases only slightly with temperature up to 200 K; the initial asymmetry is also nearly constant (0.34) in this low temperature region. We found no coherent precession of the muon spin. The48muons did not depolarize at room temperature or at higher temperatures 393 K, ^73 K and 573 K. The physical reason for the nearly temperature-independent depolarization rate and the lack of a coherent precession fre­quency in the ordered phase is unknown at present. One possible explanation is as follows: a number of different local atomic configurations around the Ni atom are realized in the amorphous state; therefore, the magnitude and direction of the magnetic moment of each Ni atom are random in the ordered phase, but the magnetization is not zero (though probably very small). The ob­served results are compatible with this picture. The ordered phase of a Ni 7gS i10B 12 is in some respects similar to a spin glass.The zero-field longitudinal depolarization function was also measured for amorphous and annealed Co78Si 10B 12 at a few temperatures. The crystallized sample was prepared by an­nealing at 770 K for 20 h in vacuum. There is little difference between the overall shapes of the relaxation functions for the two phases; in each case a small asymmetry and a fast depolarization were observed. We believe that the ySR method will be a useful tool for investigating not only the metal- metalloid systems but also for the rare earth amorphous alloys in which the local magnetic anisotropy plays an essential role.E xperim ent 147Mu fo rm a tion  and reaction  dynam ics in the gas phasey+ charge exchange and muonium formationAn initial study of the pressure dependence of the muonium (Hu) formation amplitude referred to in last year's annual report is now complete. Some results are given in Table VIII for the noble gases. Similar trends have been seen in polyatomic gases (H2 , N2 , NH3, CH^) and for comparison the N2 results are also given in Table VIII, In this table the fraction of y+ thermalizing as 'free' y+ (f^) and as Hu(f|v|u) are absolute fractions in that they are all measured relative to fy = l.O in A£ (the Mu amplitude has been multiplied by two to account for unobserved 'singlet' Mu), in contrast to the data presented in last year's annual report where the fractions were separately normal­ized to unity in each gas. The last column in Table VIII shows the 'lost' fraction, f[_ = 1 -f -fnu> which is seen to systematical­ly decrease as the gas pressure is increased.Similar results have been seen in Kr gas at LAMPF.Our initial interpretation of this P depen­dence was that it was probably largely due to a solid angle effect. The range spread of the y+ in the gas becomes greater at lower pressures and hence the distributed initial phase of y+ (Mu) precession coupled with a large solid angle of acceptance would be ex­pected to result in lower asymmetries at lower pressures. That a change in initial phase accompanies a decrease in P can be seen in Table IX, which presents results for the y+ signal in Ne. However, Monte Carlo cal­culations predict that the effect of an extended stopping distribution on the + (Mu) asymmetry would be, at most, a 30% effect whereas some of the data in Table VIII reveal changes by as much as a factor of three. It is clear then that there is a significant P dependence affecting the for­mation probability of the Mu atom.In general, one can speak of Mu formation as occurring in three different energy/time zones. The y+ first enters the gas with several MeV of energy (~3 MeV for surface y+) , most of which is given up during Phase I in the normal Bethe-Bloch type of ionization processes as the y+ slows down to ~30 keV.At 1 atm pressure, this takes ~ 1 5 nsec.Phase II is the charge exchange regime wherein Mu is formed and lost in a series of charge exchange cycles,Table VIII. Pressure dependence of measured amplitudes and fractions for muon and muonium thermalization in the noble gases.G 3 5 P(a tm )Ap+a AMu3 V(%)fMu(%)fLCtt)He 1.2 0.15 0 A3 0 552.8 0.21 0 60 0 Ao3-0 0.22 0 63 0 35Ne 0.1(0 0.09 -0.01 26 ~5 700.80 0.10 0.02 29 10 601 .2 0.17 0.01 b A9 5 501 .6 0.26 0.02 7A 10 152.0 0.30 0.03 86 15 0Ar 1.1 0.07 0.11 20 62 152.5 0.10 0. 1A 2A 71 0Kr 0.1(0 -0.02 0.0A ~6 23 700.65 0.01 0.09 3 51 A50.90 0.01 0.12 3 69 30Xe 0.1(0 -0.02 0.05 29 650.65 0.01 0.09 3 51 A5n 2 1.0 0.03 0.12 9 69 202.5 0.07 0.17 18 87 0^Estimated to be accurate to ±0.02.Obtained in a separate run with ultra-pure Ne. Given to the nearest 5%.i»9Table IX. Effect of pressure on the initial phase in Ne.Ne pressure (mm)<t>R(deg)A(ysec-1)300 163 ± 26 0.35600 219 ± 8 0.17900 264 ± 4 0.0901200 320 ± 3 0.0581500 286 ± 3 0.035Phase II is the charge exchange regime where­in Mu is formed and lost in a series of charge exchange cycles,_ a 10 . y + e .. M u ,CT01ultimately emerging as either Mu or 'free' y+ (no doubt bound in a molecular ion) at some still epithermal energy of ~ 2 0 e V , depending on the specific velocity dependence of oio ar|d cj'oi in the moderator gas. Esti­mates based on proton stopping powers predict about 100 of these charge exchange cycles for the y+ (H000 for the proton) in a total time ~ 0 .1 nsec at 1 atm pressure. The time here is the crucial parameter. Since Mu oscillates between 'triplet1 and 'singlet' states at the hyperfine frequency v0 = 4463 MHz, the y+ is effectively 50% de­polarized in a time At = l/v0 = 0.2 nsec.If an equal amount of time is spent by the y+ during each charge exchange cycle, then At/exchange would only be — 0.001 nsec, << l/v0 and £o y+ depolarization would occur. In Phase III, the thermalization process is completed as the y+ (Mu) slows to kgT in ~10 nsec at 1 atm P, again dependent on the moderator. In Phase III, At >> 1/v0 and the normal 50% of the y+ (singlet) polariza­tion is lost. The above scenario would pre­dict then no additional (P-dependent) depol­arization, contrary to observations.The crucial regime is Phase II and no doubt it is only the last one or two charge exchange cycles which are important and which consume most of the total time. By lowering the stopping P, e.g., by a factor of 3, we can increase this time by the same factor thus enhancing the chance that Mu will spend sufficiently long time in the singlet state to be (partially) depolarized. This is surely what the data in Table VIII are revealing. Qualitative estimates of the time involved can be gained from the per cent changes in polarization which can in turn berelated to the cross sections for charge ex­change, since At ~  l/(vop), where V  is some average velocity and p is the gas density.It is just this area of very low energy charge exchange that is generally inacces­sible to proton experiments and where we hope that the y+ will be able to play a major role. The above data have been presented at the recent 2 nd International Topical Meeting on Muon Spin Rotation.Mu spin exchangeCompleted room temperature (300 K) measure­ments of the spin exchange cross sections ctse for Mu + 02 and Mu + NO have been published. Contrary to the statement in last year's report, more recent H atom results for H + 02 and H + NO spin exchange reveal that, within errors, as^(Mu) = ctse(H). Such a mass independence in the spin exchange cross sections is consistent with the expectations of a simple random phase approximation (RPA) to the basic scattering cross section, the latter given by£c°SE = T T  £  (2&+1) sin2AJl, (l)£=0where A^ is the difference in phase shifts between singlet (doublet) and triplet (quartet) scattering for Mu + NO (Mu + 02).In the RPA, sin2A£ averages to 1/2 up to some 'cut off' partial wave l c , yielding°SE = ^ 2  S  (2*+0 *  tt R|ff , (2)giving some effective geometrical cross section with the further approximation thatf c£  (2H+1) «  £  .0 c This simplistic prediction of mass (and temperature) independent 033 near 300 K is consistent with detailed theoretical calcu­lations comparing Mu + H with H + H and Mu + 02 with H + 02 spin exchange.Measurements of the temperature dependence of acjj: for Mu + NO and Mu + 02 in the range ~300-500 K have been carried out which reveal, within errors, that aSE is essential­ly independent of temperature. This result is also consistent with the RPA calculations mentioned above. The data are given in Table X. Detailed theoretical calculations comparing H and Mu + 02 spin exchange actually predict a weak (~50%) increase in 0SE f°r both h and Mu but that their ratio50Table X. Observed depolarization rate constants and spin- exchange cross sections for Mu and H with NO and and 02 in the temperature range 295_i»78 K.System Temperature (K) kd ( 10- mo 1 ec .■1C- 1'cm3-sec"1)0 S E(1 O’•16cm2)Mu + NO 295 ± 5 2 .8L + 0.2 10.0 ± 0.7Mu + NO 385 ± 5 3.30 + 0.23 10.2 ± 0.7Mu + NO A38 ± 5 3.62 + 0.25 10.6 ± 0.7Mu + NO L78 ± 5 L.O + 0.7 1 1 . 2 ± 2.0H + NO 310 10.6 ± 0.9H + NO 373 9-9 ± 0.9Mu + 02 295 ± 5 2.6L + 0.L 7.9 ± 1 .2Mu + 02 LOO ± 5 3.L5 + 0.L 8.9 ± 1 .0Mu + 02 L38 ± 5 3.95 + 0.3 9-7 ± 0.7Mu + 02 L78 ± 5 L.15 + 0.7 9.8 ± 1-7H + 02 310 8.8 ± 0.7H + °2 315 9.8 ± 1 .0H + 02 350 8.3 ± 0.7H + 02 388 8.0 ± 0.7should be largely T independent. Again with­in errors these calculations are reasonably consistent with the data in Table X. It will be important then to extend our measurements to both higher temperatures (up to 1000 K) and, particularly, to lower temperatures where specific resonance enhancements of ose(Mu) are predicted.The spin-exchange cross sections in Table X have been calculated on the basis that any (weak) intrinsic T dependence in dje can be ignored. That is to say that the reaction (depolarization) rate constant kp can be directly related to the experimental depol­arization cross section 0p and hence to agjr by the usual 'hard sphere' result, i.e.,kp = o p • v = oSE-v , (3)where f is a statistical factor discussed in a paper presented at 2nd Int. Topical Meeting on Muon Spin Rotation [Fleming, Mikula and Garner, Hyperfine Interactions, in press]. In Eq. (3) V  is the mean colli­sion velocity and hence the rate constant data in Table X is expected to reveal a T 12'2 dependence. This is shown in the log- log plot of Fig. 53 for the Mu + NO reaction in which k(T) = ATn is plotted, giving n = 0.6 ± O.A. A very similar plot was ob­tained for Mu + 02 yielding n = 1.0 ± 0.5. Although the errors are admittedly large, the results are consistent with n = 0.5, as expected. Higher temperature data will be important then in reducing the size of these errors, thus allowing a more definitive statement of the T dependence of kp and hence agE .Chemical reaction dynamicsAlthough the very large difference in iso­topic mass between Mu and H (Mmu = 1/9 M^) is relatively unimportant in a 'collision con­trolled' reaction like spin exchange, it can be of crucial importance in the proper interpretation of 'activation controlled' chem iaa l reactions like Mu + F2 or Mu + H2 , etc. Gas phase chemical reactions using surface y+ have long been a focus of our work at TRIUMF, as detailed in previous annual reports. We are currently investigat­ing the temperature dependence of the reac­tion rates of Mu + C2Hit, Mu + HBr and Mu +H2 . These are fundamentally very different types of chemical reactions. The Mu + C2 H4 reaction proceeds via an addition reaction forming a muonic radical as an intermediate state whereas Mu + HBr and Mu + H2 are (H atom) abstraction reactions.Mu + CH2 = CH2 MuCH2 - CH2Our recently measured rate data for the Mu addition reaction with ethylene between and k8k K are compared with those due to Lee and coworkers for the analogous H atom reac­tion between 198 and 320 K in the Arrhenius plot of Fig. 5^- Because this reaction follows an energy transfer mechanism with a moderator M:Fig. 53. A log -log  p lo t k (T ) = A'F1 fo r  the spin ex­change reaction Mu + NO, y ie ld ing  n = 0.6 ± 0.4. A very s im ila r p lo t was obtained fo r  Mu + 02 giv ing  n = 1.0 ± 0.5.511000/TEMPERHTURE (K'1)Fig. 54. Arrhenius p lo t o f  the rate constants fo r  the reactions o f  Mu (top ) and H (bottom) with ethylene in  the gas phase. E rror bars shown in  both cases are la. Arrhenius parameters (2a erro rs ) are: kMu = (4.4±1.6) x 10~11 exp(-1160±270 cal mole~l/RT) and kg = (3.67±0.66) x 10 exp(-2066±83 cal mole~^/RT) cm3 molecule-1 see-1.H + CH2 = CH2 t  CH3 - CH2 ■ * + M -*CH3 - CH2 . + M ,where the asterisk indicates vibrational ex­citation, it is necessary to measure the addition reaction rate at sufficiently high moderator pressure to ensure that the unimol- ecular decomposition of the radical does not occur. The H atom measurements of Lee e t  a l .  were done with Ar moderator at pressures ranging from 300 Torr at 198 K to 760 Torr at 320 K, and were found to be in the high pres­sure limit. The Mu atom reactions were observed in 800 Torr of N2 at all tempera­tures. To determine if the Mu reaction rate constants are also from the high pressure limit, the room temperature measurement was repeated in 1500 Torr of N2 - the measured rate constants were 6.1±0.5 and 5-5±0.8x 10-12 cm3 molecule-1 sec-1 in 800 and 1500 Torr N2 , respectively (2a errors). The agreement between these measurements is considered to be good evidence that the Mu experiments were also in the high pressure limit. Indeed, for reasons associated with the behaviour of muonic radicals, it is expected that the MSR technique as applied to gas phase studieswill be insensitive to any range of moderator pressure, except possibly at very low temperatures.Comparison of the Mu and H data reveals a Mu:H isotope effect ratio of 5-6±0.6:1 at 295 K and a Mu activation energy which is only 56±13% that of H— behaviour which is very similar to that for the Mu(H) reactions with F2 . In the absence of any detailed theoreti­cal calculations, these isotope effects are most readily explained as arising from increased quantum tunnelling in the Mu reac­tion. If the interpretation of quantum tunnelling is correct, then it may imply that the activated complex is 'loose', (i.e.) the barrier to the addition reaction is early. Jakubetz has pointed out that the full reduced mass effect of H isotope substitution is felt as tunnelling in H atom reactions on trajec­tories which are parallel to the reactant valley of the potential energy surface, and thus tunnelling is expected to be important when the energy barrier is located in the reactant valley.Further work planned in the study of this reaction includes: extending the measurementsto lower temperatures to cover the range of the H atom measurements, checking that the rate constants measured at high temperatures are independent of moderator pressure and, finally, attempting to observe the muonic ethylene radical directly via MSR... , UD jf MuBr + HMU + HBr< M u H  + BrA preliminary study of the total (abstrac­tion + exchange) rate constants for this system between 294 and 355 K gives the Arrhenius expression: k^u = (1.1±0.6) x 10-1° exp(-1160±360 cal mole-1 /RT) cm3 molecule-1 sec-1. In analogy to the H atom reaction and because of the large endoergi- city of the exchange reaction channel for Mu, which arises from the large zero point energy of the MuBr bond, it is expected that these 'total' rate constants in fact correspond to the abstraction reaction chan­nel only.The most recent direct measurement of the analogous H and D atom rate constants at 300 K are by Husain and coworkers who found k^ = 6.0+0.1 and kg = 4.1±0.1 x 10-12 cm3 molecule-1 sec-1 for the reactions H+HBr and D+HBr. Compared with these measurements the Mu:H:D rate constant ratios at 300 K are 2.65±0.09:1 :0.68±0.02 which are very close52to the trivial mass factors! If anything, there is an inverse isotope effect favouring the heavier D isotope. This result is con­sistent with the classical trajectory calcu­lations of Polanyi and coworkers which show that the reaction probability is largely dependent upon the time during which the attacking H isotope interacts with the large Br atom. If this time is sufficiently long, then the attacking H isotope will be clouted by the other H atom as the HBr molecule rotates. These calculations suggest that the reaction probabilities well above threshold will be ordered such that the heavier the attacking atom and the lighter the H isotope in HBr, the more favoured the reaction. Further work must be done on the measurement of the activation energies for all the isotopic variants of this reaction in order to gain a firmer handle on the reaction process.Mu + H2 -*■ MuH + HThis reaction is fundamentally probably the most important one that we can measure. The accurate ab i n i t i o  potential energy surface of Liu and Siegbahn has made it possible to test various theoretical methods by directly comparing calculated results with experiment Any disagreement resulting from this com­parison cannot be attributed to a deficiency in the surface but rather to a weakness in either the experiment or theoretical method. However, for the H and D isotopic variations of the H+H2 reaction, the experimental un­certainties are generally much larger than the calculated isotope effects, thereby frustrating this valuable comparison between theory and experiment. In the case of Mu the isotope effects are expected to be large Connor and coworkers have calculated one­dimensional rate constant ratios for Mu:H of2.7 x 10-4 at 300 K and 0.1A at 1000 K.Other theoretical calculations including 3D calculations are presently being undertaken.Experimentally, the reaction rate constants for the Mu+H2 reaction are difficult to measure because the reaction rate is so slow, largely due to the endoergicity of the Mu+H2 ( v = 0 )  reaction which arises from the large zero point energy of MuH. The MSR technique, of course, requires that the reaction rate be observed on the time scale of the muon lifetime, 2.2 ysec. Based on the calculations of Connor we expectecj that the Mu reaction would only be detectable at temperatures in excess of 600 K with H2 pressures at 700 kPa. This indeed is thecase as shown by a preliminary measurement of the bimolecular rate constants kj^ u in Table XI. The corresponding rate constants for the H atom reaction are taken from the literature. These calculations are in fact consistent with calculations at 1000 K.Table XI. Mu and H rate constants3 for reaction with H2 gas.T(K) ■ b kMu •<HC kM u (lD)d600 3.2xl0"15 1.6xl0-13 3.2xl0-15700 1 .8xl0_11+ A.OxlO-13 2. Ox 1 0"li+800 5.3xl0-14 1.OxlO-12 6.3X10"11*3 o i l^Al 1 given in units of cm mol" sec" .Preliminary, with estimated errors of ±50%. jH atom values from the literature. Theoretical 1-dimensiona1 calculations from the literature and based on the H atom values in the adjacent column.The data in Table XI reveal that kj^ u << k^, which is a marked reversal of the 'normal' isotope effect found in gases where Mu is in­variably faster than H, by as much as a factor of 10 in the case of the Mu + F2 reac­tion. The basic reason is the one mentioned above— the large endothermicity of the Mu + H2 (v=0) reaction. Since the H3 poten­tial energy surface is accurately known, the good agreement obtained between (ID) theory and experiment is a strong indication that the basic theory of gas phase reaction dynamics is well understood. It remains important to extend the Mu atom rates to higher temperatures and also to improve the errors on the data in order to provide a definitive comparison between theory and ex­periment of this most sensitive of all H isotope isotopes. Such studies are currently under way.During 1980 Expt. 157 had some 75 shifts of beam time on M20. Several projects were initiated using muonium atoms to study fundamental aspects of chemical kinetics in liquids which are not readily discernible by other techniques, such as 1) activation, diffusion and tunnelling of reactants;2) the mass dependence of diffusion; 3) sol­vent- 1 imi ted processes , including 'cage effects'; b) membrane permeability, or theE xperim ent 157M uonium  ch e m is try  in  liq u id s53TI Mr IN uSEC :16 N5EC/BINIFig. 55. MSR data and computer f i t s  to Eq. (1 ) fo r :  (a ) p u r ifie d  tetramethylsilane (TMS) and (b) pu rified  n-hexccne.effect of 'Inclusion' on reactivity; and 5) the mechanism of muonium formation and its possible relation to radiation chemical processes. To this end muonium was studied in organic solvents, in aqueous media con­taining micelles and eye 1odextrins, in dilute porphyrin solutions, in the presence of high electric fields and at various temperatures (over a rather limited range).Last year we reported that we had found muonium, just, in tetramethylsilane (TMS).Now we readily find it in any saturated hydrocarbon providing it is very pure.Figure 55 shows muonium with a chemical life­time greater than 1 psec in n-hexane and TMS. Furthermore, its yield is comparable to that found in water or alcohol. Since these four liquids have very different free electron mobilities and spur lifetimes, these results seem to argue strongly against the spur model of muonium formation. This is corroborated by the fact that externally applied electric fields up to kO kV/cm, which change the intraspur neutralization probabilities, did not affect the yields.A comparison of the reactivity of muonium with protoporphyrin (no Fe3+) and hemin (containing a centrally co-ordinated Fe3+ion) showed that spin exchange with the central ion was the dominant reaction but that the porphyrin sheath protected the Fe3+ more effectively than does CN” in Fe(CN)3 . Solute reactivity towards muonium was also studied for I2 in eye 1odextrins and for 12 , phenol and napthalene in various-sized micelles. A selection of data is given in Fig. 56 and Table XII to show the effect of the critical micelle concentration (CMC), but not the size of the micelle, on the reaction rate constant of muonium atoms. Various aspects of the effect of the micelle on the encounter frequency, on the effect of 'caging' on the encounter pair, and on the solvation of the reactants, are of interest in these experiments for implication to solution reaction kinetics in general. The influence of temperature and solvent struc­ture on these muonium reactivities will be studied further.[NaLSJ/mMFig. 56. The muonium reaction rate constant with naphthalene as solute (a t ~10~h M) vs. the concen­tra tion  o f  monomeric surfactant molecules (NaLS) in  aqueous so lu tion  at 295 K. The errors given are two s ta t is t ic a l standard deviations.5^Table XII. Muonium reaction with I2 in different micelles.No. of C in Surfactant hydrocarbon cha i nAgg regat i on numberCMC(M)kM/1010 bel owM ^ s ' 1CMCkM/ 1010 M_1s_1 above CMCku (above) k^ (below)NaHS 6 30 0.4 1.46b ± 0.34 4.0b ± 0.9 2.7NaOSA 8 40 0.14+1OOCO 0.30 4.lc ± 1.0 2.3NaLS 12 62 0.008 *^1 0 Q.1+ 0.80 5 . 0 d  ±  0 . 8 2.9uI2 concentrations were 0.04 mM.NaHS concentrations: below CMC = 0.19 M, above CMC = 0.83 M (where = 0.20). cNa0SA concentrations: below CMC = 0.05 M, above CMC = 0.19 M. cNaLS concentrations: below CMC = 0.003 M, above CMC = 0.030 M.E xperim ent 60 M uonium  fo rm a tionThe long term objective of this experiment has been the production of a substantial amount of muonium (p+e-) in a vacuum environ­ment. To this end, formation studies in a variety of finely divided oxide powders and other materials have been carried out and some better comprehension of the processes involved thus achieved.The first observations of Mu formation in the liquid and solid phases of Ar, Kr and Xe were made and careful measurements made of the fractions of muons stoppinq as muon­ium atoms [J. Chem. Phys., in press].In all cases these fractions were substan­tial ranging from 0.43 ± 0.09 in liquid Xe to 0.97 ± 0.29 in liquid Ar and as high as 1.00 ± 0.10 in solid Kr. Both liquid Ar and solid Kr targets showed evidence for two distinct Mu spin relaxation rates, the fast relaxation component may well arise from the interaction between the Mu atom system with free electrons and radicals produced in the spur at the end of the track. Again in the solid phases the data are consistent with the sum of the fractions of muons and muonium atoms observed by spin rotation equalling unity; in contrast in the liquids roughly half of the incident muons are un­observed by pSR after 100 nsec, presumably the result of some fast depolarizing mech­anism. Apart from contributing to the muon­ium formation puzzle, this data shows fur­ther that it is possible to study Mu reac­tions with substances deposited in the solid phases of inert rare gas moderators for com­parison with reactions of H atoms underidentical circumstances. At lower tempera­tures it may also be possible to compare Mu hyperfine splitting shifts with data from H atoms deposited in an inert element matrix.A short experiment was epithermal Mu atoms in positive muons emergin foil. Charged particl the emerging beam by a the decays of muons in tral beam observed. C tained for epithermal quantitative estimate poss i ble.undertaken to look for a beam of low energy g from a thin gold es were removed from sweeping magnet and a stopper in the neu- lear evidence was ob- neutral particles but a has not yet provenEffect of inert surface films on muonium relaxation in oxide powdersMSR measurements on finely divided S i O2 > ^ 2^ 3 and MgO powders at 6 K, using a cryostat in which cold helium gas circulated through the powder, showed extraordinarily small relaxa­tion rates, indicating that muonium is being produced and reaching the void region rapidly where it stays until decay. The Mu atoms do not thermalize inside the grains as previous­ly be 1i eved.Measurements made on A&203 as the temperature was raised showed a dramatic sharp increase at 12.5 K. By taking measurements over a range of pressures 0-700 Torr at different temperatures, and also with neon, it became clear that the relaxation rate was a very steep function of the concentration of He (or Ne) on the surface and was indicating the completion of an inert gas monolayer with no vacancies in the film through which a Mu atom might attach.55Clearly Hu atoms can be used as a unique probe into a variety of two-dimensional systems deposited on such surfaces.Muonium conversion to antimuoniumThe data from the Mu -> Mu conversion experi­ment completed in 1979 have now been analysed. The high density stopping p + beam, available on the M 13 channel, together with the use of a target of 17 thin layers of fine silica powder supported on collodion films enabled a limit to be set on the coupling constant G^uMlT < ^2 Gpermj (95% confidence limit). A similar experiment performed in argon gas at 1 atm and room temperature produced a limit of Gp(up|u < 190 Gfermi •While considerably improved sensitivity is now required to test multiplicative muon number conservation in the neutral current interaction, this does represent a consider­able improvement on the existing limits of 5800 Gpermi set by Amato e t  a l .  in a MuMu experiment and of 610 Gpermj in an e~e~ -> y_y- search by Barber e t  a l .E xperim ent 150Backward m uon reactionsUnlike most other ySR experiments at TRIUMF, which utilize surface muons, Expt. 150 em­ploys backward muons, since these have suffi­cient momentum to penetrate both thick targets and magnetic fields of several kilo- gauss. An existing ySR apparatus, built by the University of Tokyo group for an earlier experiment, was available, and this was used throughout 1980 whilst an improved apparatus was constructed. The main difference is the use of a large pair of Helmholtz coils (28 cm i.d.) instead of the solid poletipped electromagnet of the Tokyo apparatus. This results in greater target space and much improved access. The coils are mounted on a cart which can be rotated to provide magnetic fields both longitudinal and transverse to the beam. The counters are mounted on a separate cart in such a way that the whole array can be rolled back to permit access to the target and collimators. As a result of the improved counter geometry b5% of the muons stopping in the target lead to good events compared to 15% with the old apparatus.Despite the disadvantages of the old set-up a good start was made on the project. For example muonium-substituted free radicals were observed unequivocab1y for the firsttime at TRIUMF. In addition to muonium eye 1ohexadieny1 and other radicals observed previously at SIN, muonium 2-furanyl was detected as a new species. The measured hyperfine frequency is 379 MHz, which may be compared with 339 MHz found for the related thiophenyl radical. The increased hyperfine frequency for furanyl implies higher unpaired electron spin density on the 3-carbon. This can be understood in terms of reduced de­localization in the oxygen-containing hetero­cycle of furan compared with the sulphur in th i ophene.All muonium radicals detected to date stem from muonium addition to organic molecules.It is hoped to extend this work to inorganic systems. A first step was a radical search, so far unsuccessful, using a target of tin tetramethyl, both at room temperature and at -A0°. Other molecules will be tried, and the tin tetramethyl system will be investi­gated in other ways.Once the capability of observing radicals was demonstrated most experimental effort was directed towards the goal of elucidating the earliest events in muonium chemistry—  radiolysis effects. A comprehensive study of aqueous solutions of potassium chromate en­tailed measurements of diamagnetic muon polarization on 8 concentrations at 6 mag­netic fields, as well as measurements of the muonium decay rate in a further series of 5 low concentrations. The rate constant de­termined from the latter measurements is consistent with a diffusion controlled reac­tion, as was expected from earlier measure­ments on permanganate solutions. In both cases it is assumed that muonium is oxidized to leave the muon in a diamagnetic molecule:Mu —5 pgq MuOH .Analysis of the diamagnetic polarization (Fig. 57) yielded the result that the ini­tial diamagnetic fraction increases with chromate concentration, as is the case for other strong electron scavengers. The in­terpretation under the spur model is that muonium formation is being inhibited by removal of presolvated electrons formed in the muon radiolysis track. These and all the earlier results for muonium inhibition were subjected to quantitative analysis in a novel manner, using the method of competi­tion kinetics. The predicted straight line relationship between the inverse fraction of muonium inhibited and the inverse concentra­tion of electron scavenger is obeyed56Fig. 57. Muon po la riza tion  in  aqueous solutions o f  chromate; concentration (top to bottom) 1.0, 0.4, 0.2, 0.08, 0.04 and 0.01 M.(Fig. 58), and rate constant ratios were derived from the slopes of the plots.An exciting new venture has recently arisen in the form of a collaboration with the metal- ammonia group at Arizona State University (Prof. Bill Glaunsinger and colleagues) and with Dr. Ron Catterall of Salford University, England. As well as being fascinating inFig. 58. Competition k inetics analysis.their own right, metal-ammonia solutions are highly relevant in the study of early events in muonium chemistry, since electrons solvated in ammonia are more stable than in water, where most muonium chemistry has been carried out. In first exploratory studies muonium has been detected in pure ammonia in both the liquid and solid phases.57APPLIED PROGRAME xperim ent 61 B iom ed ica l programStable high intensity beam time (100 yA) was available on a more regular basis during 1980 which has enabled a marked acceleration of the biomedical/prec1 inical program. The physics and dosimetry measurements, however, still had to use the periods of lower inten­sity (<30 yA) to enable the biomedical experiments to proceed,uti1izing the maximum amount of beam time.The M8 channel performance and reliability have been considerably improved so that all the biomedical experiments in 1980 were completed without any channel failure. A versatile, discrete step range shifter was installed early in the year to generate reproducible depth dose profiles of any desired characteristic. This is essential because it has been observed that the bio­logical effect of t t "  depends not only on the physical dose, but also on the field size and beam contamination, and so depth dose profiles of various characteristics will be required under different conditions to pro­duce uniform tumoricidal effect over the whole tumour volume.The biomedical channel contains two sextupole magnets which were designed to provide large field sizes for cancer treatment. However, the uniformity of large field sizes produced in this way was not satisfactory, and it was decided to switch to spot scanning for field size control. Spot scanning also presents other advantages, such as less beam loss in collimation and the ability to cover field sizes of various size and shape. A scanning patient couch under computer control was designed by the TRIUMF design office and will be installed in the summer of 19 81.Progress has also been made on some funda­mental studies of t t "  dosimetry. The rela­tive i t "  capture ratios in various elements of clinical interest have been measured in many organic compounds and in animal tissue. This is one of the most important remaining sets of data required for the calculation of i t "  star dose. Phantoms matched in atomic composition as well as in density are essen­tial for charged particle dosimetry, especially with t t "  beams. A systematic method has been developed for formulating tissue-equivalent liquids with a specified physical density.Cultured cells from hamsters were used to investigate the relative biological effec­tiveness (RBE) of the various beam tunes produced compared with conventional radia­tion (Table XIII). These cells were suspended in gelatin media during irradia­tion to map the spatial variation of biological effect. In addition, the gelatin technique has also been used to investigate the possible dependence of biological effect on field sizes, the effect on hypoxic cells, the effect on cellular recovery and the interaction of t t "  with drugs.A complete study of the dose dependence of RBE using the mouse foot skin reaction tech­nique was completed in April. This involved a total of eight experiments lasting over two years covering a variety of fractiona­tion schemes including 1, 2, 10, 16 and 20 dose fractions. The RBE is observed to increase steadily with the number of frac­tions (i.e., with decreasing dose per frac­tion), as shown in Fig. 59.Two runs of pig skin irradiation were made in May and November. The pig skin was used as a simulation for human skin to look for acute and late tissue reaction to t t "  radia­tion. Reference radiation using X-rays was made to different parts of the skin of the same pigs for comparison.Human skin nodule irradiations were con­ducted during March, August and November to investigate the RBE on the human skin directly. A total of seven patients wereDOSE <GRAY) /  FRACTIONFig. 59. Variation o f  RBE with dose per fra ction  fo r  the mouse fo o t skin reaction. The curves define the 90% confidence in terva ls .58Table XIII. RBE vs. depth for various tt” beams at TRIUMF: Measured in CHO cells at S=10%.RBErion beam PIateau P rox i m a 1 Centre Di stal Downst reamModu1 ated5 cm peak 5x5 cm field 1.16 1 .22 1 .24 1.39 1.48Modulated10 cm peak 5X5 cm field 1.11 1.18 1 .26 1 .47Modu1ated10 cm peak 10x10 cm field 1 .22 1.27 1.32 1 .59Unmodulated5X5 cm field 1.10 1 .29 1.37treated, but the November run had to be aborted after 4 fractions due to a major cyc­lotron failure. The treatment regimes used were 10 daily fractions of 325 rad of t t "  at the peak dose region, with a k cm diam circu­lar beam as defined by a brass collimator in contact with the patient skin.E xperim ents 77, 93 Iso tope p ro d u c tio nProduction of 123I and 127Xe from the cesium spallation facility for research and develop­ment continued through 1980 with financial support from the Vancouver Foundation. A total of 11 Ci of 123l was distributed to twelve hospitals in British Columbia, two hospitals in Ontario and one laboratory in the United States. In the last quarter the Nuclear Medicine Department of B.C. Institute of Technology received small quantities of 123I for use in the training of medical technicians. The purpose of the distribution program has been to familiarize the medical community with the advantages and problems associated with regular clinical use of 123I.In December a questionnaire was circulated to the users. All were very appreciative of the TRIM/TRIUMF program. Most of the material was used for anatomical studies of the thyroid, or dynamical measurement of thyroid performance, with a few cases for localization of thyroid cancer metasteses. Although there were no reports of 123l used for labelling pharmaceuticals from external users, many expressed keen interest in receiving l23I fatty acids, hippuran andfibrinogen in the future. Because of the superior imaging characteristics and low patient radiation dose, the users felt that the added cost was justified; several now purchase commercial 123I although none had done so before the TRIM program. Unfortu­nately one negative reaction was very clear in all reports: the supply schedule from TRIUMF did not allow busy nuclear medicine departments to adopt 123l for standard radio iodine procedures. Requests were made for two or three production days per week, as well as back-up for shutdown periods.There were reports of patients hospitalized for several days, as well as some who travelled 350 km from the interior of B.C., to receive TRIM 123I. One can appreciate that the present exigencies of clinical ope­ration create pressure to adopt inferior substitutes to 123l that are readily available.In September the TRIM group presented an ac­count of its experience with the spallation iodine facility to the Second International Symposium on Radioiodines sponsored by the University of Alberta at Banff. Vancouver General Hospital and the Hospital for Sick Children also reported application projects with our iodine. Conference proceedings will be published as a special issue of the Journal of Radioanalytica1 Chemistry in 1981.A subsidiary problem of interest in the use of spallation-produced 123l is the biologi­cal pathways of trace 121Te, an unavoidable contaminant. A study has therefore been undertaken to elucidate this pathway in59collaboration with the Human Monitoring Laboratory of AECB. At the end of the year TRIM had developed a process for separating 17_day 121Te from 60-day 125I, another by­product, to purities better than 99-9%, and a sample quantity has been shipped to Ottawa.Studies of a potential tumour-sensing agent, 52Fe-1abel 1 ed porphyrin, came to a conclusion this year with a series of i n  v i t r o  and animal i n  v iv o  measurements using one tumour model. Tissue culture uptake was shown to be highly selective of the species of porphyrin used. I n  v iv o  results employing the pre­ferred species, however, were a disappoint­ment, most of the material being removed by the liver rather than concentrating in the tumour. Details are to be found in the Master's thesis of R. Thaller, Univ. of British Columbia, Dept, of Pharmaceutical Sciences, 1980.Byproduct 127Xe from the spallation facility was extracted this year and supplied in small quantities to EIR (Eidgenossisches Institut fur Reaktorforschung) in Switzerland and the Danish National Health Services for evalua­tion.As 1980 came to an end a new radiopharma­ceutical manufacturing laboratory in the Chemistry Annex was commissioned for the regular production of heart and kidney agents. This lab, together with the anticipated advent of the TRIUMF low-energy production facility in 1981, will provide the focus of attention for the coming year.P ositron  em iss ion  tom ography (PET)In I98O the TRIUMF Applied Program saw a new development in the form of the beginning of a program of positron emission tomography. Funding was obtained by UBC from the Provin­cial Government to provide the necessary chemical apparatus and supplies to equip the Chemistry Annex research laboratories for nuclear and organic chemistry operations, and to support the acquisition of a positron tomograph. In July an order was placed with Atomic Energy of Canada Ltd. for the Theras- can 312 8 camera, and this was scheduled for delivery to TRIUMF in February 1981.Three professional chemists were appointed to work at TRIUMF this year: two full-time nuclear and organic chemists and a part-time organic chemist, all to work on the develop­ment of positron-emitting radiopharmaceuti­cals.A gas target system was installed upstream of the TNF target, for the preparation of 18F and 150 by the irradiation of neon tar­get gas and the preparation of U C by the bombardment of oxygen. The target system proper consists of two gas target volumes en­closed by three double-foil helium window systems. The interior of the gas target volumes was bright nickelplated, to reduce the absorption of 18F activity on the target wall surfaces. The target was connected to the Chemistry Annex radioisotope research laboratories by multiple 300 ft long runs of stainless steel tubing of 2 mm internal d i ameter.The target system was commissioned with beam currents up to 100 yA. For 18F production the gas-filling was neon plus 1% F2 , the fluorine carrier being required to promote 18F recovery from the target. During the course of this year recoveries were variable, and of the order of 30% of the expected pro­duction. This was attributed to a number of factors in target operation, and at year's end these were being systematically explored. It was also demonstrated that a target mix­ture of neon plus oxygen carrier successful­ly produced 150 activity.Synthetic organic chemistry operations dur­ing this year were directed along two lines. First, attention was directed towards the synthesis of 2-f1uoro-2-deoxy-glucose, a glucose derivative used for the imaging of glucose metabolism in the brain by PET tech­niques in healthy subjects and in patients suffering from epilepsy, multiple sclerosis, psychiatric disorders, etc. The cold syn­thesis of this material was achieved by means of literature procedures, and this was followed by the first synthesis of the same material labelled with F activity. Some attention was paid to the shielding of the reaction vessels, and to the implementation of remote transfer techniques, in order to reduce laboratory personnel radiation exposures.A second direction for synthetic organic chemistry research was in the investigation of novel synthetic techniques for other potential positron-emitting radiopharmaceut­icals. As an example, the reactions of tin organo-metal1ic compounds were exploited for the rapid synthesis of fluro- and iodoben- zene, which when labelled with 18F or 120I activity are expected to be useful agents for imaging the distribution of myelin with­in the brain, and following the loss of60myelin in disease states such as multiple scleros i s .All of the foregoing work made extensive use of gas-chromatography and high-pressure- 1iquid-chromatography techniques. Some attention was paid this year to the imple­mentation of these techniques to the Chemistry Annex and to the development of the battery of other chemical instrumentation required for future synthetic operations.The TRIUMF PET group participated in the monthly deliberations of the UBC Pet Collab­orators Group, which were directed towards discussions of the PET technique and its implication in the study of a variety of brain disease states. Another facet of this activity was the development of a rather extensive PET bibliography which, towards year's end, was to be indexed on a word- processor system. On the basis of this understanding of the literature, planning was begun for a program of physics measurements on the tomograph following its arrival, and particularly the development of image-pro­cessing techniques.R adio iso tope p roduc tionAECL operations at TRIUMFThe 26 targets received from TRIUMF have mostly been used to develop chemical proces­sing and packaging techniques.22Na, 67Cu, 68Ge, 82Sr, 109Cd and 127Xehave been produced via 500 MeV proton spal­lation of AX,, Zn, As, Mo, In and Cs targets, respectively. Commercial shipments of 57Cu and 108Cd have started. 323i was produced in approximately 100 mCi batches 10-15 times via 70 MeV protons on a Nal target. Develop­ment of methodologies for 57Ga, ^ I n ,  i23i and 201T£ isotopes expected to be produced with the Cyclotron Corporation CP42 cyclo­tron have begun.Fac i1i t i esBeam line 2C. The feasibility of radioiso­tope production using a third extracted beam at TRIUMF was established this year with the successful operation of a 3 g cm-2 molten Nal generator target in the 70 MeV beam at exit port 2C. Twelve runs were completed with proton beam currents up to 4 yA, the largest single run yielding more than 0.6 Ci of 123I at extraction. Both the yield andpurity of the product were as expected from published data. Initial set-up time for this beam was of the order of one hour, but as the crew became more experienced only a few minutes were required. The chief problem was in learning to use a local magnetic field bump in Br to select the fraction taken from the other two simultaneous high-energy beams. Discrete energies 68, 70, 72, 85, 90 and 100 MeV were extracted during the course of the tests. In the last quarter the yields of 120I from the 127l(p,8n) reaction were measured at 70 and 100 MeV. Plans call for the interim Nal target to be decommissioned when the new multichannel, low-energy facili­ty comes on 1i ne.CP-42 cyclotron. The delivery of the Cyclo­tron Corporation's 42 MeV cyclotron has been delayed by about one year, due to an under­estimate of prototype development. However, there is steady progress and the various problems are being solved one after the other. The first beam was accelerated to 44 MeV in September. The maximum beam cui—  rent reached in December was 125 pA.In the meantime the secondary cooling system was delivered and installed. The primary cooling system with chiller has been in­stalled. Much of the cabling has been laid and the radiation monitoring and area access system is 80% complete. A start was made with the installation of rabbit tubes.500 MeV isotope production facility. Last year's annual report described the construc­tion of the 500 MeV isotope production facility. During the January shutdown the facility was installed at the thermal neutron facility, about 80 cm upstream of the lead target, and was ready to receive beam by the end of February. The facility is detailed in Figs. 60, 61 and 62.The first few months were used to commission the facility and to expose various targets to gradually increasing beam currents. At the end of the year the facility had been exposed to a total of 55,656 yAh. 40 radio­isotope targets had been irradiated, 26 of which were delivered to the AECL Commercial Products Radioisotope Group. The targets consisted of A£, Zn, In, Mo, Mo03, Zr02 ,As20 3, Y203 ar>8 CsC£. Only the CsCX, targets have so far given difficulty at higher beam currents, due to expansion of the CsC£.Chemistry Annex. The construction of the Radiochemistry Annex was substantially61T A R G E T  IN BE AMLINEFig, 60, The isotope production fa c i l i ty :  v e r tica l cross section  normal to beam line .CHAINDRIVE THERM O­C OU PLESPROTONBE A Mi f f fFig. 61. The 'in-heam' section o f  the isotope production thimble. Cross seotion normal to  proton beam ( l e f t )  and pa ra lle l to proton beam (r ig h t ).Fig. 62. The inside o f  the ta rget transfer hot c e l l  o f  the 500 MeV isotope production fa c i l i ty .  Note the ta rget holders ( l e f t ) ,  each holding two targets, the target storage rack (cen tre ), and lead container plug with target shelves ( r ig h t ) .62complete in January and was occupied immedi­ately. The elaborate ventilation and filter­ing system, which serves the numerous fume hoods and the four hot cel 1s , was commissioned early in the year and operates as expected. The cyclotron vault door, which moves on air pads, was commissioned successfully after the floor was accurately levelled with epoxy resin. The various groups that now occupy the ground and below-ground floors of this bu i1d i ng are:TRIUMF Applied Program GroupTRIUMF PET Chemistry GroupAECL Radiochemistry GroupThe top floor is office space occupied by TRIUMF experimenters.Interim isotope laboratory. This laboratory was used during 1980 for a variety of research operations. These included studies of the absorption of trace elements into human hairs by means of radiotracer tech­niques, chemical separations for Expt. 113, process development of isotope production by AECL (prior to the availability of the main Chemistry Annex facilities), and the produc­tion of 52Fe for pharmaceutical preparations by the TRIM Group.NovatrackThis was the first complete year of operation for Novatrack. The thermal neutron facility (TNF) at the end of beam line 1A proved to be very useful for the analysis of large numbers of geological samples. Almost all mining and exploration companies in BritishColumbia made use of the services provided by Novatrack. The determination of uranium by delayed neutron counting did not prove to be in high demand after the imposition of the moratorium on uranium mining by the B.C. government, but the dramatic increase in the price of gold did produce a very strong demand for gold analysis. At the peak of the season in August, 12 people were employed at Novatrack, and for a while more than 1000 gold samples a day were being analysed.Other elements that were analysed include arsenic, antimony, tantalum, cesium, thorium, tungsten and molybdenum. Trace elements were measured in concentrate materials. The accurate determination of rhenium in molyb­denum concentrates by neutron activation analysis proved also to be a valuable tool.Unfortunately, the delivery of a useful neutron flux in the TNF was compromised by the installation of the 500 MeV irradiation facility. This device affected the neutron flux to a much greater degree than had been predicted. Consequently, simultaneous use of the beam down beam line 1A, between the 500 MeV irradiation facility (AECL) and the TNF (Novatrack), was not possible. At present usage of the beam is shared evenly between Novatrack and AECL, but this does not help to improve the overall viability of Novatrack. Compounded with this TRIUMF ran into some serious operational problems in the latter half of the year. It is hoped the overall reliability of TRIUMF as a supplier of a medium-sized neutron flux will only improve as time goes on. The ultimate success of Novatrack certainly does still depend on this.63THEORETICAL PROGRAMIn tro d u c tio nThere has always been a commitment at TRIUMF to provide a core group of theoretical physi­cists who are actively involved in research in the areas of medium-energy nuclear and particle physics which are under experimental investigation at TRIUMF. The intention is then that such a group will provide both a centre for high quality theoretical research and resource people for the various experi­mental groups and that the laboratory program as a whole will benefit from the interaction between theorists and experimentalists. Generally such benefits are being realised, despite the fairly small size of the group relative to the large variety and number of experimental programs under way. The theorists have taken an active part in vari­ous activities of the laboratory and are in­volved in a number of research programs, some of which are detailed below.Currently there are three permanent staff in the group: H.W. Fearing, A.W. Thomas and R. Woloshyn. A fourth position has been approved and is currently being advertised. Research associates in the group, some of whom are supported jointly with UBC, include M. Betz, B. Blankleider (from November),J. Greben (to September), J. Niskanen (from September), J. Ng, A. Rosenthal (from September), A. Saharia (to September),0. Shanker (from September). Graduate stud­ents are M. Beaudry, G. Brookfield,J. Johnstone, P. Kalyniak, N. Shrimpton and S. Theberge. Two visitors to UBC, A. Gersten and G. Papini, have participated in group activities and in some of the projects listed below. Theoretical faculty and research associates at member universities have also been active participants including D. Beder,M. McMillan, E. Vogt, N. Weise (University of British Columbia), J. Greben (from September), A. Kamal, H. Sherif (University of Alberta),C. Picciotto, C. Wu (University of Victoria),D. Boal and M. Soroushian (Simon Fraser Un i vers i ty).During the year various members of the group have been involved in such efforts as plan­ning and carrying out a very successful work­shop on muon physics and possible new muon facilities at TRIUMF, in thinking about physics possible at a high intensity kaon factory in preparation for an eventual report on such an option for future development of TRIUMF, and planning for a workshop on suchphysics to be held in the summer of 19 81. Others are involved in the Canadian Associa­tion of Physicists study of research oppor­tunities in medium-energy physics. Several have also taught courses at UBC during the year and are supervising graduate students from the member universities.Members of the theory group have represented TRIUMF at a number of external meetings, including9th International Conference on the Few Body Problem, Eugene, Oregon International Conference on Nuclear Physics, Berkeley, California International Conference on Polarization Phenomena in Nuclear Reactions, Santa Fe, New MexicoAspen Institute for Physics, Aspen, Colorado SIN Workshop on Medium-Energy Physics,Arolla, Swi tzer1 and Gordon Conference on Photonuclear Inter­actionsGordon Conference on Nuclear Structure Conference on Nuclear Structure with Inter­mediate Energy Probes, Los Alamos, New Mexi coNeutrinos 80: International Conference on Neutrino Interactions SLAC Summer Institute on Particle Physics Grand Unification Workshop, Durham, New Hampsh i reAgain this year the group made its pilgrimage to Edmonton for discussions with the experi­mental group there. Regular weekly theory meetings have continued, providing opportuni­ties for informal presentation of work in progress. Organization of the regular TRIUMF seminar series has been another responsibil­ity and it, together with the theoretical visitor program, has made possible visits to TRIUMF of a number of theorists including R.D. Amado, N. Auerbach, F. Coester, L. Dodd, M. Fortes, M. Gyulassy, M. Harvey, R. Hwa,N. Isgur, K. Johnson, A.N. Kamal,K. Klingenbeck, S.E. Koonin, M. Krell,R. Landau, H.C. Lee, F. Lenz, G. Miller,T. Osborn, H. Pagels, L. Ray, A. Rinat,R. Shrock, R. Tegen, J.A. Tjon, M. Vassanji , J.D. Walecka, S.N. Yang and many others pass­ing through.Some specific areas and topics of research which have been of interest during the past year include the following:6A6  C  M .Fig. 63. The tensor po la riza tion t20 7I1^  *  ^  f ovTv = 140 MeV. Curves show the resu lt o f  a Faddeev ca lcu la tion  with no ? n  in te raction  ( . . . . )  and the e ffe c ts  o f  successively including P n  rescattering  (---- ) and then true pion absorption (---- ) .A un ita ry  m ode l o f the nNN systemThere has been a good deal of progress in the theoretical description of the ttNN system in the one-pion approximation. Various groups, using rather different approaches, have arrived at the same set of unitary equations for the coupled processes Trd -* ird, ird -*-»• NN and NN -+ NN [see for example, Afnan and Blankleider, Phys. Rev. C 22^ 1638 (1980)].Work has progressed on the numerical solution of these equations with particular attention paid to the effects of true pion absorption on n-d elastic scattering, and the adequacy of the model for the description of ird NN. The investigation has been in the 0-256 MeV pion laboratory kinetic energy region, and very encouraging results have been obtained. For ir-d elastic scattering the model gives reasonable agreement with experiment at all considered energies. However, perhaps the most notable predictions of the model for this reaction are: (i) The value of t20(180°) at 1 40 MeV (Fig. 63) - only the inclu­sion of both pion absorption and t t - N rescat­tering in the P ^  channel results in a value totally in agreement with the experiment of Holt e t  a t . (ii) The reproduction of the dip in the 256 MeV differential cross section (Fig. 64) - lowering of the dip is due to the inclusion of absorption in our model. The0  C MFig. 64. The d if fe re n tia l cross section fo r it-d  e la s tic  scattering at T^ = 256 MeV. Curves have the same notation as in  Fig. 63.results of our model regarding the effect of absorption on tt - d elastic scattering are strengthened by the especially successful description of the differential cross sec­tions for pp ■*-*■ ir+d . In Fig. 65 we show the the pp ■> T+d differential cross sections forc o s ' dFig. .65. The pp -*■ ir+d d if fe re n tia l cross sections f o r  energies up to  that o f  the resonance. These resu lts are generated from the same set o f  coupled equations that give the s o lid  curves in  Figs. 63 and 64.65energies up to that of the resonance. For energies above the resonance our cross sec­tions become progressively larger than exper­iment. This reflects our use of relativistic pion kinematics (RPK) in which the nucleons are treated non-re 1 ativistica11y . For the other coupled process, NN -* NN, our results are consistent with predictions of similar models that neglect the exchanges of the heavy mesons p, w, etc. Work is currently in progress at including these exchanges which are necessary for the correct descrip­tion of the nucleon-nuc1 eon force at short ranges.p  + p ■* d + n +A review of the basic reaction p + p •+ d + tt+ has been made with the stress on polariza­tion phenomena [Niskanen, invited talk at the 5th Int. Symp. on Polarization Phenomena in Nuclear Physics, Santa Fe]. The kinemat­ic simplicity of this reaction makes it the obvious first target for attempts to under­stand pion production and absorption reac­tions. Although the previous calculations gave a reasonable agreement with experiment for the cross section and asymmetry with a polarized beam o r target up to laboratory energies 600-700 MeV (without adjustable free parameters once NN scattering phase shifts were ensured), the later results from SIN with a polarized beam and target between 500 and 600 MeV have created a major discrepancy between theory and experiment (Fig. 66).Though the coupled channels model (COM) in co-ordinate space appears the most successful a qualitative discrepancy especially in the asymmetries Axx and Azz persists.This discrepancy has been surprisingly diffi­cult to overcome by modest variations in the COM, and proposals have been made to explain it away by contributions from so-called 'dibaryons', claimed to be seen in the NN scattering. However, it seems difficult to separate these 'dibaryons' from the NA inter­mediate state, which since the fifties has been assumed to dominate the reaction between kOO and 800 MeV. The most prominent 'di­baryons' appear exactly in the partial waves and energies where the NA is the most impor­tant, in 1D2 , 3^3 > 1Git. The work is in progress to obtain a boson-exchange interac­tion for the NA-system to see if any addi­tional 'dibaryon' contributions are necessary. The NA interaction might be important in 5S2 (NA) and P(NA) states.Fig. 66. Asymmetries (normalized by the unpolarized d iffe re n tia l eross sections) when the hecon and ta r­get are polarised in  the d irections z and x, y and y, etc. S o lid  lin e : CCM (Niskanen, Phys. L e tt. 79B, 190 (1978)); dashed lin e : three-body ca lcu la tion  (Rinat et a l . ,  p rep rin tJ; dotted lin e : 'dibaryon' f i t  (Kamo caid Watari, preprin t. A fte r correcting  some errors  in  ca lcu la tion  and om itting the 'non-resonant back­ground’ o f  the Nt these authors obtain a good f i t  in  la te r work. I t  should be noted that in  the CCM the NA gives a resonant con tr ib u tion .) Later the SIN data fo r  A h a v e  been corrected and show now a b ette r overa ll qua lita tive  agreement with the CCM than in  th is  figu re  (C. Lechanoine-Leluc, private  communication).With the development of experimental methods and facilities it has become obviously advantageous to use orthogonal functions in expansions of more and more detailed angular dependencies instead of the old cosG power expansion [Mandl and Regge, Phys. Rev. 39_, 1*78 (1955)]. We propose a new notation and show the kinematic structure of some of the most basic polarization observables in p + p - > d + u + in the hope to prevent an ex­plosion of different conventions as new data accumulate [Niskanen, contribution to the 5th Int. Symp. on Polarization Phenomena in Nuclear Physics, Santa Fe].66P henom eno log ica l H am ilton ian  fo r nucleons, p ions  and A isobars: NN sca tte ring  and p ion-deuteron  in te rac tionsThe A (1236) resonance in the pion-nucleon 33 channel is known to play a crucial role in pion-nucleus and nuc 1eon-nuc1eus reactions at intermediate energies. The importance of A degrees of freedom in the description of the ground state properties of nuclear matter and the structure of finite nuclei has been emphasized by many authors in recent years. For an investigation of these questions in the framework of quantum many- body theory, a Hamiltonian describing the interactions between nucleons, pions and A isobars is needed. Such a Hamiltonian has been constructed from the following inter­actions: (i) two-body interactions acting between two-baryon (NN and NA) states;(ii) two-body interactions between ttN states in all but the P33 channel; and (iii) a A Nit vertex. Relevant scattering equations for the processes N + N -> N + N, N + N-* tt +  d and i r  +  d - >  i t  +  d have been derived, in the 'one-pion' approximation. Simple (separable) parametrizations have been chosen for the interactions and the param­eters have been determined by fits to ttN and NN scattering data.The model thus constructed has been used to study various aspects of NN scattering, pionFig. 67. Phase s h if t  and in e la s tic ity  parameters fo rthe lD2 NN p a rtia l wave a) (---- ) f i t  obtained witha l l  in teractions included; b) (--- ) same as a) butno NN in te raction  in  intermediate NN-n states; c ) (••■■) same as b ), but no Nb pion exchange.Fig. 68. Total cross section fo r it ++d ■* p+p. See caption o f  Fig. 67.absorption on the deuteron, and pion-deuteron elastic scattering [Betz and Lee, Phys. Rev.C 23_, in press]. Multiple pion exchange between nucleon and A, as well as NN inter­actions in intermediate NNtt states, are expected to influence NN scattering at medium energy. These effects have been in­vestigated and turn out to be fairly impor­tant for the *D2 NN partial wave (see Fig. 67). The same interactions were also found to affect significantly the p + p -+■ tt+ + d reaction. As shown in Fig. 68, they enhance the cross section by roughly 30% in the resonance region [Betz and Lee, contrib­uted paper to the 9th Int. Conf. on the Few Body Problem], Another aspect of the NNir system of great current interest is the influence of the coupling to the NN channel ('true' pion absorption) on ird elastic scattering. Calculations based on the model described above show that back-angle differ­ential cross sections are affected by this coupling, but long-standing discrepancies between theory and data are not completely removed. Vector and tensor polarizations are also influenced by true absorption, though the effects predicted by the above model are not as large as those obtained using other approaches [Rinat e t  a l .  , Nucl. Phys. A329, 285 (1979); B 1ankleider, Ph.D. thesis, Flinders University of South Australia]. A more thorough investigation of the sensitivity of the results to the choice of parameters in each model seems ca 1 1ed for.67The pp -* p n n + reaction (p,y) and (p,n) reactionsThe model described above is being used to study the pp -* pmr+ reaction, under the assumption that pion production proceeds through the excitation and decay of a A iso­bar. This conjecture is supported by the 800 MeV data from LAMPF [Hudoma1j-Ga1itzsch e t  a l . , Phys. Rev. C _1_8, 2666 (1978)], which shows a bump corresponding to an invariant mass of the p7r+ system equal to the A reson­ance energy. For the purpose of comparison with other calculations [ i b i d .  and VerWest, Phys. Lett. 8 3B , 161 (1979)], it is desir­able to replace the separable baryon-baryon interactions by one-boson-exchange inter­actions. Calculations based on current OBE models [Holinde and Machleidt, Nucl . Phys. A280, A29 (1977)] with parameters fitted to low-energy NN phase shifts have been found to yield rather poor agreement with NN scat­tering data above the pion production threshold. A preliminary study of the pp -* pnTr+ reaction indicates that polariza­tion observables are very sensitive to ini­tial state interactions. Reliable calcula­tions therefore require an improvement of the model. A search on the parameters of the OBE model is under way, in order to achieve a satisfactory description of NN scattering. Once this is accomplished, one can hope that the pp -y pnir+ reaction with polarized beam and target will provide valuable information on the NN -> NA transi­tion amplitude, in particular concerning the role of p-meson exchange and the presence of dibaryon resonances.The A (p ,N n)A ' reactionOne of the motivations for constructing the model discussed above is the study of many- body reactions at medium energy. As an example, the A(p,Nit)A' reaction is under in­vestigation. Data for 9Be(p,Nir) 9Be [Expt. IA3 ] show no structure corresponding to an invariant mass of the Nit system equal to the A mass, as would be expected if the dominant mechanism is the excitation of the projectile to the isobar state. Crude calculations indicate that the data can be reconciled with this isobar model, provided the excita­tion of target nucleons to the A state is taken into account. Further work on this problem is under way.There has recently been a great deal of interest in reactions which involve high momentum transfer to the nucleus, of which (p,-rr) and (p,y) reactions are examples. It was suggested some time ago that a compari­son of a (p,y) reaction with the analogous (p,ir) reaction might provide useful insight into the mechanisms responsible. There will soon be results from a TRIUMF experi­ment (Expt. 131) on the reaction pd -> 3Hey which hopefully may resolve some of the dis­crepancies among earlier experiments and make possible such a comparison with the similar reaction pd -* tir.Thus an earlier calculation of the reaction pd ~y ttt in a distorted wave impulse approxi­mation model [Fearing, Phys. Rev. C J_6, 313 (1977)] has been generalized to allow a calculation of pd -»■ 3Hey. The ingredients of the model are essentially the same for both reactions, namely distortion in the initial and final (for the pion only) states, a form factor involving nuclear wave func­tions and an input two-nucleon cross section. However, the input cross sections, pn ■* dy for (p,y) and pp -* ird for (p,tt) are quite different, and the final state interaction is appropriate only in the pion case so a calculation of (p,y) should provide an inde­pendent and non-trivial test of the common ingredients of the model.Figure 69 shows some results in the model for pd -* 3Hey at 300 MeV. The two curves corre-6 7  (d e g )Fig. 69. Cross section fo r  pd 3#ey at 300 MeV ina DWIA model. The two curves correspond to two d i f ­fe ren t choices o f  the data fo r  the input pn -*■ dy cross section.68spond to two different selections of the pn -> dy cross-section data. It is immediate­ly obvious that the uncertainty in this cross section is a major source of uncertain­ty in the final results at this energy, though it becomes less important at higher energ i e s .Using the data of Dougan e t  a l . [Z. Phys. A280, 3^1 (1977)] corresponding to the upper curve, one finds that the results generally reproduce the angular distribution and near resonance also the absolute normalization of the newer data, in particular preliminary results of the TRIUMF experiment and those of Nefkens e t  a l .  [Phys. Rev. Lett. bS_, 168 (1980)].At somewhat higher energies the cross sec­tion apparently falls too rapidly with energy, which is the same effect as was seen in the analogous pd -* tw reaction. The presence of a similar discrepancy in both reactions tells one immediately that the effect is not due to interactions of the final state pion. Other possible explana­tions are neglect of the pny or, analogously, pnir intermediate states or difficulties with the approximations necessary to factor the two-body amplitude out of a loop integral, put it on shell and choose the kinematic point at which to evaluate it. These possi­bilities are being investigated further.Another related project, consuming a sub­stantial amount of time this past year, was the completion of a review of the whole area of (p,tt) reactions in nuclei [Fearing, Prog, in Particle and Nuclear Physics, to be published] and an accompanying bibliography of research on the subject [Fearing,TRI-80-3] •P roton-proton b rem sstrah lungProton-proton bremsstrahlung remains an interesting process with potential for giving information on the off-shell nucleon-nucleon interaction. This past year saw the essen­tial completion of soft photon analyses of existing experiments with the publishing of the final results of the TRIUMF experiment [Rogers e t  a l . , Phys. Rev. C 22^ , 2512 (1980)] and the analysis of the k l MeV Manitoba and 156 MeV Orsay experiments [Fearing, Phys.Rev. C 22_, 1388 (1980)]. The situation now for all medium-energy experiments seems to be that the purely on-shel1 soft photon approximation apparently fits the data as well as potential models.An obvious next step is to measure asymme­tries, and there is such an experiment being considered at TRIUMF. Theoretical analyses show major differences in the predictions obtained from a potential model calculation, a potential model calculation with modified off-shell behaviour, and a soft photon cal­culation. It has been shown, in an extension of these calculations, that the difference between soft photon and potential model calculations is in fact real and not due to differences in the elastic phases. Thus a soft photon calculation starting with phases derived from a potential differs from the full potential just as much as when empirical phases are used. Hence a measurement of the asymmetry should provide a real distinction among approaches.Finally, some efforts have begun to extend the soft photon approach into a model calcu­lation which contains the best features of the soft photon approach and at the same time allows contributions from off-shell as­pects of the interaction and direct compari­son with potential model approaches.Pion-nucleus in te ra c tio n s  in the isobar-doorw aym odelAn isobar-doorway model (IDM) has been developed for the ir-A optical potential. The treatment of nonlocality has been improved over that in the original IDM optical poten­tial [Kisslinger and Saharia, TRIUMF preprint TRI-PP-79-28]. Typical results for the differential cross section are shown in Fig. 70. The results of a first order opti­cal potential calculation are shown for compari son.During the past year our study of the (y,ir0) reaction has been completed [Saharia and Woloshyn, TRI-PP-80- 15]. Using our isobar­doorway framework we find a substantial correction to the distorted wave impulse approximation results, although not as large as that found by Koch and Moniz in the isobar-hole model [Phys. Rev. C 20, 235 (1979)]. The extension of the calculations to the reaction 1 3C (y ,tt") 1 3N (g . s .) is still under way.69ficm(deg)Fig. 70. A typ ica l f i t  to pion e la s tic  scattering  data fo r  160(-n'h, tt+J 1 6 0  at pion k in e tic  energy o f  114 MeV: dotted curve -  p red iction  o f  f ir s t -o rd e r  op tica l po ten tia l; so lid  curve -  channel-indepen­dent isobar-doorway model. The data are taken from Albanese e t a l. (Phys. Le tt. 73B, 119 (1978)).N uc lea r sizesThe analysis of the scattering of low-energy pions in terms of the nuclear size was dis­cussed at length in the 1979 Annual Report. We repeat that the two essential advantages of low-energy pions (c. 50 MeV) are their long mean free path (~5 fm in comparison with 0.5 fm in the (3,3) resonance region) and the tremendous selectivity of the p-wave pion-nucleon scattering amplitude (ir"n:iT p ~  10:1). A comprehensive review of the rela­tive advantages of all hadronic probes for measuring matter distributions was presented at the International Conference on Nuclear Physics at Berkeley in August [Thomas, Nucl. Physics A35^t, in press].More recently we have begun to examine the usefulness for future applications (e.g. at a kaon factory) of low-energy K+ beams in measuring nuclear properties. Prerequisite to the success of K+ in this role is (a) a good knowledge of the K+-nucleon scattering amplitudes, and (b) a sensitivity to the neutron distribution. In order to test the present situation on point (a), we [Krel1Fig. 71. Ratios o f  d if fe re n tia l cross sections fo r  160 to 180 and 200 MeV lab energy o f  the Pf. The s o lid  line  marked 'M artin ' represents the standard set o f  parameters; the so lid  lin e  marked 'Watts ' shows the same ra tio  but fo r  parameters from Watts instead o f  Martin. The dashed lin e  is  fo r  the standard parameter set o f  Martin, but has a decrease in  the neutron density radius o f  5% fo r 180.e t  a l . , submitted to Can. J. Phys.] used two alternate phase-shift analyses of Martin, and Watts, Astbury e t  a l . For point (b) we considered small changes in the size of the 180 and i+8Ca neutron densities (e.g. a 5% decrease). As shown in Fig. 71, there does seem to be an energy region where, even though the results calculated with the two sets of phase shifts differ, the effect of the change in size is much more significant. In fact, a meaningful experiment could probably be performed even now. (We show the ratio of the differential cross sections on 180/160, because this seemed to be far less model dependent in our pion scattering work.)Pion quas i-e lastic  sca tte ringLast year we described a proposal [Jackson e t  a l .  , Nucl. Phys. A322, A93 (1979)] to probe the behaviour of the pion-nucleon interaction in a nuclear medium using the (tt,ttN) reaction and a special 'fixed condi­tion geometry1. It has been shown (Shrimpton, M.Sc. thesis, to be published) by explicit evaluation of the appropriate distorted wave integral that— at least within the factorised DWIA— it does seem feasible to separate out the Pauli corrections (and per­haps other higher-order corrections) to the pion-nucleon interaction. The next year should see considerable progress on this problem as new data are being taken at both SIN and LAMPF.70P ion ic  co rrec tions  in  the M IT bag m ode lThe MIT bag model has provided a highly suc­cessful phenomenological description of the hadronic spectrum. It has been reviewed very well in a number of places, so for our present purposes it suffices to say that the model postulates a spherical confinement region, a bag, within which the quarks are absolutely confined, yet move freely. In order that four-momentum be conserved at the boundary of the confinement region the MIT group postulated that there be, inside the bag, a phenomeno1ogica1, positive energy density B that is equal to the Dirac pressure of the constituents at the bag boundary.In its simplest form, without even lowest order gluonic corrections and for massless up and down quarks, the bag model is de­scribed by the Lagrangian densityJB(x ) = q(x) V  q(x) - bJI 'B- j  q(x)q(x)<5s , (0where 9g is 1 inside and 0 outside the con­finement volume, and 6S is a surface delta function [S(r-R) for a static, spherical bag, with R the bag radius]. By demanding that the associated action be invariant under variations in q and q", and also under changes of the confinement volume normal to the surface, we get the three equations of the MIT model. The first is the free Dirac equation for massless quarks inside the bag. The second (linear boundary condition) en­sures that no colour flux leaves the bag, while the third is the previously mentioned pressure balance at the surface.One of the first outstanding successes of the model was the prediction that the axial vector coupling constant g^ has the value 1.09 for the nucleon. This is in remarkably good agreement with the experimental value of 1.24, and constitutes a significant im­provement on the non-relativistic quark model value of 5/3- However, there is still a problem, because the axial charge in the bag is not conserved, and the divergence of the axial vector current (SyAF) is not zero. Indeed 3yAy is quite large, in severe dis­agreement with our knowledge of the weak interaction. Formally this can be under­stood from Eq. (l) where the third term as­sociated with reflection at the bag boundary is seen to not be invariant under the global chiral transformation (by infinitesimal, constant isovector e)q q + 2 ~ '  ~y 5q ’q q" + y  qVcj • £ • (2)The TRIUMF-University of Washington group has constructed a theoretical model (similar to those of Jaffe, and Brown and collaborators), wherein chiral invariance is restored by introducing an explicit (massless) pion field Phys.(j;, in a minimal way [Miller e t  a l .  Rev. D 22, 2838 (1980)] :»CBM'0 = [jr qW  T  q- J  q"(x) e+ ( d^ ( x ))(x) - B^Og i t ‘$ ( x ) y 5/f (x) 6,(3)where f is the pion decay constant. (The subscript CBM is for cloudy bag model, which takes its name because the three-quark bag is surrounded by a cloud of pions.) The chiral transformation on the pion field is actually complicated and non-linear. For simplicity we shall retain only the linear terms in which case the conserved axial current isAF = q(x)yFy5 j  q(x)eB + f3y$ (4)Note that in this simple model, as in the work of Chodos and Thorn, the pion exists both inside and outside the bag. This allows one to quantise the pion field very easily, but a procedure for excluding the pion from the bag is being developed. It is easy to show that if we now break the chiral symme­try by explicitly adding a pion mass term to *Cc b m W  we obtain the usual PCAC relation- sh i p3mAF = f m l i  . (5)At first sight the theory presented here is indecently simple. The pion is treated as a structureless elementary particle. For example, at this level there is no fundamen­tal connection between chiral symmetry- breaking at the quark level (they get a mass) and PCAC [the introduction of the pion mass term in«CcBm (x )1• Nevertheless, this model seems to have powerful implications for our understanding of low and intermedi­ate energy nuclear physics.As a first example of a crucial problem in medium energy physics we consider the (3,3) resonance. In one part of the literature (typically Physical Review C) this is essen­tially a potential resonance generated by the graphs in Fig. 72(a). In the high71X w—C i /• N.( a )(b)AAAAJ----( OIIA A M VFig. 72. The so lid  lines represent nucleons, dashed ones pions and the curved line  the delta, (a) Chew-Low series, (b ) delta model, (a) p ion - baryon vertex functions.to the Low equation as discussed by Castillejo, Dalitz and Dyson. It is fasci­nating that whereas H0 5 HM |j + has two discrete (bag) states, the interacting Hamiltonian has only one— the nucleon. The other becomes an unstable resonance in the ttN system. A fit to the (3,3) scattering data using the CBM leads to a unique bag radius R ^ 0 . 8  fm, for which the graph of Fig. 7 2 (b) dominates. That is, if fnntt is set to zero (with all other parameters un­altered) the (3,3) resonance would move up by only 50 MeV, whereas if f ^ ^  was turned off there would be no resonance at all. This discussion of the nature of the A is a specific example of a very general problem of handling unstable particles in the quark model. In a rather different language, a very similar discussion of the A(l405) was recently presented by Dalitz e t  a l . [Oxford prepri nt 1980].energy physics literature (e.g. Physical Review D) it is a three quark state which decays ‘weakly1 into ttN, so that ttN scatter­ing is described by Fig. 72(b). These two pictures have never been reconciled before. But, if the pion field is in some sense small (so that the exponential can be ex­panded to first order in <{>) , the Lagrangian density of Eq. (3) leads to a HamiltonianhCBM = hMIT + h t7 + H int • (6)Here H^|j and H^ describe a free MIT bag anda free pion field, respectively. The inter­action term describes the coupling of the pion field to a qcf pair at the surface of the bag. If the bag states are restrictedto N and A only, then H|nt contains the ver­tices shown in Fig. 72(c). However, now the coupling constants are all related (e.g.^ANtt = /72?25 f N[sjtt) , and the cut-off (or vertex) function u(k)— calculated in terms of the quark wave functions at the bag sur­face— is the same in each caseu(k) = j0 (kR) + j2 (kR) = ■ (7)kRTherefore, one cannot arbitrarily increase the strength of the graphs in Fig. 72 (a) by increasing the momentum cut-off without also increasing the strength of Fig. 72(b). (Note that there will also be interference terms in thi s model.)This model is an explicit, physically well motivated example of an alternate solutionOnly preliminary work has yet been carried out to re-do hadronic spectroscopy in this hybrid model, but the first indications are that there will be little trouble. In fact, one interesting result already in hand is the fact that the pion self-energy is a little more attractive for the nucleon (— 400 MeV) than the delta (— 340 MeV). Thus, the mag­netic q-q interaction needs to give only some 240 MeV splitting between N and A in this model (instead of the entire amount 293 MeV, as in DeGrand e t  a l . )  . With the 1 5-20% smaller radius (0.8 fm cf. [0.95-1.0) fm] and the idea that the splitting is pro­portional to ac/R this means the colour coup­ling constant ac should be O .36 rather than 0.55 as in the earlier MIT work. The smaller number is considerably easier to reconcile with recent very high energy data— although the uncertainty in defining an appropriate momentum transfer in the bag model makes quantitative comparison impossible at the present time. A smaller value of ac is also more consistent with the perturbative treat­ment of the q-q interaction.The pionic corrections to the bag's electro­magnetic properties can also be calculated to lowest order (such a procedure is valid only for a reasonably large value of R).For the cloudy bag model the results for the nucleon electromagnetic properties are sum­marised in Table XIV. Similar results have been obtained recently by deTar. In every case except <r2>*/2 where there is little effect, the correction improves the agree­ment with experiment significantly. Note also that our value of g^ is in good agree­ment with the experimental one.72Table XIV. The mean square charge radius of the proton (neutron) is <r2>p (<r2>n) . The nucleon magnetic moments (yp,pn) are given in units of nuclear magnetons.<r z > y * A “1 V D i—yp Rn 9ACBM (R = 0.8) 0.71 -0.36 2.60 -2.01 1.19Exper i ment 0.83 -0. 3A 2.79 -1.91 1 .2LMIT (R = 1.0) 0.73 0.0 1.9 -1.2 1.09The agreement with the neutron electric form factor GEn(q2) is extremely significant.Just as in all the old static source theories the process n ■* pir- gave rise to a negative tail for the intrinsic neutron charge dis­tribution, so does the CBH. Those prehis­toric models had, however, two basic prob­lems. First, the core was not understood, and its properties were incalculable. Secondly, the interpretation of GEn(q2) was always clouded by the presence of the Darwin- Foldy term, whereby a Dirac particle with an anomalous magnetic moment appears, because of zitterbewegung to have an intrin­sic charge distribution. Indeed pn exlains essentially all of the value of <r2>n measured experimentally.In the quark model the photon interacts not with a Dirac nucleon but with three con­fined quarks (and the pion in the CBM) and there is no Darwin-Foldy term. Thus the interpretation of G£n (q2) in terms of an in­trinsic charge distribution is unambiguous in this model, and the agreement with <r2>n is very significant. Further, if we take seriously the phenomenological fits of p^(1(r) to the admittedly very poor data for GEn(q2) , we see that they tend to give the zero in pQh(r) (where it switches from posi­tive to negative) at about 0.8 fm (with at least twenty per cent uncertainty either bigger or smaller). In the cloudy bag model the pion field is a maximum at the surface of the bag and this switch in sign should occur very close to R, the bag radius. The qualitative agreement between the experimen­tal value quoted above (~0.8 fm) and the value of 0.8 fm extracted from ttN scattering is at the very least a remarkable coinci­dence. Better data for GEn(q2) would be extremely valuable.One final result which we must mention is the recent proof [Dodd e t  a l .  ] that pertur­bation theory is much more rapidly conver­gent in the cloudy bag model than in earlier pion-nuclear field theories— such as Chew-Low. In particular, we have proven a rigorous upper bound on the probability of finding n-pions around the physical nucleon, Pn - An/n! For the CBM A ~  0.9, whereas in the Chew-Low model A ~  2.2. We leave it as an exercise for the reader to check the im­provement in convergence. This is perhaps made clearer through the upper bounds on the average number of pions about the nucleon— 0.9 ± 1.0 for the CBM, in compari­son with 2.16 ± 2.22 for Chew-Low!Not only do our results give great support to the perturbative approach to single baryon properties, but one may hope for new insight in several other areas. For example, one might now expect to make progress in the understanding of the long and intermediate range N-N force using similar techniques.We might also mention the proposed tests of the various grand unified theories. In particular, there are many experiments under way which look for proton decay modes, such as p +  e+ir°. With few exceptions, the as­sumption is usually made that the nucleon consists of just three quarks, two of which annihilate to an antiquark and a lepton.If the dressed nucleon actually had a cloud of pions like that in the Chew-Low model, the theoretical predictions based on the three-quark picture would be quite unreli­able, because of the dominance of multipion decay modes. However, within the CBM our bounds strongly suggest that decays to a lepton and one or two pions will dominate.The sigm a m ode l in a bagThe relationship between chiral symmetry and quark bag theories, the two outstanding theoretical tools used in low energy hadron physics, has yet to be clarified. Present models weld the two together in an ad  hoc  manner, and despite their other successes they do not account for the fundamental feature of the Nambu-Goldstone realization of broken SU(2) x SU(2) . This feature is required to understand the low pion mass and PCAC. In studying this problem it was noticed that the most natural bagged version of the linear a-model, with explicit chiral symmetry-breaking restricted to the bag exterior, has a symmetry-violating potential energy which contributes a term to the bag constant B ~  f2 M2/2 «  20 MeV/F3. This number has the same sign and order of magni­tude as the MIT bag constant and is motiva­tion for further work on models with a space­time dependent vacuum structure.73Proton p ro d u c tio n  in  s trong  and e lec trom agne ticin te rac tionsA direct knockout model for inclusive proton production proposed some years ago [Amado and Woloshyn, Phys. Rev. Lett. j[6, 1^35 (1976)] was modified to take into account the fact that the residual system (after proton knockout) does not recoil coherently.Central to this knockout model is the struc­ture function (or momentum distribution, in PWIA language) of the struck nucleon. Determining this from an analysis of the (p,p') reaction data, we performed a param­eter-free calculation of the (y,p) reaction with intermediate energy bremsstrahlung photons [Boal and Woloshyn, Phys. Rev. C 23^(in press)]. The agreement with the data was at least as good as quasideuteron model calculations at bremsstrah 1ung end-point energies in excess of 500 MeV.This direct knockout model can also be tested by measuring the (p,2p) reaction [Boal, Phys. Rev. C 2\_, 1913 (1980)]. Preliminary results from a recent experiment at TRIUMF with 300 MeV incident protons are in reason­able agreement with the knockout model described above, but sharp disagreement with a knockout model having a coherently recoil­ing residual system. Predictions of this model for charged particle multiplicities associated with a wide angle proton trigger have also been made.Lastly, calculations using the direct knock­out approach were made for the LfHe(p,p')X reaction at 500 MeV using parameters determined from higher energy and heavier target experiments. Again, agreement with the data was good [Roy e t  a l .  , Phys. Rev.C (i n press) ].P roton-induced fragm en ta tion  reactionsSeveral models have been proposed for the emission of light fragments, ranging from statistical 'evaporation1 models to direct knockout of a preformed cluster. On the basis of an analysis of electron-induced fragment emission, and of the parameters of the statistical and preformed cluster models, we have concluded [Boal e t  a l .  , TRIUMF pre­print TRI-PP-80-28] that the most likely mechanism involves the projectile undergoing a single scattering to produce an energetic nucleon, which then 'accumulates' other nucleons to form the observed fragment. This has been dubbed the 'snowball' model.The parameters of this model are determined by analysis of light fragments emitted at fixed energy and angle. The parameters are determined to be (for light fragments):Fermi momentum of the fragment of ~180 MeV/c [compared to ~ 1 70 MeV/c determined from sLi(e,e')X] and an average distance from the nucleon surface of 3 F for fragment forma­tion. The target mass number and fragment energy and angle dependence seem to be well described by the model. Comparison has also been made with mixed success for the (e,a) reaction, and predictions have been made for other (e,fragment) reactions [Boal and Soroushian, TRIUMF preprint TRI-PP—8 I-7] - Work is continuing on light ion-induced frag­mentation reactions.M any-body phys icsIn collaboration with A.D. Jackson and S.-0. Backman a formalism was developed to calcu­late the so-called 'induced interaction' contribution to the particle-hole interac­tion in nuclear matter. This contribution arises in a medium through excitation of particle-hole pairs which, in part, propa­gate the interaction [Fig. 73(c)]. The results were very much simplified by the discovery that the input, Brueckner's reac­tion matrix [Fig. 73(a,b)] calculated fromAV S ' /F ig . 75the Reid soft core potential, was local with a surprising accuracy in the sense that in the expansion 3"(k,g) = + ^ e W  ttletwo terms were dependent only on one momen­tum variable. Here d and e refer to the direct and exchange parts [Figs. 73(a), (b) , respectively] of the interaction and k and g are the momentum transfers in the respec­tive channels. By locality the solution of the otherwise complicated set of integral equations reduces to geometric sums. The simplicity of the result now makes it pos­sible to calculate the two-phonon-exchange processes [Fig. 73(d,e)] when one-phonon ex­change is considered to be the sum of the first-order interaction and the induced interaction. The results indicate large repulsive contributions from both the7^induced part and the two-phonon exchange [Fig. 73(d)] in the spin-isospin independent part of the particle-hole interaction bring­ing the compression modulus K from about zero to about 150 MeV as compared with the experi­mental value of about 200 MeV. More repulsion would be expected from the full multiphonon exchange series. The tensor parts are de­creased by the induced interaction by a factor of 1/3 - 1/2, but unfortunately the symmetry energy 3 remains very much the same,~20 MeV, through the calculation as compared to the experimental value, ~30 MeV. It would be very interesting to see the effect of explicit inclusion of NA excitations on the sea 1 ar-isovector part of the interaction.An application of the above formalism to neutron matter and neutron star cooling was carried out in collaboration with J.A. Sauls and R.A. Smith. Due to the repulsive effect of the induced interaction we find it much more difficult to generate the BCS gap for superfluidity. The logical conclusion is that, because superfluidity is not suppress­ing processes n -+ p + e_ + v and p + e- -> n + v, neutron stars should have a much higher neutrino emissivity than expected from superfluid matter. Consequently, the cooling rate could be higher without the necessity to introduce more exotic effects like the phase of pion condensation.Z N  in te rac tionsOne-boson-exchange models of ZN interactions have been studied in preparation for a full investigation of Z-hypernuclei. The simplest channel is T = 3/2 where the strong decay ZN AN is isospin forbidden and in which there is the outstanding problem of a pos­sible Z”n bound state. Standard analyses proceed by fitting meson coupling constants to NN and the small amount of AN data, a pro­cedure which involves a large number of free parameters. This analysis has used the OBEP with recent parameters derived from meson- baryon scattering, an independent source of information. The couplings are in many cases quite different from the fitted values. At low energies all Z-n channels are found to be repulsive except for the 1Sq whose depth depends strongly on 0+ meson exchange. Two models have been considered:A) A single 0+ nonet with masses at theParticle Data values. There are two free parameters, the eNN coupling and the F/D ratio. The former is fixed in fits to S-wave NN scattering and the latter has been varied to the ZN data.B) A pair of 0+ nonets, one (called 0|) at ~800 MeV including the S* and 6 and another (0+) at ~1400 MeV including the e and k , as suggested by bag models.There are five free parameters: ejNN, kjNN, E2NN and the two F/D ratios.With model B one can fit the low energy data in more than one way and predictions are meaningless. In model A, however, adequate ' fits to data are possible only in a very restricted parameter range. None of these fits allows a bound Z“n, and they all pre­dict a strongly repulsive 3Sj channel so that such a model is unlikely to bind the Z-nn system. These results lead us to ex­pect that for even the 1ightest Z-hypernuclei one will be concerned with the full compli­cations of a coupled channel problem. This problem will be addressed in the coming months using tfie T = 1/2 potentials predicted by the above models.1-hypernucie iOne of the most fascinating nuclear physics possibilities at a kaon factory is the ability to make and study hypernuclei. The recent discovery of two unexpectedly narrow Z-hypernuclei has made this field even more exciting. Attempts are being made to calcu­late the properties of these exotic nuclei from a microscopic theory. Separable Z-N potentials (including the coupled inelastic A-N channel) have been fitted to available two-body data. The use of these somewhat simplified two-body interactions permits a much simpler treatment of the many-body problem. Initial results concerning the effective Z-N scattering length for use in the calculation of Z-atomic levels were very promi s i ng.B o u n d p decayAn important background for the p e con­version experiment now under way at TRIUMF is the ordinary decay of a muon bound in a nucleus. Under these circumstances the nucleus can absorb the necessary momentum so that a high-energy electron can be emitted. Thus it is necessary to calculate the spec­trum of such electrons carefully. Previous calculations have considered recoil effects only in the phase space. Although these are the most important corrections, recoil effects in the matrix element are of the same order and should be included for a completely consistent calculation. We are attempting to include all such recoil effects using the effective potential75approach of Grotch and Yennie [Rev. Mod.Phys. k]_, 350 (1969)]- So far an effective potential has been derived and appropriately generalized to the case of finite nuclei. A separation of variables and formal solution has been obtained and the appropriate trans­formations from the y-nucleus to e-nucleus frame worked out. Unlike the non-relativis- tic case these later steps are non-trivial when one works consistently to first order in the nuclear recoil or equiva1ent1y v/c.The matrix element and phase space have been worked out in general, leading to general expressions for both the electron spectrum and asymmetry. So far these expressions have been evaluated numerically only in the very simplest case, namely plane wave elec­tron and point charge muon wave function.In this (unrealistic) situation the recoil effects other than phase space are small.The more realistic case, where both electron and muon wave functions are obtained from the full effective potential for a finite nucleus, remains to be examined.In a separate but related investigation the spectrum of high-energy electrons from bound muon decay was studied from the point of view of seeing whether the spectrum is sensi­tive to deviations of the weak interaction parameters from their standard values, and if so, what effect the deviations would have on the interpretation of the y -* e conversion experiment. It was found that the bound muon decay spectrum is not very sensitive to the presence of scalar, pseudoscalar, tensor or (V+A) currents. This is because the high- energy spectrum is determined by the p parameter of the Michel spectrum from free muon decay, which is very well measured.Also, a possible non-zero mass for the neutrinos (including the possibility of neutrino mixing) changes the spectrum shape in a simple and wel1-determined way. The spectrum is depleted at the high-energy end because of non-zero neutrino masses, and. hence does not confuse the interpretation of the y -> e conversion experiment. Thus, deviations of the weak interaction parameters from their standard values do not cause problems in calculating the bound muon decay background. It was also found that the nuclear charge distribution, which affects the background calculation, was known to sufficient accuracy. It was shown that previous calculations of the high-energy bound muon decay electron spectrum could be understood in a simple manner when use is made of certain (Wronskian) relations which follow from the Dirac equation.H orizon ta l gauge m ode lsOne of the interesting questions left un­answered in present theories of particle physics is the reason for existence of gen­erations, e.g., the electron family, the muon family, etc. One appealing idea is that the generations are members of a multi- plet of a local gauge group, often called the horizontal gauge group. While this is as yet only a speculation, many authors have studied this possibility. Horizontal gauge bosons are also necessary in extended tech- nicolour (ETC) theories. At TRIUMF the phenomenology of horizontal gauge models incorporating a natural flavour change sup­pression mechanism was studied. These models can have muon-number-violating rates comparable to present experimental limits. This is to be contrasted with_horizontal gauge models in which the K°-K° transition is not suppressed. Another interesting consequence of the suppression mechanism is that in some cases it requires CP violation to occur due to the exchange of horizontal gauge bosons. This is similar to the super- weak model of CP violation first introduced by Lincoln Wolfenstein. However, unlike in usual superweak models, the neutron dipole moment in some of the models studied at TRIUMF is predicted to be of order 10-27—  10-26 e-cm, not far below present experimen­tal limits. This is because of the flavour change suppression mechanism that is incorporated in the models.H ydrogen recom b ina tion  a t 1°KDense atomic hydrogen at low temperature would constitute an essentially perfect Bose gas, if it were stable. Recent experiments [Physics Today, June (1980), p . 18] have been fairly successful in attaining a relatively high density for some time. However, hydro­gen recombination seems to be a limiting problem. In order to understand this limi­tation it is necessary to study the process of hydrogen recombination at low tempera­tures— i.e. where no metastable state H2" is available as an intermediate stage.A recent UBC experiment found a recombina- for atomic hydrogen in He at l°K of 28 x lO-34 cme/sec. We h ave investigated the true three-body reactionH + H + He + H2 + He (l)as the o n ly  available mechanism. After a careful calculation including the off-shell76behaviour of the H-He t-matrix, and thermal averaging (which is crucial!), we found a rate of 21 x 10-34 cm6/sec [Greben e t  a l . , TRIUMF preprint (1981)] in impulse approxi­mation. This remarkable agreement has very important implications for the recombinationmechanism, since the formation of ortho-H2 seems to give about 90% of the total rate. Thus we can make some definite predictions for the temperature and magnetic field dependence of the recombination rate.77BEAM RESEARCH AND DEVELOPMENTINTRODUCTIONOn the experimental side this has been a year mainly of consolidation on past achieve­ments; on the design side, however, a number of new ideas have arisen which promise well for the future, particularly for the proton lines and secondary channels.In the cyclotron the beam intensity has been steadily pushed up to a record 170 yA (1015 p/sec) by improvements in the ISIS front end (see Cyclotron Development, p. 7)• Moreover, with more accurate measurement of the quadrupole voltages and of the emittance shape it has been possible for the first time to understand and improve the operation­al tune of ISIS at high intensity. At the other end of the scale some experiments have demanded very low intensities for in-beam counters— in one case as little as 103 p/sec, stable over many hours, obtained by detuning techniques. In the interest of reducing internal beam losses further studies have been made of the gas and electromagnetic stripping processes for H~ ions. Medium energy resolution beams (AE/E < 10~3) have been routinely set up for users with inten­sities of up to 9 yA. The successful use of a ‘picket fence1 extraction foil was demon­strated; this enabled a A00 keV wide beam to be extracted down beam line AA without the the use of internal slits while an intense normal resolution beam was provided to beam line 1A (Fig. 7A) .Another novel extraction foil— this time with two fingers— appears as if it may pro­vide a neat way of producing two beams in the same line with sufficient separation at a waist for magnetic splitting (1A/1C). The front end design of the third high energy line (2A) has now been completed. For BLABFig. 74. Beam line layout:  protons, •••• pions/muons, ----  proposed.operation with the MRS in energy-loss mode a five-quadrupole twister has been designed to rotate the dispersion from horizontal to vertical. On the practical side BLAC has been successfully commissioned and used to provide polarized beams of 105 p/sec simul­taneously with beams 108 times more intense in BL1B.Extensive measurements have been made of the pion and muon fluxes and contaminations in the various secondary channels. Factors studied included target material, spot shape and proton energy. Improvements have been proposed to the M 8 , Ml 3 and M20 channels. For M8 the addition of a permanent quadrupole magnet near the production target is pre­dicted to double the i t "  intensity. For M 1 3  a short dc separator would clean up the sur­face muon beam. The M20 redesign will permit the simultaneous use of forward and backward muon beams in the two legs; a clean forward muon beam could also be obtained in the 37-5° leg. In addition a superconducting solenoid channel has been studied as a high flux source of polarized muons. Finally the 'Discovery' pion spectrometer design has been comp 1eted.CYCLOTRONISIS beam op ticsProgress has been made toward understanding the beam behaviour along the 300 keV injec­tion line, which is AO m long and contains two 90° bends and a total of 79 quadrupoles—  all electrostatic. The beam behaviour has been calculated using the computer program SPEAM. This program includes the transverse space charge effect by numerically solving the Kapchinsky-V1 adimirsky equations. The initial emittance figures (6 tt mm-mrad hori­zontally and A. 5 tt mm-mrad vertically at 300 keV) were derived by measuring the beam size at four locations at the beginning of the unpolarized line. Given the operational voltage values, it is now in general possible to calculate a beam envelope up to the chopper slit which meets all of the existing constraints (a series of 13 mm x 13 mm col­limators and the chopper and 1:5 selector slits— see Fig. 75- To achieve this agree­ment, the electrostatic voltages had to be78Fig. 75. Beam envelope in  the in je c tio n  line  calculated from fou r beam p ro f ile  measurements (v e r t ic a l arrows).measured to an accuracy of better than 1%. Calibration of the quadrupole power supplies has also enabled a number of dispersion 1 ess tunes for the horizontal bend section to be ver i f i e d .An effort is being made to reduce those effects which tend to misalign the beam with respect to the beam line axis. These include the residual stray magnetic field and geo­metrical alignment errors. At present, these effects prevent the implementation of the optimum non-dispersive solution contemplated i n the or i g i na1 des i gn .M edium  energy reso lu tionThe slit-selected beam described in last year's annual report has been used by experi­menters and a detailed instruction manual has been written to aid the Operations group. The maximum current through the slits with energy spread AE/E £ 10-3 has been 9-5 yA at 500 MeV. The emittance of the beam leaving the central region of the cyclotron is dif­ferent at high currents so one must start by setting the slits about a pulsed beam that, at 100% duty factor, would give more than 100 yA. The computer program mentioned last year that predicts first harmonic coil set­tings to centre the beam to a precision equivalent to 0.02G first harmonic now works well. Initially there were problems with slight irregularities in the probe-chart recorder system that caused spurious varia­tions in turn spacing. This was apparent once the turn spacing was plotted as a function of radius.A special 'picket fence' extraction foil (Fig. 76) has been mounted on the beam line IA mechanism. The foil was made up of 7 carbon strips about 0 .0 3 in. wide separated by 0.01 in. Since v r is close to 1.5 the emergent beam has undergone selection in the main in only one orientation in x-px space; however, RF phase selection will have taken place and a narrow extraction foil inbeam line A will provide further selection depending on its location. The aim is to deliver a high current to beam line IA while providing improved resolution to beam line A at energies above that run in IA. We obtained about A00 keV resolution at 506 MeV on beam line 4B while delivering 30 yA to beam line IA with about twice the normal losses; however, the spills were not opt i m ized.We also have a pneumatically operated picket fence in the vicinity of 195 MeV; this per­forms a more complete selection in horizontal phase space since v r is close to 1.25. The beam incident on the 'fence posts' is not extractable and is consequently limited to about 1 yA. It is possible to further define the beam by shadowing the extraction foil by a probe at an appropriate azimuth; any other user must be operating at a lower energy. Figure 77 shows a spectrum produced from 208Pb by a beam passing through the picket fence and extracted at 200 MeV, the foil being shadowed by a probe on the opposite side of the machine. The FWHM of 108 keV includes instrumental resolution, but not the broadening that would be induced by wire chambers that many experiments require to be placed at the spectrometer entrance.I I I I IcmFig. 76. Picket fence f o i l  used at 500 MeV, with seven carbon s trips  0.030 in . wide.79Beam loss by e lec trom agne tic  s tr ip p in g°PbTp = 200 MeV=  2 1 'groundstate-108 keVVj _ L ..2.615 MeVFig. 77. Spectrum o f  200 MeV MEW protons extracted  with a p icket fence f o i l  and scattered from 20BPb, using the MRS (courtesy o f  Univ. o f  Alberta group).Beam loss by gas s tr ip p in gA renewed investigation of gas stripping is under way to determine its contribution to the total residual radiation in the cyclo­tron vault. Measurements of gas stripping have shown a current loss of ~1 4% for an air equivalent pressure (a.e.p.) of 1 x 10-7 Torr, which is in agreement with previous theoretical calculations. Thus the best a.e.p. in the past six months, 4.3 x 10-8 Torr, is responsible for a current loss of or 2.2% power loss. At this pressure H2 accounts for ~60% of the loss. A new liquid helium cryopump still in the testing stages was found to decrease the H2 partial pressure by a factor of 3; this could con­ceivably reduce the a.e.p. to 2.7 x lo-8 Torr and a current loss of ~ 3 . IX or ~1.3% power loss. The above power loss values can be compared with the power losses from electro­magnetic dissociation, ~9% to 500 MeV and ~1.6% to 450 MeV, and from beam dynamics, ~1.5%. Assuming an a.e.p. of 2.7 x ]0-8 Torr a reduction in tank activation of ~2 should be achievable by extracting at 450 MeV as opposed to 500 MeV, while still maintaining a constant ir- flux in M8. Further work on this problem will involve measuring the gas stripping and tank pressure more accurately in order to determine safe upper limits on the pressure for a given extraction energy and beam current.We know from transmission measurements that the beam loss due to electromagnetic strip­ping is close to that calculated by our orbit codes using cross sections previously measured [Stinson e t  a l .  , Nucl. Instrum. Methods 7j4, 333, 1969]- Those measurements were made in the same _vxB_ regime under which TRIUMF operates but at 50 MeV. An accurate confirmation of the gas and electromagnetic loss would be useful in determining operat­ing modes at high current; however, it is difficult to determine from the difference between two similar beam currents in a transmission measurement. In addition the electron capture efficiency of the beam current probe is not 100% and varies with energy.It was therefore decided to measure the loss directly using secondary emission detectors placed in the vacuum tank between the outer­most orbits and the tank wall. Stripped neutral atoms leave their orbits tangential- ly and each detector intercepts those atoms arising within a narrow azimuthal band ex­tending from the highest energies downwards, Fig. 78. One detector was placed to sample gas and electromagnetically stripped atoms arising in a hill, the other gas stripped atoms from a valley. Activation foil measurements [Craddock e t  a l .  . IEEE Trans. NS-24, #3, 1615 (1977)] have confirmed our  M EASUR EM ENT (H °) C A LIBR A TIO N  (H +)5 3 54 0 03 0 0200Fig. 78. Location o f  the two stripp ing  detectors with some examples o f  H° and H+ tra je c to r ie s .DETECTOR 280predictions of the azimuthal distribution at the tank wall of the gas and electromagnet!- cally stripped atoms.A multi-plate secondary emission detector was chosen over a device that would strip and collect the electrons from neutral atoms, partly because it is easier to shield from stray RF fields and partly because it could be calibrated directly with protons stripped by a beam probe or extraction foil (Fig. 78). Calibrations performed at the two higher energies of 250 and 4SO MeV scaled by dE/dx, as expected (Mackenzie, IEEE Trans NS-26, § 2 , 2312 (1979)]. The detector acceptance varies in a trapezoidal fashion with azimuth and is roughly 3° wide; the acceptance was calcu­lated as a function of energy.A detector gives a signal corresponding to the loss integrated over its arc of accept­ance from the lowest energy to the maximum beam energy (which may be determined by the radial position of a probe). Moving the probe to a higher energy gives an increase in detector signal corresponding to the loss occurring between the two energies. The ad­ditional loss arising from a valley is small whilst that from a hill increases dramatical­ly. To predict the losses for comparison with the observed results it is necessary to know the number of turns made per unit energy interval. This is obtained directly from the rate of change in the flight time from a macro-pulser in the injection line to a time pick-off on the beam probe as the probe radius is altered.Figure 79 shows the measured electromagnetic loss; it compares well with the expected loss based on numerical integration of the formula for the dependence of H” lifetime t on energy Ex = (A/E) exp(B/E) ,with the constants A = 2.82 x 1CT14 s-MV/cm and B = bk . JO MV/cm obtained from Scherk's theoretical lifetime values [Can. J. Phys.57, 558 (1979)]— themselves in agreement with Stinson e t  a l . ' s  measurements. The error bars include uncertainties in the energy gain/turn, the energy defined by the probe and the location of the detectors.CUMULATIVE ELECTROMAGNETIC STRIPPING LOSSFig. 79. Cumulative electromagnetic stripp ing loss as a function o f  energy.PRIMARY BEAM LINESBeam line  1AIn order to feed a new pion production target for a high flux biomedical pion channel interest has arisen in producing a beam spot in beam line IA made up of two spatially separated components; a septum could then be inserted to deflect the components into different beam lines. One way to do this would be to use an extraction foil divided into two parts and form an image of the foil at the septum, Fig. 80(a). The overall beam envelope produced by such a two-part foil would be much larger than from a normal C foil. However, Monte Carlo calculations indicate that it would be possible to use an extractor with a 0 .2 5 in. space between the foils and transport the resulting double beam through the existing k in. diameter beam pipe to a focus at IATI [Fig. 80(b)]. The beam loss would be less than l/lO4 including scattering effects. Experimental tests are planned using a profile monitor which should be able to resolve the expected separation of 2 mm at IATI. A double beam spot would make it particularly easy to set up focus-to-focus conditions between IATI and 1AT2. Studies are also under way to see whether a double beam spot could be produced well upstream of I AT 1, where the separation could be much larger.Various improvements have been made in the regular operation of beam line IA. One dif­ficulty has been 1.5 mrad deflection caused by the remanent field (~40 G) of the 1BVB2 dipole magnet which switches beam between lines IA and IB. With the help of a trickle power supply and Hall probe the field can now be readily kept below 5 G, resulting in much simpler horizontal steering. The effect of the Mil septum magnet on beam line IA has81FRAMETTTTTOOTHFOILSTOPPING FOILI I I I 1SCALE (cm)Y(CM) REVMOC OF "F0ILBEAM 2" TO T1 WITH TUNE 1A500NEWBX(CM)Fig. 80. a) Stripping f o i l  fo r  double beam extraction , b) sca tte r p lo t and horizontal p ro jection  o f  the doidole beam spot calculated fo r  1AT1.also been checked; it was found to mis-steer the beam at 1AM10 by mm, but had no measurable effect on spill. Studies are under way to see if it is possible to make the beam line less sensitive to operational deviations. For instance, a 1 mm lateral shift in the beam spots at the production targets 1AT1 and 1AT2 can lead to shifts of more than 2 cm elsewhere. The situation can be improved somewhat by relocating the steer­ing magnets. Studies were completed to check the effects of proposed vault changes; un­fortunately they were found to have a detri­mental effect on the optics and operation of the beam line. The proposed new tune BL1A500N has been modified to reduce beam spills in 1AQ.12 and 1 AO 13-Beam line  2ABeam line 2A would feed the proposed kaon factory and/or experimental area north of the vault. The line would provide a high in­tensity beam of energy > kOO MeV. During the past year the vault segment of the Tine has been defined and is shown in Fig. 81.Several choices for the 2VB1 dipole bend angle were investigated (45°, 50°, 55° and 60°). Of course, each of these corresponds to a different bend in the combination mag­net (at kOO MeV, 20°, 15°, 10° and 5°, respectively; at 500 MeV, 10° less in each case). For each configuration it was pos­sible to obtain a solution in which the beam beyond dipole 2VB1 was doubly achromatic and had a diameter ^ 2 cm. Engineering estimates indicated that the overall cost of the com­bination magnet and 2VB1 dipole dependedonly upon the total bend angle and not upon a particular choice of individual bend angles. Ultimate choice of a 5° combination magnet bend (at ^00 MeV) and 60° 2VB1 dipole bend was based upon the following considera­tions: This option requires a smarller mag­net, and thus the least steel, near the exit horn. Perturbation of the magnetic field of the cyclotron is then minimized. Further, by reducing the amount of material in a par­ticularly 'hot' radiation area, installation and maintenance procedures become simplifiedFig. 81. Layout fo r  the proposed beam line  2A.82SPECTRO M ETERFig. 82. Beam line 4B, showing the location  o f  the proposed 5-quadrupole tw ister.Beam line  4B tw is te rPart of the program for the upgrading of the MRS is the installation of a beam twister on beam line AB. The twister, whose simplest form consists of five quadrupoles all oriented with their poles at an angle of kS° to the vertical, would rotate beam disper­sion from the horizontal into the vertical plane. Experimenters have indicated that with the twister installed it would be desirable to retain the use of target ABT1 , the possibility of a horizontally dispersed beam at ABT2 and the option of using a sole­noid when running polarized experiments at ABT2. Incorporation of these requests into the design was studied during the year.The most acceptable solution appears to be the arrangement shown in Fig. 82, in which the twister is centred between target loca­tions ABT1 and ABT2. This configuration has the advantage of retaining the use of target 4BT1 and allowing the installation of a solenoid upstream.In normal operation a horizontally dispersed focus is produced at 4BT1. The twister operates as a unit magnification device between targets 4BT1 and ABT2, rotating the horizontal dispersion into the vertical plane. The twister can also be used in a 'non-twisting' mode, that is, the horizontal dispersion can be imaged at ABT2 as a hori­zontal dispersion.Incorporation of a solenoid into the beam line complicates the problem. It can beshown that in rotating the spin of the pro­ton beam through an angle <j> the solenoid also rotates the beam through an angle 0 = <f>/2.79- Consequently, in order to de­couple horizontal and vertical motion com­pletely, the twister itself must be rotated by an angle 6/2 from its normal position. Alternatively, one could obtain a solution in which a vertically dispersed focus, uncoupled to horizontal plane motion, is obtained at ABT2. The latter would allow coupling in the other particle co-ordinates. Preliminary results indicate that satisfactory solutions can be attained for either situation. Further studies of this design and of second-order effects will continue into the next year.Beam line  4CThe purpose and the characteristics of the line have been extensively described in the 1979 annual report. During 1980 the beam line was commissioned and used at several energies between 210 and 520 MeV. This required setting up the tunes for these enei—  gies and establishing a setting-up procedure to be followed by the operators. Briefly, the procedure is as follows: The beam linequadrupoles upstream of the 1 mm collimator are carefully set up to provide a waist at the thick polarimeter location and an almost parallel beam envelope at the collimator entrance. In this way both transverse emit- tances of the collimated beam are minimized in size. This makes the tuning downstream easy, provided the beam centring along the line is carefully optimized. Such tunes have been established for 7 energies, and operat­ors are now capable of setting up tunes for intermediate energies without physicists' expertise. Accurate work had to be done to interpret some disagreement between measure­ment and theory upstream of the collimator. This was found to be due to errors in the positions assumed for some of the monitors and for the polarimeter and to inaccuracies of as much as 10% in the calibration of the quadrupole fields.SECONDARY CHANNELSPion and m uon flux  m easurem entsA general survey has been made of the parti­cle fluxes and contaminations in the second­ary channels viewing the 1AT2 production target. Two target materials, carbon and beryllium, and three proton beam spots, cir­cular, horizontal and vertical ribbon, were83used during these measurements. The beryl­lium targets used were encased in stainless steel water cooling jackets with 0.005 in. entrance and exit windows while the carbon target was water cooled only on the side opposite the secondary channels. The object of these measurements was to evaluate the effects of operating with a circular beam spot on a carbon (pyrolytic graphite) produc­tion target on the secondary channel particle fluxes since these are the anticipated beam and target conditions for operation above 200 yA. The particle flux measurements were normalized by using the flux measured from the M 13 channel viewing a thin target at the IATI target location.There was a large amount of data taken during these measurements and this is difficult to present in a short closed form. However, there are some generalizations that can be made which may be summarized as follows:1 )  t t -  fluxes from the carbon target were 80-85% of those from beryllium (for equal g/cm2) at 500 MeV.2) t t and y+ fluxes from the carbon target were 100-110% of those from beryllium.3) Electron contaminations were proportional to the amount of material between the production location and the channel.There was therefore approximately a fac­tor of 2 worse contamination from the enclosed beryllium target than from the carbon target under most usable beam cond i t ions.The above flux measurements were made for 500 MeV incident protons. At the end of these measurements the beam energy was lowered to 450 MeV and particle fluxes F were measured in the M8 and M20 channels for the horizontal ribbon beam spot. The results of these measurements are1) for the beryllium target F(450 MeV)/F(500 MeV) = O .67(200 MeV/c t t "  in M8) = 0.73 (backward y+ in M20)2) for the carbon targetF (450 MeV)/F(500 MeV) = 0.61(200 MeV/c t t -  in M8) = 0.65(backward y+ in M20)Fig. 83. Proposed location  o f  a permanent quadrupole magnet to  double the w- f lu x  in  the M8 channel.M8 channe l im provem entsCalculations show that the flux of 180 MeV/c negative pions from the biomedical channel M8 could be improved by a factor two by insert­ing an 8 in. long samarium-cobalt permanent quadrupole magnet in the 1AT2 target assembly 23 cm from the production target (Fig. 8 3). With an extra 12 in. quadrupole added to the end of the beam line the final beam spot can be made similar to the present one. Some hardware problems are presently being inves- t i gated.M13 channe l ex tens ionThe proposed Ml3 extension consists of a 60 cm long dc separator to separate positrons from polarized 30 MeV/c positive muons (surface muons), followed by a quadrupole triplet. One of the reasons for the exten­sion is to provide uncontaminated surface muon beams during the period in which M20 is being upgraded. The quadrupoles and their power supplies are on site; the separator can easily be constructed with available components.With a horizontal and vertical slit system between separator and triplet it will be possible to obtain beam spots as small as 0.5 * 0.5 cm2 and a flux of 2.5 x lOVsec for a 100 yA proton beam on a I cm carbon target at IATI. The luminosity is about half the luminosity of the present Ml3 - Such a com­bination of high luminosity and small beam spot has yet to be realized anywhere.10 cm  Be ta rg e t5 0 0  MeV —protons8437.5° LEGFig. 84. Redesigned M20 channel.M20 channe l redesignThis study, whose initial features were described last year, has now been completed. The general layout has been maintained; how­ever, the quadrupole doublet preceding the dc separator, in the 37-5° leg, has been re­duced from 12 in. to 7 in. diameter, avoiding interference with the 75° leg and allowing both legs to be installed permanently (Fig. 84). Also the final 37-5° quadrupole doublet has been replaced by a triplet.The 75° leg will mainly be used for decay muon beams generated between the two bending magnets; for these it appears that the luminosity at the final focus can be increased by a factor 6 over that available from the present channel. A factor 2.5 is gained by replacing three 7 in. quadrupoles by 12 in. ones, and a further factor 2.5 by incorporating a true decay section of 10 alternating gradient quadrupoles between the bends. A 6-quadrupole decay section was also studied, but the 10-quadrupo1e case gave 25% more forward muons and 50% more backward muons. For a 10 cm beryllium target and 166 MeV/c pions the forward y + flux (173 MeV/c) is estimated to be 7-3 x 106/sec/ 100 yA altogether at the final focus, with 2.5 x 105/sec/100 yA within 4 x 4 cm2 ; the corresponding figures for backward y+(86.5 MeV/c) are 2.6 x 106/sec/100 yA and 0.6 x 106/sec/100 yA. (Similar calculations for the present channel are in agreement with the observed fluxes.)Having two final legs to the channel (at 37-5° and 75°) suggests the interesting pos­sibility of delivering the forward and back­ward muon beams simultaneously to separate experiments (their average momenta being in the same 2:1 ratio as the angles). With thedecay section tuned for backward muons this turns out to be quite feasible, the forward muon intensity being reduced by half. The forward y's would be unseparated, as at present, since momenta > 110 MeV/c are too high for effective use of the dc separator in the 37-5° leg, but backward muons in the 75° leg would be clear of contamination.It is also possible to tune Q2, Q3 and Q4 for a c le a n  forward muon beam in the 37-5° leg without turning on the separator, at the ex­pense of 30% backward muon flux in the 75° leg. The contaminating electrons, pions and unpolarized cloud muons from the production target are shifted off axis horizontally after the 37-5° bend and can be readily re­moved with a slit 1.5 m after the separator. In that case there will be 4 x 10J/sec/100 yA backward y+ in the 75° leg and simultaneously 5 x 105/sec/100 yA forward y+ in the 37-5° leg in a 4 x 4 cm2 spot for a 10 cm Be production target.The momentum acceptance of the line is about 7% FWHM (Ap/p). For surface muon beams im­proved momentum resolution is desired and therefore momentum slits are placed 25 cm downstream of Q 4 . At this position a hori­zontal dispersed focus can be obtained with a ratio between horizontal magnification (0.6) and momentum dispersion (1 cm per X) of0.5- This makes it possible to have a reso­lution of 3-7% FWHM for a 10 cm long and 2% FWHM for a 5 cm long production target.The expected surface muon flux has been cal­culated by scaling from the experimental results of the M 13 channel for a 1 cm long carbon production target. The predictions are 1.4 and 0.4 x l06/sec/100 yA for the long and short production targets, respectively. Beam spots are about 3 x 2 cm2 FWHM.85BL1A T2Fig. 85. Suggested layout o f  a high f lu x  polarized  backward muon channel.H igh flu x  po la rized  m uon channelPreliminary designs have been studied for two superconducting solenoid muon channels which give high fluxes of highly polarized backward muons. The first channel takes off at a forward angle from the pion production target and at 85 MeV/c gives approximately half the muon flux achieved at SIN for the same con­ditions. The factor two is due to the lower proton energy at TRIUMF.The second channel takes off at a backward angle where the production cross section for low energy pions is high and gives b2 MeV/c muons (Fig. 85). A special feature of this channel is that the muons are produced in a b m long superconducting solenoid and ex­tracted with two additional solenoids placed on either side of a bending magnet. The first solenoid gives a small beam spot at the centre of the bending magnet; this is then imaged to a final focus with the second solenoid. The muon capture solenoid is assumed to have a l2 cm diameter bore and a field of 3 T. For a 10 cm long carbon pro­duction target, 100 pA 500 MeV protons, the flux of negative b2 MeV/c muons in a 10%. momentum bite is 10G/sec for a 6 x  6 cm2 beam spot and 0.5 x 10G/sec for a b x b cm2 beam spot.Pion sp ec trom e te r ‘D iscove ry ’A spectrometer has been designed which could be used for pion studies in beam line IB and Mil. It has a Q0D0 configuration, with the quadrupole being an 8QN16M/7; the first sextupole is a regular 12 in. type, the second is an asymmetric sextupole of new design, and the dipole magnet is also new.The spectrometer length from target to focal plane is about 5 m. The angular and momentumacceptances are 15 msr and 140%, respectively.The momentum resolution varies from 2.5% p0 to 0.04% p0 depending upon the degree of software correction or phase space limitation used. Angular resolution in the non-bend plane is ±3 mrad with software corrections.The scattering angular range is 30° to 160° and the maximum momentum is 600 MeV/c.REVM0C calculations indicate that the angular acceptance is insensitive to target size but that the use of vacuum windows would cause a serious deterioration in the resolution.BEAM DIAGNOSTICSThe increase in microampere hours has led to several tests of the remote handling of moni­tors. A gas-filled multiwire ion chamber and a secondary emission profile and protect monitor were successfully exchanged on the 1 AM 11 structure, located in front of the thermal neutron facility. The retractable ion chamber had lasted for close to100,000 pA h and was only replaced to rearrange the monitors on the structure. The carbon wire secondary emission profile monitor mounted on the 1AT2 target ladder began to show wire-to-wire variations in efficiency after 160,000 p A h o n  a 10 cm long beryllium target. During meson production the moni­tor is retracted to a distance of about 10 cm from the target. This monitor cassette was also easily exchanged remotely.</The Cerenkov monitor, which is supposed to respond to pair production from y-rays asso­ciated with ir° decay at the 1AT2 target, showed darkening of the light guide and phototube glass. This device was installed in 1975 shortly after initial cyclotron ope­ration and is located near the exit of the first bending magnet in a secondary channel about 3 m from the target. The device has been redesigned with the phototube below the beam plane, and the use of radiation- resistant glass will be explored.A proportional chamber profile monitor has been constructed at the University of Alberta and, by varying the bias voltage from 0.3 to 3-8 kV, has given profiles for a beam intensity ranging from several nano­amperes to 1O4 protons/sec. The device fits into a standard monitor box, uses standard cables and electronics, and can be used in any beam line providing suitable proportional chamber gas.86COMPUTING SERVICES compete for access in a 'line concentrator'This year the public terminal room in the old CRC Lab (supported by the Computing Centre) has seen the addition of three more CRT terminals and replacement of the 300 1pm Printronix printer by a (theoretically)600 1pm model. The good resolution plotting capability of this printer is particularly useful. The Service Annex terminal room has been provided with two more CRT terminals, making six in all. Here also the COMTERM printer is to be replaced by a Printronix in the new year; a separate card reader will be ma i nta i ned.The considerable expansion anticipated in the asynchronous communication system has been stymied by the continued delay (now over a year) in installing extra telephone lines to TRIUMF. This delay may fairly be attributed to a variety of factors, among them being the substandard quality of UBC manholes.Although the number of permanently connected stations has only increased by three, there has been a valuable operational improvement in that each of these stations has a direct link to the computer and no longer has toIn order to bypass the telephone line short­age, two more multiplexers have been built capable of supporting seven stations each, while the Computing Centre has promised six­teen more ports. The first of these multi­plexers has now been installed. The overall situation is summarized in the followi ng table :Telephone circuitsAsynchronous facilities UBC CC ports UBC CC 1i nes Mult iplexed 1i nes TRIUMF stations ^A800 bd terminalsSynchronous 1 i nesNov. Nov. Nov. Dec.1977 1978 1979 19807 8 9 96 9 11 269 15 18 261 2 2 38 12 17 260 2 2 33 3 2 1Work on software support for synchronous communications has been suspended for lack of manpower. Various options for a high speed (megabaud) link to the Computing Centre have been compared by the Electronics group; the preferred choice is optical f i bre.87CYCLOTRON SYSTEMSION SOURCE AND INJECTION SYSTEM300 keV H beam in je c tio n  lineAt the beginning of the year the ISIS group was restructured into an 'ISIS Maintenance" and an 'ISIS Development & Engineering' g roup.During the January shutdown the cryopump system along the injection line was commis­sioned with all control panels and interlocks in place. It was then possible to remove the liquid nitrogen system running over the vault roof beams and also to remove a fair amount of wiring from the overloaded cable trays.The two cryopumps for the injection line in the vault have been fitted with radiation- hard thermocouples. The temperature of the cryopanels in the pumps can be read remotely. A threshold temperature can be set for gate valve interlocks on a controller which will indicate the time for pump regeneration and which can be done remotely. During the year the new cryopump system performed well and maintained a good vacuum during the high beam current runs.Two turbomo1 ecu 1 ar pumps have arrived for possible replacement of the diffusion pumps on the injection line. Tests will commence next year.In support of a more dependable high beam current operation, new 30 kV bend power sup­plies and bend ballasts have been installed at the electrostatic bends in the injection l i n e .A wire scanner system has been developed and installed which matches the injection line optics and hardware and the H~ beam diagnos­tic requirements. At present the system provides for 8 locally controlled wire scan­ners; 6 are installed and used successfully for H~ beam studies in the injection line. Next year 8 more wire scanners will be added to the system. To reduce the heating of the scanning wire at high beam currents and to minimize the effect of the scanner on the H“ beam, each scanner scans the beam only once, and the signal is stored on a scope for ob­servation. Each scanner has its own base line assigned on the scope and will display the true location and size of the full beam envelope either in a 2% or 99% pulsed mode.A system is almost completed to make it pos­sible to address the scanners locally or by REMCON.U npolarized ion sourceFor the unpolarized source terminal a new control and interlock system has been de­signed and is being built. It is hoped to install this system next year during the shutdown. With the installation of this new system maintenance on the control and inter­lock system should be more transparent. The new interlock and control system has also been chosen for the polarized source termin- a 1 .TRIUMF now has three ion sources for the pro­duction of H- beams. A fourth source 'D 1 has been designed, built and tested at the CRC test stand and will be available to ISIS at the beginning of 1981.Preparations are made to improve the match­ing of the source to the 'optics box', to allow a greater percentage of available source current to be utilized. In combina­tion with this program a study will be made to reduce the 300 kV sparking over the accelerator tube during high beam current runs .Polarized sourceIn 1980 the design of a RF spin filter and a rapid spin reversal (~1 kHz) system was started. During a 3-week visit to TRIUMF J. McKibben of LASL suggested a design which would be compatible with the 300 kV cage dimensions. By the end of the year the design had been finalized, the drawings sub­mitted to the machine shop, and manufacture of parts was in progress. Present plans anticipate assembly, testing, field mapping and installation to be completed by the fall of 1981. It is expected that not only will rapid spin reversal be achieved with this design but also that the polarization will be enhanced due to the effort being made to shield the beam from the cyclotron fringe magnetic field.Design of a comprehensive interlock system for POL ISIS was finally started. The system will be similar to the one to be installedin the unpolarized source. The Electronics group has begun assembly and installation is planned during the shutdown in 1981.RF SYSTEMRF resonatorsDuring the January shutdown a major resonator straightening program was implemented. This involved installing new floating springs which support the resonator panel to the strongback and new resonator tip supports which support that part of the resonator panel which extends beyond the strongback structure at the tip of the resonator. In order to realign the resonators it was neces­sary to revert back to using the tulip connectors between adjacent resonators. Since the tulips do not provide the necessary mechanical coupling between resonators for stable RF voltage operation, mechanical links were installed between adjacent reson­ators, including between #1 resonators and tt2 resonators which previously had no mech­anical connection between them.The optical alignment of the resonator hot arms, with the periscopes, requires the lid down and rough vacuum. Consequently the ad­justment of the levelling arms had to be carried out without the peripheral shielding. Because shimming and adjusting were previous­ly done with sagging resonators, some of the levelling arm adjustments reached their limit before proper alignment was obtained.It was felt that as long as periscope measurements could be made on the resonators it would be possible to determine whether or not they were still sagging. However, the periscopes could not withstand the high radiation fields, and it was not possible to optically monitor the resonators for sagging.The positive results of all these changes were an improved Q for the fundamental and third harmonic, lower strongback temperatures which were uniformly distributed over the resonators, and lower general RF leakage in the beam gap. However, the RF pick-up on the diagnostic probes and the temperatures on the beam stops increased. The resonators also behaved differently in that it took longer for the RF system to stabilize after the RF had been turned off for a period of time. Also observed were step changes in frequency after an RF spark-off.In the original design of the resonators the ground arm tips were made adjustable for the purpose of adjusting the frequency. However, adjustment of the resonator ground arm tips (especially the outer resonators) not only affected the frequency but also the RF pick­up on diagnostic probes, temperatures of resonator strongbacks and beam stops, general RF leakage into the beam gap, and the vacuum system. Various tip-tuning programs were carried out to try to understand the correla­tion of these parameters.Advantage was taken of a lid-raising to dis­connect the mechanical connections between the § 1 resonators and the #2 resonators. The effect was to shorten the time for the frequency to settle down following a mainte­nance day. However, sometimes there is still a step change in frequency, but much smaller, when the system sparks off. Also when the RF is off for a period of time it does not necessarily return to the same frequency.In November and December the lid was raised three times as a result of RF resonator problems with melting tips, sparking and RF leakage. The melting damage was in the area of §6, #7 and tt8 resonators which from pre­vious observations are very sensitive to resonator misalignment. A realignment pro­gram was carried out adjusting approximately a dozen resonators, and a subsequent peri­scope survey indicated that the resonator hot arm tips were well aligned. Careful adjustment of the ground arm tips enabled the machine to operate with improved relia­bility. The discovery of a screwdriver in the transmission line and a piece of masking tape on the centre post made the diagnostics of the major RF problems much more difficult.Third harm onic  a m p lif ie rAssembly and testing of the third harmonic amplifier into a resistive load was con­tracted out to Hoyles & Niblock Ltd. In order to stabilize the amplifier, suppress parasitics and make use of the existing socket assembly, the design of the amplifier had to be changed from a grounded cathode to a grounded grid configuration. The grounded grid configuration requires more drive power and therefore further work had to be done on the driver amplifier. The air-cooling sys­tem for the socket was a copy of the air- cooling system used on the I PA amplifier.We have since experienced that the cooling on the I PA is marginal and therefore would not be adequate at 69 MHz. A new air-cooling system was installed.89It is hoped to have the amplifier tested into a resistive load by the end of March 1981.R esonator rep lacem ent programDue to lack of manpower the resonator re­placement program progressed very slowly.The majority of the tools, jigs and fixtures are manufactured, but construction and assem­bly of a standard resonator has been delayed.Efforts are at present being made to speed up the resonator replacement program, and model work has started on the f t l and #8 resonators for RF beam gap leakage studies.BEAM DIAGNOSTICSThe increase in microampere hours has led to several tests of the remote handling of moni­tors. A gas-filled multiwire ion chamber and a secondary emission profile and protect monitor were successfully exchanged on the 1AM11 structure, located in front of the thermal neutron facility. The retractable ion chamber had lasted for close to100,000 yAh and was only replaced to rear­range the monitors on the structure. The carbon wire secondary emission profile moni­tor mounted on the 1AT2 target ladder began to show wire-to-wire variations in efficien­cy after 160,000 yAh on a 10 cm long beryl­lium target. During meson production the monitor is retracted to a distance of about 10 cm from the target. This monitor cassette was also easily exchanged remotely.The Cerenkov monitor, which is supposed to respond to pair production from y-rays asso­ciated with i t 0  decay at the 1AT2 target, showed darkening of the light guide and phototube glass. This device was installed in 1975 shortly after initial cyclotron ope­ration and is located near the exit of the first bending magnet in a secondary channel about 3 m from the target. The device has been redesigned with the phototube below the beam plane, and the use of radiation- resistant glass will be explored.A proportional chamber profile monitor has been constructed at the University of Alberta and, by varying the bias voltage from 0.3 to 3.8 kV, has given profiles for a beam inten­sity ranging from several nanoamperes to 101* protons/sec. The device fits into a standard monitor box, uses standard cables and elec­tronics, and can be used in any beam line providing suitable proportional chamber gas.VACUUM SYSTEMC yclo tronThe main vacuum system operated with general­ly good reliability during the year. One of the two B-20 cryogenerators was still requir­ing maintenance at an unacceptable rate and was undergoing a major overhaul at year's end. The other unit has operated reliably.The operating pressure in the cyclotron vacuum tank was <6 x 10“8 Torr from early March, after two weeks' conditioning, until about mid-August when it began to deteriorate due to a leak in exit horn #5- The leak was located and reduced in September but was sufficiently large to hold the operating pressure up at ~ 1 .5 x 10~7 Torr. Repair of the leak will be a large undertaking and has been deferred until the next shutdown.The only major loss of beam time due to vacuum problems occurred in September. Poor vacuum in the cryoline insulating space was misdiagnosed as a water leak in the cyclotron tank, and several days were wasted searching for a non-existent leak. An ion gauge has been fitted to the cryoline as the insuffi­cient sensitivity of the existing thermo­couple gauge was a major contribution to the diagnostic error.The liquid helium cryopump was tested several times during the year, and a reduction in H2 partial pressure by a factor of three was observed with the cryopump cold and the dif­fusion pumps valved off. Unfortunately the tests also turned up several operational shortcomings in the present device, and work on it has ceased in favour of the design and construction of a new pump.Beam linesAll rubber 'O' rings between the exit horns and the first dipoles in beam lines 1 and A were replaced as a preventive maintenance procedure in January. In spite of this there were two or three failures in beam line 1 due to radiation damage. A major design effort has been started by Beam Lines and Remote Handling which will result in metal seals that can be safely serviced after being i rradi ated.Beam line A vault section was fitted with remote leak-checking lines. The beam line AC vacuum system was installed and commis­sioned, and the meson hall roughing system extended to serve Mil and M 13 -90Work on microprocessor-based controls for beam lines 4A,B,C and IV was started, but budgetary and manpower constraints prevented progress beyond the preliminary design stage.REMOTE HANDLINGConstruction of the second pair of outrigger trollies was started and their completion will round out the full family of nine trol­lies for the in-tank remote servicing. All trollies have been converted to dc drives for better speed and positioning control. A CAMAC-based microprocessor is being added to the trolley control system, and will initial­ly be used on the new outrigger slave hand trolley and for leak checking. The remote leak check wand and remote continuity checker were commissioned. The resonator trollies were basically completed with the addition of a new ground arm tip support mechanism.The nutrunner trolley torque control problems from last year were corrected, and in December the first fully remote levelling of resonators was successfully completed. A low speed, high torque, right-angled nutrun­ner was added, and a high speed horizontal and vertical (with remote rotary positioning) nutrunner was designed.The lift trolley performed reasonably well for a total of 70 h of shadow shield place­ment and removal (three iterations). Most of the in-tank remote handling problems in 1980 stemmed directly from equipment damage and misalignments resulting from now having to remove all the equipment from the vault while the cyclotron is running.Beam linesA second back-up target flask was designed, and a dedicated flask for the septum magnet was fabricated. A new fully remote service­able b in. vacuum sea 1/coup 1ing (double indium) was designed and manufactured, and will be introduced in the vault, on beam lines 1, b and 2C. All 8 in. indium seals are being replaced with double indium as the opportunities arise.SAFETYThe TRIUMF Safety Group (TSG) was expanded from nine to eleven members in 1980 with the addition of a health physicist responsible for the radiochemistry program and a full­time industrial safety officer. There has been a significant expansion in facilities that required effort in the design and manu­facture of new interlock systems and radia­tion monitoring systems. The radiation levels and contamination levels have been steadily increasing as the beam currents are being run more regularly at the 100 yA level. This has led to the implementation of routine monitoring procedures that were not previously required, and there are now three full-time radiation surveyors whose time is constantly in demand.TSG prepared a safety course which was divided into five 2-hour lectures, to be given to all staff in the new year.The TRIUMF Safety Advisory Committee (TSAC) met twelve times during the year and had its workload doubled from the previous year.This increased workload led to a review of the TSAC organization, and a new subcommittee structure was implemented. All new submis­sions to TSAC were first delegated to a standing subcommittee for review before being presented to the TSAC meeting. These subcommittees are: the Operation Radiation Hazards (ORH), Induced Radiation Hazards (IRH), Chemical Toxicity and Flammable Hazards (CTF) and the TRIUMF Accident Preven- tion Committee (TAPC). I terns of concern were changes to the safety interlock system, radioactive shipping procedures, waste management, new experimental and applied program facilities and radioisotope licens­ing.The TRIUMF Accelerator Safety Report, which consists of two substantial volumes, was being compiled by the Documentation Officer for submission to the Atomic Energy Control Board in support of our accelerator licence application. This report should be avail­able ear 1y in 1981.R adiation p ro te c tio nThe number of individuals on the TLD and neutron badge service rose to 489 during 1980. The total man-dose measured by the badges was 23 man-rem. No reading was recorded on the neutron badges. A frequency distribution of accumulated gamma/beta dose91ACCUMULATED GAMMA/BETA DOSE(mrem)Fig. 86. Frequency d is tribu tion  o f  accumulated gamma dose.is shown in Fig. 86. Approximately 20% of this year's man-dose was received during the repair to the cyclotron resonators in December.The Dose Study Group completed a first-order estimate of the future dose commitments and concluded that a substantial effort has to be made to improve procedures and equipment if the intended high-current operation is to be realized. More of the group's effort this year went into screening and evaluating the procedures for ongoing maintenance and development, especially prior to shutdowns.A major acquisition during 1980 was a Beckman 8000 gamma counter to facilitate the analysis of routine swipes necessitated by the increasing amounts of radioactivity handled by the radiochemistry program. A gate-monitoring system was installed at the main entrance into the TRIUMF security fence and has proved to be very useful. Ten new stack monitors were built after a prototype had been successfully tested. A dedicated monitor was set up exclusively for routine thyroid monitoring for 125I and 123I in those involved in the processing of 123IR ad iochem istry  opera tionsThe Chemistry Annex was licensed for a possession limit of 10 Ci per target for TRIUMF operations. AECL Commercial Products obtained their own radioisotope licence for operation at TRIUMF in the same period.A temporary shipping/receiving facility has been installed in the IRL, and became functional in the latter part of 1980. A routine radiation control program wasimplemented in the Radiochemistry Annex.This includes surface and swipe surveys, fume hood air flow checks, radiation monitor checks and air sampling. A finger TLD ser­vice was started (TLD mounted on a ring), and a foot & hand monitor became functional in the Radiochemistry basement. In addition each lab has been provided with a portable radiation montior. A personnel decontamina­tion kit, a first aid kit, a radiation decon­tamination wagon and a laundry facility were also made available.Installation of the Radiochemistry Annex holding tank and dilution system and the stack sampling unit was also completed.As for the safety aspects of the TRIM opera­tion, an extensive survey program has been executed with the Beckman 8000 being used to assess the activities in all swipe samples. Thyroid uptake measurements have been per­formed on a weekly basis throughout most of the year. Laboratory surveys were also ex­tended to the 70 MeV facility, mainly during the 123l and 120i production runs.Safety in te rlo ck  system sA new set of logic equations were burned in­to the PROMs of the central safety system (CSS) during the June shutdown. These new equations were required to accommodate the installations of the very 1ow-intensity pro­ton channel, beam line 4C, and the new high- energy meson channel, Mil. This new logic was subjected to extensive testing before the shutdown in a CSS simulator system and during the shutdown in the CSS itself.Further changes in the equations were under consideration by year's end to accommodate changes in beam line 2C and beam line IB operat i ng modes.The new meson channel Mil required the in­stallation of a new area safety unit (ASU) and interlock chain. The Mil ASU uses a microprocessor (a Cromemco single card com­puter based on a Z80 CPU) and electronic buffering to replace the relay logic of older systems. This new style ASU also has a front panel which is designed to function as a flow diagram of the operations necessary to gain entry to the Mil area or to secure the area in preparation for beam.Modifications were made to the beam line 4B, beam line IB and the vault ASU's to allow for short controlled accesses. The controlled accesses to beam line 4B and beam92line IB make small alterations to experiment­al equipment in those areas simpler to accom­plish. The controlled access to the vault allows for a maximum of three persons (personal keys from transfer lock must be carried) for a period of less than 10 min without dropping out the lock-up chain. The purpose of the vault controlled access is to allow minor inspections or adjustments to be made without the requirement of a complete re-establishment of the lock-up chain. The resecuring of the area following such minor entries often incurred a larger radiation exposure than the job itself.Modifications were made to the M9 ASU so that entry into the M9 area is now prevented if high X-ray radiation levels are present. These X-rays result from operation of the electrostatic separator and can be reduced sufficiently to allow entry by lowering the voltage on the separator.The safety system for the b2 MeV cyclotron was modelled after the TRIUMF safety inter­lock system and was tested on the safety system simulator and installed in its final configuration for initial tests. Final tests will be conducted when the b2 MeV cyclotron is installed.In d u s tria l sa fe tyEffective May 1 TRIUMF appointed its first full-time industrial safety officer. His areas of responsibility are varied and include fire prevention, safety inspections, industrial hygiene, management of hazardous materials, first aid programs, accident in­vestigation, and the development of an ongoing staff training program.Two fire inspections were held during the year in conjunction with the UEL Fire Department. These inspections included the semi-annual audit of all fire extinguishers on site. The quota of extinguishers has been upgraded and documented. Key plans and accompanying emergency procedures have been regularly revised to meet changing needs at TRIUMF.A new hazardous materials storage building was completed by the end of the year and provides TRIUMF with an excellent facility for the storage of hazardous materials. The solvent dispensing area has been equipped with grounding/bonding equipment. Chemical spill kits have been distributed throughout the s i te.A target preparation iab was built in the meson hall and has been equipped with all necessary safety equipment to provide a much needed facility in this area.The construction of the meson hall gas handling system facility began in late fall and is expected to be completed early in the new year. Proposals have been made for the relocation and expansion of the gas bottle storage racks.During the course of monthly site inspections a deficiency notification and follow-up form was added to the report and seems to have been effective in improving resolution.There has been a dramatic decrease in site deficiencies noted each month.Preparation of an industrial safety course for all TRIUMF staff has begun and should be ready for presentation in 1981 on an ongoing basis. It is hoped it will further reduce the number of accidents/injuries at TRIUMF.At the close of the year TRIUMF continued to enjoy a good accident/injurty record. For all reported injuries the median frequency rate was 0.37 injuries/100 workers/month, with an expected downward trend. The median severity rate, or time lost due to injury, was 0.b9 days/100 workers/month. However, an increasing trend in severity can be ex­pected. It was noted that the majority of first aid calls involved injuries to eyes and hands. Improving safety and knowledge of protective equipment and work procedures will be a target to reduce these injuries.It is hoped that the upcoming safety course presentations will relieve this situation.CONTROLSAs reported in last year's annual report, a workshop held in the last month of 1979 identified the major problems, proposed spe­cific solutions and determined future direc­tions for the TRIUMF control system. Most activities in 1980 were directed towards implementing that plan.The REMCON program had been found to be too busy, primarily because of time spent addressing ADC channels and updating second­ary beam line displays. The secondary beam line control system was modified such that data from the central system are parallel loaded into a CAMAC memory, rather than sent serially with interrupts via a CAMAC teletype93. ■ r  » iHLL CLI I| S130 |  \ S130 T ‘I , I 1___ __I<< >> RC MCA "c y " MCA “c n "S/N '----- S/N S/NMCAjr “ D1" " ]  j “ d 2S/N f -I  I<(m p m ”CAMAC7 Branches ( to  Cyclotron and Console)Fig. 87. Expanded TRIUMF con tro l system.TS 200ProgrammingSystemdriver. The resultant time saving has per­mitted support of two additional secondary channel control systems— those for M9 and Mil. An extensive program to convert all CAMAC ADCs to scanning types, which require one CAMAC cycle per read rather than several was begun. Three ADC systems were changed over, and eight remain to be converted.The 'cyclotron' program had been found to be overburdened by the task of updating the console '6ll‘ displays. This was resolved by off-loading this task to a TRIMAC micropro­cessor which receives its data from the cen­tral system via shared CAMAC memory. The system works well, and the effect on the cyclotron program has been significant. A second aspect of this program had been to replace the 6 11 storage displays and their CAMAC drivers with some raster scanning alternatives; however, the modules tested first proved unsatisfactory (too slow), and a solution has not yet been found.The 'console' computer was also too busy, in this case primarily from formatting and seri­ally outputting data for the main console CRT displays. Here the proposed solution was again to off-load this mindless task to spe­cialized display processors; however, in this instance the strategy was to use additional Nova/Eclipse family computers rather than more microprocessors. The reasons for this cho i ce were :1) The higher speed of the minicomputer would permit more displays to be updated per processor.2) To reduce interprocessor communications, the display processors should have discs of thei r own.3) The present mix of console CRT type dis­plays are not all run from CAMAC, let alone from a single CAMAC crate, as would be desirable if TRIMACs were to be used.k) The Nova/Eclipse display software exists and could easily be adapted to the new systems.3) Use of additional minicomputers would permit some task redistribution among com­puters, with a resultant reduction in inter­processor communications and increase in ava ilable memory.These considerations led to a plan for expan­sion of the control system which is described below.System  expansionThe planned additions to the control systems are shown in dashed lines in Fig. 8 7 . This plan was arrived at not without controversy and compromise, and was recognized as useful only for the next years.The computer 'D I ' is the first specialized 'display processor', intended to relieve muchof the load from the CN computer. This new function is performed by the Supernova al­ready in the system and known previously as 'computer T 1. The present Eclipse S200 com­puter, now known as the 'message organizer', is to become the programming system. Two new SI 30 Eclipses are to be added, one now referred to as 'TTY', which will do certain tasks presently performed in CN, REMCON and computer 'T '. The second, called 'HLL'(high level language) will be programmed largely in FORTRAN, performing some tasks now done by the message organizer, and new ones designed largely by the Beam Development group. Other tasks now carried out on the message organizer are expected to move to the Data Analysis Centre VAX.It is evident from Fig. 87 that the planned expansion is dependent upon two corollary developments: extension of the interprocessor communications bus (MCA) from 3 to 7 com­puters, and development of a 7_port memory (MPM) to replace the 3-port memory now in the system.Considerable progress was made during 1980 toward the implementation of this plan.Tests were performed in the spring to demon­strate the feasibility of extending the MCA bus. Subsequently, two SI 30 computers were ordered and arrived on schedule in October, whereupon the MCA bus was extended to include 7 processors, successfully passing an over­night reliability test without failure. Shortly thereafter the D1 program was imple­mented partially, and the system ran that way for a few days before failure of one CPU resulted in a temporary return to the previ­ous system. Completion of phase I is sched­uled for early 1981 and awaits the repair of one Supernova, the installation of floating point software in the two Eclipses, and completion of the 7-port memory.System  im provem entsIn addition to the efforts directed toward the expansion described above, numerous other improvements, major and minor, were implemented during 1980, and over 50% of our effort was required to maintain the system and support changes and improvements in other cyclotron systems.Two major contributions to control system downtime in 1979 were attacked directly in 1980. The tank thermocouple multiplexing system was completely redesigned and simpli­fied, and a quick disconnect system forCAMAC power supplies was designed and in­stalled on 80% of our crates. Also intended to reduce control system downtime is a pro­gram to reduce the total number of crates in the system by improving packing densities. For example, the number of crates in POL ISIS has been reduced from 2 to 1 by the instal­lation of octal DACs and new T R 1UMF-designed octal 'DIGIs ' (digital controllers).Software improvements included a complete redesign of the display driver data base; a number of new high current scans to protect certain probes, strippers, targets and moni­tors from too much beam; improved status display and control of the IATI, 1AT2 and TNF targets; implementation of a system which allows error messages to be directed to a combination of one or more output tele­types or screens; and programs to pass console data to the new 'HLL' computer, al­lowing special algorithms written in FORTRAN by the Beam Development group or Cyclotron Operators to be implemented. An early application of this facility has been opera­tion of harmonic coil doublets from the main console.R e lia b ilityIn 1980 the control system was charged with 86 h of cyclotron downtime, or about 8.5% of the total downtime for the year. These figures are unchanged from the previous two years.40% of this downtime was caused by a series of major problems in the CAMAC system dis­tributed over 4 branches and 5 major epi­sodes, one of which resulted in 22 consecutive hours down— our largest single downtime ever. The problems included oscillating power supplies, failed crate controllers, and a mechanically defective crate. No other single identifiable cause contributed more than 5% of the total controls downtime, the remainder of which resulted from amiscellany of hardware failures and programbugs— the latter especially related to new scans.Because of its timing, little downtime wasattributed to the most alarming reliabilityproblem— a series of computer failures at the very end of 1980. At least two memories have failed, and one elusive problem remains in a computer chassis after over two months of attempted diagnosis. Last year we reported almost no failures of computers or peripherals, and it is to be hoped that the95large number of problems at the end of 1980 does not signal the impending demise of our 10-year-old family of Supernovas.E lec tron ics  supportAt year's end the Electronics group staff consisted of 8 engineers, 17 technicians and 6 assemblers, an increase of 2 over 1979- The staff was increased to provide more sup­port to the experimental program through maintenance of pool electronics and PDP-11 data acquisition systems.Distribution of the group's efforts was as fo11ows:System design and construction 10.5 man-yr Maintenance, repair and improve­ment of central control system and other machine systems Nucleonics development Nucleonics maintenance Assembly to support above and other groups Supervision and clerical--rate at end of year1980 saw completion of several interlock and control systems using CAMAC microprocessor controllers:Interlocks for the 500 MeV gas target were added to the 500 MeV irradiation facility system. That system, in turn, was inter­faced to the central control system (CCS) to provide status readout in the control room.An interlock and control system for the 70 MeV interim target was built and used successfully during all operations of the target. As this facility expands into the full beam line 2C, the control system will be enlarged to a complete beam line control system.The obsolete position readback equipment for the SFU scattering chamber was replaced with a TRIMAC-driven CRT display. Later the stepping motor drivers will be controlled by the same TRIMAC.Interlocks for 4 extraction probe vacuum systems (beam line 1, beam line 4 and future beam lines 2A and 2C) were installed in December. This TRIMAC-controlled system shares a CAMAC crate with the 70 MeV con­trols, confirming that multiple controllers and tasks can share CAMAC cost overhead.The ISIS second harmonic buncher control sys­tem was installed in October. Controls for other ISIS/RF devices— chopper, pulser, etc.—  are being developed in the lab. These will be installed as they are completed. The complete system will use six TRIMACs sharing 1/0 and display equipment in one crate.A nuclear magnetic resonance (NMR) system was built using two TRIMACs. One TRIMAC controls the excitation of the resonant cavity, mea­sures the phase and amplitude response, and processes the data. The second generates a CRT display of the averaged resonance curve in one of three modes. In the first mode the most recent scan is displayed, in the second a stored reference scan is displayed together with a new scan, and in the third the areas under successive resonance curves are dis­played as a function of time. The system is now being used to measure the degree of polarization of a frozen alcohol target.The Electronics group provided all hardware support for maintenance and improvements of the CCS. Improvements made during the year included replacement of the old resonator thermocouple measuring electronics with a new system based on 16-channel thermocouple amp­lifiers designed in 1979- At the same time the analogue-to-digital converter servicing these 128 signals and 256 other signals in the area was modified to automatically scan its digital output into a CAMAC memory. This modification was part of a continuing pro­gram to reduce CCS computer overhead. Ana­logue readings, with scanning A/Ds, can be obtained with one CAMAC cycle rather than six. Designs are complete for conversion of all remaining A/D systems. All will be con­verted by the end of 1981 . Tests done before conversion started proved that a 25-301 reduction of REMC0N CAMAC cycles will result from the change to scanning A/D s i te-w i d e .A single width octal digital control module was designed and 20 produced. This unit performs the functions of two of the old 2-width 0441 controller used site-wide as a remote 0N-0FF controller. The 4:1 CAMAC slot saving has allowed new installations to be made without adding crates to the system.A new digital controller with interlock in­puts (DI CON) is in production. It will be used to provide long-awaited interlocks and control in the polarized ion source. It will also replace the obsolete system in the main ion source.8.5 man-yr2.5 man-yr 1.5(3)*man-yr4.0 man-yr2.5 man-yr96A new Supernova-Eclipse multiport memory has been designed to replace the prototype unit in the CCS. The new unit has 8 ports; 16K RAH (expandable to 64k ) , 2K PROM. Memory can be accessed under programmed I/O or by data channel transfer. To facilitate block trans­fers between computers via this unit, a CALLregister is implemented whereby any computer can raise an interrupt request in any other computer(s). Acknowledgement of the inter­rupt identifies the interrupting source(s). Two-computer tests of the new unit are scheduled for April 1981.97EXPERIMENTAL FACILITIESINTRODUCTIONDuring 1980 the fast pion channel Mil, which views the 1AT1 production target, was in­stalled and the first pions observed from the straight-through port of the second bending magnet. The commissioning of the power sup­plies for this latter magnet and the sextu- polesonMll is expected in early 1981 , and channel optics studies using an a 1pha-particle source will be carried out during the upcoming 1981 spring shutdown. Some problems were encountered with the septum magnet toward the end of the year; however, it is expected that it will be available for experiments early in 19 81.The M9 channel has operated throughout the year in the configuration described in the 1979 annual report incorporating a dc parti­cle separator. A larger acceptance RF separator has been designed and constructed to replace the existing separator and will provide higher separated muon fluxes to the M9 W3 and M9 W4 experimental locations. It is expected to exchange the separators early in 1 9 8 1.Studies have continued on the pion spectrom­eter 'Discovery' and on the improved M20 channel described in last year's annual report. A detailed design of the spectrom­eter coils and magnet steel was completed and is ready to be sent out for bids for fabrica­tion. Quadrupole magnets and power supplies were purchased for the spectrometer and M20. The channel is presently being designed in detail for installation in late 1981 or early 1 9 8 2.Efforts to improve the energy resolution of the medium resolution spectrometer (MRS) have led to a factor of two improvement, giving 110 keV at 200 MeV. Work has continued toward the reduction of the amount of material in the path of particles traversing the spectrometer, and design work has started on new focal plane wire chambers with improved position resolution. A redesign of beam line 4B was undertaken this year to in­clude a five-quadrupole 'beam twister' and allow the production of a vertically dis­persed focus at the MRS target location. This will be required to operate the spectrometer in an energy loss mode which will eliminate the limitation of the resolution due to the energy spread in the incident beam.In addition to the above developments, the Experimental Facilities group has continued its activities in the areas of experimental and production targets, data acquisition software, detector and wire chamber facili­ties and general experimental support.Further details of these activities are in­cluded below and elsewhere in this report.MESON HALLRF separatorThe RF separator will be installed on M 9 , replacing the dc separator, to increase the transmission of 77 MeV/c cloud y~. The beam optics and conceptual design were described in the 1979 annual report.During the year the detailed design of the separator and the fabrication of all major components were completed. The RF amplifier was refurbished and tested. Late in the year assembly was under way in preparation for off-line testing and commissioning early in 1981. Instal1 at ion is planned for late spring or early summer of 19 81.M9 ex tens ion  w ith  dc separatorThe extension to M9 including the dc particle separator was completed late in 1979. Dur­ing 1980 the configuration of the channel remained unchanged and is shown in Fig. 88. The capability of the channel to deliver beam to each of the three experimental locations F2, W3 and W4 (TPC) has been exploi ted.Early in the year the system to run the separator w i t h — 0.5 y pressure argon was im­plemented and immediately allowed an increase in routine high voltage operation up to 550 kV. Cloud muon beams of 65-80 MeV/c with pion contamination as low as 1% were then possible. The separator was also used to produce clean tt beams for TPC tests in addi­tion to clean surface muon beams.While only low voltages on the separator (-50 kV) are needed to remove the contaminant positrons from the surface muons, at high voltages the separator can be used to pre- cess the muon spin and produce a transversely polarized surface muon beam. This is shown98COcX<3}ffi99V{Et—UJ22>to<0  100 2 0 0  300SEPARATOR VOLTAGE (kV)Fig. 89. Muon-decay electron asymmetry as a function  o f  separator f ie ld .in Fig. 8 9. The asymmetry in the muon-decay electrons measured in two planes— one paral­lel and one perpendicular to the beam axis—  shows clearly the precession of the muon beam spin with increasing magnetic field (which is proportional to the separator voltage).Two technical improvements to M9 have been made this year: A new mid-plane slit-jawassembly has been installed with improved mechanical design and compatible with micro­processor control. The new assembly has pro­vision for inclusion of a degrader wheel in the future.ance of the channel, e.g., second-order cor­rections with sextupoles, will be necessary after that date.Installation was accomplished in three stages throughout the year. Poured in place con­crete magnet bases were installed in January, with final installation of the front-end components completed in July. The septum magnet was installed after six months of testing. It was installed complete with a remotely handleable stand and vacuum box- jaws assembly. The second bend magnet M11B2 was installed in October after delivery of its new coils, along with the final quadru­pole M11Q6 and the last two sextupoles.A delay was experienced in the preparation of a power supply for Ml 1B2. As an interim measure a tune was developed to produce a beam spot through the 0° port of the dipole. This enabled initial commissioning tests to begin on front-end components with M11B2 un­powered. A 180 MeV pion beam was achieved in November, and pions and protons were identified by time of flight. Preliminary measurements indicate that the pion flux was slightly higher than predicted and the pro­ton contamination of the pion beam also h i gher.Five sextupoles installed for second-order corrections are awaiting power supply deliveries in early 19 81. A slits and de­grader assembly identical to that in M 13 was completed and is ready for installation.The second improvement is the microprocessor- based control system for M9 which is similar to M13. This system will control the power supplies via REMCON as well as the slits and jaws and can access a variety of other parameters from REMCON. Some beam-tuning- related control of the new RF separator to be installed in 19 81 will also be possible from this system.M11 channe lThe TRIUMF Mil pion channel is designed for production of ir+ and tt" over an energy range from 50 to 350 MeV. The design is summarized in TRI-DNA-80-5, Design Configuration of the Mil Channel at TRIUMF, G.M. Stinson.At present the installation of this channel is nearing completion and initial commission­ing tests are under way. It is hoped that experiments can start in May 1981, although further commissioning to improve the perform­Problems developed with the septum magnet towards the end of the year. The magnet first developed ground fault problems and later an intermittent short in the coil appeared. This necessitated removal of the magnet from the beam line for work in the remote handling warm cell. The problems resulted from a pinhole water leak develop­ing in a silver brazed joint, which caused water to cascade down the coil. It is expected to complete repairs on the magnet and reinstall it in the spring shutdown of 1981 .Some of the expected properties of the Mil channel and some representative fluxes as compared to Ml 3 are summarized in Table XV.The construction of the experimental area is proceeding and shielding is being finalized. Cabling from the experimental area to the counting rooms is being prepared, with pri­ority aiven to the first exDerimental1 0 0Table XV. Predicted properties of Mil channel.Achromati c'Norma 1 1 Di spersed'Reversed D i spersedSol id angle (msr) Momentum acceptance Ap/p% Momentum resolution xo=±0 . 1 cm at target Dispersion cm/% p Beam size at target FWHM cm(X) x  cm(Y)FWTM cm(X) x  Cm(Y)10.3 (8)a3.0±0.05%01.5 x 2 . 00 . 5 x  2 . 05.0 x  3 . 01 . 0 x  2 . 87-4 (6) 3-0±0 . 1 1 1-3.3no slits slits 2 mm wide no slits slits 2 mm w i de1 0 . 1 (8) 1 . 112.7200 MeVTT ' SaAcceptance reduced when off-axis exit from 1AQ9 taken into account.Compa r i son of Ml 3 and Ml 1 channe1 s .fi Ap/p L tt Decay factor ir+d2cr/dfidTm yb/sr MeV^Channel n/uii msr FWHM m 50 MeV 200 MeV 50 MeV 200 MeVMl 3 30 9% 9 0 .2 83 10 (1 3 5°)Mil 8 3£ 14 0.140 0.445 6 (2 2 °) 26 (2 2 °)aSIN data PR 79-010.For Ap/p=1 % Ml 1/Ml 3 = 8/30 x 0.140/0.283 x 6/10 = 0.08 at 50 MeV.For Ap/p=l% Ml 1 (200 MeV t t) /M1 1 (50 MeV i t )  = 40 assuming d2o/dfidT7r = 26 yb/sr-MeV.Measured M 13 flux on 1 cm graphite target = 30 K/sec/yA tt+ at 50 MeV in Ap/p =] %.Proton contamination in Mil (no absorbers):100 MeV 0.77 pAr+200 MeV 1 .45 pAr+300 MeV 30.9 p/ir+Initial operation of the Mil channel will use a 1 cm graphite or H2O meson production tar­get. The it+ flux and proton contamination are improved using pions from the p+p -> d+ir reaction on a hydrogen-containing target. However, the pion energy is then related to the incident proton energy (208 MeV pions at 500 MeV, 124 MeV pions at 400 MeV) so that operation in this mode will cause some sched­uling problems. In addition the change from operation with tt +  to t t -  will require a retune of beam line 1A as several quadrupole polari­ties are swi tched.Future plans call for the installation of a 7 cm long liquid methane production target.This target is undergoing prototype tests at present.Thermal neutron  fa c ilityThe thermal neutron facility has been operat­ing without failure during this period. The only cyclotron downtime attributed to the TNF was 1.9 h, caused by a control system failure.The first neutron target, removed in June 1979, was shipped to CRNL for inspection. It took more than a year to make the arrange­ments with AECL and to obtain a shipping licence. The target has been cut open at CRNL awaiting further analysis.101In line with plans to increase the cyclotron beam current, a design note for upgrading the neutron target was written in July (TRI-DN-80- 10). It discusses a design that would accept 400 pA at energies varying from 200-500 MeV. The proposed schedule is for installation in December 1982. The upgraded target and moderator assembly would be commissioned by using the cyclotron beam.Three devices have been installed in the TNF in support of the Applied Program: the first was a 500 MeV irradiation facility, which is now in use for routine irradiation of isotope production targets for AECL. The second device is a rotating sample machine, installed above the neutron target. It allows more effective use of the neutron flux for neutron activation analysis by Novatrack. This device has now been in use for several months. The third device is a gas target for 18F, n C and 150 production, for use in the posi­tron emission tomography program. The target was commissioned during October. A fourth device, the neutron diffraction spectrometer, is part of the Experimental Program. It was designed in 1978 and installation is in progress. Each of these devices is dis­cussed in more detail elsewhere in this annua! report.N eutron  spec trom e te rThe neutron diffractometer for the thermal neutron facility has been fully instrumented and commissioned under microprocessor con­trol. It is now being used for studies of large monochromating crystals made of stacks of silicon wafers under elastic stress. The apparatus is suitable for both single crystal elastic scattering and powder diffraction.Due to the low flux of the thermal neutron facility, which varies between 5 x 1010 and 3 x 1011, depending on loading of the proton irradiation facility, large samples are required for reasonable data collection times. For a typical large powder sample adequate data on six peaks require one day. For large single crystals one acquires 32 peaks in a six-hour run.P R O T O N  H A L LMRS so ftw are  deve lopm entDACS (data acquisition and control system) is a software package to implement a wide vari­ety of nuclear data acquisitions and analysis jobs on Data Genera! Eclipse computers. Two major versions of DACS were released to theusers in 1930. The first version, released in early summer, was used to analyse data tapes acquired by the Honeywell computer in an earlier MRS (p,2p) experiment. This version lacked any CAMAC capability, had com­plete spectrum display and plotting capabil­ities, and a flexible compiler for specifying how the events, read from tape, were to be processed to form spectra. The analyses of the (p,2p) data with DACS was begun using the (main site) MRS computer and later con­tinued using one of the Eclipse computers in Edmon ton.The second release of DACS was in November, shortly after the CAMAC driver software was delivered from Edmonton. This was the first release having complete CAMAC capability, in addition to the existing tape playback capa­bility. Since this release date DACS has been used on three occasions for MRS single arm data acquisition.DACS is a collection of approximately 250 subroutines, written either in FORTRAN or in machine language. By including only the program modules which are needed for a par­ticular application, a wide variety of dif­ferent DACS programs may be generated.These various programs divide naturally into two major types: those tailored mainly for data analysis (i.e. tape playback) and those mainly for acquisition. Although the acqui­sition versions of DACS are all capable of playback, it is more efficient to tailor a program especially for playback. This in­volves leaving out all the program modules having to do with CAMAC communications and live display leaving more space in memory for the user-written event processor. So far the usage of DACS for data analysis has been confined mainly to the Edmonton computers.A typical application of DACS to data acqui­sition is described below for the case of the 'giant resonance experiment' (Expt. 124). This application might be called a 'typical' MRS singles experiment. The DACS program stored five one-dimensional and five two- dimensional spectra, a total of 20K channels. The maximum tape-writing speed was measured to be approximately 500 events/sec for the 25-word events. This tape-writing capabili­ty and the size of the spectrum storage region both represent substantial improve­ments over the old Honeywell computer program.The experimenter is able to tailor DACS to fit a large range of CAMAC and event pro­cessing configurations. CAMAC processing1 0 2and event processing are controlled by the experimenter using two special purpose language computers. The CAMAC compiler allows the user to specify CAMAC processes in a simple language. Each module in up to seven CAMAC crates can be assigned a descrip­tive name of the user's choosing. A CAMAC process is then accomplished by compiling a user-written list of CAMAC commands which reference the modules by name. Up to three independent events may be simultaneously acquired from CAMAC.Once the events have been read into the com­puter they are arranged into blocks which are written onto tape and also passed to an event processor. The action of the event processor is specified by the experimenter in a second special-purpose compiled language. In this language the user creates descriptive names to refer to spectra, logical tests, and other data structures which can be derived from the raw data. The processing of each type of event is specified as a structured list of these created names, including IF-ELSE-THEN structures to specify unlimited nesting of conditional processing.MRS hardware deve lopm entAn MRS development run with no front-end scatterers gave encouraging results— 110 keV FWHM at 200 MeV. This was achieved with0.3 mm high Pb strip target and a phase- restricting 'picket fence' in front of the stripping foil. Addition of 50 mg/cm2 scat- terer at the target worsened the resolution to 150 keV. Non-bend plane position resolu­tion was better than 0.7 mm, the limitation being resolution of the Yb detector.Beam line  4CBeam line AC was installed early in the year during the winter shutdown. The line was designed to deliver a proton beam of 105-106 protons/sec with a beam spot less than 10 mm diam at the polarized proton target position. The line was to operate between 215 and 515 MeV. The layout of beam line AC is indi­cated in Fig. 90.The beam polarization was monitored in beam line AA at the polarimeter location where a waist in the beam was formed. A A.75 mm thickFig. 90. Layout o f  beam lin e  4C.103CH2 foil was used to produce the necessary high counting rate. The superconducting solenoid was used to rotate the proton spin direction when required.The copper collimator installed in the 0° port of the neutron collimator was 200 mm long and had a 1 mm diam axial hole. It reduced both the transmitted beam's intensity and emittance. By varying the focus of the beam on the upstream face of the collimator, transmission varying from 1:200 to 1:10,000 could be produced. The required beam inten­sity of 105- 106 particles/sec has been observed at the target position, with reasonable stability, when beam line 1A was operated at 100 yA, indicating an overall split ratio of 1 :104 .The UCLA magnet produced a 35° bend that served both as a momentum selector and spin precessor. The steering magnets SM4 and SM5 allowed fine steering on to the polarized target volume. A specially designed wire chamber monitor operating on 'magic gas' was installed at the 4CM8 location. It allowed beam profile measurements at incident particle rates as low as 103/sec with a 1 mm wire spac i ng.It was found that Q.8 and Q9 were only required at 215 MeV; at higher energies satis­factory beam spots were obtained by correct tuning upstream in beam line 4A. Indeed, at high energies Q.6, Q 7 , Q.8 and Q9 were all powered down. Polaroid films were mounted on the upstream and downstream faces of the polarized target to confirm beam spot sizes of the order of 5 mm diam.The polarized proton target was installed during April. After target and beam line commissioning the BASQUE group performed measurements of the pp total cross section differences Aoj and Acj|_.VAULTBeam line  2CThe overall plan for a multiple use 70- 100 MeV high current facility was discussed in the 1979 annual report. Construction of several subsystems of the project have pro­gressed substantially during 1 980, and in­stallation is scheduled for April 1981.A realistic sketch of the existing components assembled in the design configuration is seenFig. 91. Sketch o f  beam line 20 magnets and monitoring devices.in Fig. 91. Since the entire beam line resides in the cyclotron vault, several un­usual features were incorporated: non-organic vacuum seals; a modular, self-positioning concept which allows rapid, initial installa­tion and facilitates future servicing.Conceptual design of a variable energy ex­traction probe for the cyclotron has been completed and a prototype is in construction.Two high current, generator style production targets are being designed and one prototype is being tested at year's end.The controls system is configured to facili­tate rapid task changes to meet a demanding schedule from the multiple users.TARGETSM eson p ro d u c tio n  targetsThe meson production target systems have operated well throughout this year. On the few occasions when faults occurred they were found, except in one case, to be due to transducer drift or human error. The trans­ducer drift problem was associated almost entirely with the water reservoir level sensors which will be replaced in 1981.The cooling-water heat-exchanger in 1AT2 was changed for an upgraded version capable of operating at the 200 yA limit of the present targets and even to 400 yA operation which may be achievable in the future. Parts for104a standby target assembly will be finished by the end of the year ready for assembly early in the new year. A description of the pro­duction targets, collimators and blockers in beam line IA was written and distributed as VPN-80-1.A prototype liquid methane target, for pion production in Mil, is about 80% complete and experiments to check the feasibility of a full-scale device will be undertaken in the new year.Polarized targetsAssembly of the A cm3 polarized proton target from the University of Liverpool was completed and the target was installed in beam line AC for two experimental runs in May and June, with vertical polarization. The coils of the polarizing magnet were then rotated and the target run with longitudinal polarization in September. During this last run the target polarization was 65%, in both positive and neg­ative polarization directions, using butanol with EHBA paramagnetic ion doping. The target was removed from beam 1ine AC in December and reassembled in the model lab to begin an ex­tended program of NMR system improvements.Design work was begun in October for a large (50 cm3) polarized proton target to operate in 'frozen spin' mode. At the same time work began to convert the Liverpool polarized tar­get so that it too will be able to operate in frozen spin mode.C ryogen ic targetsUniversity of Manitoba liquid helium-A target. This target was repaired and operated for two experimental runs in beam line AB during May and July.Liquid deuterium neutron production target.An extensive renovation program was initiated for the LD2 target. The gas storage vessels were moved outside the accelerator building and gas handling pipework was installed. A new hydrogen ventilation hood and ductwork system were similarly installed. Work is currently proceeding on the vacuum system valve control panel and on a microprocessor- based target control system.L iq u id  hydrogen targetsA liquid hydrogen target was installed in M 13 during the first quarter for use by the TINA group. In a sequentially following experi­mental run the target was filled with liquid neon for use by a University of Victoria group.The support frame for the liquid hydrogen target to be used by the (p,ir) group in beam line IB was installed during August.The BASQUE su p e rconduc ting  so leno idThe solenoid was installed on the arm of the MRS for an experimental run in beam line AB during the first quarter. It has since been installed in beam line AA for use in the polarized target experimental program under way on beam line AC.C O M P U T IN G  S U P P O R TData ana lys is  centreFollowing interviews with all potential users of an intermediate size (32 bit) com­puter at TRIUMF, as well as users and admin­istrators of comparable installations at SIN, LAMPF and the University of Toronto Physics Department, and after lengthy discussions with representatives of Digital Equipment Corporation, a decision was taken in September to order a VAX 11/780 for TRIUMF users.An order for the system was placed in early October, and a March 31, 1981 delivery date has been promised. The configuration ordered has A MB of 32-bit MOS memory with battery backup; 2 RM05 256 MB 1.2 MB/sec disc drives; and 2 TU77 125 ips 800/1600 bpi tape drives. In addition, it will include two 6250 bpi tape drives, a printer/plotter, and a graph i cs termi na1.The facility will have 2A serial ports, with possibility for expansion in groups of 16, and hardware and software sufficient for a test of a high speed (DECNET) communication link with one PDP 11. It is expected that acquisition computers will be able to trans­fer files to the VAX using 9600 bd serial lines; however, the facility is not to be considered as a necessary part of any acqui­sition program.A VAX 'System Manager' will be hired to over­see the preparation of the plant, supervise installation and commissioning, and eventu­ally make the system as attractive as poss ible to a 11 users.105S oftw are  su p p o rt fo r data acq u is itio n  system sIn 1980 three man months of support were pro­vided for the development of the MRS data acquisition system. The site contribution to development in that system ended in the spring; however, it is expected that some software maintenance will continue to be pro­vided as needed.The major effort has been in the development and support of PDP 11 based data acquisition systems running the program MULTI under both RT-11 and RSC-ll/M operating systems.Several jobs have been undertaken, including implementation of user-requested modifica­tions to RT-11 MULTI; support of the I AC- approved Kinetics 3912 CAMAC Crate U con­troller under RT-11 MULTI; updating of the radioisotope production spectrum-former, with data transmission to the TRIUMF data inter­face; and implementation of MULTI operating under RSX-ll/M. The available histogram space under MULTI has been increased and a plot package added for PRINTRONIX printer/ plotters. A major thrust has been to speed up the acquisition portion as far as is possible.It is recognized that MULTI is not suitable for all experimental situations; however, limited manpower dictates that most of our effort be on this commonly used system.C om puting  fa c ilit ie s  a t TRIUMFIn April a standing committee on Computing Facilities at TRIUMF (CFAT) was established 'to recommend TRIUMF standards for all com­puter and peripheral equipment ... and data acquisition systems ... and to review all equipment purchases in the above categories'.Regular meetings of the committee were initi­ated in September. The committee is not a funding agency, but advises on the accepta­bility of specific computer and peripheral equipment purchases, with the objective of encouraging adherence to standards, and mini­mizing the number of different kinds of equipment used on site. A number of requisi­tions have been approved, or modifications suggested, and a number of memos and sugges­tions considered.By year's end the mandate of the committee was under review as a result of the uncertain attitude of the IEPGSC as regards funding of data acquisition systems.M W P C  F A C IL IT YThe multiwire proportional chamber facility at the University of Alberta produced several models of wire chambers for use in experi­ments at TRIUMF during the year. Currently two standard models of delay line readout chambers are produced: a 5" x 5" aperture chamber and an 8" x 8" aperture chamber.These chambers are read out using a printed circuit delay line with leading edge pulse detection and have a position resolution of typically ±0.3 mm. Two 12" x 12" aperture chambers were also produced this year which were scaled-up versions of the 8" x 8" aper­ture chambers. The 12" chambers worked but had poor resolution over the outer 2.5" of the wire plane. This loss of resolution was probably due to increased attenuation of the signal on the longer printed circuit delay line. It is believed that the performance of the 12" aperture chambers could be improved by either using a less dissipative delay line or by differentiating the delay line pulses and using zero crossing detectors rather than the leading edge detectors.Three spare helical chambers were wound for one of the UBC research groups, and some existing 5" x 5" and 5" x 10" aperture chambers were modified for one of the Uni­versity of Alberta groups. The 5" x 5" and 5" x 10" chamber modifications consisted of replacing wire cathode planes with foil cathode planes.A prototype retractable profile monitor was constructed for beam line kC .A prototype 60 cm chamber was constructed for Expt. 121. This chamber uses a wound wire delay line which is less dissipative than the printed circuit delay lines used on our smaller chambers. Position resolution of about ±0.3 mm could be obtained using differentiation followed by zero crossing detection or by using constant fraction dis­criminators on the delay line pulses. How­ever, leading edge detection of the delay line pulses produced poor results.Figure 92 shows the prototype 60 cm aperture chamber.The MWPC facility has two winding tables.The large table was used to wind the 60 cm chamber and can be used to handle chambers up to 1 m by 1.5 m in size. It was also used to wind the helical chambers for the UBC group. The smaller table is used for winding all chambers up to a 12" aperture.1 0 6Fig. 92. A prototype 60 am multiwire proportional chamber has been constructed at the University o f  Alberta. A delay line  readout system w ill  g ive a resolu tion  o f  0.3 mm. Several chambers w ill  even­tua lly  be used by the charge symmetry experiment (Expt. 121).S U P E R C O N D U C T IN G  S O L E N O ID  M A G N E T  S Y S T E MA solenoid with^a horizontal warm bore of 10 cm and an ^  3 • dJi of 2.2 T-m was speci f ied and ordered. This magnet will complement the BASQUE solenoid and will be used to pre- cess protons by 90° in beam line AB initial­ly and IB eventually. At year's end it had passed its factory test program and was being prepared for shipping.E X P E R IM E N T A L  A N D  B E A M  L IN E  M A G N E T SVarious designs and studies for experimental and beam line magnets were made during the year. These include:1) Procuring steel and recommissioning the 'C0M0S' magnet from Berkeley for Expt. 13A.2) Conceptual design of a neutron spin- precession dipole which will use the original coils M11B1 and be employed in the charge symmetry experiment.3) Design and procurement of two saddlecoils for the RF separator to be used in M 9 ,together with the steel yokes and pole plates .A) Design of two circular coils for the oldUBC Van de Graaff dipole.5) Rev iew and conceptual design for newcoils for the Resolution spectrometer in beam line IB.6) Design and fabrication of a short A-inch steering magnet for beam line 2C.7) A review and conceptual design of modifi­cations to M20B1 to reduce saturation. This requires new coils and pole pieces.L IQ U ID  H E L IU M  S U P P L YAn order was placed in 1979 for equipment to set up a helium liquefaction plant, complete with gas recovery and repurification facili­ties. The intention is to ensure an ade­quate supply of liquid helium for use in both the experimental program and cyclotron systems. The expander module of the lique- fier and an interim compressor were delivered in mid March and in production in late March. The compressor was very trouble­some, and after four major failures in 325 h of operation it was decided to cease repair­ing this'unit and wait for the delivery of the high capacity screw compressor which arrived on July 12 and was in operation by July 20. The expander module produces liquid at a rate of 21+ litres per hour which is slightly better than specified. A total of 8A20 litres were delivered to users from TRIUMF production.The recovery compressor was received in May, connected to the main building recovery sys­tem and high pressure storage. The manufac­turer has failed so far to deliver the puri­fier. Delivery is expected in the new year.107CONFERENCES, WORKSHOPS AND MEETINGSS E C O N D  IN T E R N A T IO N A L  T O P IC A L  M E E T IN G  O N  M U O N  S P IN  R O T A T IO N  (mSR2)The Second International Topical Meeting on Muon Spin Rotation, more economically known as 'ySR2', was held August 11-15 on the campus of the University of British Columbia with the support of Canada's Natural Sciences and Engineering Research Council, TRIUMF, the University of British Columbia and Simon Fraser University. The meeting attracted 111 participants from 10 countries: Canada,England, France, Germany, Italy, Japan,Mexico, Sweden, Switzerland and the USA.Several papers were submitted i n  a b s e n t ia  from the Soviet Union. There were 109 invited and contributed papers presented at the meet ing.The five-day span of the meeting was barely enough to accommodate all topics in a serial format. In order to enhance the endurance of the participants, sessions were held in the mornings, late afternoons and evenings, leav­ing early afternoons free for discussions and/or recreation. Most contributed papers were presented in the evening poster sessions. This approach seems to have preserved the strong cross-disciplinary exchange interaction traditional to ySR, despite the continued expansion of the field.In the two years since 'ySRl1 (Rorschach,1 9 78) there has been no obvious revolution in chemistry or physics brought about by ySR techniques. However, there have been several qualitative advances, and progress along certain lines seems to have accelerated encouragingly. The unique properties of muons as probes are better understood, the theories required for less ambiguous interpre­tation are considerably improved, and the connections between diverse results are more integrated. The reader of both proceedings will find that ySR2 includes more papers in which results from allied fields (NMR, ESR, PAC, etc.) have been combined with ySR results to reach a new and deeper understand­ing of phenomena. This is partly by design of the Organizing Committee, but is due mainly to the great success of ySRl in bring­ing together many research communities to share perceptions. The first meeting had the flavour of 'introductions'; at ySR2 we tasted the fruits of cross-disciplinary 'teamwork' at a more involved level. It is to be hoped that ySR3 (tentatively scheduled for 1982 inJapan) will similarly reflect evolution of the field in Vancouver this year.At ySR2 there were again several germinal papers from which new branches of ySR research may be expected to sprout. The ob­servation of 'helium coating' effects on the interactions of muonium (Mu) atoms with powder grain surfaces suggests possible applications of kSR to surface physics and chemistry. Use of rf driving fields in DEMUR (Double Electron-MUon Resonance) shows the way to elaborate and high-precision in­vestigations of hyperfine structure of para­magnetic states. Similar advantages accrue from the development of zero-field techniques for studying anisotropic hyperfine states (e.g., Mu in quartz at low temperature). The potential of zero-field relaxation studies, only hinted at in 1 9 7 8, has been vividly demonstrated by new results on spin glasses. Observations of unexpected muon motion in metals at ultra-low temperatures may provide the key to the riddle of quantum diffusion of light interstitials. And the observation of total flux trapping in superconducting vanadium, however fortuitous, remains tantalizingly unexplained.As after ySRl, one is left with the impres­sion that the most potent effect of ySR research is still the theoretical progress it seems to stimulate. Chemical reaction rates, for example, can be calculated ab i n i t i o  only in a few extremely simple cases, and the promise of a comparison between Mu + H2 ,H + H2 and D + H2 is an opportunity to push the theory beyond the scope of present ex­periments. The evolution of theories of electronic charge- and spin-densities around interstitial impurities in metals continues to be goaded forward by measurements of local fields and Knight shifts at muons in metals. Measurement of y" hyperfine anoma­lies have necessitated a more precise relativistic theory of electronic spin- densities in heavy muonic atoms. Muon motion (loosely termed 'diffusion') is apparently dominated at higher temperatures by impurity/ defect trapping in most metals— in fact, trap-quenching of the 'motional narrowing' of y+ relaxation is extraordinarily sensi­tive to minute impurities— but at tempera­tures below 2 K there is new evidence for1 0 8quantum effects, perhaps here uncluttered by impurity interactions. Theoretical treatments of muon motion have now set aside most of the crude approximations of the early days (Condon approximation, point-like muons, etc.) and seem to be converging on a complete quantum-mechanical picture of 'diffusion' of light interstitials. And the 'Kubo-Toyabe' stochastic theory of spin relaxation, compara­tively neglected for many years due to the lack of a probe capable of revealing the behaviour it predicts, has now become a powerful tool in several areas thanks to the development of zero-field pSR.'ySR technology' was a new explicit topic at ySR2, in recognition of the vital role experi­mental innovation has played in the progress of ySR. New developments, such as phase- coherent DEMUR, pulsed pSR and transversely polarized surface muon beams, are sure to stimulate new science at the same time as improvements upon 'old' technology, such as stroboscopic frequency measurements, zf-pSR and high time resolution, enhance the effi­ciency, reliability and versatility of the experimental apparatus.T R IU M F  M U O N  P H Y S IC S /F A C IL IT Y  W O R K S H O PThe workshop was held August 8-9 preceding the Second International Topical Meeting on Muon Spin Rotation held at the University of British Columbia the following week. The purpose of the workshop was to achieve an overview of some of the physics to be done with muons and to derive recommendations for the planning of future muon facilities at TRIUMF. The workshop was sponsored by TRIUMF and the TRIUMF Users Executive Committee.The topics and speakers were:Tests of unification models Muon captureMuonic molecules and atoms Muon spin polarization phenomena Muon properties, tests of QED, -oniums Muon decayR.E. Marshak J.G.P. Deutsch H. SchneuwlyT. YamazakiE. Zavattini A. S i rli nSadly, the workshop coincided within days of the death of Mike Pearce, one of its strongest supporters. Many of the workshop participants wished to attend a memorial service which conflicted with the original program, and the program was revised by dropping a discussion of facilities at TRIUMF.Informal discussions among users after the workshop were the basis of a summary of facilities presented at the November TUEC Annual General Meeting and two recommenda­tions were approved:1) TRIUMF has competitive surface muon beams now and should continue to support and further develop these.2) TRIUMF lacks, and needs, a channel capable of high stopping luminosity and highly polarized negative muons.The proceedings of the workshop will be issued as a TRIUMF report early in 1981.T R IU M F  U S E R S  G R O U P  A N N U A L  G E N E R A L  M E E T IN GAs has been customary, the TRIUMF Users' Annual General Meeting was scheduled by the Executive Committee (TUEC) immediately pre­ceding the November meeting of the Experi­ments Evaluation Committee (EEC).The agenda was divided into four sessions on the first day with an evening meeting at the UBC Graduate Student Centre. The second day closed after lunch to allow the EEC to start.Copies of written reports on facility devel­opment projects are available on request from TUEC.The meeting was well attended. Among the highlights were several talks on physics possibilities with kaon factories (now a perennial topic) in the Wednesday evening session, leading to approval by the users of the following statement regarding a kaon factory option:'The potential use of the existing TRIUMF cyclotron as the injector for a facility designed to produce an intense proton beam at energies up to 30 GeV is worthy of the urgent attention of both the TRIUMF staff and interested users. Any decision to pro­ceed beyond a feasibility study would in­volve the preparation of a detailed statement of both the scientific motivation for and technical feasibility of the project. Any such proposals should be circulated to all users for comment prior to submission to the government for the approval of major funding. The TRIUMF administration should be encouraged to take whatever steps are neces­sary to financially support a feasibility109study and to indicate to the government the possibility of a major request for additional funds within the next 5 years. The study of the feasibility of a kaon factory should be regarded as an incentive for those with alternative interests in the long-term devel­opment of TRIUMF to present their ideas for careful consideration by the community.1This statement helps to emphasize the poten­tial of a Users' Long-Range Planning Commit­tee in the evaluation of such major under­takings as a kaon factory.In 1980 the Canadian Association of Physicists conducted a survey of (among other things) intermediate-energy physics, at the request of federal funding agencies. The conclusions of this survey should be public in early 1981, and will presumably reflect discussions held at the AGM.E lec tion  o f TUEC fo r 1981Long-Range P lanning C om m itteeDiscussions in l979-80 led in 1980 to a proposal that TRIUMF users should form (through TUEC) a Long-Range Planning Commit­tee (LRPC). The reasons for this action, the terms of reference for such a committee, and its intended role are outlined in the initial proposal, which was approved by the users at the November AGM. Since then a charter has been written incorporating those principles and defining procedures. It is available on request from TUEC.Briefly, the LRPC will consist of 6 members appointed by TUEC, so that 2 will retire each year, and 3 members appointed by the TRIUMF administration. The LRPC will report to TUEC, who will transmit their findings to the users, to the administration of TRIUMF, and to the EEC. Proposals and/or enquiries may be placed before the LRPC by any TRIUMF user, either directly or through TUEC.The election of new TUEC members took place in the fall of 1980 and was announced at the November AGM. Members for 1981 are:The first meeting of the LRPC will be in spring of 1981.theJ.H. Brewer University of British Columbia Cha i rmanL.G. Greeniaus University of Alberta Assoc. Cha i rmanR. Abegg B.C. Robertson I.M . ThorsonP. SchmorUniv. of Alberta and TRIUMFQueen's UniversitySimon Fraser University andTRIUMFTRIUMF1 1 0ORGANIZATIONB o a r d  o f  M a n a g e m e n tThe Board of Management of TRIUMF manages the business of the facility and has equal repre­sentation from each of the four universities. At the end of 1980 the Board comprised:University of Alberta Dr. H.E. GunningDr. G .C . Ne i1 son Dean K.B. NewboundSimon Fraser University Dr. B.P. da ym an Dr. W. DeVries Dean J.M. Webster V ic e -C h a irm a nUniversity of Victoria Dean J.M. Dewey President H.E. Petch Dr . C .E . P icc iottoC hairm anUniversity of British Columbia Dr. K.L. Erdman Dean P.A. Larkin Mr. D. SinclairNon-voting members: Dr. R. Foxall, National Research CouncilDr. J.T. Sample, Director, TRIUMFDr. G.A. Ludgate, TRIUMF S e c re ta r yIn April, Dr. E.W. Vogt, Chairman of the Board since December 197^, stepped down, and the Board elected the University of Victoria's President H.E. Petch to serve as Chairman; in October Dr. Vogt resigned from the Board and at year's end Dr. K.L. Erdman replaced him as University of British Columbia member. Other changes during the year: The vacancy inUniversity of Victoria membership, following the death of Dr. R.M. Pearce, was filled by Dr. C.S. Picciotto. Dean K.B. Newbound of the University of Alberta relinquished the Honorary Secretaryship.The Board met five times during the year.O p e r a t in g  C o m m i t t e eThe Operating Committee of TRIUMF is responsible for the operation of the facility. It reports to the Board of Management through its chairman, Dr. J.T. Sample. It has four voting members, one from each of the four universities. The Associate Directors are non­voting members. The members of the committee (alternate members in parentheses) at the end of 1980 were:Dr. J.T. Sample C hairm an Di rectorDr. K.L. E rdman Associate Director, FacilitiesDr. B.D. Pate Associate Director, Applied ProgramDr. J.M. Cameron University of Alberta (Dr. G.A. Moss)Dr. R.G. Korteli ng Simon Fraser University (Dr. J.M. D'Auria)Dr. L.P. Robertson University of Victoria (Dr. G.R. Mason)Dr. M.K. C raddock University of British Columbia (Dr. J.H. Brewer)Dr. G.A. Ludgate S e c re ta r yChanges in 1980 were: J.M. Cameron succeeded G. Roy as University of Alberta member;Moss replaced J.M. Cameron as alternate member. M.K. Craddock succeeded G. Jones as University of British Columbia member and his place as alternate member was taken by J.H. Brewer.G.A.1 1 IT R IU M F  S a f e t y  A d v i s o r y  C o m m i t t e eThe TRIUMF Safety Advisory Committee (TSAC) has four standing subcommittees with membershi as defined below. The main TSAC consists of all standing subcommittee members as well as:Mr. I.M. Thorson C ha irm an TRIUMFDr. G.A. Ludgate S e c re ta r y  TRIUMFDr. G.D. Wait Head, TRIUMF Safety GroupDr. R.T. Morrison Director of Nuclear Medicine, VGHOperation Radiation Hazards Subcommittee:Mr. A.J. Otter C ha irm an TRIUMFDr. M.W. Greene B.C. Ministry of HealthMr. M. Zach TRIUMFDr. J.A. Macdonald TRIUMFMr. L . Mor i tz TRIUMFInduced Radioactivity Hazards Subcommittee:Dr. E.W. Blackmore C ha irm an TRIUMFMr. W. Rachuk Radiation Protection and PollutionControl Officer, UBC Dr. B.D. Pate TRIUMFMr. J.W. Carey TRIUMFMr. F. Szlavik TRIUMFM r . R . Tha11er AECLChemical Toxicity and Flammability Hazard Subcommittee:Mr. J.J. Burgerjon C ha irm an TRIUMFDr. J.B. Farmer Dept, of Chemistry, UBCDr. P. Percival TRIUMFMr. A. Bishop TRIUMFDr. D.R. Gill TRIUMFIndustrial Hazards Subcommittee:Mr. A. Johnson C ha irm an TRIUMFMr. S.C. Frazer (Observer) Workers' Compensation Board of B.C.Mr. T.D. Bulger (Observer) Workers' Compensation Board of B.C.Mr. L. Crozier TRIUMFMr. A. Hurst TRIUMFMs. Y. Langley TRIUMFA TSAC meeting consists of the first group above, together with the chairman of each of th subcommittees and as many of their subcommittee members as is required for the particular agenda in hand.E x p e r i m e n t s  E v a lu a t io n  C o m m i t t e eDr. F . KhannaDr. R .D. AmadoDr. A,. AstburyDr. A,,D. BacherDr. G -.A. BeerDr. R.,L. BurmanDr. J,. DomingoDr. K..P. JacksonDr. A..E . Li ther1 andDr. J..T. SampleDr. L.,D. SkarsgardDr. A.,W. ThomasDr. A., TurkevichDr. M., WalkerC ha irm anS e c re ta r yChalk River Nuclear LaboratoriesUniversity of PennsylvaniaRutherford LaboratoryIndiana UniversityUniversity of VictoriaLos Alamos Scientific LaboratorySINTRIUMFUniversity of Toronto TRIUMFB.C. Cancer Foundation TRIUMFEnrico Fermi Institute University of TorontoB i o m e d i c a l  E x p e r i m e n t s  E v a lu a t io n  C o m m i t t e eDr. L • D. Skarsgard C hairm an B.C. Cance r FoundationDr. M,• J. Ashwood-Smi th Un i ve rs ity of VictoriaDr. H .C. Johns Ontario Cainee r 1nst i tuteDr. R.. R. Johnson Un i vers i ty of British ColumbiaDr. A..E. L i ther1 and Un i vers i ty of TorontoDr. T.. R . Overton Universi ty of AlbertaDr. J,.T. Samp 1e TRIUMFDr. A.,W. Thomas TRIUMFDr. D.,C. W a 1ker Un i vers i ty of British ColumbiaDr. G..F. Wh i tmore Un i vers i ty of Toronto113Appendix APUBLICATIONSConference proceedings:D.A. Hutcheon, The (p,2p) and (p,d) reactions, Proc. Nuclear Structure with Intermediate Energy Probes Workshop, Los Alamos, January, LASL report LA-8303-C (1980), p. 220.[TRI-PP-80-3]J.M. Greben, Application of a unified theory of elastic and rearrangement scattering to l|He(p,d)3He, ibid., 402. [TRI-PP-80-2]A.N. Saharia and R.M. Woloshyn, ir°-photopro- duction in the isobar-doorway model, ibid., 423. [TRI-PP-8O-1]D.H. Boal, Clusters, nucleons and quarks in intermediate energy react ions,Proc. Interme­diate Energy Nuclear Chemistry Workshop, Los Alamos, June, LASL report (in press).[TRI-PP-80-19]M.K. Craddock, High intensity accelerators for kaon factories, Proc. 11th Int. Conf. on High- Energy Accelerators, Geneva, July (Birkhauser, Basel, 1980), p. 2A7. [TRI-PP-8O-13]D.A. Hutcheon, Elastic scattering of polarized protons at 200 to 500 MeV, Proc. 5th Int.Symp. on Polarization Phenomena in Nuclear Physics, Santa Fe, August, AIPCP#69 (in press).J.A. Niskanen, Polarization phenomena in (p ,tt) reactions, ibid.J.A. Edgington, The interpretation of recent measurements of np and pp cross sections,ibid.E.G. Auld, Polarization analyzing power mea­surements in coherent pion production by protons, ibid.G. Roy, L.G. Greeniaus, G.A. Moss, D.A. Hutcheon, R. Liljestrand, R.M. Woloshyn,D. Boal, A.W. Stetz, K. Aniol, A. Willis,N. Willis and R. McCamis, Inclusive scattering of protons on helium and nickel at 500 MeV, ibid.R. Abegg, J.M. Cameron, D.A. Hutcheon, R.P. Liljestrand, W.J. McDonald, C.A. Miller, L.E. Antonuk, C.E. Stronach and J.R. Tinsley,Search for the dibaryon bandhead, ibid.D.A. Hutcheon, J.M. Cameron, R.P. Liljestrand P. Kitching, C.A. Miller, W.J. McDonald, D.M. Sheppard, W.C. Olsen, G.C. Neilson, H.S. Sherif, R.N. MacDonald, G.M. Stinson, D.K. McDaniels, J.R. Tinsley, L.W. Swenson,P. Schwandt, C.E. Stronach and L . Ray, Elastic scattering of polarized protons at 200 to 500 MeV, ibid.G.J. Lolos, E.L. Mathie, P.L. Walden, E.G. Auld, G. Jones and R.B. Taylor, New aspects of the TRIUMF (p,ir) program, ibid.P. Kitching, L. Antonuk, C.A. Miller, D.A. Hutcheon, W.J. McDonald, W.C. Olsen, G.C. Neilson, G.M. Stinson and A.W. Stetz, Quasi­elastic lt0Ca(p,2p) scattering at 200 MeV at TRIUMF, ibid.R. Abegg, D.K. Hasell, W.T.H. van Oers, J.M. Cameron, L.G. Greeniaus, D.A. Hutcheon, C.A. Miller, G.A. Moss, R.P. Liljestrand,H. Wilson, A.W. Stetz, M.B. Epstein and D.J. Margaziotis, The reaction 2H(p,t)ir+ at 470 and 500 MeV, ibid.M.B. Epstein, D.J. Margaziotis, R. Abegg, D.K. Hasell, W.T.H. van Oers, J.M. Cameron, G.A. Moss, L.G. Greeniaus and A.W. Stetz, Asymme­tries from the 1+He(p,2p)3H reaction at 250 and 500 MeV using polarized protons, ibid.G. Roy, L.G. Greeniaus, D.P. Gurd, D.A. Hutcheon, R. Liljestrand, C.A. Miller, G.A. Moss, H.S. Sherif, J. Soukup, G.M. Stinson,H. Wilson and R. Abegg, Measurement of the de­polarization parameter D in elastic 9Be(p,p) scattering, ibid.H.W. Fearing, NN and NN interactions, Proc.9th Int. Conf. on the Few-Body Problem,Eugene, August, Nucl. Phys. (in press).[TRI-PP-80-25]C.A. Miller, The (p,2p) and (p,pn) reactions, ibid. [TRI-PP-80-26]J.M. Cameron, R. Abegg, I.J. van Heerden, D.A. Hutcheon, P. Kitching, W.J. McDonald, C.A. Miller, A.W. Stetz, J. Thekkumthala and H.S. Wilson, Study of the 2H(jD,y)3He reaction at Ep = 200-500 MeV, Contributed Papers, Few- Body Problem Conf. (Univ. of Oregon, Eugene, 1980), p. 32.H.W. Fearing, Comparison of (p,ir) and (p,y) reactions: pd->-3HeY, ibid., 39.A.W. Thomas, S. Theberge and G.A. Miller, The cloudy bag model, ibid., 97-M. Betz and T.-S.H. Lee, Influence of interac­tions in intermediate NNir states on NN scat­tering and ir+d p+p, ibid., 108.J.M. Greben, A.W. Thomas and A.J. Berlinsky, Quantum theory of hydrogen recombination, ibid., 141.J.M. Greben, A unified theory of elastic and rearrangement scattering, ibid., 142.114R. Dubois, R. Keeler, E. Auld, D. Axen,D. Bugg, A. Clough, M. Comyn, B. Dieterle,J. Edgington, G. Ludgate, J.R. Richardson,L. Robertson and N. Stewart, da/dfl (np^-np) and CTtotal from 220 to 495 MeV, ibid., 194.A. Gersten and A.W. Thomas, The one-pion- exchange nucleon-nucleon interaction in the cloudy bag model, ibid., 1 9 5-A.W. Thomas, The determination of nuclear matter densities using strongly interacting probes, Proc. Int. Conf. on Nuclear Physics, Berkeley, August, Nucl. Phys. (in press)[TRI-PP-80-22]A.W. Thomas, S. Theberge and B. Day, Bags, deltas and nuclear matter, Abstracts of Berkeley Conf., LBL report LBL-1118, p. 47.P. Kitching, L. Antonuk, C.A. Miller, D.A. Hutcheon, W.J. McDonald, W.C. Olsen, G.C. Neilson, G.M. Stinson and A.W. Stetz, Measure­ment of analyzing powers in quasi-elastic scattering, ibid., 64.D.A. Hutcheon, J.M. Cameron, R.P. Liljestrand, P. Kitching, C.A. Miller, W.J. McDonald, D.M. Sheppard, W.C. Olsen, G.C. Neilson, H.S.Sherif, R.N. MacDonald, G.M. Stinson, D.K. McDaniels, J.R. Tinsley, L.W. Swenson,P. Schwandt and C.E. Stronach, Proton elastic scattering at 200 to 500 MeV, ibid., 101.S. Ahmad, G.A. Beer, J.A. Macdonald, G.R.Mason, A. 01 in, R.M. Pearce, 0. Hausser and S.N. Kaplan, Search for the gamma decay branch of the shape isomer in muonic 238U, ibid., 369.S.N. Kaplan, A. Mireshghi, 0. Hausser,S. Ahmad, G.A. Beer, J.A. Macdonald, B.H. Olaniyi, A. Olin and R.M. Pearce, Nuclear fis­sion induced by atomic transitions of the muon in 235U and 238U, ibid., 370.S. Theberge, A.W. Thomas and G.A. Miller, The cloudy bad model of the pion-nucleon (3,3) resonance, ibid., 696.D.G. Fleming, R.J. Mikula and D.M. Garner, y + therma1ization and muonium formation in noble gases, Proc. 2nd Int. Topical Mtg. on Muon Spin Rotation, Vancouver, August, Hyperfine Interactions 8_ (in press).P.W. Percival, Muonium formation in water and aqueous solutions, ibid.P.W. Percival, The missing fraction in water,ibid.D.C. Walker, Arguments against a spur model for muonium formation, ibid.D.G. Fleming, D.M. Garner and R.J. Mikula, Temperature dependence of muonium reactionrates in the gas phase, ibid.Y.C. Jean, B.W. Ng, Y. Ito, T.Q. Nguyen and D.C. Walker, MSR applications to muonium reac­tivity in cyclodextrins, ibid.Y. Ito, B.W. Ng, Y.C. Jean and D.C. Walker, Effect of external electric fields on the ySR of liquid hydrocarbons and fused quartz, ibid.R.F. Kiefl, Thermalization of muonium in oxide powders at low temperatures, ibid.J.H. Brewer, Muonium in quartz, ibid.C.W. Clawson, K.M. Crowe and S.S. Rosenblum, Muonium states in silicon, ibid.J.H. Brewer, D.P. Spencer, D.G. Fleming and J.A.R. Coope, Muonium hyperfine matrix in quartz, ibid.C.W. Clawson, E.E. Haller, K.M. Crowe, S.S. Rosenblum and J.H. Brewer, Formation probabil­ities and relaxation rates of muon states in germanium, ibid.J.H. Brewer, E. Koster, A. Schenck, H. Schilling, D.L1. Williams, )j+SR studies in ant i ferromagnet i c CoC5,2 "2H20, ibid.J.H. Brewer, E. Koster, A. Schenck,H. Schilling and D.L1. Williams, p+ diffusion in single crystal AJCu(2%), ibid.M. Doyama, Comparison between positive muon research and positron annihilation in the study of crystalline effects, ibid.M. Doyama, R. Nakai, R. Yamamoto, Y.J. Uemura, T. Yamazaki, Y. Fukai and T. Suzuki, Behavior of positive muons in zirconium and vanadium hydrides, ibid.R. Nakai, M. Doyama, R. Yamamoto, Y.J. Uemura,T. Yamazaki and J.H. Brewer, Study of diffu­sion and trapping of positive muons in quenched aluminum by the trapping model, ibid.R. Yamamoto, R. Nakai, M. Doyama, T. Yamazaki,T. Masumoto and J.H. Brewer, Muon spin relaxa­tion in amorphous metals, ibid.Y.J. Uemura, J. Imazato, N. Nishida, R.S. Hayano, M. Takigawa and T. Yamazaki, Paramag­netic shift of u+ in MnO and its time dependence, ibid.Y.J. Uemura, Probing spin glasses with zero- field ySR, ibid.Y.J. Uemura, C.H. Huang, C.W. Clawson, J.H. Brewer, R.F. Kiefl, D.P. Spencer and A.M. de Graff, Zero-field ySR in an insulator spin glass (Co0)i+o (Al2 O3) 10 (SiO2 )50 , ibid.Y.J. Uemura, N. Nishida, J. Imazato, R.S. Hayano, M. Takigawa and T. Yamazaki, Longi­tudinal spin relaxation of p+ in MnO around115Neel temperature, i b i d .J.H. Brewer, y+SR with surface muon beams,i b i d .D.V. Bugg, The status of dibaryon resonances, Proc. 1980 Int. Symp. on High-Energy Physics with Polarized Beams and Polarized Targets, Lausanne (Birkhauser, Basel, in press)M. Comyn, D.C. Healey, G.A. Ludgate, D.A.Axen, R.L. Shypit, D.V. Bugg, J.A. Edgington, N.R. Stevenson, J.P. Stanley, N.M. Stewart, J.R. Richardson and R. Dubois, Measurements of Aoy, 0.66 GeV/c to 1.10 GeV/c, i b i d .M. Comyn and R.I.D. Riches, A microprocessor- based NMR system, i b i d .Journal publications:H.W. Fearing, Relativistic calculation of radiative muon capture in hydrogen and 3He, Phys. Rev. C 2]_, 1951 (1980) .[TRI-PP-79-37]H.W. Fearing, Comparison of proton-proton bremsstrahlung data at 42 and 156 MeV with soft photon calculations, Phys. Rev. C 22,1388 (1980) . [TR1-PP-79-40]R.S. Sloboda and H.W. Fearing, 0(l/m2) and nuclear effects in radiative muon capture in 40Ca, Nucl. Phys.'A340, 342 (1980).[TRI-PP-79-36]A.W. Thomas and R.H. Landau, Pion deuteron and pion-nucleon scattering, A review, Phys. Rep. 58, 121 (1980). [TRI-PP-79-23]G.A. Miller, A.W. Thomas, S. Theberge, Pion- nucleon scattering in the Brown-Rho bag model, Phys. Lett. 9J_B, 192 (1980) . [TRI-PP-79-16][RL0-1388-785]S. Theberge, A.W. Thomas and G.A. Miller, Pionic corrections to the MIT bag model: The (3,3) resonance, Phys. Rev. D 27, 2838 (1980).[TRI-PP-80-8]K. Kubodera, M.P. Locher, F. Myhrer and A.W. Thomas, Interference of dibaryon resonances with Faddeev amplitudes for elastic ttD scat­tering, J. Phys. G 6, 171 (1980).R.M. Woloshyn, PCAC and the non-relativistic pion-nucleon vertex, Nucl. Phys. A33&, 499 (1980). [TRI-PP-79-19]J.M. Greben and R.M. Woloshyn, Non-relativis- tic approximations to the pion production operator in LtHe(p,mr+)ItHe, Nucl. Phys. A3 33 , 399 (1980). [TRI-PP-79-9]A.N. Saharia and R.M. Woloshyn, Application of the isobar-doorway model to pion chargeexchange reactions, ( 1980).Phys . Rev. C 2]_, 11 1[TRI-PP-79-31]A.N. Kamal and J.N. Ng, Constraints on heavy- lepton mixings from deep inelastic charged lepton scattering, Phys. Rev. D 2_J_, 1224 (1980). [TRI-PP-79-32]D.H. Boal, Probing inclusive production mechanisms with the (p,2p) reaction, Phys.Rev. C 2 ± , 1913 (1980). [TRI-PP-79-33]M.B. Epstein, D.J. Margaziotis, J. Simone,D.K. Hasell, B.K.S. Koene, B.T. Murdoch,W.T.H. van Oers, J.M. Cameron, L.G. Greeniaus,G.A. Moss, J.G. Rogers and A.W. Stetz, Com­parison of the ltHe(p,2p)3H reaction at inter­mediate energies with the distorted wave impulse approximation, Phys. Rev. Lett. _44, 20 (1980). [TRI-PP-80-6]J. Kallne, A.N. Anderson, J.L. J. Rogers, D.A. Hutcheon and W Some dynamical aspects of pickBeveri dge,J. McDonald, •up reactions -500 MeV, Phys. [TRI-UAE-5027]studied in 13C(p,d)12C at 200 Rev. C 2 ± , 675 (1980).J.G. Rogers, J.L. Beveridge, D.P. Gurd, H.W. Fearing, A.N. Anderson, J.M. Cameron, L.G. Greeniaus, C.A. Goulding, C.A. Smith, A.W. Stetz, J.R. Richardson and R. Frascaria, Proton-proton bremsstrahlung at 200 MeV, Phys. Rev. C 22, 2512 (1980). [TRI-PP-80-11]P. Kitching, C.A. Miller, W.C. Olsen, D.A. Hutcheon, W.J. McDonald and A.W. Stetz, Quasi-free scattering of polarized protons, Nucl. Phys. A340, 423 (1980). [TRI-PP-79-34]G.A. Moss, L.G. Greeniaus, J.M. Cameron, D.A. Hutcheon, R.P. Liljestrand, C.A. Miller,G. Roy, B.K.S. Koene, W.T.H. van Oers, A.W. Stetz, A. Willis and N. Willis, Proton-4He elastic scattering at intermediate energies, Phys. Rev. C 21_, 1932 (1980). [TRI-PP-79‘35]E.G. Auld, R.R. Johnson, G. Jones, E.L.Mathie, P. Walden, D. Hutcheon, P. Kitching, W.C. Olsen, C.F. Perdrisat and B. Tatischeff, Differential cross section and analysing power for backward pions in 2H(p ,tt+)3H,Phys. Lett. 93B, 258 (1980). [TRI-UAE-5022]R.E.L. Green and R.G. Korteling, Fragment production from p + Ag interactions at inter­mediate energies, Phys. Rev. C 22, 1594 (1980)TTr 1-pp-79- 29]H. Dautet, G. Bischoff, J.M. D'Auria andB.D. Pate, Yield of deep spallation products of medium to heavy mass targets bombarded with 480 MeV protons, Can. J. Phys. jj8, 891 (1980). [TRI-PP-79-42]G.R. Mason, G.A. Beer, M.S. Dixit, S.K. Kim, J.A. Macdonald, A. 01 in, R.M. Pearce, W.C.116Sperry and J.S. Vincent, Pionic K X-rays in liquid 3He, Nucl. Phys. A340, 240 (1980).[TRI-PP-79-17]N.M.M. Al-Qazzaz, G.A. Beer, G.R. Mason,A. Olin, R.M. Pearce, D.A. Bryman, J.A. Macdonald, J.M. Poutissou, P.A. Reeve, M.D. Hasinoff and T. Suzuki, The TRIUMF stopped ir-p channel, Nucl. Instrum. Methods 174, 35 (1980). [TRI-PP-80-4]S. Ahmad, G.A. Beer, M.S. Dixit, J.A. Macdonald, G.R. Mason, A. Olin, R.M. Pearce,0. Hausser and S.N. Kaplan, Fission yields and lifetimes for muon-induced fission in 235U and 238U, Phys. Lett. 92B, 83 (1980).[TRI-PP-80-5]T. Suzuki, R.J. Mikula, D.M. Garner, D.G. Fleming and D.F. Measday, Muon capture in oxides using the lifetime method, Phys. Lett. 95B, 202 (1980). [TRI-PP-80-12]E. Mazzucato, B. Bassalleck, M.D. Hasinoff,T. Marks, J.M. Poutissou and M. Salomon, Phys. Lett. 96B, 43 (1980). [TRI-PP-80-1S]B.M. Barnett, W. Gyles, R.R. Johnson, K.L. Erdman, J. Johnstone, J.J. Kraushaar, S. Lepp, T.G. Masterson, E. Rost, D.R. Gill, A.W. Thomas, J. Alster, I. Navon and R.H. Landau, Proton radii determinations from the ratioof ir+ elastic scattering from 31B and 12C,Phys. Lett. 97B, 45 (1980) .A.S. Clough, W.R. Gibson, D. Axen, R. Dubois,L. Felawka, R. Keeler, G.A. Ludgate, C.J.Oram, C. Amsler, D.V. Bugg, J.A. Edgington,L.P. Robertson, N.M. Stewart, J. Beveridge and J.R. Richardson, Neutron-proton elastic scat­tering between 200 and 500 MeV. I. Experimen­tal details and measurement of the D^ and P parameters, Phys. Rev. C 2J_, 988 (1980).[TRI-PP-79-11]D. Axen, R. Dubois, R. Keeler, G.A. Ludgate,C.J. Oram, L.P. Robertson, N.M. Stewart,C. Amsler, D.V. Bugg, J.A. Edgington, W.R. Gibson, N. Wright and A.S. Clough, Neutron- proton elastic scattering between 200 and 500 MeV. II. Measurement of R^ and A t , Phys. Rev. C 2_j_, 998 (1980). [TRI-PP-79-12]D.V. Bugg, J.A. Edgington, W.R. Gibson,N. Wright, N.M. Stewart, A.S. Clough, D. Axen,G.A. Ludgate, C.J. Oram, L.P. Robertson, J.R. Richardson and C. Amsler, Neutron-proton elastic scattering between 200 and 500 MeV.III. Phase-shift analysis, Phys. Rev. C 21, 1004 (1980). [TRI-PP-79-13]D.C. Walker, Dynamics of electron localiza­tion, J. Phys. Chem. 8h_, 1140 (1980).D.C. Walker, Y.C. Jean and D.G. Fleming,Reply to the time-scale of intraspur muonium formation, J. Chem. Phys. J2_, 2902 (I98O).Y.C. Jean, B.W. Ng and D.C. Walker, Chemical reactions between muonium and porphyrins,Chem. Phys. Lett. _75, 561 (1980).Y. Ito, B.W. Ng, Y.C. Jean and D.C. Walker, Muonium atoms observed in liquid hydrocarbons, Can. J. Chem. 5 8, 2395 (1980).Y.J. Uemura, T. Yamazaki, R.S. Hayano,R. Nakai and C.Y. Huang, Zero-field spin re­laxation of y+ as a probe of the spin dynamics of ^\uFe and CuMn spin-glasses, Phys. Rev.Lett. 45, 583 (1980).Y.J. Uemura, Zero-field muon spin relaxation reflecting dynamics of spin glass, Solid State Commun. _36, 369 (1980) .R.S. Hayano, Y.J. Uemura, J. Imazato, N. Nishida, K. Nagamine, T. Yamazaki, Y. Ishikawa and H. Yasuoka, Spin f1uctuations of itinerant electrons in MnSi studied by muon spin rota­tion and relaxation, J. Phys. Soc. Jpn. 49,# 5  ( 1 9 8 0 ).M. Takigawa, H. Yasuoka, Y.J. Uemura, R.S. Hayano, T. Yamazaki and Y. Ishikawa, Positive muon spin rotation and relaxation studies in the helically ordered state of MnSi, i b i d .Preprints and in press:H.W. Fearing, Pion production in nuclei:Things known and unknown (Prog, in Particle & Nuclear Physics, in press). [TRI-PP-80-27]A.W. Thomas, S. Theberge and B. Day, A new saturation mechanism for nuclear matter (sub­mitted to Phys. Rev. Lett.). [TRI-PP-8O-7 ]G.A. Miller, A.W. Thomas and S. Theberge, Pionic corrections in the MIT bag model (Com­ments Nucl. Part. Phys., in press).[TRI-PP-80-33]A.N. Saharia and R.M. Woloshyn, Isobar-doorway model for coherent Tr°-photoproduct ion (Phys. Rev. C, in press). [TRI-PP-80-15]A.N. Saharia, R.M. Woloshyn and L.S.Kisslinger, Pion-nucleus optical potential in the isobar-doorway model (Phys. Rev. C, in press). [TRI-PP-80-30]D.H. Boal and R.M. Woloshyn, The role of direct emission in strong and electromagnetic- ally induced inclusive reactions (Phys. Rev.C, in press). [TRI-PP-80-23]0. Shanker, Muon number violation in some horizontal gauge theories (Phys. Rev. D, in press). [TRI-PP-80-32]117J.N. Ng, On the connection between neutrino oscillations and pion decay (Phys. Lett., in press). [TRI-PP-80-9]J.N. Ng, Low energy consequences of inter­mediate mass neutrinos in ir^ 2 decays, solar neutrino fluxes and neutrino oscillations (submitted to Nucl. Phys. B) . [TRI - PP—80— 3^ + ]J.M. Greben, A unified theory of elastic and rearrangement scattering (submitted to Phys. Rev. C). [TRI-PP-80-10]G. Roy, L.G. Greeniaus, G.A. Moss, D.A. Hutcheon, R. Liljestrand, R.M. Woloshyn, D.H. Boal, A.W. Stetz, K. Aniol, A. Willis,N. Willis and R. McCamis, Inclusive scattering of protons on helium, nickel and tantalum at 500 MeV (Phys. Rev. C, in press).[TRI-PP-80-2AD.H. Boal, R.E.L. Green, R.G. Korteling and M. Soroushian, Tests of models for inclusive production of energetic light fragments at intermediate energies (Phys. Rev. C, in press).[TRI-PP-80-28]A. Olin, P.R. Poffenberger, G.A. Beer, J.A. Macdonald, G.R. Mason, R.M. Pearce and W.C. Sperry, Measurement of pionic and muonic X-rays in 10>n B (Nucl. Phys. A, in press).[TRI-PP-80-14]D.E. Lobb, Beam optical properties of the magnetic field produced by two coaxial cables (submitted to Nucl. Instrum. Methods).[TRI-PP-80-31]B. Bassalleek, F. Corriveau, M.D. Hasinoff,T. Marks, D.F. Measday, J.M. Poutissou andM. Salomon, The observation of charge exchange of pions captured in several nuclei (Nucl.Phys. A, in press). [TRI-PP-80-17]C.J. Oram, J.B. Warren, G.M. Marshall and J. Doornbos, Commissioning of a new low-energy iT-p channel at TRIUMF (Nucl. Instrum. Methods, in press). [TRI-PP-80-16]R.F. Kiefl, J.B. Warren, G.M. Marshall, C.J. Oram and C.W. Clawson, Muonium in the con­densed phases of Ar, Kr and Xe (J. Chem.Phys., in press). [TRI-PP-80-20]R.F. Kiefl, J.B. Warren, C.J. Oram, G.M. Marshall and C.W. Clawson, Surface interaction of muonium in oxide powders at low tempera­tures (submitted to Phys. Rev. Lett.).[TRI-PP-80-21]V.L. Highland, M. Salomon, M.D. Hasinoff,E. Mazzucato, D.F. Measday, J.-M. Poutissou and T. Suzuki, Branching ratios for stopping pions in deuterium (submitted to Nucl. Phys. A). [TRI-PP-80-35]J.S. Vincent, A .H . Dougan, D.L. Lyster and J.W. Blue, A facility for the production of 123I by spallation of caesium (submitted to J. Radioanalytic Chemistry). [TRI-PP-80-29]Reports:C.J. Oram, J.B. Warren, G. Marshall,J. Doornbos and D. Ottewell, Ml 3 beam line tun i ng [TRI-80- 1 ]Report on Workshop on Prospects for high resolution studies with a proton beam between Ep = 200-500 MeV, October 5-6, 1979, eds.J.M. Cameron, P. Kitching and D.A. Hutcheon[TRI-80-2]H.W. Fearing, A bibliography and summary of data for the (p,ir) reaction: p+A •> it+(A+1)[TRI-80-3]D. Bryman, Some physics possibilities for the kaon factories [TRI-80-A]1 1 8Appendix BUSERS GROUPUniversity of Alberta. University of Victoria:R. Abegg* G.C. Neil son S. AhmadE .B . Ca i rns A.A. Noujaim G.A. BeerJ.M. Cameron W.C. Olsen G.B. FriedmannW.K. Dawson G . Roy T.A. HodgesJ.B. Elliott D.M. Sheppard A.D. KirkJ. Greben H . Sheri f D.E. LobbL.G. Greeniaus J. Soukup G.R. MasonP . Ki tch i ng R.C. UrtasunW.J. McDonald H . W i1 son*G.A. MossUniversity of British Columbia:Simon Fraser University A.S. Arrott D. Boal J.M. D 1Aur i aJ .H . B rewer J.R. Ledsome B .L . Fun t[Chairman 1981] G. Ma rsha 1 1 R. GreenE.G. Auld P.W. Mart inD.A. Axen C.A. McDowel 1D.S. Beder J.M. McMi1lanM.K. Craddock D.F. Measday TRIUMF:C.F. Cramer C. Oram K.P. JacksonR . Dubo i s B.D. Pate* [Cha i rman 1980]F. Entezami M. Salomon R. BaartmanK.L. Erdman* J . Sams M. BetzD .G . FIeming J. Trotter J.L. BeveridgeD. Garner E.W. Vogt E.W. BlackmoreM.D. Hasinoff D .C . W a 1ker B . B 1ank1e i derR.R. Johnson C.E. W a 1tham C.W. BordeauxG. Jones J.B. Warren W.J. BryanR. Kief 1 B .L . Wh i te D.A. Bryman"'at main site VancouverM. Comyn D.A. Dohan J. DoornbosB.C. Caneer FoundationG. DuttoH.W. Fear i ng D.R. Gi11K.Y. Lam D.P. GurdL.D. Skarsgard D.A. HutcheonM.E.J. YoungT C . J . Ko s tI'B.C. Canoer Control AgencyR. LeeG.A. LudgateVisiting experimentalists based at main site:G. Azuelos, R. Poutissou, Universite de Montreal W. Falk, H.P. Gubler, D.K. Hasell, University of Manitoba J. Tinsley, University of Oregon1 19T. Numao*B . 01 a n i y i *A. 01 in*C.E. P i cc iotto P.A. Reeve* L.P. Robertson C.S. WuS.D. Hanham C.H.W. Jones R .G . Korte1i ng P.W. Percival I.M. Thorson.A. Macdonald i.H. Mackenzie .A. Mi 1ler . N . Ng . Niskanen . Ottewel1 -M Poutissou .G. Rogers . Rosenthal .T. Sample . Schmor . Shanker .E. Spuller .W. Thomas •K. Verma . S . Vi ncent .D. Wait . Walden . Waters . Woloshyn . ZachOther institutions:CanadaC.Y. Kim, S. Rowlands, University of Calgary T. Walton, Cariboo CollegeA.L. Carter, Carleton UniversityG.A. Bartholomew, J.S. Fraser, O.F. Hausser,F.C. Khanna, H.C. Lee, A. McDonald, Chalk River Nuolear LaboratoriesJ.W. Scrimger, S.R. Usiskin, Cross Canoer Institute, Edmonton P.A. Egelstaff, University of GuelphB.S. Bhakar, J. Birchall, A. Bracco, N.E. Davison, M.S. de Jong, J. Jovanovich,R. McCamis, W.T.H. van Oers, University of ManitobaB. Margolis, S.K. Mark, L. Yaffe, McGill University P. Depommier, J-P Martin, Universite de MontrealM.S. Dixit, C. Hargrove, Rational Research CouncilH. Blok, Novatrack Analysts LimitedG.T. Ewan, B.C. Robertson, Queen’s University M. Krel1, Universite de Sherbrooke T.E. Drake, University of Toronto R.T. Morrison, Vancouver General Hospital W.P. Alford, University of Western OntarioOverseasD.V. Bugg, R. Gibson, Queen Mary College, LondonN.M. Stewart, Bedford College, LondonA.S. Clough, University of SurreyA.N. James, University of LiverpoolC. Amsler, A. Astbury, R. Keeler, C. Sabev,CERNR. Engfer, Universitat ZurichJ. Domingo, E.L. Mathie, A. Schenck, SINS. Jaccard, Universite de NeuchatelR. Grynszpan, CNRS VitryR. van Dantzig, IKO AmsterdamM. Furic, Inst. R. BoskovicJ. Alster, D. Ashery, Tel-Aviv UniversityB.K. Jain, Bhabha Atomic Research Centre R. Hayano, K. Nagamine, K. Sakamoto,T. Yamazaki, University of Tokyol.R. Afnan, Flinders University of South AustraliaUnited StatesK.W. Jones, Brookhaven National LaboratoryF.P. Brady, University of California, DavisB.M.K. Nefkens, J.R. Richardson, University of California, Los Angeles M.P. Epstein, D.J. Margaziotis, California State UniversityB. Bassal leek, L. Wolfenstein, Camegie- Mellon UniversityJ.J. Kraushaar, T. Masterson, University of ColoradoH.S. P1 end 1 , Florida State University M.E. Rickey, P. Schwandt, T. Ward, Indiana University Y.K. Lee, Johns Hopkins University P. Tandy, Kent State UniversityC. Clawson, K.M. Crowe, G. Gidal, S. Kaplan, R.H. Pehl , V. Perez-Mendez, S. Rosenblum, M.W. Strovink, R. Tripp, Lawrence Berkeley LaboratoryJ.W. Blue, Lewis Research Center, NASA L.E. Agnew, H.L. Anderson, C.A. Goulding, R.J. Macek, Los Alamos National Laboratory R.P. Redwine, Massachusetts Institute of TechnologyH.B. Willard, National Science FoundationB. Dieterle, University of New Mexico J.K. Chen, State University^ of N.I. Geneseo K.K. Seth, Northwestern UniversityF.E. Bertrand, Oak Ridge National LaboratoryB.C. Clark, Ohio State UniversityD.K. McDaniels, University of Oregon K.S. Krane, R. Landau, A.W. Stetz, L.W.Swenson, Oregon State University R.F. Carlson, University of RedlandsG.S. Mutch 1er, Rice UniversityR. Bryan, R.B. Clark, Texas A&M University V.G. Lind, R.E. McAdams, O.H. Otteson, Utah State University K. Ziock, University of Virginia M. Blecher, K. Gotow, D. Jenkins, Virginia Polytechnic Institute and State UniversityI. Halpern, E.M. Henley, P. Wooton, University of WashingtonA.S. Rupaal, Western Washington University W.C. Sperry, Central Washington UniversityC.F. Perdrisat, R.T. Siegel, College of William and MaryH. Bichsel T.C. Sharma1 2 0Appendix CEXPERIMENT PROPOSALSThe following lists experiment proposals received up to the end of 1980 (missing numbers cover proposals that have been withdrawn, replaced by later versions, or combined with another pro­posal). Page numbers are given for those experiments which are included in this annual report.Page1. Low-energy pi nuclear scatteringR.R. Johnson, University of British Columbia [Completed] 233. The study of fragments emitted in nuclear reactionsR.G. Korteling, Simon Fraser University [Completed] 2h6. Studies of the proton- and pion-induced fission of light to medium mass nuclidesB.D. Pate, University of British Columbia [Completed]9. A study of the reaction if" + p +  y + n at pion kinetic energies from 20-200 MeVD.F. Measday, University of British Columbia [Active] lA10. Positive pion production in proton-proton and proton-nuc1eus reactionsG. Jones, University of British Columbia [Active] 2611. Nuclear spectroscopic studies of short-lived radioactive products of high energy reactionsJ.M. D'Auria, Simon Fraser University [Active]lA. The interaction of protons with very light nuclei in the energy range 200-500 MeVG.A. Moss, University of Alberta [Completed]15- A proposal to study quasi-free scattering in nucleiW.J. McDonald, University of Alberta [Completed]18. Influence of chemical environment on atomic muon capture ratesR.M. Pearce,*University of Victoria [inactive]19. Nuclear decays following muon capture R.M. Pearce,*University of VictoriaE.D. Earle, Chalk River Nuclear Laboratories [inactive]20. Isotope effect in p captureR.M. Pearce*University of Victoria [Inactive]21. Optical activity induced by polarized elementary particlesD.C. Walker, University of British Columbia [Active]22. Negative pion capture and absorption on carbon, nitrogen and oxygenH.B. Knowles, Washington State University) [Passed to Biomedical EEC]23. Study of decay modes a) ir° -* 3y > b) 7T+ e+ + ve + y, c) tt+  -* i t 0  + e+ + veP. Depommier, Universite de Montreal [Completed]2A. Elastic scattering of polarized protons on 12CG. Roy, University of Alberta [Completed]26. Measurement of the differential cross-section for free neutron-proton scattering and for the reaction D(n,p)2nL.P. Robertson, University of Victoria [Completed] 1627. Measurement of the polarization in free neutron-proton scatteringD.A. Axen, University of British Columbia [Completed]35. A study of positive muon depolarization phenomena in chemical systemsD.G. Fleming, University of British Columbia [Active]A0. A proposal for neutron experiments at TRIUMFD.A. Axen, University of British Columbia [Completed]Ala. Radiative capture of pions in light nucleiM. Salomon, University of British Columbia [Completed] 1^121Page42a.42b.46.47.48. 52. 53-54.55.56.57.58.59.6 0.61 .65.66. 70.71 •72.4 l b .73-Charge exchange of stopped negative pionsM.D. Hasinoff, University of British Columbia [Completed]ir~-3He: Strong interaction shiftG.R. Mason, University of Victoria [Completed]ir”-3He: Neutron-neutron scattering lengthG.R. Mason, University of Victoria [Deferred]Hyperfine splitting in polarized muonic 209Bi atomsG.T. Ewan, Queen's University [inactive]Photon asymmetry in radiative muon captureM.D. Hasinoff, University of British Columbia [inactive]Ferti1e-to-fissi1e conversion in electrical breeding (spallation) targetsI.M. Thorson, Simon Fraser University [Active]A measurement of the tt -* ev branching ratioD.A. Bryman, TRIUMF-University of Victoria [Completed] 16Emission of heavy fragments in pion absorption P.W. Martin, University of British ColumbiaD.R. Gill, TRIUMF [Active]tt— reaction cross-section measurements on isotopes of calciumR.R. Johnson, University of British Columbia [Active]y- capture in deuterium and the two-neutron interactionJ.M. Cameron, University of Alberta [inactive]A study of the decay of the muonD.F. Measday, University of British Columbia [Pending]Search for the y+ -*■ e+ + y decay modeP. Depommier, Universite de Montreal [Completed]Polarization effects of the spin-orbit coupling of nuclear protonsP. Kitching, University of Alberta [Completed]Investigation of the (p,2p) reactions on 3He, 3H and 4HeW.T.H. van Oers, University of Manitoba [Completed]Study of muonium formation in MgO and related insulators and its diffusion into a vacuumJ.B. Warren, University of British Columbia [Completed] 55Pre-clinical research on the i t -  beam at TRIUMFL.D. Skarsgard, B.C. Cancer Foundation [Active] 5&Radiosensitivities of tumours in situ to ir-meson irradiationK. Sakamoto, University of Tokyo [Pending]Survey of p-p bremsstrahlung far off the energy shellJ.G. Rogers, TRIUMF [Completed]Proton total cross-section and total reaction cross-section measurements for lightnucleiW.T.H. van Oers, University of ManitobaR.F. Carlson, University of Redlands [Deferred]Muon spin rotation projectT. Yamazaki, M. Doyama, R. Hayano, K. Nagamine, University of TokyoD.G. Fleming, University of British Columbia [Active] 44Solid-state studies by muonic X-ray polarizationK. Nagamine, University of Tokyo [Completed]Artificial muon polarizationK. Nagamine, University of Tokyo [Active]1 2 274. Proposal to measure D, R and R' in pp scattering, 200 to 520 MeVD.V. Bugg, Queen Mary College [Completed]75. The d(p,ir+ )t pion production reaction for high momentum transferW.C. Olsen, University of Alberta [Completed]77. Evaporation-cooled metallic cesium target assembly for production of 123iJ.W. Blue, NASA Cleveland [Active]78. Importance of defects in p+SR in metalsT. Yamazaki, University of Tokyo [Active]79. Low-energy tt production as a function of energy at 500 MeV and belowL.P. Robertson, University of Victoria [Completed]80. Measurements of pionic X-ray energies, widths and intensitiesR.M. Pearce* Un i vers i ty of Victoria [Completed]8 3. Bound muon decay in nucleiM.D. Hasinoff, University of British Columbia [Active]84. The (tt± , d) reaction on light nucleiR.R. Johnson, University of British ColumbiaT.G. Masterson, University of Colorado [Completed]86. Elastic and inelastic scattering of polarized protons from calcium and leadD.A. Hutcheon, TRIUMF [Active]8 7. Proton radiography studies at TRIUMFE.W. Blackmore, TRIUMF [Active]88. Systematic studies of total muon capture ratesT. Yamazaki, University of Tokyo [Active]8 9. u fissionS.N. Kaplan, Lawrence Berkeley Laboratory [Active]91. Muonium in semiconductorsJ.H. Brewer, University of British Columbia [Active]93- Production of radioisotopes at medium energies for pure and applied researchJ.S. Vincent, TRIUMF [Active]96. Spin dependence in pp pmr+D.A. Axen, University of British Columbia [inactive]97- Rare electromagnetic decays of pionic atomsM.D. Hasinoff, University of British Columbia [Completed]98. The detection and characterization of the heavy partner in fragmentation reactions R.G. Korteling, Simon Fraser University [Active]99. Studies of (p,d) reaction in nucleiJ.M. Cameron, University of Alberta [Active]101. Investigation of (tt,2tt) reaction [Letter ofG. Jones, University of British Columbia Intent]102. Absolute cross-sections of 12C (tt* ,ttN) 1*C reactions at low energyR.G. Korteling, Simon Fraser University [Inactive]103. Search for target spin dependence in proton elastic scatteringG. Roy, University of Alberta [Active]104. The time projection chamber - A new facility for the study of decays of muons and p i onsD.A. Bryman, TRIUMF-University of VictoriaC.K. Hargrove, National Research Council [Active]105. Backward inclusive scatteringG. Roy, University of Alberta [Active]5947292930173159Page31332 0123Page107.1 0 8. 110. 111.113.114.115.117.1 1 8 .119.120. 121 .122.123-124.125-126.127.128.129.130.1 0 6. New proposal for a pey experiment .J-M Poutissou, TRIUMF [Inactive]Study of the (p.dir) reactionJ. Kallne, University of Virginia [Active]Meson cascade studiesR.M. Pearce ,* Un i vers i ty of VictoriaMicrodosimetry of ir” beam at TRIUMFA. Ito, University of Tokyo [Active]Study of the absorption of it" at rest in ^He, 3Be, ^2C, 11>N and ^ 0C. Cernigoi, University of Trieste/INFN Legnaro [Active]A proposal for 3He(p,p)3He at backward anglesJ.M. Cameron, G.A. Moss, University of Alberta _ [Active] 34W.T.H. van Oers, University of Manitoba, J. Kallne, University of VirginiaThe (p,2p) reaction on 4He and 3HeW.T.H. van Oers, University of Manitoba [Active] 35Neutral pion production from 209Bi at intermediate proton energiesJ.M. D'Auria, Simon Fraser University [Completed] 35Single particle inclusive spectra of light fragments over their entire energy rangeR.G. Korteling, Simon Fraser University [Active] 24A study of (w,2N) reactions on light nuclei R.R. Johnson, University of British ColumbiaB. Bassa11eck, Carnegie-Mel 1 on University [Active] 23Small angle scattering of thermal neutrons for the study of magnetism and liquid crystals .A.S. Arrott, Simon Fraser University LActiveJA study of the production and decay of 11Be with intermediate-energy protons K.P. Jackson, TRIUMF [inactive]Test of charge-symmetry in n-p scattering G.R. Plattner, University of BaselW.T.H. van Oers, University of Manitoba [Active] 22A ySR investigation of dipolar fields in cobaltA.S. Arrott, Simon Fraser University [Active]Observation of e+ channeling from stopped y+ in a crystalline hostA.S. Arrott, Simon Fraser University [Completed]Excitation of giant multipole resonances by intermediate energy protonsF.E. Bertrand, Oak Ridge National Laboratory [Active] 36Proton-proton bremsstrahlungJ.G. Rogers, TRIUMF [Inactive]Measurement of the line shape of pionic X-raysA. 01 in, University of Victoria [Deferred]Measurement of the strong interaction shift in pionic deuteriumG.A. Beer, University of Victoria [Active] 29Variation of muonic X-ray intensities with atomic numberG.R. Mason, University of Victoria [Active]Quasielastic pion scattering at resonance energies for light T=0 nuclei R.R. Johnson, University of British ColumbiaA.I. Yavin, Tel-Aviv University [Deferred]The energy dependence of the polarization parameter in proton-proton scatteringD.A. Axen, University of British Columbia [Completed] 16124131. A study of (p,y) reactions on 3H and 6Li at intermediate energiesJ.M. Cameron, University of Alberta [Active] 36132. Measurement of the differential cross section of the reaction pp dir+ between lab proton energies of 325 to 500 MeVP.L. Walden, TRIUMF [Active]131*. Measurement of the eta parameter in muon decayK.M. Crowe, Lawrence Berkeley Laboratory [Active] 22135. A measurement of the 4He(p, mr+)4He reactionA.W. Thomas, TRIUMF [Letter ofW.C. Olsen, University of Alberta Intent]136. Production and detection of pi-oniumJ.B. Warren, University of British Columbia [Active]137- Lifetime of the positive muonM. Eckhause, College of William and Mary [Active]138. Surface muon studies of germaniumK.M. Crowe, Lawrence Berkeley Laboratory [Active] A2139. Macroscopic diffusion of positive muons in aluminumK.M. Crowe, Lawrence Berkeley Laboratory [Active]1 AO. Transfer effects for stopping tt- in H2 -D2 mixturesD.F. Measday, University of British Columbia [Active] 15lAl. Muonic hydrogen at STP - A feasibility studyJ.H. Brewer, University of British Columbia [Completed]1A2. A study of the single scattering mechanism for non-evaporative fragment emissionR.G. Korteling, Simon Fraser University [Active] 2A1A3. A study by recoil detection of proton-induced reactions on 9BeK.P. Jackson, TRIUMF [Active] 371AA. Studies of (^,d) reactions in nucleiJ.M. Cameron, University of AlbertaJ.J. Kraushaar, University of Colorado [Active]1A5. The neutron and gamma-ray correlation in the negative pion capture in18lr31Ho and 181TaY-K Lee, Johns Hopkins University [Active]1A6. Measurement of the small angle n-p differential cross section from 200-500 MeV G.A. Ludgate, TRIUMF [Deferred]IA7 . The formation and reactivity of muonium in the gas phaseD.G. Fleming, University of British Columbia [Active] Ag1A8. A direct measurement of the muonium hyperfine splitting in silicon at 77°KC.J. Oram, University of British Columbia [Active]IA9 . ySR studies of phase transitionsM. Doyama, University of Tokyo [Active] A8150. Utilization of backward muons to study muonium reaction intermediatesP.W. Percival, Simon Fraser University [Active] 36151. Interaction of muons with fissile nuclides IIA. Olin, University of Victoria [Active]152. Measurement of the spin rotation parameter R in p_l*He elastic scatteringG.A. Moss, University of Alberta [Active] 38153. Elastic scattering of protons from 3HeW.T.H. van Oers, University of Manitoba [Active]125155.156.157.158.159- 160. 161 . 162 . 16**.165.166.167.168. 169 -170.171. 173- 17**.175.176.177.15**. Muon i um i n soli dsJ.H. Brewer and D.G. Fleming, University of British ColumbiaStudy of deep hole states 40 Ca with (p,2p) reactionP. Kitching, University of AlbertaDeuteron production in proton-nuc1eus collisions J.M. Cameron, University of Alberta J. Kallne, University of VirginiaThe chemistry of muonium atoms in condensed media D.C. Walker, University of British ColumbiaStudy of the reactions p2H -> dn+n and p3He -> tir+pJ.M. Cameron, University of AlbertaC.F. Perdrisat, College of William and Marypp and pd interactions at thresholdB.L. White, University of British ColumbiaStudies of some ternary magnetic superconductors with muonsC.Y. Huang, Los Alamos Scientific LaboratoryStudies of spin dynamics of some amorphous spin glasses with muonsC.Y. Huang, Los Alamos Scientific LaboratorySurvey of X-ray production of high-energy protons K.W. Jones, Brookhaven National LaboratoryMeasurement of the 1/E dependence in (p,n) reactions J.M. D'Auria, Simon Fraser UniversityCross sections and analyzing power measurements of giant resonances for incident 200-500 MeV protonsD.K. McDaniels, University of OregonNeutron-nuclear structure with pionsR.R. Johnson, University of British ColumbiaD.R. Gill, TRIUMFBackward ttP and irD scatteringR.R. Johnson, University of British Columbia2S muonium production from thin foilsC. Oram, University of British ColumbiaProton elastic scattering from oxygen-16D.A. Hutcheon, TRIUMFFission-evaporation competition in heavy nuclei at intermediate energies P. Kitching, University of Alberta B.D. Pate, TRIUMFTest of T-invariance in pp scattering D.A. Hutcheon, TRIUMFMeasurement of pionic **-3 X-ray transitions in heavy nuclei A. Olin, University of Victoria[Act i ve][Inact i ve][Deferred] [Act i ve][Act i ve] [Act i ve] [Act i ve] [Act i ve] [Act i ve] [Act i ve][Act i ve][Act i ve] [Act i ve] [Act i ve] [Act i ve][Acti ve] [Act i ve] [Act i ve]Spin dependence of the pp -*■ pn ir+ reaction D.A. Axen, University of British Columbia [Act i ve]An investigation of inclusive one pion production in proton nucleus collisions R.M. DeVries and N.J. DiGiacomo, Los Alamos Scientific Laboratory [Active]Measurement of the parameter E in the muon decay K.M. Crowe, Lawrence Berkeley LaboratoryProton radius determinations for C, N and 0 R.R. Johnson, University of British Columbia[Act i ve] [Act i ve]h i38Page53391 2 6178.179.180. 181 . 182.183.184.185.Nuclear radius studies in the Ca regionR.R. Johnson, University of British Columbia [Active]Studies of the (p,t) reaction on 12C, 51tFe and 208Pb at 175 and 225 MeVJ.J. Kraushaar, University of Colorado [Deferred]Electric quadrupole moments from the measurement of muonic X-raysG.R. Mason, University of Victoria [Deferred]Measurement of the Is strong interaction shift in pionic hydrogenG.A. Beer and B. Olaniyi, University of Victoria [Active]Measurement of the n-p spin correlation parameter using a polarized beam and polarized target [Letter ofW.T.H. van Oers, University of Manitoba Intent]Inelastic pion scatteringD.W. Storm, University of Washington [Deferred]Investigation of the p + 2H -+ 3H + ir+ reaction from 275 to A50 MeV using polarized protonsG. Jones, University of British Columbia [Active]Precise measurement of the polarization parameter A search for the effects of a right-handed gauge boson in y+ decayM. Strovink, University of California, Berkeley/LBL [Active]Page*deceased127

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