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

Annual report scientific activities, 1982 TRIUMF Jun 30, 1983

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TRIUMFANNUAL REPORT SCIENTIFIC ACTIVITIES 1982MESON F A C I L I T Y  OF:U N I V E R S I T Y  OF A L B E R T A  S I M O N  F R A S E R  U N I V E R S I T Y  U N I V E R S I T Y  OF V I C T O R I A  U N I V E R S I T Y  OF B R I T I S H  C O L U M B I ATRIUMFANNUAL REPORT SCIENTIFIC ACTIVITIES 1982TRIUMF4004 WESBROOK MALL VANCOUVER, B.C. CANADA V6T 2A3PRODUCT IONCYCLOTRONI N T E R I MR A D I O I S O T O P ELABORATORYNEUTRON ACT  I VAT I ON A N A L Y S I SB L 2 C ( p)B L l B ( p )MESON HALLM9 ( i r/y )M 2 0 ( u )B L I ABATHOB I O M E D I C A L - LABORATORYTHERMAL  NEUTRON FAC I L I T YFO R E W O R DThis annual report describes the first full year of operation of TRIUMF as initially envisaged. The thirty-six weeks of scheduled operation and the doubling of delivered beam are reflected in the high morale of the project, in the amount of science which is emerging and in the length of this annual report.Clearly the high priority being given to cyclotron reliability is beginning to pay off. The TRIUMF cyclotron is a very large and complex machine which requires high precision adjustments and fine tuning. It is very satisfactory that the cyclotron maintenance and operations personnel (often overlooked when the kudos flow to science output) are able to keep the cyclotron operating round the clock for weeks at a time with minimal maintenance periods and un­scheduled shutdowns.The science output has been impressive at all of TRIUMF's various beam lines. With its variable-energy, high-quality proton beams TRIUMF has completed the very important survey of the fundamental force between nucleons. With its muons and pions a number of very interesting experiments were completed or are under way. Only a few of these address questions which existed when TRIUMF was initiated but they do now place TRIUMF at the forefront of subatomic science.The progress in science is epitomized by the remarkable accomplish­ments of the applied program. The positron emission tomograph (PET) was completed and the isotope pipeline installed. In pion therapy the first sixteen patients with deep-seated tumours were treated, and there now appears to be no impediment to major clini­cal trials using this new therapy tool. This is a major change in outlook. A year ago it looked as though pion therapy could not proceed without a costly new channel. With a concatenation of minor improvements and with smooth cyclotron operation at high intensities over extended periods, the intended goals have become possible.The TRIUMF Board of Management experienced the completion of Howard Petch's term as chairman. He has been of immense help to the project in his many years of service on the Board.vTRIUMF was established in 1968 as a laboratory operated and to be used jointly by the University of Alberta, 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 programme 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 factory'.Fields of research include basic science, such as medium- energy nuclear physics and chemistry, as well 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 treatmentThe 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 full-energy beam in 1974 and its full current in 1977.The laboratory employs approximately 355 staff at the main site in Vancouver and 17 based at the four universities.The number of university scientists, graduate students and support staff associated with the present scientific pro­gramme is about 300.C O N TE N TSINTRODUCTION 1SCIENCE DIVISION 3Introduction 3Particle Physics 5ir~p ■+ 711 and 7r“p •> ir°n 5Systematic studies of total muon capture rates 5Search for muon electron conversion 6Test of charge symmetry in n-p elastic scattering at 500 MeV 9Total cross-section differences in pp elastic scattering 10Pion production 12Measurement of the n parameter in muon decay 13Lifetimj; of the positive muon 13pp and pd interactions at threshold 142S muonium production from thin foils 15pp ->- pmr+ 16Precise measurement of the polarization parameter E, 18Nuclear physics and chemistry 19Absorption at reat of negative pions in 12C 19Elastic scattering of polarized protons from % e  at inter­mediate energies 21Study of %e(p,2p)d and %e(p,pd)p quasi-free scattering 22Fragments 23Giant resonances 23Strong interaction shift in pionic deuterium 24Radiative capture of polarized nucleons 24Non-evaporative fragment emission 25A study by recoil detection of proton-induced reactions on 9Be 25A measurement of the Wolfenstein R parameter in p-^He elasticscattering at 500 MeV 26Quasi-elastic scattering of polarized protons at 300 MeV 27Fission-evaporation competition in heavy nuclei 28Broad pionic X-rays 28pd -»• tir+ 29Pion production from 10B 29P,tt radiochemical study 30A survey of pion double charge exchange at low energies 30A study of (p,n) and related reactions 30The particle and y-ray correlation in the tt~ and p- capturesin medium-heavy nuclei 31In search of a tredecabaryon resonance 33The 2H(p,2p)n reaction and momentum distribution of thedeuteron 34Pion absorption and scattering 34Research in chemistry and solid-state physics 38Transfer effects for stopping tt“ in H2~D2 mixtures 38Formation and reactivity of muonium in gases 38Utilization of backward muons to study muonium reactionintermediates 43The chemistry of muonium atoms in condensed media 45Studies of some ternary magnetic superconductors with muons 46Amorphous spin glasses 47Muons and muonium on surfaces 47viiTheoretical program 49Introduction 49Meson-nucleus interactions 49Few-nucleon systems 50Nuclear reactions 53Electromagnetic reactions 53Quark models and QCD 56Theoretical chemistry 58Weak interactions and grand unification 58General topics in theoretical physics 60High energy physics 61APPLIED PROGRAMS DIVISION 62Programs 62Biomedical program 62TRIM program 65Positron emission tomography 65Radioisotope processing (AECL) 66Neutron activation analysis (Novatrack) 66Facilities 67500 MeV isotope production facility 6742 MeV cyclotron 67Beam line 2C 69Biomedical channel upgrade project 69CYCLOTRON DIVISION 70Introduction 70Beam production 73Cyclotron 73Cyclotron development 73RF system 78Probes and diagnostics 81Vacuum 82Ion sources and injection system 82Primary beam lines 84Thermal neutron facility 85Control system 86Operational services 88EXPERIMENTAL FACILITIES DIVISION 92Introduction 92Experimental support 94Data acquisition systems and CFAT 94Nucleonics and IAC 96Detector facility 96Wire chamber facility 97Meson hall 97Mil channel 97M13 low-energy ir-y channel 98QQD spectrometer 98M9 and RF separator 99M20 channel 101M20 improvements 101Beam line IB and Resolution spectrometer 102Beam line 2A 102Beam line 2C 102viiiProton hall 102Beam line 4A 102Beam line 4B 102Neutron facility 103MRS operation and upgrade 103Second arm spectrometer 104Targets 105Experimental facilities engineering 106ACCELERATOR RESEARCH DIVISION 110Beam development 112Cyclotron 112Primary beam lines 113Secondary channels 116Beam line diagnostics 117Computing services 119Kaon factory studies 120TECHNOLOGY DIVISION 133Introduction 133Site services 133Safety program 133Building program 136Mechanical engineering 137Planning 137Controls, electronics and computing 138Electronics development 138Electronics shop 141VAX computing centre 141CONFERENCES, WORKSHOPS AND MEETINGS 143ORGANIZATION 145APPENDICESA. Publications 148B. Users Group 154C. Experiment Proposals 156ixIN TR O D U C TIO N1982 has been, for TRIUMF, the first year of full operation as a science project. The amount of beam produced was that initially envisaged for the project and more than double the amount for any preceding year.All of the experimental programmes originally planned for TRIUMF are now under way. This annual report is intended to describe, brief­ly, the new experimental results emerging and the progress made on the accelerator and the experimental facilities.The past decade of accelerator design and construction, of cyclotron improvement, of experimental facility development and of ini­tial facility operation was prologue to the period of full operation just begun. During 1982 there were 36 weeks of cyclotron operation - about 24 weeks of high intensity operation (normally at about 100 yA beam current integrating to 229 mAh for the year) and 12 weeks of polarized running. Neither the total number of weeks of operation nor the 1:2 split between polarized and high intensity running are likely to change very significantly in the coming years. Further increases in meson production will require higher average beam currents.The very successful year just completed has been, in part, the result of greater atten­tion to cyclotron reliability which remains the highest project priority. The efforts of the Cyclotron Division towards higher reli­ability - both for 1982 and for the future - are described in the report of that division. It was not a year without machine traumas.At the beginning of the year the failure of a trimming coil in the most awkward location and towards the end of the year the inadvert­ent introduction of pump oil into a vital section of the injection line challenged the ingenuity of the operations team. In between there were many other events of comparable interest and challenge. But it was, in short, a year of magnificant recoveries from the incidents which occurred. The cyclotron again showed that it is capable of operating sweetly over extended periods.Cyclotron Division also accomplished a great deal towards future reliability. The mysteries of RF leakage inside the tank are being dispelled. Main magnet stability is greatly improved. Step by step a new resonator system is emerging, a third ion source is being developed, and higherpolarized beam intensities are being achieved.The development of secondary beam lines and major experimental facilities is described in the report of the Experimental Facilities Division. In recent years TRIUMF has changed from a facility with only meager facilities to one with a very interesting and competi­tive system of beam lines. The M13 beam line, completed a little over a year ago, is the best in the world for many experiments involving pions and muons. The continuous improvement of existing facilities and the development of new ones is essential if a project like TRIUMF is to retain its competi­tive edge.In 1982 three facilities projects were completed. The RF separator of M9 was essen­tial to the very significant progress made on one of TRIUMF's most important experiments - the pursuit of muon conversion with the time projection chamber (TPC). The Mil line, although begun earlier than M13, was com­pleted and provides beam for many additional pion and muon experiments. The 2C beam line (70-110 MeV protons) has provided valuable new facilities for isotope production.Decisions on new facilities are the end- product of a complex process. Initial ideas for facilities come from the pressure of experiments or from fresh ideas about future experiments as articulated by the TRIUMF Users Long Range Planning Committee. It is the responsiblity of TRIUMF's administration, in consultation with the Operating Committee, to prepare the rolling TRIUMF Five-Year Plan which requires approval by TRIUMF's Board of Management before its annual submission to NRC's Advisory Board on TRIUMF (ABOT).The elements of the current Five-Year Plan are described in the report of the Experimen­tal Facilities Division. Of key importance at present is the progress on the new M20 beam line (now nearing completion for muon spin resonance research) and on the various elements of the medium resolution spectrom­eter (MRS). Also, design and planning is under way for the new M15 muon beam line and for a second arm of the MRS.Prospects are very bright for the new MRS, expected to come into operation in 1983. It will provide 70 keV resolution, with variableenergy (180-520 MeV) and good polarized beams. This is a unique combination spanning an energy window of great current interest for nuclear physics.The focus in this annual report is on the science which has emerged. A few touchstones here are intended only to convey the extent of the body of work reported by Science Division.The very important initial survey of the nucleon-nucleon interaction at intermediate energy (BASQUE) was completed. This was an eight-year program involving scientists from many different institutions and with much new technology. Its very significant results are contained in a series of 13 scientific publi­cations .The muon conversion experiment with the TPC exceeded the previous world limit for muon conversion in nuclei. This is one of the most fundamental experiments in subatomic physics. It should reach its goals in 1983. The development and operation of the TPC is a major technological achievement.The experiment (#185) by a Berkeley group on the Michel parameters in muon decay appears to have achieved its experimental goals in 1982. When analysed, early next year, this data will set important new limits on the possible existence of any right-handed gauge bosons.The low energy pion group made a great deal of progress in 1982 in commissioning the QQD spectrometer (provided by Julich) and in ini­tial experiments involving pions of several tens of MeV energy interacting with atomic nuclei. Because of their long mean free paths such pions are particularly promising for nuclear physics.The applied program at TRIUMF achieved major milestones in three different programs. The CP42 cyclotron for isotope production (100 pA beams of variable energy up to 42 MeV) came very close to achieving production status. Meanwhile the 2C beam line produced commer­cial quantities of several isotopes. The positron emission tomograph (PET) wascompleted and moved to its new site in the nearby imaging centre at the Walter Koerner Acute Care Hospital. A pipeline to speed short-lived TRIUMF isotopes to the imaging centre - a distance of over 2 km - was installed. Finally, a magnificent beginning was made on pion therapy for human subjects. The first 16 patients with deep-seated tumours were treated, as described in the report of the Applied Science Division. More importantly, it was shown that the pion therapy program of the M8 beam line was capable of treating many dozens of patients per year in 1983 and beyond, which should make possible a proper clinical trial of this important new therapy tool.The work in accelerators and physics for a kaon factory continued to be the main interest of Accelerator Research Division. This is a convergent process of great impor­tance to the future physics of TRIUMF.A new Sixth Division was created in 1982 to aggregate TRIUMF's electronics effort and various other site services. Strong elec­tronics development for both the cyclotron and experiment remains of crucial importance for the project.New buildings appear and trailers remain.The remote handling building was completed in 1982 and TRIUMF's new machine shop building was begun and nearly completed. Office and work space congestion remains endemic while a major debate on buildings for new proton facilities persisted through much of the year. Perhaps the vitality of the project in 1982 is best measured by the constructive tension about new possible facilities. If so, 1982 was a very good year and 1983 should be even better.Significant changes in TRIUMF's management included the departure from TRIUMF's Board of Management of five members who have contrib­uted many years of splendid service. Howard Petch, John Dewey, David Sinclair, William DeVries and Kenneth Newbound helped to guide the TRIUMF joint venture into its present vigour. New members welcomed to the Board are John McDonald, John Cochran, Morris Belkin, Lyle Robertson and Alfred Fischer.2S C IE N C E  D IV IS IO NINTRODUCTIONFifty experiments received beam during the past year of which twenty completed the data acquisition phase. Twelve new proposals were reviewed by the Experiments Evaluation Committee at the July meeting and fourteen in December. In addition to Canadian users, spokesmen of visiting groups represent such institutions as Central Research Institute for Physics, Budapest, College of William and Mary, Indiana University's Cyclotron Facility, Japan Society of Science, Johns Hopkins University, Lawrence Berkeley Labora­tory, Los Alamos National Laboratory, University of Melbourne, University of Michigan, Northwestern University, University of Oregon, Oak Ridge National Laboratory, Tel-Aviv University, University of Tokyo, University of Trieste and University of Washington. In a reciprocal way one experi­ment (Expt. 159) is a test of equipment by a TRIUMF group collaborating in an antiproton experiment at CERN.The unique feature of the negative ion accelerator is the ability to extract multiple beams each simultaneously and inde­pendently variable in energy and intensity. Experiment 130, the measurement of the total cross-section differences Ao^Ac^ using the variable energy polarized beam and polarized target is the last of a series of elastic nucleon-nucleon scattering experiments. Analysis of TRIUMF data combined with data from LAMPF, SIN and Saclay has produced a set of unique phase shifts up to 800 MeV. This range of energies covers the range of ener­gies at which individual nucleons interact within nuclei. The spin dependence of the inelastic reaction pp ■+• pir+ was studied in Expt. 174. The next generation of nucleon- nucleon experiments includes a test of the basic assumption of charge symmetry of nuclear forces (Expt. 121) and precision measurements of the differential cross section and analysing power in the inelastic reactions np -*■ dy (Expt. 190) and the brems- strahlung experiment pp ppy (Expt. 208) both below the energy for significant pion production.The energy dependence of pion production in the NN interaction has been studied by measuring the differential cross section and angular distribution in the fp •+■ ir+d reaction (Expts. 132, 192). At the same time preci­sion data (±0.6%) for pp elastic scattering at 90° c.m. have been obtained, which are in excellent agreement with similar data obtained independently at other laboratories. Pion production in composite nuclei has been studied in Expt. 184 (j&l tir+) using the medium resolution spectrometer and Expt. 187 10B(i?, ir+) 1 *B using the spectrometer on beam line IB.Elastic scattering of polarized protons from light nuclei has been studied in Expts. 113, 114, 131, 152 and 153. The 3He data will be analysed in terms of the new nucleon-nucleon scattering amplitudes. The recent p+d -*■ 3He+y data are in excellent agreement with new results from Bates on the inverse reaction yt-3He p+d. This agreement resolves a long­standing puzzle in reaction rates which indi­cated evidence for an unexpected violation of time reversal invariance. Other proton- induced nuclear reaction studies using the variable energy feature include quasi-elastic scattering from individual nucleons in 1+0Ca (Expt. 155), a study of giant dipole resonances in 208Pb (Expts. 124, 165), a study of the competition between two decay processes of excited nuclei, fission and neutron evaporation (Expt. 170), a study of the fragmentation process following proton bombardment (Expts. 117, 142, 143), a study of pion production in heavy nuclei using radiochemical techniques (Expt. 189), and a search for resonant structure (Expt. 212).The high intensity extracted beam is operated mainly at one energy (500 MeV) and one inten­sity (100 yA) for pion production. The high intensity, low energy pion and muon fluxes that have recently become available have been exploited to solve a number of longstanding experimental problems and for a number of new experiments. The Panosky ratio = (ir-p -> ir°n)/(TT-p yn) at rest would be expectedto be the ratio of the square of the stronginteraction coupling constant to the electro­magnetic coupling constant. The pion nucleon interaction is basically a p-wave interaction, forbidden at rest, which reduces the ratio to1.5. For pions in flight this kinematicalrestriction no longer applies, as shown in the results of Expt. 9.Experiment 104 is a search for muon number violation in the reaction u"+T-[ *  e”+T-£.3Although In the standard electroweak theory such reactions do not occur, many extensions of the simplest model allow measurable rates. The time projection chamber built for this experiment is in full operation. Experi­ment 168 is a measurement of the Lamb shift in muonium, a unique system composed of two point particles with no finite size effects.A pion cannot be absorbed by a single nucleon with simultaneous conservation of both energy and momentum. Absorption is therefore assumed to involve a correlated nucleon pair. The excitation energy spectrum of the residu­al nucleus in the 12C( ir- ,nn) 10B (Expt. Ill) shows clearly the nuclear shell structure. Both p-p and p-n coincidences from ir+ and Tt- absorption in flight by 3He were measured to compare absorption on T=0 and T=1 nucleon pairs (Expt. 199). Particle/y-ray correla­tions in tt- and p- captures in medium mass nuclei were observed in Expt. 211.As the observed ratio of pion-nucleon cross sectiong( T+p) = <  TT~n) = 9 o( tt~p) a( n+n)is so large tt+ elastic scattering experi­ments are sensitive probes of proton distributions in nuclei and tt- scattering experiments of neutron distributions. This technique has been exploited in Expt. 166 to measure neutron radii in 32S, 3I+S and 2ltMg,26Mg and proton radii in 12C, 11+N and160, 180 (Expt. 177).Pionic X-rays are shifted and broadened from that calculated from purely electromagnetic interactions due to the extra nuclear inter­action. At the large distances involved thenuclear interaction is weaker than the electromagnetic so that the nuclear effect is a perturbation. Experiment 127 is an attempt to precisely measure (1 eV) the k a energy in pionic deuterium and extract the pion nucleon scattering lengths. In Expts. 173 and 196 a Compton suppression system was used to suppress background and observe the 4-3 transition in 288Pb and 289Bi.Experiment 185 is a precision experiment (0.001) of the Michel parameter ? describing electron spectra of muon decay. This experi­ment will also give a limit on the minimum allowed mass of possible right-handed gauge bosons. Such particles have not been observed as yet.Experiments 88 and 140 are new experiments designed to study the effect of chemical environment on negative pion absorption.Muon decay kinematics is such that the electron is emitted in the direction of the muon spin. Muons stopped in a region of magnetic field precess with a characteristic Larmor frequency which can be determined from the precession of the direction of the decay electron. In this way muons are used to measure intermolecular magnetic fields.Expt. 164 is an application of pSR technique to study properties of amorphous spin glasses, Expt. 160 a study of superconduc­tors, and Expt. 190 a study of crystalline surface. Positive muons also interact with atomic electrons to form muonium which, if in the triplet state, precesses at 200 times the free muon rate. Experiment 147 is a study of the formation and reactivity of muonium in gases and Expt. 150 a study of muonium formation in frozen aqueous solutions.4PARTICLE PHYSICSExperiment 9 j t - p - ^ y n  and n~p -*~x°nThe data-taking for this experiment was com­pleted during a 3-week run on Mil in August. There are now results for pion energies of 50, 65, 80, 95, 110 and 125 MeV. A short run at A3 MeV was also taken as a check on abso­lute normalization to compare with our earlier data on M13. We have obtained the y- ray spectra every 15° from 45° to 145° with some poor data at 30° as well, but these may be unusable because of the high count rate from the muon halo in the beam.The data at the higher energies were taken with a small collimator (15 cm <j>) for TINA, to improve the energy resolution. An example of a Y-ray spectrum is given in Fig. 1 for T,, = 125 MeV. The peak from radiative capture is still clearly separated from the charge exchange, but careful spectral fitting will be needed to obtain a precise cross section.It was felt that higher pion energies should await an improved y-ray detector.In order to improve the energy resolution of TINA it has been decided to send the crystal back to Harshaw, for recompensation with a 6 MeV y-ray source. This has been very successful for a Nal crystal produced by them for A. Sandorfi at Brookhaven National Labora­tory. It is expected that TINA will be returned by the end of the shutdown to start work again in April 1983.A draft paper has been completed about the earlier work on M13 at 27.4 MeV and 39.4 MeV. The results were discussed in last year's annual report. The only major change is that now there is a better understanding of the disagreement between our results on the charge exchange cross section and the phase- shift analysis of Zidell e_t al_. From conver­sations with Arndt, who was at TRIUMF in the summer, it now appears that the analyses, published in that paper, were restricted to tt“p data. A new "combined" analysis includes w+p data as well and the agreement with our cross sections is quite satisfactory.The data for higher pion energies is now being analysed and will form the Ph.D. thesis of A. Bagheri. Present indications are that there will be no undue difficulty in signifi­cantly improving on existing data for both the tt~p * yn capture reaction and the ir-p * ir°n charge exchange reaction.Experiment 88 Systematic studies o f total muon capture ratesIn an experiment to measure the lifetime of the y~ in various elements it was found that if a compound was used the data also gave information on the atomic capture ratios, i.e. in a substance such as CdO one could determine how often the p~ reached the cadmium nucleus and how often it reached the oxygen nucleus. The first crude estimate is the well-known Fermi-Teller Z law, i.e. that in this case the atomic capture probability would be expected to be W(Z/0) = 48/8 or 6 whereas experimentally it is ~3.6. Not only is the Z-law inaccurate but there are also fluctuations as a function of Z, which corre­late with atomic structure.Some of the earliest experiments were also done by the so-called "lifetime technique", but later experiments normally used informa­tion from the mesic X-ray spectrum. In these experiments one is comparing X-rays with quite different energies, and the efficiency of the detector can vary over a range of 50:1, so it was felt that it would be worth pursu­ing the other technique because it has such different systematic errors.A first attempt was published some time ago [Suzuki at_ al^ ., Phys. Lett. 95B, 202 (1980)] but soon thereafter it became clear that there had been an error in the data analysis due to an incorrect definition of t=0. This meant that the atomic capture ratio for the heavier elements was too low. A recent experiment has been conducted taking greatG A MM A - R A Y  ENERGY ( c hanne l s )Fig. 1. Energy spectrum for 125 MeV pions.5DE NS IT Y ( g / c m 3 ) ATOMIC NUMBER OF METALFig. 2(a). Atomic capture ratio for muons in Fig. 2(b). Atomic capture ratio for muons inoxides vs. density. Data appears monotonic. oxides vs. about the definition of t=0 as well as taking more precautions about the carbon background.A preliminary analysis of the recent data has been completed and some examples are given in Table I, with a comparison to the mesic X-ray data of von Egidy et al. and of our earlier publication. It is clear that we are now in better agreement with the other method, although a systematic difference still remains.During the analysis of our data, it was noticed that the capture ratio is a monotonic function of the density whereas it exhibits strong fluctuations when plotted against Z (the publications by von Egidy et al. and by Suzuki et al. have the mandatory plot against Z). This is illustrated in Fig. 2 for our data on monoxides. (The situation becomes too confused if the other oxides are included.) We illustrate the capture ratio against p and against Z, and it is clear thatthe single point moves into line (it is SrO which is anomalously low).Further runs are anticipated in 1983 to com­plete measurements on all available oxides. These data will constitute the M.Sc. thesis of S. Stanislaus.Experiment 104 Search fo r muon electron conversionThe mystery of the multiple generations of fundamental particles continues to present one of the major challenges in physics.There are at least three lepton generations, or flavours, which have in common a set of remarkable features. These include:1) identical electromagnetic interactions, as evidenced by the spectacular agreement of experiments and theory on the values for electron and muon anomalous magnetic moments,Table I. Atomic capture ratios of muons in oxides.Oxide von Egidy Suzuki New data11 Na 20 2 0.99 ± 0.05 0.87 + 0.02 0.99 + 0.0312 MgO 0.89 + 0.05 0.80 + 0.02 0.93 + 0.0422 Ti02 2.74 + 0.14 2.17 + 0.11 2.81 + 0.0629 CuO 3.26 + 0.23 4.06 + 0.23 4.31 + 0.2248 CdO 3.31 + 0.39 1.93 ± 0.07 3.83 + 0.2082 Pb02 5.03 + 0.58 3.21 + 0.23 6.9 + 0.362) identical weak interactions embodied in tests of electron-muon universality in the branching ratio of ir->ev/ir+yv,3) absence of strong interactions,4) symmetry in the generation structure with the quark sector as required for the cancel­lation of anomalies,5) absence of flavour-changing interactions, such as y-»ey, y-+nucleus + e”+nucleus, K+ye and T+yy, and6) existence of a conserved additive lepton number for each generation, as evidencedby searches for neutrinoless double-beta decay.These features of the lepton families are incorporated in the Weinberg-Salam-Glashow (WSG) unified gauge theory of weak and electromagnetic interactions. This is a one- generation model and in spite of its extraordinary success in describing observed weak and electromagnetic phenomena, there are still important unanswered questions. Many of these are related to the lepton generation puzzle. Open problems include the neutrino mass spectrum which has important cosmologi­cal implications, lepton mixing and neutrino oscillations, CP violation, and the fundamen­tal relationships between quarks and leptons within each generation and between the generations themselves.The concept of muon number conservation has been developed due to the apparent absence of reactions, such as y + ey, y“+nucleus e-+ nucleus known as muon-electron conversion, and v^N -*■ eX and K ye.As mentioned earlier, there is good reason to doubt that a fundamental conserved quantum number is associated with each lepton generation. However, in the standard WSG model muon number is absolutely conserved if the masses of all the neutrinos are identically zero.Stringent limitations on alternative models derived from muon-electron conversion and other lepton number violating processes have been discussed by Shankar [Phys. Rev. D 23, 1955 (1981)]. For example, under certain as­sumptions the present limits indicate that the mass of horizontal gauge bosons may be M > 3000 Mw . Stringent limits on the scale of lepton substructure can also be derived [Lyons, Oxford report 52/82 (1982)].The experimental search for muon-electron conversion using the TRIUMF time projection chamber has now begun. After teething problems with the new RF separator in the M9 muon channel were solved, data collection commenced in the summer. The RF-separated muon beam has a flux of ~106 y“/s at 74 MeV/c with a pion contamination <2 x 10-1+ and an electron contamination ~10% at the experimen­tal target.The TRIUMF TPC shown in Fig. 3 consists of a large volume drift region with a central high voltage plane located in a uniform magnetic field. The ionization electrons from a charged particle track drift to either end of the drift region where they are detected by a proportional wire system which measures the x,y and z coordinates of up to twelve track segments.The principle of operation of the TPC is as follows. A charged particle traverses the active volume of the chamber, and leaves a track of ionization. The ionization elec­trons from this track drift towards an end cap under the influence of the electric drift field. As the drifting track reaches the end cap, a segment of it passes through a slot into one of the proportional wire regions.The position of the entrance slot determines the y coordinate. The electrons in this segment are amplified by gas avalanche near the anode wire; the charge produced on the anode induces a corresponding charge on theFig. 3. Isometric view of the TRIUMF TPC.7Fig. 4. The measured resolution a in the TPC as a function of the crossing angle.cathode. The cathode is segmented in the direction of the wire, and the distribution of charge on the segments (pads) is measured and used to deduce the position of the track segment along the anode wire, giving the x coordinate. The drift time of the track segment to the wire is used along with the known drift velocity in the gas to give the z coordinate. From this information, the track, a circular helix, is reconstructed and the momentum calculated. The amplitude of the anode signal is used to determine the energy loss (dE/dx) of the particle that produced the track.One of the central features of any experiment is a thorough understanding of the apparatus. Since this is one of the first TPCs, we have spent considerable effort in detailing the operational characteristics of the device and in arriving at a quantitative description of the observations. A full discussion of the results can be found in Mes et al. [in prepa­ration] and Hargrove et_ al. [Proc. Int. Conf. Colliding Beam Physics, SLAC-250, 41 (1982)].The observed spatial resolution (Fig. 4) of the TPC at TRIUMF has been shown to depend on the drift length and crossing angle of the track, and on the magnetic field. A formula­tion has been developed, which reproduces the observed resolution. It takes account of discrete nature of the ionization deposited along the track and the charge distribution induced on the cathode pad readout system.The parameters of the formulation are measurable physical properties of the gas, or are chamber-dependent quantities which can be calculated.The equation for the resolution has the form:62 = C 2 + C2 ----— -0 Ni cos ®, (tan9 - tana)R cos 9 T L — — — — — — — — — —  .3 N :The factor R may be calculated from the theo­retical cluster distribution and is equal to7.5. Nj is the effective number of primary ionization electrons.The formulation above has three components: a constant term, a diffusion term and a cross­ing angle term. The constant term which is the best resolution was determined empirical­ly to be 180 p. It takes into account elec­tronic noise, fitting uncertainties, diffusion near the anode wire, and other poorly deter­mined factors. The second term, which takes into account the transverse diffusion during the drift in the chamber, is reduced by mag­netic field and is dependent on the track ion­ization density. The diffusion constant for each magnetic field was determined from the variation in width of the cathode charge distribution as a function of drift distance.The third term is dependent on the width ofthe entrance slot to the anode wire box, theI? x if forces near the anode wire and the dis­crete nature of the ionization deposited along the track. The constants governing this behaviour were determined from the vari­ation of the width of the cathode charge dis­tribution and from the theoretical variation in ionization density.The spatial resolution has a minimum near an angle a, where a is dependent on the magnetic field. A rapid deterioration in resolution occurs at larger and smaller angles. Since the momentum resolution of the chamber depends on the spatial resolution, and since negative particles tend to cross the wires at angles near a whereas positive particles cross at angles near -a, the TPC at TRIUMF has a better momentum resolution for negative par­ticles, such as electrons, than for positive particles, such as positrons. Based on these results the expected momentum resolution (FWHM) of the TRIUMF TPC for 100 MeV/c elec­trons is about 4% and for positrons it is 6%.Using the spatial resolution determined, the expected momentum resolution for tt+ e+ decay was obtained from a Monte Carlo simulation.The observed resolution (FWHM) of 5.5 MeV/c for the positrons with a momentum of 70 MeV/c agrees well with the calculated results.Experiment 121 Test o f charge symmetry in n -p  elastic scattering at 500 MeVDuring the past year instrumentation develop­ment has essentially been completed except for the frozen spin target whose completion is projected for May 1983. A program of instrumentation tests and preliminary mea­surements has begun and is rapidly increasing in pace in order to start data-taking in the summer of 1983.During the June-July shutdown the low intensity proton beam line (4C) was removed from the proton hall to make room for the neutron beam facility. The instrumentation for Expt. 121 installed in beam line 4A com­prises the following: a proton beam polarim- eter and proton beam energy monitor installed in a new lid of the SFU scattering chamber; two split-plate secondary electron emission monitors (SEM's) (each giving x and y co­ordinates) mounted in their own monitor boxes; the spin precession solenoid Janis; and a new proton beam profile monitor with 1 mm wire spacing just upstream of the refur­bished liquid deuterium (LD2) target.The proton beam polarimeter observes in coin­cidence the scattered (17° lab) and recoil protons from a thin kapton foil in left-right (L-R) symmetric detection systems. The geometry is chosen such that the polarimeter is insensitive to small lateral beam drifts at the target. The forward angle (17° lab) detection systems are followed by range counter telescopes each consisting of six scintillators interspaced by appropriate amounts of copper absorber. The proton beam energy monitor has shown to be sensitive to long-term beam drifts as small as 50 keV.Each split-plate SEM, with its feedback sys­tem to steering elements upstream, can lock the position of the centroid of the beam to within 0.25 mm. Since the SEM's are separ­ated by the superconducting solenoid Janis, coupling of the x and y co-ordinate correction matrices occurs. Further work on determining the 4x4 correction matrix for the dual SEM system is under way. The refur­bished LD 2 target has been able to accommo­date beam currents of 0.75 pA without noticeable deterioration in its operation.It is tentatively deduced that beam intensi­ties may be increased well beyond the 1 pA level. For beam current monitoring purposes a third SEM has been installed close to the beam dump. All elements on beam line 4A have been carefully surveyed and corrections weremade accordingly.During the October-November shutdown the steel collimator inserts for the 9° neutron port were remachined so that the neutron beam axis now properly intersects the proton beam axis at the centre of the LD2 target. The clearing and neutron spin precession dipole magnet Clyde, providing a vertical magnetic field up to 20 kG, as well as the second neutron spin precession dipole magnet Bonnie, providing a horizontal magnetic field up to 17.5 kG, were installed and aligned on the 9° neutron beam line. Additional collimation in the first spin precession dipole magnet will define a neutron beam profile of 2 in. k 2 in. at its exit. A neutron beam profile monitor and polarimeter have been installed downstream of the location of the polarized hydrogen target. The neutron beam profile monitor consists of a charged particle veto scintil­lator, a scintillator converter and two 8 in. x 8 in. delay line multiwire proportional chambers. Measurements of the neutron beam profile pointed to deficiencies in the collimator which have been corrected. The neutron beam polarimeter measures L-R and up- down (U-D) asymmetries by observing charged particles scattered from a polyethylene tar­get around 30° lab. Studies of the instru­mental asymmetries of the polarimeter have been made. The scintillator trigger may require to be viewed from two sides by photo­multipliers to correct a small U-D asymmetry.Subsequent to the commissioning and testing of the instrumentation on beam line 4A and the 9° neutron beam line, the major detection apparatuses were installed in a L-R symmetric configuration around the scattering centre of the polarized hydrogen target. All instru­mentation was carefully surveyed and aligned. Two booms holding the recoil proton detection systems pivot around the scattering centre. Each proton detection system (set at 52° lab) consists of a time-of-flight start counter; four 60 cm x 60 cm delay line multiwire pro­portional chambers (each providing x and y co-ordinates) and a range counter (AE scin­tillator, brass wedge-shaped absorber at 3.25 m, E scintillator and veto scintillator). Each neutron detection system (set at 32° lab) consists of a proton trigger counter (required for gain stabilization), a plane of veto counters, two banks of seven scintil­lator bars with the front face of the first bank at 5.00 m, each bar 15 cm thick, 15 cm high and 105 cm wide giving an overall effi­ciency of approximately 30% for neutrons, and a column of seven button counters (required9Proton rangeFig. 5. Experimental layout of the test of charge symmetry in n-p elastic scattering.for gain stabilization by triggering on pass­ing protons). The electronics has been set up in four racks just outside the neutron beam facility. In a test measurement n-p co­incidences were observed and rates determined using a water target.Layout of the apparatus is shown in Fig. 5.Further details about the test of charge sym­metry in n-p elastic scattering at 500 MeV can be found in a contribution to the 5th Int. Symp. on High Energy Spin Physics [Birchall et al., TRIUMF preprint TRI-PP-82-19].Experiment 130 Total cross-section differences in pp  elastic scatteringInterest in the possible existence of di- baryon resonances was stimulated in the late1970's when groups working at the Argonne laboratory found structure in spin-dependent total cross-section differences Ac^ and Ao-j in the 1-2 GeV/c range. For longitudinally polarized beam and targetA op = = An/p to Fjand for transverse polarizationsAcsj = o(+ + ) - a( + + ) = -An/p to F 2where F 2 and F 3 are spin-dependent forward scattering amplitudes and p is the laboratory momentum. During the same period extensive pp elastic scattering measurements allowed partial wave analyses with unique solutions up to 800 MeV [Dubois et^  a^., Nucl. Phys.A377, 554 (1982)]. Elastic data alone determine the phase shifts <5 accurately; however, the inelasticities n are rather poorly determined except for the dominant in­elastic channels ^ 2  and 3F 3 which also make large contributions to the elastic cross section. The imaginary parts of F 2 3 depend on sums of partial wave amplitudes through terms of the form 1 - n cos 6. Hence as the 6 are small (cos 6 close to unity), the total cross section differences give delicate information on the spin dependence of the inelasticity parameter n.A controversy developed whether the observed structure was due to resonances or threshold effects associated with the various possible inelastic channels. It was therefore felt desirable to measure Ac<l and Aop within the energy range available at TRIUMF (0.65 to 1.12 GeV/c) with careful attention to sys­tematic errors. These measurements are now complete and the final data submitted for publication.A new low intensity beam line, BL4C, shown schematically in Fig. 6, was constructed for this series of measurements in the location of the previous neutron beam line. The polarization of the incident beam at an intensity of 10® to 10^/s was monitored with the previously calibrated polarimeter P. Because of possible radiation damage the incident intensity acceptable for the polarized target is near 105/s. A reduction to 105 to 106/s was achieved by defocusing the beam onto the entrance of a 1 mm diam­eter 20 cm long collimator. For the longi­tudinal configuration the incident proton spin was precessed from the vertical direction by the combined use of the superconducting-Proton beam■Proton polarimeter & energy monitorH - dipole magnetLead collimatort.o.f. start x-y wirespin targetdetectoile monitorprecession solenoid plate s.e.m.'s deuterium targetV - dipole magnetcollimator10Fig. 6. The beam line and experimental lay­out in the Aoj. and Ao^ configurations:P, monitor of beam polarization; Q1,Q1, quad- rupole magnets; S, solenoid; C, collimator;M, bending magnet; PC, wire chamber monitor;S l 2 3* t>eam-(iefining counters; PT, polarized target; W, wire chamber monitors with trigger scintillators; T j_ 6, transmission counters; E 1}2, efficiency counters.solenoid and bending magnet. Two sets of split counter Sj, S2 and a veto counter S 3 and a wire chamber PC were used to locate and monitor the beam position. The polarized target was obtained from Liverpool University. In addition to the NMR system for monitoring target polarization, the tar­get polarization was monitored by observing pp elastic scattering with a double-armed telescope in the transverse orientation and the single-armed telescope in the longitudi­nal case. (In this case the polarization was aligned at 12° to the incident beam.)Total cross-section measurements were made by the conventional transmission method using six circular scintillation counters T^ sub­tending solid angle £2^ to record the fraction of the beam transmitted by the target in each polarization orientation. Total cross- section differences were then obtained by extrapolation of the differences in the transmitted fraction to zero solid angle.Experimental results are given in Table II and compared with results of other groups in Figs. 7 and 8. The results are essen­tially 3-4 mb more negative than previous Argonne, newer LAMPF and preliminary SIN data at nearby energies. Also Ac*p is up to 1.5 mb larger than the results from LAMPF and Saclay. The data at 202 and 325 MeV, below significant pion production, are, however, in good agreement with phase-shift predictions. Exhaustive discussion with the Argonne, LAMPF and SIN groups has not exposed reasons accounting quantitatively for the Ac^ dis­crepancies and hence must be resolved by new data soon forthcoming from Saclay.These A a n d  Aop data do not resolve the controversy regarding the existence of di- baryon resonances. Both cross-section differences peak near 550 MeV. The peak may be due to inelasticity in the 1D 2 channel. Detailed phase information over the whole energy range is required to establish the existence of a resonance.E la b  ( M e V )Fig. 7. Results for A c o m p a r e d  with those of other groups. Our points are denoted by full circles, LAMPF results by triangles and preliminary SIN results by open circles. Phase-shift fits of Dubois et al. are shown by the full line. The dashed line indicates the upper limits allowed by phase-shift anal­ysis if elasticities for J > 4 are taken from OPE and remaining inelasticity is all in *D2»E la b  ( M e V )Fig. 8. Results for Aaj compared with those of other groups. Our points are denoted by full circles, Saclay results by open circles and an Argonne result by a triangles. Dashed and full lines are as in Fig. 7.11Table II. Values for Ao^ and AoT . There is an additional normalization error of ±6.6% in Aol common to all energies and an independent ±6.9% in Aoj common to all energies.Parameter Energy Value(MeV) (mb)Phase shift prediction (mb)Aoj>A°l202.8 0.29±0.38325.1 0.16±0.37374.8 2.68±0.33419.4 4.21±0.37455.7 6.76 ±0.50497.5 10.84±0.73516.6 11.17 ±0.64202.7 -30.21 ±0.66325.4 -25.52±1.21419.5 -21.75±0.96455.8 -16.86±0.97497.1 -14.68±0.41516.5 -12.86±0.450.26±0.30 0.51±0.59-30.88±0.32 -25.78±0.63Experiments 132, 192 Pion productionDuring the past year the (p,ir) group has com­pleted data-taking on both of its proposals which used beam line 4B: Expt. 132, the measurement of the differential cross section (da/dfl) for the reaction pp dir+ , and Expt. 192, the measurement of the analysing power (A^q) for the same reaction. Data now exist on tape for d a /d Q at energies 500, 475, 450, 425, 375 and 350 MeV, and for Ajjq atenergies 500, 450 and 375 MeV. During thecourse of these experiments it was found to be necessary to calibrate absolutely our pp elastic beam monitors which resulted in measuring dcr/dfi for pp -* pp at 90° c.m. and for energies 300, 350, 400, 450 and 500 MeV.The aimed-for accuracy on these two proposals is 1% absolute on da/dfi and ±0.01 on A^q * The da/dfi data have not yet been analysed so that the 1% goal looks feasible but one cannot say for certain that it will be met. However, as analysis now stands, it seems certain the accuracy goal for Afjo will be met. In Fig. 9are shown the final A^q results at 450 MeV.The errors are all smaller than the size of the data points. There are no errors larger than ±0.01. From examination of the smooth­ness of the data points the error estimation seems realistic.trIdSoQ-IM>-<Z<0 . 0.2- 0 . 3- 0 . 4- 0 . 5- 0. 6■■■ ■_1_ _l_ _1_4 0  8 0  120 160C.M. PION ANGLE (DEGREES)Fig. 9. The analysing power for the reaction $jp dir+ at 450 MeV. Errors are smaller than the data points.Preliminary results for the pp elastic cross- section measurement are currently available and are shown in Fig. 10. The errors shown are absolute and are around ±0.6%. As can be seen the data are certainly the definitive measurement at this angle and energy region. The data also match nicely with similar measurements done at SIN (NESIKA) between the energies of 500 to 600 MeV. The curve shown in the figure is a recent PWA fit by Arndt. The results shown could move around by as much as an error bar as certain systematics and corrections are accounted for.Fig. 10. The differential cross section for the reaction pp pp at 90° c.m.12Experiment 134 Measurement o f the r\ parameter in muon decayRecent interest in precise values of the parameters for muon decay arises from the possibility of looking for the effects of small contributions of the weak interaction which may add to the standard interaction given by the Weinberg-Salam model. In par­ticular the least well determined parameter n determined directly by Derenzo (1969) has a value n = 0.12 ± 0.21. The sensitivity to this parameter is maximum at the low end of the (unpolarized) muon decay spectrum. However, its effect is scaled down by a factor ~ m e/my so that for example for elec­trons of energy Ee/Fmax =0.1 the fractional change in the spectrum is less than 0.2 n.The direct measurement of n therefore requires accuracy in spectral shape to better than (the order of) a per cent to show that n less than 0.1.A group from UC Berkeley-LBL has undertaken this difficult measurement with a convention­al axial focusing beta spectrometer (Fig. 11) which is scaled up to ~50 MeV maximum energy. It has ~2.5% resolution with the severe requirement that electrons of energy greater than that at which the spectrometer is set will not filter down and distort the shape at lower energies. This is important because at low energies the intensity is already greatly reduced relative to its peak value, which occurs near the upper energy limit.This requirement dictates a rejection of less than 10“ 5 for positrons at the maximum ener­gy, 50 MeV, ending up at one-tenth or 5 MeV.An elaborate array of veto counters to elimi­nate such inelastic processes has been added within the vacuum chamber of the spectrom­eter which are designed to reduce these spurious events.The progress to date is as follows. The spectrometer has operated and performed ac­cording to our expectations using test beams of (contamination) electrons obtained in the M13 beam line. This electron beam was directed into the acceptance aperture of the spectrometer. Adequate resolution and rejec­tion requirements were measured and a preliminary muon decay spectrum obtained in March. The result of this run was limited to a statistical accuracy of order of the exist­ing value and a number of small but signifi­cant corrections, due to for example, bremsstrahlung in the muon stopping target, a thin scintillator, and Bhabha scattering,| v ! 'A 3  A 2  A lO hC2□ O H  A .7:N o IFig. 11. Comus spectrometer, top view (not to scale).ionization, energy loss, etc. are being calculated in a computer simulation by Monte Carlo method. We are confident that the accuracy of these corrections will be suffi­cient to reduce the systematic errors well below the goal for our accuracy for n less than ±0.05 and a run is being planned to reduce the statistical error to this level later in 1983.Experiment 137 Lifetime o f the positive muonIt is of interest for several reasons to know the mean life Ty of the positive muon to high accuracy. The dimensional coupling con­stant Gy of the electroweak interaction is essentially determined by Ty. A comparison of of Ty with the mean lifetime of negative muons in hydrogen gives the rate of capture of the y- by protons. We have therefore made a precise measurement to verify and to improve somewhat the accuracy of determiningVThe experiment was done in two runs, one in July 1981 with beam line M13, and the other in August 1981 with beam line Mil. Beams consisting primarily of were stopped in a 48 cm long, 48 cm diameter cylindrical water Cerenkov counter. The arrival of the tt+ was signalled by a coincidence in two plastic scintillators placed in front of the Cerenkov counter, and the time of e+ emission from ir+ ■+■ y+ -*■ e+ was signalled by the Cerenkov light. The intervals between beam particle arrival and Cerenkov signals were determined by a specially constructed clock in which the detector signals gated pulses from a 108 Hz crystal-controlled oscillator, and the number of oscillator pulses was counted. Events were recorded during a 20 us period after a13tt+ stop and were stored in separate histo­grams according to both the multiplicities and energies of the Cerenkov signals. The single medium energy e+ histogram contains 3 x 10 9 events.The possibility of systematic errors being introduced by precession or depolarization of beam y+ contaminant was examined in detail. Cancelling coils kept the magnetic field in the detector below 50 mG to reduce precession to a low level, and an estimate of depolari­zation effects showed that these also were negligible. In addition a sample of data from time-of-flight selected beam muons showed directly that such beam muons did not affect the result.The single medium energy (20-50 MeV) events were fitted to the expressionae~t / T V + bfor t large compared to the pion lifetime.It was verified that the data required no other terms in the fitting function. Exami­nation of runs with differing beam intensi­ties showed that there was no detectable rate dependence.Our result is = (2.19695 ± 0.00006) ys. Experiment 159pp andpd  interactions a t thresholdThe CERN-Mainz-Munich-Orsay-TRIUMF-Zurich collaboration is preparing to study pp reac­tions at rest by stopping low momentum anti­protons provided by the low-energy antiproton facility LEAR at CERN. The objectives of the collaboration are to obtain an understanding of protonium spectroscopy, "pn annihilation dynamics, spectroscopy of normal (qq) and exotic mesons (including baryonium) produced in pn annihilations ami an understanding of the relations between NN and NN interactions. Most of the existing data on pn annihilations have been derived from analysis bubble chamber data for which analysis of events with multiple neutral particles is not pos­sible. Due to Stark mixing annihilations in liquid are essentially all from the s state. In this experiment the antiprotons will be stopped in an H 2 gas target at atmospheric pressure positioned in the centre of a large acceptance magnetic detection system. Gamma- rays will be detected in position-sensitive y-detectors mounted on the spectrometer end caps and by y-converter foil inserted intothe cylindrical detector system. The unique and novel feature of this experiment is to trigger the readout system on X-rays arising from transitions between low-lying Coulomb energy levels of the protonium (pp) atom in coincidence with both charged and neutral annihilation products.The large acceptance magnetic detector which has been used previously on e+e- colliders at Orsay and now modified for this experiment is shown in side elevation in Fig. 12. This detection system has cylindrical symmetry.The X-rays will be detected in a thin windowed (6 p mylar) multiwire drift chamber which surrounds the gas target. Charged pp annihilation products will be tracked through the magnetic field using the 9 concentric multiwire proportional chambers.The TRIUMF contribution to the collaboration is the cylindrical multiwire proportional chambers Cl and C2. These chambers were built at the Carleton Science Workshops in accordance with their extremely successful1 H2 target gas 10 Position-Sensitive Gamma Detector (PSGD)2 Moderator 11 Extension of magnet coil3 50y plastic scintillator (T2) 12 Extension of magnet yoke4 Veto scintillator (T3) 13 Magnet yoke5 Veto scintillator (Ti*) 14 Magnet coil6 X-ray Drift Chamber (XDC) 15 Endcap7 Internal Drift Chamber (IDC) 16 Cradle8 Cylindrical MWPC's Cj, C2 17 Cylindrical MWPC's Qj, Q2, Q39 Cylindrical MWPC's Pj, P2 18 Gamma conversion foil (optional)Fig. 12. Experimental set-up (side view).14Chamber Current (Microamp)Anode Voltage (KV)Anode voltage (KV)Fig. 13. (a) Chamber efficiencies and(b) chamber leakage current, at an incident flux of 8 x 105 particles per and construction procedure. The high voltage distribution and signal pick-off sys­tem for the anode wires and the cathode pre­amplifier system were designed and prototypes built in house. Both chambers and the support electronics were checked using a beta source. Finally rate-dependent tests of the complete system were made in a minimum ionizing elec­tron beam with pion and muon contamination us­ing the Mil channel. Efficiencies for Cl and C2 anodes and C2 cathodes as a function of the anode wire voltage are shown in Fig. 13 at an incident flux of 8 x 105 particles per second.The support electronics for the two chambers have been built by a local firm. The complete system has been shipped to CERN and is now installed in the magnet in the south hall at CERN.Computer programs have been developed for writing and reading data summary tapes, Monte Carlo simulation of data and graphical recon­struction of events. These techniques are being developed in such a way as to handle easily in excess of 108 events. These pro­grams have been integrated with existing software from CERN and the complete package is being tested at TRIUMF. A large data run is scheduled for the autumn of 1983.Experiment 168 2S muonium production from thin foilsDuring the spring a new apparatus was con­structed for this experiment (Fig. 14). This apparatus was tested with an a source and the Lamb shift in n=4 He+ measured to be 1.81 ± 0.08 GHz (see Fig. 15). This is in good agreement with the theoretical value of 1.77 GHz. Tests on M13 in August showed that a separated p+ beam was not required and the experiment benefited from the superior beam spot obtained. The multichannel plates (MCP) appeared to be working at a lower efficiency than expected; however, a clear signal was obtained for 2S hydrogen.During the fall improvements were made to the apparatus to allow for baking and testing of the MCP1s. During 3.5 days of beam time in December a significant improvement in the efficiency of the MCP!s was obtained and a signal for both 2S hydrogen and 2S muonium obtained.A data-taking run is planned for the spring 1983 to make a measurement of the Lamb shift in the n=2 state of muonium. It is planned to design a new apparatus for a more accurate measurement.e + DETECTORFig. 14. The apparatus, showing an event in the quench region.15FREQUENCY GHzFig. 15. Measurement of the Lamb shiftin n = 4He+ .Experiment 174 pp pnn+A unique and well-defined set of 1=1 (proton- proton) phase shifts [Dubois et^  al^ ., Nucl. Phys. A377, 554 (1982)] up to 650 MeV has been deduced from the data obtained at the three intermediate energy laboratories. Sim­ilarly, 1=0 phase shifts, which require np scattering data, are well known up to 515 MeV Further improvement in the understanding of the nucleon-nucleon interaction requires a similar amount of experimental data and anal­ysis of the inelastic reactions NN ■* NNit. Aseries of experiments to measure the spin dependence of inelastic reactions are in progress at a number of laboratories. The BASQUE group has used the variable energy polarized proton beam, the polarized proton target and the detection system used previ­ously in the elastic scattering experimentsto measure the spin correlation parameters ALL> ALS> ASS> ANN and the analysing power Aqj^  for the inelastic reaction pp pmr+ at three energies and a restricted geometryimposed by the apparatus. This is the firstdata obtained for a reaction with a three- body final state using a polarized target.The experimental apparatus as it was config­ured in beam line 4C is shown schematically in Fig. 16. For the A ^  configuration no solenoids were used and the polarized target was mounted with the proton spin normal to the reaction plane. In this configuration additional measurements were made with a non- hydrogenous teflon target to determine the quasi-free proton contamination in the data from bound protons in carbon nuclei of the sample. The P parameter for pp elastic scat­tering was measured to confirm the calibra­tion of the NMR system used to monitor the target polarization. For the App and AgpFig. 16. Experimental configuration.configurations the target spin was longitudi­nal and the upstream solenoid used for the first configuration and the downstream for the second. For Agg the polarized target spin was rotated through 90° (s = iJxf).Angular position and time of flight of the neutron was measured with a one metre square neutron detector 6 m from the target. This detector was moved through four angular posi­tions in the horizontal plane at each energy and spin configuration. Angular co-ordinates of the two charged reaction products were de­termined using six one metre square multiwire proportional chambers immediately downstream of the target. The trigger scintillator downstream of the chamber array was divided into a 3x3 logic matrix. For the Agp, Appand Agg configurations pions were also ob­served at 90°±12.5° horizontally and ±12.5° vertically. The trigger consisted of two charged particles in the logic matrix in co­incidence with a beam particle and a neutron. A total of 3.2 million events was recorded. The distribution of the events between ener­gies and angles is listed in Table III.The method of analysis is to solve the three conservation of momentum equations and the conservation of energy equation iteratively correcting for the effect of the magnetic field in each configuration. The solution is done twice, once with each possible mass assignment for the two charged particles. For each iteration a x2 is calculated and the solution with the minimum x2 chosen. This X2 distribution is shown in Fig. 17 where the shaded histogram is for the carbon data. For a cut at X2 = 4 the data sample has a less than 10% carbon contamination.16(/>h-lj  4 0 0  -QLdh-0 ZD01 h cn z o<Jolz3 0 02 0 0  -100 -X c D ISTRIBUTIO N OF RECONSTRUCTED EVENTSP O L A R IZ E D  PROTON TARGET (A L L  SP IN S )TE FL O N  TARGET(N O R M A L IZED  AT HIGH X c )f“ T10 12 14X 2 ( 2C F IT)Fig. 17. Comparison of the x of recon­structed events with a polarized and a teflon target in the Ajjjj configuration, at 470 MeV and the neutron detector at 8°.Aj^ [ and Agg for neutron angles equal to 8°, proton angles of 10±5° and pion angle of 20±5° as a function of the recoil proton momentum are shown in Fig. 18. The solid curve is the result of a coupled channel cal­culated by Kloet and Silbar [J . Phys. G. 8^  475 (1982)] in which the authors considered only the P 31 and P 33 intermediate states for the ir+p system. For this specific geometry the agreement between experiment and theory is excellent. The remainder of the data is being analysed.p ( M e V / c )Pl a bFig. 18. Spin-spin correlation parameters for pp -*■ pnfr+ as a function of scattered proton momentum at 510 MeV with the neutron detector at 8°. Near-coplanar events with 9p = 10°±5°, D = 20°±5° (except for Agg with =±2°). Vertical acceptance of p,iT is ±7.5°. Points are present data. Bin widths are 50 MeV/c (100 MeV/c for Agg). Solid lines are calculations from Silbar with 9p = 10°,8^ = 20° at 500 MeV.vn10Table III. Number of triggers recorded at each angle of neutron detector (Total: 3.2 million events).Configuration Energy 8° 17° 26° 35°All 516 106,000 107,000 85,000 85,000470 71,000 106,000 81,000 130,000425 100,000 80,000 82,000 -a sl 516 172,000 89,000 86,000 90,000470 97,000 82,000 81,000 98,000425 46,000 45,000 - -a nn 514 50,000 58,000 40,000 64,000470 57,000 80,000 60,000 47,000425 45,000 39,000 - -Ann Carbon 470 24,000 25,000 25,000 25,000425 25,000 14,000 13,000 -ASS 513 80,000 111,000 139,000 83,000470 40,000 40,000 66,00017Experiment 185 Precise measurement o f the polarization parameter £During 1982 Expt. 185 made the transition from an inventory of magnets and detectors to a fully operational experiment which collected a substantial sample of data. Re­building and mapping of the Sagane magnet was completed by TRIUMF and installed in the M13 experimental area in January. After the magnet was aligned and its vacuum tank was fabricated at TRIUMF and installed, the medium and large drift chambers were attached and tested parasitically in that channel. During March the solenoid magnet was powered, mapped and installed. A two-shift run at 10-l+ of the normal M13 beam intensity was sufficient to establish the trigger and observe parity noninvariance.The experiment's first prime use of the M13 channel occurred during four weeks in April and May. Usable data were collected begin­ning in the second week. With substantial assistance from the TRIUMF cryogenics group, the liquid He target was commissioned and used for data collection during the third and fourth weeks. At this early stage in the experiment the majority of running time was used for necessary calibrations and studies of possible sources of systematic error.By the time of the Experiments Evaluation Committee meeting in July enough analysis software had been developed to confirm the success of the shakedown run. Typically, drift chamber planes were 98% efficient with 250 u resolution. Positrons at the end of the muon decay spectrum were fit with momentum resolution under 100 keV. A Monte Carlo-independent method of determining £ by direct comparison of data with the decaying muons unpolariged and fully polarized was identified and applied. The statistical error on £ from this initial sample was 0.3% for each of five stopping muon targets.During the summer and early fall 100% of these data were processed using off-lineXFig. 19. Distribution in reduced positron energy X near the spectrum end point X=l, for unpolarized muon decay. The sharp edge is evidence of the excellent resolution. The rounded shape near X=0.99, created by Bhabha scattering and radiation in the target and other material, is well fitted by the expected curve.analysis codes which are close to what will ultimately be necessary. Approximately 99% of the triggers produced found tracks in all spectrometer segments. The analysis package was installed on a VAX 11/750 computer brought to the M13 counting room for that purpose.A main data-collection run used the equiva­lent of three weeks of M13 beam in November and December. A number of minor improvements were made to the spectrometer, and a sigifi- cant fraction of the data was analysed for physics results within a few days of its col­lection. Performance of the detectors was excellent, allowing three times the spring 1982 statistics to be obtained. The analysis was refined to the point that statistically significant differences in £ determined from different targets became evident. These data are being studied closely. Barring unfore­seen difficulty, preliminary results are expected in the spring of 1983.18NUCLEAR PHYSICS AND CHEMISTRYExperiment 111 Absorption at rest o f negative pions in 12CThis experiment was undertaken with the pur­pose of obtaining complete data regarding the light particles (n, p, d and t), of energy greater than about 20 MeV, emitted by direct processes after negative pion absorption at rest in 12C.The group measured the energies as well as the momentum directions of either single particles (n and p) or of two particles in coincidence like (n,n), (n,p), (n,d) and (n,t), emitted after pion absorption. From the measured data other information has been obtained, such as excitation energy spectra of the residual nuclei, recoil momentum dis­tributions, angular correlations of the particle pairs, one-nucleon energy spectra in coincidence and branching ratios.The experiment was performed with negative pions, on the M13 channel, having a momentum of 113 MeV/c, i.e. a kinetic energy of 40 MeV.The neutrons emitted after pion absorption were detected by means of four neutron counters. Each neutron counter consisted of an NE110 scintillator slab having an area of 200 x 15 cm2 and a thickness of 5 cm. The counters, arranged in two pairs and placed one on top of the other in each pair, were used independently to measure the neutron time of flights over a flightpath of 5.20 m. The overall resolution was 650 ps and the energy threshold was set at about 15 MeV. The neutron momentum directions were determined with an uncertainty of 1-2°.The identification and the energy measurement of the charged particles were performed with a counter telescope consisting of eight NE 104 scintillator slabs having an area of (78x18) cm2. Particle identification was achieved by means of a combined beta-range- energy method. The particle energy was measured by a time-of-flight method with a time resolution of about 600 ps and energy thresholds of about 19, 28 and 33 MeV for p, d and t, respectively. The counter was placed at a distance of 4.5 m from the target, and between the target and the counter was placed a helium bag to reduce the charged particle energy loss due to air.Some of the results obtained in this experi­ment are the following:Single nucleon energy spectraThe single neutron spectrum is shown in Fig. 19 and is the sum of the spectra measured by the four independent neutron counters.The sum was arrived at after having sub­tracted from each of the four spectra the relative background - different for each of the counters - and after having verified the mutual consistency of the four spectra.The spectrum exhibits some significant struc­tures. The peak at 111 MeV [which is well above the kinematic end point (101 MeV) of the two-nucleon emission process] should be associated with the single-neutron emission; in fact it corresponds kinematically to neutrons of the reaction 12C( ir_,n) 145. The energy resolution in this energy region (5.5 MeV) is not sufficient to separate the ground state from the excited states of ^B. The area under this peak is about 1.7 x 10~ 2 neutrons per stopped pion, that is, ten times greater than the value of Bassalleck nt al. [Nucl. Phys. A319, 397 (1979)], which - as far as we know - is the only experimental value reported in the literature. The peak at about 89 MeV could be attributed to neutrons coming from the reaction ltHe(ir- ,n)% on an a-substructure in the 12C nucleus.By integrating the spectrum one obtains for the multiplicity of fast neutrons (above about 15 MeV) the value 1.25 neutrons per stopped pion which is in good agreement with the average value 1.4 reported in the literature.Fig. 19. Neutron single-energy spectrum.19PROTON ENERGY (M eV)Fig. 20. Proton single-energy spectrum.The single-proton spectrum shown in Fig. 20 corresponds to the inclusive reaction ir“+ 12C > p + anything. It was measured with the charged particle counter telescope. Such spectrum is very different from the single­neutron spectrum: in fact, it does not exhibit significant structure, and its high energy tail drops down at lower energies than in the neutron case.Excitation energy spectraIn Fig. 21 the excitation energy spectrum for the reaction 12C( ir“,nn) 10B, corresponding to the opening angle range 150°-180°, is shown. The peaks below 15 MeV can be associated with the removal of two nucleons from the p shell leaving a bound state of as residualnucleus, in agreement with the data of Bassalleck et al. [thesis, Inst. f. Kern- physik, Karlsruhe (1977)]. Cheshire et al. also observed the excitation of the (IP3/2) two-hole state but with less resolution. The presence of these peaks may be interpreted in the light of the calculations of Kopaleishvili regarding the probabilities of exciting levels in 10B. The peak at 20 MeV could be attributed to an s-p removal since the exci­tation energy is a little too high to corre­spond to a (lp 3/2)~2 configuration. This hypothesis can be checked by analysing the recoil momentum distribution. The large peak at about 38 MeV can be interpreted as due to the removal of two nucleons from the s shell. The (Is1/2)-2 two-hole excitation is expected to exceed the (IP3/2)-2 excitation by roughly twice the separation between the one-hole ex­citations involving the same shells. From the (p,2p) experimental data of Tyren et al. this separation amounts to 19.3 MeV, whichEXCITATION ENERGY (M « v )Fig. 21. Excitation energy spectrum for the (ir“ ,nn) reaction in 12C.agrees with the separation of 17 MeV deduced from our data. In any case, the general pattern of our (n,n) excitation spectrum resembles closely that of the 12C(p,pd)10B of Zhusupov et^  al.Angular distributions of the emitted pairsThe angular distributions of the (n,n),(n,p), (n,d) and (n,t) pairs emitted after the pion absorption were measured.The (n,n), (n,p) and (n,d) distributions are presented in Fig. 22. One may notice, first­ly, that the back-to-back emission is some­what more pronounced in the case of the (n,n)and (n,p) pairs than in the case of the (n,d)pairs. Secondly, that while for the (n,p)  the o ry  ( ref. 18)■ ("•") P-i'O□  (n .  p )  p a ir s  >  t h is  w o rk  y ^ ~ • (n .  d )  p a ir s  J 15Fig. 22. particles* 0  100 M O  180O PE N IN G  ANGLE (deg.)Angular distributions of pairs of emitted in the tt“+ 12C reaction.20and (n,d) pairs the absorption rate versus opening angle decreases monotonically as the opening angle decreases, for the (n,n) pairs the distribution shows a broad hump in the angular range around 100°. This pattern agrees with the predictions of Bhalerao and Waghmare that are based on the assumption of a two-nucleon absorption mechanism with final-state interaction between the two out­going nucleons, and takes into account all the possible excited states of the residual nucleus 10B.Data analysis are in progress and the results will appear soon in the literature.Experiments 113 and 153 Elastic scattering o f polarized protons from 3He at intermediate energiesMeasurements have been made of the differen­tial cross section and analysing power angular distributions for proton elastic scattering from 3He. Data were obtained from the angular range 20° to 150° c.m. at inci­dent proton energies of 200, 300, 415 and 515 MeV. A liquid 3He target system provided areal densities of 90 or 120 mg/cm2. The medium resolution spectrometer (MRS) was used to detect scattered protons at the forward angles and recoil 3He particles at the larger angles.- I  (GeV/ c  ) 2Fig. 23. Differential cross section angular distributions for 3He(j£,p)3He compared with Glauber model predictions.The differential cross sections obtained, together with data available from the litera­ture, are shown in Fig. 23. The curves are calculated using the Glauber multiple scattering formalism with a parametrized nucleon-nucleon scattering amplitude of the form:f p>J = 4"ii °p >j (i+ a = a p > j ) e P ’ -^ » J= p>n ;where k is the incident momentum, isthe total proton-nucleon cross section, is the ratio of the real to the imaginary part of the proton-nucleon scattering ampli­tude as 0°, bp^j is the proton-nucleon scat­tering slope parameter, and q is the momentum transfer. The agreement is satisfactory for the forward angles at the higher energies, but the shape of the minima and the backward angle data are not reproduced. A more detailed calculation is under way using the complete spin-isospin dependent form of the nucleon-nucleon scattering amplitudes as given by phase-shift analyses. Such a calcu­lation can then also be compared with the analysing power data which are shown in Fig. 24. Hopefully, these calculations will provide some indication of the appropriate­ness of the approximations used and of the basic input to the calculations: the nucleon- nucleon scattering amplitudes. Also the kinematic corrections to the on-shell scattering amplitudes can be examined.156 MeV 3H e ( p , p ) 3He-2 0 0  MeV-■■3 0 0  MeV■ "■ ■ ■ "■ ■■ ■+m 415 MeV-m515 MeV\  - I%i i i i i i0  3 0  6 0  9 0  120 150 1809cm ( deg )Fig. 24. Analysing power angular distribu­tions for 3He(^,p)3He at 200, 300, 415 and 515 MeV.21An optical model parametrization of the dif­ferential cross section and analysing power data of the present experiment has been per­formed to provide the input to distorted wave impulse approximation calculations.Experiment 114 Study o f3He(p,2p)d and 3He(p,pd)p quasi-free scatteringThe principal interest in studying these reactions is the determination of the proton- deuteron relative motion momentum distribu­tion in 3He in the framework of the PWIA and DWIA. In this context the 3He(p,2p)d and 3He(p,pd)p reactions should result in the same relative motion momentum distribution of a p-d pair. Comparison of the results of the two reactions will provide an unambiguous test of the reaction mechanism and the cor­rections used in the deduction of the momen­tum distribution.The 3He(p,2p)d reaction was studied at an incident energy of 450 MeV at the angle pairs 70°-30° and 46°-46° and at 300 MeV at 70°-33° corresponding to recoil momenta larger than 350 MeV/c. These high momentum components of the wave function were previously unexplored. For the 3He(p,2p)d reaction the magnetic spectrometer (MRS) and a Nal(TJl) counter telescope consisting of a multiwire propor­tional chamber, a 0.08 cm thick plastic scintillator, a 10.2 cm diameter annular (veto) plastic scintillator and a 12.7 cm diameter by 15.2 cm thick NaI(T£) detector.In order to separate two-body breakup events from three-body breakup events the recoil deuterons were detected in coincidence with a second Nal(TL) counter telescope thus requiring a triple coincidence. For all these measurements the University of Manitoba L 3He cryostat with target cell of 120 mg/cm2 thickness was used.Some of the 3He(p,pd)p data were collected simultaneously with the (p,2p) data at the same angle pairs. The corresponding recoil momenta are between 80 and 290 MeV/c. Other measurements of the 3He(p,pd)p reaction were made at 450 MeV incident energy at the angle pairs 68°-25° and 68°-50° covering a range of recoil proton momenta from 0 to 400 MeV/c.In the case of the 3He(p,pd)p reaction the deuteron was detected with the magnetic spec­trometer MRS and the proton with NaI(T£) counter telescopes. Analyses of the latter data are still in progress.A  °3H e {p ,2 p )d  ( 4 5 0  MeV) TRIUMFf \3H e (p ,2 p )d  ( 3 0 0 MeV) TRIUMFa  A 3H e(p , p d )p  (4 5 0 M e V )  TRIUMFT ^ r  A 3H e(p , p d )p (3 0 0 M e V )  TRIUMFT jk  ■ 3H e (p ,p d ) p (5 9 0 M e V ) S R E L♦ A  + ♦ 3H e (e ,e 'p )d  (5 3 0 M e V ) SACLAY3He(e , e 'p ld  ( l2 0 0 M e V ) KHARKOV 1 S ( P ,  E ) IRVING -G U NN+ V ® 2 S ( P , E  ) LEHM AN+\ \ 3 S ( P ,  E)  DIEPERINK+ Y \ + Y4 S ( P , E )  CIOFI d e g li A T T I+ \ ( V \ \  •  \V A 5 fc  <+W " 5_W  51 12i i i \  \ \ \100 2 0 0  3 0 0  4 0 0  5 0 0  6 0 0P ( MeV/c )Fig. 25. Nucleon momentum distribution in % e as function of the recoil momentum. The data are as indicated.A comparison of our results with previously existing data is presented in Fig. 25.Curve 1 shows a PWIA prediction based upon the Irving-Gunn wave function for 3He, while curve 2 shows the spectral function S(f,E) as obtained by Dieperink e_t al. in the context of the PWIA using the three-nucleon wave function of Brandenburg, Kim and Tubis ob­tained through a Faddeev approach. The other other curves show the spectral function ob­tained by Gibson and Lehman from three- nucleon wave functions using separable poten­tials and by Ciofi degli Atti al. using variational techniques. There is an apparent excess of high momentum components for large recoil momenta as has been observed in previous (p,2p) measurements on light nuclei.22Experiment 117 FragmentsThis experiment is designed to measure single particle inclusive energy spectra of light fragments (A < 8) over a large range of frag­ment energies (to the kinematic limits for Z >2). Data are being collected at two incident proton energies (190 and 300 MeV) for two targets, Be and Ag. Coupled with the large angular range studied for these reac­tion products (20° to 160°), this information should provide a nearly complete characteri­zation of light fragment spectra from these representative light and medium mass targets.Half of the desired data was collected during 1982. Coupled with previous data, this completes 75% of the required measurements. Only radiation damage to the high-purity Ge detector being used prevented completion of the experiment. The radiation damage has now been eliminated by reannealing the detector, and it is hoped to complete the experiment with one additional set of runs in 1983. A second HPGe detector has also been acquired and will allow the energy ranges of the hydrogen isotope fragments to be extended for these final measurements.Experiments 124 and 165 Giant resonancesDuring the past year the group has combined the Ay(0) results obtained on 208Pb with its earlier cross section measurements in order to obtain a thorough picture of the giant resonance excitations for this impor­tant nucleus. A number of significant con­clusions can now be drawn.In agreement with earlier work a strong iso­scalar quadrupole peak was found with its ipain strength concentrated at an excitation energy of 10.6±0.5 MeV and a weaker L=2 resonance at 8.9 MeV. The L=2 nature of this peak is nicely corroborated by our Ay(0) measurements, provided that a Full-Thomas spin orbit interaction is included in the DWBA calculation. Our observed EWSR sum rule depletion of 23±3% is also in accord with results from a recent experiment with 200 MeV protons at Orsay. Our EWSR value was obtained in the standard collective model DWBA procedure where the form factor is the deviative of the proton-nucleus optical potential. The optical potentials were taken from the recent analysis by the IUCF group.Inasmuch as lower energy results are consis­tent with an L=2 EWSR of 80% or higher, it is concluded that our DWBA analysis underesti­mates a transition strength by roughly a factor of 3-4.There is a striking disagreement between our interpretation of the peak centred near 20.9±1.0 MeV and conclusions drawn from several earlier experiments. We conclude that this peak is a T=0, L=3 resonance in substantial agreement with the 800 MeV inel­astic proton scattering work which has the L=3 peak at 19.1±1.0 MeV and the %e scatter­ing studies of Yamagata et al. where the L=3 resonance is found at Ex = 20.5 MeV. The present cross-section results are backed up by our A„(0) data which are in accord only with an L=3 assignment. On the other hand the isoscalar octupole resonance is claimed to be at 17.5 MeV from both 172 MeV alpha particle scattering studies and the recent 200 MeV Orsay proton investigation. Our ob­served L=3 EWSR is only 10±3%, but if this is multiplied by three, as in the L=2 case, then the value of 30±9% would be in general agree­ment with RPA calculations.Two close peaks, found near 14 MeV of excita­tion, can be reasonably identified as an IVGDR and an isoscalar monopole vibration. Beyond 7° the L=0 contribution starts to dom­inate; our A y ( 0) data confirm this multi­polarity assignment. Multiplying the observed L=0 EWSR of 30±15% by three implies that the monopole transition exhausts the theoretical sum rule.Some evidence is found for a weakly excited L=4 peak located just above the strong giant isoscalar quadrupole resonance, although the evidence is not totally conclusive. It is found that this peak contains about 2.5% of the total hexadecapole EWSR strength (10% if we multiply by the scaling factor of four), in keeping with the upper limit of 5% found by us in lower mass nuclei for the 2 hto, L=4 transition. The results are shown in Fig. 26.The background shape of the continuum is roughly what would be expected if single­scattering processes dominate with a broad quasi-elastic peak standing out at low exci­tation energies. A plot of the excitation energy of the centroid of this peak as a function of scattering angle verifies that this broad peak follows quasi-free scattering kinematics if an average binding energy of about 12 MeV is assumed.23at the low 2.6 keV energy of the t-d K a X-ray, and to data-taklng with three different absorber foils and three detectors. Two of the foils were coated with Bi, whose My absorption edge spans the Ka region of interest. The histograms and fits for one of the detectors are shown in Fig. 27.The problem of the high continuum background is apparent, but the Ka X-ray in the case of zero Bi absorber is resolved from the Kg and Ky structure. Systematic uncertainties in fluorescence backgrounds, especially from Bi, are a limiting factor; Bi electronic M X-rays cannot be resolved from the K a peak.It is planned to build and test a gas scin­tillation proportional counter (GSPC) of resolution comparable to the Si(Li) detectors, to facilitate a reduction of the continuum background and a determination of fluorescence backgrounds.Experiments 131 and 190 Radiative capture o f polarized nucleonsFig. 26. Angular distributions for L=2 and L=2+4 resonances. Data on the L=2 peak from Orsay are included for comparison. The solid curve is a DWBA L=2 calculation; the dashed curve includes some L=4 strength.This past year has seen the completion of data-taking for Expt. 131 with the measure­ment of the asymmetry and cross section for the reaction 3H(^,Y)^He. Data were taken at seven angles for Ep = 300 MeV and a limitedAnalysis of data taken on 80Ni, 88Zr, 120snand 238U has been completed. Papers describ­ing this work are in preparation. The giant resonance aspects of the scattering of 200 MeV protons by these nuclei will form the Ph.D. thesis of J. Tinsley.Experiment 127 Strong interaction sh ift in pionic deuteriumThe objective of the experiment is a precise (<1 eV) measurement of the Ka X-ray energy of the ir“d system by the critical absorption technique. In 12 shifts on M13 in February it was established that the background in the Si(Li) detectors, in the range 2-20 keV, was due primarily to energetic photons scattering in the detector material. Furthermore, it was correlated with high energy gamma-rays from it-  interactions detected in a lead glass counter. This is a major restriction in the precision obtainable with large solid-state detectors.1600 — I— I— r12008 0 04 0 0- |-----1-----1— r~* 1.0 mg cm Bi_l I I L_E N E R G Y  ( K e V )A subsequent set of 24 shifts in July on M9 was devoted to improving the Si(Li) operationFig. 27. ir-d spectrum taken with the foils indicated on the figure.24excitation function was obtained for three angles from additional measurements at Ep = 225 and 375 MeV.Excitation functions for the reaction 2H(j5', y) 3He at centre-of-mass angles of 60° and 90° have been compared with other data for this and the inverse reaction in a paper to be published in Physics Letters. It is interesting to note that recent data on 3He photodisintegration taken at the MIT-Bates facility are in substantial accord with the TRIUMF radiative capture data indicating that there is as yet no clear evidence for time reversal violation in the A-energy region for these electromagnetic reactions.A second paper is in preparation in which our angular distributions for asymmetries and cross sections for this reaction are compared to a number of existing model calculations. Analysis of data obtained for the reaction 2H(f£, ir°) 3He during the experiment is now nearing completion.The apparatus for the n^ " -> dy experiment (190) was installed at year's end and a data- taking phase is anticipated, at energies below the pion production threshold, in the first half of 1983. Polarized neutrons will be used to bombard a liquid hydrogen target and, as in the previous work, recoil nuclei will be detected in coincidence with the photons.Experiment 142 Non-evaporative fragment emissionThe data of the 300 MeV (p,2p) measurements on 9Be have at least three significant features. First, there is a clear correla­tion between trigger protons at 90° (lab) and high energy forward protons. An integration of the data indicates that this correlation is substantial (5-50% depending on the trigger energy). Second, the angular distri­bution of the forward protons is quite sharp (A9 ~ 27° FWHM) and located above the QTBS angles (angle of minimum momentum transfer) for low energy triggers but approaching the QTBS angles for trigger protons of greater than 100 MeV. Third, there is little evidence for some of the previously reported phenomena or mechanisms used to explain the reaction. For example, we did not find that the ratio of coincidence to forward singles spectra is independent of angle, except possibly in a limited kinematic region, and there was no observable evidence for specialmechanisms such as (p,d) scattering and subsequent deuteron break-up.Although the main features of the data can be reproduced by a direct knockout model calcu­lation, explanations for the displacement of the angular maxima above the QTBS angles do require additional scattering mechanisms.Both a decrease in the incident proton energy before measured interaction and the subse­quent scattering of the backward emitted proton must be involved. Work on these theoretical problems is proceeding. While the data do not rule out the notion of hot spot mechanisms, they do indicate that their contribution would have to be small.In an effort to extend the measurements to fragment emission, data on the (p,pd) reac­tion from 9Be are being analysed. Although the analysis is still preliminary, the same leading proton correlation is observed but with an angular displacement to higher angles and with an increased multiplicity. It is also interesting to note that there is no degradation of the leading proton angular distribution and, in fact, the (p,2p) and (p,pd) widths are identical. This is illus­trated in Fig. 28 where data for 70 MeV and 80 MeV trigger protons and deuterons are displayed.Before the measurements can be extended to (p,pa) reactions a new chamber must be constructed. This is under way, with a final design almost completed.Experiment 143 A study by recoil detection o f proton-induced reactions o n 9BeThe acquisition of the final data for this experiment was completed in a ten-shift run during May. A summary of the previously existing data was given in last year's report. The final measurements were made at proton energies of 188, 281 and 480 MeV with emphasis on completing the systematic study of the dependence on incident energy of the (PjPo)> (P,"+) and (p, tt°) reactions at large values of q, the momentum transferred to the recoiling nucleus. The measurements for the 9Be(p, it0) 10B reaction at 188 MeV required a semiconductor telescope with a thinner sili­con AE detector (8.5 pm) than those used pre­viously. The opportunity was taken to extend earlier measurements of the elastic scatter­ing reaction to a wider range of values of momentum transfer.25(lab)Fig. 28. Energy integrated angular distribu­tions for the forward going proton triggered by either protons or deuterons at -90° in the (p,2p) and (p,pd) reactions on 9Be at 300 MeV. Data for both 70 and 80±5 MeV triggers are displayed along with the QTBS angles for each case. Representataive error bars indicate statistical errors only.Throughout the TRIUMF energy range and to values of q as high as 1 GeV/c, the 9Be (p,p0) reaction exhibits strikingly simple behaviour: to a good approximation dcr/dt depends only on q and is independent of Ep (t is the usual Mandelstam variable). The (p,ir+) and (p,n°) reactions at all but the lowest incident energy also reveal a nearly common dependence on q at forward angles (Sc .m. ^ 90°). The dependence of do/dt on Ep, however, does exhibit a broad maximum in the region of Ep = 300 MeV similar to that presented by Couvert for the ^®B(p, if*") ^ B  reaction as evi­dence in support of a two-nucleon description of the reaction mechanism. Besides essenti­ally doubling the data available on the broad dependence of the (p ,it+) reaction on q and Ep, this experiment uniquely provides the corresponding information for the (p,ir°) reaction. Some differences are noted.Some of the results of this experiment were reported at an invited talk at the Symposiumon Pion Production with Eight Ions at the September 1982 meeting of the ACS. A paper describing the results for the two-body final states is in preparation. This paper will be followed by a second summarizing reactions such as 9Be(p,Nir) 9Be and 9Be(p,2p)8Li also involving large coherent momentum transfer but with more than two particles in the final state.Experiment 152 A measurement o f the Wolfenstein R parameter in p-4He elastic scattering a t 500 MeVThe Wolfenstein R parameter in proton-4He elastic scattering at 500 MeV has been measured from 15 to 50° (lab) using the focal plane polarimeter on the MRS. The results have been published [Moss et al., Nucl. Phys. A392 (in press)].In conjunction with the existing differential cross section and analysing power angular distributions we have published, these data permit a complete determination of the elas­tic scattering amplitude (apart from a sign ambiguity and an overall phase) in this angular range. The results are shown in Fig. 29 along with a theoretical prediction which uses an optical potential obtained from fitting the cross section and polarization data.#cm (degrees)Fig. 29. Comparison of the experimental data for R, measured in this experiment, and the theoretical prediction. Representative error bars are shown for some data points.26The cross section and polarization data for p-^He elastic scattering at TRIUMF energies have resisted a satisfactory theoretical description. Neither the non-relativistic nor the Dirac optical phenomenology have been able to accurately account for these data.The measurement of a third independent elastic scattering observable, the R param­eter, can be very useful in resolving this problem.For 4He all existing optical potentials have given roughly the same prediction for R, although this prediction showed little agreement with the data. It could be con­cluded that an essential element in the des­cription was missing and that the R parameter was particularly sensitive to this shortcoming.We have analysed the three sets of data (cross section, polarization and R) using the Born approximation [Greben and Gourishankar, to be submitted to Phys. Rev. C]. This has enabled us to uniquely determine which features of the potential are responsible for the main features of the data.Our main conclusions are: (1) R measurements are very important in determining the charac­teristics of the real spin-orbit potential.In particular we find that its radius is larger than that of the central and imaginary spin orbit. (2) The real central potential has an attractive tail and a repulsive core. This is in accordance with findings for heavier nuclei. (3) The imaginary potential is very absorptive in the interior. (4) The magnitude of the spin-orbit potentials is reduced when the central potentials are described properly.The final fit was obtained using an extension of the search program SEEK, which now allows the use of potentials that do not have the standard Woods-Saxon parametrization.While our final potential can serve as input for reaction calculations, it is also useful as a means to connect experimental results and a fully microscopic description. Unphys­ical features of the local optical potential could signal the need for non-local interac­tions. This, in turn, could be due partially to isobar or more exotic effects. In fact we cannot exclude that the sizable core of the central potentials found are manifestations of non-local effects.", 0 Ca C p ,2 p )  3 0 0  MeV INCIDENT ENERGY A N A LY ZIN G  POW ER 3 0 ° - 5 5 °Fig. 30. Analysing power as a function of energy of one of the outgoing protons.Experiment 155 Quasi-elastic scattering o f polarized protons at 300 MeVOur earlier measurements of the lf0Ca(^ ', 2p) reaction at 200 MeV incident energy have been extended to 300 MeV using the TRIUMF pola­rized proton beam. The angles and energies of both outgoing protons were measured, one being detected in a magnetic spectrometer and the other in a Nal(TJl) scintillation crystal. Measurements were made in two geometries, in one of which the angles of the outgoing pro­tons were close to equality and the other in which they were very unequal. Values of cross section and analysing powers for the knockout of protons for ld3/2, 2s 1/2 an  ^ld5/2 shells in lf0Ca were obtained and are compared to DWIA calculations incorporating the spin-orbit terms in the optical poten­tials, and also to calculations using opti­cal potentials derived from a relativistic approach based on the Dirac equation. The expected j-dependence of the analysing power was seen (Fig. 30).As in our previous work, however, the analys­ing powers measured in the geometry where the angles of outgoing protons are very unequal are consistent with a value of zero for the two-body polarization parameter App, while its value for free nucleon-nucleon scattering Appee ~ 0.2. This can be seen in Fig. 30 where the value of App is roughly equal to27R ECO IL  M OM EN TU M (MeV/c )1+0Ca(p,2p)Fig. 31. Analysing power for scattering from "2s" state.Fig. 32. Experimental arrangement.the analysing power at the point where the d 3/2 analysing power equals the d 5/2 analys­ing power. Measurements for scattering from the 2s 1/2 protons, whose analysing power Ay should be equal to A|pee (if spin orbit dis­tortions are neglected), show no such effect (Fig. 31). This figure shows the ratio of Ay to the value of A|pee obtained from free nucleon-nucleon scattering, and indicates a value of Ay > Appee. We have not developed a satisfactory explanation for this behavior. The possibility that refraction effects are responsible is being investigated.Experiment 170Fission-evaporation competition in heavy nucleiThis experiment had a very successful one- week data-taking run in April, in which uranium and bismuth targets were bombarded with 450 MeV protons. The apparatus, which performed flawlessly, was designed to detect the fission fragments in coincidence with low-energy neutrons produced both parallel to and perpendicular to the direction of the fission fragments (Fig. 32). The fission fragments (FF) were detected by means of a multiwire proportional chamber (MWPC) and two parallel plate avalanche chambers (PPAC's) which measured their angle, energy and time of flight. From these data the masses of the fragments can be derived and component of velocity along the beam direction of the fis­sioning nucleus. The neutron energy was determined from its time of flight. Pulseshape discrimination was used to reject the y-ray background. The neutron counter effi­ciency was measured using a 252Cf source. The number of neutrons emitted parallel to the direction of the fission fragments compared to the number emitted perpendicularly may be used to derive the numbers of neutrons emitted before and after the nucleus has fissioned, thus enabling the competition between the fis­sion and evaporation processes to be studied.The data-taking phase of this experiment is now complete and the results are being analysed at TRIUMF and by our collaborators at the Weizmann Institute in Israel.Experiments 173, 196 Broad pionic X-raysPionic atoms provide a unique environment for the study of the ir-nuclear interaction at low energies. Their X-ray emissions have been measured over a wide range of nuclei, with recent measurements attaining a precision of 1% in the strong interaction energy shift.We proposed to extend the range of these mea­surements to larger energy shifts, specific­ally the pionic 4-3 transitions in 208Pb and 209Bi and the pionic 2-1 transitions in Na,Mg and k l .  This direction seems particularly interesting in view of the anomolously narrow widths that have been observed in the broadest levels. These very broad levels are difficult to measure because the low peak-to- background ratios make them difficult to dis­tinguish from structures in the background.28We are developing a Compton suppression spec­trometer (CSS) constructed of bismuth germanate crystals to reduce the backgrounds while enabling the experiment to utilize intense meson beams. The light yields from these rather large crystals are poor, result­ing in an energy resolution of 30% at 662 keV, a time resolution of 6 ns FWHM at 1 MeV, and an energy threshold of 50 keV. Some improve­ment in these parameters is expected through modifications to the preamplifiers.A 12-shift run in August was used to commis­sion the CSS and for a first measurement of it 208Pb and it 209Bi X-rays. The 10-segment structure of the CSS allowed us to run at rates of 300 kHz in the CSS with only 10% dead-time losses. An in-beam background sup­pression factor of three at 1 MeV was obtained.Figure 33 shows a portion of the prompt photon spectrum observed with the CSS. There is a broad structure evident near the expected location of the pionic 4-3 X-ray at 1280 keV. This structure does not appear in the 209Bi target spectra, and has a basically Lorentzian line shape. The broadened pionic 5-4 transition has also been observed with very high statistics and low backgrounds. Analysis of this data is still in progress, and we plan another run to obtain data on the other targets.Experiment 184, pd —- tn+ Experiment 187, Pion production from 10BFinal j$d -»• frr+ data were taken at 277 MeV on the Resolution spectrometer in IB. These results complement the previous data at 305, 330, 375 and 400 MeV [Lolos et al.,Nucl. Phys. A386, 477 (1982)]. The measure­ments for both differential cross section (da/dJ2) and analysing power (Ajjo) were made using a deuterated polyethylene target (CD2) rather than a liquid deuterium target which, although intrinsically superior from the point of view of signal-to-noise, was too costly to install at this stage of the pro­gram. In order to obtain an adequate signal- to-noise ratio for the solid target at back­ward angles (where the cross section is small) the associated particle (triton) was detected in coincidence with the pion. For forward pion production the cross section was large enough that adequate signal-to-noise was obtained simply by subtracting the back­ground spectra obtained for a pure carbon target. Figure 34 illustrates the currentENERGY ( k e V )Fig. 33. Spectrum of prompt photons observed by the Compton suppression spectrometer (CSS).status of the analysing power measurements for this reaction which have now been sub­mitted for publication [Lolos et^ al., TRIUMF preprint TRI-PP-82-41].The angular distributions of both the diffe­rential cross section and the analysing power were measured for 1 °B( ji, tt+) 1 ^ B using an en­riched target of 10B for incident protons of 200, 225, 250 and 260 MeV kinetic energy. Since the target was not completely monoiso­topic, data were also collected using a natural boron target (81.2% 11B). AnalysingFig. 34. Analysing power angular distribu­tions Av(6) for: • 375 MeV, A 305 MeV, and o 330 MeV from Lolos et al. [Nucl. Phys.A386, 477 (1982)]; ■ 500 MeV from Abegg £t^  al. [AIPCP 69 (AIP, New York, 1980), p. 1205]; A 277 MeV, this experiment.29d (LAB)7TFig. 35. Preliminary analysing powers for the 1 °B(^, tt+) 1 reaction at the proton energies indicated.power results for those pions leading to the ground state of 1 *B are illustrated in Fig. 35. The energy dependence is qualita­tively very similar to that for 12C(f, tt+ ) 18C [Lolos al_., Phys. Rev. C 25_, 1086 (1982)], except for a shift in energy scale.The extraction of do/df) for both reactions awaits further analysis in 1983.Experiment 189 p,n  radiochemical studyThe principal objective of this experiment is to measure the total reaction cross section a as a function of proton energy (from 200 to 500 MeV at TRIUMF) for the group of reactions 209Bi(p, ir~xn) 210-xAt where 0 < x <7.In essence radiochemical separations specific for astatine are applied to irradiated Bi foils, and the residual activity (a,y) of the heavy At reaction products measured to determine for the specific reaction.The final series of runs were performed in August and while some of these data are still under analysis, Table IV presents some pre­liminary absolute cross sections at incident beam energies from 120 to 800 MeV obtained at IUCF, TRIUMF and LAMPF by this group. It should be emphasized that these data have not yet been corrected for contributions from secondary (a) reactions. The errors indi­cated include those from counting statistics,branching ratio uncertainties, chemical effi­ciency uncertainties, etc. Chemical effici­encies were measured by direct radioassaying of the irradiated Bi foil for the production of 211At and comparing this to 211At activity in the separated sample.Experiment 201 A survey o f pion double charge exchange at low  energiesA short run was made with the QQD spectrom­eter on the Mil channel to study the double charge exchange (DCE) reaction 180( ir+ , it-) 18Ne for 65 MeV ir+ at 90° in the lab. A H2180 (gel) served as the foreground target (Q = -6.10 MeV) and a H 2180 (gel) was used for background (Q = -28.85 MeV). After cuts to assure that the detected particles were pions through the entire system, the background counts in the energy region from the 18Ne g.s. to 18Ne* (10 MeV) had been reduced to zero while nine counts remained in the fore­ground. The cuts consisted of:1) TOF to separate it ' s  from y's and e's in the channel.2) Continuous line through the spectrometer to remove it's that have decayed in the spec­trometer and scattered tt+ , s  that induce reactions in the walls of the spectrometer vacuum vessel.3) No signal from the Cerenkov detector at the exit of the spectrometer.The nine counts correspond to a very pre­liminary energy integrated cross section of2.8 yb/sr for the 180( tt+ , ir“) 18Ne reaction after 65 MeV pions at 90° in the lab. This compares well to the previous measurements inthis low-energy region of 1.7 yb/sr at 95 MeVand 0° by Burman e_t aJ. and of ~1 yb/sr at 80 MeV and 5° by Greene et al.Experiment 206  A study o f (p,n) and related reactionsThe main objectives of this study are to measure for the first time differential cross sections for inclusive energetic neutron emission on a series of targets from Be to U at selected incident proton energies.Similar measurements of energetic inclusive proton production on the same target and for the same incident energies will be performed where necessary so that a comparison of (p,n) and (p,p') can be made. Such a comparison is of value in furthering our understanding of the mechanism of intermediate proton-induced30Table IV. Preliminary total cross sections for astatine production from 208Bi target.Cross section (ub)aastatine isotopeEp 203 204 205 206 207 208 209 210(MeV)120b _ _ _ 0.6 + 0.2 * 1.3 + 0.5 —160b - - - - 4.6 + 0.9 * 4.2 + 0.8 -180b - - - - 10.6 ± 2 * 5.0 + 1.1 -188 - - - - 27 + 10 * 7.4 + 4 *200b - - - - 17.4 + 3.9 - 1.6 + 0.3 -210 1.4 + 0.7 22 ± 4 61 + 9 37 + 10 18 + 3 * 5.8 + 1 *214b - - - - 10 + 3 - 1.0 + 0.3 -225 13 + 4.5 22 + 4 42 ± 7 20 + 4 9 + 1 * 2.0 + 0.6 *252 52 + 8.5 30 + 18 46 + 9 32 + 6 9 + 2 * 1.4 + 0.2 *300 41 + 18 41 ± 6 35 + 3 19 + 2 5.6 ± 0.8 * 1.1 + 0.1 *350 30 + 7 26 + 7 29 + 7 24 + 4 5.5 + 0.6 * 2.6 + 0.4 *400 36 + 8 14 ± 2 29 + 3 19 + 3 3.9 + 0.4 * 1.2 ± 0.3 *450 24 ± 4 - 17 + 2 16 + 8 2.6 + 0.4 * 1.0 + 0.2 *480 27 + 4 22 + 2 21 + 4 11 + 2 3.4 + 0.7 * 1.5 + 0.2 *800b * * * * * * * *aThese data were obtained only from residual alpha emissions of At products; secondary contri­butions have not been subtracted yet. bData taken at IUCF (below 220 MeV) or LAMPF (800 MeV).*Data at these energies and for these isotopes are still under analysis and will be available.reactions, and the applicability of a direct knock-out model!Studies have been performed over the last ten months to explore whether satisfactory energy resolution could be obtained using time-of- flight techniques, and to investigate the nature and extent of the neutral background in the 4BT1 areas.Preliminary measurements at 200 MeV using a Ta target indicated that the signal/back­ground ratio is already satisfactory, even with a minimum amount of shielding, the ratio varying from about 10:1 at the higher neutron energies to about 1:1 at the lowest energies of interest. Minor changes in the design of the shielding and the use of liquid rather than plastic scintillators should improve this ratio, especially at the lower ejectile energies. The energy resolution that was achieved with the time-of-flight system using a 10.2 cm thick by 10.2 cm <j> NE110 scintil­lator to detect the neutrons was limited mainly by the width of the cyclotron beam burst (~2.5 ns) and is also satisfactory for this experiment.Shown in Fig. 36 is the relative cross section derived from these preliminarymeasurements. The errors indicated are sta­tistical only, and there is an overall error of about a factor of two, mainly from uncer­tainties in the beam current. The start pulse was derived from the beam pick-off signal from beam line 1 and the time varia­tion between this signal and the beam pulse on the target at 4BT1 was very carefully monitored to a precision of better than 100 ps. This level of accuracy is necessary because the cross section falls off rapidly at the higher neutron energies, so that a small error in the time (energy) measurement would lead to a large error in the cross section at these high energies. Time cali­bration of the entire system was achieved using pp scattering on a CH2 target.Experiment 211 The particle and y-ray correlation in the n~ and p  ~ captures in medium-heavy nucleiThe energetic components of n and p emission following p“ capture in medium-heavy nuclei are not easily understood on the basis of available theories of p capture or nuclear de-excitation process. It has been suggested that the pionic processes in the nucleus should be taken into account in the weak31•  SHADOW BAR OUT •  x  SHADOW BAR INX* fXI_J_______________ 1_I________ 1__________ _________5 0  8 0  110 140En ( M e V  )Fig. 36. Neutron emission spectra for Ta(p,n)X at Ep = 195 MeV, 9n = 50°, illustrat­ing the total (shadow bar out) and background(shadow bar in) differences. The cross sec­tions are subject to an overall uncertainty of a factor of two because of uncertainties in the beam current integration.hadronic current in order to explain the energetic emissions. We measured the parti­cle spectra in an experiment parallel to cor­relation study in it-  capture.The multiple particle counter system used for y“ and 7r“ experiments is a careful compromise of efficiency, timing and background conside­ration originally worked out for the tt~ capture experiment (Expt. 145). It consisted of twelve large plastic scintillators with dE/dx shields used in a time-of-flight con­figuration, and was capable of angular corre­lation with respect to y-rays and particle- particle correlations. For p” experiment the delayed nuclear y-rays detected in a 2x2 NaI(T£) were used as the time-zero signal.The results of p” experiment are still explo­ratory, but we were able to obtain prelimin­ary results for both neutron and proton spectra, as shown in Fig. 37. The neutron TOF spectrum in Fig. 37(b) shows two exponen­tial components with E 0 = 5.1±0.8 MeV from 11 to 32 MeV and E 0 = 11.9±1 MeV extending from 32 to 80 MeV, where E 0 is used as in the expression exp(-E/E0). The proton TOF spectrum in Fig. 37(a) shows an energetics-OELd-oC|"DSbcj"D1.00 .50.20.10 .0 50.02component with a slope of E 0 = 14±2 MeV ex­tending to 90 MeV. The abrupt drop in proton spectrum below 35 MeV is due to protons stop­ping in dE/dx counters. The emission of proton is one order of magnitude less than the neutron as expected, but the slope of the two spectra is nearly equal, posing serious problems for interpretation by impulse approximation.The investigation of the it- capture in medium- heavy nuclei is now in its final phase and a preliminary report has been published [Levin et al., Phys. Lett. 114B, 427 (1982)]. We continue to study the neutron and proton spectra in coincidence with discrete nuclear y-rays detected by Ge(Li) counters, to exhibit correlations of spectra to neutron multiplicity and residual nuclear states. A discrete component in the pre-compound neu­tron spectra is resolved for the first time, and its correlation to the population of high spin nuclear states is observed as in typical cases shown in Fig. 38. In this figure we show the neutron spectra in coincidence withPARTICLE ENERGY MEVFig. 37. Particle spectrum from y“ capture in 155Ho measured by time of flight, (a) pro­ton spectrum, (b) neutron spectrum.32Fig. 38. Neutron spectra in coincidence with individual transitions in ground state bands for neutron multiplicities of 5 and 7 for 165Ho target.individual nuclear states in the ground state band for the cases of neutron multiplicity of 5 and 7. The origin and nature of the dis­crete feature of neutron spectra and the nuclear spin-dependence of the neutron multi­plicity and spectral shape are still uncertain and pose a major challenge to detailed pre­equilibrium calculations.Experiment 212 In search o f a tredecabaryon resonanceThe objective of this experiment is to search for resonant structure in the compound nucleus 13N by measuring the excitation func­tions for the elastic and inelastic scatter­ing of protons from 12C. The medium resolu­tion spectrometer is used to identify protons scattered at backward angles in the popula­tion of specific low-lying states in the residual nucleus. The differential cross sections will be measured as a function of the incident proton energy as that energy is varied from 180 to 500 MeV in 2 MeV steps. It is anticipated that this range will be divided into several segments and that over each of these the scattering angle will be stepped to keep the value of momentum trans­fer a constant.Initial feasibility studies were carried out during a run of 5 shifts in August with protons incident at an energy of 300 MeV on natural graphite targets of three different thicknesses. Data were recorded at labora­tory angles of 29°, 50°, 76° and 86° for protons populating both the ground and first excited (4.44 MeV) states of 12C. This run confirmed the basic suitability of the MRS in the measurement of cross sections as small as 3 nb/sr (observed for the elastic scattering from 12c at 86° for which the momentum trans­fer q is 1.05 GeV/c). At the larger angles the rate at which data could be accumulated was limited by neutron radiation levels outside the proton hall which restricted the beam current to a maximum of 7 nA with a target of surface density 0.35 g/cm2.A recent test run utilized 6 shifts in December to extend the measurements at 300 MeV with a target of surface density0.107 G/cm2. Preliminary angular distributions were obtained for the lowest two states in 12C over the range 50° < 9iab < 130° as well as additional data on the states at 9.64 and14.08 MeV. Concrete shielding added prior to the run permitted at the larger angles the use of a beam intensity of 100 nA (the maxi­mum presently allowed by the licence in beam line 4B). This improvement was critical in the measurement of the angular distribution of the ground state for which at 130° (q =1.35 GeV/c) the differential cross section was observed to be ~0.06 nb/sr.The measurements completed in 1982 are the essential prerequisites to undertaking at least the initial segment of the resonance search. It is anticipated that the upgrade of the MRS to be completed early in 1983 will improve the performance of the spectrometer under conditions of high count rates in the electronics at the entrance to the quadru­pole. The changes necessary to permit ope­ration of beam line 4B at intensities above 100 nA are also being investigated.33Experiment 223 The 2H(p,2p)n reaction and momentum distribution o f the deuteronAn experiment is being prepared studying the 2H(p,2p)n reaction in the context of the plane wave impulse approximation under kine­matic conditions chosen to minimize and accentuate the various processes competing with quasi-free scattering. The experiment will be done using 500 MeV unpolarized pro­tons and will consist of the following:1) A measurement of the coplanar symmetric angular distribution from 38°-38° to 57°-57° covering recoil momenta between -0.055 and +0.357 GeV/c with a 3% absolute error for recoil momenta less than 0.100 GeV/c and a 10% absolute error for higher values of recoil momentum.2) Measurement at a fixed momentum transfer to the scattered proton both in the quasi- free region where the recoil momentum can be as small as zero and off this region for recoil momenta up to 0.520 GeV/c.3) Measurements at equal relative energies for all three pairs of nucleons for various recoil momenta.At present a dual liquid hydrogen-liquid deuterium target assembly is under construc­tion at the Technical University at Delft, The Netherlands. The cryostat will make use of a commercial cryogenerator. The target cells will have a thickness of approximately 150 mg cm-2.Experiments 199, 209, 178, 177, 166, 202, 203, 226 Pion absorption and scatteringThis report is broken into three segments corresponding to the progress of TRIUMF experiments with pion absorption and scatter­ing on complex nuclei. A considerable amount of beam time has been available this last year and there have been results in these PISCAT group projects.Pion absorption experiments with ir+ and ir“ (Experiment 199)The reactions ir++ 3He p+p+p and ir-+ 3He p+n+n have been studied using a neutron/ proton scintillator array in coincidence with a Nal proton detector array as shown in Fig. 39. The data comparison between these two experiments is a measure of the relativeimportance of absorption on T=0 and T=1 nucleon pairs. For example, Fig. 40 shows experimental results of the reactions for the proton detector at 120°. The neutron/proton detector was placed at an angle corresponding to the two-body irD 2p second proton angle for 45°. The tt++ 3He * p+p+p shows a pronounced peak at the energies in the two arms corresponding to absorption on a quasi- deuteron with the third proton a spectator. There is likewise a corresponding peak, though diminished, in the it- case. Comparing these results with others [Ashery et al. and Gotta et_ al^ .], as shown in Fig. 41, indicates that current theoretical estimates of absorp­tion on a T=1 nucleon pair are overestimates.These experiments will be continued at higher energies and we assume the detector arms will be available to us in the summer of 1983.The 3He target is being reconstructed for these runs.Two-body absorption reactions ir++ 6Li 3He+3He (Experiment 209)The preceding experiments on helium are a study of the most dominant absorption pro­cesses for pions. It is possible for a pion to be absorbed on a larger aggregate of a nucleus than a two-nucleon pair. The two- body reaction 3He+3He -»• ir++ eLi has been studied at T 3He = 280 MeV [Bimbot _et al^ . ] and now we have studied the inverse reaction at T-^  = 60, 75, 90 and 140 MeV.Tests have been made with scintillator arms that were designed to stop Z>2 particles but pass the majority of absorption products,34F i g .Fig. 40. (a) tt+ spectrum and (b) it- spectrum.proton m NoiK ( m ,,. )41. Energy dependence of reaction Tf-^He.3TD\bPION E N E R G Y  (M e V )Fig. 42. Energy dependence of iT++ 6Li.1000•  ORSAY ▲ LAMPF-CMU ■  TRIUMF-UBCHUBER etal .  @30°GERMOND et a l . \  @30 °-  7T+  +  6 L i — 3 H e + 3 He ENERGY DEPENDENCE35<-> 1.2 - wX2_J______I______I______I______1_4 5 . 0  7 0 . 0  9 5 . 0  1 2 0 .0  1 4 5 .0ANGLE (c .m . de g )AIL ■ 5 0 m fmAr_ = AlLANGLE ( c .m . deg )Fig. 43. C-N ratio experiment, n+ .elec.scat.1.31.1toXtn0 .7_1_ _L_2 0 .0  4 5 . 0  7 0 . 0  9 5 .0  12 0 .0ANGLE ( c.m . deg )Fig. 45. 31t> 32S 7t— ratio.protons with energies greater than 30 MeV.The tests were made at = 60, 75, 90 and 140 MeV. The overall coincidence rate was about one a second after quasielastic events (10 per second) were removed by raising the E threshold on the back angle counter. The 3He-t-3He coincidence rate resulted in about 70 counts in 20 h. These data are plotted in Fig. 42 on a cross section curve due to Huber where an intermediate state calculation is employed.Pion elastic and inelastic scattering - The QDD spectrometer(Experiments 178,177,166,202,203,226)The QQD spectrometer is designed to use pion beams from M13 and first experiments have been completed this summer. These experi­ments were elastic scattering experiments.As the resolution of the spectrometer and channel combination improves inelastic scattering experiments will be performed.The channel and spectrometer tunes and con­figuration were adequate for a 1.5% Ap/p overall resolution so that elastic scattering experiments were performed. Figures 43 and 44 show the preliminary results of ir+ scat­tering on isotopes of C, N and 0. The central curve corresponds to established charge radius of the nuclei while the outer curves correspond to a 50 mfm difference from the accepted charge radius differences.These preliminary data show the consistency of the technique to find nuclear radius differences with elastic scattering ratio differences.In addition to the 36S measurements performed earlier an elastic scattering experiment on 34s was performed. The preliminary results from this experiment are presented in Fig. 45. The preferred neutron radius difference between 34S and 32S is about 100 mfm. More analysis is under way for these data.7 7 + E LA STIC  SCATTERING RATIO Tt +=  5 0  MeV= ArP, 'elec.scat. Afp = +  5 0 m fm4 5 . 0  7 0 .0  9 5 .0  1 2 0 .0  1 4 5 .0ANGLE ( c.m . d e g )Fig. 44. N-0 ratio experiment, tt+ .77 +  E LA STIC  SCATTERING RATIO T^ + = 5 0  MeV= - 5 0 m f mOtoOa>7 7 “  E LASTIC  SCATTERING RATIO Tw - = 5 0  MeVA rn = - lO O m fmA rn = +100 m fm364 QQD SOLID ANGLE/ Vt *ix CARBON t  •  HYDROGEN- 2 0  -10 0 10 20 A  p /p  (%)Fig. 46. Solid elastic scattering has also been taken to establish the solid angle acceptance of the spectrometer. Figure 46 shows the results of the measurement. This confirms one of the design aims of the spectrometer system. It is clear that a remaining objec­tive - resolution - depends on the channel- spectrometer combination. A channel tuning run has been performed to remove quadrupole steering effects in the second half of the channel. The results of these tests are reported in the QQD spectrometer section, p. 98.2 6toECD2<Q_)Ocn136 .537RESEARCH IN CHEMISTRY AND SOLID-STATE PHYSICSExperiment 140 Transfer effects for stopping n~ in H2-D2 mixturesA very successful run In September completed the data-taking for this experiment. Nega­tive pions were stopped in various mixtures of H 2 and D 2 as well as in HD gas. The TINA crystal is used to determine whether the pion ends up attached to the hydrogen or the deuteron. For pions which react with a proton the clear signature is the charge ex­change reaction Tr“p -*■ ir°n which has a very low probability for the deuteron (~10-1*).A large quantity of HD was needed for this experiment, so it was decided to manufacture this locally. In co-operation with J. Stadlbauer of the Chemistry Department at UBC, sufficient gas for this experiment was produced with about 97% HD molecules. This was then passed through high-pressure com­pressors to attain the pressures needed for this experiment ( ~100 atm).Several pressures were used in the experi­ment and all the effects appeared to be inde­pendent of pressure, although a final state­ment awaits a detailed analysis of the backgrounds which change with pressure. It was found that for H 2-D2 mixtures there is about a 2 0 %  transfer from hydrogen to deuterium for mixtures with more deuterium than hydrogen. For the case of HD there was found to be a 40% transfer to deuterium, presumably consisting of a 2 0 %  effect when the ir~ first meets the HD molecule, followed by another 2 0 %  transfer if the it-  first chose the hydrogen. This confirms our earlier ob­servation of an anomaly in liquid deuterium when we detected the reaction ir”d TT°nn at rest.A preliminary analysis of our data is presented in Fig. 47. Here the probability of stopped pion capture on protons in the gas mixture is shown, W(H2+D2) divided by the probability of stopped pion capture on protons in the HD gas, W(HD). From this early analysis W(H2+D2)/W(HD) is about 1.20 for pressures less than 70 atm and may decrease a little at 100 atm. Mesomolecular effects have been seen before for hydrogen in different chemical environments [see review by Horvath, Radiochimica Acta _28, 241 (1981)]. Ours is the first result pointing to the role of the reduced mass in the pirdmolecule, this being the only obvious param­eter distinguishing the two types of gas target. Indeed, the result comes surprising­ly close to what one expects from the model of large mesic molecules if the de-excitation process of the tt were governed by dipole gamma transitions. In this case the ratio of dipole rates depends on (m^/m^p )^ . Further investigation is needed to establish if this speculation is responsible for the observed effect.The detailed analysis of this experiment is continuing and will be published soon. A preliminary report was given by K. Aniol at the meeting of the Nuclear Physics Division of the APS, held at Amherst in October.Experiment 147 Formation and reactivity o f muonium in gasesMuonium formation in vapoursOur previous work on y+ charge exchange and muonium (Mu) formation in different gases has now been published [Fleming et aJL., Phys.Rev. A 26^ , 2527 (1982)]. We have taken addi­tional data on a variety of vapours; water, methanol, hexane, c-hexane, benzene, TMS and all the chlorosubstituted methanes (CHjCi. is in fact a gas at room temperature). The pro­cedure utilized was basically the same asPRESSURE ( A T M )Fig. 47. The relative probability of stopped pion captures on protons in gas mixtures of hydrogen and deuterium.38Fig. 49. Pressure (electron density) of the total muon polarization seen in dif­ferent vapours. The solid line repre­sents a fit to a simple charge exchange model, as discussed in the text.- 0.10Fig. 48. The MSR signal obtained in water vapour at a pressure of 1080 Torr in a magnetic field of 6. 5  G. The solid line is a x 2 fit to the data.- 0.20 0.0 1.0 1.5 2 .0T im e  in  fis (3 0  n s /b in )T o ta l  P o la r i z a t io nValence Electron Density (10“ e_ crrf*)before, except vapours were introduced into the target vessel by heating the corresponding liquids to a high vapour pressure (~200°C), having first degassed them (to remove dissolved 0 2) by a series of freeze-pump-thaw cycles. A typical muonium spin rotation (MSR) signal is shown in Fig. 48, obtained in H 20 vapour at a pressure of 1080 Torr in a magnetic field of 6.5 G.As found in our earlier study, the measured amplitudes of both the Mu (Aj.ju ) and diamag­netic muon (Ap) liquids are strongly pres­sure dependent, reflecting the time spent as "singlet” muonium in the charge exchange regime. This time is inversely proportional to the pressure (or valence electron density) of the gas. The absolute total polarization, Ptot = Pj4U + Pp, can be defined relative to 100% diamagnetic signal in aluminum. This sum is shown as a function of electron density for a variety of vapours in Fig. 49 [Arseneau, M.Sc. thesis, in progress]. The solid curve represents a fit to a simple model, Ptot * sin(w0t)/w0t> where t is the time spent in the charge exchange regime.This only gives a qualitative account of the data, and a much more sophisticated model is currently being developed [Turner, TRIUMF Theory group]. The most important result to be learned from Fig. 49 is that the total polarization is asymptotic to 100% in the limit of even moderately high pressures; i.e. there is apparently no missing or "lost" polarization, P 2, in gases, in contradistinc­tion to the prevailing situation in the liquid phase [Percival, Radiochimica Acta 26,1 (1979); Walker, Hyp. Int. 8_, 329 (1981)].Representative results for the high pressure limit of the absolute polarizations found in our present work compared with the corre­sponding values found in the liquid phase are given in Table V. In order to be able to make this comparison was the prime motivation of the present study, because there has been a lot of interest in recent years centred around the mechanism for muon thermalization and Mu formation in condensed media. In the "spur" model [Percival, o£. cit.] the distri­bution of muon polarization is thought to be the consequence of specific intraspur reac­tions, as a result of radiolysis processes created by the thermalization of the ener­getic positive muon. In the "hot atom" model [Walker, op. cit. ], as in the gas phase, Mu is thought to form at epithermal energies by a charge exchange process prior to its thermalization. Since one would not expect spur or radiolysis processes to make a signi­ficant contribution in gases at moderately low (~1 atm) pressures, it was important to measure the muon polarization fraction in vapours in order to, hopefully, be able to shed more light on the above controversy.This we have now done (Table V). The data clearly show that the mechanism(s) for the distribution of muon polarization are clearly different in the gas and in the condensed phase. In every case, we see appreciable Mu39Table V. Comparison of the distribution of absolute muon polarization between liquids3 and vapours^Target Phase PM PD PLh 2o g 93 + 4 7 ± 4 0I 19 + 2 62 ± 2 19 ± 2c h 3oh g 87 + 2 13 ± 2 0I 23 + 3 62 ± 3 15 ± 20 gH ^ g 81 + 8 19 ± 8 0a 13 ± 3 65 ± 3 22 ± 4^ 6^  12 g 83+ 6 17 ± 6 0SL 20 + 3 69 ± 3 11 ± 2C C ^ g 48 + 3 52 ± 3 0% 0 100 0TMS g 87 + 4 13 ± 4 0a 21 + 3 53 ± 3 26 ± 4aTaken mostly from summary of Walker [Hyp.Int. _8, 329 (1981)] .^From Expt. 147 results [Arseneau, M.Sc. thesis, in progress].formation, of order 90%, vs. about 20% in liquids, with the exception of carbon tetra­chloride, where ~50% Mu is seen in the vapour but no Mu at all is seen in the liquid phase. The vapour phase data can be readily under­stood in terms of a charge exchange/hot atom model, but not the liquid phase results. It is possible that efficient thermomolecular (perhaps hot ion) processes are responsible for the large diamagnetic fraction seen in the liquid phase, but it has also to be recognized that a spur model is a likely, and in fact now much more credible, possibility. Further work on the interpretation of these data is in progress.Molecular ion formation in doped rare gasesAs noted in last year's report, we have now constructed a new set of Helmholtz coils which, in principle, provide magnetic fields (in range 4  G to ~ 500 G) 100 times more homogeneous than our earlier (smaller) "work­horse" coils. In practice, their performance has been about 10 times worse than this in the unfavourable magnetic environment present at the end of the (M20) beam line. Our goal is to be able to measure slow muon relaxation processes in gases in order to compare with abundant NMR data in gases, but these typically are expected to exhibit relaxationtimes >100 ys, and the above-mentioned factor of ten will have to be recovered before such measurements become realizable. Nevertheless we have been able to measure a variety of muon relaxation processes in doped (rare) gases in the present magnetic field environment.An appreciable amount of this type of study had already been accomplished in our smaller set of coils, as outlined in last year's report. However, with the availability now of both a larger and more homogeneous field, we have discovered that our earlier measure­ments of the muon (thermal) relaxation rate for Xe and CH^ added to neon are incorrect. There are, in fact, two muon relaxations seen upon the addition of trace amounts of Xe to Ne, as shown by the ySR signals of Fig. 50 in a 125 G magnetic field. The top part of the figure is for pure neon at 1500 Torr pressure while the bottom part shows the effect of adding ~200 ppm of xenon. There are clearly two relaxations present upon the addition of xenon, a very slow one (X2) at later times1376T: 1500 to rr  Ne 125 G0.40.2 - - 0.2 --0 4  I I_____I___ 1___I______ I____I --0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.CTim e in /xs (40  n s/b in )Fig. 50. (top) The ySR signal for muons stopped in Ne at 1500 Torr pressure in a 125 G magnetic field. The solid line is a x 2 fit to the data assuming a single exponential re­laxation. (bottom) As above but for 200 ppm of added xenon. The x2 fit is for a two-component relaxation function, as explained inthe text.40[ x e ]  x 10 a t o m s  ccFig. 51. The measured fast relaxation rate (Xj) vs. Xe concentration. The solid line is a straight line fit to the data, from which( 3.1 ±0.3 )the bimolecular rate constant k10“  10 cc atomand a very fast one (Xj) at early times, which is gone after ~500 ns. These data necessitate a fit to the more general ySR signal S(t), given by-X.t -X„tS(t) = Aj e 1 (cos wt+<j>) + A 2 e 1 (coswt+<|>),X. X2 C1)where Aj1 and represent the initial amplitudes and relaxations of the fast and slow components, respectively. Note that there is also an effect of the amplitude of the ySR signal upon the addition of xenon.This is due to epithermal Mu formation in thecharge exchange process; indeed, the muon amplitude is asymptotic to zero (correspond­ing to 100% Mu formation) at Xe concentra­tions of ~500 ppm [1981 Annual Report; Phys. Rev. A 26, 2527 (1982)]. Similar effects to those seen in Fig. 50 have been seen at dif­ferent Xe concentrations, and the correspond­ing relaxation rates for the fast signal, Xj, are plotted in Fig. 51; the slope of a pre­liminary straight line fit to the data gives the bimolecular rate constant kj = (3.1 ±0.3) x io“ ^  cc atom-1 s“ 1, about 10 times faster than given in last year's report based on a simple exponential fit to the data (indeed, Fig. 50 in that report already hints at the presence of two relaxations). We have also carried out measurements of the relaxation of the ySR signal for CH^ added to neon and find essentially no effect; i.e., there is only a very long-lived signal, in marked contrast to the case of xenon.Our preliminary interpretation of those data is as follows. As discussed previously, the muon cannot be free in the gas, otherwise we would see a comparable thermal relaxation for the process y++X -*■ Mu+X+ where X = Xe, CH^(or Mt3), since all are exothermic for Mu formation. Hence, the muon must be bound in a molecular environment, more surely Ney+ in a Ne moderator and Hey in a He moderator (further experiments with the new coils in He have not yet been carried out). Recent theoretical calculation of the binding energy and no vibrational spectrum of Ney+ (and Hey+), motivated by the present TRIUMF work [Fournier and Govers, J. Physique-Lettres 43, 483 (1982)], show, moreover, that these molecular ions must react in excited states (Ney+)* since the g.s. binding energy is greater than the exotherminicity for Mu form­ation (by 0.4 eV in the case of Ney"*~). Hence the following reaction scheme with readout X is envisaged:< Mu + Ne + X+ (2a)yX+ + Ne (2b)Reaction (2a), resulting in Mu formation, is responsible for the fast relaxation seen in the case of Xe, since, at thermal energies,Mu is formed at random times and hence precesses incoherently in the applied field, leading to a relaxation of the muon signal itself. Reaction (2b) again places the muon in a diamagnetic environment and is not expected to lead to any appreciable relaxa­tion of the muon signal; it is the analog of well-known proton transfer reactions and is thought then to be responsible for the long- lived signal seen. In fact, there is a measurable slow relaxation in the case of X = Xe (k 2 = 0.018 ±0.008) x 10“ 10 cc atom s-1), comparable to that found earlier for X = NH3 (0.05±0.02) but there is essentially no relaxation for the case of X = CH 1+ in neon (k2 = (0.01±0.01) X 10-!0 CC atom-1 s-1).The fact that there is no fast signal seen for either CH^ or NH3, although both of these cases are even more exothermic for Mu forma­tion in collision with (Ney+)* than is Xe (in fact, from the molecular ion g.s. in the case of NHj), is a dramatic and surprising result. It suggests that there is a very fast muon transfer reaction occurring in these cases, much faster than the maximum rate expected on the basis of the classical Langevin theory of ion-molecule reactions, which generally work well for a wide variety of such reactions. These data suggest, in fact, that quantum tunnelling is enhancing the transfer process, which, if true, would be the first time that such an effect has been established for the41T e m p e ra tu re  (K )Fig. 52. A log-log plot of the measured depolarization rate constant Kp vs. T for the spin exchange reaction Mu+02.(diamagnetic) muon. The importance of quan­tum tunnelling has heretofore only been established in the reactivity of the (para­magnetic) muonium atom [Conner, Hyp. Int. J3, 423 (1981)]. See also subsequent section. A paper on these data has been written for sub­mission to the J. of Chemical Physics, and further work will be carried out next spring with the completion of the new M20 channel.Muonium chemistry and reaction dynamicsIn the spring we carried out measurements of the temperature dependence of the reaction rates of Mu+02 and Mu+C^H^, down to ~90 K, using a new "cold can" that we had constructed for this purpose. This extends the temperature range of our earlier study on both of these systems.The Mu + 0 2 reaction is a spin-exchange reac­tion, in which the electron polarization that is shared with the muon at time 't’ is suddenly changed as a result of collisions with the paramagnetic 0 2, resulting in an effective loss of muon polarization. In our earlier study of this reaction [Mikula et al., J. Chem. Phys. _75_> 5362 (1981)], we concluded that the cross section for spin exchange with 0 2 was essentially independent of temperature in the range ~300-500 K, in agreement with available H atom data but in disagreement with current theoretical calculations [Aquilanti et al., Hyp. Int. 8 ,^ 347 (1981)].io o o / t e m p e r a t u r e  ( kh )Fig. 53. An Arrhenius plot for the reaction of Mu with ethylene (top data points) compared with the reaction of H and D with ethylene (bottom lines). Note the obvious break in the slope for the case of Mu which is not at all evidence for the cases of H and D. These latter data are from Sugiwara et aJL. [Chem. Phys. Lett. 78 , 259 (1981)].However, the temperature range was relatively small and thus it was important to be able to extend it, in order to make a more meaningful comparison with theory. Our results for the depolarization rate constants Kp as a function of temperature are shown in Fig. 52, including those from an earlier study.Figure 52 is in the form of a log-log plot (Kp(T) = A"Tn ) and if the spin exchange cross section were indeed temperature inde­pendent, the data of Fig. 51 should lie on a straight line with slope n = 0.5, reflecting only the temperature dependence of the relative velocity in the collision process. This is not the case. Although these data can be fit to a straight line dependence (n ~0.7±0.1), there appears to be signifi­cant curvature at both the low and high temperature ends. We are currently trying to understand the correct interpretation of these results, which may necessitate the taking of further points at low temperature in order to confirm the trend to curvature seen in the data in this region.The chemical reaction Mu+C^H^ is of a total­ly different nature, as outlined in the 1980 annual report. At that time we had not been able to extend our temperatures below 300 K,42which was necessary in order to completely overlap with available H and D atom data [Sugawara et al., Chem. Phys. Lett. 78^ 259 (1981)]. This we have now done. Our complete data, in the temperature range ~150-500 K, is shown in the form of an Arrhenius plot in Fig. 53, which is compared with both H atom and D atom data in the same temperature range. This is the first time that it has been possible to compare the re­activity of Mu and H over such a wide tempe­rature range. The comparison is dramatic and indeed illustrative of the importance of studies in muonium chemistry. As noted several times in this work, the unprecedented mass difference between Mu and H atom iso­topes provides for the possibility of enorm­ous isotope effects in chemical reactivity, the prime motivation of our studies in the first place.In a bulk chemical kinetics experiment such as performed in muonium chemistry, the bi­molecular rate constant is related to the cross section a(E) for the collision process by.3/2k(t) =8_Try1/2/ ikBTC  a(E)E e E/kBT dE o (3)In Eq. (3) note that there is a trivial "kinetic" isotope effect, predicting for example kj4u/kjj/kp ~ A.4/1.4/1.0, comparing the reactions of M, H and D atoms. This is essentially exactly what is shown by the data of Fig. 53 at high temperatures, where the reaction is expected to be dominated by classical effects. At low temperatures on the other hand, H and D + C 2H It continue to behave classically but Mu is now dominated by quantum tunnelling, as evidenced by the dramatic break in the Arrhenius plot; indeed, at ~20 K, the ratio kj^ u/kE ~ 18! This is certainly the first time that such curvature has been seen in an Arrhenius plot in Mu chemistry and may well represent the most unambiguous example of the presence of quantum tunnelling in any chemical reaction. This work is currently being written up for publication.Experiment 150Utilization o f backward muons to study muonium reaction intermediatesThe overall objective of this project is the application of muonium as a substitute for H to elucidate problems in H atom chemistryare not amenable to study by more convention­al means.There were three main areas of experimental activity in 1982, each of which is discussed below. In addition, the analysis and inter­pretation of some earlier work was completed, leading to the publication "Spin depolariza­tion in muonium by hydrated electrons" [Percival jrt al., Chem. Phys. Lett. SU, 1 (1982), TRIUMF preprint TRI-PP-82-23].Muonium in iceThis year it had been planned to devote con­siderable time to the study of muonium forma­tion in frozen aqueous solutions (see next section). However, we began with the pure solvant, i.e. ice, and our discovery was so profound that our efforts were concentrated in a new direction. We wanted to check if the physical state of an ice sample has any effect on the muonium formation probability, so we specially grew a pure single crystal.All previous ySR studies on ice have been with polycrystalline samples. We discovered a two-frequency precession of muonium at low magnetic fields where degenerate transitions were expected (Fig. 54). The phenomenon is just that found by Brewer et^  al^ . in quartz (Expt. 154). It is due to a previously unknown anisotropy in the muonium hyperfine interaction. We investigated the effect in both H 20 and D 20 and at a number of tempera­tures. We tested the orientation dependence of the frequency splitting, and found the expected (3 cos20 - 1) dependence (Fig. 55). From measurements at higher field we also determined the isotropic part of the hyperfineTime/usFig. 54. Muon asymmetry in a D 20 crystal at 146 K oriented with its c-axis parallel to the field of 10 G and perpendicular to the muon polarization. The precession signal contains a low-frequency muon component in addition to the two beating muonium frequencies.439 /degreesFig. 55. Muonium splitting in H 20 as a function of the angle between the crystal c-axis and the applied magnetic field (o 5 G, • 10 G, P 20 G). The measured splittings have been corrected for Zeeman contributions.tensor. Our results are isotope and tempera­ture independent:A | - A j_ = 1.27 + 0.03 MHzA 0 = j  (A | + 2AjJ = 4440 ± 100 MHz .A paper has been accepted for publication [Percival e£ al^ ., Chem. Phys. Lett., TRIUMF preprint PP-82-33].Although the ice work represents a departure from our original plans for the study of muonium formation, they do in fact fit in with the long-term objectives of the project, since we are obtaining hitherto unknown in­formation on H atoms. Consider the followingpoints:1) H has not been detected in ice between 50 K and 160 K.2) H has not been studied in single crystalsof ice.3) Hyperfine anisotropy was not known for H in ice, so that studies of esr linewidth [Shiraishi et^a^., J. Phys. Chem. 80, 2400 (1976)] did not take it into account.4) By analogy with the quartz results we postulate that the Mu (H) axial hyperfine anisotropy arises from diffusional motion of the atoms in a preferred direction, along the c-axis channels. Anisotropic diffusion has been measured for He and Ne, but has never been studied for H in ice.In view of the important implications for H, we propose to continue our studies of muonium in ice in the coming year. In particular, we intend to measure the muonium spin relaxation rate as a function of temperature for both H 20 and D 20 crystals. These results will then be compared with theoretical predictions based on a model describing anisotropic dif­fusion, to test the hypothesis of motion along the c-axis channels. Muonium ampli­tudes can also be determined with relaxation rates, so we can also check the temperature dependence of muonium formation probabilities that was previously found for polycrystalline samples.Frozen aqueous solutionsSo far we have only made a few preliminary tests on glass-forming solutions of inorganic salts in water. The results are significant, however:1) The diamagnetic fraction in 10M K0H and 10M LiCl glasses falls with temperature.2) The muonium signal disappears at low tem­perature in LiCl. This is due to fast spin relaxation, not inhibition, and suggests that muonium is trapped in the glass, unlike the situation in ice.3) The diamagnetic fraction increases when the LiCl glass contains a small concentration of K 2CrO[+. This agrees with our experience with room temperature aqueous solutions [Percival, Hyperfine Int. 315 (1981)], but in the glass the contribution from thermal reaction is quenched.In the coming year we hope to obtain full in­formation on these points. The temperature dependence of the diamagnetic signal in 10M LiCl will be fully mapped, and we will attempt to follow the muonium signal to lower temperatures by substituting D20 for H-,0, and if necessary changing to a non-magnetic anion. Once the pure glass has been charac­terized we will measure enhancement of the diamagnetic fraction (and muonion inhibition, if possible) by added electron scavengers.Muon relaxation in paramagnetic solutionsDuring the past year we completed an exten­sive study on nuclear magnetic relaxation of very concentrated Mn 2+ solutions by pSR. The rationale of the work was to explore spin- exchange between Mn2+ ions under conditions where conventional proton magnetic resonance44is not possible. The experimental approach adopted was to make muon Tj and T 2 relaxation measurements over a very wide variation of magnetic fields (50-4000 G). The muon simply replaces a proton in the solution in a statistical manner, and thus (apart from changes in magnetic moment) the information should be identical to that of NMR. The utility of MSR is that relaxation times of 10- 5-10-8 s are easily accessible and wide variation of the magnetic field is simple.In dilute solution scalar relaxation which is modulated by electron relaxation predom­inates for Mn2+, and it was felt that a field dependence study of pSR relaxation would yield electron relaxation times. It turns out that the shortening of electron relaxa­tion by Mn2+ - Mn encounters reduces the scalar contribution sufficiently that we observe predominantly dipolar relaxation.From a study of the concentration dependence of relaxation as a function of field in con­centrated Mn(N03)2 and a study of solutions of composition CaxMn(^_x)(NO3)2 • 6H20 (x = 0-0.965) as a function of field (Fig.56), one can obtain reorientational correlation times, electron relaxation times and metal ion-muon distances. We see no evidence for direct Mn2*- - NO 3" interactions, and also the reorientational times show almost no depen­dence on solution viscosity over very large ranges contrary to expectation. This study is the first detailed magnetic resonance study of a concentrated paramagnetic solu­tion, and there is still much to understand.A first paper has been submitted for publi­cation, "Nuclear magnetic resonance in very concentrated paramagnetic electrolyte solutions: Muon spin rotation study of manganese (II) nitrate", [Newman et al., J. Soln. Chem.].Fig. 56. Muon spin relaxation rates of mix­tures of calcium and manganous nitrate in aqueous solution as a function of magnetic field.temperature, viscosity and dynamic ranges are more variable.During 1982 Expt. 157 was assigned 49 shifts on M20, of which some 41 were fully usable. Several aspects of the study were undertaken, including the following:(1) Aqueous solutions of nickel cyclam were used to test for spin-exchange interactions. This d 8 solute ion can be altered from an octahedral (paramagnetic) complex to a square planar (diamagnetic) one merely by adjustment of the solution's ionic strength. A hundred­fold change in the muonium rate constant occurred as the optical absorption spectrum changed, thereby providing convincing evidence for spin-conversion from 'triplet' to 'singlet' muonium [Stadlbauer ££ a^., J. Amer. Chem. Soc., in press].Experiment 157 The chemistry o f muonium atoms in condensed mediaBy applying the muon spin rotation (ySR) technique to chemical systems one can observe several fundamental physico-chemical pro­cesses involving muonium atoms, as they occur and with good sensitivity. Experiment 157 covers a broad range of studies associated with the kinetics and mechanism of the reac­tions of muonium, and its formation, in liquids and solids containing a variety of solutes. Many of these have involved organic and inorganic solutes in water - related to the 'chemistry of life'. Others, however, have utilized pure organic liquids where the(2) Addition reactions of muonium to cyanides were shown to depend on the nature of the CN group by comparing the rate of inorganic ions (CN-, Cd(CN)2-) with organic nitriles (CH3CN, CH2CNC02-). Quite different kinetic isotope effects and Arrhenius parameters were found [Stadlbauer et^  al_., J. Phys. Chem., in press].(3) Muonium was observable with a long chemi­cal lifetime in neopentane ^(CHg)^], a mole­cule in which there are none of the relatively weak methylene groups. This material was studied over a broad range of temperatures as both a liquid and solid. The muonium relaxa­tion was faster in the solid phase, but the yield did not change at the phase transition [Stadlbauer jil^ ., Can. J. Chem., Leo Yaffe issue, in press].45Frequency (MHz)Fig. 57. Fourier transform of the ySR spec­trum at 3400 G transverse field in a mixture of 85% benzene/15% styrene. D is the diamag­netic muon frequency, Sj and S2 the radical frequencies from styrene (N.B. vinyl not ring radical), B 1 and B2 from benzene.(4) Muonium reactivity studies towards vinyl monomers were completed in 1982. These results were presented at the annual spring ACS meeting, where the editor of ACS publi­cations happened to pick this paper for an editorial write-up in the Society's magazine[Chem. & Eng. News 60(5), 31].(5) pSR was further used to study the free- radicals formed on muonium addition to adouble bond. In a series of experiments onmixtures of benzene and styrene both radicals were observed with the formation of the radical from styrene (only the one formed by addition to the vinyl bond) being favoured over that from benzene by some 5 to 1. The Fourier transform of the MSR spectrum in a mixture of 85% benzene/15% styrene is shown in Fig. 57, where the power levels of the two pairs of precession frequencies are seen to be comparable. These results suggest fast intra-molecular conversion.(6) Anti-inhibition experiments were started in order to make a direct comparison with positron annihilation studies, using C^Fg to inhibit muonium (and ortho-positronium) form­ation in cyclohexane containing CCJl^ . Pre­liminary results indicate no anti-inhibition, as if muonium is not formed by combination of the thermalized muon with an end-of-track spur electron (the spur model).(7) Unsuccessful attempts were made to observe muonium in liquid methane and its solutions, at ~100 K using 'surface muons'. There were too many problems arising from the cryostat caused mainly by its bulkiness and unreliability. Further efforts will be made in this direction, however, since CH^ is an46ideal solvent in which to test important as­pects of muonium dynamics.Experiment 160 Studies o f some ternary magnetic superconductors with muonsWith the short separator on the M20 beam line and surface muons measurements were carried out on the ternary superconductors SmRh^B^ and YRh^B^, mostly using the zero field tech­nique to study the relaxation of the muon signal as a function of temperature (Eagle apparatus, Janis cryostat). The striking change in the relaxation at 0.87 K transition temperature from the superconducting to the superconducting-antiferromagnetic coexistence state) reported last year has been confirmed for SmRh^B^ (Fig. 58). The relaxation rate in the temperature range ~ 0 . 9 K < T < 5 K  has been found to decrease with increasing temp­erature with a small change around T = 2.7 K of transition to the normal state. The asymmetry decreases with increasing tempera­ture (Fig. 59). At temperature over 20 K theSmRh4 B4 Z F - ^ S R  0 . 4 8 K  S 2.6KTIME ( m i c r o s e c )Fig. 58. Relaxation signal for two tempera­tures above and below Tjj.T ( K )Fig. 59. Critical behaviour of the relaxa­tion in SmRh^B^.0 .8 bv> 0 .8tlJ 0 .7 5I—< 0 .7cr0 .6 5X< 0 . 6- JUJ 0 .5 5LL/< 0 - 50 .4 5TIME ( microsec )Fig. 60. Change in relaxation function from low to high temperature.relaxation function changes to a Gaussian Kubo-Toyabe shape (Fig. 60), as is the case when the relaxation is due to dipolar inter­action with the nuclei in the host lattice. Thus the picture emerging is that, below about 3 K where the material displays the interesting interplay and coexistence of superconductivity (electron pairs, coherence length) with magnetic ordering (antiferromag­netic, exchange fields, fluctuations, etc.), the muons probe directly the dynamics of the rare-earth spin system. Further evidence that this is the case is provided by the YRh^B^ measurements. This material is super­conducting below ~10 K but not magnetic since the rare-earth ions have been replaced. In this case a Kubo-Toyabe function has been found at all temperatures. The shape of the relaxation function for SmRh^^ at the higher temperatures is practically indistinguishable from that of YRh^B^ at the measured tempera­tures (6 to 30 K). This relaxation is undoubtedly due to the nuclear spins.Partial results for these experiments were reported at the March meeting of the APS (Solid State). Considerable interest has arisen among theorists engaged in trying to develop a microscopic understanding of the properties of the ternary superconductors, as ySR is practically the only probe reacting directly to the dynamics of the rare-earth spin system, which in turn is the dominant factor in the magnetic behaviour of those materials.Experiment 161 Amorphous spin glassesAs remarked last year, the amorphous spin glass Pd(75)Fe(5)Si(20) exhibits a sharp change in the slope of the internal field vs. temperature dependence, in contrast to the smooth behaviour found for the crystalline spin glasses. Unfortunately this study has come to a standstill, with no beam time available to it during 1982. A broad class of spin glasses will be investigated in the future, as the longitudinal (including zero) field technique of pSR with surface muons has proved capable of furnishing unique experi­mental information on such materials for which the theoretical understanding is still at a very primitive stage.Experiment 191 Muons and muonium on surfacesRuns of this experiment were performed on both the M9 and M20 secondary channels. The M20 surface muon beam in combination with the short dc separator proved to be ideally suited for studying the interaction of muons and muonium with catalytic surfaces. During 1982 research has continued on finely divided samples of Si02 and Pt (unsupported cata­lysts) with the following results.s i o 2A simple nonequilibrium model has been developed to explain the temperature depend­ence of the transverse field muonium relaxa­tion rate (% u) in silica powder (70 A mean diameter), prepared at 120°C in vacuum to remove moisture, shown in last year's annual report. In essence, this "three-state" model assumes two absorbed states (host and trap sites) and a desorbed state for muonium, and describes the surface diffusion, trapping and desorption of muonium from the silica surface. From the model one can extract the binding energies for the adsorbed states, activation energies for hopping between sites, trap concentrations and other intrinsic properties of the surface. A fit of this model to the data taken in 1981 is shown in Fig. 61.To study the effect of surface hydroxyl groups on the muonium behaviour, two samples were prepared in vacuum at 420°C and 600°C, which is expected to remove 50% and 70% of the hydroxyl groups, respectively. In com­parison with the sample prepared at 120°C,47h-<K)Fig. 61. Muonium relaxation rate Xj^ u as a function of temperature for Si02 powder.transverse field measurements of the muonium relaxation rate as a function of temperature for these two samples show a dramatic decrease in the muonium relaxation rate below about 18 K. The results of these experiments indicate a strong dependence of the muonium relaxation rate on the surface concentration of hydroxyl groups at low temperatures and are in basic agreement with the three-state model described above. A detailed description of these and the results described below is in preparation for publication. In addition,BET studies (i.e., gas absorption isotherms) were carried out on the sample baked at 120°C (moisture removed) and the sample baked at 600°C (hydroxyl groups removed) using ultra- pure ‘Hie. The functional dependence of the transverse field muonium relaxation rate on percentage surface coverage is markedly different for the two samples. Also, the transverse field relaxation rate for muonium was measured as a function of temperature in the SiC>2 sample baked in vacuum at 120°C with a 10% monolayer of argon. The data for these two experiments is currently being analysed and thus no quantitative conclusions can be given at this time.The transverse field relaxation versus temp­erature and surface coverage for samples prepared under varied but controlled condi­tions provide useful information to help characterize the muonium site and dynamics on the surface. Additional information on the actual interactions responsible for the muon and muonium depolarization can be obtained by means of zero and longitudinal field p+SR studies. So far, longitudinal field measure­ments have been made on an Si02 sample bake in vacuum at 120°C. Results show that at5.7 K the muonium anisotropy is completely restored by a field of only 2 Oe. In the three-state model the muonium atoms are "frozen" in the host adsorption sites at this temperature. The complete quenching of the muonium relaxation at such a low field sug­gests that the relaxation at the host sites is mainly due to nuclear dipole moments, presumably from the hydroxyl protons, or from random hyperfine anisotropy. At this stage it is impossible to decide which of these two mechanisms is predominant; however, prelimi­nary results on hydroxyl group dependence of the relaxation function suggests further that the surface hydroxyl groups certainly play an important role in the low temperature trapping and relaxation at the host sites.At 25 K a two-component relaxation is observed; the fast component can be quenched with a 2 Oe longitudinal field, again indi­cating nuclear dipole interaction or random hyperfine anisotropy, while a slower relaxa­tion component remains unaffected by applied fields up to 40 Oe. This contribution to the muonium relaxation must be due to either superhyperfine interactions or spin exchange. To properly assess the nature of the inter­action (and its strength) responsible for this component, new equipment is required which provides larger longitudinal fields.PtLast year p+SR in transverse field (TF-y+SR) was used to study the p+ relaxation rate as a function of temperature and surface coverage, in this case hydrogen atoms, in a sample of platinum microcrystals (~100 A mean diameter). Early in 1982 evidence was obtained that indeed most of the muons reside on the Pt microcrystal surfaces. A sample covered with several layers of frozen air showed a large decrease in the muon asymmetry below ~55 K, a clear sign of muonium formation at the surface. We have since performed new measurements on a sample of 100 A platinum microcrystals to study the temperature depen­dence of the muon relaxation rate and asymmetry both before and after hydrogen chemisorption. In both cases a reduction in the muon asymmetry was observed at low temperatures. These results will be compared with NMR experiments on similar samples.Note that muonium formation has never been directly observed in the Pt samples. How­ever, a direct observation would be possible with sufficiently large longitudinal field.48THEORETICAL PROGRAMIntroductionDuring the past year both the size of the theory group at TRIUMF and the diversity of its interests have increased considerably.The research activities of group members cover a variety of topics in nuclear and par­ticle physics. Much of the research program is directly related to the TRIUMF experimen­tal program. In addition to their research activities the theorists are also involved in a number of other laboratory activities.The four permanent staff members of the group are H.W. Fearing, B.K. Jennings (from August)A.W. Thomas (in leave from April) and R.M. Woloshyn. J.N. Ng holds an NSERC University Research Fellowship. Research associates, some of whom are supported through NSERC grants, are B. Blankleider (to November),C.Y. Cheung (from September), R.G. Ellis,G. Fogleman (from September), P.A. Kalyniak (from September), O.V. Maxwell (from October)A.S. Rosenthal (to August), 0. Shanker (to September), L. Tiator (from October) and R.E. Turner (from October). Long-term visitors to the theory group are R. Barrett, N. de Takacsy, B. Keister, Q. Li and E. Veit.Several members of the theory group taught courses at UBC and supervised graduate stud­ents. Students completing their Ph.D.'s during the year were J. Johnstone, P.A. Kalyniak and S. Th^berge. Current graduate students are R. Workman and P. Zakarauskas.Members of the theory group have been involved with the Experiments Evaluation Committee, the Long Range Planning Committee and the Kaon Factory Steering Committee. Organization of the regular TRIUMF seminar series has also been handled by the theory group. This and the summer theoretical visitor program has brought a large number of visiting theorists to TRIUMF including0. Sparrow1. TalmiF. TabakinV. Vento P. Vogel R. WeinerC.W. Wong S. WongI. Afnan R. Arndt L. Arnellos S. Barr A. BarrosoA. Bielajew M. Bolsterli L.S. BrownB. Campbell L.M. Chang M. Chanowitz S. CoonJ. EisenbergV. EliasE.D. Cooper A. Fonseca T.J. Goldman J.M. Greben A. HacinliyanF.C. Khanna L. KokR. Koniuk T.K. Kuo H.C. Lee K .F . Liu L. LudekingV. Mandelzweig Th. MarisB. McKellarH. McManus M. Moravcsik P. Mulders M. Rho G. G . Ro s s P.N. ScharbachB. SchwesingerE. Siciliano R. Seki M. SoyeurSpecific research activities undertaken dur­ing the past year are outlined below. Some of this work has been done in collaboration with theorists at other institutions, not all of whom are mentioned.Meson-nucleus interactionsPion-nucleus scatteringThere is a longstanding argument in low-ener­gy pion-nucleus scattering over the nature and role of the multiple scattering terms in the multiple scattering expansion, the catch words being Lorentz-Lorenz effect and rho- meson. It has been argued [Brown et al., Phys. Reports _50, 227 (1979)] that the Lorentz-Lorenz effect and the rho-meson act to greatly reduce the multiple scattering. A recent inelastic pion-scattering experiment [Amann et al., Phys. Rev. C _23^  1635 (1981)] on 12C may cast new light on this subiect.In particular the scattering to the 0 7.65 MeV state shows a strong disagreement between DWIA calculations and the experimen­tal data at more forward angles. The experi­mental data have a minimum at forward angles while the calculation has a peak. A plane wave impulse approximation would, like the experiment, have a minimum at forward angles since the cross section in this approximation goes like the momentum transfer squared.Thus by going to a better theory and putting in the distortions due to multiple scattering we get a worse result. If the multiple scat­tering were suppressed, for example by the effects mentioned above, we would again get agreement with the experiment. We are cur­rently investigating this case further.Kaon-induced deuteron disintegrationThe likelihood that high quality kaon beams will become available in the near future, possibly at TRIUMF, has accelerated theoreti­cal interest in K-nucleon and K-nuclear physics in recent years. One of the simplest K-nuclear reactions, however, the exclusive reactionK~d -»• l“pAn (1)with a two-body final state, has received very little attention to date, either49theoretically or experimentally. The similarity of (1) to the very well-studied reactionTr~d -*-»■ pp (2)suggests that simple models that have achieved semi-quantitative success in the latter reac­tion could be adapted to describe reaction (1) as well. Both reactions are governed by the same kinematics, which demand a large momen­tum transfer between the two baryons in order to conserve both energy and momentum, and which necessitate the inclusion of rescatter­ing terms in the reaction mechanism.We have initiated a study of reaction (1) based upon a model for reaction (2) original­ly proposed by Brack et_ al^ . [Nucl. Phys.A287, A25 (1977); see also Maxwell et al., Nucl. Phys. A3A8, 388 (1980) and Chai and Riska, Nucl. Phys. A388, 3A9 (1980)]. The kaon reaction is complicated by the richness of the A and E resonance spectrum just above and below threshold [there are 9 resonances lying within 350 MeV of threshold (above and below) in reaction (1) compared with only one in the pion reaction] and by the much greater multiplicity of meson exchanges that can con­tribute to the two-body absorption terms [K exchange, K* exchange and isoscalar meson exchanges, as well as isovector meson exchanges, are possible in reaction (1), de­pending upon the final state]. The kaon reaction is further complicated by the strong coupling between the XTp and An channels, which may necessitate a coupled channel treatment of the final state. In view of these complications, the following strategy has been adopted. Initially, only the im­pulse approximation and rescattering through the two lowest-lying resonances, the £(1385) and the A(1A05), are included in the reaction mechanism. To simplify the calculations, we also neglect the 57p +-*■ An coupling and con­fine ourselves to the 57p final state. The effect of higher-lying resonances can then be studied by including them in the reaction mechanism one by one with coupling constants adjusted to reproduce the observed widths and branching ratios (where known) and with form factor masses introduced as parameters. At a later stage the effect of final-state correlations will be examined.With just the two lowest-lying resonances included in the two-body absorption term, by far the largest contribution to the cross section arises from rescattering through the A(1A05) followed by one-pion exchange.Neither the impulse approximation term, which is suppressed both kinematically and by virtue of the weakness of the ENK coupling, nor rescattering through the £(1385), which lies almost 50 MeV below threshold and has a width of only 17 MeV, has a significant effect on the cross section. Inclusion of additional meson exchanges following the A(1A05) excitation alters the one-pion- exchange result by less than 10% over the full range of energies considered. Since the A(1A05), as well as the £(1385), lies below threshold, the calculated cross section is essentially structureless, decreasing mono- tonically as a function of energy. This will change, of course, once the higher-lying resonances above threshold are included.A momentum space analysis o f pion photoproduction from nucleiPion photoproduction from nuclei involves three major problems in nuclear physics, namely the nuclear structure, the pion- nucleus scattering and the off-shell effects of the photoproduction of pions from bound nucleons. And in comparison with elastic electron scattering or with pion-nucleus scattering, it provides additional informa­tion. In the past the momentum dependence of the production operator has never been taken fully into account. Since this production operator is given only in momentum space it is natural to perform the calculation in momentum space. In the framework of a dis­torted wave impulse approximation we are now able to treat the Fermi motion effects of the nucleons as well as the local pion momentum dependence in the production operator exactly. We have studied 12C( y, tt+) 12B as a typical photopion reaction and compared our calcula­tion with existing data at low pion energy. While there is only a small effect at low energy we find quite a big discrepancy between a local co-ordinate space and our momentum space calculation at high energies, especially in the vicinity of the A(1232) resonance.Few-nucleon systemsRelativistic description o f the two-nucleon systemWe have studied the role of the relative energy variable in a model deuteron composed of scalar nucleons exchanging scalar mesons. The Bethe-Salpeter equation (BSEQ) was solved50for three different configurations of binding energy and meson exchange, and the resulting bound-state wave functions compared to standard three-dimensional reduced equations, in which the relative energy degree of free­dom has been eliminated. For all three con­figurations the solutions of the reduced equations reproduce the BSEQ relative three- momentum dependence quite well. Furthermore, the reduced solutions can be iterated in a simple scheme to reproduce most of the BSEQ relative energy behaviour as well.A related project was a study of the elec- tron-deuteron charge form factor at very large momentum transfer, using a similar scalar model of nucleons and mesons. The goal was to establish consistency criteria for calculations which are based upon a nucleon-meson field theory. It was found that a momentum loop integral with the spec­tator nucleon on the mass shell has the same leading behaviour at large momentum transfer as a four-dimensional integral with Bethe- Salpeter solutions. However, not all three- dimensional approaches yield this behaviour.The results of these studies suggest that two-nucleon reactions at lower energies are also dominated by configurations in which an intermediate nucleon is on shell. This idea is currently being tested for some simple models, appropriate for pp •* diT+  and NN + NA.Charge symmetry and the reaction d + d - *  4He+n°Although it is known that nuclear charge independence is broken, the violation of nuclear charge symmetry has not been firmly established [Henley and Miller, in Mesons in Nuclei, Vol. I (North-Holland, Amsterdam, 1979)]. The reaction d+d ■+■ 1+He+ TT0 is forbid­den by charge symmetry because it requires a change of the total isospin of the system by one unit. Consequently, this reaction pro­vides a sensitive test of charge symmetry in nuclear interactions.The reaction mechanisms of d+d ■*■ ^He+ir0 have been examined in the A(3,3) energy region.We consider the following sources of charge symmetry breaking: (a) Direct electromagnetic interaction, (b) p°-m mixing, (c) n-tr° and n'-Tr° mixings and (d) n-p mass difference.The forward angle differential cross section is calculated to be in the range of 0.01 pb/sr to 0.1 pb/sr.Meson exchange three-nucleon potentialsTo date, all calculations of the binding and saturation density of nuclear matter using two-nucleon potentials which fit the scatter­ing data and deuteron properties fall on the Coester band. Consequently it is very interesting to study the effects of three- nucleon potentials (3NP's). An investigation is in progress to develop p-ir and p-p exchange 3NP's [Coon e£ j+L.] using the analog of the PCAC and current algebra analysis of Coon et al. [Nucl. Phys. A317, 242 (1979)] for the it- it exchange 3NP. In the ir-p analysis PCAC, current algebra, CVC and vector dominance are used to obtain a low- energy extrapolation for the off-mass-shell pN-HtN amplitude which generates the p-ir ex­change 3NP. To first order the p-ir amplitude is uniquely determined (in fact it is the p analog of the Kroll-Ruderman theorem). The A(1230) contributions are found to be impor­tant in both ir-p and p-p exchange 3NP contri­butions to nuclear matter. Preliminary results indicate that the nuclear matter binding energy contributions from the tt— tt and p-ir exchange 3NP are of similar magnitude but opposite sign resulting in a significant cancellation. The p— it and p-p exchange 3NP are therefore of considerable interest.Soft photon calculations o f np —  dyThere has recently been renewed interest in the np * dY reaction at TRIUMF, and a new ex­periment is now under way [Expt. 190]. In view of the similarity between np -» dy and nucleon-nucleon bremsstrahlung (ppy) it seems worth while to re-examine the np dy process in terms of the same kind of soft photon approximation (SPA) used for ppy [Fearing, Phys. Rev. C 22, 1388 (1980)] and to make the same kind of comparisons with potential models as has been done for ppy. One simple form of SPA was recently applied to np dy by Govaerts et_ £+L. [Nucl. Phys. A368, 409(1981)] with rather encouraging results.One of the first observations one makes is that the np ->■ dy differs from p py  in that there is no "elastic" process. Thus here the SPA relates the radiative process to the np + d vertex function at an unphysical point, rather than, as in ppy,  to a directly measurable physical process. The vertex function must be evaluated by extrapolation, for example from low energy np scattering, but once such extrapolation is done, one can apply the SPA just as for ppy .  Our calcula­tion is thus developed in exact parallel with51the ppY calculations• It differs from Govaerts et al. in that we have kept all of the SPA terms in the cross section, rather than just the leading ones.The results of this approach in the forward direction are quite encouraging. Recall that the forward differential cross section as a function of energy has been a puzzle for some time since potential models do not fit the data and since many attempts to resolve the problem by including a variety of corrections such as exchange currents, D-state contribu­tions, etc. have not been very successful.The SPA calculation, however, does qualita­tively fit the data over the energy range of about 30-130 MeV, and the additional terms we have kept give a somewhat better fit than that obtained by Govaerts et al. For the angular distributions the extra terms included are quite significant. They amount to essentially a constant factor across the full angular range. They thus remove the un­physical zero in the differential cross section at 0° and 180° and make the results look more like those obtained in potential models. The results are then in rough quali­tative agreement with the data. As a next step, the dueteron D-state was included.This gives sensible results for the leading terms of the SPA but so dominates the next terms that one must probably conclude that there are significant D-state contributions and cancellations from even higher terms which cannot be calculated in SPA.Nucleon-nucleon bremsstrahlungProton-proton bremsstrahlung (ppY) has been of interest both experimentally and theoret­ically at TRIUMF for some time. There has been one experiment [Rogers et al., Phys.Rev. C 2_2, 2512 (1980)] and calculations under a variety of conditions in soft photon approximation [e.g. Fearing, Phys. Rev. C 22, 1388 (1980)]. A proposal for a new experi­ment [Kitching, Expt. 208] which would measure the analysing power for the first time is now under consideration and this has stimulated further theoretical work in ppY*During the past year theoretical efforts have been directed toward two separate approaches. First, some further work has been done on a relativistic gauge invariant model of ppY which was described in the previous annual report, work aimed at trying to solve the uniqueness problem. Second, we have started to develop a modern potential model code for ppY* The potential approach is relativelystandard, but there have been no recent cal­culations and none at all using any of the modern potentials, such as the Paris poten­tial. A good start has been made on a calcu­lation which will use the Paris potential, and perhaps other modern potentials, and which will include a variety of effects, e.g. relativistic spin correction, in a systematic way. The intention then is to achieve a potential model calculation significantly more realistic than those in existence so that comparison with new data will provide a real test of the potential approach, one which is not made ambiguous by approximations to the model.Amplitude analysis o f the kNN systemOne of the most elementary and fundamental problems in intermediate energy physics is the description of the ttNN system and its coupling to the NN channel. The small number of (traditional!) particles involved facili­tates microscopic theoretical descriptions. Indeed the most sophisticated of these, the so-called unitary approaches, include in their description pion and nucleon rescatter­ings to all orders, heavy meson exchanges, explicit dressings of nucleon propagators and ttNN vertices, 3-body unitarity, large numbers of partial waves, and relativistic effects. Nevertheless there remain large discrepancies between theory and experiment especially in various polarization observables.To help isolate the origin of these discrep­ancies we have proposed to investigate the explicit contribution of partial wave ampli­tudes to each of the observables in the ttNN system. This program is different from the usual phase-shift analysis in that one is more able to input theoretical and experimen­tal prejudices regarding the importance of certain partial wave amplitudes. For example we have found that the assumption of a domi­nant J11 = 2+ amplitude leads to otherwise model-independent tensor polarizations in pp ->■ ctt. Again the same assumption leads to the conclusion that it11 in pp ■* cfn is high­ly dependent on the = 0+ amplitude. This type of amplitude analysis is currently in progress for the reactions pp <fir, TTcf ■+ ncf and pp ^ pp.52Nuclear reactions Relativistic heavy ion collisionsThe collision of heavy ions has been, and still is, a much studied subset of nuclear reactions. It is only recently that terrestri­al accelerators have been made available for the study of relativistic collisions. One successful approach to describing these data is through thermal or phase space models. As a good first approximation one can say that the results of heavy ion collisions are determined by the available phase space. One place the phase space models fail is in the predicting of the pion production cross sec­tion. The predicted cross section is a factor of two too high. The pion production cross section is rather sensitive to the temperature or equivalently the available energy. The most obvious way to lower the temperature is to tie up some of the energy in collective flow. This has led us to develop a simple model which incorporates a collective radial flow. This model fits the pion total production cross section while preserving the good fit to other data such as the inclusive cross section. We would claim this is the best evidence of collective flow to date.As mentioned previously the results of rela­tivistic collisions are determined largely by phase space. However, phase space calcula­tions are non-trivial for interacting systems. One approach we have used is the virial expansion. This approach permits one to correctly include the finite width of the delta resonance through pion-nucleon phase shifts and avoid philosophic arguments about whether the delta is a particle or resonance.The use of the virial expansion also allowed us to study the cancellation between con­tinuum and bound-state contributions to the phase space of interacting nucleons. By comparisons with more exact calculations we could show [Jennings et_ al., Phys. Rev. C 25, 278 (1972)] that in the energy range of interest it was reasonable to treat the deuteron as a particle and ignore the other effects of the nucleon-nucleon phase shifts.Effective polarization in quasi-free scatteringThere is a simple prediction which one can make for good shell model nuclei like 160 or ^Ca, namely, that the average effective polarization of the protons in two sub­shells, split by the spin orbit coupling,should vanish to a good approximation. Exper­imental results [Kitching et^  al., Nucl. Phys. A340, 423 (1980)] show that the effective polarization obeys the theoretical prediction only if the polarization p(9), characteristic of the free scattering, is reduced in the nuclear environment. We have used the OBE model to investigate the effect of the nucleus on p(0).Coupled channel analysis o f deuteron scattering using the adiabatic approximationWe use an alternative approach to that of Amakawa e£ al. [Phys. Lett. 82B, 13 (1979)] to generalize the Johnson-Soper calculation of the contribution of unbound n-p states to deuteron elastic scattering. In the Amakawa calculation the relative n-p states are ex­panded in orbital angular momentum and a cut­off is made after 1=2. In the present approach the scattering problem is solved in the body-fixed frame of the n-p system and this removes the cut-off in angular momentum.Electromagnetic interactionsOn the validity o f the virtual photon conceptExclusive photonuclear reactions like pion photoproduction or photodisintegration are very powerful in testing the nuclear struc­ture at intermediate energies. However, since there are no continuous wave electron accelerators in this energy range available which allow use of a monochromatic photon beam, the experiments have been performed using either bremsstrahlung or virtual photon concept. Since the bremsstrahlung spectrum is quite uncertain near the end point many experiments were done with virtual photons and analysed by using the Dalitz-Yennie virtual photon spectrum. This spectrum, however, assumes an infinitely massive target and recent experiments on light nuclei found significant deviations in their analysis. So the aim of this work was first to study whether or not the concept of virtual photons works and if so to derive an improved formula which takes recoil effects into account. We found that this concept works extremely well in pion photoproduction on light nuclei even 50 MeV from the end point [Tiator and Wright, Nucl. Phys. A379, 407 (1982)]. In electro­disintegration of the deuteron, however, we found that this is only true for certain kinematical domains. Figure 62 shows an angular distribution for d(e,p)e'n at 125 MeV electron energy about 25 MeV from the end530 PFig. 62. Electrodisintegration cross section in the lab as a function of proton lab angle 9p. The full line is the complete (e,p) cross section, while the dashed and dashed- dotted lines are obtained with our new and the Dalitz-Yennie virtual photon spectra, respectively.point. The full line is an exact calculation while the dash-dotted and dashed lines are obtained with our new virtual photon spectrum and the Dalitz-Yennie spectrum, respectively. Even though there is a very good agreement with our new formula at backward angles, the concept breaks down for forward angles, unless one stays within about 5 MeV from the end point [Wright and Tiator, Phys. Rev. C 26, 2348 (1982)] .(y,p) reactions at intermediate energiesThe study of photonuclear reactions is a way of understanding nuclear structure. Since the electromagnetic interaction is weak and in principle well understood, we may there­fore concentrate on questions of nuclear structure and reaction mechanisms.The reaction 160(y,p)15N for photon energies 50-350 MeV has been studied by Londergan and Nixon [Phys. Rev. C 19_, 998 (1979)] and Gari and Hebach [Phys. Rep. 72, 1 (1981)].Londergan and Nixon found that for Ey >100 MeV, isobar photoproduction mechanism provides a very large contribution to the reaction cross section. However, Gari and Hebach reached different conclusions; they found that the "exchange current" contribu­tion is very important, and that the isobar excitation contribution is important only when "shell-model" and "exchange current" amplitudes interfere destructively.The main objective of this study is to try to clarify the importance of the A-contribution to (Y>p) reactions. Final-state interactions, which are not treated quite properly by Londergan and Nixon, will be taken care of through distortion by an optical potential. This work is still in progress.Electroproduction o f off-mass-shell pionsThe PCAC hypothesis and current algebra Ward identities have been used successfully in the past to develop an off-shell expansion for ttN scattering [Scadron, Proc. VII Int. Conf. on the Few Body Problem, Delhi, 1976]. Follow­ing this success it is of interest to apply the same techniques to electroproduction of off-mass-shell pions. Such analyses have been made by Weisberger [Brandeis Lectures 1970], Dombey and Reid [Nucl. Phys. B60, 65 (1973)] and recently by MacMullen and Scadron [Phys. Rev. D 20, 1069 (1979)]. In the latter analysis a modified pion pole Born term was used which explicitly satisfies the Ward identity on the electroproduction- ampli­tude. We have shown [Ellis and McKellar] that an amplitude satisfying the Ward identi­ty can be constructed starting from the usual Born terms which do not satisfy the Ward identity and that this same amplitude will be obtained from a large class of input Born terms, one of which is the MacMullen and Scadron pole term. Consequently the final result of MacMullen and Scadron does not depend on the choice of Born term and we en­courage its use to develop the electroproduc­tion analog of the PCAC off-shell expansion for ttN scattering.Polarized electron-polarized nucleus scatteringDue to the lack of free neutron targets, mea­surement of neutron electromagnetic form factors, particularly the neutron electric form factor (Gg^ j), is quite complicated. In­formation extracted from e-d elastic scatter­ing data involves large uncertainties - caused by the high momentum component of the deuteron wave function [Galster £t^  a l_., Nucl. Phys. A314, 253 (1979)].In this study we calculate the spin asymme­try54A = da(t) - da(t) d a( +) + d a( J)for the inclusive and exclusive reactions cf(e,e')X and ct(e,e'n)p. Preliminary results indicate that the asymmetry crosses zero at a certain electron scattering angle 0O and that 90 changes with Gg^. This is very desirable because a null point can be measured experimentally with high accuracy. With quasi-free kinematics, deuteron high momentum components, exchange current effects, and final state distortions are not important [Fabian and Arenhovel, Nucl. Phys. A314, 253 (2979); Arenhovel, Nucl. Phys.A384, 187 (1982); Dunning Phys. Rev.141, 1286 (1966)]. Therefore Gg^ can be extracted with fewer uncertainties. In par­ticular, we note that for the exclusive reaction, with the detected neutron momentum equal that of the electron momentum transfer, the dueteron D-wave component does not contribute, and off-mass-shell effects are minimal. In this situation the deuteron essentially provides a free neutron target.We are also investigating polarized quasi- free scattering of electrons from 3He. In this case the asymmetry A is expected to be especially sensitive to the properties of the neutron as the two protons are mostly in opposite spin states. Here too considera­tions of e-n scattering lead us to expect that the asymmetry will change sign for certain geometries of the experiment, thus providing a new way of measuring Ggjg- Two further observations about this reaction may be made. Firstly, the unpolarized cross section depends only on the square of electromagnetic form factors. For the polarized case there are additional cross terms between electric and magnetic form factors thus giving extra phase information inaccessible with unpola­rized scattering. Secondly, this reaction may provide new information about the three- body wave function as it probes both the momentum and spin distributions of nucleons in 3He.pd 3 Hey in a distorted wave impulse approximation modelThe process pd -> 3Hey has attracted recent interest, both because of new experiments aimed at resolving some of the current dis­crepancies in the data and because of its close connection with the analogous (p,ir) reaction, pd tir, and the hope that the comparison of the two reactions would lead to additional insight. A calculation of thisprocess, mentioned in last year's report, is now substantially complete. The model used is a generalization of the type of distorted wave impulse approximation used earlier for pd -*■ tir [Fearing, Phys. Rev. C 16, 313 (1977)]. It is based on the pn dy cross section as input, modified by a form factor coming essentially from the Fourier transform with respect to momentum transfer of a prod­uct of wave functions and a p-d distortion factor.The results in this model have been compared with the new TRIUMF data [Abegg et al., TRI­PP-82-18; Fearing, in progress]. The agree­ment is remarkably good over most of the energy range, 200-500 MeV, which was measured. Thus, for example, both angular distributions and normalization are repro­duced almost exactly at 350 MeV and the angular distribution is correct, but normali­zation slightly low at 500 MeV. More inter­esting is the one energy, 200 MeV, where the data show a qualitative effect which is not given by the theory, namely a dip in the forward direction. This dip at 0° was seen in the TRIUMF data and in an earlier experi­ment Frascaria et_ al. [Proc. 9th Int. Conf. on the Few Body Problem, Eugene 1980, vol. 1, p.39]. It is not given by the theory, which however does reproduce the angular distribu­tion for 9y > 45°.A somewhat similar theory by Prats [Phys.Lett. 88B, 23 (1979)], when extended to 200 MeV, which is probably near the upper limit of its validity, does seem to give this forward dip. It differs from the present theory in that it includes explicitly dia­grams corresponding to direct radiation from the proton and deuteron as well as the same triangle diagram used here. As can be seen from Fig. 63, it is the interference between the proton radiating diagram and the triangle diagram that gives the forward dip. However, in the context of the phenomenological model of the triangle diagram as used in both cal­culations, a portion of the proton radiating diagram is included already in the triangle diagram since that diagram is evaluated directly from the pn > dy and this cross sec­tion includes some contribution of a direct proton radiation diagram. Thus to include both diagrams as done by Prats involves some double counting. How much is not clear as there are selection rules and different ap­proximations operating in the two cases. Thus these phenomenological models have simply suggested a possible explanation for the for­ward dip; to actually resolve the question a more microscopic calculation will be required.55Fig. 63. Comparison of the pd ->■ 3Hey cross section at 200 MeV calculated in DWIA with contributions of the individual diagrams in­cluded in a similar calculation of Prats. Prats' total contribution is made up of the square of the triangle diagram (A2), of the proton radiating diagram (l2) and of their interference (1-A). Deuteron radiating pieces are small and have not been drawn, but are included in the total.Quark models and QCDHybrid quark model o f A nonmesonic decay in nucleiThe free decay of the A-hyperon is mainly weak mesonic. However, when it is bound in a complex nucleus, the A decays predominantly via the nonmesonic mode, AN NN [Adams,Phys. Rev. 156, 1611 (1967)]. Knowledge of this nonmesonic process is not only necessary for the understanding of the A-hypernuclear lifetime, but also provides important infor­mation about A-N interactions.We have estimated the lifetime of a A-particle in nuclei. The long-range part of the A-N interaction is assumed to be mediated by one- pion exchange. For the short distance part (r < 0.8 fm), we describe the A-N cluster by configuration of six quarks; and the transi­tion AN -*■ NN occurs as a result of w-boson exchange between two quarks. The distortionsof the outgoing nucleons are included in an eikonal approximation. We find that the 6- quark pair dominates the nonmesonic decay, and the nonmesonic lifetime ® 1/3 x^ree.Gluonic mass spectrum in the Abelian bag modelIn the Hagedorn bootstrap model [Hagedorn, Nuovo Cimento Suppl. 147 (1965)] thedensity of hadronic states increases exponen­tially with energyp(E) ~ exp(E/T0) .A similar expression has been obtained in the Abelian bag model [Kapusta, Phys. Rev. D 23, 2444 (1981)]. We were able to show, however, that important differences arise when one includes surface effects due to the finite size of the bag [Jennings and Bhaduri, Phys. Rev. D 26, 1750 (1982)]. The density of states then has the formp(E) ~ exp [m/T0 - a(m/T0) 1/3] ,where a depends on the shape taken for the bags but is of order unity. This modifica­tion has important consequences when the temperature approaches T 0 from below. The total energy, occupied volume, entropy, etc. remain finite regardless of the power of E out in front of the exponential. This will strongly affect the nature of any phase transition which may occur at T0.Quantum fluctuations in the bag and baryon observablesThe hadronic bag model provides a phenomeno­logical realization of two of the major prop­erties attributed to QCD, asymptotic freedom and confinement, and at the same time is roughly consistent with baryon spectra. Im­provements in the original model have been mainly concerned with the incorporation of a third property of QCD, its invariance under chiral transformations, and have led to the introduction of Goldstone fields in the model. Much less attention has been devoted to gluon-mediated processes within the bag, which induce quantum fluctuations in the quark fields there.In an attempt to address these questions, we have developed a time-dependent, perturbative formalism within the static, spherical cavity approximation to describe the effect of fluc­tuations of the quark fields on static obser­vables. This formalism differs from previous ones in that (1) all relevant contributions to second order in the QCD coupling constant56are generated systematically and included in the numerical treatment; (2) the intermediate state sums that occur in normal mode expan­sions of the quark and gluon propagators are carried out over a full set of states con­sistent with parity and SU(2) coupling rules. Two classes of diagrams occur in the treat­ment: two-body diagrams involving a gluon ex­change between two quarks and one-body vertex diagrams above the zero*-*1 order current insertion are modified by the emission and re­absorption of a gluon before and after the insertion. One-body quark self-energy diagrams have not been treated explicitly since these are presumably already accounted for through renormalization of the masses and fields appearing in the cavity Lagrangian.The one-body vertex terms exhibit ultraviolet divergences of the same type that occur in free space theories. After removing these divergences, we apply a finite renormaliza­tion such that the renormalized vector and axial vector quark-current couplings have unit strength within the bag where the chiral symmetry is realized in the Wigner mode [we assume that the external Goldstone fields do not penetrate the bag surface].Final results with this formalism have not yet been obtained; however, preliminary esti­mates for the nucleon observables indicate that the first-order quantum corrections are significant but much smaller than the zero*-*1 order results. This supports the concept of a hadronic bag as a bounded perturbative region within a non-perturbative vacuum. On the other hand, the magnitudes of the correc­tions obtained indicate that quantum effects alone are not sufficient to account for the existing discrepancies between the zero*-*1 order results for nucleon observables and the empirical ones.The KN interaction near thresholdThe SU3 generalization of the cloudy bag model gives a prediction of_the strength and momentum dependence of_the KN A(1405) and 7TZ A(1405) vertex. KN and ttT scattering have been investigated using the Lee model with non-relativistic and relativistic kine­matics and by solving the coupled Schrodinger equations. The latter give also a prediction of the K“p atomic bound state energy. The calculations are being compared with the KN scattering length and directly with the scattering data. Results indicate that the real part of the scattering length has the same sign as the imaginary part in agreement with kaonic atom measurements.Infrared behaviour o f QCDWe are studying the properties of the gluon propagator using the Schwinger-Dyson equation which, in some approximation, can be put into a closed form in non-Abelian gauge theories.So far most of our work has concentrated on the three-dimensional pure gauge theory. The main conclusion is that there are no massless solutions to the Schwinger-Dyson equation in this theory. This is in agreement with Cornwall [Phys. Rev. D 26, 1453 (1982)] but contrary to the claim of Gardner [Oxford University preprint 8/82] who found both massive and massless gluons. Using Mandelstam's version of the equation we esti­mate a minimum gluon mass of g2Nc/60ir which is much smaller than the value given by either Cornwall or Gardner.The difference between various approaches lies in the construction of the "longitudi­nal" three-gluon vertex function. The expression for this quantity is not unique.The implications of the arbitrariness in the longitudinal vertex are presently being studied.The quark-gluon plasma at high temperature and densityWe showed in a model calculation [TRIUMF pre­print TRI-PP-82-14] that there is a thermo­dynamic limit to the quark plasma phase. The basic assumption is that the interactions among quarks and gluons can be represented by an effective potential which varies inversely with the density. Requiring a self- consistent solution for the density almost automatically yields a critical temperature and density below which the plasma phase cannot exist.The critical behaviour is seen very clearly in an approximate equation for the number density which holds when the quarks are taken to be massless:- ic n 7  5/ T  n^ ~ e 1The behaviour of the right-hand side is plotted in Fig. 64 at high and low temperature. Below T = Tc only the trivial nj = 0 solution exists. At high temperature the system approaches an ideal gas in line with QCD expectations. The critical temperature was estimated to be between 200 and 300 MeV which agrees with other calculations.57n j ( f  m 3 )Fig. 64. Behaviour of the rhs of the equa­tion as a function of n-p.Theoretical chemistryMulti-trajectory theory o f inelastic collisionA systematic approximation scheme has been developed [Turner and Dahler, J. Phys. A., in press] for introducing multi-classical tra­jectories into the theory of inelastic colli­sion. This scheme is based upon the use of an interaction picture generated by the diagonal elements of the Hamiltonian in the internal state representation and the Weyl- Wigner phase space representation. In general, the translational and internal degrees of freedom are coupled through the interaction picture potential which is non­local in translational space. For each different pair of internal states this potential has a unique classical trajectory generated by the Hamiltonian which is the arithmetic mean of the two appropriate (in­ternal state) diagonal elements of the full system Hamiltonian. Localization of this potential in translational position space produces multi-trajectory eikonal theory. Finally, replacing the unique classical trajectories with fully parametrized trajec­tories gives a multi-trajectory version of the standard impact parameter approximation. Results for both atomic and molecular (adia­batic and diabatic) bases are presented.Classical path theory o f laser-induced chemiionizationMiller's [J. Chem. Phys. 52, 3563 (1970)] classical path theory of field-free chemi­ionization is extended to laser-assisted (LA) and laser-enhanced (LE) processes [Dahler e_t al., J. Phys. Chem. 86, 1065 (1982)]. Field- free chemiionization includes both Penning ionization,A + B -> A + B+ + e“ , and associative ionization,A + B ■* (AB)+ + e" ,written here in terms of atoms A and B and the diatonic (AB)+ molecule. The addition of a laser of some specified frequency can enhance an already occurring field-free chemiionization process (LA) which is ener­getically forbidden in the field-free regime. The heavy particle dynamical motion is treated classically while quantum mechanics enters only through its implicit involvement in the atomic interaction potentials and in the rates of the electronic transitions that occur, viz., photoexcitation, photoionization and autoionization.Weak interactions and grand unification Extensions o f the standard modelThe constraints set by different processes on extensions of the standard weak interaction model were studied [TRI-PP-82-8]. The models considered were those with extended Higgs representations, technicolour models, Pati- Salam type of grand unified models and supersymmetric models. These classes of models were constrained by the it + ev to tt -*■ pv branching ratio, by CP_violation in the K^3 decays and by the K°-K° mass mixing. Limits on muon number violation were also used to constrain the models. It was found that the tt^ 2 branching ratio was sensitive at a useful level not only to massive neutrinos, but also to the presence of leptoquarks or supersymmetric particles.Intermediate energy subgroups o f SO( 10) grand unificationS0(10) grand unification symmetry-breaking patterns which have SU(3) x SU(2) x U(l) x58U(l) as an intermediate energy subgroup were analysed. These models are characterized by four different energy scales. The highest scale, My, the unification scale, is where S0(10) breaks to either SU(5) x U(l) or to SU(4) x SU(2) x U(l). At a scale Mx the second group in the symmetry-breaking chain breaks to SU(3) x SU(2) x u ( l )  x U(l). The gauge theory based on SU(3) x SU(2) x U(l) x U(l) differs from the standard model based on SU(3) x SU(2) x 0(1) in that it has two massive neutral vector bosons instead of only one. The scale M' where SU(3) x SU(2) x U(l) x U(l) breaks to SU(3) x SU(2) x SU(1) is the intermediate scale which can, theoretically, be relatively low (compared to My). The lowest scale, Mw , is the Weinberg-Salam breaking scale which is about 100 GeV. Models such as this are interesting, because they do not have the usual energy "desert" between the scales of Mw and My.The experimental value of sin29w appropriate to this model is determined by fitting free parameters of the extended electroweak model based on SU(2) x U(l) x U(l) to neutral cur­rent experimental data. It was found that the extended electroweak model is consistent with the neutral current data as long as the intermediate energy scale M' is greater than 260 GeV.Renormalization group analysis of the S0(10) model with Higgs effects included show that either the predicted value of sin20w is too large compared to the experimental value or that the predicted lifetime of the proton is below present experimental upper limits or both. These results were shown for the case where the only Higgs used in the breakings at M' and at Mw are those necessary to give mass to the fermions.Thus the grand unified theory based on S0(10) with SU(3) x SU(2) x U(l) x U(1) as an inter­mediate energy symmetry group and with minimal Higgs is ruled out by presently available data and by limits on the proton lifetime. Existing experimental data forces the conclusion that the S0(10) grand unified model and the extended standard model based on SU(3) x SU(2) x U(l) x U(l) are mutually exclusive.Massive neutrinos in muon decayWe have set limits on the mixing of a massive neutrino into the muon family, iUyjJ2, for neutrino masses in the range 1-70 MeV/c2.Both the experimental e+ spectrum [Bryman et^al., TRIUMF preprints TRI-PP-82-42 and 43] of muon decay and the p Michel parameter [Particle Data Group, Phys. Lett. 111B, 58 (1982)] are used with our theoretical analy­sis [Kalyniak and Ng, Phys. Rev. D 25, 1305 (1982)] of muon decay to obtain |Up7T2 < 10-2 in this mass range. The current experimental limits are summarized in Fig. 65. For neutrino mass below 7 MeV/c2 our limit is better than that from TTyV decay [Abela et al., Phys. Lett. 105B, 263 (1981)] but it is much worse for the mass range 7-30 MeV/c2. We fill the gap in the limit on |UyjJ2 for the neutrino mass range 30-70 MeV/c , which is inaccessible to tt£2 and Ke2 [Hayano et al., Phys. Rev. Lett. A9_, 1305 (1982)] experiments. Limits obtained from an analysis of y- cap­ture in %e for neutrino masses from 40- 80 MeV/c2 are complementary to our results [Deutsch et al., Univ. Catholique de Louvain preprint, 1982]. If one billion muon decay events were available our limits would be improved by about an order of magnitude.This hypothetical case indicates the effect of improved statistics on our analysis.Arvjio '6 l 1-------------- 1---------------1---------------1-------------- 1— ►0  3 0  6 0  9 0  120 150m „  ( M e V /c 2 )Fig. 65. The current experimental limits on |Uyi|2 are shown. The solid curves give the limits from the two-body it+ and K+ decays as indicated. The dashed curve is our limit from the measurement of the Michel spectrum in ordinary muon decays. The dash-dot curve is the limit obtained by considering the un­certainty in the rho parameter of the Michel spectrum.59Symmetry-breaking patterns in SU(5) with nonminimal Higgs fieldsWe have analysed the symmetry-breaking pat­terns of an SU(5) grand unified theory with Higgs fields in an adjoint and a 45-dimen- sional representation and compared our results to the case of an adjoint and a fundamental (5) representation of Higgs [Magg and Shafi, Z. Phys. C4, 63 (1980)]. We have assumed hierarchical breaking. Our analysis yields constraints on the parameters of the Higgs potential for the various symmetry- breaking scenarios. We have obtained some modes of breaking which are different from that of the case with a Higgs 5 replacing the 45, but they give the wrong low-energy symmetry so are not of phenomenological inte­rest. The standard symmetry-breaking pattern for SU(5)SU(5) + SU(3)xSU(2)xSU(l) SU(3) xu( 1)is reproduced for one particular form of the eigenvalues of the Higgs 45. For the case of Coleman-Weinberg symmetry breaking, there is a unique solution for this choice of the 45- dimensional Higgs field eigenvalues. We find that the 45-dimensional Higgs field can be used in place of the fundamental representa­tion without inconsistency.General topics in theoretical physics Multiple scattering theoryIt has been known for a long time that the multiple-scattering problem can be expressed entirely in terms of on-shell constituent amplitudes, provided the scatterers can be enclosed by non-overlapping spheres. The conditions for this "on-shell theorem" have now been extended to include certain classes of close-packed geometries of non-spherical scatterers which are encountered in various classical and condensed matter problems. The practical solution for these extended geome­tries involves a procedure analogous to anal­ytic continuation, and as such, the ordering of certain partial wave sums (never at issue for non-overlapping spheres) becomes crucial for convergence of the solution.Quantum generalizations o f the classical phase spaceQuantum mechanics is generally displayed through operators acting in a Hilbert space. In contrast classical mechanics is displayedthrough functions on the classical phase space. In dealing with systems that are nearly classical it is often useful to recast quantum mechanics in a form similar to classi­cal mechanics. That is, we want to express quantum mechanical operators as functions of p and q where in the classical limit p and q are the canonical momentum and co-ordinates, respectively. The most common method of doing this is through the Weyl association [Weyl, Z. Phys. 46_, 1 (1927)]. This associa­tion is given byA(p,q) = Tr A(p,q)A ,where the A denote operators. The delta is given<x1 | A(p,q) |x"> =  q^ exp i(x-x") .AWhen A is the density matrix the correspond­ing function is also known as Wigner's func­tion. This association has found important uses in fields as widely separated as molec­ular scattering, heavy ion scattering (rela­tivistic and non-relativistic) and low-energy nuclear physics. When -ft is not small, the p,q space introduced through the Weyl associ­ation has a structure different from the classical phase space. It is invariant only under linear inhomogeneous transformations rather than the full set of canonical trans­formations .We have developed alternative associations which are invariant under different subsets of the canonical transformations. However, it appears impossible to find an association which is invariant under the full set of canonical transformations. Each of these alternative associations provides a different but equally good (or bad) quantum generaliza­tion of the classical phase space. This new freedom, i.e. the choice of association, will we hope lead to computational simplifications in actual problems.Time-dependent view o f eikonal cross sectionsEikonal theory of inelastic binary collisions is a semi-classical high-energy approximation which involves a straight line translational trajectory. As well the duration of the collision is assumed to be shorter than the time scale associated with the internal motion (of the isolated particles) . Thus the motion due to the internal state Hamiltonian is neglected. The objective of the present work has been twofold, namely, to deal with situa­tions in which the internal state motion60cannot be neglected and, secondly, to treat the translational motion in a more realistic manner.In the first instance, time-dependent solu­tions [Turner et al., Can. J. Phys. j>0, 1371(1982)] of the Zwanzig-Feshbach projection operator method have been used [Thirumalai and Turner, unpublished] to obtain eikonal cross sections involving time-ordered cosine and sine memory operators. Since eikonal theory is a high-energy approximation, a time-disordered perturbation approximation is considered which contains all orders of the collision potential with the first-order term being the Born approximation.Straight line trajectories appear as a common feature of eikonal approximations. However, distortions from linearity occur during a collision and are expected to play an impor­tant role. Thus it is desirable to build some distortion into the trajectories. One way of doing so [Turner, Phys. Rev. A26, 3155(1982)] is to introduce a single classi­cal reference trajectory associated with a reference Hamiltonian. This leads to dis­torted inelastic eikonal cross sections.In both the straight line and distorted eikonal approximations there is no feedback from the internal state motion to the trans­lational motion. Effects of the internal state motion on the translational motion can be introduced [Turner, Phys. Rev. A, in press] using multi-trajectory theory. In particular, for each pair of internal states the resulting eikonal potential has a unique classical trajectory which is generated by a Hamiltonian whose potential is the arithmetic mean of the appropriate diagonal elements of the collision potential.On time-dependent solutions of the projection operator methodThe projection operator method of Zwanzig and Feshbach is used to construct the time- dependent density operator associated with a binary scattering event [Turner e_t al., Can.J. Phys. 60^ , 1371 (1982)]. The formulae developed to describe this time dependence involves time-ordered cosine and sine projected evolution (memory) superoperators. Both Schro'dinger and interaction picture results are presented. The former is used to demonstrate the equivalence of the time- dependent solution of the von Neumann equa­tion and the more familiar, frequency-depend­ent Laplace transform solution. For two particular classes of projection super­operators projected density operators are61shown to be equivalent to projected wave functions. Except for these two special cases, no projected wave function analogs of projected density operators exist. Along with the decoupled motions approximation, projected interaction picture density operators are applied to inelastic scattering events. Simple illustrations are provided of how this formalism is related to previously established results for two-state processes, namely, the theory of resonant transfer events, the first order Magnus approximation and the Landau-Zener theory.High-energy physicsAssociated Higgs boson and heavy flavour production in p~p collidersWe have investigated the production of Higgs bosons and heavy quarks in high-energy pp collision via quark and antiquark annihila­tion. The cross sections are small and found to be around 1 pb at ~1 TeV centre-of-mass energies.Another mechanism for the production of Higgs bosons is via gluon-gluon fusion. Since the gluon "content" of the proton (antiproton) is non-negligible this mechanism is expected to lead to a larger production rate. Calcula­tion of this is currently under way.The final-state interactions between the two heavy flavoured quark-antiquark pairs can lead to the formation of quarkonium states.We have completed the calculation for the case of qc[ forming a bound state. Thisis found to be negligible due to the small Higgs quark-antiquark couplings and is further suppressed by the value of the wave function at the origin for the above state. Calculations are now in progress for other quarkonium states.Neutral Higgs boson decay to jetsWe have calculated the total rate for H° decay to a quark-antiquark pair including first- order QCD corrections. Also, we have ob­tained the rate of Higgs decay to two jets for jets of the Sterman-Weinberg type. Quark mass has been included in these calculations. The calculation will be extended to include frag­mentation to hadrons yielding, finally, multi­plicities of outgoing particles. This study is motivated by the possibility of Higgs production in e+e“ collisions at LEP and, consequently, the need for detailed analysis of experimentally meaningful processes.APPLIED P R O G R A M S  D IV IS IO NSeveral of the applied programs have benefit­ed greatly from the 500 MeV machine's better reliability during 1982. However, the long shutdowns continue to be a problem for the two commercial enterprises that utilize the particle beams at the TNF. Novatrack Ltd. has overcome this problem by taking its neutron activation analysis samples to facil­ities in Washington State during shutdowns and then analysing the samples in their laboratories at TRIUMF. AECL has to limit their line of 500 MeV radioisotope products to those with long half-lives.For the biomedical group this has been the first year of actual radiotherapy, made possible by the greater reliability, higher beam currents and the completion of the scanning patient couch. Stronger pion flux and shorter shutdowns are still desirable, but even with the present state of the art one may look forward to a proper evaluation of pion therapy within the next few years.The various targets for the five 70 MeV beam lines in the main cyclotron vault have made progress, to the point where full operation of this facility is anticipated for 1983.These include isotope production targets for 127Xe and 123I as well as radioisotope research targets. The TRIM program has been moved from beam line 4A to the 70 MeV beam line 2C.The 42 MeV cyclotron for radioisotope produc­tion is essentially operational. The two solid target stations have been installed and the two gas targets are close to completion. After some more tuning to reduce beam losses it will be available for isotope production at a gradually increasing rate.The "PETT VI" positron emission tomograph was completed and moved to the UBC Health Sciences Hospital. The machine is ready for commis­sioning with short-lived radioisotopes from the 42 MeV cyclotron that will be trans­ported via a 2.5 km long pipeline, which was also installed during the year.Looking back on 1982, progress with the various programs within the Applied Programs Division has been impressive. More detailed information on the various APD activities can be found in the following sections, presented in two groups: Programs and Facilities.PROGRAMSBiomedical programThe year 1982 has been a very exciting one for the TRIUMF biomedical group because, after a decade of planning and development of the tt-  channel, we were able to initiate tT  radiotherapy with deep-seated tumours. We have been irradiating human skin nodules since November 1979 in order to study the acute and late effects of ir- irradiation in patients and to estimate the relative biolog­ical effectiveness (RBE) of our ir” beam. With the installation of the computerized scanning couch in February, we were able to produce better quality dose distributions for large volumes (~1000 cc) which are suitable for clinical use. On the other hand, the perform­ance of the TRIUMF cyclotron in terms of stability and reliability at high intensity operation has also been greatly improved after a major renovation at the end of 1981. Three major patient treatment cycles were undertaken in May, August and November. Sixteen patients were treated, including eight brain and seven pelvic tumours. The relatively long treat­ments have been well tolerated by all the patients, who volunteered in this clinical trial. We have been observing the patients for several months now; however, it is still too early to give any preliminary assessment of the results of these it-  treatments.Two treatment protocols were initiated this year: brain tumours (glioblastoma multiforme) and advanced pelvic tumours (rectum, bladder and cervix). The former regime was a collab­oration among the three ir~ facilities (LAMPF, SIN and TRIUMF) in order to establish inter­national trials. It consists of a pion boost dose of 1750 rad in 14 fractions to a primary field of 4000 rad in 20 fractions to the whole brain. After these preliminary studies we expect to move on to use total pion dose rather than just boosting. The pelvic tumours were treated with pions only to a total dose of about 3000 rad in 12 fractions. The patients were treated using two opposing fields whenever possible. This helps to reduce skin dose and also to reduce any vari­ation of the quality of the n~ beam over the tumour volume.The it-  irradiation was delivered using a unique discrete step lateral scanning and62Table VI. Summary of TRIUMF pion patient treatment for 1982.Fractions finished Total Dose/fractionRun Patient Fractions intended days ( it -  rads)Feb X skinnodule2/3 4 700May XXbrain 14/1414/141616125125Jul X bladder 10/10 11 250X bladder 10/10 11 200X brain 14/14 16 125X brain 14/14 16 125X brain 3/14 3 125X brain 14/14 17 125X bladder 10/10 12 250Nov X brain 14/14 25 125X bladder 12/12 22 250X brain 14/14 17 125X bladder 12/12 26 250X rectum 12/12 18 250X bladder 12/12 13 250range shifting system because (a) a mathemat­ical technique using linear programming has been developed successfully in-house to use discrete scanning and range shifting;(b) stepwise movement is much simpler to ope­rate and to maintain than the conventional continuous movement systems; and (c) it uses integral beam intensity monitor pulses as clock pulses and so can be relatively immune to large fluctuations in beam intensity.In order to achieve the best uniformity the scanning is done in a hexagonal fashion, or composite of hexagons. At each spot position a complete range shifter cycle will be delivered. Since the shape of the depth dose profile depends only on the relative ratio of the monitor pulses used at each of the eight sectors of the range shifter, while the total dose depends on the sura of all the monitor pulses on the eight sectors, the shape of the depth dose profile and the total dose for the profile can hence be varied independently.In general the range shifter function can be made different for each spot in a lateral scan to allow for the varying thickness (i.e., depth) of the tumour, as well as to compensate for varying inhomogeneity and skin curvature. However, for simplicity in our initial work, plastic tissue compensators made using computerized tomography data were used to compensate for tissue inhomogeneityand skin curvature instead, and the range shifter was used only to cover the varying thicknesses of the tumour.Due to the production of long-range secondary charged (protons) and uncharged (neutrons) particles following tt-  capture, the lateral profile of a uniform-step scanned tune for a finite size of about 10 cm in width will appear dome-shaped. Simple edge boosting of the field was found to be adequate for first- order flattening of these fields. This is achieved simply by delivering the same range shifter profile but at higher dose for the spots along the perimeter of the treatment field. We observed that, for the pencil beam tune developed in 1982, a 100% boosting is required for a 6 cm hexagonal field, whilst only 60% is required for an 8 cm hexagon. In general the amount of edge boosting required decreases with increases in field size.The brain tumour patients were immobilized in thermo-plastic shells which were bolted down to the treatment couch. The precision of this set-up is in the order of about 1 mm. Thermo-plastic shells were also used on pelvic patients initially. However, they were found to be too uncomfortable for these long treatments and hence polyurethane molds were used instead. The set-up precision of these pelvic shells is in the order of about63Fig. 66. The biomedical channel, the range shifter and the treatment couch.MANUAL INCLINATION OF TABLE (±20°)Fig. 67. An elevation view of the scanning couch for pion treatment.64Fig. 68. Brain tumour irradiation. The pion beam exits from the last quadrupole on the right. The apparatus shown are (from right to left) the primary beam collimator, the range shifter, the patient collimator, the compensator and the plastic shell enclosing the patient's head. The last three are fastened to the couch and move with the patient during scanning.0.5 cm. At a steady 120 pA at 500 MeV output from the TRIUMF cyclotron, a brain tumour treatment takes about 20 to 30 min, while a pelvic tumour requires an hour or more. Treatments are conducted every day of the week except when the beam is off for maintenance and development, which is usually scheduled on Wednesdays. A pre-set-up procedure has now been developed so that patients can be set up outside the treatment room on a simu­lated couch top. This has helped to minimize the patient change-over time and to reduce staff irradiation dose, as the general radia­tion background during beam-off (i.e., M8 beam blocker in, but full beam still on 1AT2 target) is in the order of 10-50 mrem/h.These patient treatments were handled by physicists from the Medical Biophysics Unit of the British Columbia Cancer Research Centre with medical support from the staff of the Cancer Control Agency of British Columbia.TRIM programproduction from the beam line 4A cesium target came to an end on May 26, 1982 to allow for the dismantling of the facility in the spring shutdown. The isotopes from the last runs in 1982 were used to complete a phase of the myocardial studies at Vancouver General Hospital and for some preliminary labelling studies at the University ofAlberta. Another interesting application of TRIM iodine has been the tomographic visual­ization of metastatic melanoma to the liver. This work was done at the VA Hospital in Seattle. 123j from TRIM was labelled to monoclonal antibody fragments that were engi­neered to be specific to this type of tumour. In spite of the fact that this trial was successful from the scientific standpoint, more work must be done in close collaboration between the user and TRIM to define and control the relevant quality factors in future 123I production to arrive at a reli­able and routine protocol.Most of our effort since the end of May has been concerned with the removal of the old cesium target facility and the relocation of the TRIM trailer to the vault south berm. Design features incorporated into the cesium target at construction allowed us to accom­plish the final packaging of it for disposal at a fraction of the man-dose predicted by TSG. The trailer was thoroughly cleaned prior to its relocation and several thousand kilograms of lead was removed in order to lighten the load. At the end of the year the hot cell is being reconstituted and connected to beam line 2C for radioiodine and radio­bromine reception. The control system is being integrated with that of beam line 2C in order to provide for more centralized moni­toring and data acquisition.Positron emission tomographyThe construction of the PETT VI positron emission tomograph, which was begun at TRIUMF in April of 1981, was completed in July of this year. A number of improvements over the original design by the group at Washington University, St. Louis, Missouri were incorpo­rated. These were primarily in the area of coincidence recording electronics and in microprocessor and computer-related hardware. Reconstruction and diagnostic software were written for the TRIUMF VAX 11/780 computer system. The tomograph construction was con­ducted with strict adherance to PERT proced­ures, and was completed within one month of the scheduled date, and close to budget.The completed tomograph was shown to provide a resolution in-slice of 7.8 mm. These and other physics and engineering data were the subject of a publication [Evans et_ al., Proc. IEEE 1982 Nuclear Science Symposium, Washington, October (in press)].65In November, the tomograph was disassembled and reinstalled in the PET suite in the Acute Care Unit of the UBC Health Sciences Centre Hospital. It was connected to a VAX 11/750 computer system in the UBC Electrical Engineering Department by means of a glass fibre optics cable, approximately 1 km in length, which carried data from the tomo­graph on a serial CAMAC loop and recon­structed RGB video images back to the hospital. The link also serviced computer peripherals.Work on the production of PET scanning agents also continued this year. Towards year's end the first beam from the CP42 cyclotron was incident upon oxygen and neon gas target systems for the production, respectively, of oxygen-15 and fluorine-18.The inorganic gas chemistry for conversion of oxygen-15 into labelled 02, H 20 and CO was established. The process for the production of 2-deoxy-2-fluoro-D-glucose (FDG) labelled with fluorine-18 was also in place by the end of the year. A newer FDG synthesis involving acetylhypofluorite was developed and was the subject of a publication [Adam, abstract,10th Int. Symp. of Fluorine Chemistry, UBC, August].At the same time, a program of research into the synthetic chemistry for new radio­labelled agents, particularly dopa, was pursued and resulted in several publications.Transport of the radio-labelled scanning agents, particularly those labelled with 2- minute oxygen-15, from TRIUMF where they were produced to the ACU hospital for scanning applications, necessitated construction of a fast transport system. Four 2.7 km long pneumatic tube transport systems (rabbit lines) were installed in a conduit 4 ft below the ground surface between TRIUMF and the ACU, with nine intermediate manhole access points. Shielded send and receive stations were installed at the ends of the line together with sensing equipment for locating the position of a rabbit in transit. By year's end the system was undergoing tests.Radioisotope processing (AECL)There was good availability of beam to the 500 MeV production targets in 1982 and com­mercial shipments of 87Cu, 88Ge, l"Cd and1 9  7i^/Xe were made. After eighteen months of routine production it was decided not toschedule further runs of 67Cu because the world-wide demand for this isotope has turned out to be disappointingly low. 127Xe, 109Cd and 58Ge are maintained as stock items with the bulk of the shipments in 1982 being to Europe.Acceptance testing of the Cyclotron Corpora­tion CP-42 is progressing steadily (albeit slowly) and 57Co, 67Ga, 123I and 201T1 will be available in commercial quantities at the end of the first quarter of 1983.NAA (Novatrack)The neutron activation analysis program at TRIUMF continued a steady growth pattern in 1982. The rotating irradiation facility at the thermal neutron facility has proven to be very reliable and accounted for most of the irradiations done at TRIUMF during the year. At the same time an increased reliance is being placed on doing irradiations at the two universities in Washington State. The reactor centre at Washington State University in Pullman handled the bulk of our workload in 1982. All counting of irradiated samples, however, continues to be done at the TRIUMF site. Doing irradiations elsewhere was necessary because of the fairly long periods of no beam at TRIUMF. During scheduled beam periods in 1982, however, the current was sufficiently high, and the schedule suffici­ently reliable, to accommodate all required irradiations for neutron activation analysis work.This year about 26% of all irradiations were done at TRIUMF (up from 22% in 1981), 60% in the reactor centre at Washington State Uni­versity, and 14% at the University of Washington in Seattle.The majority of the users of the facility were industrial clients and government agencies. For the second year in a rowNovatrack obtained the contract for thestanding order for neutron activation analy­sis work of the Geological Survey of Canada, and an increasing number of Japanese and European industries and government agencies are sending samples for analysis to the Novatrack facility.No major new equipment acquisitions were madein 1982. The existing equipment is now beingused to about 90% capacity. Staff levels for the facility have now levelled off to 6 full­time positions.66A new rotating irradiation facility has been designed and fabricated for the new thermal neutron facility moderator tank. This new design should provide us with even higher flux levels for 1983.FACILITIES500 MeV isotope production facilityThe year 1982 was the third year of operation for the 500 MeV isotope production facility. The facility performed without failures and could cope well with the higher maximum beam current run during some periods. It received ~120 mAh, considerably more than during the previous two years. The use of the facility over the three years is illustrated in thellowing table TargetsmAh to Targets deliveredYear facility irradiated to AECL1980 51 40 261981 56 53 381982 120 49 42Of the nine different target materials irrad- ated in 1981, four turned out to be marketabl for the present. The production of the faci-e lity for 1982 is tabulated as follows:Number ofNumber of targets Target targets deliveredmaterial Isotope irradiated to AECLCsCI  127Xe 42 31In 109Cd 2 6*Zn 67Cu 4 4As 68Ge 1 1*Four of the six delivered targets had al­ready been irradiated during 1981.The 42 MeV cyclotronThis cyclotron will provide beams of 200 pA at 11-42 MeV to produce radioisotopes for processing and marketing by AECL's Radio- Chemical Company and for the positron emis­sion tomography project. It was delivered early December 1981. By January 1982 the machine was evacuated to 2 x 10“ 6 Torr, indi eating no major leaks had been introduced during transportation.Installation of the cyclotron, by TRIUMF staff with guidance from the supplier (The Cyclotron Corporation of Berkeley,California), took more time than anticipated. This was due to delays in the supply of equipment and instructions, caused by the fact that the company had to commission five of these cyclotrons at the same time, with more on order, and was unable to cope with peak in their workload.On May 23 the cyclotron accelerated its first internal IT1" beam to a nominal 42 MeV. Within a month H“ beams were obtained also and the beam losses were reduced to an acceptable value at the 1 pA beams used for commission­ing. A 30 MeV beam was extracted to the port where an isotope production target station, was to be installed later.Early in July the variable energy beam line components and the two isotope-production tar­get transfer systems were delivered, after one of the systems had successfully passed the factory acceptance tests. By the end of the month the first "rabbits" were transferred between target station and hot cell. By the middle of September both target transfer sys­tems had passed the site acceptance tests.Both factory and site acceptance tests con­sisted of a series of 50 consecutive runs dur­ing which the systems should not fail. In spite of these severe tests several problems were still encountered during actual operation of the systems, and some more work is needed to achieve better reliability and interchange­ability of items such as targets and subcarriers.By October the variable energy beam line, ex­tractor mechanism and magnetic channel were installed and commissioning of this beam line was started. On November 15 the energy of the extracted beam was calibrated against the mea­sured range in aluminum. It turned out to be 41.10 ±0.51 MeV, which is only 0.4 MeV short of the 42 ± 1 MeV quoted by the company. By the end of the year beams of nominally 42, 30, 20 and 11 MeV were delivered at the experimen­tal area target station with transmissions of 100%, 87%, 94% and 40%, respectively, with respect to the stripping foil current. The company quoted 90% in its specifications. The magnetic channel was not used during these runs and is expected to improve the transmis­sion by correcting for the defocusing effect of one of the magnet sectors for some energies.The users got a foretaste of things to come in 1983: on October 26 AECL's first thallium test target was bombarded with 400 nA of 30 MeV protons for 15 min. The next target was irradiated on December 4 and the third67Fig. 69. The Cyclotron Corporation's CP-42. Fig. 70. The 11-42 MeV variable energy beamThe upper magnet core and coil and vacuum line,chamber lid are raised for servicing.Fig. 71. The 42 MeV control room.Fig. 72. The 30 MeV target station. The beam enters through the pipe on the left and the irradiated target is transferred through the curved pipe at the top of the picture.Fig. 73. The neon and oxygen gas targets in series, at the end of the 11-42 MeV beam line.68target received 70 pA for 30 min on Dec 22. For the PET program the first bombardment of the neon gas target took place on December 6 at 42 MeV and 400 nA. The sample yielded 0.5 mCi of 18F, which was subsequently pro­cessed to FDG.Beam line 2CThe development of beam line 2C this year concentrated on the design and construction of five target facilities. Two beam tests were completed to check on the beam line design and to measure the extraction effici­ency of a wide stripping foil.The first target to be developed for beam line 2C was a metallic cesium heat pipe which will operate at 350°C and 100 MeV to produce 127Xe in the on-line mode. This assembly and its beam stop was bench tested at an equiva­lent of 60 pA beam. It was installed in BL2C5 during the spring shutdown. The second target to be developed is a sodium iodide generator for radioiodine production. This target has been built and is being presently tested. Installation in BL2C3 is planned for January 1983. The third target is water- cooled beryllium for fast neutron production in BL2C1. Construction is finished but no testing has been completed. Targets 2 and 4 are, respectively, a radiobromine generator and a general purpose solid target rabbit system. These facilities are in the design phase. The controls system has been enlarged to monitor and control elements of the tar­gets system required for safe operation.Several beam tests were carried out at the 1 pA level in February and March when four energies, 70, 72.5, 100 and 110 MeV, were brought to a Faraday cup at the target loca­tion in BL2C4. It was found that the line was easy to tune at these levels with 100 pA circulating in the cyclotron and beam spots less than 6x6 mm2 were readily achievable on target. In the spring shutdown one of the strippers, normally 2.5 mm wide, was replaced with one 10 mm wide. The purpose was to verify calculations made by the Beam Develop­ment group on extraction efficiency versus foil width. A measured efficiency of 27% for the 2.5 mm and 99% for the 10 mm at 70 MeV confirmed the predictions. These measure­ments will be of importance for the applica­tion of the new variable energy, multifoil mechanism under development by the Probes group.M8 upgrade projectCalculations have shown that the flux of 180 MeV/c ir“ from the biomedical channel M8 could be improved by a factor of two by inserting a 20 cm long, 10 cm diameter aper­ture, samarium-cobalt permanent quadrupole magnet between the production target 1AT2 and the first conventional quadrupole. Early in 1982 this project was given priority and the two major design problems were studied. One concerned the mechanical design problem of modifying the existing M8 blocker assembly so that the permanent magnet quadrupole could be inserted and rotated into position while still retaining the blocker mechanism. The other was to determine whether the SmCo 5 material could withstand the radiation and thermal damage which would result from the close proximity to the meson production target and the primary proton beam.A detailed design of the blocker-quadrupole combination has been completed by the engi­neering group at TRIUMF, Victoria; however, the results of the radiation damage studies have not been optimistic. A sample of SmCo 5 was mounted on the 1AT2 target assembly at a 10 cm distance from the production target. After a three-month irradiation the sample was found to be reduced to a non-magnetic powder. The sample container indicated severe overheating so that negative result was attributed to direct heating by the incident proton beam during a mistuning incident. A controlled experiment to study the radiation effect of 500 MeV protons on the magnetization of SmCo5 was mounted in the beam line 4A irradiation facility. Thermo­couples were used to keep the sample tempera­ture below 120°C and beam monitors were used to control the beam position and intensity.The magnetization was measured in situ by rotating a flux coil over the sample. The initial result of this measurement is that a 13% decrease in magnetization was observed with an exposure of 3x1017 protons/cm2 with an average energy of 480 MeV. This is about a factor 50 less flux than the material would receive in one year at the point of closest proximity when mounted on the M8 channel. A LAMPF measurement has shown that when exposed to 1018 neutrons/cm2 (energy < 0.1 MeV) the magnetization loss of SmCo5 is less than 1-2%.This project is on hold until further radia­tion damage studies are made. One aspect of the upgrade which will continue is the in­stallation of a new power supply on the first quadrupole. This could result in a 10% increase in the channel flux.69C Y C LO TR O N  D IV IS IO NThe higher emphasis given to machine relia­bility made 1982 a year of excellent beam production, with 4650 h of accelerated beam and 229 mAh of total extracted beam charge, more than twice the charge produced in any previous year. The downward trend observed during 1981 (see Fig. 75) was definitely reversed in 1982, with new records achieved, not only for the total beam charge but also for the maximum peak beam current extracted.In a 10% duty cycle pulsed mode peak currents of 225 pA were obtained, up from 205 pA in1981. At these levels space charge phenomena in the injection line and beam loading of RF and electrostatic components become signifi­cant and have to be thoroughly understood and compensated in order for the peak current to be increased.A detailed understanding of the causes for the observed limits in the beam transmission at the high intensities is being achieved with beam measurements, evaluation of compo­nents and space charge calculations. Recent­ly, a gain in transmission through the cyclo­tron was obtained by increasing the power of the two injection line bunchers. In addi­tion, a collimator limiting the energy accep­tance through the injection line, and there­fore the energy dispersion introduced by the bunchers, was altered in size to be compat­ible with the higher buncher voltages required at higher currents (see details in the ISIS section). The ion source output is no longerFig. 75. Beam charge delivered (broken line) and hours of operation (solid line) over the past several years. Milestones in extracted peak current are also indicated. The histo­gram shows the charge delivered per month.the limiting factor. With the most recent developments sources providing more than 1 mA within an emittance of less than 0.2tt mm-mrad (normalized units) are avail­able. Without space charge or beam loading phenomena this type of beam would normally be transported with a transmission of >80% through the injection line and >50% through the machine, corresponding to an extracted current of >400 pA.For high intensity operation and meson pro­duction the beam was extracted, for most of the year, at 500 MeV and the average beam current was kept at 120 pA or a little lower. However, during two production periods lasting several days each the extracted current was increased to 140 pA as a test. During the first of these periods a failure occurred in the stripping foil mechanism, possibly related to the higher temperatures. During the second period, performed at 475 MeV, everything went well and the results seemed to confirm, within the experimental error, the 1/3 reduction in machine activa­tion expected from the reduced electromagnet­ic stripping in the cyclotron. The 475 MeV value was chosen since the higher intensity (of about 130 pA), required for a pion production equivalent to the production from a 500 MeV 100 pA beam, is still within values at which the machine can be reliably oper­ated. The availability on schedule of the high intensity beam was altogether satisfac­tory, enabling cancer patients to be treated on a daily basis (except for maintenance days). Sixteen patients were treated during the year, each of them with many daily fractions.The maximum extracted cw current was limited to 150 pA by the 50 kW cooling capacity of the present thermal neutron lead target (TNF), used as a beam dump. During the coming January shutdown a new lead target and a new moderator tank will be installed. This will allow 125 kW cooling capacity in the lead target, compatible with currents greater than 400 pA extracted from the cyclotron, as reported below in the report from the thermal neutron facility group. However, the present meson-producing targets are adequate only for currents up to 200 pA. This will set the upper limit for production tests at 475 MeV or 500 MeV during the coming year.70During the first part of the year the polar­ized beam operation went through a period of poor source behaviour with lower output current and frequently required maintenance. The cause was trivial, i.e. insufficient diluent in the suspension used for the fila­ment coating. However, it took quite an effort to locate the problem. Recently the source has again delivered its maximum out­put. More than 300 nA, 75-80% polarized, could be extracted from the cyclotron during operation. The recent installation of the spin filter, which will allow 1 kHz spin reversal without appreciable change in the spatial distribution of the emittance figure, is a significant upgrading of the polarized beam facility.In another development an ECR proton source was inserted in a Lamb-shift assembly in the laboratory and found to produce a polarized current output similar to the one obtained from the Lamb shift assembly when equipped with a duoplasmatron. The ECR source built was very compact and therefore had a factor of 10 less ion density than expected. An ECR source Mark II of larger size is being built and is expected to give at least a five-fold increase in polarized beam intensity.Another advantage of the ECR source is the absence of filament and the longer lifetime between maintenance.The resonator system in the cyclotron tank operated quite well this year; definitely a major factor in the excellent beam operation and the satisfactory production records achieved. The resonator reliability defi­nitely improved since the hot arms of most of the eighty segments were aligned under RF load in 1981. Since then their position has been monitored several times both in RF on and off conditions and has been found to vary only slightly but unpredictably, with a ten­dency towards increased sagging, especially for the lower segments. Measured deviations of the hot arms were compensated for, when­ever possible, with equivalent displacements of the opposite ground arm panels, which are adjustable through vacuum feedthroughs. This technique has allowed maintaining strong back temperatures and other RF related leakage effects within non-disruptive limits. How­ever, it should be pointed out that some of the hot arm and ground arm panel positions are at the limit of their adjustment range.A resonator straightening program may therefore be required should the alignment deteriorate substantially before the installation of the new resonator segments.Although melting of resonator components or severe damage to probes slits or other devices requiring emergency tank openings could be avoided, the reliability and avail­ability of diagnostic equipment and the stability of the correction plates were still marginal because of remaining RF leakage.This leakage has always been one of the major sources of problems. Therefore, two different lines of attack are being followed:1) Mechanisms and diagnostic devices are being progressively modified to be compatible with higher temperatures and an RF environ­ment of a few kV. Modified slits and flanges were recently installed by the Probes group. New low energy probes and correction plate wireways are being designed and tested.2) The study of the RF leakage field was intensified. Numerical and analytical calcu­lations and detailed measurements with an accurate 1:10 scale aluminum model of the entire cyclotron tank were performed. The Cyclotron Development group was asked to join the RF group in this investigation. The collaboration with experts from CERN and Brookhaven was very valuable in setting up the proper techniques. The natural resonat­ing tank modes, excited in the tank volume traversed by the beam at frequencies close to the operating frequency, were identified and a way of reducing the leakage by 15 dB was found during the model investigation. This was based on shifting the resonating frequen­cies of the natural tank modes away from the operating frequency of the RF cavity. Measurements in the cyclotron tank are planned for the coming shutdown in order to establish whether the improvements achieved in the model can be realized in the main cyclotron tank. The benefits of a 15 dB reduction in the cyclotron tank would be enormous. Phase probes, low energy probes, and other diagnostics would become reliable and more available for operational and developmental purposes. The temperature of the resonator strongback and the interaction with cryopanels and correction plates would be greatly reduced with great benefit to beam stability and vacuum. Installations of new devices for multi-turn extraction (kaon factory injection) or for other developments would be facilitated. The maintenance time of cyclotron components in the tank would be reduced, implying a reduction in personnel exposure to radiation. For these reasons the study of the RF leakage was made an important part of the resonator replacement program, so that the results can be taken into account in the new resonator replacement program.71The design activities for the new resonator system and the construction of the new proto­type segment were substantially intensified since the beginning of the year. The mechan­ical engineering staff was increased by a few professionals and technicians. The prototype of the new segment, designed with an improved mechanical structure and with better materials adequate for the temperatures known from the present operational experience, is now practically complete with several mechan­ical tests already successfully performed. A few difficulties had to be overcome and a few design improvements were incorporated, causing the loss of a few months on the prototype schedule. An RF test facility was installed and is presently almost complete with power and vacuum units. Electrical testing in vacuum and at full power will start shortly. A stress analysis and a vibration analysis will also be performed in collaboration with outside experts. The details of this project are described below in the resonator report of the cyclotron section.Highlights of the year were the new records achieved for the magnet stability and the cyclotron vacuum. The magnet stability was improved to <±0.7 ppm over periods of half an hour by improving the feedback circuits in the main power supply. Using external beam phase information as a feedback it is now possible to keep the beam phase stable within ±0.7° in RF phase, a factor of two improve­ment with respect to previous results. The vacuum reached values around 1x10“ ® Torr with RF off and 4xl0-8 with RF on. This resulted from a consistent search for and fixing of leaks. A major leak was eliminated by weld­ing the vacuum box of the combination magnet in beam line 4 directly onto the exit horn (see Beam Lines report).A detailed analysis of the faults causing machine downtime was performed by Operations in collaboration with the groups. The results are shown in the section on opera­tional services (Fig. 85, p. 89). It appears that RF problems, mainly RF transmitter and controls, are still the leading cause of downtime, followed immediately by ISIS, main­ly ion sources. Measures are being taken to improve both these situations. It should be noticed that the Controls group were able to reduce significantly the controls related downtime in spite of the commissioning on line of the new multiport memory system which was completely installed and connected to the various control computers according to thescheme reported last year. Part of this success is due to the fact that improvements and changes can, with the new system, be inserted on line. The air conditioning of the level 264 service annex and improved cooling circuits in the experimental areas made TRIUMF cope well through the busy and hot summer months, where in previous years an intensification of faults and downtime was recorded.Progress toward higher yearly integrated currents was made by making several sections of beam line 1 and beam line 4 radiation hard and remotely handleable. With the improve­ments planned during the coming winter shut­down for the combination magnet on beam line 1 and with the upgrading of the vault entrance floor to allow easy removal of heavy equipment from the vault, the vault improve­ment program as defined in one of our major basic projects will have been completed. The new remote handling building with its service area, test area and control unit separated from the vault constitutes a significant step forward toward efficiency of vault mainte­nance and lower dose exposures.A committee was struck at the beginning of the year to identify and assess the problems to be expected as the integrated extracted beam currents continue to be increased and to recommend the action to be taken in order to be able to operate at reasonable rates of man-dose exposure. The committee for higher yearly average current (HYAC) received reports on the dose study for some of the more critical cyclotron systems. Other interested individuals made presentations to the committee outlining the requirments for longer periods of higher-intensity beam pro­duction and methods for achieving lower residual fields or less exposure of person­nel. The committee concluded that, in view of the upcoming resonator replacement program and assuming no other improvements are made toward reducing exposure, the total yearly extracted beam charge should be limited to 200 mA h for 1983, a level similar to that achieved in 1982. It also recommended that techniques such as running with equivalent pion production at 475 MeV and adding third harmonic to the RF be implemented to reduce the beam losses in the cyclotron in order to allow higher yearly total pion production. Other recommendations included better monitoring of beam losses, availability of spare equipment and more manpower trained for some of the more specialized tasks which have to be carried out in high field areas.72BEAM PRODUCTIONThe work done in 1981 to increase machine reliability has paid great dividends and the total integrated current delivered was229,000 pAh. This is approximately double the output of the previous record high. The high intensity beam was scheduled for a total of 3500 h and available for 2900 h. Polarized beam operation during the year was also quite successful with 1165 h of polarized beam operation scheduled and 985 h available.Beam line IB received beam 90% of the time it was available and beam line 4, 86% of the time. The success of the year's operation cannot be attributed to any single change but to a series of many factors.Figure 76 shows the non-polarized current produced in relation to that scheduled for the year, and also shows the weekly scheduled and actual production. The particular shape of the curve reflects the scheduled sequence of operation, which typically was 6 to 7 weeks of high current operation, followed by 2 weeks of polarized operation, and then about 2 weeks of maintenance and development.In September-October a 7-week shutdown was scheduled to rebuild the front end of beam line 4 and to do miscellaneous work in the cyclotron vacuum tank.Only two significant interruptions in the beam schedule occurred. The first was at the beginning of the year when trim coil zero failed and had to be replaced. The second was in November when oil from a diffusion pump was accidentally sprayed into the vertical injection line. Also the beam line 4 combi­nation magnet cooling coil required repair, and the RF system had an intermittent capaci­tor failure. The total scheduled time lost was about one week each in the spring and fall.Table VII is a summary of all experiments which were scheduled to run at TRIUMF and the beam which they received. The title of each experiment and the experiments' spokesmen are listed in Appendix C.CYCLOTRON Cyclotron developmentThe main effort in cyclotron development reflected the continued emphasis on reliabil­ity and the requirements for improved beam quality. Efforts in the study of the RF leakage in the vacuum tank region outside of the resonator cavity were greatly increased. Substantial improvements in the main magnet stability were obtained. Progress continued in the area of cyclotron diagnostics and cyclotron data acquisition.cocr=)oX<ocr<xCJ<LUCDcn cr =) oX<LUOcr<xo<LUCD<O2 5 0 0 02 0 0 0 01 5 0 0 0100005 0 0 0 -  5 0 0 0 0H  SCHEDULED J  DELIVERED2 5 0 0 0 02000001 5 0 0 0 010000010 Hour =2 0  3 0W E E K-33.6*10 Coulomb(SCHEDULED)^■229mAh( T O T A L )I fJLAFig. 76. Beam production, scheduled vs. actual.73Table VII. Beam to experiments - total 1982Experiment* Channel Scheduled Deliveredh pAh h pAh %Maintenance 481.5/21 605 437.8/21 675Development 572.3 420.35QQD Mil 370 28 205 318.7 23 976.49 85.0Tests Mil 92 pol. 83.5 pol. 90.79 Mil 725 54 050 564.15 40 508.5 74.947 Mil 46 4600 37.65 3861.11 83.947 M20 276 27 600 205.8 16 997.01 61.660 M13 167 5010 122.65 4348.6 86.861 M8 92 pol. 83.5 pol. 90.761 M20 138 13 800 119.65 11 552.16 83.771b M20 173 17 300 167.19 18 889.93 109.288 Mil 252 25 200 234.1 21 064.59 83.688 M20 196 3120 75.15+83.5P 1586.96 50.9 (80.9 h)104 M9 3057 26 577 2533.99 219 218.95 82.5122 M20 127 8600 102.15 6746.8 78.5127 M9 104 3120 75.5 2039.6 65.4127 M13 265 20 730 199.44 12 915.13 62.3134 Mil 310 19 240 228.0 12 780.4 66.4134 M13 536 52 880 513.34 49 310.93 93.3140 M9 435 478 149.95+101.2P 361.61 75.7147 M9 832.5 49 735 621.7 37 074.67 74.5150 M20 515.5 49 895 436.5 42 410.22 85.0154 M20 173 17 300 148.4 15 097.04 87.3157 M20 573 51 530 476.3 40 305.02 78.2159 Mil 616 55 280 599.64 51 729.43 93.6160 M20 138 13 800 119.65 11 552.16 83.7166 Mil 112.5 10 530 104.25 10 003.96 95.0166 M13 257.5 25 750 237.77 22 738.7 88.3168 M13 323 32 300 248.8 23 308.32 72.2173 M13 150 15 000 128.0 12 705.99 84.7177 Mil 127 12 700 106.0 9659.55 76.11 7 8 M1 3 115 11 5 0 0 8 5 . 8 5 8 5 1 3 . 7 5 7 4 . 0185 M13 1025 75 050 782.2 57 331.24 76.4191 M20 369 36 900 356.05 33 788.36 91.6199 Mil 531 53 100 491.74 51 856.92 97.7202 M13 338.5 20 800 280.38 16 565.4 79.6205 Mil 669 54 615 404.65 34 808.01 63.7209 Mil 553 55 300 465.35 42 974.86 77.7211 M13 231 23 100 218.0 22 529.99 97.5213 Mil/13 123 12 300 120.75 12 585.0 102.3187 IB 821.5 +23 Dev.Pol. 560.0 Pol. 68.22C 2C 24.0 22.0 91.7MRSdevelopment 4B 58 11.42 19.7MRS upgrade 4B 80 15.5 19.4Perm.magnet 4A 34.5 32.65 94.6SEMdevelopment 4B 92.0 14.1 15.377 4A 107 79.05 73.9114 4B 155 84.65 54.674Table VII. Beam to experiments - total 1982Experiment* Channel Scheduled h uAhDeliveredh pAh %117 4A 320 284.9 89121 4A 241 133.2 55.3121 4B 114.5 64.6 56.4131 4B 208 150.75 72.5132 4B 346 253.55 73.3143 4A 126 90.25 71.6165 4B 150 Pol. 93.7 Pol. 62.5169 4B 276 169.7 16.5170 4B 126.5 104.3 82.5171 4B 643 320.1+73.2P 61.2174 4C 517 357.45 69.1189 4A 69 35.9 52.0190 4A 172 83.7 48.7192 4B 115 96.15 83.6195 4B 123 76.45t 62.2206 4B 115 74.85 65.1208 4B 139 37.15 26.7212 4B 87.9 110.75 126.0*See Appendix C for experiment title and spokesman. tPoor beam, 50% useful.RF studiesRF leakage, due to misalignments in the reso­nator structure and other small differences in parameters, has in the past been severe enough to cause RF heating of uncooled sur­faces. It has also damaged diagnostic probes and interfered with the operation of the cryopanels. Large RF-induced currents make beam measurements with the low-energy probes and internal non-intercepting phase probes extremely difficult. During 1982 a major study of the RF leakage problem was embarked upon, by means of model studies and computer relaxation calculations. The model, one- tenth the size of the machine, was construc­ted entirely of aluminum. Initial measure­ments were carried out using solid panels to model the upper and lower dees. The model was excited with “1 W of RF power and the resulting resonances, observed with a network analyser, are shown in Fig. 77(a). A special high impedance probe, designed at CERN, was used to measure the RF voltage between the upper and lower lids of the tank in the region behind the centre of the resonators.The effects of the cryopanels, the centre post, and the upper-to-lower hot arm shorts (at the centre and the edge of the dees) were measured. The effect of distortion of the hot arms on the leakage, measured by uniform­ly displacing the hot arm tips away from the symmetrical position, is shown in Fig. 78.It can be seen that the estimated leakage of 2-3 kV in the machine implies asymmetries equivalent to a uniform displacement of 6 mm of the resonator hot arms. This is not surprising considering the size of the dis­tortion and misalignments which have been measured for the present individual resonator segments. A SUPERFISH calculation of the leakage, based on a 2-dimensional approxima­tion of the RF cavity, is in reasonable agreement with the measurements. The separation between segments was simulated by cutting slots in the solid panels. The effect was an increase of 10 dB in the leak­age. A frequency scan of the leakage region showed a number of "tank" modes, Fig. 77(a) and (b). Each mode implies a pair of resonances corresponding to the push-pull and push-push mode in the quasi-circular tank volume. The cyclotron operating frequency is located on the shoulder of the lower of two nearby tank resonances. The spatial distri­bution of these resonances was measured using a grid of 100 holes drilled in lower quad­rants 3 and 4. The results for the resonance pair at 215/218 MHz nearest the fundamental push-pull cavity are shown in Fig. 79(a) and compared with the results of numerical calcu­lations [Fig. 79(b)]. The 2-dimensional cavity code SUPERFISH was modified to perform75mT>01LJ50CLU.01EQUIVALENT DISPLACEMENT  FROM SYMMETRICAL POSITION (mm)- 8 0100 200  260 EXCITATION FREQUENCYOPERAT IN GFREQUENCYRELATIVE TO THE  RF VOLTAGE ( 1 0 0 , 0 0 0  V )J measured value—  calculated I  value (Superfish)Veq ( volts) - 3 0 0 0  -- 2000-- 1000Fig. 77. Network analyser frequency scan of resonances excited in the 1:10 model: (a) at the dee gap in the RF cavity; (b) behind the root of resonator No. 8 in the tank; (c) at the same location as (b), but with selected resonator slots shorted, showing the shifted TM31q tank resonances.Fig. 78. Stray electric field measured in the 1:10 RF model of the cyclotron tank. Voltage and displacement are scaled up to corresponding cyclotron values. The results of a calculation with program SUPERFISH are given for comparison.RF relaxation calculations in a simplified 3- Comparison with the measured voltage distri- dimensional geometry approximating the TRIUMF bution shows that the 215/218 MHz resonancequasi-circular tank geometry. Higher capaci- pair corresponds to the push-pull and push-tance (narrow gap) regions were simulated push components of the TM31q mode. Otherwith regions of higher dielectric constant. resonance pairs at 123/138 MHz, 144/154 MHzIm CYCLOTRONFig. 79. Electric equipotential lines of the TM31Q tank resonance pair, (a) Measurement in the 1:10 model at 215 MHz (right) and 218 MHz (left). The shaded region corresponds to the tank region between the upper and the lower resonators. This region is not accessible and was not measured, (b) Calculation using a quasi-3-dimensional cavity computer code (a modified SUPERFISH). The shaded region has a higher capacitance to approximate the geometrical effects of the resonators.76and 238/240 MHz show patterns in agreement with the TM110, TM210 and T M ^ q modes. Work is now in progress to show whether these tank modes also occur in the machine and to determine their significance to the cyclotron leakage phenomena. A preliminary spectrum analyser scan of the resonances was performed in the machine (Fig. 80) and indicates a spectrum similar to that of the model.A number of experiments have been performed on the model to shift the tank resonance frequencies in an attempt to reduce their contribution to the leakage. In particular, by shorting out slots between selected seg­ments, the frequency has been success­fully shifted upward away from the fundamen­tal operating frequency without significantly changing the TM110 and TM21Q modes. As a result, the leakage excited at the operating frequency now situated in the large gap between the TM2i an^ ^ 3 1  m0<^ es reduced by 15 dB, corresponding to a reduction from ~2-3 kV to ~400 V in the main machine [Fig. 77(c)]. In parallel with the above effort a 3-dimensional relaxation code,CAV3D, is being modified for the TRIUMF geom­etry. In particular, the requirement of a cubic grid has been removed, allowing the integration step size to be varied indepen­dently in each dimension.Magnet and RF stabilityDuring the summer the Magnet/Power Supply group, in collaboration with Hans Baumann of SIN, were successful in substantially improv-DEEGAP2 L 72L7Fig. 80.tron RF system of resonances measured in the dee gaps. (Measured at resonator No. 7, lower second quadrant.)2 0 0 M H z 3 0 0 M H zMODEL  l: 10l : l2 0 M H z  3 0 M H zComparison between model and cyclo-T ( min )Fig. 81. Time variation of the cyclotron magnetic flux measured through an outer trim coil before and after the 1982 the stability of the main magnet power supply. Some ground loop and termination problems were identified and corrected; differential inputs on the new error ampli­fiers and master/slave amplifiers were in­stalled and proper temperature compensation was achieved. Possible sources for instabil­ities such as the crane movement and shunt water temperature variations were reviewed.A comparison of the magnetic field stability, before and after the modifications, is shown in Fig. 81. The stability of ±0.7 ppm required for separated turns was achieved for a period of half an hour. Other details about this important improvement are given in the report by the Magnet/Power Supply group (below).Slow drifts were compensated by measuring the field with an NMR probe and applying a cor­rection to the main power supply as described in the 1981 report. Work has continued to improve the NMR system. The lifetime of the existing NMR probe in the high radiation field has been significantly extended by replacing a bipolar transistor in the probe with a p-channel J-FET. Work is in progress to improve the sensitivity and band width of the original system designed at CERN. A digital programmable RF synthesizer source allows measurements of the NMR frequency and thus the B field to 1 part in 107 and still maintain a 10 Hz bandwidth. The feasibility of this method has been demonstrated on a test bench. A prototype is being designed for tests on the main cyclotron magnet.Additional instabilities in the beam phase resulting from magnetic field drifts were monitored with the capacitive phase probe in beam line 1 for extracted currents of several77microamperes. These phase drifts have been reduced by means of a feedback loop in which the RF frequency is adjusted to compensate for the phase drift. The resultant beam stability of ±0.7° observed for periods in excess of 1 h is a factor of 2 better than previously reported and meets the requirement for separated turns operation. Work is now proceeding to provide phase stability for beam currents at the few nanoampere level, using counter techniques. At the same time studies are in progress to improve the RF voltage stability, the next requirement for separated turn and stable high split ratio operation. For the spectral analysis of beam- and stability-related measurements, a dual channel FFT analyser has been ordered. This instrument will facilitate measurements of the correlations between beam and RF proper­ties. To this end, a biased programmable instrumentation amplifier has been developed to aid in the conditioning of these signals. This CAMAC module has a programmable preci­sion dc offset which may be subtracted from the input signal before amplification and digitization. The unit is now being tested.Data acquisitionThe amount of cyclotron data logged by the central control system increased substantial­ly during 1982. In addition to the logging of radiation and spill monitor data, the tank vacuum, RF voltage and frequency, ISIS and machine transmissions, and all of the tank thermocouple data are recorded in the log stream. A number of computer programs have been developed for the playback, storage and analysis of logged data.In order to increase the CPU power for on­line data analysis and tune fits, a VAX 11/730 computer has been ordered. A serial CAMAC highway for the VAX will run through the ISIS area, the central control room, the proton hall extension assembly area, and the CRM laboratory to facilitate developments and provide data acquisition, analysis and dis­play capabilities in these areas. The commu­nication system between the VAX and the cen­tral control system will be develoed in 1983 in conjunction with the Technology Division.Diagnostic developmentsDuring 1982 the 50 resistors in the inter­nal non-intercepting phase probes were re­placed with 10 Mfi resistors. The probe signal-to-noise ratio has been improved by tuning the probe transmission line to anintegral number of half wavelengths and terminating the line in a high impedance of 10 MJ2 rather than 50 fi. The resulting improved low frequency response will be use­ful for producing non-intercepting beam time- of-flight information. Measurements with the internal probes show that beam loading modu­lates the RF noise to the extent that it interferes with the internal phase measure­ment, particularly at high duty factors.Phase detection is possible at duty factors between 30% and 70%.The design and testing of a system to provide a 23 MHz signal phase locked either to beam signals from scintillators detecting scat­tered protons for low intensity beams or to discriminator pulses from the beam line 1 capacitive probe for higher current levels was completed in 1982. Two units were in­stalled as part of the RF separator electron­ics to lock the separator drive signal to the beam line 1 capacitive probe signal. In another application the 23 MHz signal, phase locked to scattered particle signals in beam line IB, was used to provide a measurement of the phase of the low intensity extracted beam.The mechanical components for the ISIS emit- tance apparatus were assembled and tested in the CRM laboratory. Current readout is done with a 16-wire harp which can be displaced by 1/2 wire spacing to provide the equivalent of a 32-wire readout. Movable beam-defining slits are placed upstream of the harp. The entire apparatus may be rotated about the beam axis to provide both vertical and hori­zontal emittance measurements. Software to control slit and harp movement and current readout has been written and is being commis­sioned on the CRM laboratory source. The apparatus is scheduled to be installed in the ISIS horizontal section in 1983.RF systemResonator replacement program GeneralThe major effort this year was focused on manufacturing a prototype resonator segment and building an electrical test facility to test the prototype. In consultation with the Department of Metallurgy at UBC a critical analysis of the new resonator system was performed with favourable results. The manu­facturing of the prototype resonator segment is well under way and is described below.78Prototype resonatorFabrication and assembly of the first proto­type resonator segment was in the final stages of completion at year-end after a lengthy program of manufacturing process, development and design improvements.Figure 82 shows an exploded isometric view of the prototype.The main structural component is the 'strong- back' assembly shown at the top with the 'tip' at the left side and 'root section' and 'levelling arms' at the right. The structure is 32 in. wide over a ten-foot length from the tip to the root section, where it narrows abruptly to the 15 in. wide levelling arm which continues on 33 in. to the levelling arm adjustment point at the right-hand end.In service, the strongback is supported across its width at the root section and at the levelling arm adjustment point to form a cantilevered beam which supports the hot arm panel. The panel shown below the strong- back forms one side of the resonator segment cavity. The other side of the cavity is formed by the existing ground arm panel shown at the bottom, and the right-hand end of theFig. 82. Exploded isometric assembly.cavity is closed by the root structure which also supports the strongback. The 'tip' of the hot arm panel is a removable assembly for adjustment and assembly purposes.Strongback assembly. The strongback struc­ture of the existing resonator segments is a welded assembly and has not been stress relieved. There is no water cooling and it does not directly support the last 30 in. of the hot arm panel at the tip. The new strongback assembly is comprised of two water-cooled aluminum I-beams that run the entire length from tip to levelling arm.Each assembly supports a water-cooled longi­tudinal outrigger member at the side through numerous transverse stainless steel supports. The structure is rivetted together following aircraft practice with an additional 1 in. thick aluminum plate forming the levelling arm proper and 0.080 in. thick aluminum cover plates top and bottom providing additional stiffness.A novel design feature is that the I-beams are stretchformed to a reverse curvature such that in its assembled state supporting the hot arm panel in the cantilever configuration the strongback assembly forms a level struc­ture, i.e. there is no droop due to the assembled mass.In the present program, stretchforming the I- beams was not a simple process because of their hard T6 condition and the difficulty of providing suitable end attachments to apply the stretchforming load. However, after numerous schemes were evaluated a suitable system was developed and beams were stretch- formed very satisfactorily.The curvature of the beams presented some problems in the assembly jig, and there were also problems associated with the welded con­nections of the numerous cooling water supply and return lines. Rivetting the structure together was also problematic - the rivet size and lack of access in places necessitated the use of aircraft style blind rivets instead of the conventional solid type. This in turn caused difficulties due to the limited selec­tion of blind rivet materials that are compatible with the vacuum and non-magnetic requirements of the cyclotron. Although the first prototype has been assembled, the final selection of rivet material is not yet resolved.Hot arm panel. The present hot arm panel is a roll bond panel made of two aluminum sheets79and one copper sheet. Cooling is provided by channels incorporated between the two alumi­num sheets. The new hot arm panel consists of a flat 1/32 in. thick copper sheet water cooled by a series of flattened stainless steel tubes soldered to one surface. The panel is fixed to the strongback by 29 float­ing supports (compared to 8 in the existing segments) which locate the panel but allow for thermal expansion in service.Both the forming and soldering of the stain­less steel tubes required substantial devel­opment to achieve good results. The forming of the thin-walled tubes was performed in a custom made tube bender to prevent tube wall buckling, and the flattening of the resulting tube was performed by first filling the tubes with water and freezing it to prevent tube wall damage during the flattening process. Numerous tests were performed to develop a satisfactory soldering process. The final system employs a silver/tin solder which is first preformed to suit the tube and then attached to it and the panel with a non- corrosive flux. The complete panel and tube assembly is then heated as a unit on a custom made 'hot table' to melt and form the solder joint.Root structure. The root structure serves two functions: it supports the strongback and also houses the root tuning device. This device consists of a movable flat foil which forms the closed end of the RF cavity. In the existing resonator root structure the root tuning foils are not water cooled. They failed after the first year of operation and were replaced by fixed panels. A prototype of a new tuning device with water-cooled movable foils has been operating in a cyclic test rig for a simulated 15-year lifetime to date under no-power conditions.The completed prototype resonator is now scheduled to undergo a series of mechanical tests prior to RF testing in the large vacuum tank facility. In this regard a dual channel FFT analyser will be used to measure the dynamic mechanical properties of the proto­type resonator for comparison with the oper­ating resonators. A stress analysis will also be performed in consultation with outside experts.Test facilityThe RF power amplifier which is capable of 25 kW was successfully tested into a load by HN Engineering. This will enable the appli­cation of full operating voltage in vacuum on a system consisting of the new prototype and one old resonator segment, separated by a distance corresponding to the cyclotron beam gap and electrically coupled through side flux guides. The vacuum tank has been pumped down to pressure of 2 * 10“ 6 Torr with an external LN2 cryopump, but plans are now proceeding to install a cryopanel in the main body of the vacuum tank in order to improve the vacuum to pressures in the 10“ 7 Torr range.1:10 modelA 1:10 scale aluminum model of the entire vacuum tank and resonator was constructed in order to further understand the RF leakage problem. Extensive tests have been carried out with very encouraging results. These have been discussed in the Cyclotron Development report above.Operational performancePresent resonatorsAlthough the RF resonators were found to be in different positions, following shutdowns, one could in general compensate for hot arm misalignments with ground arm tip adjust­ments .In the fall shutdown approximately one-third of the resonators were modified as follows:• The resonator hot arm tips were changed from aluminum to copper.• The resonator hot arm tip supports were changed from aluminum to stainless steel.• The 10 Hz dampers were removed since this frequency was not contributing to the measured voltage instability.• The 4 Hz dampers were reinstalled at the centre of the resonator in order to allow for the installation of new stainless steel tip supports. They were also shielded from the RF by a stainless steel casing.It is planned to modify the remaining reso­nators in the early 1983 shutdown.RF amplifier systemThe RF amplifier system was the source of most of the RF downtime. The first major problem began when a water-cooled surge- suppressing resistor in the dc power supply failed causing steam pockets to form and80build up pressure inside the water-cooling jackets, eventually rupturing them. After two such failures the resistor was replaced by a ribbon-type air-cooled resistor.The combination of a transmission line capacitor failure, and the failure of the crowbar protect system caused high-voltage discharges to puncture a hole in a copper cooling line that feeds the plates of one of the power amplifiers. To further add to the problem the replaced driver tube was inter­mittently breaking down from plate to cathode causing the crowbar system to fire falsely.The transmission line capacitor subsequently failed again and a transmission line elbow, badly damaged due to a slow water leak in that area, was replaced. Indications were that sparking had been occurring in that area for some time and could very well have caused the failure of the transmission line capacitor.On another occasion the intermittent failure of a vacuum capacitor in the intermediate power amplifier (IPA) caused many hours of machine downtime before the problem could be properly diagnosed.With the help of HN Engineering a reliability program was started on the RF amplifiers.The first area worked on was the lower power stages including the IPA. The 25 W tuned transistor stage was replaced by a commercial 25 W broadband amplifier and a new matching network installed. Parasitic suppression in the input circuit of the IPA was improved and the output circuit tuned for better loading.A new RF choke was installed in the B+ line of the IPA power supply which eliminated the RF heating problem in that compartment. The IPA stage is now operating with 20% less plate current for the same available drive power for the power amplifiers.The power amplifiers have had a history of crowbars and parasitic oscillations, some­times melting spark gaps and puncturing by­pass capacitors. Parasitic suppression in the input circuit was improved and the ampli­fiers were changed from Class C to Class B operation to reduce the stresses on the com­ponents and load down any instabilities in the RF system. The reliability of operation has greatly improved since this change and no external crowbars or oscillations have been experienced since this modification.Probes and diagnosticsThis year has seen relatively trouble-free operation of probes and diagnostics systems with only one extraction probe 1 problem causing any significant machine downtime. Efforts are continuing to improve the relia­bility of the slit and tank mechanisms in the tank, and a major improvement in the cyclo­tron internal viewing and lighting system has been achieved. The design and construction of a prototype BL2C stripper mechanism was completed and is presently under evaluation.Numerous replacement beam line monitors have been built and installed and several newly designed secondary emission monitors (SEM) have been built and tested successfully.Various improvements have been made to the signal processing, display and distribution systems, but not all of the electronics development work that was planned has been accomplished. A new electronics engineer was hired towards year-end, and this should greatly improve the situation.In more detail, the extraction probe 1 prob­lem was the breakage of a beryllium copper drive tape on the probe head during a period of 140 pA running. It was not established whether the problem was due to direct beam damage, indirect beam-related heating or RF- induced heating. Several small design changes were implemented and the problem has not recurred.The plain bearings in slits 3,4 and the ver­tical flag mechanisms - approximately 80 in number - were replaced with either beryllium copper or 300 series stainless steel ball bearings. This should alleviate the problem of bearing seizure that has been experienced often in the past. It is proposed to simi­larly replace the plain bearings in slit mechanisms 1 and 2 in early 1983.Following the successful tests last year of the in-tank periscope lighting, the design and fabrication of an operational unit was completed and it was installed in October of this year. To date, it has not failed in the tank environment, and its use has approxi­mately halved the time and dose required for tank viewing operations, particularly the resonator alignment surveys.The design of the new beam line 2C stripping foil mechanism for extracting beam between 70 and 110 MeV has posed some problems because81the required stripping foil locus lies between resonator levelling arms directly under a main magnet pole piece. This pre­cludes direct vertical access through a port and thus the proposed design utilizes a curved track and cable drive to position the stripping foil. The concept is promising in its present prototype form and a decision should be made shortly to proceed with a cyclotron-compatible unit.Conceptual design and testing of some key components of a new low energy probe less ex­posed to RF interference has been completed and detail design work is scheduled to commence shortly.In beam line monitor activities a new vacuum housing with thin stainless steel end windows was designed and built for the BL1B total current SEM. The design adhered to high vacuum practice in order that a vacuum of approximately 10“ 8 Torr could be maintained. The monitor has operated without problem and with low signal noise, and it is planned to replace the two SEM's in BL4A and 4B with the new design.A small SEM was designed and built to replace the Cerenkov monitor at the 1AT2 target. The new monitor will be positioned adjacent to the target on the profile monitor housing and should be relatively maintenance free as compared to the Cerenkov monitor, which required replacement at four-month intervals due to radiation damage.A beam halo detection plate has been added to the 1AT2 target protect monitor and the signal interlocked to the cyclotron system to prevent damage to the beam line due to mis-steered beam.A pair of split plate SEM's was installed in both BL4A and BL4B as part of automatic beam steering systems used by experimenters for optimal beam alignment. The units in BL4A operate in beam line vacuum, whilst the BL4B units operate in a variable pressure argon gas fill within 0.002 in. thick aluminum windows to increase their response for low beam currents of the order of 50 pA.VacuumThe vacuum system operated normally this year with minimal downtime. The welding of the combination magnet box on the exit horn four (reported in the beam line section) elimina­ted the leak in that area. This resulted ina new record base pressure of ~1.0xl0-8 Torr, with the beam off, and permitted pressures of 5x10“ 8 Torr at 100 yA extracted current (4x10“ 8 Torr with RF on only).The calibrated leak line in quadrant 1 was split to provide a second inlet into quadrant 4. This will remove the effects of the beam gap conductance in pumping speed measurements. These measurements will be enhanced with the commissioning of a new quadrupole mass spec­trometer which has been purchased and in­stalled. Orders were placed for two new dif­fusion pumps and cold traps to replace faulty existing equipment. A diffusion pump system not requiring LN2 cooling is being considered.ION SOURCES AND INJECTION SYSTEMThere has been a great deal of activity within the ISIS section this year. The pre­dicted inevitable oil contamination in the vertical section occurred, but was removed much quicker than believed possible. Source developments have permitted continuous opera­tion from one maintenance period to the next without filament changes, even at the" higher currents. It has long been realized that in order to achieve long-term reliability it would be necessary to build a third ion source terminal. Work was begun and completed on the building design, the high voltage terminal, and the electrical distri­bution systems design. An ECR source was built and tested on a polarized source with the help of Dr. T. Clegg from the University of North Carolina and Dr. V. Bechtold from KFK in West Germany.High intensity source and injection lineOperationThe work in ISIS has concentrated on increas­ing the overall reliability of the system.The major activities in addition to the regular maintenance are outlined below.A comprehensive interlock system based on DIC0NS (a CAMAC-based interlock controller) was installed in the 300 kV terminal of the high intensity ion source (II) in January.The system was commissioned and has continued to operate with very few problems. A new 300 kV power supply, purchased as a replace­ment, was tested and put into operation earlier than expected because of problems with beam stability. Precision high voltage probes to measure voltage deviations in the82order of lO-4 are under construction. Flow switches, an essential item in the ISIS interlock system, have been unreliable in the past. The most critical switches have been replaced during the year and the remainder will be during upcoming shutdowns.The 12 kV optics box was cleaned and modified to reduce the problems with high voltage sparking. The slit which acts as a beam stop for the pulsed beam was water cooled. As a result, not only has the sparking been reduced but the offset current on the Faraday cup and the beam-loading on a number of power supplies have also been reduced.As the result of modifications to the sources, there are now four ion sources (proper) which are capable of providing a 100 yA extracted current with minimal adjustment to only two of the II parameters, namely the magnet and the puller position. This has resulted in much shorter times to again reach 100 yA after a source change.In the injection line additional steering capability has been introduced into the east- west section of II. The cyclotron fringe field had not been adequately shielded in this region. The effect on the beam transmis­sion remains to be tested. Also, as the result of calculations and operational beam experience, more powerful RF amplifiers were installed on the bunchers. The immediate consequence was a ~10% increase in beam transmission (from ~54% to ~59%) through the cyclotron.Measurements during the last week in December have shown that a collimator (1.3 cm aper­ture) located at the centre of the vertical bend is limiting the high peak current. The vertical beam size is larger than 1.3 cm in this region as a result of the higher buncher voltage (consequently higher energy spread) required to compensate for the effects of space charge at the higher beam currents. A wider collimator will be installed in this position prior to the next high intensity production period.The year was not without problems. A water leak in the II terminal led to arcing and to damage of power supplies. A failure in the interlock system resulted in a breakdown of the filament power supply. Faulty mainten­ance procedures to the roughing system led to a serious oil contamination of the vertical injection beam line. Fortunately the oil could be removed by repeated flushing with freon without removing the vertical beamline. The roughing system has now been modi­fied to prevent a reoccurrence in the future.DevelopmentsThe drawings for a building extension to house a third ion source have been completed and the project is ready to go for tender.The design for a 100 kVA-300 kV-3 phase isolation transformer has been completed and is being manufactured in Vancouver. The ex­tension will be located to the south of the existing terminals and will allow the third source to be connected into the north-south section of the injection line without the need of a bend.As a consequence of results from the test source in the CRM a modified puller was de­signed, built and installed in the II termi­nal. A record of 1.09 mA was achieved within the acceptance of the slits defining the high intensity beam. Measurements have been car­ried out to optimize a number of other source parameters, such as source slit size and position, the gas flow and vacuum require­ments, extraction potential, and filament lifetime. Further improvements are required in order to meet the demands of the antici­pated higher extracted current operation.POLISISThe operation of the polarized ion source has in general not been up to expectations. The polarization has been good (75 to 80%) but the current much lower than normal. A great deal of time and effort has been devoted to trying to understand the problems. Renewing the filament coating compound gave a large in­crease in current. Careful alignment of the extraction electrodes also gave improvements.The RF spin filter, rapid spin reversal coils and electronics have been installed and tested. The computer software to operate this new system is also complete. The system is ready to be commissioned as soon as develop­ment time can be scheduled. It is expected that the polarized beam transmission will in­crease along the injection line and in the cy­clotron since the beam should no longer shift in position when changing the spin direction.Intense polarized ion sourceA number of developments have proceeded in parallel towards an intense polarized ion source. A small electron-cyclotron-resonance (ECR) proton source was designed, built and83tested. An experiment to measure the polari­zation of optically pumped sodium is being set up.The ECR source was designed to be a replace­ment for the duoplasmatron in the existing Lamb-shift source. It was assembled on a test bench together with extraction elec­trodes, cesium and argon charge exchange canals. Measurements were made of the plasma density inside the source, the extracted current density and the polarized H“ current density. The plasma density was about 10% of that expected. This is believed to be due to the small plasma chamber which has the same diameter as the microwave transmission line.The extracted current was about 30% of that expected from the measured plasma density.This is due to the non-optimized extraction electrode geometry, originally designed for the duoplasmatron. Nevertheless, the polar­ized H~ density was approximately equal to that of the cyclotron Lamb-shift source. It is felt that this source, if installed in the high voltage terminal, could already provide a current comparable to the existing source with greater reliability.A second, larger ECR source, which overcomes the limitations of the first source, has been designed. An extraction system suited to the ECR plasma geometry is also in the design stage. Plans call for the system to be ready for tests early in 1983.There has been parallel progress on the opti­cally pumped source. The pump laser, dye- laser, solenoid and sodium oven are now oper­ating. Initial difficulties, experienced in realizing the required light intensity, were finally overcome with a third argon tube. The sodium cell had to be repaired after water came into contact with the sodium. The sys­tem has been reassembled and is now ready for measurements on the sodium polarization. Com­munication regarding results obtained at KEK in Japan suggests that this type of polarized source will indeed yield the substantial polarized H- currents that are expected.PRIMARY BEAM LINESDuring the past year one aim of the Beam Lines group has been to increase the relia­bility of the primary beam line components and their compatibility with high current operation. Towards this goal a number of beam line components have been made radiationhard and access to components via remote handling has been improved. This will significantly reduce the personnel radiation dose during maintenance.Beam line 4During January the vault section of beam line 4 was upgraded between the exit of the combination magnet (4CM1) and the entrance of the first dipole (4VB1). Rubber seals were replaced with indium ones and all com­ponents are now remotely handleable. In addition, a retractable 1 mm collimator (for use in experiments on beam line 4B) was installed upstream of 4VB1.In the past the vacuum seal between the cyclotron exit horn and the combination mag­net vacuum chamber has been a continual source of leaks. Thus, replacement of the vacuum chamber of the combination magnet was a major undertaking in the September shut­down. The new chamber was welded to the cyclotron exit horn. At the same time the combination magnet support stand was replaced with one which allows the magnet to be split and rolled away from the cyclotron. This improvement, intended to allow ease of coil replacement, was baptized shortly after in­stallation when it was found that the upper magnet coil was overheating. The magnet was removed and another cooling layer added. The magnet gap was reduced by 1/8 in. Disassem­bly and reassembly of the magnet proceeded smoothly because of the new stand.Beam line 1Access to components between the thin and thick targets (1AT1 and 1AT2) on beam line 1A has been difficult because of residual radiation in the area. The problem was alleviated in January with the installation of a shielding wall along the beam line within the existing tunnel. Servicing of components in this section is now possible in residual fields of 5-10 mrem.During July the quadrupole doublet 1AQ12/13 upstream of target 1AT2 was replaced with a pair of radiation-hard quadrupoles, capable of being handled remotely. Vacuum couplings in the section of line between these quadru­poles and the 1AT2 target shield were up­graded with metal seals. New rate-meter flow switches were installed on all five quadru­poles between 1AT1 and 1AT2. These meters have proven more reliable and provide a visual indication of coolant flow.84One of the quadrupoles (1AQ10) between 1AT1 and 1AT2 has given problems because of a faulty cooling circuit. Blockage could be cleared by backflushing with a weak HC1 solu­tion - a procedure which took some time. A "portable" self-contained flushing system using the copper cleachant used at LAMPF has been constructed. The new flushing system is adaptable to any water-cooled magnet on site. It also significantly reduces the time and personnel dose required for the operation.Improvement in the vault section of beam line 1 was in the form of a new stand for the quadrupole triplet which lies between the dipole and the vault wall. The new stand allows the triplet to be slid sideways out of the beam line, for faster and easier access.Beam line operationIn general, throughout the year beam line operation ran smoothly. Except for the changing of Mil from tt+ to it- operation (which involves reversing the polarities of the quadrupoles between 1AT1 and 1AT2) and a few other special cases, most tunes were set up and easily reproduced by the operators.Some of the existing diagnostic devices were upgraded and some new ones built for easier tuning, equipment protection and special experimental requirements (see the report from the Probes and Diagnostics group in the Cyclotron section).Normal high intensity operation of beam line 1A was at the 120 pA level. The most used target at 1AT1 was the 10 mm cooled carbon target; that at 1AT2 was the 10 cm Be.Currents of 100 nA and 1 pA were extracted down beam lines 4B and 4A, respectively. Oper­ation on these lines was sometimes difficult at currents of a nanoampere of less since extracted beam split ratios of 1:105 are difficult to establish in a stable mode.Thermal neutron facility (TNF)OperationThe thermal neutron facility has operated as in the previous three years with a minimum of downtime, as befits a passive component that does little but transfer heat. Yet there are signs of deterioration, and the replacement of the complete moderator/target assembly, scheduled for January 1983, is timely indeed. The lead target (112) presently in the facility has been exposed to approximately330 mAh of beam, and the water window (111), which separates the TNF tank vacuum from the moderator tank water, to approximately 380 mAh. The target and the water window are therefore the two most heavily irradiated components at TRIUMF. Their inspection for radiation damage, which is planned to be done at CRNL some time in 1983, may reveal interesting results.Deterioration in the vacuum of the TNF tank and in the flow of cooling water between water window and target has been noticeable for close to two years. Radiation damage to the water window could have caused the poor vacuum. The decrease in coolant flow is probably due to leakage at the spring-loaded seal between the water window and the target. Neither of these deteriorations were suffi­cient to cause unsafe operation.As reported in last year's annual report, problems continued with the -100°C refriger­ator which cools the mercury trap. It was discovered, however, that the periodic warm­ups almost always cleared themselves without operator intervention before the temperature rose above -70°C.Mark II targetDuring 1982 all of the components for the new high-current target/moderator assembly designed in 1981 were produced, tested and assembled. They are ready for installation in January 1983 (Fig. 83). The main compon­ents which will be replaced are the moderator tank with its entire contents consisting of the target, shadow shield, rotirad and mis­cellaneous NAA rabbits. A redesigned target incorporating a water jacket to improve the cooling has been fitted with 24 thermocouples to monitor temperature gradients in the molten lead (Fig. 84).The cooling package has been redesigned to include a more powerful pump and a no-break cooling system. The latter is necessary to protect the target from over-heating. This could cause a possible vapour explosion in case of a power failure during high beam current operation. It consists primarily of a storage tank located under the meson hall roof that provides 30 s of cooling after the circulation pump stops.The new equipment will upgrade the TNF beam power capability from 50 kW to 150 kW. This means it will be able to accept 300 pA of 500 MeV beam with no other targets in beam85Fig. 83. The new moderator tank ready for installation in the TNF. The lead target and water jacket are shown at left. The aluminum water window, behind which the target will be located, is visible near the bottom of the tank as is one of the experimental neutron channels.line 1A. With the usual targets at 1AT1,1AT2 and the 500 MeV irradiation facility, beam line 1A beam current could be increased to 400 pA. Analysis of lead temperature data during commissioning may allow further up­grading of the target's beam power capability.Side benefits of the upgrading program are a new improved "rotirad" and more and wider irradiation tubes for neutron activation analysis. There are also some changes to the neutron channels used for neutron spectros­copy. The mercury trap assembly has been redesigned so that it may be removed without dismantling the 500 MeV irradiation facility hot cell. This is to enable once-a-year retrieval of the trap for transfer to AECL, who have expressed an interest in recovering 1 ^ Au, the decay product of ^^Hg.The redesign of the mercury trap assembly also allows future replacement of the refrig­erator, which should eliminate future prob­lems in case of refrigerator failure. Some shielding will be added to hopefully reduce the neutron flux above the cave. The shield­ing will also be made easier to seal for air leaks to alleviate air activation.LicenceThe present TRIUMF licence to operate requires changing the present target #2 after 350 mAh exposure or up to December 31, 1982, whichever comes first. With the above quoted exposure of 330 mAh we have come very close to this limit.The TNF Safety Report has been revised to include the redesign and has been approved by TSAC for submission to AECB.CONTROL SYSTEMFor the most part 1982 has been a year of minor improvements to existing systems and small steps towards long-range goals. The major achievement of the year was the final installation of the new multiport memory with six computer ports. This, as well as the movement of the magnetic tape unit from the console computer (CN) to the "TTY" computer, allows a large amount of program development while the control system continues to run.Because faster logging was required for oper­ations a faster printer was installed in the control system. In addition the success of a test using the 300 £pm impact printer in the terminal room has led to ordering a quality fast printer. To satisfy the requirement of improved information to the experimenters the most important machine parameters and an up­dated status-message page are now distributed to the experimental shacks using a new video86Fig. 84. The target/waterjacket shown assembled (left) and shown separated (right). The thick aluminum pipes carry the cooling water to the jacket. The thin stainless steel tubes connect the target to a vacuum pump and carry the 24 thermocouple leads.information distribution system. Also a terminal has been installed in ISIS for con­venient display and control.There has been considerable progress in the effort to move the video terminal software out of the console computer (CN) and into the display processor (Dl). When the terminal software is completely moved the main console software will be consolidated in CN and thus multiprocessor communication will be reduced. More channels have been added for chart re­cording, both in ISIS and in the control room.There have been some additions to the soft­ware interlock system. There are new trans­mission interlocks using the beam current information in beam line 1 at 1AT1, 1AT2 and TNF. As a back-up to the tank spill inter­lock a scan was added on the new low energy spill thermocouple. There is now software protection against confusion in the control of switchable power supplies in beam line IB and the secondary beam lines - now these power supplies can be controlled only when the appropriate beam line is switched on.There have been a number of improvements in controls hardware. The analogue multiplexing system to read the trim and harmonic coils failed and was replaced by a commercial sys­tem. The replacement necessitated modifica­tion of the power supplies by the Operations and Magnet groups. There are displayable power monitors in almost all control system crates. A program to modify interlock fan­out units to eliminate oscillating bits and resultant garbage scan messages has begun.The 1AT1 and 1AT2 units have been retro­fitted; the others will be changed in the next shutdown. Because of a persistent problem with data transmission from the ion sources the optical part of the serial link used to communicate with the devices in the ion sources was redesigned. The final ver­sion has been installed in both ion sources.A number of terminals have been added to the development computers - a second terminal has been added to both the programming system and TTY (the controls development system), and a third terminal, for use with AOS (described later), has been added to HLL (the high level language system).The spin flipper program has been greatly augmented to make it possible to use the capabilities of the new spin flipper control­ler, described elsewhere in this report. A microprocessor-based program to control Bertan power supplies has made possible a feasibility study of the application of Bertan power supplies in ISIS.The demands on the HLL and TTY computers have made the present operating system (RDOS) in­adequate. A new operating system, AOS (advanced operating system), will allow more terminals on the HLL computer. The new system has been acquired and is almost ready for permanent installation. Developments on HLL have included fast logging of RF probe signals to allow RF analysis, analysis of data logged by the central system, and main magnet stability recording. Developments on TTY have included a FORTRAN version of the $FIND command (to identify CAMAC addresses of cyclotron devices) and improved hardware de­bugging programs.87The beam line 2C control system has developed a great deal. A number of problems in both the hardware and the software of the commer­cially supplied CAMAC interface have been solved. A system of pages displays and con­trols the beam line. At present there are pages for the monitors and vacuum system, and work has begun on the target pages. The cen­tral system is sending data via a CAMAC-CAMAC link to the beam line 2C (PDP 11) system. Other aspects of the communication remain to be developed. An interface to the central safety system is ready for installation.In the secondary beam line control system the slit control program (SLICON) has been modi­fied to include M20. The M20 beam blocker controller has been installed. A second set of slits was integrated into the M9 system.ReliabilityThe control system has been significantly more reliable during 1982 than it was during1981. In 1981 the control system caused101 h of cyclotron downtime, or 10.3% of the total; in 1982 the control system caused 73 h of downtime, or 7.9% of the total. The major single contributor to control system unrelia­bility during 1981 was the multiport memory which has been completely replaced. The major contributors to controls system down­time during 1982 were the RF thermocouple system, the chargers for the no-break power system, and a problem of set points changing erratically. A new system for the RF thermo­couples is planned, and the set point problem was solved early in the year.A rather interesting problem turned up during1982. Data in the multiport memory was occa­sionally being destroyed by a fundamental fault in the design of our twelve-year-old computers. The problem in the computers was fixed by the replacement of a chip inside each of them. Since the repair the frequency of computer crashes has declined significant­ly. Probably many mysterious intermittent problems of the past were due to this fault.Space and time limitations in the central control system, specifically space in the "CY" computer and time in the remote console control computer, are making the need for expansion critical.OPERATIONAL SERVICESThe year saw a continual increase in demand for operational services. The year therefore was not only one of operating and maintaining equipment but also saw the expansion of many systems, as outlined in the following sec­tions. Of particular note is the setting of a new hydro peak demand of 8010 kW in August.A major achievement was a substantial increase in main magnet stability as outlined in the Magnets & Power Supplies section. A new Remote Handling building was occupied at the end of the year and its function described in the section on Remote Handling.OperationsA change in operations announced in 1981 saw the innovation of two operations co-ordinator positions. The typical functions covered by these two co-ordinators evolved during the year and the new roles proved to be extremely important for smooth and reliable operation.The two co-ordinators are appointed from the most senior shift supervisors and are alter­natively on duty seven days a week overlap­ping partially the three rotating daily shifts. Duties include monitoring the repro­ducibility of beam tunes, the performance of various co-ordination tasks and maintaining prompt communications between shift super­visors, group leaders responsible for systems, experimenters and the engineer responsible for operations. A review of the daily functions of the cyclotron is performed and fault reports are being reviewed to ascertain that the repair work is being done.A critical analysis of the frequency of the faults is used to point out priority of action for system improvements. A complete record of all faults is recorded and tabu­lated and given to the groups.Figure 35 shows the total downtime charged to the various groups in 1982.PlantThe year saw all equipment operating with no catastrophic breakdowns or failures. Various systems were extended to serve an ever- increasing workload and some new installations were made. An air-conditioning system was in­stalled to serve the service annex power sup­ply floor and RF room. These areas were very hot and equipment failures occurred constant­ly. This installation was a very positive200UJ22  160 SoQu. 120 oCOJ  8 04 0240Fig. 85. 1982 total hours of downtime tocyclotron and beamlines by systems.step in improving reliability of the equip­ment in these areas. In the chemistry annex an expansion tank was installed to improve the compressor duty cycle for the CP42 cooling system.On the main cooling systems:1) A new pump, surge tank and increased diam­eter pipe were installed on the meson hall system. This was made necessary by the continuous increase in load in this area.2) A filter was installed on the raw water system to decrease the silt clogging the heat exchangers.3) A complete analysis of all cooling systems was done and pressure-temperature sensing devices are being installed in the most crit­ical points, with corresponding monitoring and trip alarm setting in the control room.The compressed air system was extended and a second compressor added. Each compressor operates separately with an automatic switch­over should one compressor fail.The month of August saw TRIUMF establish a new peak demand for electricity of 8010 kW. August also saw a record consumption of5,137,000 kWh.Vacuum— Liquid He and N2Several new pumps were acquired and installed and a continual effort was required to keep136CO CO HV) <f) £-J oo <52 5010the systems at the proper levels. Various leaks were repaired which resulted in improved vacuum levels especially in the cyclotron tank, the results of which appear in the report of the cyclotron section.A total of 28,100 I  of LHe was delivered this year, an increase of 15% over last year. The liquefier has accumulated a total of 9450 h running. There were a number of minor failures during the year but there was no major interruption of supply; virtually all requests were met. Four major capital pur­chases were made to increase the efficiency and flexibility of the system: (1) three newlightweight 100 i  dewars to improve distri­bution, (2) a new recovery compressor of higher capacity and reliability, (3) a repuri­fied helium storage tank and (4) a small forklift dedicated to the helium building.The LN2 consumption for the year totalled600,000 £.. Different pumping systems are being evaluated for the cyclotron and other systems in order to assess the possibility of not using liquid N 2 traps and therefore sub­stantially reducing the N 2 consumption and associated cost.Magnets and power suppliesIn January trim coil 0 developed a water leak and a short to ground. A week of very hard work was required to redesign and install a new coil. All the trim coil and harmonic coil power supplies had new MUX amplifiers installed to give 5 V full scale. A switch was installed to switch three power supplies from the harmonic coil set 10 through set 13 for providing either Bz or Br corrections to the main field. To compensate for asymme­tries in the magnet steel, three more power supplies were added to the switch to power the top and bottom coils individually.In the fall a strong effort was made to improve the main magnet stability. The following modifications were introduced:1) Installation of a differential amplifier to isolate the error amplifier from the master/slave amplifiers.2) The shunt is now in parallel with the capacitor bank, so that resonant circuit currents between the magnet inductance and the capacitor bank are picked up by the shunt. The bandwidth of the current ampli­fier has been increased to ~2.3 Hz. The bandwidth of the voltage amplifier is~2.5 kHz.3) The temperature compensation circuit was changed. A new take-off point was selected89and a new compensation resistor (~2.7 kf2) was installed. The sensitivity to shunt cooling water temperature was decreased from 6 ppm/0.2° to <3 ppm/6°.The results were very encouraging with ±0.7 ppm high-frequency noise and 2-3 ppm drift over an eight-hour period achieved (see Fig. 81 in the Cyclotron Development section, p. 77).Several power supplies were installed or up­graded to satisfy different experimental requirements. Experiment 185 had two 60 kW Alphas and two 300 kW supplies connected to its solenoid. The fifth Brentford power supply was upgraded and installed on a new wooden mezzanine in the proton area extension along with the 300 kW UCLA supply for the charge symmetry experiment. Two 25 kW CTS supplies and the CDC spectrometer supply were connected to the QQD spectrometer and the stability on the M13 power supplies was veri­fied for the ir-scattering experiment. Two sextupoles were also installed on M13. Vari­able shunts were installed across quadrupoles Q3, Q4 and Q6 of the M20 Chicago quadrupole string. This doubled the surface muon flux through the line. All the new supplies for the M20 extension are installed except for the B1 and B2 power supplies, which are being constructed outside and the Q4-5-6 supply which is a Brentford power supply being rebuilt at TRIUMF. Two new 60 kW Alphas were installed to power the new radiation-hard 1AQ12 and 13 quadrupoles installed in beam line 1.Remote handlingThe summer and fall shutdowns required routine shadow shield installation. An upper resonator was replaced and the adjacent reso­nator relatched during the fall shutdown.The new lift trolley has been fabricated and all major parts ordered. Assembly will begin in the new year. The new service bridge carrier has been designed and is being fabri­cated. This carrier and the lift trolley, in conjunction with a new design of shadow shields, will reduce the shield installation/ removal times by a factor of three. A flat- deck rail car has been built to transport equipment of up to 7.5 tons through the vault tunnel.The tool trolley was rewired to operate with either the new microprocessor or existingrelay-logic control systems. This trolley was also fitted with an improved tool head to allow continuous or incremental bi-directional tool drive, complete with remote torque sensing feedback. The control system software for the operation of the tool trolley has been completed.The Mil septum magnet was removed from ser­vice and repaired in the warm cell. The active 4VE1 vacuum box was machined in the R/H "hot shop". Assistance was given with the installation of new 1AQ12 and 13 magnets and the removal of the 4A cesium production target. The target handling flask was modi­fied to optimize its shielding. A second target flask is being fabricated, and Remote Handling has taken over management of the "storage" holes in the TNF vicinity. A new 4 in. diameter "thru-pass" indium sealing flange assembly was designed and commissioned for beam line use.The renovated warm cell is nearing completion with improved size and handling capabilities, as well as greater flexibility for "hands-on" servicing of components. Routine replacement of target cassettes and bellows is continuing in the hot cell.The Remote Handling group has taken responsi­bility for on-site mechanical assembly and servicing of the 1AT1/1AT2 targets. Work has started with the assembly of the first of two spare targets.The new remote handling building allows direct access to the vault. The service bridge will be stored, and therefore always available for testing and updating, on the lower floor. The service bridge carrier can be "parked" out of the way so that any item which can be handled by the vault crane (7.5 tons) can be transported in or out of the vault without requiring special equip­ment. There is also 400 ft2 of vault equip­ment set-up space on the 264 level, available for other groups to use. The middle floor houses the electronic assembly and test area, and includes a partial tank mock-up. The remote control centre is also housed on this floor, complete with programmable controls and viewing monitors, and it is from here that most routine remote tank operations will eventually be performed. The top floor houses the "hot" machining and welding, mechanical assembly and test area, and cyclo­tron trolley storage. Some office space is provided in a two-floor adjacent building.90The building is now completed and occupied. Set-up of equipment and organization of work space is in progress and secondary services (shop-air, equipment wiring, etc.) are being connected. Construction of the new full-scale partial tank mock-up has started. The hot shop relocation from the meson hall is complete. Work has begun on the 150-ton biological shield door required at the en­trance to the cyclotron vault access tunnel.91E X PE R IM E N TA L FACILITIES D IV IS IO NDuring 1982 the increased level of beam oper­ation resulted in a corresponding increase of activity in the experimental areas.Several large experimental set-ups were in­stalled, some more than once, a number of new facilities were commissioned and progress made on future installations.Three major projects were completed in fiscal 81/82, the M9 intense muon channel, the RF separator and the Mil fast pion channel.With the successful commissioning and opera­tion of the RF separator the project to increase the muon flux on the M9 channel was completed. The design aim of 10® P~/s at 77 MeV/c and 100 pA proton current with low pion and electron contamination was achieved. This facility is used exclusively for the TPC experiment at present.Although the first commissioning of the Mil channel occurred in June 1981 the project did not officially end until this year. The channel still does not meet the design aims in terms of momentum resolution and beam size due to second- and higher-order aberrations which cannot be completely compensated for with the present sextupole locations. How­ever, the flux is as calculated and the chan­nel has been adequate for several experiments and was used for initial commissioning of the QQD spectrometer. The second annual failure of the Mil septum magnet occurred in March, but the repair was straightforward and possi­bly future shorts of this type were elimin­ated. The spare septum is well under way towards completion. Optics calculations have shown that a relatively minor rearrangement of components in Mil could improve the beam performance.The major projects in facility development and experimental support in the division are listed in Table VIII. Three major projects are scheduled for completion this fiscal year. The M20 channel redesign described in the 1979 and 1980 annual reports was given priority last year and now exists as hardware ready for installation in the January 1983 shutdown. The new layout of this channel and experimental areas is shown in Fig. 94 (see p. 101). The anticipated factor 6 improvement in beam luminosity should be available early next summer. Similarly the MRS upgrade program, which includes a 6-quadrupole beam twister on beam line 4B, to dispersion match the incident beam energy spread to thespectrometer, a new scattering chamber to reduce multiple scattering and improved focal plane detectors, is now available as hardware. The twister assembly shown in Fig. 97 (p. 108) is being prepared for installation in February. It is expected that these improve­ments will result in a spectrometer energy resolution of 70 keV.The other major project to be completed this year is beam line 2C, the 70-100 MeV high current facility located in the cyclotron vault. Most of the installation was com­pleted last year and low current beams have been used for commissioning. Much of the work this year involved completion of the control system and development of targets.The TRIM trailer, which has been located for several years above the 4A beam dump and used for 123I production there, was moved to the south berm of the meson hall in anticipation of future isotope production with the beam line 2C facility.Progress on the major projects is only part of the effort of the division. Support has been given to several major experimental installations during the year. Considerable effort has gone into the completion of the QQD low energy pion spectrometer and improve­ments to the M13 channel to fully utilize this spectrometer. Two sextupoles were added to the M13 channel and both dipoles of the channel were realigned to reduce steering effects.The large Sagane magnet and a solenoid magnet built at Berkeley were installed twice in M13 for Expt. 185. A short dc separator was fabricated and installed on M20 for several experiments. This separator, designed for surface muon beams, provided good separation between the muons and positrons.In the proton hall the final experimental run of the BASQUE group in beam line 4C was com­pleted, ending an eight-year experimental program. During the June shutdown beam line 4C was dismantled and the resurrection of the neutron area for the charge symmetry breaking experiment started. A large spin precession dipole was fabricated for this experiment and installed at this time along with the previously used spin precession magnet.A proton beam of 1 pA has been run on the improved liquid deuterium target on BL4A and92Table VIII. Experimental Facility Division - Major ProjectsProject titleThousands of 1982-83 dollarsPastExpend1982-83 1983-84 1984-85 1985-86 1986-87 1987-88 TotalCostFACILITY DEVELOPMENTM20 improvements 476 558 Completed 1,034Beam line 2C 728 221 Completed 949MRS upgrade 135 287 Completed 422Second arm spectrometer 198 200 514 235 Completed 1,147M15 muon channel ---- ---- 540 590 200 Completed 1,330Detector facility ---- ---- 200 150 150 Completed 500MRS upgrade II ---- ---- 150 150 Completed 300Beam line 2A-front end 207 58 (50) (50) (400) (300) 1,065Second proton hall ---- ---- (100) (550) (1,200) (600) Completed 2,450High resolutionspectrometer ---- ---- ---- ---- (150) (300) (500) 1,900*Superconducting muonchannel ---- ---- ---- ---- (100) (500) (700) 2,900*North experimentalarea equipment ---- ---- ---- ---- (200) (600) (1,100) 3,500*(p,n) facility ---- ---- ---- ---- (200) (500) 1,200*Secondary channelupgrading ---- ---- ---- ---- ---- (300) (300) 2,300*EXPERIMENTAL SUPPORTPolarized H target 390 94 Completed 484Frozen spin target 212 476 Completed 688ySR facility ---- ---- ---- (300) (300) Completed 600*Cash flow required in future years ( ) Cash flow dependent on future decisions and/or buildingsneutron beam profiles measured through the neutron collimator. Progress has been made on the dilution refrigerator for the large volume frozen spin target with successful cryogenic tests to 200 mK, and the NMR system has shown that it can detect the proton ther­mal equilibrium polarization signal at 4°K.The neutron area has been arranged to be a separate lock-up area in the proton hall so that access is available to beam line 4B during running of neutron experiments.Considerable effort was spent during this past year in studying the options for future experimental facilities at TRIUMF. An ad hoc committee of the IEP Grant Selection Committee visited TRIUMF in January to review the proton program and to make recommenda­tions on the future plans. There were two meetings of the Long Range Planning Committee in January and March to review facilityoptions. For these meetings two documents were generated by the Experimental Facilities Division - "Options for TRIUMF Experimental Facilities in the Next 5 or So Years" and "Options for the Proton Program at TRIUMF".The results of the deliberations of the com­mittee are available in the committee reports.One action resulting from these meetings was the planning of a spectrometer workshop which was held at TRIUMF during the first week in April. Karl Brown from SLAC and Stan Kowalski from MIT were invited to review our plans for a second arm to the existing MRS spectrometer. The purpose of the review was to assess both the design of the second arm spectrometer and the advantages or disadvan­tages of coupling the spectrometer to the MRS. The conclusion was that the second spectrometer is a worth-while addition to our facilities but that further ray-trace studies were needed to confirm the design.93The other project which has been given the go-ahead this year is the M15 surface muon channel which uses the 150° vertical take-off from the 1AT1 target. The experimental area will be in a new 2400 ft2 building located at ground level to the south of the meson hall. Engineering work has started on the design of this channel. The configuration of the front section of this channel is shown in Fig. 87.There has been considerable discussion on how to use the remaining Phase II building money. Late in the year a decision was made to use the money for an Experimental Support build­ing and to seek funding for a new proton hall in the next phase of building money requests.In the following sections more detailed descriptions of the projects and experimental support activities of the division are provided.EXPERIMENTAL SUPPORTThe effort to improve the level of support to experiments continued this year, and a number of developments have increased the instrumen­tation facilities available as well as the efficiency of their use. The data acquisi­tion systems have been augmented with several hardware improvements and ongoing software development. The nucleonics pool has under­gone a major change by the removal of many rental charges to users, and more coordinated supervision to share modules to meet experimental needs.The facilities to support detector develop­ment have been extended with more space allo­cated for this activity and a clean room under construction. This has enabled a variety of design and test projects to beundertaken both by the detector development group and by experimenters themselves.Several wire chambers have been designed and fabricated in support of various experiments, and some improvements to existing chambers have been made at the wire chamber facility at the University of Alberta.A Technical Review procedure has been imple­mented to help and encourage experimental spokesmen to provide well in advance informa­tion to the Experimental Facilities Division about upcoming requirements for a range of areas of support requested from TRIUMF.A new technician was hired this year to help users in the meson hall in the set-ups and to facilitate the shared use of the experimental areas and counting rooms by the several groups that work there.Data acquisition systems and CFATThe CFAT (Computing Facilities at TRIUMF) Committee continued this year in exercising its mandate to oversee the administration and support of the standard data acquisitionH O R IZO N TAL  B E A M  A X ISB4 H  EL 2 9 0 '-9 .9 "R E M A IN D E R  OF CO M PO N ENTS NOT SHOWNFig. 87. M15 channel.EL 2 6 8 - 6 "94systems as well as to review and advise the administration on other computing facilities. Although the Committee's mandate related to the latter function is comprehensive in principle, its focus has been in particular on those facilities related directly to the experimental program.A number of hardware developments have taken place this year. Additional disc drives have been acquired for some of the systems and several VT640 graphics terminals have been installed including some on-site upgrades of VTlOO's. These terminals serve also as remote terminals to the VAX 11/780. A new PDP 11/34-based standard DA system was bought to cover the requirements of the Mil channel which was fully operational this year. This removed much of the scheduling pressure from the PDP 11/60 which was then available for fast off-line analysis for the uSR experi­ments. In an attempt to enhance further the PDP 11/60 for ySR analysis a Computer Designs MSD-3X array processor was purchased; unfortunately the device did not live up to expectations and was found to be unsuited for the application.When the experimental program of the BASQUE group was completed in June, its PDP 11/34 was taken over and upgraded to the standard DA system configuration. It has become a development system primarily for software but also for hardware support of the other sys­tems, and has brought an end to the nomadic life of the programmers who previously had to cope with fleeting access to one or another of the on-line systems. The development system can, of course, serve as a back-up for one of the other systems in an emergency.Some of the peripherals for the development system were acquired from a PDP 11/40-based system obtained from the University of Victoria Physics Department.This year TRIUMF has relied heavily on in- house maintenance for the DA systems, with reduced use of outside maintenance contracts and service calls. This effort has been greatly helped by the increasing degree of standardization, an improved spares inven­tory and the growing experience and expertise of TRIUMF staff.One recognized shortcoming of the present DA system hardware is lack of universal access to good quality hard copy graphics. To improve this two schemes are being pursued: first, to multiplex access to the Printronix printers, and secondly, to evaluate agraphics upgrade to the LA120 (Decwriter III) console terminals.A major opportunity presented itself in October when the Expt. 185 group from LBL brought a VAX 11/750 to TRIUMF for their data analysis. The system is expected to be on site for one to two years, and in return for sharing maintenance and other support TRIUMF will have access when the system is free to evaluate and develop a variety of applica­tions being considered for other similar systems.A second programmer was hired this year to support and develop applications programs for the DA systems and complement the system programming effort for both the PDP 11/34's and the VAX. A number of software improve­ments have been realized. The MULTI-DA package has been greatly improved for user convenience, data-logging efficiency and efficiency of memory space as well as better handling of scaler data and computer dead­time logic. In addition a package has been written to handle high rate single parameter experiments for the SFU group using the Lecroy 3512 ADC, 3588 histogramming memory and 3587 data routes. A graphing and curve- fitting program has been developed, initially for MULTI-data, but later adapted to handle other data formats as well. A second general data acquisition package, "PHA", has been adapted for the standard systems. It is based on a Data General Nova package and uses the same CAMAC and data-logging routine as does MULTI. PHA, while somewhat less general and flexible (at present at least), has some significant speed advantages over MULTI (typically x3 depending on histogramming activity).At year-end a strategy was formed for upgrad­ing the RSX-11M operating system to version 4.0. This latest version takes up more memory, requiring a sacrifice in histogram­ming space, but has a number of advantages including DCL which makes it similar to VAX/VMS from the user's viewpoint. To com­pensate for the memory loss, development of a data-space memory for the PDP 11/34 is being investigated.The CFAT Committee has reviewed the use of LSI 11 systems on site, such as the MIK-11 and Kinetics 8033 as well as DEC-supplied PDP 11/23 and 11/24 systems. The PDP 11/34 is now priced very competitively, and it was noted that in general the loss in performance and board-level compatibility for the LSI's95is not compensated by the marginal cost saving. The PDP 11/34 remains the system of choice (for 16-bit CPU's), especially if any degree of compatibility with the standard software is desired. In this regard, it has also been recommended that the remaining PDP 11/40 systems be phased out as budgets and changeover effort permits.A disc management system has been proposed for the DA systems whereby all user-specific files will reside on the user disc (DL1), making it unnecessary for users to retain their own system discs (DL0) . The resulting reduced number of system discs can then remain on the drive units and can be readily and uniformly updated as the software develops.A number of circumstances have focused the Committee's concern on development of a new generation of "standard" system based on a 32-bit CPU: e.g. the upcoming retirement of the ySR PDP 11/40, the future need for a sys­tem for M15, the availability of the LBL VAX 11/750 for development, and a proposal for a new system for the TPC. It is likely that the architecture of such a system will require distributed intelligence in the front end for adept interrupt handling and data­logging so that full advantage can be taken of the 32-bit computing power. A number of options for the front end can be considered including a streamlined modification of the existing PDP 11/34, various intelligent CAMAC controllers, and possibly the MBD.The Committee is in the process of formulat­ing a philosophy and policy for the applica­tion of 32-bit processors on site. Because of the range of applications, hardware capabilities and costs, a simple and uniform standard seems impractical at present.Nucleonics and IACA major change in the guidelines for the oper­ation of the Instrumentation Pool occurred in February when the NRC sanctioned the re­moval of pool rental charges, retroactive to April 1, 1981. Included in the policy changes were clauses stating that rental charges could still be applied in certain cases. For example, if major experiments require large amounts of nucleonics that could not be provided either from the Instru­mentation Pool inventory at that time or be capitalized by the experiment through NSERC funds, then TRIUMF would negotiate the pur­chase of nucleonics and apply rental charges over an agreed amortization period.The assignment of equipment to experiments is now based on the Technical Review report submitted by the experimental spokesman during the experiment proposal evaluation and updated as the electronics requirements of the experiment change during the setting up and running periods.These changes in the mode of operation have allowed the optimum allocation of equipment amongst the running experiments. During several periods in 1982, over 95% of the modules in the Instrumentation Pool data-base have been in use simultaneously. Hence the Pool has been able to support a larger number of more complex experiments running simultan­eously than was possible under its previous allocation arrangement.During the course of the year eleven new Pool standards have been defined by the IAC, necessitating the evaluation of twenty-six modules. More than 200 new modules have been added to the Pool inventory.The Annual Spring Meeting of the Association for Research Electronic Pools (AFREP) was held at TRIUMF in May attended by the heads of the Instrumentation Pools at Brookhaven National Laboratory, Fermi National Labora­tory, Los Alamos National Laboratory,Lawrence Berkeley Laboratory, Lawrence Livermore National Laboratory and Stanford Linear Accelerator, plus representatives from TRIUMF. Electronic developments at each laboratory were presented. The uses of auto­mated test facilities for module repair, checkout and calibration were discussed with the aim of defining standard test systems and computer programmes for this task. For a relatively small laboratory such as TRIUMF, its information exchanged in such meetings with the Nucleonics divisions of the United States national laboratories is extremely valuable.TRIUMF continues to provide in-house repair and maintenance facilities for nucleonics modules and data acquisition systems, and where it is most effective external companies are used.Detector facilitySeveral major improvements have occurred in the last year: completion of the gas handling room for proton hall wire chamber users, a96scintillation counter bank which allows users to borrow counters for a short time, a small area in the proton hall annex for testing counters, the construction of large area wire chambers, the start of several development projects and the installation of a new clean room for repairs and assembly of wire chambers•There are, however, several problems that require solutions. The manufacture of coun­ters for TRIUMF suffers from large fluctua­tions in manpower requirements. This produces unwanted delays in their manufacture and in some cases (when overtime labour is required) it increases the cost of the detec­tors. One way to overcome partially this problem is to bring the scintillation con­struction and the wire chamber construction to TRIUMF and share the technicians and the equipment.The following development projects have been completed. A light transmission Monte Carlo program has been developed, which allows determination of the fate of photons in scintillators and light guides of different shapes. This program is already in use at TRIUMF as well as at SLAC and Saclay.We have built and tested a very fast two- dimensional hodoscope to be used in secondary beam lines at TRIUMF. It has a spatial reso­lution of 8 mm and will accept an average rate of 108 particles per second.We have measured energy resolutions of Si photodiodes with Nal crystals, as replacement of photomultipliers.We also attended the IEEE meeting (Washington, DC) and the Int. Conf. on BGO (Princeton) where some of the above work was presented in contributed papers.Wire chamber facilityThe major project this year was the assembly of eight 60 cm aperture wire chambers for Expt. 121. These chambers were completed in November.A prototype drift chamber for the MRS focal plane was completed in June. Currently plans for a second version of this chamber arebeing worked on for use in Expt. 208. Somematerials for the chamber have been ordered.A third version of this chamber, for the MRSfocal plane, is planned for next year.Construction is under way on a 90 cm x 40 cm chamber for Expt. 190. This chamber is simi­lar to the 60 cm chambers of Expt. 121 but is configured as two 40 cm x 40 cm chambers in one frame with a 10 cm dead gap in the centre. The option exists of activating the 10 cm region in the middle to get the full 90 cm x 40 cm aperture. This chamber is scheduled for completion around the first week of January 1983.A single wire proportional counter was con­structed for M. Salomon and a 5 in. aperture chamber was repaired for R. Openshaw. Presently five stacks of planes for beam line MWPCs are being fabricated. The beam line stacks are scheduled for completion in February.A new model 5 in. aperture chamber was designed and constructed. The changes resulted in a chamber that is easier to assemble, less prone to gas leaks, and easier to service. This was gained at the expense of a larger envelope size, the new model being 9.25 in. x 13 in. x 1 in.MESON HALLM11 channelAn improved tune has been established for the Mil channel through an iterative procedure with TRANSPORT runs and experimental trials converging to the result listed in Table IX. The origin of the higher-order aberrations that make the final beam spot, FWHMX = 30 mm, FWHMy = 25 mm, much larger than the design value of FWHMX = 4 mm are presently being studied using the computer programs REVM0C and RAYTRACE. A proposal for changes to im­prove the optics of M il  will be ready in early 1983.A study of the use of the Mil channel as a source of backward muons has concluded that Mil produces about 10% the backward p flux available in the present M20. However, low- rate experiments may be able to use Mil profitably.97Table IX. Sample achromatic tune at 65 MeV (P = 150.9 MeV/c).aElement DAC Current(amperes)Magneticfield(gauss)11B1 16,925 254.0 464611B2 14,201 212.0 449711Q1 213 100.211Q2 157 76.611Q3 185 88.211Q4 19,850 294.911Q5 363 172.511Q6 216 104.911SX1 163 31.611SX2 off11SX3 265 51.411SX4 140 27.211SX5 off11S1 23,200 1769.01AQ9 20,239 231.5aSlits set at 3%; 70% of the beam passed through a 3 cm diameter hole counter.M13 low-energy n-u channelDuring the year the channel has operated without any major problems. The requirement that It work in conjunction with the QQD spectrometer has required changes to upgrade it beyond the initial design criteria. Two sextupoles were installed close to the two dispersed foci and the vertical slits removed to make way for them. During tuning of the channel for the QQD it was found necessary to move the dipoles slightly in order to align the beam axis with the quadrupoles to eliminate beam steering. The movement has decreased their nominal current settings by about 0.6%.Hall probes have been installed in all the elements except M13B1 and NMR probes are installed in M13B1 and M13B2. It is proposed to incorporate the Hall probes into the channel control system. Progress is being made towards making the NMR in M13B1 more radiation hard.The momentum resolution of the channel with 50 MeV e+ was measured to be 0.5% Ap/p (FWHM). This corresponds to an energy resolution of 435 keV for 50 MeV it+ . The measurement has not been repeated since the sextupoles were installed, but a significant improvement is expected.QQD spectrometerThe QQD spectrometer (Fig. 88 ) was assembled for the first time for an initial commission­ing run on Mil during the April-May high intensity beam period. Although the channel resolution was inadequate to test the resolv­ing power of the spectrometer several other aspects of the QQD were commissioned. Some areas for improvements were uncovered.The QQD spectrometer was reassembled for the July-August high intensity period, on M13. Again limitations of the channel prevented the limits of the resolving power of the spectrometer from being tested. The angular acceptance was found to be very close to the predicted value of 20 msr. A preliminary set of transfer coefficients was established for a limited acceptance that corresponded close­ly with those predicted by TRANSPORT. A resolution of 1.5 to 2% was established for the M13-QQD spectrometer combination.A procedure for evacuating the spectrometer vacuum vessel and wire chambers and refilling with helium was commissioned. REVM0C studies predict a factor of three reduction in multiple scattering contributions to the resolution for a helium filling compared with air.The largest problem with the M13 channel for use with the QQD spectrometer was found to be a large steering effect caused by changes in the magnet fields of the M13 quadrupoles.98The source of this effect was determined to be the physical positioning of the M13 dipoles. The analyses indicated that both dipoles needed to be moved approximately 1 cm. These moves were made during the September-October meson hall shutdown.The QQD spectrometer was once again reassem­bled for the last nine days of the November- December intense beam period. The assembly time required was greatly reduced by the development of a single lift apparatus that enabled an almost completely assembled spec­trometer to be lifted into the M13 area.The largest part of the nine-day run was devoted to studies of the M13 channel. The repositioning of the M13 dipoles greatly reduced the steering effects of the quadru­poles. This in turn enabled a detailed study of the energy dispersion of the beam at the first and second slits and at the experi­mental target position. A detector telescope consisting of three germanium crystals, each1.5 cm thick, was used in the measurement of the energy-resolving capability of the channel in order to have an independent check of the spectrometer. An achromatic channel tune for 50 MeV it ' s  was devised which had an energy width of approximately 500 keV.The next step was to study the sextupole effects. A sextupole setting was found forwhich the sextupole aberrations were removed, for a slit #2 opening of ±13 mm, i.e. ±1%. Beyond this opening width the remaining steering effects and other aberrations (octu- poles) become operative. Several tunes were then studied that produced dispersions of +2 cm/% to -1 cm/% at the experimental target. All of the above results are in full agree­ment with TRANSPORT calculations made follow­ing the experimental studies.The achromatic tune was then used to study the QQD spectrometer. The data indicated an on-line resolution of better than 1% and is presently being analysed off line.M9 channel and RF separatorAfter an extensive period of tests and modi­fications and repairs and more tests during 1981 and early 1982, the RF separator met the power and reliability criteria required for use in M9. Installation began late in the winter shutdown and by March the M9 extension was rebuilt including the separator and ready for commissioning. Figure 89 shows the present layout of M9 and the RF separator. Figure 90 shows the separator after assembly (but before installation) with the trans­mitter in the background.The tuning of the beam line to the M9W3 loca­tion upstream of the Chicago magnet went99Fig. 90. RF separator, general view.smoothly with all but two elements being within 10% of their calculated tune settings. The beam line was then tuned to the M9W4(TPC) location using a 14-element hodoscope inside the TPC-Chicago magnet, and spot sizes of the expected ~8 cm FWHM were achieved. The first tests of the separator in beam were then carried out. With the nominal values of RF power and the crossed magnetic field and phase tuning, with respect to the beam line 1A capacitive probe, a muon flux of 106 y“ s-1 for 100 pA was obtained at the entrance of the Chicago magnet, in very good agreement with expectation. The pion contamination at this position is a few parts in 103. A more detailed study of the contamination of the transmitted beam to the target was made by a normalized measurement of high energy (>400 MeV/c) prompt protons from pion capture. These measurements showed a pion fraction in the degraded and collimated muon beam of 2 x 10“ 1*.The beam transmitted to the TPC target posi­tion was up to 80% of the incident beam at the magnet entrance. However, with the collimator (3 in. <f>) and degrader required during the y->e experiment with a titanium target, the useful stopped beam is about 50% of the incident. Improvements are planned for the collimator design and rate capabili­ty of the TPC itself in order to make full use of the total flux possible.Figure 91 shows a sketch of some details of the separator and some of its design and operating characteristics. Figure 92 shows schematically the principle of operation of the separator on the transmitted beam with respect to time of flight of the beam con­stituents. Figure 93 shows a detail of the separator's deflector plates which carry the RF voltage of up to ±180 kV.The separator produces several hundred mR/h of X-rays - an order of magnitude less than the dc separator - but still an important concern for shielding requirements, especial­ly for wire chambers. This and RF electricalIPERATINGFR EQPOWER0PARAM ETERS 23.1 MHz 100 kW50 00Fig. 93. detail.RF separator, deflector platesGAP DIMENSIONS 15cm *  100cm ELECTRIC  F IELD  24kV /cm  MAGNETIC F IE L D  113 jou ssMOMENTUM RANGE 4 0 - 9 0  MeV/c PION REJECTION  10’’  J 7 4  MeV/cELECTRON  REJECT ION  10Fig. 91. RF separator for M9. Fig. 92. Time distribution of secondary particles arriving at the RF separator.100pick-up are ongoing concerns but have been managed successfully.The most severe difficulty encountered thus far with the separator was the problem of RF radiation to the thin vacuum isolation windows. Installation of smaller RF shield- apertures and a change from 0.00025 in. aluminized mylar to 0.00075 A SL metal foil windows appears to have solved this problem.The separator has been operated thus far using the old CRM controls with some adapta­tions. This system has proved more or less satisfactory, the main problem being poor phase regulation of only ±15°, about a factor of 3 worse than desired. However, a new control system continues under development and should be capable of overcoming this as well as some other minor operational diffi­culties .The M20 users eagerly look forward to the complete rebuild of the channel that is to take place in spring 1983. This should have the effect of substantially increasing the backward muon flux, permitting spin rotation of the surface muon beam, and generally making the channel more "user-friendly".M20 improvementsIn 1982 the design and construction of the improved M20 channel (shown in Fig. 94) has proceeded towards the expected installation date of January 1, 1983. All major compon­ents have been fabricated or procured with the exception of the second dipole and two quadrupoles which are presently in use in the existing channel. These three components will be refurbished and field mapped at the same time as the front-end components are being installed.M20 channelThe intense competition for M13 beam time and the monopoly of M9 by Expt. 104 resulted in greater demand for M20, since this became the only channel available for the myriad ySR ex­periments in addition to other experiments requiring a significant flux of backward muons. Happily, the channel worked well, and in fact considerable improvements to its surface muon operation were achieved. There has been a continuing program of power supply replacement as new units were acquired in anticipation of the channel rebuild, and this allowed installation of a shunt to enable separate control of two parts of the quadru­pole string section. Also beneficial were a new Marmon flange window and beam "snout". Finally, a short dc separator was commis­sioned to give a clean surface muon beamThe optical components have been mounted on modular, relocatable stands which will allow quick removal, repair and replacement in the event of component failure. All available magnets have been individually tested and field mapped and, when appropriate, power tested after installation and interconnection as part of a multiple magnet module. This pre-assembly and testing should significantly reduce the final installation time.for first time on M20ratio dropped from ~-40 to less than at 100 pA p+ on 10 cm Be at 1AT2). B L O C K E RM 2 0 B 294. M20 channel.101The fabrication of the vacuum system has been completed except for the welding of some interconnecting flanges which will be aligned and welded at the time of installation. The remote handling fittings on the vacuum pipe through the first two quadrupoles have been assembled and tested to the extent possible before installation of the doublet.The momentum slits, two beam blockers in the second dipole vacuum box and the separator slits have all been fabricated, assembled and tested in their respective vacuum boxes. All these devices are ready for installation and connection to the control and safety systems.Some considerable effort was made to design the shielding required to surround the channel, before the time of installation.This required a reasonably detailed defini­tion of all power, water and control services and the exclusion outline of all devices within the shielding. As a result, all special concrete and steel shielding blocks have been fabricated and a complete design of the shielding is on hand.The final work to be completed before instal­lation begins is the detailed PERT of the installation activities and a corresponding radioactive dose study required to investi­gate possible personnel exposure problems to be encountered during installation.Beam line 1B and Resolution spectrometerAn extended period of polarized beam was available during the summer, thereby permit­ting extensive data collection for the reac­tions fid ->• tTT+ and fi10B -»• 11Bir+ on the "Resolution" spectrometer.Experimental measurements using the Resolu­tion spectrometer have now been completed, and the spectrometer removed from beam line IB. The tt production experiment from Los Alamos, "CALLIOPE", has now been installed at beam line IB and will begin data-taking during January 1983.Beam line 2ABeam line 2A has been placed "on hold" until a design for the kaon factory has been finalized. The BL2A combination magnet has been completed and its field surveyed.Beam line 2CDuring the July shutdown two small 4 in. quadrupoles, 2CQ4 and 2CQ5, were installed onthis line. This completes the component installation for the line. A more complete description of this facility and of the tar­get development for isotope production will be found in the Applied Programs section.PROTON HALLBeam line 4AThere was a significant change in the utili­zation of beam line 4A for experiments during1982. Most of the beam time before the end of June involved specialized use of the primary beam for the completion of Expts. 77, 143 and 174. The shutdown in the early summer saw the removal of both the cesium target used in the production of 123I and the low intensity proton beam line 4C. The latter activity enabled the re-establishment of the neutron area. Although there is ongoing use of the primary beam in the 60 in. scattering chamber and the gas jet irradia­tion facility for Expts. 117 and 189, much of the beam line is now devoted to neutron pro­duction for Expts. 121 and 190.The removal of the cesium target located immediately in front of the beam line 4A dump was preceded by a relocation of the TRIM trailer to a site in closer proximity to beam line 2C. To remove the target it was neces­sary to dismantle the local iron shielding and all of the components of the beam line downstream of 4AVA8. The local shielding is no longer required but all the beam line components with the exception of the target, its collimator and one irradiation facility were reinstalled. Unfortunately, during the move an electrical fault developed in the beam line 4A secondary emission monitor.This device was therefore removed and subse­quently replaced by the SEM originally used in beam line IB.Activities during the October shutdown included the completion of a refurbishment of the LD2 target used for neutron production and the installation of Hall probes on the beam line 4A quadrupoles.Beam line 4BOver New Year 1981/82 the 4BT1 and 4BT2 ac­quisition systems were relocated in new count­ing rooms constructed as part of the service annex extension. The H-316 acquisition system was ready by January 15 and the S-200 Eclipse NRS acquisition system became opera­tional by February 8. In addition an S-130Eclipse was installed and was used for replaying of tapes by mid-March.The movable Faraday cup on beam line 4B has been modified so that it can be kept opera­tional at all times and be requested by ex­perimenters using BL4B (Ip ^ 1 nA).The precision requirements of Expt. 171 (time reversal invariance in proton-proton elastic scattering) made it necessary to develop a feedback system using secondary electron emission monitors (SEM's) capable of operat­ing at incident beam currents of 50 nA as well as 50 pA. At a beam intensity of 50 nA the SEM's operated at beam line vacuum. At the low beam intensity of 50 pA the SEM's were pressurized with Ar to 15 Torr to again allow satisfactory operation of the automatic beam control feedback system. To compensate for any leaks in the essentially zero flow gas system (SEM's in series) a manostat maintained a preset pressure. The manostat was modified to allow the use of the beam line vacuum as reference.The installation of Hall probes in all quad­rupoles and NMR probes in all bending magnets allowed the successful tuning of beam line 4B based on theoretical tunes at 200, 300, 400 and 500 MeV.The gas handling system for the proton hall has been relocated in a building built onto the north wall of the proton hall extension. The system now provides four feeds (4BT1, 4BT2, neutron facility and spare), allowing three different mixes and one pure isobutane line.The shielding of the proton hall was improved to allow increased intensities in beam line 4B. During Expt. 212 (tredecabaryon) inten­sities in excess of 100 nA (100 mg cm-2 12C target) were achieved.Neutron facilityDuring the July shutdown the low-intensity proton beam line 4C was removed to make way once again for the neutron facility.The 4VB1 vacuum vessel was outfitted with a port to allow surveying of beam line 4A from the cyclotron vault. In addition NMR plates were installed in 4VB1 and 4VB2 and are read out in the control room. The superconducting solenoid Janis was installed in beam line 4A, approximately 2 m upstream of the LD2 target: beam line 4A was resurveyed and necessary ad­justments to quadrupoles and multiwire pro­portional chamber monitor boxes were made. Special attention was given to the alignment of the 9° port. The "9° line" as defined by the neutron collimator originally intersected the LD2 target at its downstream end. The collimator inserts were subsequently removed and remachined, and the 9° line now points to the centre of the LD2 target. The clearing and neutron spin precession dipole magnet Clyde (former UCLA magnet), providing a vertical magnetic field of up to 20 kG, as well as the second neutron spin precession dipole magnet Bonnie, providing a horizontal magnetic field, were installed and surveyed on the 9° line. Additional collimation in Clyde defines a neutron beam of 2 in. x 2 in. at its exit. The pivot arrangement of the range counters for Expt. 121 as well as the neutron polarimeter and the neutron arrays were installed and surveyed.Experiments 121 and 190 continued to share the task of commissioning the neutron facility. The LH2 target was installed in preparation of Expt. 190 and successfully operated using the TINA flask.The proton polarimeter was commissioned at 500 and 195 MeV while the neutron polarim­eter was tested at 500, 285 and 195 MeV. Neutron beam profiles were measured at the three energies (500, 285 and 195 MeV). Beam intensities in excess of 500 nA were obtained at the aforementioned energies. The limita­tions in beam intensity seem now largely due to LD2 target-associated radiation spills.MRS operation and upgradeOperationsDuring 1982 the medium resolution spectrom­eter continued to operate essentially unchanged. It was used in the following ex­periments :113 Elastic scattering of protons on 3He114 Quasi-free scattering of protons in 3He 121 Tagging protons for counter tests165 Inelastic proton scattering 195 Search for fissioning mesomolecular states excited by inelastic proton scattering 208 High flux counter tests 212 Feasibility test runs for large angle small cross-section measurements103UpgradeProgress was made on a number of fronts towards achieving a momentum resolution of Ap/p - 10“ 4.New target chamber. The new target chamber together with its fairly complicated support assembly has been fabricated and installed on the round table from the 4BT2 MRS target station. This system provides for continuous vacuum from the beam line through the spec­trometer by rotating with the spectrometer while coupled to the beam line via large flexible bellows. The new chamber was tempo­rarily removed pending final installation in February 1983 together with a control system. The chamber will ensure safe containment of any flammable gas leaking from a low pressure wire chamber which is to be mounted in the spectrometer port on the target chamber. The design is complete and fabrication under way of a horn-shaped extension to be coupled to the new chamber for operation at scattering angles in the range 3-15°. It is expected to be available in spring 1983.Focal plane detectors. A small-scale proto­type vertical drift chamber (VDC) together with its Lecroy 4290 TDC/wire readout system has been successfully tested. The spatial resolution, although inferred indirectly, appears to be in the 200 to 200 pm region, quite adequate for the new focal plane chambers which are now to be built. Unfortu­nately, some delay is expected in their construction because of either the backlog in the TRIUMF wire chamber shop or the need to prepare commercial-grade engineering drawings if they are to be constructed elsewhere. However, it is hoped to have one new VDC ready for high-resolution commissioning work beginning immediately after the February- March shutdown.Front end wire chamber. This device has been completely redesigned. The original cathode and anode frames were insufficiently rigid.A new vacuum enclosure has been fabricated which is compatible with the original gas containment foil frames. New cathode and anode frames are now being assembled.Dipole shims. Pole-edge shims for the exit end of the MRS dipole have been fabricated and installed for tests involving tracking protons through the spectrometer. The results are equivocal. Although the shims are designed to untilt the focal plane from 66° to approximately 45°, to reduce multiplescattering in the exit foil of the spectrom­eter vacuum vessel, the resulting focal plane angle was 54°. A tentative explanation for this is the proximity of the coils to the pole edges. Magnetostatic calculations are now being done to confirm this and to investigate the usefulness of field clamps that might be installed in the very limited space available. The 54° focal plane angle is adequate for good resolution over a ±5% momentum bite.Beam line dispersion twister. Since the MRS uses a vertical bend, a beam phase space rotation is necessary to match the beam dispersion on the target to the spectrometer D/M. The original optical design for a five- quadrupole twister was dropped in favour of a six-quadrupole system which acts as a true unit section between the upstream 4BT1 target location and the MRS target station. The resulting advantages are considerably reduced vertical angular dispersion at the target and less sensitivity to errors in alignment and quadrupole field values.A massive rotating carriage for the six quad­rupoles has been designed and fabricated.The magnets are now being installed on the carriage. The mechanical rotation capability is required to provide horizontal dispersion for diagnostic work as well as to accommodate spin-precessing solenoids upstream which are needed for measurement of spin rotation param­eters. The carriage will be mounted on rails beneath the beam line so that it can be rolled up or downstream to maximize space available at whichever target station is in use. Installation of the twister will take place during the shutdown of February-March 1983.The present schedule calls for commissioning the upgraded spectrometer system with beam tests in April-May 1983. Although it not yet clear how difficult it will be to obtain dis­persed beam tunes with the required preci­sion, it is possible first experiments using improved energy resolution (~100 keV) could begin in the summer of 1983.Second arm spectrometerFor some time a design has been evolving for a relatively large solid angle pion spectrom­eter for pion production studies over the full TRIUMF energy range. During 1981 it became clear that the original plans for installing such a device on beam line IB gave rise to space conflicts, large costs for ex­tending the beam line, and possibly poor104performance of the device due to beam energy spread. In addition, a case was put forward for using the spectrometer in coincidence with the existing MRS for (p,2p) measurementsThe decision was consequently taken to install the new spectrometer (with a vertical bend) as a second arm spectrometer (SASP) at the 4BT2 target position where the MRS now operates. This would take advantage of the dispersion twister now being installed in that beam line, for MRS operation, to dis- persion-match to the SASP for pion production. This becomes more difficult at the lowest beam energies. It will also be possible to dispersion-match to the missing mass or crudely speaking, the summed energy, when the two spectrometers are operated in coincidence for (p,2p) measurements.The design specifications for the SASP are summarized below:• short flight path• maximum (central) momentum• momentum acceptance• solid angle• momentum resolution• angular range• beam spot acceptance (dispersed)• opening angle between two spectrometers-£5 m 600 MeV/c Ap/p = ±20%15 msr Ap/p ^ ±2x10“4 20°-160°±1 cm<50°During 1982 optical design studies were con­tinued to determine whether the original QD design could be adapted to this new situa­tion. This work involved ray-tracing to investigate the aberrations beyond second order, which become important for such a large solid angle acceptance. The MFT RAY- TRACE code has been modified to explicitly incorporate dips in the dipole field arising in the "semi-split pole" design used in the QDQ at NIKEF-H in Amsterdam. A recently hired physicist is now working on this proj­ect full time. It is hoped that detailed redesign of the spectrometer components can begin early in 1983.TARGETSPolarized targetsLiverpool polarized proton target. The Liverpool polarized proton target was ope­rated for three runs of Expt. 174 during the first half of the year. Following the con­clusion of the experiment the target wasmoved to the CRM to be fitted with a dilution refrigerator. This conversion will allow the target to be run in the frozen spin mode and also allow reasonable deuteron polarizations to be achieved. The dilution refrigerator is one of two being built in conjunction with Dr. G.R. Court of the University of Liverpool. His refrigerator was recently completed and has been operated at temperatures below 50 mK. At year's end the assembly of the TRIUMF dilution refrigerator was well advanced.Large frozen spin target. Various components of the large (50 cmd) frozen spin polarized proton target have been completed. These include the cryostat, the helium-3 and helium-4 pumping systems, and the supercon­ducting polarizing magnet. The dilution refrigerator has been assembled and has been operated down to a temperature of 200 mK.The low temperature tests are continuing with the objective of obtaining an operating temperature of 50 mK. The NMR system is partially assembled and has been demon­strated to detect a proton thermal equilibri­um polarization signal at 4.2 K. The designs for the target stand and the holding field magnet have been completed.Cryogenic targetsLiquid deuterium neutron production target.The renovation and recommissioning of the neutron production target in BL4A have been completed, and the target was operated for several runs of Expts. 121 and 190 during the second half of the year. The target was demonstrated to handle an incident proton beam of 1 pA and heating tests indicate this can be increased to 1.5 pA.Liquid hydrogen targets. The liquid hydrogen target was operated in the Mil experimental area for Expt. 9 during the first half of the year. It was then set up in the BL4A neutron area, with a new flask and vacuum vessel, for Expt. 190. A second CTI refrigerator was purchased, to allow renovation of the second liquid hydrogen target. This target was de­commissioned when its refrigerator was returned to the Rutherford Laboratory in England.Superconducting solenoidsThe BASQUE solenoid was removed from BL4A and put into storage. The Janis solenoid was operated in BL4C for Expt. 174 during the first half of the year. It was then moved into BL4A, immediately upstream of the105Fig. 95. (clockwise) M20 BI dipole; spin precession dipole and UCLA magnet in beam line 2C; beam line 2A combination magnet; 3 - 12 in. quadrupoles for M20.neutron production target, and operated for several runs of Expts. 121 and 190.EXPERIMENTAL FACILITIES ENGINEERINGMagnetsDuring this year outstanding orders for stan­dard 4 in. and radiation-resistant 8 in. quadrupoles from Alpha Scientific were completed.Local manufacturers are now being used for a greater proportion of our magnet requirements. Ebco Industries of Richmond supplied steelfor the M20B1 dipole and the spin precession dipole as well as the yokes, poles and assembly of three 12Q12/5 quadrupoles for M20. Beaver Electric of Burnaby supplied a Helmholtz coil pair for the M20 experimental group, and Best Coil, also of Burnaby, made the saddle coils for the M20 short separator. These two companies will also supply coils for the holding magnet of the frozen spin target and a small Helmholtz coil array for TNF experimenters. Some of these magnets are shown in Fig. 95.Two asymmetric sextupoles were built, tested and installed in the M13 beam line (Fig. 96). The as-built magnet had a strong dipole106Fig. 96. (a) M13 sextupole, (b) M15 proposedquadrupole.component which was reduced to an acceptable level by removing the tips of the short poles.Conceptual designs for 5° dipoles and quadru­poles for kaon factory extracted beam were made as a function of energy. Costs of mag­net plus power supply at 15 GeV were 1.25 times and 1.11 times those at 10 GeV for dipoles and quadrupoles, respectively.Preliminary designs for the magnets for the proposed M15 secondary channel have been made and detailed drafting has started for a new short 6 in. bore quadrupole. The line design calls for eight of these magnets with the following characteristics:Bore 6 in.Effective length 22.5 cmField gradient 1.6 T m-1The proposed magnet is shown in Fig. 96.Beam linesConsiderable effort has been extended on the M20 channel upgrade throughout the year. Inaddition the vault beam lines have been up­graded to replace the old 4 in. Marmon quick disconnect vacuum seals, which use "0” rings, with a new 4 in. indium seal design. The combination magnets are also being upgraded; CM4 is completed. The vacuum chambers are now to be welded directly to the cyclotron vacuum chamber to eliminate the old "C" ring seal which was impossible to replace without exceeding TRIUMF radiation dose limits. New stands allow the base of the magnet to be removed sideways and replaced in exact align­ment. The cooling header design has also been upgraded. The two 8 in. quadrupoles immediately ahead of 1AT2 have been replaced with radiation-hard types and the section of beam line 1A between 1AT1 and 1AT2 will be upgraded in 1983. Design is complete and components are being manufactured.Beam line 4C was removed and rebuilt for the charge symmetry experiment by installing the UCLA magnet and the new spin precession dipole on the 9° neutron collimator port. Three swing cable booms were installed from the west wall. The two dipoles were cere­monially named "Bonnie and Clyde" by the Beam Lines magnet naming committee.The design for the twister on beam line 4B was completed and then modified to accept an extra quadrupole. The frame and magnets during preliminary assembly are shown in Fig. 97.The cesium target station at the end of beam line 4A was removed and the end of the beam line rebuilt. A fence has been installed between beam lines 4B and 4C and a blocker installed at the entrance of 4B. This allows personnel to work on beam line 4B whilst experiments are in progress on 4C.The preliminary design problems for the pro­posed M15 secondary channel are being con­sidered. The main problem is how to install two samarium-cobalt magnets inside the 1AT1 target volume without interfering with the target protect monitor which cannot be con­veniently relocated. Problems of support, access and shielding remain to be resolved.Experimental area supportSecondary channelsOn M9 the installation of the RF separator required relocating several quadrupoles and revising sections of the beam line vacuum. A new door to the RF seperator area was107Fig. 97. Beam line 4B twister during assembly.installed with 1/4 in. lead sheet to shield against X-rays generated by the separator.The Chicago magnet was found to have the hose barbs on the aluminum coils dissolving on the centre section. These hose barbs were origi­nally welded to the coils. The existing barbs, or what remained, have been cut off and replaced with new aluminum hose bards which can be easily replaced.Several large experimental setups were in­stalled in the M13 area during the year. The large Sagane magnet and related equipment had to be dismantled at the end of a long run and replaced with another experiment during a two day period.Two new asymmetric sextupoles were completed along with new slit boxes for FI and F2.After modifying the slits to fit in the shorter boxes, the sextupoles were installed during the June shutdown.The CALLIOPE magnet, part of the apparatus for a Los Alamos National Laboratory experi­ment on pion production, arrived on site in November and was installed in BL1B. Early in December the trailer/counting room arrived and was placed on top of the BL1B roof shielding.The shielding wall between M13 and BL1B was revised to accommodate better access to the BL1B experimental area required by the CALLIOPE equipment. It provided a four foot wide access door from the M13 area and an additional one foot more room on each side of the wall for each area.The BL1B SEM was removed and installed in BL4A. This required modification of its flanges to adapt to an 8 in. marmon flange.A new design of 12 in. marmon flange has been built for evaluation. If successful it will eliminate the grinding off of welded flanges in special locations that may require the removal of beam tube from quadrupoles, e.g. Mil. Design of 8 in. and 4 in. marmon types should be available also.Other areas of support have been in the de­sign of a Si-detector probe assembly for use with an 8 in. beam table which can be inserted and retracted automatically.Magnet MeasurementsAcceptance tests and field surveys of a num­ber of quadrupoles, sextupoles, dipoles and Helmholtz-type magnets were completed. Mag­netic field surveys of the assembled QQD spectrometer showed there was considerable field leakage from the dipole to the quadru­poles, which proved impossible to eliminate; however, RAY-TRACE calculations using the measured fields indicated that the spectrom­eter should operate well at low fields. RAY- TRACE calculations were also compared to experimental optics measurements, and good agreement was obtained up to second order, except for the R ^  term. RAY-TRACE calcula­tions on the front end of Mil indicated a misalignment problem, which should be elimi­nated if 1AQ9 is operated at a higher current; this was later confirmed experimentally.A conceptual design of a fully automated field measuring system was completed and108detailed drafting is under way. With this equipment it will be possible to reduce on­line measuring manpower requirements from one and a half to a half man. Also it will be possible to survey the fields of magnets in the beam curvilinear coordinate system, which will considerably reduce the time spent on foot measurement analysis.Fabrication of the septum magnet was held up because the new joints could not be brazed successfully. It was decided to try yet another joint design, using solid copper blocks with spark eroded slots for the cool­ing water. So far this has proved success­ful and the magnet fabrication should be complete before Easter.109ACC ELERA TO R R E S E A R C H  D IV IS IO NAlthough Kaon Factory Studies have claimed an increased fraction of the Division's efforts this year, a major share continues to be ex­pended on Beam Development for the Cyclotron and Beam Lines, Beam Line Diagnostics and Scientific Computing Services.In beam development work on the cyclotron de­polarization effects have been carefully measured around the resonance at 467 MeV.The expected dependence on vertical betatron amplitude was confirmed and the depolariza­tion was found to be much reduced for a beam of specially selected emittance. Additional studies have concerned stripping foil design for beam line 2C, the reduction of beam loss by the use of third harmonic RF, the distri­bution of activation around the tank, and radial-vertical beam coupling effects. The latter have caused some interference with optics measurements in support of the beam line 4B twister installation, but a correc­tion scheme using a harmonic coil has now been successfully implemented.In beam line 1A the ability to reverse quad­rupoles Q10-Q13 in sympathy with Q9 has made low spill tunes easier to obtain when switch­ing Mil from tt+ to tt- operation. The use of heavy metal targets at 1AT1 would provide higher fluxes for the Mil and M13 channels; the additional beam spill downstream, how­ever, appears to be unacceptable. A split beam design has been shown to be possible for feeding a south hall. This could be used to supply either a fraction of the high intensity unpolarized beam for fast neutron production or the whole of the polarized beam to replacement target stations for 1BT1 and 4BT1; an appropriate design for beam line IB' was prepared.Beam line 2C has been tuned for four energies from 70 to 110 MeV and 6 x 6 mm2 spots have been obtained. For beam line 4A a new tune has been developed to provide an achromatic double waist just upstream of FERFICON.Final twists were given to the beam line 4B twister design by the addition of a sixth quadrupole and the decision to mount the whole device on a support twistable about the beam axis. In connection with studies of a possible proton hall expansion a number of new configurations for beam line 4A were in­vestigated in order to give two target locations, one a replacement 4BT1, the other a replacement 4C. Several schemes for aseparate beam line 5 to feed the MRS via a twister were also studied.On the M9 channel the installation of the RF separator resulted in the expected factor 2 increase in intensity. An intensive study of the Mil channel optics is under way and is revealing interesting effects as far upstream as the septum. One sextupole will be moved upstream of B2 in an effort to reduce the aberrations and beam spot size. The use of the M13 channel with the QQD spectrometer required some upgrading, including the installation of two extra sextupoles. Then two dipoles have been realigned to eliminate a substantial mis-steering effect at the QQD target. The M15 surface muon channel design has been modified to include a vertical section to ground level. The final version should yield a flux of 106/s within 2-3 cm2 (FWHM).In beam line diagnostics a comprehensive cross-calibration and sensitivity check was carried out on various beam line 1 monitors up to 1AT1. The signal distribution system to counting rooms was reconfigured'. Work is also reported on the target protect monitors, the 1AT1 air ion chamber, the beam line 4A SEM profile and total current monitors, and on multiwire proportional chambers for beam line IB and M13. Of particular interest is the successful operation of a gas-filled split- plate chamber for low intensity beams in beam line 4B.Computing services report continued expansion in the asynchronous links to the UBC Comput­ing Centre, there now being a total of 47 circuits. Multiplexing was eliminated from 28 of the circuits, raising the transmission speed from MTS to >4800 bd on all lines.With the installation of PACX many of the terminals may communicate with either MTS or the VAX. There have been various software developments, including a new set of device drivers, a new contour plotting code, the "latest" version of TRANSPORT, and the perennial project of upgrading REVMOC.Effort has also gone into improving graphics capabilities, particularly on the VAX. Fibre optics and coax cables for the high-speed link to UBC have been purchased and installed.In Kaon Factory affairs a Steering Committee has been set up to co-ordinate the prepara­tion of a proposal. Working Panels have been110formed to deal with specific topics. A number of specimen experimental proposals have been submitted to the Initial Programme Working Panel and are helping to crystallize thinking on the experimental facilities and beam properties required. Present thinking is to provide low, medium and high energy (4 GeV) kaon lines in a large new hall, each based on a dedicated proton line fed on a time-shared basis at several hertz. The most Important sources of pion contamination in kaon channels now seem to have been identi­fied and new channels are being designed to suppress the impurities. Neutrino beam designs are also being studied, a possible route being down the eastern site boundary. The results of the K" and "p production experiment have now been analysed and sub­mitted for publication.Accelerator feasibility studies have continued on two options to produce 100 uA currents at 15 GeV - a rapid-cycling synchro­tron and a two-stage superconducting ring cyclotron. In these studies we have bene­fited considerably from the ideas and advice of a number of consultants - Andris Faltens, Werner Joho, Takeshi Katayama and Lee Teng. For a 30 Hz synchrotron 770,000 TRIUMF bunches have to be accumulated for each acceleration cycle. Attention has therefore been concentrated on pulsed extraction from TRIUMF and the synchrotron injection process. For the latter a separate dc accumulator ring is recommended, to be mounted in the same tunnel with the synchrotron proper and a "superferric" dc stretcher ring. By running the accumulator at twice the TRIUMF RF frequency and interleaving the injected bunches their density could be doubled and the radius kept to 80 m.Beam transfer between TRIUMF and the accumu­lator could be accomplished using protons, neutral hydrogen atoms or H- ions. Feasible schemes have been developed for each species, though H~ ions would undoubtedly be the most straightforward if injection into the accumulator were the only consideration. Two schemes have been considered for H“ injec­tion. One minimizes multiple scattering in the stripping foil but requires a kicker mag­net repetition rate 10,000 times higher than those of existing kickers. Such a rate would require a novel power supply, but it appears that a vacuum tube exists which would make this development possible. Nevertheless the second scheme may be preferable; this requires a much lower kicker repetition rate,at the expense of more multiple scattering and a larger magnet aperture.Pulsed extraction of H“ ions from TRIUMF would involve four steps: turn compaction to ~100 turns/in., pulsed vertical deflection, horizontal separation from the circulating beam using an electrostatic septum and final­ly steering out via a magnetic channel. Turn compaction can be accomplished either by lowering the accelerating voltage locally, or by perturbing the average magnetic field.The RF method has proved to give much better matching to the longitudinal phase space ac­ceptance of the synchrotron. Two schemes have been proposed for its implementation, one in­volving modifications to the existing dees, the other the addition of novel decelerating cavities in the form of coaxial lines. Another approach would be to build a separate 430 MeV storage and compaction ring (TRIST0R).The CANUCK superconducting cyclotron option envisages 15-sector 3.5 GeV and 42-sector 15 GeV isochronous ring cyclotrons operating in series. With cw operation at a multiple of the TRIUMF frequency and good turn separation injection will be trivial. Their feasibility depends on designing practical superconduct­ing coils, maintaining isochronism and focus­ing to the highest energies, crossing various resonances without enlarging the beam too much, and extracting it efficiently. Cryo- genically realistic coil designs for the high energy cyclotrons have been produced and are being used as the basis for new magnetic field and orbit computations. The fields show good isochronism and real axial focusing over the full energy ranges of both machines. The effects of magnetic gullies outside the coil are also being studied and appear promising.Resonance crossing studies have been carried out on the old 30-sector 8.6 GeV field, but should be representative of the situation for the higher energy designs. Radial imperfec­tion resonances should be satisfied by toler­ances similar to those for TRIUMF (0.3 G during assembly and ten times better using trim coils). The lowest order intrinsic resonance (30/3) doubled the radial emittance, but can be reduced by adjusting the sextupole field component d 2B 3Q/dr2. For extraction it was found that the vr=12 resonance could be excited sufficiently by a 12th harmonic imperfection to provide a clear 0.8 mm wide beam-free region for a septum - sufficient for clean extraction of the scaled TRIUMF beam emittance.IllBEAM DEVELOPMENTCyclotronDepolarizationThe depolarization produced by crossing the 3.796y = 6-vz resonance at 467 MeV is ex­pected to depend on the square of the verti­cal betatron amplitude. Since the vertical motion in the central region is not adiabatic it was possible to use one of the correction plates (CP31) to introduce a controlled coherent component of up to 3.3 mm to check this dependence. The incoherent amplitude was about 2.5 mm.The polarization was measured at 482 MeV first as a function of the coherent ampli­tude. The stripping foil extended from top to bottom of the circulating beam and thus sampled all heights. The coherent amplitude was altered by CP31 and the resulting mean polarization is shown in Fig. 98. It con­firms that the depolarization increases with the square of the amplitude. The error bars are not statistical but reflect variations in source and cyclotron conditions.The amplitude dependence of the depolariza­tion was also confirmed by measuring the change in polarization across the resonance for a specially selected low emittance beam. The depolarization was found to be <1% (spin up) and <4% (spin down), compared to the 5- 10% observed with beams of regular emittance. It should be noted that there is longstand­ing evidence of ~5% polarization drop-off from the core to the edge of the beam at all extracted beam energies.Beam height changes induced by Bz harmonic coilsFor some time we have observed that powering certain harmonic coil sets in the Bz mode to control radial centring of the orbits also alters the vertical position of the beam.The latter is determined by horizontal field components and the strength of the vertical focusing forces. The 5-finger probe HE1 was used to measure the change in beam height resulting from the HC10 set of windings powered in the first harmonic Bz mode. An example of the height change is given in Fig. 99.The measured amplitude and phase of the beam shift in the radial direction agreed with that expected from the magnetic fieldCP 31 ( D A C )Fig. 98. Average proton polarization at 482 MeV as a function of the coherent beta­tron amplitude, showing the expected quadratic dependence.surveys, so it was unlikely that a wiring error had occurred. The windings on the upper and lower surfaces of the vacuum tank were inspected for geometric or magnetic differences. Although several were found their effects would be more pronounced at the inner or outer radii of the coil set, 220 in. and 246 in., and moreover would probably have a longer wavelength than the 10 in. observed.Computer simulations using our equilibrium orbit code CYCLOP have showed that the effect can be understood in terms of a complete field description, incorporating the harmon­ics of Bz, Br, Bq and 3Bz/3z. The superim­posed Bz field from the harmonic coil pro­duces radial perturbations in the orbits within its region of influence. In portions of this region, where there are large gradi­ents in radial field, 3Br/3r, the perturbed orbit will experience a different horizontal field and take up a different vertical position. The magnitude of the vertical movement will depend not only on the ampere- turns in the coil and the magnitude of 9Br(r,9)/3r but also on the relative phase of the first harmonic Bz and the harmonics of 3Br/3r. One expects a change in the average height Az0 and also in the modula­tion of Az(9). The latter, however, tends to be smaller since the nth harmonic amplitude Azn is inversely proportional to n2-v2 wherev2 » 0.04 ■+ 0.10. z112Fig. 99. Comparison of observed changes in vertical beam position for HC10 powered at 1000 At with a phase of 240°, and those calculated from CYCLOP on the HE1 probe.Figure 99 shows that there is good agreement between the measurements and the prediction of CYCLOP over much of the radial range. The calculations are based on field data from the 1973/74 survey; the actual field may be dif­ferent due to changes in trim coil settings, addition of new components and the aging of the magnet.If necessary the mean change in height ("z) may be compensated by a Br trim coil. At one desired azimuth the vertical direction may be controlled using a harmonic coil.Primary beam lines Beam line 1ADevelopment has continued of tunes to provide circular beam spots at both the 1AT1 and 1AT2 target locations regardless of the polarity of quadrupole 1AQ9. This is necessary because 1AQ9 - located immediately down­stream of 1AT1 - is run vertically focusing for tt+ operation of the Mil channel and hori­zontally focusing for it-  operation. The effect of this quadrupole upon the primary line tune is compensated by adjustment of quadrupoles 1AQ10-13. Were this not done, unacceptably high spills would occur near 1AQ11. It was necessary to redevelop the tune for beam line 1A because quadrupoles 1AQ12 and 1AQ13 were replaced with radiation- hard versions during the September shutdown.A 500 MeV tune has been developed which pro­duces a 2 mm x 3 mm FWHM spot at 1AT2 for ir+ operation of Mil and a 3 mm x 2 mm FWHM spot during it” operation. Beam spills and low changeover from tt -*- it- ■+• tt+ operation pro­ceeds smoothly.High Z targets at 1AT1. The use of thick copper or tungsten targets at 1AT1 would provide higher fluxes for the Mil and M13 channels. At the same time beam spill down­stream of 1AT1 would be expected to increase. The program REVM0C has been used to predict what spill might be anticipated. Beam spills between 1AT1 and 1AT2 were compared for 3 mm C, 10 mm C, 3 mm water-cooled Cu and 1 mm W targets at 1AT1. The results showed that un­acceptable increases in beam spill were to be expected downstream of 1AQ9 for the Cu and W targets.Beam line 2COperational tunes have been established for the four fixed strippers presently installed, corresponding to energies of 70, 72.5, 100 and 110 MeV, respectively, for the zero bend channel. For each energy, it has been demon­strated that a small (6 mm x 6 mm) spot can be obtained on the profile monitor immediately upstream of the production target. Quadru­pole detuning measurements were made for the 70 and 100 MeV tunes to provide information about the poorly known phase space configura­tions of the beam after extraction from the cyclotron. For this work typically ^1 pA was extracted down beam line 2C out of a circu­lating current of ~100 pA in the cyclotron. This operation had no effect on other users, except at 110 MeV, where the beam in the cyclotron was too low to be reached by the 2C stripper. The beam can be raised using Br trim coil #25, although this causes an increased beam spill along beam line 1A which must then be retuned.Beam line 4B twisterThe 1981 annual report described the design of a five-quadrupole twister which would allow operation at the MRS (4BT2) target under con­ditions ofa) achromatic beam,b) horizontally dispersed beam,c) vertically dispersed beam,d) any of the above with a solenoid installed upstream of 4BT1.In early 1982 K.L. Brown suggested that a six-quadrupole twister might be more suitable in that such a system could be a unit section. (A unit section 5-quadrupole twister has been designed but the experimen­tal configuration and the available quadru­poles do not allow its installation.) It is113planned to Install such a 6-quadrupole twister (suitably modified to satisfy experi­mental requirements) between target locations 4BT1 and 4BT2. This choice means that the angular dispersion at 4BT2 is significantly reduced compared to the 5-quadrupole twister, whose overall transfer matrix was equivalent to a thin lens. The use of the unit-section 6-quadrupole twister reduces the angular dis­persion at 4BT2 by a factor of ten.Following the installation of the 6-quadru­pole twister in early 1983, the MRS will be used for some (p,2p) experiments. These require beam line tunes in which the disper­sion varies from 3 cm/% to 10 cm/%. In addi­tion a |D/M| > 0 is required. In order to meet both requirements, it was found neces­sary to add one quadrupole to the doublet up­stream of 4BT1. As presently envisaged, the reconfigured beam line 4B will be as shown in Fig. 100 below.Reconfiguration o f low intensity proton linesThe beam lines available for proton experi­ments (IB, 4A and 4B) suffer from various limitations. For instance the space for ex­periments on beam line IB is somewhat limited and conflicts can arise with experiments on M13. In the proton area experiments cannot be set up on beam line 4B when beam is run in beam line 4A - and vice-versa. In order to solve these and other problems a number of suggestions for new or modified proton lines have been made and studied during the year.Fig. 100. Six quadrupole twister for beam line 4B.These include modified forms of beam line 4A to feed a proton hall extension, a new beam line 5 as a dedicated line to the MRS, and a replacement for beam line IB to supply a new south hall.a) Beam line 4A reconfiguredOne possibility would be an "extended 4A", continuing the 4VB1-4AB2 section in a straight line to the west; this would simply translate the double waist at the SFU loca­tion to a target location near the existing west wall of the proton hall. Alternatively, a "shifted 4A" version (Fig. 101) would run parallel to the north wall of the hall. Experiments would then be run in an extension at the west end of the experimental area.b) Beam line 5With this proposal a new beam line would feed the proton experimental hall, allowing its use simultaneously with beam line 4A. One version of this line is shown in Fig. 102.The layout shown requires no changes to the existing beam line 4B or experimental equip­ment from 4BT1 onwards. Design of a line feeding beam line 4B from extraction port 5 is complicated by the fact that the 4BT1-4BT2 separation must be kept constant because of the beam twister to be installed between these locations. Also it is necessary to be able to produce a horizontal beam magnifica­tion and dispersion at 4BT1 suitable for twisting into the vertical plane at 4BT2.The line labelled beam line 5(a) in Fig. 102 would require that the beam dump be moved. Since this would interfere with the proton hall extension referred to above, it was not considered further. Two versions of beamFig. 101. Beam line 4A redesigned to serve the proton hall extension.114Fig. 102. Possible beam line 5 designs to serve the twister and MRS.Fig. 103. Split beam arrangement for a south hall.line 5(b) were investigated. Each requires a (non-standard) combination magnet to direct stripped beam in a westerly direction. The layout sketched in Fig. 102 would utilize three conventional 45° dipoles. An alterna­tive layout would use two 90° superconducting dipoles in the vault and a conventional 45° dipole in the proton hall. Both configura­tions have been shown to provide the approp­riate beam conditions at the 4BT1 target. An important point is that space is available for the installation of a solenoid somewhere between the extraction point and the last dipole, allowing the production of a longi­tudinally polarized proton beam.c) Beam line IB' to a south hallSeveral concepts have been considered in order to provide replacements fora) Beam line IB, with more experimental spaceb) the 4BT1 target positionc) the neutron beams previously on beam line 4AThe initial concept was for a simple mirror image of beam line IB. While optics calcula­tions showed that this would be feasible, it did not satisfy all the experimental require­ments. The line was therefore redesigned to allow neutron beams to be taken off at thesecond bend, a third dipole being added to clear higher intensity proton beams (<10 pA) into a special beam stop. The arrangement within the south hall is shown in Fig. 103.An additional possibility - also illustrated in Fig. 103 - is to feed the new line via a septum and split beam. This scheme, whose feasibility was demonstrated experimentally in 1981, uses a toothed stripping foil to produce a two-component beam in beam line 1A. Two completely separated spots are produced at the septum, which then directs the south­erly component (weak unpolarized or polar­ized) down beam line IB', while the northerly component (main unpolarized or vacant) con­tinues down beam line 1A. With this arrange­ment experiments could be run in the south hall during both polarized and high intensity unpolarized operation.To provide a horizontal focus at the septum, just downstream of the vault dipole 1VB1, a new beam line 1A tune is required, with the polarities of Ql, Q2 and Q3 reversed. The use of a toothed stripping foil with a 5 mm gap then results in two spots at the septum cleanly separated by 9 mm. The 1BVB2 dipole would be completely removed from beam line 1A, while the triplet 1AQ4-6 would be shifted ~4 m downstream. Retuning quadrupoles 1AQ4-8 would provide beam properties at 1AT1 almost identical to those available now.Secondary channels M9 channelThe dc separator has been replaced by the RF separator. Measurements have confirmed that the intensity of 77 MeV/c cloud muons has in­creased by a factor 2. The pion and electron contaminations are a few per cent and can possibly be improved.M11 channelWith increasing experimental demand for this channel, intensive studies of the higher- order optics of the line began in mid-year using the programs RAYTRACE and REVMOC. This has been necessary because the beam spots observed are some three to five times larger than those predicted by TRANSPORT.RAYTRACE was initially used to trace particles through the measured fields of the first two elements of the channel (quadrupole 1AQ9 and septum 11S1). This study showed that particles of the momentum for which the channel is tuned exit from the septum some 2-3 cm off axis and diverge from the central trajectory. Quadrupole 1AQ9 must be tuned ~20% higher than the TRANSPORT value in order that particles of the nominal momentum exit the septum parallel to the optic axis of the channel. A short experimental run in November indicated that a 12% increase in the 1AQ9 setting resulted in a 20% increase in flux at the end of the channel. Time did not, however, permit variation of the septum or 11B1 setting nor did it allow an investi­gation of the beam spot.REVMOC studies indicate general agreement with TRANSPORT as to first- and second-order matrix elements. Third-order terms coupling horizontal position at the final focus to momentum and horizontal and vertical angles at the target are observed. REVMOC predicts the final beam spot FWHM to be of the order of 1.5 cm to 2 cm. This prediction is some­what smaller than the observed 3 cm FWHM. The experimental observations, however, were made with 1AQ9 tuned to its nominal value rather than that required from the RAYTRACE study. Retuning of 1AQ9 may lead to a reduction of the discrepancy between the two numbers.This will be attempted as soon as possible.Regardless, REVMOC studies indicate that the original design goals cannot be met. A further TRANSPORT/REVMOC study has shown that ~75% of the beam (at full solid angle andmomentum acceptance) can be directed into a 1 cm diameter spot with a small modification to the channel. This requires that the last sextupole