MASTER January—December 1984 Clinton P

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DISCLAIMER LA-10429-PR This report was prepared as an account of work sponsored by an agency of the United States Progress Report Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- UC-28 bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- Issued: Aprii 1985 ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom- mendation, or favoring by the United States Government or any agency thereof. The views and opinions uf authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Progress at LAUVSPF MASTER January—December 1984 Clinton P. Anderson Meson Physics Facility

Editor LA—10429-PR

John C. Allred DE85 015365

Scientific Editorial Board

Olin B. van Dyck Richard L. Hutson Mario E. Schillaci

Production

Beverly H. Taliey Margaret Pinyan Laura Schreffler Chris Weaver

ABSTRACT

Progress at LAMPF is the annual progress report of the MP Division of the Los Alamos National Laboratory. The report includes brief reports on research done at LAMPF by researchers from other institutions and Los Alamos divisions.

Los Alamos National Laboratory Los Alamos, New Mexico 87545 FOREWORD

The past rear was one of unsurpassed achievements in terms of tiic research program, improvements to the facility, and planning for i he future. The facility was host to 389 researchers from % institutions; 69 experiments received beam time and 33 were completed. A mong the latter were a number of major experiments, including rare muon decay, parity nonconservation in pp scattering, spin observables in small-angle pp scattering with polarized beam and polarized target, the unambiguous observation ofr\ production, and the first cross-section determination for the scattering of clear n-neutrinos by electrons. Improvements to the facility include extenshe preparation for providing beam to the Proton Storage Ring. These improvements encompass a high-intensity H~ ion source and injector, a more sophisticated low-energy beam-transport system, und a complete rebuilding of the switchyard. In addition, plans and components were prepared for a complete rebuilding of the beam-stop area. This latter effort will not only provide replacement of components that have deteriorated but will reduce off site radiation levels and provide easier access lor isotope-production and radiation-effects studies. Also, during this past year the Clamshell spectrometer was commissioned and began operation. Perhaps the most dramatic progress was made toward assuring future high levels of accomplish- ment in nuclear science and derivative technologies. This is important to national technological goals and to the vigor and vitality of Los Alamos, one of this nation's crucial national-security laboratories. Even with all the foreseeable improvements to LAMPF and the other meson factories in the world, it is highly probable that these will cease to fulfill their function by the middle of the next decade. Just as the meson factories were needed to bring meson probes and meson degrees of freedom into the study of nuclear science, so is it now necessary to bring kaon probes and quark and gluon a'pgrees of freedom to bear if progress in nuclear science is to continue at a level commensurate with defense and industrial needs and if it is to attract to this field some of the best minds in our society. The past year saw the first-phase culmination of the work of scores of scientists, over a number of years, toward identifying the next stage in the exploration of nuclear and particle physics at intermediate energies. "A Proposal to Extend the Intensity Frontier of Nuclear and Particle Physics to 45 GeV (LAMPFII)" has been prepared. We believe this initiative t" be cntciolly important if we are to maintain 'he knowledge base and people base required to advance nuclear science. We reproduce the Executive Summary of this proposal in Sec. V. Finally, it is important to recognize that the members of the LAMPF l.'scrs Group. Inc. (Ll'GI), having participated strongly in developing the LA MPFII proposal, are solidly behind this approach to the study of nuclear science. A letter from the L UGI Board of Directors sums up the attitude of the LAMPF Users toward L4MPFII; it is reprinted as Appendix A. Also, the management of Los Alamos National Laboratory recognizes the importance of this initiative and gives it their highest priority in the realm of basic research.

Louis Rosen Director of LAMPF

IV CONTENTS

EXPERIMENTAL AREAS x

LAMPF ORGANIZATIONAL CHART x»

LAMPF NEWS 1

LAMPF USERS GROUP 7 Eighteenth Annual Meeting 7 Committees 7 Working Groups Chairmen 9 Minutes 9 Visitors Center 11 Nucleon Physics Laboratory Upgrade Working Group Meeting 12

RESEARCH 17 Nuclear and Particle Physics • EXPERIMENT 792 — Measurement of Parity Nonconservation in the p"p and pd Total Cross Sections at 800 MeV 17

z • EXPERIMENT 748 — Measurement of (JWn/Mp) for 2" Transitions in T = 1 Nuclei 20 • EXPERIMENT 797 — Exciiation of Giant Resonances and Low-Lying Collective States in 90Zr and 11BSn by n* Inelastic Scattering 22 • EXPERIMENT 809 - Study of (n , p) and (n , p) Reactions with EPICS 24 • EXPERIMENT 826 — Mass Dependence of Nonanalog Pion Double-Charge-Exchange Excitation Functions 26

• EXPERIMENT 583u — Measurement of ALL in the Coulomb-Nuclear Interference Region at 650 and 800 MeV 28 • EXPERIMENT 685 — Measurement of Third-Order Spin Observables for Elastic pp — pd Scattering at 800 MeV 30

• EXPERIMENT 709 — Measurement of Am and Ass for pp Elastic Scattering in the Coulomb-Nuclear Interference Region at 650 and 800 MeV 30 « EXPERIMENT 741 — 500-MeV Nuclaon Scattering and the European Muon Collaboration Effect 33

• EXPERIMENT 790 — Measurement of ANN and ALL for the pp — dn* Reaction at 650 and 800 MeV 35 • EXPERIMENT 523-Pion Single Charge Exchange on 14C 37 • EXPERIMENT 401 - Angular Distributions for the 15N(n\n°)15O Reaction to the Isobaric-Analog State at 100 and 290 MeV 39 V • EXPERIMENT 77S — Study of the 16O(n*,n°p) Reaction 41 • EXPERIMENT 814 - n'-Nuclear Elastic Scattering from Nickel and Tin Isotopes at Energies. Between 30 and 80 MeV 45 « EXPERIMENT 850 — Low-Energy Pion Single Charge Exchange 47

» EXPERIMENT 884 — Pion-Nucleus Double Charge Exchange at Low Energies ... 49 • EXPERIMENT 225 —A, Study of Neutrino-Electron Elastic Scattering 51 • EXPERIMENT 455 - High-Precision Muon Decay 59 • EXPERIMENT 750 —Inclusive Pion Double Charge Exchange in "He 61 • EXPERIMENT so4 — Measurement of the Asymmetry Parameter in rt + p - Y + n Using a Transverse Polarized Target 63 • EXPERIMENT 825 — Investigation of the WA Interaction Through nd • pn"n . ... 70

• EXPERIMENT 336 — Studios of the Spin Dependence of pjp - nX 72 • EXPERIMENT H52 — Measurements of (n ,r\) Reactions on Nuclear Targets to Study the Production and Interaction of n. Mesons with Nuclei 74 • EXPERIMENTS 400/455.726. AND 6i8 —Crystal Box Experiments 77 • EXPERIMENT 529 — Muon Capture in 3He 83 An Improved Search for u - ey 84 Atomic and Molecular Physics Atomic Physics Using the 800-MeV H Beam 87 • EXPERIMENT 536 — A Study of the Effects of Very Strong Eiectric Fields on the Structure of the H Ion • EXPERIMENT 587 — Fundamental Experiments with Relativistic Hydrogen Atoms: Exploratory Work • EXPERIMENT 727 — Experimental Investigation of Muon-Catalyzed dt Fusion ... 89 Prediction of Ortho- and Para-Deuterium Effects in Muon-Catalyzed Fusion 93 An Emitter-Coupled Logic Router for Multihit Experiments 95

Materials Science

• EXPERIMENT 499 — Muon Longitudinal and Transverse Relaxation Studies in Systems with Random Exchange 99 « EXPERIMENT 571— Muon-Spin-Rotation Studies of Dilute Magnetic Alloys 104 -» EXPERIMENT 639-Muon Spin Rotation in Selected Magnetic Oxides 105

• EXPERIMENT 640 —Holmium-lon Dynamics in HoxLu, xRh4BA 108 • EXPERIMENT 842 — Muon-Spin-Relaxation Studies of Itinerant Magnets and Heavy-Fermion Superconductors 112

VI Muon-Spin-Relaxation Dilution Refrigerator 113 Experimental Study of Muon Beam Chopping for Muon-Soin-Relaxation Experiments 114

• EXPERIMENT 787 — Muon Channeling for Solid-State Physics Information 116 Calculation of Displacement and Helium Production at the LAMPF Irradiation Facility 118 Measured Radiation Environment at the LAMPF Irradiation Facility 121 A Study of Defects Produced in Tungsten by 800-MeV Protons Using Field Ion Microscopy 121 Biomadical Research and Instrumentation Radiobioiogy of Uitrascft X Rays , 123 Instrumentation 124 Nuclear Chemistry

• EXPERIMENT 308 — Direct Mass Measurements in the Light Neutron-Rich Region Using a Combined Energy and Time-of-Flight Technique 125 Masses of Ground-State Baryons Calculated with a Nontopological Soiiton Model 129 Distorted-Wave Impulse Approximation Predictions for Pionic n Production 3He(n ,n.)3H 131 • EXPERIMENT 691 — Production of Long-Lived Cosmogenic Nuclides with High-Energy Beam-Stop Neutrons 133

Radioisotope Production Isotope Production and Separation , 139 Radiopharmaceutical Labeling Research 145

Theory Unified Analysis of Pion Single- and Double-Charge-Exchange Scattering in the Resonance Region 151

A33 Dynamics in Pion Double Charge Exchange 151 Toroidal Bag Nuclei and Anomalons 152 Picn Charge Exchange from Oriented, Deformed Nuclei 152 On Muon Decay in Left-Right Symmetric Electroweak Models 154 Report of the T-5 Theoretical Group 166 MP-Division Publications 173

VII INSTRUMENTATION AND COMPUTING 187 Clamshell Spectrometer 187 Time-of-Flight Isochronous Spectrometer 189 • EXrIZRIMENT 7j2 — A Low-Pressure, Multistep, Multiwire Proportional Counter for the Time-of-Fiight Isochronous Spectrometer 192 EPICS and HRS 196 Data-Analysis Center 202 Expert Magnet Design Program 203 Magnet Mapper 203

STATUS OF LAMPF II 205 Executive Summary 205 Scientific and Technical Summary 207

FACILITY DEVELOPMENT 215 LAMPF Upgrade for the Proton Storage Ring 215 Central Control Computer 224 Target-Cell and Beam-Stop Replacements 224 Upgrade of the A-6 TargetjBeam Stop 226

ACCELERATOR OPERATIONS 227

MILESTONES 229

APPENDIX A Letter from LAMPF Users Group Supporting LAMPF II 233 APPENDIX B Experiments Run December 6, 1983—October 22,1984 235 APPENDIX C New Proposals During 1984 241 APPENDIX D Visitors to LAMPF During 1984. 253

INFORMATION FOR CONTRIBUTORS 259

Vlll EXPERIMENTAL AREAS

Primary Beam Lines in Experimental Areas

Line A — Main Beam Line for Pion and Muon Channels Line B — Neutron and Proton Beams and Nuclear Chemistry Facility Line C — High-Resolution Proton Spectrometer Lines D.E WNR — Weapons Neutron Research Facility PSR — Proton Storage Ring In-Flight Neutrino Source

Experimental Beam Lines

Area A: BIO — Biomedical Pion and Muon Channel BSA — Beam Stop A EPICS — Energetic Pion Channel and Spectrometer IFF — Isotope Production Facility LEP — Low-Energy Pion Channel P1 — High-Energy Pion Channel REF — Radiation Effects Facility SMC —Stopped-Muon Channel TA-5 — Target A-5 TTA — Thin Target Area TOFI — Time-of-Flight Isochronous Spectrometer Neutrino Area

Area B — AB or Nucleon Physics Laboratory (NPL): BR — Neutrons and Protons EPB — External Proton Beam LB-NC — Line B, Nuclear Chemistry

Area C: CCH — Area C Control and Counting House HRS — High-Resolution Proton Spectrometer AREA B 10 20 30 1 I I meters

AREA C

SOTOPE PRODUCTION & RADIATION NEUTRINO EFFECTS EXPERIMENT TUNNEL

BEAM STOP

SERVICE BUILDING

BEAMS Protons - - - — H" PSR Proton Storage Ring — — — — Pions or Muons WNR Weapons Neutron Research Facility _.._.._ Neutrinos (v) HRS High-Resolution Spectrometer _ . _ . _ Neutrons (n) NPL Nucleon Physics Facility LEP Low-Energy Pion Channel SPECTROMETER p3 High-Energy Pion Channel SMC Stopped-Muon Channel EPICS Energetic Pion Channel and Spectrometer TOFI Time-of-Flight Isochronous Spectrometer

EXPERIMENTAL AREAS LINE E . LAMPF Director Assoc. Division Leader MP-Division Leader Chief ol Operations I.IIUIS HilH'll Assoc. Division Leader Deputy MP-Division Leader Experimental Areas

Accelerator Development LAMPF Scheduling Committee Committee Experimental Areas Development Committee /I i ihwrwu/t ( haimian P ( llit)ii'nihiit '. hiimt /- /. . \^rii.'\\, ( huintuin

Asst. Division Leader Facility Planning, Budget Control, 4 User Liaison J \ nnulhurv

Group MP-1 Group MP2 Asst Division Leader Asst. Division Leader Group MP-7 • Group MP-1 Electronic Instruments' Accelerator Operations Plant Maintenance and LAMPF Safety Ekperimental Arean I Electronic Instrjmenta- tion & Computer Systems Construction I tion & Computer Systems /'. ii l/i'llman /) H I- Ctn-hrun /. K AglH'H • /:' H\ Hoffman

Group MP-fl ' Group MP-II Group MP3 Asst. Division Leader Group MP 10 ' Group HPB Engineerinneering Support I | Accelerator SupSuppor| t A pplications-Oriented Users Safety Officer HHS & EPICS I Engineering Support Research A /) Hinh • I .; 1) Ualluic J. A llruilinirr /) R I- lochran R I. Boudrir . I. D Uu.sh

Group MP-14 Group MP-4 Group MP-13 LAMPF II Development Nuclesr & Particle Beam-Line Development Physics // I llm-wrn D /-.. Nuglr /) // l-'ltztlivdltl. -\i-Unj(

December 1984 LAMPF ORGANIZATIONAL CHART UKMPF NEWS

Three Polarized Targets Run Simultaneously!

Polarized target at HRS from the National Laboratory for High-Energy Physics (KEK) in Japan. Left to right are Kevin Jones (Los Alamos); Gianni Pauletta, Spokesman (UCLA/University of Texas at Austin); Nobi Tanaka. Spokesman (Los Alamos); Shigeru Ishimoto (KEK); Steven Greene (Los Alamos), Akira Masaike (Kyoto University), and Yuji Ohashi (UCLA).

1 PROGRESS AT LAMPF— 1984

Polarized target at P'-East. Left to right are Colin Seftor (George Washington University) and Hans Ziock, Jack Engelage, and Steve Ad-ian (UCLA). Other participating universities were Abilene Christian College and Catholic University. LAMPF NEWS

Polarized target at Line BR. Left to right are Mike Beddo (New Mexico State University), Ken Johnson (Argonne National Laboratory), and Lee Northcliffe (Texas A&M University). PROGRESS ATLAMPF—1984

• The Engineering Support Group, MP-8, has a new • As of November 1984, R. W. (Bob) Stokes was expert system for the design of bending magnet::. The made Assistant Division Leader for Plant Mainten- system (computer program EMD) queries the user for ance and Construction. design parameters and then furnishes a preliminary magnet design, including dimensions, power dissipa- • In November, three eminent Chinese physicians tion, and cost. Originally suggested by Dick Hutson, visited Bill McCabe and Danny Doss at LAMPF to MP-3, the system was programmed by Ann Aldridge discuss the use of hyperthermia for the treatment of of C-3, formerly of MP-"7. human brain tumors. McCabe and Doss developed this technique, which has been used previously in the » The LAMPF II report, entitled "A Proposal to United States in the treatment of cancer eye in cattle. Extend the Intensity Frontier of Nuclear and Particle Three Chinese patients, treated in Shanghai, have Physics to 45 GeV," is complete and will soon be responded well, with either stable or gradually distributed. diminishing tumors.

Physicians fro.n China visiting inventors Danny Doss and Bill McCabe- Shown in the photo, left to right, are McCabe, Doss, Kao Xiao-Tung, Zhu Yong-Hua, and Tsai Yen. LAMPF NEWS

• The second winner of the Louis Rosen Prize for October 29, 1984, at the Eighteenth Meeting of the outstanding thesis research at LAMPF is Leslie LAMPF Users Group, Inc. The prize consists of a Bland. The title of his thesis is "Forward-Angle Pion certificate and $1000. Inelastic Scattering." Bland was awarded the prize on

Charles Glashausser (Chairman of the LAMPF Users Group Board of Directors), Leslie Bland, and Louis Rosen. Bland, the recipient of the second Louis Rosen Prize, is presently Assistant Professor of Physics at Indiana University and continues his research at the Indiana University Cyclotron Facility (IUCF). More than 100 people have completed Ph.D. theses at LAMPF. LAMPF USERS GROUP

Eighteenth Annual Meeting Committees

The Eighteenth Annual Meeting of the LAMPF Board of Directors Users Group, Inc.. was held in Los Alamos on Octo- ber 9-30. 1984, with 207 attendees. Chairman The Board of Directors consists of a Secre- Charles Glashausser (Rutgers University) presided at tary/Treasurer and seven members elected by the the first session, which included a welcoming address LAMPF Users Group. Inc.. whose interests they by Gerald Garvey. Deputy Associate Director for represent and promote. They concern themselves Particle and Nuclear Physics, and a report on with LAMPF programs, policies, future plans, and LAMPF operations by Donald Hagerman. especially with how users are treated at LAMPF. ! In the afternoon session, conducted by incoming I sers should address problems and suggestions to Chairman Robert Redwine (MIT). Charles individual Board members. Giashausser gave the Annual Users Group Report. The Board also nominates new members to the which was followed by a presentation of the election Program Advisory Committee (PAC). results. Barry Preedom (University of South Caro- The 14S5 membership and term expiration dates lina) is the Chairman-Elect of the Board of Directors; are listed below. new members are George Burleson (New Mexico James Bradbury (Secretary/Treasurer) State University) and Donald Geesaman (Argonne Los Alamos National Laboratory). Terms Expiring in 1985 During the Tuesday afternoon session the LAMPF C juries Glashausser (Past Chairman) Status Report was presented by Louis Rosen. Direc- Rutgers I iniversity tor of LAMPF. Working group meetings were held the rest of the day. Peter D. Barnes The following talks were given during the meeting: ("arnegie-Mellon University "What is the Pion?" Wolfram Weise (University of John 1). Walccka Regensburg); Stanford I 'nivcrsity "Delta Dynamics in Nuclei." Flia/er Piaset/ky (Uni- Terms Expiring in 1986 versity of Tel Aviv); Robert Redwine (Chairman) "Inclusive 500-MeV Nudeon Scattering and the MIT EMC Effect." Thomas Carey (Los Alamos); "Search for Parity Violation in /T-LH./5-LD. Scatter- • ••• •;••.• I 'son ing at 800 McV." Vincent Yuan (Los Alamos); N i 'State LJnivcrsity "Quarkiei: Nuclear Physics from QCD!" Terrence I)'. -:.u Gcesaman Goldman (Los Alamos): Aiv ..ne Nationri Laboratory "Search for States Near ;Y/V Threshold." Gerald Ten. i Expiring in 1987 Smith. Chairman of Brookhaven Users Group Barn I 'reedom (Chairman-Elect) (Pennsylvania State University): University of South Carolina "Searching for Hidden Color Components of Nuclear Wave Functions with the Pior.-Nudeus Double Charge Exchange Reaction." Gerald Miller (Uni- Technical Advisory Panel versity of Washington): The Technical Advisory Panel (TAP) provides "LAMPF II." Henry A. Thiessen (Los Alamos): and technical recommendations to the Board of Directors "Strategic Defense Research at Los Alamos." Robert and LAMPF management about the development of Selden, Associate Director for Theoretical and experiment facilities and experiment support ac- Computational Physics (Los Alamos). tivities. The TAP has 12 members, appointed by the 8 PROGRESS ATLAMPf —1984

Board of Directors for 3-\ear staggered terms; the Terms Expiring in 1985 Chairman of the Board if Directors also serves as \ .an/ L. Gross TAP chairman. The TAP membership and term College of William & Mary expiration dates arc listed below. Barry Holstein Terms Extended into 1985 University of Massachusetts 1984 Billy E. Bonner Sheldon B. Kaufman Los Alamos Argonne National Laboratory 1984 Thomas J. Bowles Leonard S. Kisslinger Los Alamos Carnegie-Mellon University 1984 Gerald Dugan June L. Matthews Fermi relational Accelerator Laboratory MIT Terms Expiring in 1985 Daniel W. Milicr Indiana University Cyclotron Facility 1985 Donald Gccsamun Argonne National Laboratory Darragh Nagle Los Alamos 1985 Ka/uo Gotow Virginia Polytechnic Institute and Slate Bruce VerWest University Atlantic Richfield Company 1985 Christopher L. Morris Robert Lee Walker Tesuque. New Mexico Los Alamos Terms Expiring in 1986 1985 Thomas A. Romanowski David Axcn Ohio State University TRIUMF Terms Expiring in 1986 Barry Barish 1986 George R. Burleson California Institute of Technology New Mexico Siate University Dietrich Dehnhard 1986 Michael A. Oothoudt University of Minnesota Los Alamos Friedcr Lenz 1986 Gary Sanders SIN Los Alamos Harold M. Spinka. Jr. 1986 Charles A. Whitten Argonne National Laboratory UCLA V. Viola Indiana University LAMPF Program Advisory Committee Larry Zamick The Program Advisory Committee (PAC) consists Rutgers University of about 25 members appointed for staggered 3-year Terms Expiring in 1987 terms. Members advise the Director of LAMPF on EricG. Adclberger the priorities they deem appropriate for the commit- University of Washington ment of beam time and the allocation of resources for Gerard M. Crawlcy the development of experimental facilities. The PAC Michigan State University meets twice eacn year for 1 week during which time all new proposals that have been submitted at least 2 William R. Gibbs months before the meeting date are considered. Old Los Alamos proposals, and the priorities accorded to them, also WickC. Haxton mav be reviewed. Los Alamos LAMPF USERS GROUP 9

Stanley B. Kowalski Time-of-Flight Isochronous Spectrometer (TOFI) MIT Thomas Carey Los Alamos Philip G. Roos University of Maryland Computer Facilities James Amann Benjamin Zeidman Los Alamos Argonne National Laboratory Solid-State Physics and Materials Science Solid-State Physics and Materials Science Robert Brown Subcommittee Los Alamos Russell E. Walstedt, Chairman Muon-Spin Relaxation Bell Laboratories Mario Schillaci Los Alamos Carl McHargue Oak Ridge National Laboratory Low-Energy Pion Channel (LEP) Barry Ritchie Mary Beth Stearns Universitv of Maryland Arizona State University Stephen von Molnar IBM Wa'son Research Center Minutes Charles Allen Wert Board of Directors University of Illinois at Urbana The LAMPF Users Group, Inc. (LUGI), Board of Woi king Groups Chairmen Directors (BOD) met on February 17, May 25-27, and October 28-30, 1984. All meetings were chaired High-Resolution Spectrometer (HRS) by Charles Glashausser; selected topics of discussion Susan Seestrom-Morris are provided below. University of Minnesota Tiierc were 207 registrants for the 1984 Annual Neutrino Facilities Users Meeting, 83 from outside the Laboratory. The Thomas A. Romanowski papers presented at the meeting and the minutes cf Ohio State University the workshops are given in the Proceedings.' Stopped-Muon Channel (SMC) The Program Advisory Committee (PAC) met in Richard Hutson August 1984 and will meet again in February 1985. Los Alamos For these 2 sessions 78 new proposals were received. The breakdown follows. Nuclear Chemistry Larry Ussery HRS 23 Los Alamos EPICS 20 Energetic Pion Channel and Spectrometer (EPICS) LEP 12 John Zumbro Nuclear Chemistry 3 University of Pennsylvania NPL 3 1 SMC 4 High-Energy Pion Channel (P ) 1 William Briscoe P 3 George Washington University Biomed 2 Solid State Physics and Materials Science . 17 Nucleon Physics Laboratory (NPL) Miscellaneous 1 Upgrade/Medium-Resolution Spectrometer John McClelland Those PAC members whose terms usually expire Los Alamos at the end of 1984 will serv; at the February meeting; PROGRESS ATLAMPF—1984 new members for both the Technical Adviso: y Panel meetings the bulk of the lime was spent discussing (TAP) and the PAC will be recommended by the various proposed upgrades to LAMPF capabilities BOD at their meeting in March 1985. The summer during the next few years. These upgrades include meeting of the PAC" again will be the "overlap" • a nigh-intensity polarized ion source; meeting. • improvement at NPL, including a buncher, The 3OD selected Leslie Bland as the recipient of beam swinger, medium-resolution spectometer. the Louis Rosen Prize for 1984 for his thesis "For- spin prccessor. and reconfiguration of Area BR: ward-Angle Pion Inelastic Scattering." The award • a second-generation jt" spectrometer: was presented at the Annual Users Meeting. • the Crystal Box upgrade for rare-decay studies: The Users' lounge, located east of the Data- • a decay-in-flight neutrino source; and Acquisition Center, is now furnished and functional. • a helium-jet system coupled to an on-line mass Comments from the User community about addi- spectrometer. tions to improve its usefulness are welcome. A technical description, including detailed costing The BOD is concerned that some students may not and timetable, of the implementation of a high- be adequately covered with health insurance (acci- intensity polarized ion source has been prepared bv dent/sickness) while working at I AMPF. Insurance the LAMPF staff and sen; 10 DOE. The NPL im- possibilities at the Laboratory will be investigated provements were discussed in depth at a December and user input on this potentially serious problem is 1984 workshop. Design of the second-generation 7t" solicited. spectrometer and the Crystal Box upgrade are The LAMPF II proposal will be delivered to the proceeding and will be presented at the February Nuclear Science Advisory Committee (NSAC) and TAP meeting, as will the choice for location of the DOE in February 1985. At the suggestion of Louis proposed decay-in-flight neutrino source. Rosen, the BOD will write letters in support of Members of TAP have been assigned responsi- LAMPF II to the management at DOE and the bility for keeping track of the various proposed up- Laboratory as well as to members of NSAC. The grades and acting as liaison between the User com- Science Policy Advisory Committee, formed by the munity and LAMPF staff. Users may contact their BOD. provided valuable advice and significant writ- TAP representatives if they wish to discuss issues ing assistance in the preparation of the physics concerning the projects. The TAP members and their justification section of the proposal. respective project assignments are listed below. The following workshops are scheduled to be held NPL Upgrade at LAMPF. Barry Precdom and Cha !es Whitten Nuclear Physics Laboratory Upgrades Neutrinos December 17-18, 1984 Thomas Bowles and Thomas Romanowski Pion Double Charge Exchange Computers January 10-12. 1985 Dcnald Geesaman and Michael Oothoudt Dirac Approaches to Nuclear Physics Polarized Source January 31-February 2, 1985 Gerald Dugan Relativisiic Dynamics and Quarks in Nuclear n" Spectrometer II Physics (summer seminar scries) Christopher Morris and George Burleson June 3-14. 1985 Crystal Box II LAMPF II Workshops on Experiment Definition Gary Sanders anci Kazuo Golow To be scheduled

Technical Advisory Panel Reference 1. "Proceedings of the Eighteenth LAMPF Users The Technical Advisory Panel (TAP) met on Group Meeting." Los Alamos National Laboratory June I. 1984. and October 31, 1984. During both report LA-10370-C( 1985). LAIUPF USERS GROUP 11

Visitors Center

During this report pciiod, 44*3 research guests worked on LAMPF-related activities or participated in experiments at LAMPF; of these, 132 were foreign visitors. A total of 576 check-ins and 628 check-outs were processed by the Visitors Center.

LAMPF Users Group Membership Institutional Distribution Membership by Institutions Non-Laboratory 638 Los Alamos National Laboratory 177 National or Government Laboratories 79 177 Los Alamos National Laboratory IIS I !ni vorsi 1 les 329 TOT-XI. 815 Industry 39 Foreign 157 Fields of Interest * Hospitals 23 Naciearand Particle Physics 699 Nonaffiliated 11 Nuclear Chemistry 116 TOTAL. 815 Soiid Slate Physif. and Materials Science 167 Theory 178 Number of Institutions Biomedical and Biological Application^ 178 National or Government Laboratories 19 Weapons Neutron Research 143 U.S. Universities 101 Data Acquisition and Instrumentation 186 Industry 27 Administration. Coordination. Facilities. Foreign 79 Operations 58 Hospitals 20 Isotope Production 60 Nonaffiliaied 6 LAMPF II 469 TOTAL. 252 'These numbers do not add to total nicniivr:'.hip because of inullipk' intensls.

Regional Breakdown East Pennsylvania. New Jersey, Delaware. Waslrngton DC, Massachusetts, New York, Connecticut. Vermont, Rhode Island, New Hampshire, Maine 109 Midwest Ohio, Missouri, Kansas. Indiana, Wisconsin, Michigan, Illinois, North Dakota, South Dakota, Nebraska. Iowa. Minnesota 92 South Maryland. Virginia, Tennessee. Arkansas. West Virginia, Kentucky, North Carolina. Alabama. Mississippi, Louisiana, Georgia, Florida 65 Southwest, Mountain Montana. Idaho. Utah. Wyoming, Arizona. Colorado, New Mexico (excluding Los Alamos). Oklahoma, Texas 119 West Alaska. Hawaii. Nevada. Washington. Oregon, California 95 Foreign 158 Los Alamos National Laboratory 177 TOTAL 815 12 PROGRESS AT LAMF-F—1984

Nucleon Physics Laboratory Upgrade The goals of the workshop were to identify the Working Group Meeting physics impact of such a program and to define the experimental facility required to support it. Gary J. McClelland Love from the University of Georgia gave a review of nucleon charge-exchange reactions at intermediate The first meeting of the Nucleon Physics Labora- energies. He discussed the uniquely selective charac- tory (NPL) Upgrade Working Group was held at ter of these isovector reactions, which, when folded LAMPF on December 17-18, 1984. Approximately into the energy dependence of the interaction over 50 attendees representing 20 universities and na- the LAMPF energy range, would allow tuning of the tional laboratories participated in round table dis- probe to investigate details of nuclear structure a-id cussions of proposals to develop new facilities in reaction mechanisms, making LAMPF the premier Area B of LAMPF (Fig. 1). These proposals include the addition of a medium-resolution spectrometer (MRS) for(p.p') and («,/>) programs and a neutron time-of-tlight (NTOF) facility for (p.7i) reaction studies with flight paths up to 500 m.

FUTURE EXPANSION AREA

FE.NC.iNG

FK;I RK 1. Proposed modification of the NPL area. LAMPF USERS GROUP 13 facility for these programs. As a guideline, a draft of a tions arc in progress and a final design is expected by proposal for such a facility' was circulated before the February 1985. meeting. There was a general consensus on all major The minimal system for commissioning of the items contained in that proposal. Many refinements MRS was defined as a complete magnet system, a full and alternative suggestions were generated by the detector array including a focal-plane polarimeter, workshop and will be incorporated in a final proposal and some beam-line instrumentation. Additions to to be submitted to the LAMPF Program Advisory this would include a polarized target and second-arm Committee and Technical Advisory Panel in Febru- interface. It was felt desirable to make the MRS work ary 1985. That proposal will include the following in the (/?,/>') mode before attempting the (//,/)) work. highlights. Given existing shielding and the higher beam intensities possible in Line B, it may be best to lest the (n,p) feasibility in Area BR and then to develop the MRS (n,p) system at the EPB when the targeting ;••-:'• Harold Enge of MIT presented additional ion- shielding problems are better understood. In any optics calculations on the proposed QQDQQ spec- instance, it would be advantageous to be able to trometer (Fig. 2). Some problems associated with the move the MRS between EPB and Area BR between strong focusing of the quadrupoles were noted; how- run cycles, which would require a cable patch system ever, he felt they were nol serious in nature and could to a common counting house from the two areas. be corrected. A great deal of attention was paid to compatibility NTOF between nucleon-nucleon and nucleon-nucleus applications. In general, this spectrometer met the di- Several options for flight paths up to 500 m were verse needs of its many applications. Table I itemizes studied (Fig. 3). It should be possible to implement the important operational parameters of the MRS as one of these without excessive excavation or inter- agreed upon by the working group. Further calcula- ference with existing activities.

MOT TO SCALE

O 10 20

METER

NMR

QUADRUPOLE MAGNETS SCATTERING VOUADRUPOLE CHAMBER MAGNETS

FN;I KV 2. Schematic of the medium-resolution spectrometer (MRS). 14 PROGRESS AT LAMPF— 1984

T UJI.I- I. Desirable Operational Parameters for the Proposed Medium-Resolution Spectrometer atNPL. Energy resolution (at 800 MeV ».5 MeV over ± 20 MeV of acceptance (A£l — 10 msr) 5.0 .MeV over ±150 MeV of acceptance (\Sl - 15 msr) Solid angle 10-15 msr target area 25 cnr Momentum acceptance i20"-o Maximum momentum I.IGtV/c Angular resolution 2 nir Angular range 0-160° Overall length 9 tn Instrumentation Wire chamberchar s at focal plane for ray tracing Focal-plane polarimeter Front chambers for (n,p) application (large target area) Polarized target interface Second-arm interface Open-sided front quadrupoles for small-angle measurements

EXPERIMENTAL AREA C ' ' '- HIGH RESOLUTION PROTON SPECTROMETER

\ EXPERIMENTAL AREA B

NEUTRON FLIGHT PATH (H)

BEAM STOP A

NEUTRINO RESEARCH

EXPERIMENTAL AREA A

200 O 200 400 600 FEET .i i-'-r-i 0 30 100 150 METER

FIGURE 3. Neutron time-of-flight path extending from NPL area to end station. LAMPF USERS GROUP

It was suggested that three or four utility and patch ing, detectors, beam-line instrumentation, high- ports be available along the flight path for operation count-rate electronics systems, and software develop- from 50-500 m. The self-contained detector house ment. It was agreed that a LAMPF project manager and data-acquisition station should be portable to would be responsible for overview of all activities. allow for this option. Neutron detectors currently being developed by P Division for collaboration with User Facility MP Division on an experiment at the Indiana Uni- versity Cyclotron Facility (ICUF) would be usable for The Working Group recommended that a level of commissioning of this facility. These detectors permanent support for users be provided on the should be available in late 1986. This is also the NTOF and MRS (somewhat comparable to the user projected time for a 100-ns buncher on the polarized facilities provided for other large spectrometers, such injector producing the pulse-separated beam as dedicated instrumentation and counting houses). necessary for (p,n) measurements. The Working Group also foresaw an additional prob- Shielding between the MRS and NTOF areas in lem for the Program Advisory Commit- the EPB area was recommended so that work in one tee—scheduling facilities that compete for beam area can proceed while beam is delivered in the other. time, to allow experiments covering both nucleon- A beam swinger magnet system will be used to vary nucleon and nucleon-nuclear physics. the incident proton beam angle on target. The It was thought important to proceed as quickly as swinger and beam dump will reside in a shielded possible on both of these projects ir; order to take full crypt outside the EPB area. Suitable personnel safety advantage of the high-int°nsity polarized source systems will be incorporated to provide adequate planned for 1987-88, which will p!ay a vital role in protection along the neutron flight path. the programs being proposed.

University Participation Reference A large fraction of participating universities of- 1. J. B. McClelland, O. B. van Dyck. N. Tanaka, M. W. fered assistance for these projects in the form of McNaughton, and C. D. Goodman. "Development Plan for the Nucleon Physics Laboratory (NPL) Fa- design studies and fabrication of subsystems such as a cility at LAMPF," Los Alamos National Laboratory polarized-target interface, generalized second arm, report LA-10278-MS (1985). scattering chamber, vacuum systems, target shield- Nuclear and Particle Physics sensitivity for each run was determined from the correlation between transmission and intensity in that run. Correlations of transmission with position Measurement of Parity Nonconservation and polarization within the data also were studied, in the pp and pd Total Cross Sections a ; the\ confirmed the on-line measurements of at 800 MeV sensitivity to these variables. Run-by-run corrections to . !,• were made for each • Experiment 792 — EPB offending beam property. The final result for 1.8 "X L'niv. of Illinois, Los Alamos, Princeton I nir., Univ. of 10"' protons incident on the H:O target is.!, = (1.7 ± Maryland 3.3 ± 1.4) X 10 \ where the two error terms represent Spokesman: I' Yuan'I tin. ot ilhn<>i\/l.n\ Alamos) uncertainties because of statistical and systematic I'uilicipunts:./. D. Bo\\r,;an, R Carlini, R. H. Mischkc, contributions, respectively. The lead and no-target D. MacArthur, D. E. Sank: II. i'raitcnfcldcr, R, If. results, wit'i roughly one-third as many incident Harper, A. B McDonald, and R. I.. 1'aluga protons. a;c consistent with zero.

The goal of Exp. 792 is to search for parity viola- LH2 tion in the pp and pd total cross sections. In 1984 the experimental collaboration performed work Much effort was devoted to a careful analysis of the related to ;liree experimental targets: H;O. H:, November 1983 pp data. As a resu'.i of this analysis and IX an improved understanding and characterization of the sensitivities to beam systematics were achieved. The entire set of 150 data tapes was replayed, and H,0 systematic corrections were made for each beam

Final analysis of data taken with an H:O target pulse. : (Exp. 634) was completed and submitted for publica- The LH: experimental setup was similar to the 1 tion. The H;O d.ua were taken in preparation for one used in the H:O run. Improvements, however, doing the H, and D, measurements that followed. A allowed a better determination to be made of system- description of the experimental setup and technique atic error contributions to .-I,. Two multiwire pos- can be found in the !982 Progress at LAMPF and ition monitors (MWPMs) were added, which allowed Ref. 1. Data taken with a lead target and with no us for the first time to monitor both the size and target also were analyzed, with the results serving as a position of each beam pulse. A four-arm polarimeter test for unidentified systematic effects. used the LH: target as an analyzer to measure re- The analysis concentrated on identifying beam sidual transverse polarization in the beam. A second properties that could mimic true parity contributions polarimetcr was added with a target that con- to I, and quantitatively correct for these effects. tinuously scanned the beam profile for a circulating During ihe run. known amounts of position and polarization componcrt. The detectors of both polarization \anation were deliberately introduced polarimetcrs were scintillator-photodiodc combina- into the beam. The analysis determined sensitivities tions. The upstream ion chamber of the transmission of. I; to position and polarization from the observed measurement, as before, was used to measure in- efleet of these variations on transmission. Efforts to tensity variations. determine a sensitivity to intensity in this manner In addition, a second servo-feedback loop was were not successful because we had no way of varying added to the single loop used in the H:O run. In this the intensity uniquely. Therefore, after the data were way we were able to stabilize the beam in angle as taken all the runs were replayed and the intensity well as position. Error signals from both loops were 18 PROGRESS ATLAMPF—1984

TVBU I. Contributions, in pp Scattering, of Beam S>stematics to Ai.. The contributions to parity-nonconserving (PNC) and helicity-independent (HI) values are given. Contribution Systematic Effect PNC(X107) HI(X107)

Position -0.3 2.7 Intensity 0.8 -7.7 Size -0.1 0.2 Polarization <0.I <0.1 Circulating polarization 0.1 0.2 Ground loop 0.0 -0.6

linearly mixed in such a way as to maximally decou- for net transverse polarization and circulating ple one loop from 'he other. The position-sensitive polarization were made for each group of four pulses detectors within the loops were mounted on and each run, respectively. As with circulating precision translation stages, and beam position at polarization, ground-loop corrections were made on either end of the apparatus could be varied with 0.1- a run-by-run basis. The systematic corrections are mm accuracy. A third loop stabilized the beam pos- discussed in more detail. ition on a defining aperture 50 m upstream of the apparatus. Intensity Analyzed results of the experiment are given in Tabhs I and II. The experiment ran for equal time A special apparatus was used to determine the periods in two different operating coMigurations (N sensitivity of the helicity-correlated transmission Z and R) of the spin filter in the polarized source. In to intensity modulations. The apparatus consisted of both configurations protons exiting, t! : source were a set of stripper grids that could be moved in and out longitudinally polarized, but the spin directions for of the H" beam path synchronously to the 30-Hz the A and R configurations were opposite with re- helicity reversal. An H" ion traversing one of the spe<;i to the 10-G spin-flip field of Xhe source. Hence, grids would have a 10% chance ofbeing stripped of its the combination (A' — R)/2 cancels the effects of electrons. Positively charged protons remaining in helicity-independent systematics and is referred to as the beam after the stripping process were deflected the parity-nonconserving (PNC) signal. The com- from the final beam upon reaching our experimental bination ;/V+ R)/2 is a measure of helicity-independ- area. Hence, the grids produced a 10% modulation of ent (HI) systematic bias and is called the HI signal. beam intensity synchronous to the helicity reversal. In the analysis the measured transmission for each With the stripper grids positioned in the beam beam palsc was corrected for the contribution of path, data were taken as the dc intensity and size of systematic effects. Corrections were made for in- the beam were varied. An analysis of these runs tensity, position, and size. In addition, corrections indicates a dependence

TABI.F. II. Results for AL in pp Scattering. Parity-nonconserving (PNC) and helliciiy-indeiiendent (HI) results are given both before and after corrections fw systernatics are made.

PNC(X107) HI(X107) (Number of Runs) Uncorrected 3.0 ± 1.2 -5.0 ± 1.2 300 (152) Corrected 2.4 ± 1.1 0.2 ± 1.1 159 (152) RESEARCH—Nuclear and Particle Physics

cl/./dl = .!„ + .1,/ + •l4ai fa algorithm was unstable. Therefore, a different algorithm based on geometrical estimation was used. where / is the beam intensity and o, (a, ) is the width For extremely narrow beam widths (o s 0.9 mm), of the incoming beam in the horizontal (vertical) the primary beam-profile information resided on direction. The first three terms contributing to d'/.fcll only two wires, and simultaneous position and size most likely result From nonhnearhies in the detectors information could not be reliably extracted from the and electronics; the last two terms are consistent with profile. In these cases a correction for correlated 30- rccc mbination effects within the chambers. Hz size variation was not made. The magnitude of the omitted correction to .1, . determined from the Polarization majority of runs where size corrections arc valid, is estimated to be <5 X 10s per run. During the experiment, contributions from polarization systematics were minimized by locating the beam along the polarization s* mmelry axis (PSA) Circulating Polarization of ,he transmission detectors. To determine this axis A full scanning-polarimcter target scan took nearly tin transverse polarization was deliberately exag- 2 min to complete. Therefore, i; was not possible to gerated and the beam was moved (scanned) across determine individual pulsc-by-pulse corrections for IC1 and 1C2. The changes in /. measured during the circulating polarization. Corrections, instead, were scan, allowed a determination of both the PSA lo- made to each run based on a sum of all the scan data cation and the sensitivity of / to 30-Hz changes in taken during that run. transverse polarization. Because the data runs to measure / were taken with the beam positioned on the PSA. transverse polarization gives the smallest of Ground Loops all systematic corrections—a correction to.-l, of beam plots of uncorrectcd transmission vs various system- profile taken at the beginning of the run. An atic quantities show large correlations that are re- algorithm then calculated subsequent beam position moved with application of the corrections. Third, and size by Taylor expanding around the beginning- the x: value for the corrected result shows nearly a of-run value. Because of the narrowness of the beam factor of 2 improvement over that for the uncor- at the upstream MWPM (o = 1 to 3 mm), the original rected result. Finally, as can be seen from Table II, 20 PROGRESS AT LAMPF— 1984

the HI result is consistent with zero. The preliminary parity-violating result of the analysis is A, = (2.4 ± l.!)X 10"7.

LD2 In June/July of 1984, Exp. 792 ran for 3 weeks to measure parity violation in pd scattering. The setup was the same as that used in the earlier H, run. Accelerator problems during the run limited the number of data tapes thai could be taken to one-half the number taken during the H: run. However, because a greater percentage of the incident beam is scattered in deuterium, it is expected that the final sensitivity of the pd result will be comparable to that of the pp run. A preliminary analysis indicates a o value of .-I, that has an upper bound of several parts in ICT7.

References 1. R. W. Harper et al.. "Parity Nonconservation in Proton-Water Scattering at 1.5 GeV/c" (submitted to -11 3 5 7 Physical Review D). 2. V. Yuan. "Measurement of Parity Nonconservation Excitation Energy (MeV) in the Proton-Proton Total Cross Section at 800 MeV," in the Proceedings of the Eighteenth LAMPF Fici'RK 1. Spectra obtained for n~ scattering from Users Group Meeting, Los Alamos. New Mexico, -6Mg, "'Si, and 14S. The locations of the 2f states October 29-30, 1984 (to be published). are marked with arrows.

The data have been analyzed using the collective 2 model for the radial shapes of the form factors, bu' Measurement of (MJMp) for 2 Transitions in with different neutron and proton deformation T = 1 Nuclei parameters, p,, and (3,,. Distorted-wave impulse ap- • Experiment 748 — EPICS proximation (DWIA) calculations were normalized + Univ. of Minnesota, Univ. of Texas, Univ. of Pennsylvania, to both the K and iC data by separately adjusting p,, Los Alamos and p,,. The resulting transition densities were integrated to obtain mainx elements A/,, and A/,,. Spokesperson: S../. Scestrom-Morris (I 'nix. of Minnesota) The matrix elements resulting from this simple In this experiment we measured cross sections for analysis along with the matnx elements extracted : 7r* and 7i inelastic scattering to the 1\ levels in the from electromagnetic measurements' are displayed nuclei '"O. ::Ne. :"Mg. '"Si, and "S. The cross sections in Fig. 2. Also shown a^e previously reported results j: for "*O and ::Ne were measured using the EPICS for Ca (Ref. 3). Although the proton matrix ele- cooled-gas target. Data for all the solid targets were ments extracted from the analysis of the pion scatter- measured simultaneously using strip targets mounted ing data agiee well with those extracted from lifetime r in the incident pion h~am. Angular distributions measurements in the target nuclei, the n utron matrix elements extracted from pion scattering in the were measured for all targets between 9lab = 20 and 40" at an incident pion kinetic energy of T. = 180 target nuclei are systematically lower than those ob- MeV. Typical spectra are shown in Fig. 1. tained from lifetime measurements in the mirror RESEARCH—Nuclear and Particle Physics 21

7T+/TT EM 0.15

0.10

0.05 - *****

0.00 ====- =

-0.05 -

-OlO 12 16 20 24 z

FIGURE 3. Coulomb-mixing amplitudes as a func- FIGURE 2. Multipole matrix elements, M and p tion of Z. Mtt, extracted from pion scattering and electromagnetic matrix elements.

this Z dependence to fit the present data leads to nuclei. We find that the average ratio of M,,(l) ob- charge-dependent admixtures, y = 1.5 X 10~3 Z4/3, tained from electromagnetic measurements to that about twice the value predicted by Bohr and Mot- obtained from pion measurements is 1.02 ± 0.03, telson but much smaller than that predicted by Mac- 5 whereas the average ratio of Mp(— 1)/M,,(1) is 1.20 ± Donald. The sign of the predicted charge-dependent 0.05. Further, the discrepancy appears to be largest at mixing is such that proton matrix elements among large Z, indicating that it is not due to a renormaliza- the low-lying states are enhanced. tion of the isovector and isoscalar pieces of the pion- In summary, we have observed an apparent viola- nucleon interaction in the nucleus but must depend tion of charge independence in comparing multipoie upon the nuclear structure. matrix elements A/,,(l) extracted from pion inelastic This discrepancy can be understood if charge- scattering with A/,,(—1) obtained from lifetime dependent Coulomb-induced mixing in these nuclei measurements in mirror nuclei. The discrepancy is of is considered. If the differences observed between the same sign and has dependence on Z, but is larger theM,, measured in pion inelastic scattering and the than that expected from Coulomb mixing. Mr from mirror nucleus lifetime measurements are assumed to be due to Coulomb mixing, then our References present data can be used to experimentally determine the size of this effect. 1. A. M. Bernstein et al., Physical Rv\iew Letter: 49, When the wave functions of the nuclear ground 451(1982). state and the low-lying excited states have isovector 2. P. M. Endt and C. Van Der Leun, Nuclear Physics admixtures y induced by the Coulomb force, the A310, 1(1978). multipole matrix elements between the ground state 3. K. G. Boyer et al.. Physical Review C 24, 598 (1981). and the low-lying collective states will have additional isovector pieces that are due to this Coulomb 4. A. Bohr and B. R. Mottelson, Nuclear Structure mixing. The values of 7 extracted from the current (Benjamin. New York. 1969), Vols. 1 and 2. data are shown in Fig. 3. For self-conjugate nuclei, 5. W. M. MacDonald, Physical Review 100, 51 (1955), Bohr and Mottelson4 find that y scales as Z4/1. Using and 101,271 (1956). 22 PROGRESS AT LAMPF- -1984

Excitation of Giant Resonances and strengths of about 1.5 for the giant quadupole reso- Low-Lying Collective States in 90Zr and nance (GQR) and l.Q for the giant isoscalar mono- <1BSn by n* Inelastic Scattering pole. : To add to our knowledge of collective phenomena, • Experiment 797 — EPCS we measure^ the TC~ and n+ cross sections to the low- Univ. of Colorado, Sacramento Stele Univ., Los Alamos, lying collective states and giant resonances in '"'Zr, a Arizona State Univ. nucleus with a good valence neutron closure but a Spokesmen: J. L. L'llmann (Univ. cj Colorado) andN.S. P. weaker proton closure leading to a target that is King (Los A lamosj basically a single-closed shell. The first 2+ state therefore is expected to be a proton-like vibration, and this + In a previous comparison of inelastic 7i and K~ has been observed with other probes.1 For the giant scattering to giant resonances and low-lying collec- quadrupole, however, different theoretical models 40 8 tive states in Ca and " Sn (Refs. 1 and 2), an inter- predict somewhat different n~~/n+ ratios.1"'1 esting anomaly was observed for the K~/K+ ratio of the Data were taken during the summer at EPICS. giant-resonance cross section in "8Sn. For a single Because of improvements in muon rejec'ion, includ- closed-shell nucleus with an open neutron shell such ing an improved range telescope and time-of-flight as ""Sn, the first 2+ state is expected to be a slightly system, we could run at 164-MeV beam energy. The neutron-like vibration1 leading to a slight enhance- beam spot size could accommodate both a '"'Zr target ment of it" over 7t+ strengths. Our data for the 1.23- and the "8Sn target used previously, providing a good MeV state in "8Sn are consistent with this view. On comparison of the two as well as a limited study of the other hand, the giant resonances in a heavy the energy dependence of the n~/n+ ratio in "8Sn. nucleus are expected to show virtually no neutron Data on the low-lying states were taken at 10 angles, enhancement, which would predict the ratio of TC/n+ with the elastic peak at a spectrometer setting of 5 = strength to be nearly unity. Although we observed 6%. A sample spectrum for goZr at 30° is shown in Fig. this ratio for the bound low-energy octupole reso- 1. Giant-resonance data were taken with the elastic nance (LEOR) in ll8Sn, we observed a ratio of peak at 5 = 10%. Sample spectra, before acceptance

3" ZrU.TT') 165 MeV 150 •

00 20 40 60 80 100 Ex(MeV)

+ FIGURE 1. Spectra of n and n scattering at a laboratory angle of 30°, highlighting the low-iying states. RESEARCH—Nuclear and Particle Physics 23

Ex(MeV)

FlGlRK 2. Spectra of IT* and IT" scattering at a laboratory angle of 30°, highlighting the giant- resonance region.

correction, are shown in Fig. 2. In the region consist- 3. V. R. Brown and V. A. Madsen. Physical Review C ing of the giant quadrupole state at 14.4 McV and the 11, 1298 (1975); and A. M. Bernstein, V. R. Brown, isoscalar monopolc at 16.2 MeV there is an obvious and V. A. Madsen, Physics Letters 103B, 255 (1981) bump in the spectra. The low-energy octupole at and 106B, 259(1981). about 7.2 MeV also is visible. 4. N. Auerbach. A. Klein, and E. R. Siciliano Physical Data are being replayed and analyzed at Colorado Review C31, 682 (\9&5). using the Q system. Replay is largely completed and 5. W. W. True and N. S. P. King "Pion Excitation of analysis of the cress sections is under way. Collective States" (submitted for publication in Physical Review C). 6. R. J. Peterson and J. L. Ullmann "The Influence of References Unbound States for Inelastic Excitations of Giant Quadrupole Resonances" (to be published in /Vw- 1. J. L. Ullmann ct ai.. Physical Review Letters 51, 1038 clear Physics A ). (1983). 2. J. L. Ullmann el ul.. Physical Renew C 31. 177 (1985). 24 PROGRESS AT LAMPF—1984

Study of (n ,p) and (n,p) Reactions Given that the yield of separated isotopes is low, with EPICS we have taken advantage of the relalivelv large projection of yield from the vertical target position. We 4> Experiment 809 — EPICS have used strip targets of :4Mg and "Al, 5KNi and 4UCa, Univ. ofSou'h Carolina, Univ. de Neuchatel, Drexel Univ., and a full-sized CD: target. Histograms of the calcu- Univ. of Maryland, Arizona State Univ., The Gustaf lated vertical target position (XTGT) are given in Werner Inst., Michigan State Univ., Los Alamos Fig. 1. The strip targets are well resolved. Spoki'.snwii: H. S. Bkuipwd(I niv. ol South Carolina) and Results for (7t\/j) and (7t ,/>) for ^Mg are seen in .!. I'. lii;i;cr(L'itiv. tic Scuclialcl) Fig. 2. The spectra have been smoothed using a Participants: (i. S. Blanpicd. C S. MIKIIIU. (i. S. Adams. prescription that takes nearest channels into account H M Prccdom.C. S. Ulusnant.J. P. K^cr. B 11. and preserves the total area. The data have not been Wildcntha!. 11. Hrcm r. X. S. Chant. B. (i. Ritchie, li. corrected for the relative spectrometer acceptance. Hoislatl, . 1. Brown, amiC. I.. \lt>rris The relative scales are 5.5/1 between (n\p) and (n ,p). There are peaks in the range of excitation < 10 This proposal was prompted by recent results at MeV in the (7t ,/>) spectrum, with cross sections as the Indiana I'niversin Cuiotron Facility (IUC'F). high as 4.5 ub/sr for (n ,p) and 10-20 ub/sr for (7i+,p). which demonstrated that the (/>.7i ) reaction is selective in the population of discrete excited states in the The ratio of (7i',/>)/(7i ,p). averaged over an excita- residual nucleus.1 This reaction is characterized by a tion energy range from 15 to 38 MeV, is given in high momentum transfer to the nucleus and the necessity for at least a two-nucleon mechanism. The 1 ' dominant transitions lead to high-spin, stretched (or nearly stretched), two-particle one-hole stales that are "Mg and ^Al favored by the two-nucleon pion-production mecha- 30Q nism. The purpose of this study is to determine the selectivity of the (n ./>) reaction and. if it is as \p 1 |'l emphatic as the {p.n ) reaction, to investigate both 200 the reaction mechanism properties and nuclear- structure effects by determining the systematic^ over a range of energies and nuclei. 100 \ After the presentation of this proposal in January - A 1984, this experiment was given a high priority to prove the feasibility of observing bound states in the v • (n~,p) reaction. In a run that began July 4. we ac- CD2 ll quired 76 h of actual data. The high 0.9-mA current ; of 800-MeV protons, plus the reworking of the front 60 llll'ij' ll'll slits at EPICS, gave us a beam of more than 107 TT/S and >2 X 10" TT'/S. The n'd • pp normalization runs 40 % - yielded >If) 000 events in 30 min. As nothing was ill! 1 known about the energy dependence, angular dis- 1 Ill ! i tributions. .1 dependence, and nuclear-structure effects for the (7i ./;) reaction in the region of bound 20 if states, we chose to measure a variety of targets at one \ • energy and one fairly forward angle. We ran (K'./>) on l: :4 r 4 V C. Mg. AI. "Ca. and "Ni. and (TC'./>) on all but '-C at a scattering angle of 25" with 7 „ = 120 MeV. The Q XTGT (cm) value of'"C is such that I\ = i 45 McV results in the same field setting for the outgoing proton, so this FIGIRT. 1. Histograms of the calculated vertical setting was used for this target. target position (XTGT). RESEARCH—Nuclear and Particle Physics 25

Table I for 24Mg, ?7A1,40Ca, and 58Ni. These ratios have not been corrected for relative spectrometer accep- 24 24 tance. Except for Mg the ratio is 22 ± 1; the ratio for 30 Mg(7T,p) 120 MeV :4Mg is 6.4, which is about 3.4 times smaller. This 9 = 25° anomaly is clarified by taking ratios among the isotopes. The ratios of cross sections for (n+,p) and 20 for (n~,p) on the other isotopes relative to those for 4llCa are also given in Table I. The values for (n+,p) and (K~,p) on :7A1 are both enhanced by about 35% I over 40Ca. and those for 58Ni by about 18%; the (7t+,/>) :4 40 U.I for Mg is comparable to Ca, and the (n~,p) is a :4 LL factor of 4 larger. Thus the anomaly is in the Mg o (n~,p) cross section. LU in 2 According to Refs. 2 and 3, the 7i + IN absorption D 45 . *Mg(7r\p) 120 MeV seems to be dominated by tip, T= 0 pairs. Therefore, R = (ir+,p)/(7i",p) should be large. Our results' >n 27A1, 40Ca, and 58Ni basically agree with this statement. The 30 :4Mg is more puzzling. However, a calculation by Girija and Koltun4 show a strong model dependence of (n~,p). TWO remarks should be made at this point: 15 1. 24Mg and :7A1 data were taken simultaneously, excluding any normalization error; and 2. our results are not necessarily in contradiction 0 10 20 30 with the R ^ 4 results given by McKeown et 56 EXCITATION ENERGY (MeV) al. because their experimental ratio was averaged over a large range of outgoing proton energies and thus included secondary protons.

FIGURE 2. The "Mg^.p) data at Tn = 120 MeV, References 1. S. E. Vigdor ct al.. Physical Review Letters 49, 1314 (1982). TABLE I. Ratios of (n,p) Cross Sections Averaged 2. D. Ashery et al.. Physical Review Letters 47, 895 over Missing Mass of 15 to 38 MeV. The (1981). ratios have not been corrected for spectrometer acceptance. 3. G. Buckenstoss et al.. Physics Letters 137B, 329 (1984). ix- f 4(IC3 1Z-/K- 4(1Ca ^/ 4. V. Girija and D. S. Koltun, Physical Review Letters 24Mg 6.4 (0.2) 1.09 (0.03) 4.14 (0.15) 52,1397(1984). 27A1 22.9 (0.5) 1.32 (0.02) 1.37 (0.05) 5. R. D. McKeown el al.. Physical Review Letters 44, 4n Ca 20.9 (0.5) -— 1033(1980). 5ltNi 21.9 (0.6) 1.19 (0.02) 1.16 (0.04) —— -— 1.04 (0.03) 6. R. D. McKeown et al.. Physical Review C 24, 211 '-c (1981). 26 PROGRESS AT LAMPF—1384

10 Mass Dependence of Nonanalog Pion Double-Charge-Exchange Excitation Functions (DIAS, 9.6 MeV) * 10 \ • Experiment 826 —EPICS Unh. of Pennsylvania, New Mexico State Univ., Los Alamos, Univ. of Texas Spokesmen: C. Fred Moore (i'niv. of Texas at Austin), C. L. Morris (Los Alamos), and R. (iihnan (L'niv. of Pennsylvania)

Experiment 826 was approved in January 1984 to I o.i measure 5° excitation functions for nonanalog pion double charge exchange (DCX) on targets of 5(lFe and M'Se. These measurements were prompted by the observation of (possibly) systematic variations in the shape of nonanalog excitation functions for lighter 0.01 - mass tar.ets. from mass 12 to mass 40. The energy dependence of nonanalog DCX was first observed on l(lO and :4Mg during Exps. 310 and 448. The characteristic feature is a peak in the forward-angle cross section at about 160 MeV, with a 0.001 width of about 80 MeV. Experiment 577 measured 60 140 220 300 an angular distribution for lflO at 164 MeV and for- (MeV) ward-angle cross sections for DCX on :sSi and 4"Ca.

The "'0 angular distribution was consistent with sim- ffl ple diffractive scattering, and the 4"Ca. :"Si. and other Fici'RE 1. Excitation functions for DCX on Fe to the residual ground state (g.s.) and T — 2 double- cross sections indicated a mass dependence for analog state. nonanalog DCX of about A~4'\ Essentially all subsequent experiments have extended these systematics to additional reactions. In particular. Exp. 701 measured excitation functions The peak in the residual (g.s.) cross section at about for nonanalog DCX on all remaining solid T = 0 140 MeV is obvious. The unusual feature is that the targets. Two features were apparent. First, the peak width of the peak is smaller than that observed on energy of the excitation functions gradually de- lighter nuclei. Figures 2 and 3 display the best fit creased with mass, although there was a kink between parameters for the peak energy and width of all :jMg and :sSi. Second, all of the excitation functions measured nonanalog DCX excitation functions vs exhibit a similar width. Experiment 826 intended to the target mass. It is clear that the peak energy does investigate whether these trends continued up to decrease with mass, as does the peak width. The higher mass nuclei. interpretation of these trends is difficult because of Figure 1 shows the measured on-line excitation the lack of a quantitative theory for nonanalog DCX. function for ShFe. as well as data to the T = 2, 5(1N: The trends, however, do present a significant con- state that is the analog of the *Tc ground state (g.s.). straint upon potential theories. RESEARCH—Nuclear and Particle Physics 27

210 | r

0 10 20 30 40 50 70 80 90

FK;I KF 2. Mass dependence of peak energy of nonanalog DCX excitation functions. Data on masses 56 and 80 were obtained in Exp. 826.

150

100

-i . I . I i L_ 0 10 20 30 40 50 60 70 80 90 A Fic;i m: 3. Mass dependence of peak widths of nonanalog DCX excitation functions. Data on masses 56 and 80 were obtained in Exp. 826. 28 PROGRESS AT LAMPF—1984

Measurement of ALL in the ing the target in the vertical plane at ±40° in the Coulomb-Nuclear Interference Region laboratory, as shown in Fig. 1. at 650 and 800 MeV Information from the wire chambers in both arms • Experiment 583U — HRS enabled us to separate the elastically scattered pp events from those corresponding to scattering from Univ. of Minnesota, UCLA, Los Alamos, KEK Lab., the heavy nuclei (carbon, oxygen, and helium; in the Hiroshima Univ., Kyoto Univ. target and from the cryostat windows. A two- Spokesmen: M. Gaz:aly(l'ni\\ of Minnesota), G. Pauletta dimensional dot plot of the opening angle and (L'CLA), and A". Tanaka (Los Alamos) coplanarity, using the wire-chamber information, shows a clean separation of these events, as seen in Experiment 583U represents the second phase of Fig. 2. our research program for determining the real parts Only two independent measurements by the spec- of the pp double-spin-flip amplitudes. The measure- trometer are needed to determine A,, , as ments of the spin asymmetry ALL were completed in July 1984. The layout of the experiment is shown in Fig. 1. The experimental setup is similar to that used >'(TT)= y..n +P,,P,AII.) for Exp. 709, except that the C magnet was replaced by a superconducting solenoid on loan from Argonne and National Laboratory. Because of space limitations, the monitoring system used in Exp. 709 had to be modified. The new system consisted of two scintillation-counter tele- thus scopes in coincidence. Each telescope consisted of three scintillation counters and a wire chamber of the delay-line read-out type. Both telescopes were view-

/LIQUID HfLIUM RESERVOIR

^ / - '-' V--TARGCT fl«

f n . I-

FIGL'RF 1. Experimental setup for Exp. 583, elevation view. RESEARCH—Nuclear and Particle Physics 29

(a) (b) (c)

FKU'RK 2. Two-dimensional computer piots of event information from the monitor system of Exp. 583: (a) opening angle—vertical in-plane scattering angle in U (up) arm vs that in the ) (down) arm, (h) coplanarity—out-of-vertical plane scattering angle in the V arm vs that in the D arm, and (c) opening angle vs coplanarity.

The first airovv represents the beam-polarization direction and the second rei^res nts the target- polari/ation direction. Tlie target p. laii; • <:; MI was reversed at most angular settings to stiu'v -.he C'fcct of an\ spurious asymmetries present. Prelimin ;ry data for An at 650 and 800 MeV for the .-^iar range from fit „. ~ \.'i IO }b" are shown in Fig. 3 with pp.-- ,uus data' and predictions of the \anous phase- shift analyses by Hoshi/aki. Lechanoine-Leluc at Saclav. and Arndt.*

*liitbrm;ilinn on phasc-shil'l pivdictiuns is I'rum N. Hoshi/aki, K\oUi l'ni\crsil> (14S4): I . l.cehan(iirn.--I.eluc. Saday. F:r;intv/(icnc\u S«u/ci-luml I I'»S4). ami R. -\. \rndl rl al . .V.V (Onipulcr Code Solution SM ll).S4.

Reference I. I. P. Auer et al.. I'IIYMCUI Renew Letters 51, 141 1

50.0

FK.I Kh 3. Preliminary Au (((,,„) measured at 650 and 800 MeV. The sjlid circles are K\p. 583 data, the squares are from Rof. 1. 30 PROGRESS AT LAMPF—1984

Measurement of Third-Order Spin general mathematical function for its line shape.' Observables for Elastic p p ^ p of Following their suggestion we have created a com- Scattering at 800 MeV puter code that determines the target polarization by fitting the DMR signal. The results obtained so far • Experiment 685 — HRS from this method, however, are inconsistent with the UCLA, Los Alamos, KEK Lab., Hiroshima Univ., Kyoto asymmetry measurements from the 1983 experi- Univ. and Univ. of Education in Japan, Univ. of ment. We now believe that the problem is due to the Minnesota, Univ. of Texas at Austin neglect of the dispersion part of the target sample Spokesmen: G. J. Igo and M. Bleszynski (UCLAJ magnetic susceptibility in our calculation of the DMR-signal line shape. This effect in fact is quite During the summer of 1984 we continued our large, as has been demonstrated recently by a group at measurements of the third-order spin parameters. Dubna.4 We are now including these effects in our We again used the KEK frozen-spin polarized deu- fitting code. teron target. Last year we used the conventional ZOLTAN magnet with the target polarized normal to the scaitenrsg plane (in the .V direction). This year the References superconducting Helmholtz coil lent to us from 1. M. Bleszynski et al.. Physical Letters I06B, 42 (1981). Argciine National Laboratory, provided us with a 2. J. Arvieux et al.. Nuclear Physics A431, 613 (1984). target polarized along the direction of the incoming beam (the L direction). We measured at the same 3. O. Hamada et al.. Nuclear Instruments and Methods angular settings as last year, at 7, i 1, 14, and 16.5° in 189,561 (1981). the laboratory frame. The analysis of the 1983 meas- 4. Y. F. Kiselev et al. Nuclear Instruments and Meth- urement is almost completed, and it is well on the ods 220, 399 (1984). way for the 1984 data. Two methods were available for measuring the target polarization. The first was to use the asymmetries in the differential scattering cross section that

depend on the target polarization. The second was to Measurement of ANN and Ass for pp Elastic use the deuteron magnetic resonance (DMR) signal. Scattering in the Coulomb-Nuclear As the analyzing power for vector-polarized deu- Interference Region at 650 and 800 MeV terons has been measured elsewhere1: for the A'-type • Experiment 709 —HRS target experiment, we could rely completely on the first method. Before and after each data run (approx- Univ. of Texas at Austin, Univ. of Minnesota, Los Alamos, imately every 20 h), we made an asymmetry meas- KEK Lab., Hiroshima Univ., Kyoto Univ. urement with the spectrometer set at ±12.5°. In 1984 Spokesmen: (i. Paulellafiniv. of Texas), M. (iazzaly with the Z.-type target, no such left-right asymmetry (I 'niv. of Minnesota), and :V. Tunaka (Los Alamos) was available and we decided to use the asymmetry in the cross section for recoil deuterons at 0° in the The main objective of this experiment and Exp. laboratory frame. To this end we always had a rela- 583U is to provide accurate measurements of the tively large L admixture in the beam polarization. spin asymmetries .1,,, .-I \ v, .Iss, and .ls, in the clastic The corresponding observable Cu . however, has not pp channel at small scattering angles in the Coulomb- been measured previously and provides us with only nuclear interference region. a relative value for the target polarization. An These measurements will provide absolute calibration will be obtained by the DMR 1. the real parts of the pp double-spin-flip method, which determines the population distribu- amplitudes at momentum transfer / = 0, and tion over the three magnetic substates of the deuteron 2. tests of theoretical forward-dispersion relation (w= 1.0.-1). calculators as well as different phase-shift A group from KEK has analyzed the rather com- analyses. plicated structure of the DMR signal and derived the In September 1983 the first series of experiments was completed. Ass was measured at 650 and 800 RESEARCH—Nuclear and Particle Physics 31

MeV over the angular range from 3 to 16° in the 3. the ability to determine the beam position and laboratory using the HRS and an /V-type frozen-spin profile at the target, which required installation polarized target. A C magnet (ZOLTA?"J) provided of two beam-profile monitors upstream and the polarizing field of 25 kG as well as the holding downstream of the target; and field of 3 kG. The magnitude of the holding field was 4. the ability to monitor beam intensity. This was dictated by the need to minimize the effect of the done by using two ion-chambers filled with magnetic field on the incident and scattered particles special gas mixtures lo ensure enough counts at and by its ability to maintain the target polarization the low incident beam intensity (—106 for a reasonable period of time. protons/s) used during the experiment. The main features of the experimental setup were Figure I shows the layout of the experiment. The dictated by the fact that the measurements extend to mean target polarization was measured by an NMR very small angles. The requirements were system. Because the polarization in the target area 1. the ability to distinguish between the particles illuminated by the beam varied more rapidly than the scattered from the hydrogen and those scattered whole target polarization, a monitoring system from the stainless steel and copper cryostat capable of measuring the target polarization had to be windows. To satisfy this requirement we used a devised. The monitoring system was made up of two polarized target with high cooling power and a scintillation-counter telescopes at ±18.5° and two cryostat with very thin windows. The dilution conjugate recoil telescopes at ±61.5°. The monitor refrigerator at the National Laboratory for High was used to measure both the beam and target Energy Physics (KEK) in Japan was the only polarizations. Each telescope contained a wire suitable and available target. KEK lent it to chamber of the delay-line read-out type. The angular us for the experiment: distribution from each wire chamber provided an 2. ihe ability to replace the polarized target with effective method for distinguishing between the solid targets for HRS calibrations or with a events that were due to pp elastic scattering from phosphor for beam tuning. For this flexibility hydrogen and those due to the quasi-free pp scatter- we fabricated movable platforms for the ing from the heavy target materials as well as the polarized target and its associated equipment cryostat windows. (such as a liquid-helium dewar). The platform During the experiment the beam polarization was movements were powered by several stepping reversed every minute whereas the target polariza- motors iwmc of the movements were tion was reversed every few hours. This procedure synchronized). The complete setup was in- enabled us to obtain four independent measurements stalled at the HRS with the polarized target at at each scattering angle: ¥{]]). >'(||). }'(||). and the pivot of the spectrometer: Y(H). where the first arrow represents the beam

SPECTROMETER FRAME

BEAM-"-

ZOLTAN ELECTROMAGNET

-DILUTION REFRIGERATOR

FIGURE 1. Experimental setup for Exp. 709. 32 PROGRESS AT LAMPF— 1984

polarization direction and the second represents the where >'o is the spin average yield, Pf, is the beam target polarization. From the above four quantities polarization, and P, is the target polarization. Because one can obtain both the beam and target polarizations were determined independently as described above, values of ,-l.v.v and As could be extracted at each angle. = HTT) Preliminary data for Ass at 650 and 800 MeV as wel! as various phase-shift analysis predictions are shown in Fig. 2. The data agree with previous measurements' and with the phase-shift predictions of Arndt, Hoshizaki, and C. Lechanoinc-Leluc at = 4}-„ larger angles.* The data below 10° cm. suffer from and 'Information on phase-shif: predictions is from R. A. Arndt ctal.. .V.V Computer Code Solution SMI984: N. Hoshizaki. &,= Y(\J)+ Kyoto Universin, 1984; and C. Lcchanoinc-Leluc. Saclay- Gencva. 1984.

p+p-p+p -

TP = 650 MeV

10.0 20.0 30.0 40.0 50.0 (deg)

FIGLRE 2. Preliminary A,s (ecm) data at 65P and 800 IVIeV. The solid circles are from Exp. 709 data; the squares are from Ref. 1. The solid curve represents phase-shift-analysis predictions from Hoshizaki; the dashed line, from Lechanoince-Leluc; and the dot-dashed line, from Arndt et al. RESEARCH -Nuclear and Particle Physics 33

about K)"'n contamination from .lsv but this will be manifestly different from the quark structure of an corrected when our ,-Iss measurements have been isolated nucleon. Iron and deuterium both may be to completed. blame for the EMC anomaly, but because deuterium is a dilute system with the neutron and proton loosely bound, it is natural to regard deuterium as providing Reference virtually free nuclcons and to attribute the EMC 1. M. McNaughton et al.. Physical Review C 23, 828 anomaly to iron. Although a plethora of hypotheses involving new quark-level physics has been presented to explain this effect, the only calculable model thus far suggests that it is no more than a result of classical nuclear physics.1 According to this model the effective num- 500-MeV Nucleon Scattering and the ber of pions per nucleon is larger for a heavy nucleus European Muon Collaboration Effect than for a free nucleon. The EMC effect can be attributed to occasional (u.u') on one of the partons ^ Experiment 741 — HRS of the extra pions in iron, a process that leads nat- Los Alamos, Indiana L'niv. Cyclotron Facility urally to enhanced scattering at (.v ~- »;„/;».,). Spokesmen:'/'. A. Curcy (Indiana I'nn: Cyclotron Facility: The mechanism for producing these excess pions and.I. H. McClelland (Los Alamos) in a heavy nucleus derives from a collective, many- body enhancement of the field of pions exchanged by The European Muon Collaboration (EMC) has the bound nucleons. As might be expected, this also measured the electromagnetic structure function has distinct implications for nuclear structure in h\(.x,Q2) for deep inelastic muon scattering from deu- regimes far from those probed in deep inelastic iep- terium and iron targets. These are very high energy ton scattering. Specifically, this same model predicts 1 (E^m = 120- to 280-GeV). fine-grained [Q = 9- to that, for quasi-elastic scattering with momentum 170-(GcV/c):] experiment: designed to probe the transfers of only 300-400 MeV/c. the response of a distribution of qu^ks inside nuck'ons in much the heavy nucleus to a o • q longitudinal-spin field same way that quasi-elastic elcriron scattering at a sii juld be significantly enhanced o> cr its response to few hundred million electron volts samples the dis i aXq transverse-spin field.2 This enhancement tribution of nucleons inside a nucleus. It was felt that ihould exhibit a characteristic energy-loss de- with such short wavelengths the structure function of pendence and should peak around

20 40 60 80 100 120

FICIRE 1. Ratio of the lead longitudinal- to transverse-spin response functions. The solid curve is the prediction for this ratio of Ref. 2 with parameter values necessary to reproduce the EMC effect. Corrections for surface absorption and isoscalar background also have been included. The data points represent our measurements from 500 MeV (p,pr); the open circle is a preliminary result from our latest run.

project the ratio of the lead longitudinal- to data at q = i.75fm ' requires g' > 0.85 whereas transverse-spin quasi-elastic responses are shown in g" < 0.7 is needed to understand the systematics of Fig. 1. The solid curve illustrates the results of a Gamow-Teller excitations. prediction for this ratio using the model of Ref. 2 Only further investigation will tell if we are gloss- with parameter values needed to reproduce the EMC ing over key nuclear dynamics or if unforeseen non- effect. In performing this calculation, we have in- nucleonic aspects of nuclei are being revealed. Re- cluded details on surface absorption and isoscalar cently obtained data for 40Ca (p.p) quasi-clastic scat- background relevant to 500-MeV (p,p') that were tering will be helpful in this regard, but similar data at not incorporated in the original model. There is clear momentum transfers other than q= 1.75 fm~' will be disagreement in the direction of no enhancement in crucial for a complete picture. the nuclear pionic field. The difficulty that this causes for the pionic inter- References pretation of the EMC effect is most exciting now that EMC data may demand that we descend to the quark 1. M. Ericson and A. W. Thomas, Physics Letters 128B, level to fully understand the nuclear spin-isospin 112(1983). response. In a more pedantic sense, our results raise 2. W. M. Alberico, M. Ericson. and A. Molinari, Nu- general questions regarding current models of the clear Physics A379, 429 (1982). residual interaction in this channel. At the very least, 1 3. T. A. Carey et al.. Physical Review Letters 53, 144 they imply that the Landau-Mi°dal parameter g has (1984). a significant momentum dependence because our RESEARCH—Nuclear end Particle Physics

Measurement of ANN and ALL for the The spin asymmetry A%s was measured during + PP dn Reaction at 650 and 800 MeV August 1983 at 650 and 800 MeV tor the laboratory • Experiment 790 — HRS angles 2.0, 3.5, 5.5, and 7.5°. The experiment was performed using the HRS and an /V-type frozen-spin Los Alamos, Unir. of Minnesota, UCLA, KEK Lab., polarized target. The polarizing and the holding mag- Hiroshima Univ., Kyoto Univ., Kyoto Univ. of Education netic field were provided by a C magnet, ZO1TAN. Spokesmen: N. Tanaka (Los Alamos), M. Gazzaly (Univ of The experimental setup, as well as the monitoring Minnesota) and U. Pauleita (UCL4) system used, was the same as that discussed for Exp. 709. The main objective of Exp. 790 is to study the The momentum resolution, combined with time- inelastic channels in the pp system with emphasis on of-flight and pulse-height information from the HRS the following: focal-plane detectors, permitted a clean separation of 1. measurement of the angular distribution for the signal from the background. spin asymmetries in the reaction p —- d + K+ at Preliminary .l data at 650 and 800 MeV are small angles, vv shown in Fig. 1, together with previous data1'3 at large 2. determination of the total inelastic cross sec- angles and the predictions of partial-wave analyses.* tions in pure longitudinal- and transverse-spin states, "Information in Figs. I and 2 on large angles and predictions of 3. determination of the total cross section for the + partial-wave analyses is from N. Hiroshige. Osaka University, reaction pp —* npn in pure longitudinal- and 1984, and D. Barlow, Northwestern University, 1984. transverse-spin states, and 4. determination of the tensor polarization 7\0 for the deuteron.

FIGURE 1. Preliminary ASN(8cm.) measured at 650 and 800 MeV. The solid circles indicate Exp. 790 data; the squares, data from Ref. 1. Phase-shift- analysis predictions are from Hiroshige (solid + -0.1 I- HIROSHIGE p+p-d+7T curve); Rinat, Ref. 4 (dotted curve); and Niskanen, RDUT NISKAKEN TP = 650 MeV Ref. 3 (doit-dashed line). -02 EXP780UAI.. TIPPERS U*lA -0.3 -0.4 F-05 -O.fl -0.7

-0.9 -L0 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 BO.O 90.0

Bc.m. 36 PROGRESS AT LAMPF— 1984

0.9 1 1 1 r 1 1 I "1 0.8 p+p-d+7T+ 0.7 HKOSHIGE Tp = 800MeV _ 0.6 KXPTKXPTBoB n a 0.5 BARLOW nilA a 0.4 0.3 02 01 d o.o < -01 -02 -0.3 -0.4 -0.5 -0.6 -0.7 -0.B -0.9 05 P+p-d+774 0.4 E 2. Preliminary Au. (O^m.) measured at 650 EXP 790 MIA O T = 650 MeV sind 800 MeV. The solid circles indicate Exp. 790 0.3 aiRLDITDAIl B P 02 data; the squares, data from Barlow; and the solid 01 curve, phase-shift-analysis predictions from 0.0 Hiroshige.

-0.3 -0.4 -05 -0.6 -0.7 -0.B -0.9 -L0 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 BO.O 90.0 (deg)

+ Our data arc in agreement with the existing data and Aal(pp^~' dn ). The deutcron tensor polariza- within statistical errors, but are in disagreement with tion7'2() will be determined from the results of the Au theoretical predictions. It should be emphasized that measurement near 0°. the limit on the smallest angle and the statistical When the results of Exp. 790 are combined with accuracy were due to constraints on the running time. the results of Exps. 583U and 709, we will be able to The spin parameter Au was measured at 650 and decompose the total inelastic cross sections &aL(pp) 800 MeV during July 1984 using the same ex- and Ac, (pp*) into their inelastic components. perimental setup as for Exp. 583U. These measurements were done at forward angles that were not References previously accessible because of experimental difficulties associated with small-angie measurements. 1. W. B. Tippeir., Ph.D. thesis, Texas A&M University.

Preliminary Au data from 1984 runs at 65C and Los Alamos National Laboratory report LA-9909-T 800 MeV are shown in Fig. 2. together with the (October 1983). previous data at large angles and predictions of 2. J. A. Niskanen, Nuclear Physics A298, 417 (1978), partial-wave analyses. When our data are combined and Physics Letters 79B, 190 (1973). with the previous measurements, complete angular distributions will be obtained. These angular dis- 3. A. Rinat et al., Nuclear Physics A397, 381(1983). tributions will be integrated to obtain Aoi(pp*—> dn+) RESEARCH—Nuclear and Particlo Physics 37

Pion Single Charge Exchange on '"C 70 ' ' ' I • ' ' I "L.* = 35 MeV • Experiment 523 — LEP 60 Los Alamos, Univ. of Colorado, Arizona Stats Univ. 50 Spokesmen: H. H'. Baer (Los Alamos) and J. L. Ullman (L'niv. of Colorado) 40 30 The purpose of this experiment is to provide a complete set of forward-angle, single-charge-ex- 20 change (SCX) differential cross sections for the isobaric-analog state (IAS) of I4C. These data comple- 10 ment those taken at the same energies on elastic 0 scattering and double-charge-exchange (DCX) scat- MeV tering. We hope that such a complete data set will be a basis for quantitative analysis of both SCX and DCX reactions. In addition, the IAS data on UC are com- ^100 plementary to the low-energy SCX data on 7Li and I5N in that 14C presents a 0+ — 0+ IAS transition for which there can be no spin-flip amplitude nor quadrupole transition amplitude. 8 In the 1984 data runs, we measured the 50-MeV angular distribution between 10 and 80° and further determined the U" excitation function b\ autiing 42.5- and 50-MeV points to the data we have at 35, 65, 80, T, =65MeV 100, 165, 230, and 295 MeV. The new data provide a + better determination of the minimum on the 0° excitation function that occurs near 50 MeV. The sharp minimum in the 0° excitation function is evident in Fig. 1, which shows the measured spec- 100 tra in the most forward angle 9 bin (0 = 10°) for energies 35, 50, and 65 MeV. At 50 MeV the IAS nearly vanishes. At 35 and 65 MeV the IAS is a prominent feature of the spectrum. Preliminary values of the measured 0° differential cross sections (cm.) are shown in Fig. 2. The data are compared to 40 60 80 100 the free-nucleon cross sections (cm.) as calculated V(MeV) with a 1984 phase-shift analysis (FP84) of Arndt.* Une sees that the I4C data follow the shape of the n~p FIGURE i. The n" spectra measured in the angular 14 — K"H reaction quite closely. The minimum is range from 0 to 11° for C. We note the disap- sharper with energy in I4C than on the free nucleus, pearance of the IAS transition at 50 MeV. and the position of the minimum appears to occur at several million electron volts higher energy in I4C. This is a little surprising, as one might have expected are predicted by the calculations of Kaufman, Gibbs. a blurring of the sharp ?- and p-wave interference by and Siegel* (KGS), shown in Fig. 2. Calculations nucleon medium and Coulomb effects. The sharpen- performed with the code PIESDEX,** retaining only ing of the minimum and the shift to higher energies

•Information from W. k, Kaufmann, W. R. Gibbs, and P. The computer program for pion-nudeon phase-shift analysis Siegel, based on theory to be reported in Ref. 1. is from R. Arndt. Virginia Polytechnic Institute and State **The computer code PIESDEX is from E. R. Siciliano, Univer- University. 1984. sity of Georgia. 1984. 38 PROGRESS AT LAMPF—1984

l ' i 1000

14C(TT+, TT°)14N(IAS) Tn = 49.3 MeV 3 PRELIMINARY I0 FPB4 TTN; ---K GS • 100 10 - P1ESDEX:

10' zf Q o LJ b if) in 10 CO o

10°=- I '1 I I _L I I I 100 200 300 20 40 60 80 TT (MeV) (deg) ecm. FiGfRF. 2. Preliminary values of 0° differential FIGURE 3. The angular distribution for the IAS cross sections (cm.) vs laboratory pion kinetic transition at 50 MeV on I4C. The curves are fits to energy. the data using Legendre polynomial series. The solid line is for n = 2 and the dashed line is for n = 1 (see text). first-order terms (no p:), are shown in Fig. 2 for the higher energies. We note that these first-order calculations predict increasing cross sections between 164 extract the 0° differential cross section, we are fitting and 295 MeV, whereas the data show a flat or slightly these data with a Legendre polynomial series decreasing cross section for this energy interval. Of special interest in the 1984 measurements was the IAS angular distribution at 50 MeV. This interest da + I A P (cos 9) was stimulated by the article of Miller.- which argued dQ k L that if the forward-angle DCX cross sections for the reaction MC(jc'.7t )UO double-isobaric-analog state I4 (DIAS) were larger than the C (TC+,7I")UN (IAS) cross Two representative fits are shown in Fig. 3. sections, one would have evidence for six-quark They correspond to an n = 1 fit yielding cluster contributions to the DIAS transition. The (.•!,,,A,) = (224, -219)nb/srandann = 2fityielding 1 DCX experiment was completed in the summer of (.-!„,.-!,, .-I,) = (99. -5. -92) |.ib/sr. These two fits give 1984 and yielded cla/dQ (DIAS) (0°) = 3.9 + 0.5 different extrapolations to 0°. The use of higher order (j.b/sr. The angular distribution we measured for the terms (n > 2) does not improve the quality of the fits IAS transition is shown in Fig. 3. We see that it has and yields curves quite similar to the one shown for n 4 I5 the forward-angle dip as previously observed for N = 2. We are still studying how to extrapolate most and as exists in the free iCp —* n°n reaction. To reliably to 0°. At present, values of the 0° cross RESEARCH—Nuclear and Particle Physics 39 sections between 2 and 8 ub/sr are acceptable. Thus References we see that at 50 MeV the IAS and D1AS cross 1. W. R. Kaufmann, W. R. Gibbs. and P. Siegel, Physi- sections at 0° are comparable in magnitude. cal Review C IK, 1286(1984). The data set at 50 MeV on UC for the various pion channels related by isospin invariance is now rather 2. G. Miller, Physical Review Letters 53, 2008 (1984). complete with the availability of K' and n elastic- 3. M. J. Leitch, E. Piasetzky, H. W. Baer, J. D. scattering data and the angular distributions for the Bowman, R. L. Burman. B. J. Dropesky, et al., "The l4 + l4 IAS and DIAS transitions. These data are being Double Analog Transition C(ji jr) Oat 50 MeV/' analyzed within three different theoretical frame- Los Alamos National Laboratory document LA- works.* The central issue is to determine to what UR-84-2754(1984). extent multiple pion scatterings play a role in these 4. M. D. Cooper. H. W. Baer, R. Bolton, J. D. Bowman, scattering processes and to see if these multiple scat- F. Cverna, N. S. P. King, et al., "Angular Distribu- 15 + l5 terings occur on the long- or short-range correlations tion for N(7t ,7r°) O (g.s.) at 1\ = 48 MeV," Physi- in the ^patial wave functions. cal Review Letters 52, 1100 (1984). 5. T. Karapiperis and M. Kobayoshi. SIN preprint PR-84-14(1984). •References I and s and information from E. K. -Sicihano. University of Georgia. 19S4.

Angular Distributions for the 1sN(n\n°)15O presence of the other states. Also, the nuclear struc- Reaction to the Isobaric-Analog State at ture of I5N and 'X) are relatively simple. iOO and 290 MeV The maximum-likelihood method' was used to • Experiment 401 — LEP extract the area under the peaks. The angle-dependent line shapes used were obtained from a Monte Los Alamos, Arizona State Univ. Carlo simulation of the jr° spectrometer. The simula- Spokesmen. J. D. Bowman amiM. D Cooper fl.es Alamos) tion parameters, which include beam energy and Participants: M. J. Leiich, 11 II. Baer. J. D. Bowman. \l. phase space, target characteristics, and wire-chamber D. Cooper. A. L. Haitin. F. Irani..). C. Penx../. R. and lead-glass resolutions, were experimentally de- Comfort, and.!. .V. Knudsan termined. The energies of states and the three-body threshold were determined from kinematics. Only We have studied the ''N(n',jt") isobaric-analog- the amplitudes of the peaks and the level of the non- state (IAS) reaction over a wide range in energy where target-related background were free parameters. The the dynamics of the 7tA' interaction changes from p- resolution (FWHM) in these measurements was wave dominance in the resonance region to the -4 MeV at 100 MeV and -5 MeV at 290 MeV. nearly complete s-, /7-wave cancellation near 50 MeV. The measured cross sections, transformed to the The study of this reaction is a severe test of our ccnter-of-mass frame, are shown in Fig. I. The error understanding of the n-nuclcus reaction mechanism bars shown, typically 8-15%, represent only the over a broad range in energy. statistical errors in the measurements. Also shown in Measurements of the angular distribution at beam Fig. 1 are the measured angular distributions for 50 energies of 100 and 290 MeV were made using the n" and 165 MeV that have been reported previously.21 spectrometer. The angular distributions cover from 0 Extrapolations to obtain the 0° cross sections were to 90° at 100 MeV and from 0 to 20° at 290 MeV. The performed by fitting the measured angular distribu- choice of !1N as a target is dictated primarily by the 5- tions with a polynomial in 0:. The extracted 0° cross MeV separation between the IAS (ground state) of' 5O sections, shown in Fig. 2, have a deep minimum near and its first excited state. Because the separation is 50 MeV; they rise as the energy approaches 165 MeV roughly twice the instrumental resolution, small ex- and then fall toward 290 MeV. The trend is very citations of the IAS can still be observed in the similar to that of the elementary nN charge-exchange 4G PROGRESS AT LAMPF—1984

4 | 0 F 1 I 1 I 1 I 1 I0 I I I

FP84 PS (Arndt) ;

290 MeV icr 15, Gibbs S Koufmnn " IAS

10" 165 MeV

!5N(7r>l;ISO (IAS) 9-0° io 3 Preliminary

100 MeV 10 _L _L 0 40 60 120 160 200 240 280 Pion Kinetic Energy Lab (MeV) V** r FIGI'RE 2. Comparison of the complete set of the measured 0° cross sections with the theoretical calculations. The dashed curve represents the free 50 MeV n/V laboratory cross sections | Arndt phase-shift 10' (PS) solution FP84|. The solid curve indicates the li* DWIA calculations of Gibbs and Kaufmann.

IOV _J t I 1 1 t 20 80 120 160 tions the effect of binding and Pauli blocking are explicitly considered in the construction of the dis- 'lab torted waves. The calculations lead to a reasonable description of the data, especially near the minimum FiGl/RE 1. The "N(n%it°)'-O angular distributions at 50 MeV as well as above 200 McV. at 50, 100, 165, and 295 MeV.

References cross sections. Data points at 35. 42. 57. and 65 MeV were taken during Exp. 850. Figure 2 shows the 1. M. D. Cooper et al.. Physical Review C 25, 438 (1982). distorted-wave impulse approximation (DWIA) calculations of Gibbs and Kaufmann.* In these calcula- 2. M. D. Cooper et al., Phtsical Review Letters 52, 1100 (1984). *Information provided by W. Gibbs, Los Alamos, and W. 3. A. Doran et al. Physical Review C 26, 189(1982). Kaufmann, Arizona State University. 1984. RESEARCH—Nuclear and Particle Physics

Study of the 160 (rT,n°p) Reaction Fe(7r|7r+p) =245 MeV • Experiment 776 —LEP = 140° MIT, Los Alamos, Tel Aviv Univ., SIN, Weizmann Inst. S. Gilad(MlT), E. Piasenky (Los Alamos), andJ. Alsier (TelAviv L'niv.)

The study oi pion-induced nucleon-knockout reactions has made a significant contribution to understanding A interactions in nuclei. The charged-pion channels (n\rSp), (n ,n~p), and (jt",7t~«) were studied in detail on heavy nuclei through inclusive' experiments (|:C, 5hFe, :i|l)Bi, and l6l!iO at ! 65 and 245 MeV) and exclusive-"' experiments ['"O at 165 and 245 MeV with (Tt'.rt^p) only]. The single-charge-exchange reaction lhO{Kr.K'p) was measured last year by this collaboration. Preliminary results are reported here. In the early coincidence measurements' of the v FIGI'RF. 1. Pion-proton angular correlation in the ratio a^(n' .n*p)/oll,(K~.K~p). the direct knockout 12 + + strength was deduced from the np angular correlation C(n ,n p) reaction. The incident pion energy is 245 MeV, the pion angle is 140°, and 8,, is the only (see Figs. I and 2). In the recent coincidence 2 proton angle in the reaction plane with \|/p perpen- experiment, ' angles and energies of the outgoing dicular to it. particles were measured. The missing-mass resolution was about 3 MeV and was sufficient to identify the ground state of the daughter nucleus, which is

-20 BO 100

0p(deg)

E 2. Slices of the up angular correlation along the reaction plane with a width of Ayp = 0 + 6° for nC(n+,K*p) (squares, »t+; crosses, Jt"). Each solid curve is the result of a two-Gaussian fit to the data. The arrow marks the angle for the free np scattering, the dashed curves are the broad Gaussians, the incident pion energy is 245 MeV, and the scale for 7t+ scattering (right) is the same as that for n+ scattering (left) but multiplied by the ratio of free n p/n+p scattering cross sections. 42 PROGRESS ATLAMPF—1984

16 0{irs.TTsp)15N 1 r

1/1 c

70 60 90 IOO HO 120 130 140 (deg) 50 Ficii:BK 4. Ratio of the quasi-free n* /n cross sections. The curve is the free n+p/n~p cross-section ratio.

0 50

Ex (MeV) dominanily populated by direct /;,/rsheII proton knockout (see Fig. 3). Both of these measurements FIGURE 3. Excitation-energy spectra of the re- I5 16 15 report consistently strong deviations of the ratio sidual N nucleus for O(it*,n:» N and + + a i (K .n p)/a , (K~,K~P) from the free ratio 16O(jr~,jT/;)15N reactions. The incident energy is q q a (7i+p —- K+p)/a (iCp —* n~p), as can be seen in Figs. 4 240 MeV, the pion angle is 60°, and the proton angle is —35°. and 5. The quasi-free ratio is about 3 times larger

16 i 4 4 1515 0(n ,n p)p) Ng.s. c 9P =Bo+17.5 Bp = Bo eP=e0-i7.5° BTT' 60 l—1—1—1—r 40 eo= - 35! £20 U . L

0 = -52.5° FIGURE 5. Ratio of n*/n -induced cross sections to 60' I5 ! the NBS. in each proton telescope compared to the i estimate (solid curves), including AW knockout Jtr (see text and Rtf. 2 for details).

10 130'

0 50 100 150 50 100 150 50 100 150 200 V(MeV) RESEARCH—Nuclear and Part/c/e Physics 43

'7T

FiGi'RE 6. Illustration of (a) the direct quasi-free and (b) the AA'-interaction contributions to the (n ,n p) reaction.

than the free ratio at the most forward 7t angle ference between direct and AN knockout amplitudes measured. This large ratio implies that the quasi-free is the dynamical reason, one expects that the knockout process itself is substantially modified, as a(K*,n p)/a(x+.Tinp) ratio will be modified the other this ratio cannot be explained by simple impulse way (constructive interference) and that the overall approximation. The strong (n'.n^p) is unlikely to be effect will be smaller.* enhanced by so large a factor: therefore, the primary The collaborators on this experiment, consisting of effect must be related to suppression of the (71 .71 p) persons who made the two measurements of the + cross section. all,{n*.K p)/otli{K~.K~p) ratio and persons from MIT 4 5 + I6 Hirata. Lcnz. and Thies suggested that a A.V inter- and LAMPF. measured ov, (TC ,JT°/7) on O to con- ¥ + ) action can cause this effect. The mechanism they struct the oqt(n*.n p)l<5lll(-K ,K p) ratio. The experi- suggested is that the A interacts with another nucleon ment consisted of measurements in coincidence with in the nucleus. As a result of this interaction the other 7t" (using the TT" spectrometer) and the proton (using a nuclcon is knocked out. whereas the r.ucleon emerg- special proton arm built for this experiment). The ing from the A decay is recaptured in the nucleus (see experimenters finished taking data by the last cycle of Xb + Fig. 6). As for two-body absorption, this ratio of 1984. The reaction O(n ,n°p) was measured at TK = quasi-free knockout reactions is a filter for A/V in the 165 and 245 MeV for the 7tH angles between 30 and T= I interaction. The T— 2, ;VA intermediate state 130°. At each angle the protons were detected by must lead to the T = 3/2. jtA1 state and therefore using an array of plastic scintillator telescopes, which will not cause a change in the ratio compared with covered the quasi-free angular-correlation r.-gion. Al- the free one. Simple calculations.-' assuming that the though the data are still being analyzed, preliminary modification to the ratio is due to interference be- results from the first run indicate that the quasi-free tween the direct jt /; amplitude and the A.Y knockout process (a knockout of a p-shell nucleon) can be amplitude (A.V is in the T = 1. .S" = 2. L^ = 0 identified (see Fig. 7). When analysis is complete, we channel), are presented with the data in Fig. 4. These hope that it will either confirm the model suggested calculations are in good agreement with the data. or shed new light on the process.

This model for explaining the oq,(^ .n'p)j- c,,,(7c .n'p) ratio has a clear prediction for + "Information provided by F. Lenz. SIN. 1984. the ratio of a,,, (n .K'p)/atj, (K~.n"p). If this inter- 44 PROGRESS AT LAMPF—1984

r0 p ) 240

= 245MeV TIT* 200 s 9-irO= 100 160

120

11 . 40

i inklillili ..ill ' 0 -30 0 30 60 90 EXCITATION ENERGY (MeV)

FIGI RV 7. Excitation-energy spectra of the reaction 16O(jr+,jr°/>). The incident energy is 245 MeV and the it" and p are at conjugate angles.

References 1. h. Piaseizky et al.. Physical Review Letters 46, 1271 3. C.H.Q. Ingram, in the "Proceedings of the Sym- (1981); E. Piasetzky et al.. Physical Review C 25, 2687 posium on the Dynamics of A in the Nucleus," (1982); and E. Piasetzky. Ph.D. thesis. Tel Aviv Argonne National Laboratory report ANL- University (unpublished). PHY-83-1 (1983). p. 55. 1. G. S. Kyle et al.. Physical Review Letters 52, 974 4. M. Hirata, F. Lenz, and M. Thies, Physical Review C (1984); and G. S. Kyle el al.. :n the "Proceedings of 28,785(1983). the Symposium on the Dynamics of A in the h + Nucleus," Argonne National Laboratory report 5. "Study of the O(n .np) Reaction," LAMPF HY-n-l (1QV-;. p. S"j. Proposal 776. RESEARCH—Nuclear and Particle Physics 45

n -Nuclear Elastic Scattering from scattering alternately from a CH, target and a l2C Nickel and Tin Isotopes at target and then subtracting the observed spectrum |: Energies Between 30 and 80 MeV from the C target from that of the CH: target. The area of the elastic peak of the subtracted spectrum • Experiment 814 — LEP was then used in conjunction with the incident beam Virginia Polytechnic Inst. and State Univ., Los Alamos, flux, target density, etc., to calculate a cross section Univ. of South Carolina, Univ. of Maryland that, when compared to the known hydrogen cross Spokesmun: \l Hlcchcr (I 'irgmiu Polvtcchnii- Inst. and section, yielded a calibration constant. The resulting State I'nn:) quantity (./'AQe)~', which should be constant across the angular range of the spectrometer, was found to Experiment 814 was the first experiment to use the be constant within 6% (A£2 is the spectrometer solid new Clamshell Spectrometer. Its objective was angle, e is a constant of instrumental efficiency, and./" twofold: is the proportionality constant that relates the num- 1. to investigate the isospin effects in non-«elf- ber of counts in the JI-U decay monitors to the flux in conjugate nuclei at subresonance energies and the incident beam). 2. to act as a reasonably uncomplicated first test of Two major parts of the Clamshell were not opera- the newly completed spectrometer. tional for this first experiment: (1) the evacuated With the Clamshell's expected good resolution and target chamber and (2) the focal-plane muon rejector. large solid angle, it will be possible to economically Neither was considered essential for the experiment's investigate target nuclei with lower cross sections and success, but the lack of a vacuum at the target re- more complicated energ\ spectra than those for quired that we include no-target runs for each spec- previously studied nuclei. trometer position. The no-target spectrum was later Specifically, the experiment consisted of elasticallv adjusted and subtracted from the appropriate nickel scattering positive and negative pions from 1llNi. h"Ni. M spectrum. The nitrogen elastic peak, for the most and Ni. The incident pion kinetic energies selected part, is not negligible, as can be seen from Fig. 1. were 50 and 65 MeV. The 65-MeV data were ob- Because of the kinematic energy shift brought about tained for scattering angles of 30, 40, 50, 60. 70. 80. by changing scattering configurations and the 85, 90, 95, 100, and 110°. using both positive and behavior of its elastic cross section, the nitrogen peak negative pions. The 50-MeV data were obtained only contributed somewhat to the nickel elastic peak at for negative pions at a few strategic scattering angles small scattering angles but much more to the first that were chosen to supplement previous work. Also, s M excited state at larger angles. Tnis makes the extrac- because of time constraints, only ' Ni and Ni targets tion of inelastic cross sections from the data rather were employed at 50 MeV. For scattering angles difficult. between 80 and 100° the acceptance was divided into three ">.3°-widc bins to better resolve the differential Despite the lack of an evacuated target chamber, cross section as a function of angle at the position of the energy resolution of the spectrometer was about the minimum. 600 keV, which is better than that produced by any previous device at this energy. The good energy The incident pion flux was monitored using scin- resolution and large statistics afforded by the spec- tillator telescopes placed well within the Jacobian trometer made it possible to discern a significant low- peak for the pion-muon decay of beam particles energy tail associated with ench peak in the energy — 1 m upstream of the target. The number of muons spectrum (Fig. 2). Rather than being an instrumental recorded by these detectors is proportional to the artifact, this line shape is most likely due to Landau fluence of pions. Calibration was achieved by straggling in the targets. Such a tail is anticipated by measuring hydrogen cross sections for scattering theory for the target thicknesses and probe kinetic angles of 50. 55. 60, 70. 90. and 100° during the energy used in this experiment. course of the experiment. This was accomplished by 46 PROGRESS AT LAMPF—1984

i i r

TT ' 65 MeV

Ni g.s- 9 -- 100°

XI >4N g.s. D

c o o

0 10 20 30 40 Missing Mass (MeV)

64 FIGLRF. 1. Missing-mass histogram for Ni and a background histogram from a no-targel run consisting mainly of 14N from air.

Jv = 65 MeV 0 =40°

in c 3 O u

0 10 20 Missing Mass (MeV)

GI RE 2. Missing-mass histogram for 58Ni at a a forward-scattering angle of 40°, showing long elastic tail that is due mainly to Landui straggling. RESEARCH—Nuclear and Particle Physics

Low-Energy Pion Single Charge Exchange i r • Experiment 850 — LEP 0° Los Alamos, Arizona State L'niv.

Spokesmen: F Irom and M. .1. Latch (Los Alamos) ^•00 -I

v. y Pion single charge exchange between 7\ — 30 and

80 MeV is qualitatively different from charge ex- XI V e'nar.gc r.eur ;hi.- n,\ (3-3) resonance. The total np cross section is 25 limes smaller than that at resonance, o \" leading to a substantially increased pion mean free O ;o path. Additio.-jlly. the s- and p-wave charge ex- (J change amplitudes undergo a nearly perfect cancella- c! X! V tion, which produces a very deep minimum in the I 7i /> - ri'n cross section at 0 . as shown in Fig. 1. Theexiension to isobaric-analog-state (IAS) transitions in nuclei offers several challenges to nuclear science. How does the deep minimum in the free 30 50 70 cioss section manifest itself in nuclei? Because it is a delicate cancellation, medium effects may substantially modify its appearance in nuclei. In fact, the FIGIRF. 1. The 0° n p —+ n"n cross section vs minimum is a sensitive tool for studying medium energy in the re«ion of the s-, /»-wave cancellation. effects. Nuclear theories must be able to predict the.I The data are from Exp. 808 and the curve is from dependence of the location and width of the mini- the C5 Phase-Shift Solution of Arndt. mum as well as the magnitude of the cross sections at 0°. Not only are the 0' cross sections rapidly varying but so are the angular distributions, 2nd their varia- manifestation of the interference. The angular dis- tions must be understood. tribution on i5N already has received substantial the- Data in this energy regime also are fundamental oretical treatment, which has led to the conclusion to unraveling a complete picture of low-energy that second-order terms in the optical potential arc re-nuclear interactions—that is, elastic scattering and necessary to cancel the first-order distortions.1 single and double charge exchange (SCX and DCX). The data have been extrapolated to obtain the 0° DCX involves two nucleons and it will be necessary cross sections plotted in Fig. 3. We observe that the to undeijinnd the iterated SCX contribution to DCX minimum is less pronounced in the heavier nuclei. before conclusions about exotic shon-range effects but persists as a feature. At the minimum, the cross can be made. sections are between 3 and 10 |ib/sr per excess neu- We present a significant body of data relevant to tron. The location shifts from -44 MeV in 'H to =60 the issues discussed above. The data set includes MeV in l:"Sn Thi- movement of the minimum is measurements from 'H. 'Li, I4C, I5N. WK. and !:"Sn for dramatic A number of theoretical groups are at- small angles and for energies from 3D to 80 MeV. In tempting to make their \heories reproduce these Fig. 2 we show the angular distributions for I5N. 1QK, measurements and to identify the nuclear medium and 1J;Sn. The data show a rapid change in shape, a physics necessaiy to explain them. 48 PROGRESS AT LAMPF—1SS4

"32.4 MeV • T

15N(Tr*,7r°)'50(IAS) Preliminary IO

4Q.7 MeV

100 .63.6 MeV

20 40 60 80

500 1 1 1 40.7 MeV 100 Sn(7T*TT ) Sb(IAS) 48 MeV : Preliminary 500-

10 S9K(Tr>°)S9Ca(IAS) 48.4 MeV Preliminary

w 500] - 56 MeV is io 56 6 Mev XI

50 -- ^ 63.6 MeV - 100 5 b b •o 64.1 MeV

100 500 -

79.2 MeV \?8.7 MeV

1 1 | 1 I 20 40 60 20 40 60

0lob(deg)

FIGURE 2. Forward-angie distributions for analog n+ single charge exchange on I5N, MK, and 120Sn. RESEARCH—Nuclear and Particle Physics 49

i ' r Pion-Nucleus Double Charge Exchange at I07- Low Energies

12OSnx5*IO5 • Experiment 884 — I.EP Los Alamos, Univ. of Wyoming, Arizona State Univ., s Virginia Polytechnic Inst. and State Univ., Tel Aviv 10 Univ.

39K X 10' Spokesmen: M.. I. Lei nil and II. If. Bacr (Los Al. 'u>s) Participants: E. Piasctzky, II. If. liaer.J. I). Bowman, R. L. Burman, B../. Dropcsky, P. I. M. dram, F. Irani, D. Roberts. G. A. Rebka, Jr.,./. wave amplitudes for SCX on the nucleon, and the effect persists for SCX on light nuclei. Conse- 10 quently, the contribution of two sequential SCX scatterings to DCX is expected to be suppressed. Optical- model calculations confirm this behavior, generally giving a flat cross section with angle. Thus, at energies 10 near 50 MeV the DCX reaction to the double- isobaric-analog state (DIAS) has an enhanced sensitivity to nucleon correlation effects. Recently. Miller- proposed that explicit quark ef- 10 30 90 fects play a strong role in DCX near 50 MeV. His model assumes that pairs of nucleons sometimes form a six-quark cluster in a nudeus. This cluster can Fiai'RK 3. Zero-degree cross sections on 'H (Exp. then contribute to pion DCX and produce a strong 808), 7Li (Exp. 688), UC (Exp. 523), I5N (Exps. 850 forward peaking in the cross section. Other standard and 401), 19K (Exps. 850 and 688), and I2llSn (Exp. mechanisms. Miller claims, do not produce this large 850) showing the change in depth and location of forward-angle DCX cross section while still giving a the minimum with A. small SCX cross section ai forward angles. The only previous DCX data at this energy1 could neither confirm nor deny this feature because of the large errors and the instrumental limitation of a forward Reference angle of only 50°. To establish the shape of the angular distribution I. M. D. Cooper. H. W. Bacr, R. Bolton, J. D. Bowman. and thus investigate these correlations or possible F Cverna. N. S. P. King, M. J. Leiich. .1. Alstcr. A. Doron. A. Ercll, M. A. Moinester, E. Blackmore, and six-quark bag effects, we have measured the cross M + IJ E. R. Siciliano. "Angular Distribution for section for C(7u .7t") O (DIAS) at 50 MeV for scat- lsN(7t+,7rl))15O(g.s.)at 7; = 48 MeV," Physical Review tering angles between 20 and 130° with a relative Levers 52, 1100-1103(1984). accuracy of ±10%. Details of the experiment are 50 PROGRESS AT LAMPf— 1984 contained in a paper that has been submitted to to extrapolate to the 0° cross sec!ion of 3.9 ± 0.5 Physical Ri stew Letters.4 The results show a strong ub/sr. forward peaking of the cross section and are consis- Figure 2 shows the energy dependence of the 0° tent with previous measurements.1 In Fig. 1, the cross section. One can see that the SCX and DCX DCX angular distribution at 50 MeV is shown with cross sections approach each other in magnitude near the SCX data for lsN(n+.jr())l5O (IAS). The 15N data, where one valence neutron is involved in the reaction, have been multiplied by 2 to approximate the 200 analogous cross section for the two valence neutrons involved in the SCX reaction on UC. One can see that the DCX cross section at forward angles is nearly as 100 - large as that for SCX. The solid curve is Miller's six- quark calculation, which predicts too high a cross section at forward angles but which Miller claims will be lowered when absorption is treated correctly. The l5 IS dashed line through ihe data was used to determine N(Tr>°:i 0(IAS) 48 MeV the angie-integraied cress section of 15.3 ± 1.6 ub and x 2 20

-Quark Model

1000 -

WC(Tr>-)l40(DIAS)

1.0

•o 10 —

o.i I L_ _L 0 20 40 60 80 100 120 140

1. The angular distributions of the cross section for 50-IVIeV pion single and double charge FIGURE 2. The 0° cross section for pion single and exchange to the isobaric-analog state. The "N double charge exchange vs energy showing the SCX cross sections have been multiplied by 2 to dramatic behavior in both near 50 MeV. The curve approximate ihe I4C SCX cross section. represents pi-nucleon charge exchange. RESEARCH—Nuclear and Particle Physics 51

50 MeV (both the SCX data above 80 MeV and the 6. P. A. Seidl, M. D. Brown, R. R. Kiziah, C. F. Moore, DCX data are published1"; the lower energy SCX H. W. Baer, C. L. Morris, G. R. Burleson, W. B. data are preliminary). Also, the DCX cross section at Cottingame, S. J. Green, L. C. Bland, R. Gilman, and 50 MeV is about the same size as that at 300 MeV. Ff. T. Fortune, "Pion Double Charge Exchange on T= 1 Nuclei," Physical Review C'30, 973-979 (1984). The existence of a six-quark cluster mechanism for 'DCX is supported but not proved by our measurements. More traditional models are being developed to explain these data and have met with some success. To distinguish between these various mechanisms, we will make further measurements to A Study of Neutrino-Electron Elastic establish the systematics of low-energy DCX with Scattering energy and with target nucleus (or A). Nevertheless, it • Experiment 225 — Neutrino Area is clear that these measurements have a strong sensitivity to nucleon-correlation phenomena and are an Univ. of California at Irvine, Los Alamos, I'nir. of Maryland important step toward understanding the nature and importance of the various reaction mechanisms. Spokesman: II. II. Chen (L'niv. a/California, Irvine)

References Introduction 1. M. D. Cooper, H. W. Baer, R. Bolton, J. D. Bowman, Experiment 225 is currently taking data at the F. Cverna, N. S. P. King, M. J. Leitch, J. Alsrer, A. LAMPF beam-stop neutrino facility. Goals of this Doron. A. Ere!!, M. A. Moinester, E. Blackmore, and experiment are E. R. Siciliano. "Angular Distribution for • to study neutrino-electron elastic scattering: l5 + l5 N(7c ,7t°) O (g.s.) at 7; = 48 MeV," Physical Renew • to search for anomalous sources of v,.'s from the Letters 52, 1100-1103(1984). beam stop—for example, from vM - v,. oscilla- + + 2. G. A. Miller, "Searching for Six-Quark Cluster Com- tions or from u --• e \'t\>v, as allowed by the ponents of Nuclear Wave Functions with the Pion- multiplicative lepton-number-conservation lav Nucleus Double Charge Exchange Reaction," Uni- • to study the inverse beta reaction on i:C; and versity of Washington preprint 4048-12-N4 (1984), • to search for neutrino decays. Physical Review Letters 53, 2008-2011 (1984). Initial studies show that cosmic-ray backgrounds are 3. I. Navon, M. J. LMtch, D. A. Bryman, T. Numao, P. being kept to the level of the expected neutrino- Schlatter, G. Azuelos, R. Poutissou, R. A. Burnham, electron elastic-scattering signal and that beam- M. HasinofT, J. M. Poutissou, J. A. MacDonald, J. E. associated events occur approximately at the ex- Spuller, C. K.. Hargrove, H. Mes, M. Blecher, K. pected rate. Gotow, M. Moinester, and H. Baer, "'Pion Double Charge Exchange ai 50 MeV on 14C." Physical Review Neutrinos are produced in the beam dump from + + Letters 52, 105-108(1984). decays of stopped 7t 's and slopped u 's. Because of the long pion and muon lifetimes relative to the 4. M. J. Leitch, E. Piasetzky, H. W. Baer, J. D. LAMPF beam microstructure. the neutrino-source Bowman, R. L. Burman, B. J. Dropesky, P. A. M. Gram, F. Irom. D. Roberts, G. A. Rebka, J. N. tim? structure follows the LAMPF beam macrostrue- Knudson, J. R. Comfort. V. A. Pinnick, D. H. ture and duty factor. LAMPF produces beam-stop Wright, and S. A. Wood, "The Double Isobaric neutrinos that are one-third v,'s with an average Analog Transition l4C(7i"t,7in)14O at 50 MeV," Los energy of about 40 MeV. whereas reactors produce Alamos National Laboratory document LA- primarily v,'s and high-energy accelerators are UR-84-2754 (to be published in Physical Review sources of v,,'sand v,,'s. Slopped 7t "sand stopped u 's Letters). are absorbed so that few u 's decay. Thus, the v,. flux 5. F. Irom, J. R. Comfort, R. Jeppesen, J. J. ICraushaar, is suppressed by a factor of at least 10". Recently the R. A. Ristinen, W. Tew, J. L. Ullmann, H. W. Baer, J. neutrino flux has been enhanced by the addition of a D. Bowman, M. D. Cooper, E. Piasetzky, U. Scnn- 20-cm-thick water degrader just upstream of the iso- hauser, A. Erell. M. A. Moinester, and E. R.. Siciliano. I4 tope production target and the beam slop. Details "Pion Single Charge Exchange on C," Physical /?e- concerning this flux are shown in Table I. wirr28,~2565-2567(1984). 52 PROGRESS AT LAMPP—19S4

TABI.K I. Neutrino Fluxes and Rates for Exp. 225.

Proton energy 760. MeV Proton current 600. uA Stopped 7i+ decay/proton 0.065 Stopped n+ decay rate 2.4 X 1014 b 12 : 1 v(. flux at 9 m 2.1 X 10 cm" day" Enhanced v,. flux l 2.9 X 10i: cnr; day ' 2.7 day"1 0.18 i.8 day""1 -Q = 0.23) n 0.12 (mA • h)"1 7.4 day"1 0.51 (mA • h)~'

•'Measured for 720-McV protons if an instrumented beam slop (see Ref. 2). then scaled to 760 MeV frc m a comparison with the results of a Monte Carlo calculation. b The vM and vM fluxes are each equai to the v,. flux.

The 20-cm H;O degrader is estimated to increase the neutrino flux by-40%. dCakulateii for a 15-mclric-t^n deiccior using a 20-MeV threshold.

Proleclion against backgrounds associated with The purely leptonic processes, unfettered by uncer- the beam stop is provided by a 6.3-m-thick iron tainties associated with hadronic corrections, shield. The iron thickness was selected to reduce provide critical testing grounds for theoretical ideas. backgrounds from the beam stop to a level below In the clectroweak theory of Glashow, Weinberg, and expected neutrino signals. The large 6 to 9% duly Salam (GWS). a weak neutral-current interaction factor at LAMPF poses a severe problem for neutrino arises from /" exchange. The strength of this interac- experiments in that the rejection factor against cos- tion is determined by sin~ 9,,, the one new parameter mic-ray backgrounds is very small compared to that in the theory. In the absence of this weak neutral- typically available at high-energy accelerators. There- current interaction, there is no 'v^.c elastic scatter- fore, the walls and roof of the LAMPF neutrino ing, and the weak charged-current interaction, al- facility consist of iron 1.0 m and 1.5 m thick, respec- ready given by V — A theory, gives a well-defined tively, to reduce backgrounds from the hadronic ' v,1, c clastic-scattering cross section.* component of the cosmic rays to a level below that With a neutral-current interaction. lvj, ,c~ elastic arising from the muonic component. scattering exists and {v].,c clastic scattering is modified by the additi- of the neutral-current diagram in Physics Goals the scattering amplitude. Because the cross section is proportional to the square of this amplitude, an The large fraction of v,.'s from the LAMPF beam interference arises between the two terms that is well slop makes it a unique source of neutrinos. This defined and that is predicted to be destructive by the uniqueness is exploited in the planned experimental GWS elcctrovveak theory.' This interference between program that focuses on v, physics. The primary goal the charged- and neutral-current weak interaction of Exp. 225 is to study neutrino-electron clastic scat-

tering, with particular emphasis on v,.e" -— \\.c . *Parenthescs in notations ' v' and ,V(*) indicate either "with" or ••without-" RESEARCH—Nuclear and Particle Physics cannot be measured anywhere else. Therefore, such a To identify cosmic-ray backgrounds, activity in measurement would be a critical and unique test of each of the 600 MWPCs and in each of the 160 the GWS unification of the electromagnetic and the scintillation counters is stored for 32 |j.s before a weak interactions. trigger with a time resolution of 400 ns. The time The expected v,,,ir elastic-scattering rates for Exp. duration is dictated by the muon lifetime and by the 225, for I' - .1. and for GWS with siir 9,, = 0.23 are anticipated cosmic-ray stopped-muon decay rate of shown in Table 1. With this rate we believe that an about 107 day '. accurate measurement of the elastic-scattering cross To identify the inverse beta reaction, v,,+ I2C — e~ section is possible. Thus, we may both demonstrate + |:N*. activity in each of the 160 scimillation the existence and determine the sign of this inter- counters is stored for n4 ms after a trigger with a time ference between /" and II" exchange diagrams. resolution of 16 us. This time duration is dictated by With the anticipated suppression of the v,. flux the 11-ms half-life of 1:N. from n" and u~ absorption in the beam stop down to The detector system has been in full operation for the level of 10~\ an observation of a \\. flux substan- the past year. Data have been collected for LAMPF tially larger than this would imply new physics—that cycles 38-41 and very likely will continue to be is. from vM - v, oscillations, or u' • C*V,A\, , as collected for the next two years. Our earlier dif- allowed by the multiplicative lepton-number-conser- ficulties with operation of the vertical lubes in the vation law. We expect a sensitivity to Am :, assuming flash chamber modules have been resolved, and the maximal neutrino mixing, at the level of 0.35 eV:, efficiency now is considerably improved. + and to R. the branching ratio for u —• i'*v,.vM, at the Examples of various events selected from our on- 1% level. line computer display are shown in Fig. 1 and include Using a long-delayed coincidence capability to tag (a) a penetrating muon, (b) a stopped-muon decay, (c) I2N beta decay, we expect to detect the inverse beta an interacting neutron, (d) a high-energy elec- reaction on 1JC—that is. v,.+ i:C -• c + I:N(*). This tromagnetic shower, and (e) an elastic-scattering can- would be the first direct observation of a neutrino didate. The left half of each figure shows the top view reac'ion on a nucleus other than the deutcron where and the right half shows the side view. : nucbar effects are relevant. The expected rate is The beam stop or neutrino source (shown at the shown in Table I. top of the figure) is about 7 m from the detector. The central box in the plan view outlines the sandwich Detector System detector, the horizontal lines in this box representing pulse heights in the corresponding scintillation The Exp. 225 detector system occupies the entire counters. The 160 counters are arranged in 40 planes accessible volume inside the LAMPF neutrino cave. of 4 counters each; the 40 flash chamber modules are An active anticoincidence, consisting of four layers of alternated with the scintillation planes. The output multiwire proportional counters (MWPCs), is used to from the vertical flash tubes is shown on the left; reject charged cosmic-ray events with very high effi- from the horizontal tubes, on the right. The three 5 ciency—that is, a net inefficiency of a few limes 10~ . small boxes on the far right show activity in the Inside this MWPC is a 13-cm-thick iron shield that scintillation counters before, during, and after the abso/bs neutrals (gammas) generated by muons. The trigger (top, middle, and bottom, respectively). iron shield is augmented by an additional 2.5-crn- The MWPC anticoincidence system is shown sur- thick layer of lead on the north wall and on the roof. rounding the plan view of the central detector. The The central target-detector system has a sensitive MWPC counters in the walls are standing vertically; mass of about 15 metric tons. It contains 40 layers of those in the roof and floor are lying horizontally, plastic scintillator 3 m by 3 m by 2.5 cm, alternated orthogonal to the central detector planes. There are with plastic flash chamber modules (5.v and 5r alter- four layers of MWPCs in the walls and roof and one nating layers/module). The scintillation counters layer on the floor. The roof and tloor MWPCs are measure energy as well as dE/dx. The flash chamber shown above and below the plan view, respectively. modules measure position and angle within each The filled-in bo,\es represent MWPCs in coincidence module, thereby minimizing the effect of multiple scattering. 54 PROGRESS AT LAMPF—1984

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FlGlRK 1. (a) Selected events in the detector from the on- line display; traversal cosmic-ray muon. (b) Stopped cosmic-ray muon decay. (c) Cosmic-ray neutron interaction. (d) High-energy cosmic-ray electromagnetic shower. (e) Elastic-scattering candidate.

BEAM UAS ON TTJTBL E>C3*?r « a PtV EVEVT MXSER • 42 HJ=C ROTE . E96E.e (e) RESEARCH—Nuclear and Particle Physics 55 with the event in the central detector; the crosses, a tew microseconds earlier; and the open boxes, up lo 32 (.is earlier. COSMIC-RAY RATES ELECTRON TUNE Cosmic-Ray Rates About 5000 charged cosmic-.ay panicles traverse the MWPC anticoincidence system per second. Of these, some 1300 s ' can generate triggers in the Td.Ap 9,000/day (800/9% day) central sandwich detector. With the application of a m "EJECTED 20-u.s veto from the MWPC anticoincidence system OBVIOUS < COSMIC-RAY EVENTS and with the scintillation counters tuned for low- /•<5D0/DAY 154/9-4 DA*; energy deposition events (electron tune), the T^-A,, Q CO trigger rate is about 0.10 s '. This trigger rate trans- o REQUIRE SINGLE TRACK lates to about 800 events per day with 9% beam-on o • lOO/DAY ! 9/3% DAY ) duty factor. The corrected scintillator energy spectrum for these events is shown in Fig. 2 (tola! energy deposited in the detector is about 1.6 times that deposited in the scintillator). Most of these are from WITHIN FORWARD 20 A • charged particles traversing the sandwich de- I«/DAY [1.3/9% DAY) tector (anti-inefficiency neutrals converting in the gamma shield). 45 £0 75 90 105 • neutrons interacting in the detector (producing SCINTILLATOR (MeV) the decay chain n -•- u » e). and • stopped cosmic-ray muons (decaying after FIGL'RF. 2. Scintillation spectra of cosmic-ray 20 us). events in million electron volts. Energy loss in the Removing these and focusing on low-energy Dash chamber modules is not included. (The total energy is estimated to be about 1.6 times the ( <40 McV deposited in the scintillators) single-track energy deposited in the scintillator.) Cuts used to events within the fiducial volume, the residual rate is reject backgrounds are described in the text. about 7% of the 7', • At, rate. This spectrum also is shown in Fig. 2. Applying tighter constraints on these single-track events (single-track in both views, clean- ing up thresholds. dE/d.x cuts, and energy deposition The corrected scintillator energy spectrum is shown in a contiguous group of scintillators). the event rate in Fig. 3. After imposing additional requirements, as drops, by another factor of 6. to 9 day"' with 9% duty for the cosmic-ray events, the corresponding two factor. An angle cut of 20° (16°) reduces this rate to spectra arc also shown in Fig. 3. These rates are about 1 1.3 day ' (0.8 day ') with 9% dut> factor. The energy 2.0 and 0.3 (mA-h)" . respectively. The reduction spectra of these evenis also are snown in Fig. 2. factors for the beam-associated events are not as large The expected rate for neutrino-electron elastic as those for cosmic rays, presumably because neu- scattering is estimated to be about 1 day""1 after the trino events are being detected. corresponding cuts are implemented—for example: Data were accumulated during the LAMPF beam- fiducial volume. dE/dx. and tracking inefficiency. In spill time and also when the beam was off. Typically, this way. cesmic-ray backgrounds are reduced to the the beam macroslructure was 750-us beam-on fol- level of the expected elastic-scattering signal. lowed by 7.55-ms beam-off. Beam-off data were taken approximately 4 times as long as beam-on data between the beam-on spills so that the uncertainty of Beam-Associated Rates the experiment was not dominated by the beam-off subtraction. The time-averaged proton current was The trigger rate with beam (Td- A,,- B(i). where 15 BG \z the beam gate, measures about 12 (mA • h)~'. ^600 uA (3.7 X 10 protons/s) with 760-MeV 56 PROGRESS ATLAMPF—1984

Bl'AM-ASSOCIATED EVENTS ELECTRON TUNE !

Z ED \ V) -3200 i i50 EVEN'S Z 10 UJ FK.I KK 3. Scintillation spectra of beam- 532 *A\ EVENTS associated events in million electron volts. Energy loss in the flash chamber modules is not included. cr (The total energy is estimated to be about 1.6 times UJ IC REQUIRE SINGLE-TRACK m 751 16 EVENTS the energy deposited in the scintillator.) Cuts used 5 to reject backgrounds are described in the text.

Id2 15 30 45 60 75 90 SC1NTILLATOR

kinetic energy incident on the beam stop for this data the hardware trigger. A fiducial volume cut was sample. imposed to remove events that passed through the The detector was pulsed approximately once per first or last layers of the detector or those that passed 10 live-seconds by events that passed the trigger re- within 5 cm of the side, top. or bottom of the de- quirements. Datn were recorded on magnetic tape tector. Events that had no reconstructable track in that represented the flash-chamber data, the pulse any view of'he flash-chambers also were removed. In height and limes of the coincident scintillator data, addition, high-energy events (those with energy de- the pulse height and times of scintillators that had posited in the scintillator of >60 MeV, corresponding > 1 MeV of energy deposited during the 32-us period to about 100 MeV total) were removed. These cuts, before the event, the pulse height and times of the designated as level 2 cuts, reduced the number of scintillators that had >2 MeV of energy deposited events by about a factor of 10. during the 64 ms after the event, and the history of Most of the remaining events were removed by the anticounters during the 32 us preceding the tightening the dE/d.x requirement. This cut removed event. In addition, calibration events of muons that many proton recoils and electron-positron pairs that entered the detector and subsequently decayed and came from neutron-induced events (both beam-as- muons that passed entirely through the detector were sociated and cosmic). Events that recorded energy in taken approximately every" 10 min. A total of about more than one contiguous group of scintillators also 3000 events was taken each day. Data were ac- were removed. These further cuts reduced the data cumulated for a total of 0.97 A • h of protons (2.2 X sample by about another factor of 10. :2 10 ) on the beam stop during LAMPF cycles 38-40. To decrease the sensitivity of the results to residual beam-associated neutron-induced events, cuts also were imposed requiring that at least four adjacent Data Reduction layers of scintillation counters have pulse-height pat- The first stages of dala reduction removed those terns consistent with a single electron, with a total events induced by cosmic rays that remained after recorded energy >35 MeV (total energy >55 MeV). RESEARCH—Nuclear and Particle Physics 57

FIGURE 4. Energy deposited in the scintillators for cosmic-ray muon decays. The Monte Carlo simulation is also shown. The gains of the counters were determined by minimum-ionizing particles passing through the entire detector.

10 20 30 40 Energy in Scintillators (MeV)

I i i (a) X Beam on Monte Carlo Simulation and Detection Efficiency Jt * o60u 0 O Beam oft in (Level 2Cu«s) A Monte Carlo simulation of the detector was o u X developed so that the response of the detector to 6 400 X electrons could be understood. This simulation in- o X n cluded radiative energy loss and production of sec- o » _ ondaries from photon conversion. The core was the in 200 °°o «, X electromagnetic shower EGS code.1 In addition, sev- 0 0„ 0 eral aspects of the reconstruction efficiency and re- c c .'o 8, ji , 1 solutions were understood by passing calibration 53 -, - events through the analysis code and by generating en (b) Final Cuts '. calibration events in the simulation. Figure 4 shows q the observed energy deposited in the scintillators for 3 : stopped-muon decays from cosmic muons. The IE 1) predicted spectrum, generated by the simulation and ui 10 -T I I filtered through i.he same cuts as required by the T I - analysis code, also is shown. The agreement provides 2 0 Til- ]} u confidence in the ability of the simulation to I i 1 1 1 duplicate the absolute energy scale of the apparatus. 10 0.8 0.6 02 00 By examining the sensitivity of the experiment to COS B possible uncertainties in the energy scale and to the analysis cuts, we are confident that we understand the FK;I RK 5. absolute efficiency of the detector and of the analysis (a) Number of events that pass the level 2 cuts code to ±8%. for both beam-on and beam-off vs the cosine of the angle between the recoil particle and the direction of the neutrino source. The Results events have been normalized to give an equal The results we have obtained to date are given in amount of live time to beam-off events. Fig. 5. which shows the angular distribution of events (b) Excess of beam-on events after final cuts vs the cosine of the angle between the recoil that have survived the trigger and analysis cuts. particle direction and the direction of the Figure 5(a) shows both the beam-on and beam-off neutrino source. Neutrino-electron scatter- angular distribution normalized to equal live times ing events are expected to concentrate near after the level 2 cuts. An excess of beam-on events is B = 0°(cos9= 1.0). 58 PROGRESS AT LAMPF—1984

clearly seen. Figure 5(b) shows the beam-associated scattering is [10.1 ± 4.6 (statistical) ± 1.8 (system- events that have passed all the analvsis cuts. The peak atic)] X 10 4:X /•; (GcV)cnr. with cos 9 > 0.96 is kinematieally consistent with v-e To search for events that could have been induced elastic scattering. A background of events that con- by v,. reactions either from v(, — v,. oscillations or tribute to the signal at all angles is also evident. from exotic rnuon decay, the kinematic regions cos 9 The contribution of beam-associated events from > 0.96 and recoil-elect'on energy <35 MeV (ob- neutron-induced events had been studied during a served energy <23 MeV) were eliminated. The angle series of measurements in which the shielding be- was chosen to eliminate v-e elastic candidates: the tween the beam stop and the detector was varied. The energy was chosen to be greater than that expected results of this study indicated that the background from the v,.-i:C - c-':N (all stales) reaction. The from neutron events near 0° was <5% of the expected Monte Carlo code was used to simulate the \\.p - — c+n + v-e rate. The peak near 0° contains 24.4 ±6.8 events; reaction. If 100% of the u' decayed to f vMv,.. we a subtraction of 4.0 ± 3.0 events is applied for events would have expected 80C ± 130 events to satisfy the that contribute at all angles. This leaves 20.4 ± 7.4 trigger and analysis requirements. As oiny 4 ± 9 events, consistent with v-e scattering. To compare events were observed, the ratio of exotic u decay to this number of events with theory, the GWS predic- normal u decay was !e:.s than 0.022 at the 90% tions for sin: 9,, = 0.22 were generated in the simula- confidence level.

tion, which included the neutrino flux and uncer- For neutrino oscillations of the tyje vv —- \\., the tainty (±12%), the efficiency and uncertainty of the expected number of v,. for an initially pure state of v, : absolute trigger and the energy-deposition efficiency is A X siir(26m,x) sin [1.27 LfAmf/K]. where A' is for forward-going recoil electrons (±8%), and the the initial number of vM, the Am is the mass dif- reconstruction and cut efficiency (±10%). The simu- ference between the two neutrino mass eigenstates in lation predicts that 17.6 ± 3.2 events would have electron volts with mixing parameter sin 9mix. the L is been seen for destructive interference. Likewise, we the distance from the beam stop to the detector in would have expected 48.5 ± 8.7 events for construc- meters, and /: is the energy of the neutrino in million tive interference and 33.1 ± 6.0 events for no inter- electron volts. Integrating the acceptance over the ference between the neutral and charged currents allowed ranges of L and /•„", we find that the Thus, the preliminary results of this experiment to asymptotic limits for neutrino oscillation at the v0% : : date show agreement with those expected from the confidence level are (A/;/) < 0.61 eV [large : : 2 GWS model with destructive interference and rule sin (28mlJ] and sin (29nm) < 0.044 [large (Am) }. out constructive interference at the 90% confidence level. The uncertainties are presently too large to Future Plans claim that the interference between the charged and neutral currents has been observed. We took data for several more months this last To extract a cross section for \\.-c elastic scattering, summer (1984). using additional shielding that re- the contribution of vp- and vM-induced events must be duced the cosmic-induced backgrounds by about subtracted. Using the GWS model for the recoil- 25%. We also reduced the trigger thresholds to in- electron distribution with current values for the cross crease the low-energy efficiency of the detector. This sections for vM-f and v^-e scattering and the flux of vu winter, additional material will be placed between the and Vj, from the beam stop, a 0.7 ± 0.2 event would be beam stop and the detector to reduce the beam- expected in this sample from vu-e scattering, and associated signal from neutron-induced events. In 3.2 ± 0.9 events would be expected from vv-e scatter- addition, a separate experiment will be conducted ing. This is not significantly different from the num- that will determine the neutrino flux per incident ber of vM and vM events that would be subtracted by proton frjm the LAMPF beam stop. We expect that using GWS predictions with sin: 9,, = 0.22. Thus the we will be able to increase the efficiency and conse- data are left with 16.4 ± 7.4 events, consistent with quently reduce the uncertainties of the analysis com- v,-e scattering. The total cross section for v,-e clastic pared to the Monte Carlo simulation of the performance of the detector. These factors should allow the RESEARCH—Nuclear and Particle Physics 59 systematic uncertainties to be reduced to below porting a finite neutrino mass is open to question.) ±10%. We also expect .1 substantial increase in the The weak-interaction theory is beautiful in its sim- sample of events consistent with \\.-c scattering. plicity, but the purpose of the experiment is to determine whether that beauty is more than skin deep. We plan to measure the spectrum with high resolution References and statistics 100-fold greater than the statistic^ I. B. k.ayser. L Fischbach. S. P Rosen, and H. Spivack. previously obtained. We will compare the spectrum 7 1 I'hvsn-Lil Review I) 20. S (l^7 )). with its well-known theoretical value. 1 T. W. Donnelly. Ill'Ci')i'>rrn,T I'nieeetlinxs 26,454

Time-Projection Chamber v R. 1.. Ford and W. R. Nelson. •'The F( is Code System: ('•Hnputer Programs for the Monte Carlo The positron momentum spectrum is measured in Simulation of Electromagnetic Showers (Version a spectrometer based on a time-projection chamber 3)." Stanford I.incur Accelerator report SLAC-210 (TPC) in a solenoidal magnetic field. Muons are l'C-.V. (I'-fS). stopped near the center of the chamber and decay there. The positrons that are ihen emitted move along a helical path because of the magnetic field. The TPC makes it possible to reconstruct the positron trajectory and determine its momentum and angle of emission. High-Precision Muon Decay The TPC works in the following way. The positron • Experiment 455 — P3 ionizes the gas along its trajectory. There is an axial electric field parallel to the magnetic field in the TPC Los Alamos, I niv. of Chicago, Sational Research Council that causes the electrons from the ionized fjas to drift in Canada, SIS toward the read-out plane at one end. The read-out Spokesmen ILL. \iu!cr\cn diij II II' kimii\on (Los plane is an array of proportional chambers that reads lhi')i>>\i out the A" and r coordinates of a number of points l'dv;nipdiU\-.1 I). Bowman..! II . Lillhcrv., M. S. Yam;, along the trajectory. The r coordinate is obtained by- ('. k lldi\'rnvc. and I. /ihnth;- measuring the relative lime of arrival at the read-out plane of segments of the helical track. The detector Introduction arrangement is shown in Fig. 1. The measurement of the positron spectrum of A typical event is shown in Fig. 2. In this figure the muon decay is one of the most fundamental experi- muon entering from the top is shown together with its ments in particle physics because it is the best way to decay positron, which moves in a helical path in the determine the character and strength of the weak upstream direction. interaction. We are making a new measurement with the goal of improving the existing limits on the interaction by a factor of 5. The spectrum can be Muon-Spin Rotator calculated precisely from the accepted theory, which For the most precise measurement of p (the Michel is based on a simple symmetry proposed by Feynman parameter that describes the momentum spectrum), and Ciell-Mar.n. In it the neutrinos are massless. with it is advantageous to remove any angular dependence two rather than four components. The theory is also resulting from the polarization of the muon. Because characterized by the fact thai the only interactions are it is difficult to depolarize the muons completely, we vector and axiai vector, of equal magnitude and are planning to ur.c a muon-spin rotator to turn the opposite sign, referred to as I — .!. In this theory the spin of the muon 90° from the direction of its motion. currents are purely left-handed. All searches to date In the magnetic field of the TPC the muon will to find right-handed currents or massive neutrinos precess in such a way that angular effects will be have been unsuccessful. (A Russian experiment re- averaged to zero. This provides an internal check on 60 PROGRESS AT LAMPF—1984

TPC CANISTER B HIGH VOLTAGE TOWER POLE HANDLER

SCINTILLATOR v BEAM DEFLECTOR-

ELECTRONICS RACK -BCAM

IRON YOKE-

-COILS

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-HIGH VOLTAGE ELECTRODE

FIGURE 1. A plan view of the apparatus. The electrostatic deflector/separator is used to improve beam purity and to turn off the beam when a muon enters the chamber. The iron-enclosed solenoid produces a very uniform magnetic field up to a maximum of 6.6 kG. This field strength ensures that positrons, resulting from muon decay in the center of the 52-cm-long by 122-cm-diam TPC volume, stay within the chamber.

FIGURE 2. The positron and muon track from a typical event. The muon coordinates are indicated by the letter M\ the positron coordinates are indicated by the boxes. The figure shows the straight-line fit for the muon track and the helix fit for the positron track. RESEARCH—Nuclear and Particle Physics 61 the data. The spectrum obtained should be independ- ,- = 25° > -• 240 MeV ent of the angle of positron emission.

1.6 Results to Date In earlier runs of this apparatus we have obtained a \.z momentum resolution of 0.7% Ap/p for a measured Michel spectrum at low data-acquisition rates. Since 0.8 then we have raised the data-acquisition rate to —60 events/s. We are looking forward to a data-collection 0.4 run in June 1985.

o.o

l Inclusive Pion Double Charge Exchange > in "He I" *"• Experiment 750 — P3-West Ml T, Univ. of Wyoming, Los Alamos Spokesmen: P. A. M. drum (Los Alamos)../. R. Matthews (MIT), and (i. A. Rebka. Jr. diuw of Wyoming) Participants: /:'. R. Kinncy.J. L. Matthews, (i. A. Rcbka. Jr.. D. I. Roberts. P. A. M. dram, D. IV. MacAnhur. and E. Piasetzky

40 In this experiment we have extended our study of Ca(Tr\TT-)X inclusive pion double charge exchange (DCX) to 4He. the smallest nucleus in which this reaction can be investigated by both positive and negative pions. The purpose of these measurements is to iliuminate the problem of pion multiple scattering in nuclei by discovering the systematics of DCX. in which double scatteri-g is the leading-order contribution. Specifi- cally, we are investigating the dependence of the inclusive DCX cross sections on the incident energy of the pions and the atomic number of the target. In 4He one expects to see nearly pure DCX involving 40 80 120 I6O 200 240 two, and only two, nucleons. The observed doubly V(MeV) differential cross sections can be compared with those for DCX in heavy nuclei where evidence has FIGI'RE 1. Comparison of the doubly differential been uncovered that more than two nucleons cross sections observed in DCX reactions at 25° participate and that pion scattering and absorption with 240-MeV positive pions incident on 4He, I6O, are important competing processes. Moreover. 4He is and J|lCa (top to bottom). a simple nucleus for which a realistic theoretical description of pion multiple scattering may be trac- these reactions in '"O and 4"Ca (Refs. 1 and 2). Figure table. 1 compares energy spectra from these three nuclei ai. 4 For both the (n'.n) and (JT.TI") reactions in He, a positive-pion incident energy of 240 MeV and an we found that the energy spectra of the outgoing outgoing pion angle of 25°. The smooth curves in the pions differed remarkably from those produced by figure represent the distribution of events in four- 62 PROGRESS AT LAMPF—1984

4 T_.« 240 MeV body phase space for the '"O and "Ca spectra and in five-body phase space for the 4Hc spectrum. All of the curves are normalized to pass through the data point at 50 MeV. In "'O and 4"Ca the data qualitatively resemble phase space, exhibiting a single peak centered at low outgoing pion energy, whereas in 4He there is a prominent second peak at a higher energy. Figure 2 illustrates the behavior of this peak in the 4He spectrum as the angle of observation is increased while the incident energy is held fixed. The peak moves toward lower energies and diminishes in size, gradually merging with the phase-space-like spectrum, but it is still visible at 130°. As the pion incident energy is decreased, the peak becomes less prominent, remaining visible in the forward direction at 150 MeV and disappearing entirely at 120 MeV. The doubly differential cross sections for the {K\K )4p and the (n ,n*)4n reactions are nearly indistinguishable. One's first reaction is that some or all of the outgoing nucleons form a resonance, but the missing mass represented by the outgoing pion 80° - energy at the centroid of the peak is not constant as - the outgoing pion angle is varied. We have not dis- I 2 - covered a /cvra-neutron (or a to'ra-proton). A similar peak has been seen in an early measure- - ment of DCX in 'He by Sperinde et al.1 With only one 1 example derived from a range of forward angles at an b 04 1 • incident energy of 140 MeV, they could not test for

• the formation of an object with constant missing i . i . : i . i . i * « . 00 mass. A calculation by Phillips4 showed that this peak J I S 105° in He could be explained by a final-state interaction effect. A corresponding calculation for 4He has not yet been performed. Stetz et al.5 failed to observe peaks in their measurements of 4He DCX cross sections because of an unlucky choice of incident energies and the limited energy range of their detection system together with the poor statistics of the data. We have very recently (Exp. 859) discovered a remnant of this structure in the spectrum of DCX in "Be. These data are presently being analyzed and will be presented in a future report. To gain some insight into the mechanism of the DCX process. Wood'1 performed a simple Monte

FIGURE 2. Angular dependence of the doubly differential cross section of DCX in ''He at an incident 0 40 00 120 160 200 240 positive-pion energy of 240 MeV. RESEARCH—Nuclear and Particle Physics 63

Carlo calculation in which a pion undergoes two Measurement of the Asymmetry Parameter sequential single charge exchanges in a nucleus as- in n~ + p — Y + n Using a sumed to be a degenerate Fermi gas of nucleons. At Transverse Polarized Target the energies of interest the free pion-nucleon cross 3 • Experiment 804 — P sections used to describe the two interactions have a (14 3 cos: 9) angular dependence. Thus DCX pions UCLA, George Washington Univ., Catholic Univ. of emerging in the forward direction have a high America, Abilene Christian Univ., Los Alamos probability of having been scattered, either twice Spokesman: B. M. K. Neikcns(L'CLA) through a small angle with small loss of energy or twice through a large one with a large loss of energy. The stated purpose of Exp. 804 was to measure the Reflecting this possibility, the model duly predicts a left-right asymmetry parameter As in the reaction doubly peaked pion energy spectrum at forward 7i" 4 p — y 4- n [radiative exchange (REX)] in the angles that qualitatively resembles the 4He data. energy region from the Delta A" (1232) to the Roper However, this model does not reproduce the energy, P"{ (1400) resonances. This goal was achieved with a width, or angular dependence of the peak. Wood's statistical error in As that is expected to be approx- model was intended to simulate DCX in oxygen and imately ±0.025 when the analysis is completed. With calcium, for which, of course, no double peaking is similar accuracy we simultaneously determined the apparent in the data. A simpler calculation of the parameter A s in the reaction n" + p - •• ;t" 4 n [charge convolution of two free single charge exchanges, us- exchange (CEX)]. Data were taken at the angles and ing Gaussian momentum wave functions for ""He, energies listed in Table I. recently has been performed by Thies.* Preliminary The experimental setup and the Los Alamos P- results again only qualitatively agree with the ob- Division polarized hydrogen target that we used are served pion energy spectra. Although these simple shown in Fig. 1. The properties of the target are given models cannot be expected to achieve quantitative in Table II. The incident pions (~107/s instan- success, one may have learned that a two-step se- taneous, ~ 107s time average, depending on the duty quential-scattering model is the right starting place factor) were detected in a pair of 1.6-mm-thick scin- for a quantum mechanical treatment and that more tillation counters SI and S2 located 60 cm upstream exotic processes such as those involving exchange of the target. currents or A production may play only a small role The final-state neutron and gamma were detected 4 inDCXin He. in coincidence. The gamma detector consisted of 15 elements arranged in a 3 X 5 rectangular array. Each element was a 1.5- by 1.5- by 2.5-cm-deep lead-glass "Information irom M. Thics. SIN, 1984. block optically isolated from its neighbors and viewed by its own 12.7-cm photomultiplier tube. The neutron detector assembly also consisted of 15 elements, each of which was a cylinder of plastic scintillator 7.6 cm in diameter and 45.7 cm long, viewed References by an RCA 8575 photomultiplier tube. These were 1. E. R. Kinney et al.. Bulletin of the American Physical arranged such that each element corresponded lo a Society 29, 1051 (1984). unique gamma element, as dictated by the kinematics of the two-body final slate of the REX 2. S. A. Wood et al.. Physical Review Letters 54, 635 (1985). reaction. Radial distances of the detectors were typically 3. J. Sperinde ei al.. Xuclcar Physics B78, 345 (1974). between 2 and 3 m. The distances were chosen on the 4. A. C. Phillips. Physics Letters 33B, 260 (1070). basis of Monte Carlo calculations used when we 5. A. SletzetaL Physical Review Letters 47, 782 (1981). searched for an acceptable compromise between a large REX signal to CEX background ratio and a high 6. S. A. Wood. Ph.D. thesis, Los Alamos National count rate. The final values did not provide com- Laboratory report LA-9932-T (1983). pletely unique matching, but there was always a probability of >90% that for any REX event the 64 PROGRESS A T LAESPF— 1984

TABLE I. Measured Momentum-Angle Pairs. REX = radiative exchange; CEX = charge exchange. REX REX CEX CEX Incident Neutron Neutron Neutron Neutron Neutron Pion Angle Angle Momentum Angle 1Momentum Momentum (lab) (cm.) (lab) (cm.) (lair)

301 47.5 90.0 351.6 96.5 309.8 301 71.5 130.0 209.6 143.5 144.2 316 47.5 90.6 362.6 96.6 322,3 316 71.5 130.9 213.3 143.6 149 6 427 45.4 90.0 458.0 93.6 426.7 427 34.9 70.0 535.3 12.5 507.1 471 44.9 90.0 492.7 93.1 467,4 471 34.5 •70.0 576.9 72.1 550.7 547 44.1 90.0 552.5 92.3 5269 547 33.9 70.0 647.8 71.6 6244 586 43.8 90.0 582.2 92.0 558.0 586 33.6 70.0 683.5 71.4 661.2 625 43.4 90.0 611.3 91.8 588.2 625 35.8 75.0 693.3 76.4 671.8 625 ;>8.4 60.0 764.7 61.1 743.9 625 51.3 105.0 520.2 107.4 494.9

gamma would intersect the clement corresponding to neutron detector elements were rearranged to the one the neutron was detected in. Radial distances preserve the one-to-one neutron element-gamma of both the neutron and gamma detectors were element matching. changed as the scattering angle and/or incident pion Preceding the neutron and gamma detectors were momentum were changed. At the same time, the charged-particle veto counters, named VN and VG,

TABI.F. II. Polarized Target Properties.

Target material Ethylene glycol Hydrogen by weight 9.15% Density- 0.812 g/cm3 Target shap; Truncated sphere, 4.6 cm diameter, 2.8 cm high Target temperature <0.5K Magnetic field 25 000 G Polarization Achieved by active pumping with 70-GHz microwaves Vei tical, perpendicular to the scattering plane Typically 80% for both spin up and spin down RESEARCH—Nuclear and Particle Physics 65

'• •'./'•

'••*•'•;';- *•••', ——

Open for Dewar

RK 1. P'-East floor plan for Exp. 804. respectively. An event was defined as a six-fold coin- ments, to correct for any differences, and to remove cidence, any time jitter in the gamma elements. After these corrections were made, the recorded information was EVENT = SI • S2 • IN • IG • VN • VG , used to distinguish our signal events from each other.

n + p • y + n (1) where IN (IG) is a logical OR of the 15 neutron (gamma) elements and where VN (VG) is the anti and of VN (VG). There were two such pairs of neutron- gamma detectors, each pair with a completely n + p • n"+n separate set of electronics. This allowed the measurement of two angular points simultaneously. For each 10 lhs) --• 2y + n , (2) event we recorded both the pulse size and time of all the neutron and gamma element signals, and the time as well as from ihe background reactions of SI. S2. and the 200-MHz rf pulse on which the accelerator was timed. All times were measured relative to the gamma element that triggered the event. K + X - n+ Y (3a) The time of the rf pulse was used to determine the relative timing of all the neutron and gamma ele- and 66 PROGRESS AT LAMPF— 1984

7i + .V • n" + n-r Y We are interested in the asymmetry and thus do not need tu know an absolute cross section. The s) (3b) asymmetry is defined as

Here, Vis the 91% (by weight) of I: he target that is not hydrogen and V is everything else in the final stale. Both the time of flight of the neutrons and the pulse .\'t size of the gammas were very useful in separating a large fraction of the background events from the signal events (see Fig. 2). The timing information also where N] is the number of events (including back- was useful in distinguishing between the REX and ground) for a spin-up target run. A'} is the number of CEX evenls in the low-energy runs. For the runs at events (including background) for a spin-down target higher energies, geometry was the only means of run. and B is the number of background events. The separating our two signal evenls. The REX reaction number of events is normalized by beam flux and yields the only true two-body final state, which in target thickness. For the CEX reaction, A'j and h'[ are turn specifies the one-to-one matching between the simply sums of the number of event1; in the non- neutron and gamma elements. The CEX reaction diagonal and nonadjacent elements of the 2D histo- initially produces a two-body final state whose gram discussed above. This eliminates all REX kinematics is very similar to that of the REX reac- events, leaving only events from the nonhydrogen tion, but the IT" decays instantaneously (— 10 u' s) to material in the target as background. The number of yield two back-to-back gammas in the n" rest frame. these events is determined by using the results of the These gammas arc folded forward by the Lorentz background runs in which the target material was transformation to the isb frame and illuminate the replaced with Teflon beads (C:F4). In determining As entire area covered b\ the gamma detector. The small for the REX reaction, one considers only the events non-uniformin in this illumination is calculated in that lie on the diagonal of the 2D histogram. For the our Monte Carlo program. background in these elements, one uses the average If one numbers the detector elements (see Hg. 3) number of events found in the nondiagonal and such that neutron element 1 corresponds to gamma nonadjacent elements. This number is corrected for element 1. etc.. when using the REX kinematics, and the non-uniformity between these and the diagoaal then creates a two-dimensional histogram of the elements as predicted by our Monte Carlo calcula- number of events for each neutron elernent-gamma tions. This correction must be made for both the element combination, the REX events should lie spin-up and spin-down runs because the background only on the diagonal whereas the CEX events are CEX reaction is spin dependent. distributed over the entire histogram. This would be the ideal situation. As is seen in Fig. 3, the real situation is a little more complicated. As previously mentioned, we did not have perfect one-to-one Results matching, which resulted in a slight enhancement in Some very preliminary asymmetry values are the 2D histogram where adjacent elements were hit. shown in Figs. 4 and 5. In determining these results For example, if neutron element 8 were hit. then for the Monte Carlo calculations have not yet been used, REX one would have by far the most events for nor have the various cuts applied to the data been gamma element 8. but a few cents also would be optimized, nor are all the runs included. found in the adjacent elements 3. 7. 9. and 13. RESEARCH—Nuclear and Particle Physics

Gamma Counters Neutron Counters i——r 1 i i 180 - "I "1 1 1 1 1 : The cuts shown in (b) The cuts shown in (a) have been applied. have been applied. 140 -

\00

(a) (b) 20 CEX CEX Ll_ I 30 T 40 "50 60 70 BO 10 20 40 50 60 70 80

30 I T 1 I The cuts shown in (c) 25 have been applies.

The cuts shown, in (d). have been applied. 10

I (O . 5 (d) REX REX ill I 50 60 70 80 ( 10 20 30 40 50 60 70 80

No cuts have 80 No cuts hove 45 -• been applied. been appled.

35 60

15 20

(e) (f) Teflon target Teflon target A 1.1 III ll I I 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80

Fi<;i KK 2. Pulse-size spectra for one of the gamma counters (left column) and eime-of-flight spectra for tine of the neutron counters (right column): lop: results from a normal target run. looking at only those events from nondiagonal and nonadjacent elements: Middle: results from a normal target run, looking at only those events from the matching elements; and Bottom: results from a background run, corresponding to the events shown in (a) and (b). The arrows indicate the cuts applied to the data during the normal analysis. Note that there is no upper limit applied for (c). 68 PROGRESS ATLAMPF—19S4

Gamma Array Neutron Array

5 IO 15 I 6 II

4 9 14 2 7 12

3 8 13 3 8 13 Beam 2 7 12 Into 4 9 14 Page

I 6 II 5 10 15

0 0 2 1 2 » 3 1 1 0 1 2 0 Q ill 14 0 l 4 1 * 0 a 4 4 0 (ji © 0 s » k 13 » b 0 J 2 j & 2J & 4 12 i 3 i * 1 3 0 3 0 5 21 sD 3 11 * 1 7 3 0 m 2 3 » 0 3U 0 0 1 2 10 2 2 J a 0 1 J 0 H ] 1 7 Q

9 0 2 1 1 * 0 1 3 si* 13 G' 1 a 1 3 B * J 3 > * & 2b © 1 . i a . 0 J ^ S b 1 '?.' 30 0 4 1 E 0 3 i 4 1 3J B & * 1 1 LZJ 1 3 . 3 13 5 ! a 2 1 1 3 1 * 1 3 © 37 'HI; 0 0 1 Q t 1 1 4 3 i S 2) 0 J 1 7 0 3 3 1 2 2 1 32 2 D 4 4 1 1 s 1 3 1 G> @ a 1 G1 3 2 0 s • 2 - 1 1 6 8 IO 12 16 Neutron 7 3 1 b j B 10 11 ,. 1 s 11 Neutron Counter # Counter Gamma Counl«r

Fica KK 3. Labeling used for the detector elements and the resulting two-dimensional histogram showing neutron element- gamma element correlations. The circles indicate adjacent elements above or below the matched counter; the squares indicate adjacent elements to the side of the matched counter. The cuts shown in Fig. 2 have been applied to the data.

O 3

et a|. FK;I HI 4. F.xcitation function of Ay, for the REX reaction at B = 90°. The solid line is the result of the Tokyo multipole analysis (Ref. 1).

O IOC 200 300 400 500 600 Temperature (K) RESEARCH—Nuclear and Particle Physics 69

0 8 p(-rr")-30l MeV/c

0.6 0.4 r / 0.2

60 120 130

• i 0 8 A D(ir~) •316 MeV/c 0 6 - / \ 0 4 - / \ 30 60 90 120 150 180 0.2 - / - \ 9 (deg)

i i i j i 60 120 180

FK.I RK 5. Comparison of our asymmetry results for the CEX reaction at pn =-- 301, 316, and 471 MeV/c with the results from the Karlsruhe-Helsinki partial-wave analysis (Ref. 2).

References 1. I. Irai. in ihc "'Proceedings of the IVth International Conference on Baryon Resonances." Toronto. On- tario. Canada (1980). p. 93. 2. G. Hohler ct al.. "Handbook of Pion-Nudeon Scat- tering." Physics Data 12-1 (1979). 70 PROGRESS AT LAMPF—1984

Investigation of the A/A Interaction Stoler et al. to study the pA[) angular distribution in Through n+d - pn+n the reaction yd • ppn'] at /-.', = 380 and 450 MeV. which also corresponds to \/T= 2.23 and 2.28 • Experiment 825 — P3 GeV/c:. Rice Univ., Univ. of Houston A thorough understanding of AW interactions, Spokesman: G. S. Alutchier(Rice Univ.) .specially of the anomalies that have caused specula- tion of the existence of dibaryons, requires detailed Experiment 825 was mounted at the P3 pion beam study of the elementary AW, AA', and AA interactions. at LAMPF, and data taking was completed. This Deuteron breakup studies can be used to isolate an experiment investigated the nucleon-A interaction interacting AA' pair in the laboratory. Photon-in- through the reaction K'CI — pn'n. We used a two- duced reactions have the advantage of forming a A" in arm apparatus with a magnetic spectrometer to deter- the deuteron by the well-understood electromagnetic mine the reaction kinematics and thus measured interaction. Pion-induced breakup, on the other exclusive cross sections. During this experiment we hand, generally produces more A's and forms aA" in ++ measured the excitation function for A production the final state with very little interference from at cenier-ot-mass production angles equal to 55 and nonresonant terms [Fig. l(a)-(c)]. Both types of reac- 90" over an energy region encompassing possible tions are important in studying the A.Y interaction. dibaryon resonances. We also measured the angular The kinematics of this nd experiment was chosen to + distribution of A ' production at two energies, Tn = emphasize the K+

TT-

(a)

(c)

1. Contributions to the nV - pn n (a) quasi-free scattering; (b) n!\ final-state interaction; (c) AW final-state interaction; + (d) A"n interaction, direct; and ^ A (e) A "*n interaction exchange. -TT+

(e) RESEARCH—Nuclear and Particle Physics 71

n\~ • npn and by choosing the final stale to require M s = 1232 MeV. It is possible to simultaneously choose kinematics that restrict the mass of the n"n subsystem to less than I I 30 MeV. well off resonance TT+ (Fig. 2), so that interference from the A* in the final slate is minimized. The result of such a choice is that of all the contributions to the n'd > pn' n reaction (a) shov;n in Fig. I. diagrams (d) and (e) arc emphasized at the expense of the others. We hope then to provide good-quality data to test various theoretical approaches to understanding the .VJi interaction. The actual laboratory angles and energy settings studied are shown in Table I. Although final analysis + has not yet begun, preliminary estimates indicate ihat A a statistically significant number of events ha\e been recorded at each selling ( - 1000 events per momentum bin) in the kinematic reg'ons of interest, with the possible exception of the three largest production

angle settings where BN > 100° in the center of mass. In addition, data on reference reactions [(n'd • pp. n'd • 7i7"' quasi-free scattering, and 7t7> * n'p elastic scattering (see Table 1)] will be used lo calibrate the absolute cross sections to better than FIGI/RE 2. Then+d -- piCn 10% accuracy. Figure 3 illustrates one of the histo- (a) laboratory system and grams obtained in the preliminary on-line analysis. (b) center-of-mass system.

TABLE I: The 0,,. H,, [see Fig. 2(a)j for Various Laboratory \ngles and Energy Settings.

n d n'pn for H = Pion Beam N n+d — pp (cm.) Momentum Quasi-Free forOs=90° (MeV/c) (GeV) 30° 45° 60° 75° 90° 105° 120° Scattering (cm.)

312 2.20 80.55 55.80 103,30 75.75 350 2.20 95.35 86,45 75.53 65,67 5';.75 37,105 98,31 74,74 387 2.25 75.80 42.82 73,73 <25 2.29 93.30 80.42 70.5(5 65.55 58,65 50.77 38.91 30,105 96,31 72,72 485 2.33 60,50 35.80 94,31 71,71 ?45 2.38 60,48 33.76 94,30 70,70 600 2.42 58.46 30.75 92,30 69.69 72 PROGRESS AT LAMPF—1984

9. • 60° ,ab 9D • 50° lab 300- 9a - 55° center of mass

O O Ku.i m 3. On-line analysis of the number of counts vs pion momenta for the reaction K d • n'pn for a beam momentum of 485 MeV/e.

P, MeV/c

Studies of the Spin Dependence of been upgraded to run on the Bonner Labs VAX pfp - nX computer system. This program will determine the • Experiment 336 — EPB energy and angular dependence of the acceptance of the apparatus and also will provide sample data to Rice tniv., I'niv. of Houston, Los Alamos serve as a known input to the data analysis program. Spokesmen: (i S. MuhhkrlRicc I'niv) and!.. S. Pinskr These data will help determine the sensitivity of the (inn: of IIOUSIDIII analysis to the decay of the final-state pion or to such factors as detector or magnet misalignment. Analysis of the pp --• /ITT/I data obtained in Exp. The spin asymmetry and cross section for the 336. phn^e II. is in progress. This kinemaiiealK com- reaction p\p —• ppn" was analyzed previously, the plete experiment measured the cross section and results are included in a thesis b\ P. V. Pancella.: Also analyzing power for the reactions p}p - pn'n and included in that thesis are the predictions of Dubach P\P —• /W at incident proton energies of 500. 650. et al.' using a rclativistic model of the one-pion and 800 McV. The kinematic conditions were chosen exchange force, which imposes three-body unitarity to correspond to A" production at cenier-of-mass constraints. The predictions included in the thesis angles ranging from 0 to 90°. These data, in conjunc- and shown in the 1983 Progress Report were tion with the data from phase I at 800 McV (Rcf. I). averaged over the experimental phase space. The span the region from where pp scattering is domi- model succeeded in predicting the general shape of nated by spin-singlet amplitudes (/. = 0. .VA system) the asymmetry throughout the region of interest but to where the spin-triplet amplitudes (L = I. ,VA overestimated its magnitude in some case The fits system) make a substantial contribution. Such an to average cross section were generally poor, with the excitation curve should prove sensitive to the theoretical predictions being closest to the measured proposed 'D: dibaryon resonance at \ v= 12175 values at 800 MeV. MeV. Dubach et al. found significant errors in their The computer program used to analyze the data computer codes in the spring of 1984. Incorporating from phase I has been modified to handle phase II these corrections resulted in small changes in the and to make preliminary checks of various calibra- polarization and large changes in the cross sections tions. Another program used in phase I to perform a for the reaction pp • ppn" (Fig. I). However, little or detailed Monte Carlo simulation of the apparatus has RESEARCH—Nuclear and Particle Physics 73

3 a - P«P —"• 00^" iOC MeV J o a h P»P—»PPir° 647 M«V 20"i 9 < 25" _ 24° < 9, £30" 18" < 9,<24* 3 4 2 ~ 'C^~"— j 04 - 3 i

04 -1 o a - (a) "j -o a ' 1 a - 4C

20 a •a cf a." •o nb •a •o 300 500 7C0 900 300 500 700 900 Proton Momentum (MeV/c) •a Proton Momentum (MeV/c)

1 1 1 —' : 1 i 0 0 B L- P,P—WPPTT 647 MeV |_ P>P-—»[ pir° 800 MeV / 08 26" < 9, < 32" , /• I2°< 20* / ,' — L 29" £ 92 < 35" I8°5 04 - 04 P2 - ^ . -

| o •11 1 7/

•a a"

•a 500 700 900 500 700 900 I 100 Proton Momentum (MeV/c) Proton Momentum (MeV/c)

FIGI RE l(a)-(d). Illustrations, labeled hv energy and nominal central angle pair, of 4 of (he 14 angle pairs studies in the reaction p\p ~— ppn". In each case the asymmetry is plotted in the upper graph; the unpolarized fifth-order differential cross section, in the lower. Both upper and lower graphs are plotted as functions of the first proton's momentum. Solid dots are the experimentall values, shown with their statistical error bars. Where error bars are abicnt the statistical error is smaller than the size of the dot on the scale indL-ted. Dotted lines represent the theoretical predictions of Dubach et al.: the solid lines, the revised theory incorporating corrections received in the spring of 1984. 74 PROGRESS AT LAMPF—1984

no improvement is observed in the quality of the fits References to measured data. It is now clear tnat this theoretical 1. A. I). Hancock et al.. Physical Review C 27, 2742 model generally underestimates the unpolari/ed (I4X.1). cross section by as much as a factor of 2 (see sample plots). More theoretical work is certainly required. 2. P. V. Pancella. "A Study of Spin Dependence in the Reaction /> • />/m" at Beam Energies of 500. 647. and The calcination of the polarization and cross sec- 800 MeV." MA. thesis. Rice University (April tions averaged oxer phase space for the reaction/;/; • 1484). im'n at the three energies is now under way. .V J. Duhach et al.. Physics Letters 106B, 24 ,148 I).

Measurements of (n' ,r\) Reactions on Nuclear The (rc'.n,) reactions also could be viewed as Targets to Study the Production and coherent production of v\ mesons. A study of the Interaction of T| Mesons with Nuclei coherent reproduction mechanism might shed some additional light on the problem ol coherent K produc- Experiment 852 — P3 tion. The threshold of the (Tt'.r)) reactions can be Los Alamos, L'niv. of Virginia significantly lowered on nuclear targets. It would be Spokesman;./.-( ' Pern; 11., is lhwit>si interesting to map the energy dependence of the (H'.n,) reactions, particularly below the free produc- Participants:.!. E. Simmons. .V. Stan../'. Kapiistinskv. I). II Fdztn-niltl. 7". K. Li.J.-i: Paw. II. M'. Baa:.I. IX tion threshold. Bowman. 7". -1. Cam: P. I. \I. tinini, M. .1. l.atch. .1. .\1. Another important feature of the (Tr.r|) reactions is Mo\.s. and R. R. \i luincv that information about the n-nuclcus interaction could be extracted. The n,-nucleus distortion in the Our knowledge of pion-nuclcus interactions has cxil channel should atTect the shape and magnitude of been greatly advanced by the existence of meson the differential cross sections, and a quantitative factories such as LAMPF. In contrast, the n, meson, analysis should lead to useful information about tne which is the ^ther nonstrange pseudoscalar meson interaction. classified in the same SU(3) octet as pions. has re- An initial experiment* to measure the (K.r\) i .-ac- ceived little attention up lo now. Very little information was performed at the P'-Wcs' channel during tion exists on either the n,-nuclcon or the n-nucleus September 27-24. 1484. The purpose of this short run interaction. In Exp. 852 we propose to measure the was to measure pion flux al relatively high momen- (Tt.r|) reaction on nuclear targets in order to studv the tum (~700 MeV/c) at the P' channel and to observe production and interaction of n with nuclei.' the (jt.n,) reactions for the first time at LAMPF. The The (7t-.r|) reactions could be viewed as charge- experimental setup is shown schematically in Fig. i. exchange reactions similar to the •'rc~.7r") reactions. The SI scintillator is placed in ihe beam to count the Indeed, from the similarity between TC" and n, it is incident pions and to provide a start signal for the plausible that the (ic* nj reaction could bear some neutron time of flight. Four sets of bismuth similarities to ihe (TC'.JT") reactions. However, unlil-~ germanate (BGO) counters, each a 7.6- by 15.2-cm ir:".n"). the (7t'.q) reactions involve two particles cylinder, are placed at 50 and 70" with respect to the belonging to different isospin multiplets (the isospins beam direction to measure the coincident gamma ofnand n, are 1 and 0. respectively). In addition, the rays emitted in the n. - 2y decay. Four sets of large mass difference between K and i"| implies a scintillation counters placed 4 m from the target relatively lar.;e momentum transfer (—250 MeV/c). even at small reactu n angles. It would be interesting to compare (rc*.n) measurements with the extensive *P;iriicipanls were .1 F. Simmons. N. Stem. .1. Kapustinsky. D. (7r*.7t") data already obtained at LAMPF. H. Fii/gcrald. T. K. Li. JIKI J. C. Peng. RESEARCH—Nuclear and Particle Physics 75

FK.I m 1. Schematic of the experimental setup for the test run of F\p. 852. detect neutrons from the a - p • n + r\ reaction. Figure 2 shows the neutron timc-of-flight spectrum The largel is surrounded bv si\ scintillation counters obtained with 705-McV/c it beam on hydrogen vetoing events accompanied by charged-particle (CH-C'I. Four peaks are clearly visible in the spec- emission. trum. The peak at the shortest flight time is due to From the difference between the ( H- and carbon gamma Hashes, which are attributed mainly to it" target measurements, the it + p - - r\ -+- n reaction was produced in the p{n .it");; reaction. The peak next to measured at 705-MeV/c it incident momentum. In the gamma flash corresponds lo neutrons coming addition, inclusive r|-meson production also was ob- from the p(n .n)Ku reaction Finally, ihe two remain- served for it" on a i:C target at both 7Q5 and 670 ing peaks are identified, from the flight '.imc. as MeV/c, the latter momentum being below the free neutrons emitied in the K + p - •; + r| reaction. threshold. These two peaks correspond to neutrons produced, With 0.5-mA proton current and a 1% momentum respectively, at forward and backward angles in the acceptance in lhe P' channc1. the it flux on SI is ccntcr-ci'-inass system. Preliminary results obtained measured to be 0.5 X KV/s and 3 X 105/s. respec- for the cross section of the p(n .\\)n reaction arc tively, at 7!)? and 670 MeV/c. This is in reasonable 88 ub/sr [0, ,,,(ii) = 144"] and 86 ub/sr [0, M,(r|) = 25°]. agreement with the extrapolation from previous This is in good agreement with previous measure- measurements.* ments at similar it beam energy.

*lnt(inn:iliiin from 1). H. Ku/wnikl. Los Aiumos. I 76 PROGRESS AT LAMPF—1984

~~705-MeV/c n on p (CH2-C)~~

~~1000- . p(rr,n°)n 900- -2V 600 •;~~

~~700^ *-p(n\n)n° 600 -i~~

~~K 500: z p(n ,n)n O 400- O 300:~~

~~200 -i~~

~~100 J Jllllll Illllnllliilu 0 inWJ -100 150 200 250 300 350 400 TDC CHANNEL~~

~~FIGURE 2. Neutron time-of-flight spectrum.~~

Evidence of TJ production also has been observed The n production on carbon targets with 705- ai.J with the *V ':•) counter* The T) —* 2y decays are 670-MeV/c 7t~ beam also has been observed with the character id oy a coincidence of two energetic BGO counters. Preliminary results indicate that at I2 ;;i?'nis rays (EtM > 600 MeV) hitting the left arm 705 MeV/c the ^-production rate on a C target is a vL';,xi2) and the right arm (B3,B4) of the BGO detect- factor of 3 lower than that on a hydrogen target. If this ing system. Invariant mass can be constructed, for result is confirmed by further analysis and experi- each of the 'i '.e'l-ri'ht pairs of BGO counters. ments, it could imply a rather strong absorption of Figure 3 sho . -!; ;n\auant mass plots for 705- the T] meson in a nucleus. This is somewhat surpris- MeV/c 7u~ on a v- ri: target. The presence of r) mesons ing, as the n-nuc!eon coupling constant was is clearly observed in these plots, with the exception predicted2 to be much weaker than the K-nucleon of the plot for detectors B2.B3, which subtend too coupling constant. Another preliminary result ob- small an opening angle (the minimal opening angle tained in this experiment is that the reproduction rate for 100-MeV n is -115°. whereas B2,B3 subtend on I:C at 670 MeV/c (subthreshold) is only a factor of ~100°). With this relatively simple gamma-ray de- 2 lower than that at 705 MeV/c. tector system, a total of ~500 r| events have been For future measurements on Exp. 852 we will use identified with — 7 h of n~ beam the LAMPF n° spectrometer to improve on the solid- RESEARCH—Nuclear and Particle Physics 11

~~705-MeV/cn on CH2~~

~~100-~~

~~90-~~

~~70-~~

~~BC-~~

~~8 40~~

~~0 100 200 300 400 SOO «00 U14 (UEV)~~

~~100~~

~~BC eo-~~

~~7C 70-~~

~~ac 60 sc ao o u 40 8 40~~

~~X 30~~

~~0 1300 400 SCO 300 4 00 500 800 M23 (MEV) U24 (UEV)~~

~~ci'RK 3. Invariant mass plots for the four left-right pairs of the bismuth germanate (BGO) counters.~~

angle acceptance and energy resolulion. In addition, Crystal Box Experiments the Large-Aperture Spectrometer (LAS) will be used • Experiments 400/445,726, and 888 — SMC to measure the triton recoil IP he 'He(7r: ,r|)/ reaction. Los Alamos and Temple Univ. Spukcsmcn: References li.xps. 400/445 — C \ M. Hoffman I Los Alamos) F.xp. •'Jft — I'. /.. Highland (Temple L'nivjand 1. J. C. Peng et al.. Los Alamos National Laboratory (j. /-.'. Hogan I Los Alamos) report LA-9923-MS (1983). li.xp. ,S'(S',S' — I. Ilallun! os Alamos) 2. H. Pilkuhn. The Interaction ol Iladmns (North- Holland. Elsevier Science Publishing Co.. New York. Extensive discussions of these experiments have 1967). p. 220. appeared in the past several Progress Reports. The 78 PROGRESS AT LAMFF—1984

~~^ DRIFT tPV CHAMBER~~

~~NsKTl) CRYSTALS~~

~~HODOSCOPE COUNTERS~~

~~FIGIRK 1. The Crystal Box detector.~~

aim of these experiments is to search for several rare- either the drift chambei or the plastic scintillation decay modes of the muon and the pion and to study counters. these decay modes should they be observed. In Data for all three decay modes are acquired simul- Exps. 400/445. the muon-number-nonccrserving taneously. The major source of backgrounds are the decays u.' — (••(••(• , u' - * e'y. and p.' •— r'yy are random coincidence of e"s and y's from the uncor- being sought with a sensitivity to branching ratios of related decays of several muons. This background is about 10"'1 relative to ordinary rnuon decay. Experi- eliminated by requiring that the detected particles be ment 726 will search for the charge-conjugation- in time coincidence and satisfy the conservation of violating decay n" — 3y with a sensitivity to a energy and momentum. For the u+ — cW~ mode, branching ratio as small as 10'" relative to ordinary TI" there is the additional constraint that the three tracks decay. Experiment 888 is a study of radiative pion musi emerge from a common vertex. To reject the decay 7t+ --e+v,:,'. backgrounds to an adequate level, excellent resolutions in timing, energy, and position are required. A complex software system is required to keep Experiments 400/445 pace with the incoming data. Parallel LSI-11/23 A schematic of the Cr\ stal Box is shown in Fig. 1. preprocessors reduce timing and pulse-height infor- The detector consists of a modular array of 396- mation from the Crystal Box while drift-chamber Nal(Tl) crystals that surround an array of plastic data, sealers, and analog-to-digilal and lime-to-digital scintillation counters and a high-resolution, narrow- converters (ADC's and TDC's* are being read from stereo-angle drift chamber. Approximately 5 X CAMAC". The main (PDP-11/44) compu r as- IO5n7s are stepped in a thin polystyrene target sembles a complete physical event, performs taping located in the center of the detector. Electron and cuis. and sends the data lo auxiliary tasks, which plot positron trajectories are measured in the drift the event and analyse it in greater detail. The main chamber; their arrival times are measured in the computer also performs the vital function of auto- plastic scintillation counters. The energies of elec- matic scheduling of calibration routines to track gain trons, positrons, and photons are measured in the and pedestal shifts in the Nal(Tl). This, in addition to Nal(Tl); the photon-con version points also are de- checks made on incoming data, ensures that any termined in the Nal(Tl). Photons do not register in malfunction is quickly noticed. RESEARCH—Nuclear and Part/ciW Physics

~~0 40 60 80 100 120 40 60 80 100 IE (MeV) SE(MeV)~~

FlCl KK 2. (a) The vector sum of the momenta for the two positrons and the electron ( \Lp |) vs the sum of their energies (!£) for data events. The sloping line represents the condition Y.E + \2$ \ = M,,. The area enclosed near L£ = 100 MeV, \1$ \ = 0, contains 90% of Monte Carlo u.' ' e'e'e events. r + (b) The distribution of Monte Carlo u — e e*e~\\vv events. The number of Monte Carlo events is not normalised to the number of data events.

The final test run for this experiment took place in requirement on the total detected energy was im- January 1984. For this run, each Nal(Tl) and scin- posed. This enhanced the number of events from the + tillator channel was timed and calibrated, all trigger muon-number-conserving process u —• cW~v(,vM and read-out systems were debugged and ihe data- that triggered the detector. Eleven such events were acquisition software system was thoroughly tested. observed in agreement with the Monte Carlo pro- Everything worked so well that roughly 2 weeks were gram prediction of 12 ± 2 events. A plot of the vector spent accumulating, data at an average muon- sum of thejnomenta for the two positrons and the stopping rate of 3 X 105/s. A total of 2.2X10" electron (|Zp |) vs the sum of their energies (I.E) for muons were stopped for this data set. In addition, a all of the data events and fcr Monte Carlo \i+ —+ + + full calibration run was taken with it stopping in a e c e~v,SJv events is shown in Fig. 2. The sloping line liquid-hydrogen target that was inserted instead of represents the condition IE + \Lp | = A/,,. The the drift chamber. We have analyzed these data and enclosed area in '.he plot of the data events near LH = extracted upper limits for all three processes. 100 MeV, \tp j = 0, indicates whe:e 90% of the true + The results of the analysis of the u+ —• eW data u —• e*e e~ events should lie. have already been published.1 No evidence for this The analysis of the u+ — e+y and u+ - e+yy data decay has been observed, and an upper limit from this run is nearly complete and preliminary results have been presented.21 There were 4.3 X 105 + u+ _ c yy triggers. Cuts requiring that the three- ) detected particles he in. time to within 4.5 ns and be < 1.3X 10 "(90% C.L.) *) coplanar and that the opening angle between the two photons be greater than 75° reduced the sample to has been obtained. This is the best published limit for 3050 events. The latter cut removes only 1.3% of real this process. Fcr roughly 10% of these data, no trigger u+ — <>+yy events but is needed to eliminate triggers 80 PROGRESS AT LAMPF— 1984

~~100 i i b - 1 - IE 0>) 80 0) - LJJ - n 10 — *_ 60 -(, o i M o <5 40 _ i n - E E n n = 20 in1 u|l~~

0 / 0 i 20 40 60 1 if20 f 40 60 Q Q Fu.i.Kh 3. The total probability distributions for (a) Monte Carlo-generated \i • r/y events and (b) data events. The abscissa is designated by (2, a measure of the probability, where Q = —10 log10 ( P/Pr ), !' is the total probability assigned to the event, and P,. is the total probability assigned to the most probable Monte Carle event. The most probable events are to the left in eiuh distribution.

in which a single pholon appears to be iwo closely is currently being improved to include the max- located "clumps." imum-likelihood method, which siould result in a The probability lhat each of the? e surviving events somewhat more stringent limit. ;

is consistent with Ihe kinematics of a decay into three For the search for u.' - • c'y, tlut backgrounds are bodies is then analyzed. The probability is evaluated random coincidences and the muon-number-con-

with four variables: serving process u' • <''yv,.vM (inner bremsstrahlung). 1. the time spread of the three particles. There were 12.9 X I(T triggers. Cut:; requiring A',, and 2. their to al energy. /•.', > 35 MeV with opening angles >!40" resulted in 3. the co' me of the angle between the normal to 28 350 events. The time of the positron minus the ihe plane determined by two of the three par- lime of the pholon is shown in Fig. 4. The peak at ticle moncntum vectors and the momentum /, — /., = 0 is due to inner bremsstrt hlung. The max- vector for the third particle, and imum-iikelihood analysis was perfo-med on the data 4. the vector sum of the particle momenta in thai after cuts requiring plane. The probability distributions for Monte Carlo- generated events and for the data are shov.n in | / - / | < 2 ns . Fig. 3(a) and 3(b). respectively. It should be noted thai only 376 data events are plotted in ihis fig- /•:, > 47.5 MeV . ure—all the other cents have been assigned a zero probability. A final cut on the total probability H > 16 fr . eliminated all of the data events and retained about 60% of the total acceptance. I'sing ihe final acceptance of 4.4%. the 40% confidence level upper limit is and energy deposited in the NaKTU by the positron >44 MeV. The number O!\M cuts p:..v,ing these cuts is flu' • e'YY) 192. We observe Id + S inner bremsstrahlung events, c'v v. whereas we expect 10 ± I event. The 90% confidence level upper limit for u' • c'y is 2.6 X 10 |f. A long data-taking run took place in the summer of This result is a factor of 22 better than the existing 1984. Several problems uncovered during the Janu- upper limit for this decay. The analysis of these data ary 1984 lest run were corrected in the data run. The RESEARCH—Nuclear and Particle Physics

~~800~~

~~FK;I KK 4. Relalhe positron-photon timing. The prompt timing peak is due to muon inner hrems- struhlung.~~

~~-5.0 -2.5 0 2.5 5.0~~

~~te- ty (n«0~~

most important of these wa-. the installation of a e\pcnment arc under construction. No major modi- system to detect pilcup in the Nal(Tl) detectors. This fications to the electronics oi software are needed. system should greatly reduce backgrounds tor the u • r'y and the u • c'yy measurements and allow us Experiment 888 to run with a higher muon-stopping rale (5 X 107s). Other improvements include better control and mon- A proposal has been submitted to study the decay itoringofgain drifts and hardware thresholds, on-line it' • cv,Y with the Crystal Box. We also intend to taping cuts that reduced the number of tapes written, run this experiment in the summer of I9S5. The and improved running efficiency. During this run a experiment w ill require no changes to the detector or total of I X 10'-' muor.s were slopped, which should software. The physics goal is to study the slrong- allow us to search for branching ""altos as small as a mleraclion contributions to the pion structure as few umes !(i ' for each of the decay modes. The measured by the vector and axial-vector form factors producCn analysis of these data is presently under in this decay. The vector form factor can le de- \va\. termined by assuming the conserved-vector-currcnt (CVC) hypothesis. The remaining quantity of interest is usually denoted y, the ratio of the axial-vector 85. Test data were taken while the liquid-hydrogen ment SS8 will be able to resolve this ambiguity and to target was in place to study the trigger rale: we found provide a precision measurement of y. In a modest that the trigger rate was somewhat higher than we run o! 400 h we will acquire *25OO events. (The want. The tesi data were analy/ed to determine wha1. present result is based on two experiments with additional trigger requirements would be needed to several hundred events each.) Figures shows the achie\e an appropriate trigger rate F.lecironio '•> expected number of delected ev ents \ s y. Tht result- require a minimum of two NaKTi) rows and two ing accuracy in the determination ofy will be ±0.027 columns beiw'jcn crystals struck by photons is being An independent method of determining y is to built. This cut w ill result in an appropriate trigger rale study the distribution of events in the Dalit/ plot (the and a negligible loss of acceptance for K" • ly events. siuipe i'i ihc Dalit/ plot distribution depends on y). Modulations to the hydrogen target and addi- Figure 6 shows how the //' between a data run (aciu- tional scintillation counters that are needed tor this ally obtained with the Mo:ite ( arlo program) and the 82 PROGRESS ATLAMPF—1984

~~FiGi'RE 5. The number of events in the final Dalitz plot as a function of y after 500 h of running with 2X lOV/s.~~

~~' i • i • ii • i DO i ' l 1 i ! (a) - (b) CM O \~~

X / i 65 6 / 72 ) -\ ; / 1 ; n r- Q II 4 C Q f / cvj 64 c X 2 ^ y X :—^ \J- v 0 • i i 63 l , ^ i , -4 -3 -2 0.35 0.37 0.39 0.41 0.43 0.45 X r FiGfRF 6. The overlap f; between normalized data and theoretical Dalitz plots as a function of the y used to generate the theoretical plot. The data were generated with y = 0.4. Part (b) is the same as part (a) but expanded about the minimum.

theoretical Dalitz plot distributions varies as a func- References tion of y, where the data were generated with 1. R. D. Bolton . ai.. Physical Review Letters 53, 14)5 y = 0.40. The accuracy of the determination of y by (1984). this method is ±0.035. Although this is slightly less accurate than the couni rate measurement, it is inde- 2. P. Heusi rt al., "A Search for u -••<• cy," presented at pendent of the systematic error associated with the the meeting of the Division of Particles and Fields, American Physical Society meetings. Santa Fe. New use of the absolute acceptance. Also note from Figs. 5 Mexico. October 3 ! -November 3. 1984. and 6 that the ambiguity is completely resolved. 3. D. Grosnick et al.. "A New Search for the Rare Decay u - ryy." presented at the meeting of the Division of Particles and Fields. American Physical Society meetings. Santa Fe. New Mexico. October 31- Novembcr 3. 1484. RESEARCH—Nuclear and Particle Physics 83

Muon Capture in 3He so that a 10% measurement of the asymmetry will give /•',, to better than 30%. • Experiment 529 — SMC The setup of the experiment is shown in Fig. 1. A Columbia Univ., Boston L'niv. 28-MeV/c short backward-decay beam comes in Spokespersons: (i. Dugan and('. .S'. II // (Columbia I'mv.) along the y axis, and there is an — 100-G field in the z direction to precess the muonic atoms. The chamber Participants: D. Aide. 1.. Delker. 11. llarada. B. Roberts. J. 3 Miller. E. Austin. /•'. O'Brien, and If. van Riper gas is 400 fi of He quenched with 1.5% CO, for chamber operation. The muon stop is defined by a Two experimenta were performed previously1 to thin scintillator SI and the upstream/downstream measure the rate of the reaction wire chambers Cl and C2 by forming the coincidence SI -Cl • C2. Tracks of the -"eaction products are (H . (1) measured by the drift-chamber systems DC 1 and DC2. Tritons from Eq. (1) trigger coincidences in The object of our experiment is tu inc. uie the DC'i or DC2. They have a range of about 20 cm and pseudoscalar form factor (/•'., at t/; — "»;„) of the remain in the target box. Most muons do not trigger weak hadronic current in Eq. (1). A measurement of the drift chambers: the other reactions that trigger the the rate gives information about the axial form factor drift chambers are the break-up channels (/•'.,). but this quantity is insensitive to /•",,. Hence /•',, is known to only about i00% accuracy in 'He. The u + 'He — v + n + d . (2) experiment observes the angular correlation between the spin of the li>'(u"He)* atom and the recoil triton u + 'He — v + n + n + p . (3) momentum. This quantity is a combination of four form factors: /•",, /•',„, /•',,, and /•',,. Under the assump- and the thermal neutron capture tions of conserved-vector current (CVC) and partially conserved axial current (PCAC). the asym- /; + 'He — p + 'H . (4) metry a. is related to the residual muon polarization In addition, there is background from a emission following muon capture in the i:C and "'O nuclei of a, = 0.502 Pu . CO,:

~~ji + |:C — "C* -•• n (or p or i/or a) + nucleus : The asymmetry is rather sensitive to /-', i: r A/-',. _ ^ ±a. u -r O ••-• O* • n (or /> or c/or a) + nucleus . (5)~~

~~SEAM. FK;I"~~

~~MWPC o~~

~~se 84 PROGRESS AT LAMPF—1984~~

Electrons from regular muon decays leave the target With the triton data, the drift-chamber informa- box and are delected in a six-plane mulliwire proportion is needed to separate the iriton events from other tional counter (MYVPC) and sciniillator.S", only. They heavily ionizing tracks of Eqs. (2)-(5). This is ac- arc invisible to the drift-chamber systems. complished by measuring the dE/dx in eight planes Data were taken in the SMC south cave between and also by looking at the track range. Thus each August and November of 19S2. About 700 h of beam drift-chamber system is composed of thinner planes time were available. The muon slop rate was 4.5 kHz for dE/ilx measurement and thicker planes for the (75 kHz instantaneous). Discounting the early debug- range. Achieving this proved to be more difficult than ging runs, about 45 X 10" electron triggers and II X expected. However, we could see two peaks in the 10" triton triggers were obtained. mass spectrum, understood to be the signal trilons Data were divided into electron events and triton and alphas from Hq. (5). mostly resulting from the events and analyzed separately. Only preliminary oxygen reaction. results are available at this time. Triton tracks were measured at eight points along Electron tracks were fitted lu a straight line: infor- the track, four points each in y and z views. They mation about where along this track the event or- were filled to solve for /,, and the left/right ambiguity iginated is not available. A cut was applied to as well as the usual straight-line track parameters. eliminate e\ ems that reconstruct to the vicinity of the The /„ is subtracted from the time of event, measured G-IO frame of the drift chambers, and the time of from the muon stop and histogrammed. A fit to this electron event with respect to the muon stop was time spectrum results in a muon lifetime slightly histogrammed. Because of the precession field, the longer than 2.2 us. indicating that there is significant spatial asymmetry of the electron with respect to the error in the /,, calculation. However, one of the mass muon spin appears as an oscillation in the time peaks shows a systematically shorter lifetime, in- c pec t rum folded into exponential decay. This spec- dicating the presence of oxygen-reaction products. trum is filled to the fundion These events are 20% of the data. A more detailed analysis, using a more sophisticated irack-fiuing pro- = \,rc ' • [I + a, -cos (co/ + ip)] + C (6) cedure, is under way to confirm this result with the correct lifetime. A third class of particles. 50% of the For electrons, the asymmetry parameter a, is related non-pile-up events, is seen as a Hat background in the time spectrum. These particles are also observed in to the polarization Pu as the u" data and come from thermal neutron captures.

References With the electron sample of 1.2 X 10'' events, the 1. L. B. Auerbach el al.. Physical Review 138. BI27 asymmetry was 0.74 ± 0.21%. which is in good (1965). agreement with the previously measured value of 2. D. R.ClayetaL Physical Review 140, H586(l%5). 0.77 ± 0.34%. This old value is from a run of 1980 3. W.-V. P. Hwang. Physical Review C \7. 1799(1978). that looked for only the residual polarization. After correcting for geometric acceptance and field in- homogeneity and assuming a 40% initial beam polarization, this asymmetry corresponds to a residual polarization of 3.4 ± 1.5%. The error on the An Improved Search for p — ey present value can be improved bv including the U. I). Cooper ami (i. I', lloium I I,o\ llamo-i and M. II". events alTcc'cd by pileup. which comprise about Ruler (Si'iinlord I nivj three-fourths of the data. Because a complete history of events was kep! for up to four muons before the The search for muon llavor-violaling processes event and two muons alter, a good fraction of these such as u - <7 has been substantially more successful events could be corrected for and added to the non- during the past decade because the recent generation pi I e-up sample. of experiments offers new limits that arc three orders RESEARCH—Nuclear and Particle Physics 85 of magnitude beiiei ihan the older ones. The lack of a I \m 1 I. Parameters of the Apparatus Cor a u • ey good reason for union number conservation in mod- F.\periment. ern gauge theories moii\ates these efforts. The dis- covers ot such a reaction would herald a new type of Fractional solid angle 0.55 Detection efficiency 0.20 interaction, its nondiscovery. even with increasingly Stopping rate (average) 3 X 10 s belter limits, restricts the types of models we can Live time 1.2X10's build to explain other phenomena. Fractional positron energy resolution 0.005 The reasons for undertaking ihi. experiment are Positron position resolution 2 mm even more relevant now. Violations of the standard Positron angular resolution 0.7° vveak-interac'ion model of Weinberg and Sulam may Fractional photon energy resolution 0.02 be showing up at the CERN collider, and such events Photon position resolution 2 mm ma> indicate a rich physics beyond our current Photon angular resolution •)" Time resolution 0.5 ns knowledge. As a consequence, we ave trying to design F.ffk'ieney of internal bremsstrahlung veto 0.9 a rare-muon-e'ecay experiment that pushes the sensi- li\ uy for the reaction u • ir> to 7 X 10 4 (40% C '•..). There is no delinite proposal as >et as lo how to reach in the detectors will he handled by high multiplku-.. this goal, hut a proof oi principle is almost in hand. For example, the chambers will have I-mm wire The search for u - 17 is made by identifying spacing and there will be at least 200 scintillators. kinematically correct events—that is. in-time, back- Electrons trapped in the field for more than eiglv lo-back electrons and gamma rays of 52.8 MeY each. loops will be rejected. The chambers will be g:ued The signal must stand out from any background. To with a short coincidence pulse to limit their sensitiv- reach the desned sensitivity. the decay must be found ity to short periods of interest and the magnetic field in the midst of 3 x It)'1 normal muon decays. We will be strong enough to contain all electrons within a plan to achieve '.his number ol useful decays by 2.S-cm circle. slopping 3 v 10 surface muons/s (average) for 10 s Around ihe electron spectrometer will be the (live time) with a solid angle of 55% and a detection photon detector. Basically, the photon detector is a efficiency of 20%. The instantaneous decay rate thus series of pair spectrometers, each spectrometer con- aehiev ed w ill produce a decay decinr every 2 ns and taining layers o\' scintillators. lead converters, and will tax oiii detectors to their limits. wire chambers. Monte Carlo simulation shows that To isolate u - cy candidates from background 2% energy resolution is possible, but to achieve this events we must have good icsponses from the de- resolution approximately 1000 scintillator- tector elements. Table 1 lists the critical parameters o( phc.tomultiplier channels are required. The exact the apparatus. .Vhen equipment with these type of multivvire chambers needed is still under properties is used, less than one background event study. can masquerade as u • 17 during the live lime of the The most serious background for the experiment experiment. comes from a random, back-to-back coincidence be- The equipment is to be contained in a large, uni- tween two muon decays by the processes u • cvv (52- form magnetic Held of roughly 15 kCi. The MeV positron) and u - r/vv (52-MeV photon). We dimensions o! the solenoid are 2 m in diameter by intend 10 suppress this background by detecting the 2 m in length. Several existing magnets have been low-energy electron accompanying the photon and identified that might be refurbished for the experi- vetoing the event. This should be possible with 90% ment. ! he central region will contain the target, efficiency by using a set of scintillators near the end which vsill he canted ai a large angle so that it is thick caps of the solenoid where the beam enters and exits. in the beam direction hut thin in the direction of The trigger must serve two purposes: (1) it must accepted dec r. s. slow the data-encodinn vale sufficiently to prevent The target will be surrounded by a positron spec- dead time and (2) it must reduce the total taping trometer consisting of three planes of multivvire speed to a reasonable level. We plan a trigger with proportional chambers with seintillators at the up- both staged and parallel elements. The raw trigger stream and downstream ends. The tremendous rate will be a >42-MeV y in 'he pair spectrometer, which 86 PROGRESS AT LAMPF—1984

will reduce the rate to I event/50 us. Fast-encoding Much work remains to be done to bring this and analog-to-digital and lime-io-digital converters protodesign to the proposal stage, but we are op- (ADC's and TDCs) can handle such rates. Next the timistic that the problems will be worked out and that data will be read into roughly 20 multiplexed and the proposal can be submitted to the Program Ad- arbitrated microprocessors that will contain all the visory Committee (PAC) meeting during the summer events from a LAMPF macropulse and will have an of 1985. This experiment would improve the limit for 8-ms interbeam period for further processing. In that u -—• (7 by a factor of 500 over the Crystal Box results. period the pattern recognition can be done on the Such an improvement would allow us to explore the electron arm to produce energy and direction cuts on mass for new particles in the multiple tera-electron- the event. Gaining a factor of at least 100 at this stage, volt range. The experiment would be both a major we can tape at a rate of less than 20 events/s. scientific advance and a technological feat for LAMPF. RESEARCH—Atomic and Molecular Physics 87

Atomic and Molecular Physics the 11 beam upstream of the primary interaction region. The H inns were converted to H" atoms in the first collision. Thus, by liming the first beam Atomic Physics Using the 800-MeV H Beam carefully with respect to the ultraviolet beam, the behav lor of an H'! beam could be probed (as for H~) Los Alamos, L'nh: of Sew Mexico, I niv. ofConnecticut in the interaction region with the ultraviolet line. A Study of the Effects of Very Strong Electric I'sing pulsed Helmholtz coils developed by K.. B. Reids on the Structure of the H Ion Butterlleld and (i. .1. Rrausse. we have observed FT • Experiment 586 — EPB resonances in fields as large as 2.6 MV/cm. Figure 1 displays data that were taken to try to answer the : Spi'l\C\IIH'li. II t '. Hl'WH! 11 /I/I c' A I'll \t{'\li t l Jllll question. "Does the shape resonance decrease in I' I M (ir.ii)i iLo\ \Li»h> ' width as the electric field increases for the first 200 to Fundamental Experiments with Relativistic 300 kV.'em'.'" Figure 1 also shows the cross section Hydrogen Atoms: Exploratory Work for photodeuichment in the // = 2 resonance region • Experiment 587 — EPB tor zero field and an electric field of 120 kV/cm. The shape resonance is affected very little, although vis- S/>< A i\i >wn II M SM;/:M ' >;. i •>!' i"/*/,1,::, '// jnii ually it appears that the shape resonance has indeed narrowed. A definitive answer awaits a detailed In the past year our group completed iwo lengths sumstical analysis oi these and similar data taken in experiments. ?Nt> and 58". using the r.PB facility at the same experimental run. The shape resonance was LAMPF. Another approved experiment. 588. is pres- extremely resistant to electric field quenching and ently under way and preliminary data will be ob- was robust in this respect, to a degree comparable to tained in the summer of 1L)85. that of the ground state. As has been well documented, the experimental A high-field study also was completed on the auto- method used at LAMPF' for atomic phvsics is a high- detaehinn Feshbach resonances observed in H hc?r resolution, laser-induce 1. photodetachment technique developed b> Bryant el al. The crossing of an ultraviolet photon beam with the reiatmstic 800- MeV H allows the uiergy of the photon (in the H ion's center of mass) to be tunable o* er a large Kinge c by varying the angle of intersection. 13

Experiment 586 n .2. In this experiment the -UOL)-cY photon beam o from the fourth harmonic of a neod\mium:\tiiium- o 0) alummum-garnet (Nd:VAd) laser permitted the m energv of the photons to be tuned from 1.4 to 1 5.1) eV. in o To stud> the physics of the ion in an electric Held, a o magnetic held was applied to the interaction region. Because of ihe relatmsue nature of the II beam. e\en modest H fields were translbrmed into mega- o s \olt-per-cen'iimeler !'. fields in the rest frame of the o5 "a panicles. With this method, electric field strengths o o were reached that could not be attainc in the labora- XT tory frame, and the H field fell by the ion remained insignificant. Photon Energy The apparatus also was modified so that we could study ri in strong motional electric fields by passing 1'u.i RK 1. The Feshbach and shape resonances the fundamental frequency of the Y ACi laser through with and without an electric field applied. PROGRESS AT LAMPF— 1984

~~c o~~

~~in O uT Fu.i RK 2. The photodetaeinnent iross sec- 0 £ D tion just above the n = 2 threshold show iny c the Luc-KoeniK oscillations. 1 " Si « 2. O O CL~~

Photon hnergy I he- 'i = .i threshold. Data were obiawied lha! showed the complete quenching ol ihe I'esonances onh In an e\eepuonall\ hi.'h electric li.-ld Such behavior is in the oscillations with the field. lite data presented sinking v.onlrasi lo Ihe Fcshhaeh ivsonaim' which here constitute the highest field measurements and tlrsi spins and then quenches ai lou electric fields. consequent!^ the strongest observation of the Luc- The resistance of the l."\io()-eV resonance to Koemg oscillations in any atomic system io date. quenching has been attributed to its probable "-" The FI beam with \\ — 0.84 and a precisely known svmmctn. nature (the n = 1 Feshbach resonance has set of cnerg\ levels (the Bohr levels) were well suited "—" s\miiiein.). for a high-precision test of the Doppler formula. In fact, this measurement literally fell out of the Kxperiment 587 Feshbach calibration experiment with no additional beam time required. Our data give a test of the This e\penmenl -Aas onipleted in October lLtN4. Doppler formula to I X II) 4. The Feshbach resonance near i< ~ 1 m the H s\stem B> working at \ery high electric fields and low has been a con\enient delta function for calibrating quantum numbers we could slud\ 'he individual the resolution and energ\ scale ot our II resonance resonances near the lop of the effective Stark- work. Flowe\er. in the past we relied on theoretical ( oulomb potential without background from other predictions for the energ\ of ihe Feshbach resonance, sunk channels. I he most striking observation was cw n though these predictions disagree with one an- that over much of the high-lield regime studied, the other b;> sc\eral-mil!i-clectro". Milts. In this experi- resonance shapes depart significantly from the ideal ment the Feshbach resonance was calibrated againsi i.orent/ form. the L\man lines in neutral hvdrogen. The Feshhach energ) was One attempt was made last year to ohserv power broadening of the Feshbach resonance at /; == 2 (H)>)25 eV). \ cylindrical lens had been installed in /-.',,si. ~ i n.i>245 ^_ o.noo? c-v the ultraviolet scattering chamber, increasing the power densitv output of the laser bv roughlv a factor of 3. I wo runs were taken, the first with the laser set In the past we have looked lor oscillations in the at naif power and the second, at lull power. An effect continuum spectrum of atomic ludrogen in an elec- suggestive ot power broadening was seen. These data tric Held but obtained indefinite results. Fxamnles of runs will be repeated with high-power optics. the preliminar\ on-line data are reproduced m Fig. 2. The oscillations appear not onl\ abo\e the Held ionualioii threshold bul remain there until the HIIII- Re fere nee zation threshold of the unperturbed atom is reached. I. H. ('. Brvant el ai.. I'hvsnvl Review . I 27. 2S

Experimental Investigation of Notice that the cycling rate Xc, and therefore the yield Muon-Catalyzed dt Fusion of 14-MeV neutrons per muon, continues to rise at the highest temperature rer.-hed (800 K) and that X • Experiment 727 — Biomed c increases more rapidly with density than the first Idaho National Engineering Lab., Los Alamos power (the normalized XL. is shown). Both of these Spokesman: S. E. Jones (Idaho National Engineering Lab.) results are surprising and unexpected; the density dependence, especially, challenges our understand- The LAMPF muon-catalyzed dt Susion experiment ing. continues to provide some very surprising and inter- The dependence of Xc on the tritium fraction is esting results. The basic experimental methods and shown in Fig. 3. The optimum (for 14-MeV neutron earlier results are described in the 1983 LAMPF production) moves to the right as the temperature is Progress Report.' The catalysis cycle, with more (but raised. By using the different tritium-fraction de- r by no means all) of the complications than are pendence c ihe terms in the equation for Xc (see usually shown, is pictured in Fig. 1. Note that dd\x Ref. 1). the dt\.i molecular formation rates for t\i and tt\a fusion, along with scavenging by 'He, all collisions with D: and DT molecules can be ex- compete with dt\i fusion, creating complications as tracted. Some recent results are shown in Fig. 4. The well as opportunities to learn more. plateau for A.,y/M_rf below 300 K was completely unex- Measurements of the muon-cycling rate now have pected and remains a challenge for theorists.2 been extended to higher temperatures and densities The biggest surprise of all is the apparent variation than reported earlier'; the results are shown in Fig. 2. of the sticking probability with tritium density,

~~cHeAtHe HeM H» — -~~

~~Resonant muonic molecule formation~~

~~1NEL4 0488~~

FIGURE 1. Scheme of processes occurring when a negative muon (u) stops in a mixture of deuterium (rf), tritium (r), and helium (He) having respective molar fractions Cd + C, + Clle = 1. Rates (>.) and sticking probabilities {(a) ire defined in the Figure. 90 PROGRESS AT LAMPF—1984

175 1 1 1 i 1 i i i 0 0 ~ 150 - o o o 0 a 125 - 0 a a — o a A A A A 0 A A A 100 h 0 A a S • 8 0 8 0 a s 75 --. • * o o a D o A 30% Tritium (from • 36%) _ a 0 50% Tritium (from * 36%) § • 50% Tritium (from = 72%) 2 o o ° 25 mm 0 70% Tritium (from = 36%) "

~~l 1 1 1 i l 100 200 300 400 500 600 700 800 900 Temperature (K) INEL 4 0462 FIGURE 2. Temperature dependence of the muon-cycling rate normalized to liquid Hi density, as observed in Exp. 727.~~

~~1 i 1 T~~

~~c 100 K - 7~ 125 a • 300 K n 550 K ^100 • o • o - m - | »i- 8 a 0 ! • 1 a - o B 25 - O • oL i i 1 o 0.0 0.2 0.4 0.8 0.8 1.0 rritlum Concentration INEL 4 0443~~

~~FIGURE 3. Dependence of the muon-cycling rate on tritium molar fraction. RESEARCH—Atomic and Molecular Physics 91~~

~~1200~~

~~100 200 300 400 500 600 700 800 900 Tamparature (K) INEL 4 wee~~

FIGURE 4. Molecular-formation rates for D, and DT collisions. shown in Fig. 5 (see Ref. 1 for the method of de- fusion, but its drastic variation may indicate that the termining the sticking probability). This quantity is muon is getting lost somewhere else in the cycle as supposed to be the probability that the muon will well. In any case, it is clear that the actual a sticking remain bound to the recoiling a particle following dt probability is at least a factor of 3 smaller than theory

~~1.60~~

~~1.25 -~~

~~1.00 ilit y~~

~~CO Theory o 0.76 Pro l~~

~~ic k 0.60 CO a 0.26 -~~

~~0.00 0.2 04 O.0 0.8 (Tritium Concentration) X (Density)~~

~~FIGURE 5. Variation of the apparent sticking probability in the dtp. cycle with tritium density. 92 PROGRESS AT LAMPF—1984~~

~~FIGURE 6. Extracted ddfi molecular-formation rates vs temperature using HV = 0.126, as~~

~~100 200 300 400 500 600 Temperature (K)~~

predicts' (Fig. 5). Small sticking probability means because the st-cking in dd\i fusion is rather large large neutron yields, and indeed well over 100 neu- (12.6% as measured by Balin et al.4), dd\i fusion trons per muon already have been observed under shows up as an increase in sticking fraction and our experimental conditions. enables us to extract the dd\i molecular formation The molecular formation of dd\i competes with rate X,,^ (Fig. 6). d— t transfer for very low tritium fractions (Fig. 1). Finally, another contributor to the loss of muons from the cycle is scavenging by JHe. This enables us to determine the rate XrtHc for the reaction

~~1200 1 i /u + 'He t +~~

~~as a function of temperature; the results are shown in 900 - Fig. 7. These measurements agree quite well with the calculations of Aristov et al.5~~

Except for XMv for T < 400 K (Ref. 6) and Xc for [ low tritium fraction7 (<8%), all of the results dis- - 600 - cussed above have been measured for the first time in i i the present experiment. In view of the richness of the X T harvest so far, who can rioubi that more exciting discoveries await us in this fascinating area of phys- 300 - i ics?

References 1 1. "Progress at LAMPF. January-December 1983." Los 100 200 300 400 500 Alamos National Laboratory report LA-10070-PR Temperature (K) (April 1984), p. 102; and S. E. Jones et al., Physical Review Letters 51, 1757 (< 983). FIGURE 7. Temperature dependence of the muon 2. "Progress at LAMPF, January-December 1983," Los scavenging rate ^He' Alamos National Laboratory report LA-10070-PR RESEARCH—Atomic and Molecular Physics 93

(April 1984), p. 97; M. Leon, Physical Review Letters 5. Yu. A. Aristov et al., Soviet Journal of Nuclear 52,605 and E1655 (1984); and J. S. Cohen and R. L. 3, 564 (1981). Martin, Physical Review Letters 53, 738 (1984). 6 V. M. Bystritsky ct al., Soviet Physics-JETP 49, 232 3. S. S. Gershtein et al.. Soviet Physics-JETP 53, 872 (1979). (1981); and L. Bracci and G. Fiorentini. Xuclear 7. V. M. Bystritsky et al., Soviet Physics-JETP 53, 877 /« A364, 383 (1981). (1981). 4. D. V. Balin et al., Phvsics Letters 141B, 173(1984).

~~Prediction cf Ortho- and Para-Deuterium~~

Using the "canonical" binding energy value'1 of •For recent resiews ul'ihis subject, see Ret'. 6. 0.64 cV. we find the molecular formation rates shown in Fig. 2(a). The curves for the different targets are 94 PROGRESS AT LAMPF—1984

~~_ ^=^F = 3/2 / / * 0.8- //HT FIGURE 1. Predicted temperature dependences of the drfu. molecular-formation rates for each rfu~~

(10 ' ^^——• atom spin value F. Each F curve is the sum of •o transitions to total spin S = 3/2 and 1/2 of the rfrfu. U. "O iI >^ molecule (see Ref. 10). For F= 3/2 the LT and HT * 0.4- curves are marked; the solid E curve lies between them. For F= 1/2 the cirves are identical.

~~0- L—/ 100 200 300 400 Temperature (K)~~

~~0.30~~

~~w 0.20-~~

~~0.10-~~

FlGURE 2. (a) Predicted a'.'u molecular-formation rates for singlet fu. atoms colliding with D2 molecules, 200 300 400 with differing ortho/para ratios as marked. Temperature (K) (b) Muon-cycling rates, corresponding to Fig. 2(a), for concentrations CD,:CDT:Cr2 = 1:2:1. The various parameters (see Ref. 5) have been chosen to give a reasonable fit (HT curve) to the data of Ref. 11.

100 200 300 400 Temperature (K) RESEARCH—Atomic and Molecular Physics 95 strikingly different for T< 100 K. because the strong 8. D. H. Weitzel et al., Journal of Research of the low-temperature contribution is from the (K, —* Kj) 1 National Bureau of Standards 60,221 (1958). —• 3 resonance at 25 K, which is removed for LT and 9. J. S. Cohen and R. L. Martin, Physical Review enhanced for HT. Since for high-density targets like Letters, in press. those used in the Jones et al.2 experiment the molecu- 10. J. Zmeskal et al., Atomkernenergie Kernlechnik 43, lar-formation rates are not directly observable, we 193(1983). exhibit the corresponding cycling rates in Fig. 2(b).* It is clear that an experiment with a varying O/P ratio 11. S. E. Jones et al.. Physical Review Letters 53, 738 would be straightforward and very valuable. (1984).

*Scc Ret", 5 for the relation of the cycling rale to the molecular- formation rale and other rates of the problem. The various parameters used in the cycling-rate calculation, which were chosen to give a reasonable fit lo the data of Jones el al. (Ref. 11). include an overall scaling of the molecular-formation rates by a factor of 17. Most of this factor is needed to An Emitter-Coupled Logic Router for compensate for the reduction (by a factor of about 8) that is Multihit Experiments brought about by including electron shielding (see Ref. 9). We assume, even though this Born approximation calculation is Idaho National Engineering Lab., EC&G Idaho, Inc. not accurate for ihc very low collision velocities involved, that our values are correct for the relative strengths of the contribu- A. J. Caffrey, J. M, Hoggan, and L. O, Johnson (Idaho tions of various resonances (de'u rmincd by the energy balance National Engineering Lab.) equation and various rotational and vibrational matrix elements) and that the relative values of the molecular-formation Introduction rales arc therefore reliable. The fit to the dala was made with the HT curve. Note that singlel collisions with DT, rather lhan A study of muon-catalyzed fusion in high-density D;. molecules do not contribute at low temperature (Refs. 2 gas mixtures detects several 14-MeV neutrons within and 5). a 5-us time window.' The experiment required neutron pulse-height and time-of-arrival information. Rather than using custom-built analog-to-digital and time-to-digital converters (ADCs and TDCs), we References chose to design a simple logic-routing module. The 1. P. Kammel et al., Physical Letters 112B, 319 (1982), logic router transforms off-the-shelf CAMAC mod- and Physical Review A 28, 2611 (1983). ules into multihit devices. 2. S. E. Jones et al.. Physical Review Letters 51, 1757 (1983). Circuit Description 3. P. Kammel, in the Proceedings of the Third Inter- The logic router is basically a string of ZMype flip- national School of Exotic Atoms. Erice, Italy, 1984. flops. The first two stages are shown in Fig. 1. Each 4. S. I. Vinitsky et al., Zhumal Eksperimental'noi i successive input pulse changes the state of one flip- Teoretkheskoi Fiziki 74, 849 (1978) [Soviet Phys- flop and arms the next in line. A "1 shot" generates a ics— JETP 47, 444 (1978)]. 200-ns-wide pulse on the flip-flop transition. 5. M. Leon, Physical Review Letters 52, 605 (1984). The router is constructed with emitter-coupled logic (ECL) for fast operation.* Level shifters are 6. L. Bracci and G. Fiorentini, Physical Reports 86, provided at the inputs to match fast nuclear- 169 (1982): and L. I. Ponomarev, Atomkernenergie Kemtechnik 43, 175(1983). 7. A. Farkas, Orthohydrogen. Parahydrogen and *Motorola 10 000 series integrated circuits (ICs) were used in Heavv Hydrogen (Cambridge University Press, the module. 1935). 96 PROGRESS AT LAMPF—1984

~~Q FIRST IN NIM/ECL 7 0 ISHOT \ ECL/NIM L. R RESET NIM/ECL~~

~~L 0 SECOND a ISHOT ECL/NIM R~~

~~TO NEXT STAGE 1 r '~~

~~Fici'RK 1. Logic router.~~

instrument-module (NIM) logic levels. The output Operation provides 0 V for logical 0 and —1.5 V for logical 1 to The logic router is connected to the ADCs and match the gating requirement of our ADCs.* Two TDCs as shown in Fig. 2. A neutron logic signal (N1) outputs are provided for each stage. The router is within the 5-us window (designated MU in Fig. 2) packaged in a single-width NIM module. satisfies the AND gate and pulses the logic router. The router stops a TDC channel and gates open an *LeCroy Research Systems Model 2249SG separate-gate ADC channel. The delayed linear signal from the CAMAC ADCs and Model 2228A TDCs were used in our neutron detector photomultiplier is fanned out to all experiment. ADC inputs.

~~VALID~~

~~N1 OVERFLOW t. LJ IJOGIC ROUTER y y-~~

~~COM START TDC ADC UNE.AH FAN! 1 1 JUT STOP GATE 2 DELAY 2~~

~~n n~~

~~FIC;L KK 2. ADC/TDC logic. RESEARCH—Atomic and Molecular Physics 97/ / 0~~

In test mode, which is provided to simplify ADC cascaded if necessary. It should find other applica- and TDC calibration, all stages are armed and fire tions where the required data rate exceeds the speed together on the first input pulse. We often connect an of common digitizing instruments. output to RESET to eliminate the need for a reset pulse during tests. Reference

Performance 1. S. E. Jones et al., Physical Review Letters 51, 1757 (1983). The logic router produced no evident distortion of time or pulse-height spectra. The module can be RESEARCH—Materials Scfence

Materials Science The NSE technique, introduced by Mezei,5 measures the spin-correlation function Sa (q,t) directly, where q is the neutron momentum transfer. Muon Longitudinal and The muon-spin-relaxation (uSR) method yields spin- Transverse Relaxation Studies in lattice relaxation rates that are sensitive to fluctuations of the (dipolar) local field h(t) at muon sites. Systems with Random Exchange This yields a broad average over all ~q, as in nuclear • Experiment 499—- SMC magnetic resonance (NMR). The time dependence of Rice Univ., Los Alamos, Univ. of California at Riverside, the local-field correlation function Sh(q,t), averaged Univ. of Leiden in The Netherlands over all %, can be measured indirectly using uSR in a longitudinal applied field, and the result can then be Spokesmen:S. A. Dodds(Rice Univ.), R. H. Heffner(Los Alamos). andD. F. MacLaughlin (Univ. of California at compared to Sn(q,t), obtained using NSE in zero Riverside) field. The two techniques are complementary in the time domain because NSE is most sensitive to cor- 8 12 Comparison of Muon Spin Relaxation relation times in Sa(q,t) between 10~ s and 10~ s and Neutron Scattering whereas uSR is most sensitive to times between 10~4 s and 10"" s. Recently the longitudinal field dependence of the muon spin-lattice relaxation rate X.y has been re- For muons at rest in the sample one may argue on 1: 1 ported for T< Tx in the spin-glass Ag|oo-.vMnv, x = very general grounds' that X$ is proportional to the 1.6, 3, and 6 at.%. Here, Tg is the glass or freezing noise power •/,,(<<>„) in the fluctuating field at the 3 temperature. The measurements were carried out in muon Larmor frequency coM, assuming that the ap- applied fields H between 0.15 and 5 kOe (gy.BH

~~log (1)~~

FIGURE 1. Impurity spin-correlation functions !;(/) obtained from neutron-spin-echo measurements (Ref. 10) for T/Tg < 1.1 in spin-glass Cu99Mn,. The curves are fits to the functional form of Eqs. (2) and (3), with parameters as indicated. The dashed lines indicate that Eq. (2) is rigorously correct for (ta,t) s> 1. The numbers in parentheses are the reduced temperatures T/Tg.

~~1.0~~

~~CuMn(5at.%) C 0.5 _Tg« 27.5 K~~

~~0 -14 -12 -6~~

~~FIGURE 2. Correlation functions, as in Fig. 1, for Cu95Mn5 (Ref. 9). RESEARCH—Materials Science 101~~

and O/Mn were taken by Uemura and collaborators (2) at TRIUMF. Below 7;,, a(T) increases with decreasing temperature from a(lk) ~ 0 to the frozen-spin value a(0) for T <§: TH. Figure 3 gives the dependence of [a(T)/a{0)]2 on reduced temperature T/T for the where F(0) = 1 and F(~) = 0, so that .1 = S {~). R h ahnve systems. Within about 20% uncertainty the In a real spin glass an upper limit to the spectrum data scaie well. We note that for T/T = 0.7 the value of fluctuation frequencies exists. We take this upper s of[a(T)/a(0)]2 = 0.4 agrees well with the NSE value limit to be about an exchange frequency co,. =* kuTJh of .-1(777;, = 0.7) for Cu Mn, (Fig. 1), but is signifi- (MO'V for -v = 0.01 in CuMn and AgMn). The g9 cantly smaller than .1(777; = 0.7) = 0.6 for Cu, Mn uSR data imply a power-law form J,,((i>) <* co*"1, so )5 5 (Fig. 2). that Walstedt and Walker14 have shown that under some general assumptions (»•"' interaction, low im- (3) purity concentration, and rapid spin fluctuations) the linewidth a(T) of a probe spin (muon, nucleus) in a Using the form of the correlation function given by magnetic alloy is related to the impurity spin magni- Eqs. (1) and (2) and the time dependence implied by tude bv the uSR results [Eq. (3)], values of Sh(t) are obtained and compared with the measured £,(/) from NSE. am * <|r|>, (4) Least squares fits of the NSE data have been performed, using Eqs. (2) and (3), with free parameters A, to,., and v. In general, the NSE data are not precise enough to determine all of these parameters accurately, so it must be decided instead 1.0 whether a physically reasonable set of parameters is consistent with both uSR and NSE experimental results. The curves in Figs. 1 and 2 give typical fits. It can be seen that the form of Eqs. (2) and (3) represents the NSE data weli, using the estimates co,, = 10i: s ' for o Cugi)Mn, and 5 X 10" s"' for CuM5Mn5. For T < 0.7 Ts, reasonable fits are obtained with v = '/>, which is the value obtained from the uSR data,2 although the neutron data do not determine v well. One can see from Figs. 1 and 2 that at T/T,. — 0.7, for • AjMn ( 16 ot. %) example. .1(7") is —0.6 for Cu<,jMn5 and ~~0.4 for A AuFe (1.0 at %) Cu99Mn,. The NSE data, therefore, do not obey the expected scaling law, as noted previously.10 O CuMn (i.i a1 %)

Below Tx the short-time behavior cf the longitudinal muon relaxation function Gt{t) provides direct experimental information on the distribution of static muon local fields and is therefore related to T/TQ the long-time behavior of S,,(t) [that is, the value of A in Eq. (2)]. Measurements of G//) in .-IgMn (Ref. 11), .-Iz/Fe (Ref. 12), and CuMn (Ref. 13) for impurity concentrations of ~ 1 at.% have determined the FIGURE 3. Dependence of the square of the re- width a(T) of the Lorentzian distribution of static duced muon local-field distribution width |a(7*)/a(0)]2 on reduced temperature T/T in three local fields in each of these systems. The data on g metallic spin-glass systems at zero field (Refs. 11, .f.EfMn were taken at LAMPF. and the data on AuFe 12, and 13). 102 PROGRESS AT LAMPF—1984

Here < >r and < >; signify thermal and spatial parameters. This confirms the similarity between averages, respectively. Moreover, A{T), defined in muon local-field and impurity-spin stochastic Eq. (2), is given by behavior (assumed above) over a wide range of values of T. (A similar comparison has been made by (5) Uemura independently.16) We have concluded that muon-spin-rclaxation and Comparison ofa(D(nSR) and/l(r)(NSE) then yields neutron-spin-echo measurements of local-field and information on che spatial distribution of spin impurity-spin correlation functions £(/) in metallic spin glasses give consistent moults for tempera',ures magnitudes r, as first pointed out by Uemura and Yamazaki.'- This has been explicitly demon- above and below 7",,. The time-dependent compo- strated by Heffner and MacLaughlin,4 where it is nent of £(0 decays below Tg as t~\ v =* '/:. This argued that the relation A(T) — [a(T)/a(Q)f (given in behavior is consistent with recent mean-field theories 17 the data of Figs. 1, 2, and 3) shows that the impurity of spin-glass dynamics, as well as with earlier Monte 1 spins are distributed in direction but not in magni- Carlo simulations." tude below Tj,. This in turn seems consistent with a "percolation" picture of the transition at Tg, only if Spin-Glass AgMn the "infinite cluster" (the formation of which is taken New transverse-field uSR experiments on spin- to define Tx) quickly encompasses essentially all impurity spins as the temperature is lowered be-low glass ,4gMn have measured the s-d exchange energy T,- The form of £(/), as measured by NSE, changes for 10-6, T> Tg and eventually tends toward an exponential for T » Tg. Spin probes in rapidly fluctuating local fields are not sensitive to the functional form of S,,(t) (Ref. 6), but yield an effective correlation time T 10-7. defined bv

~~dt . (6)~~

en Values of x have been obtained for AgMn (Ref. 11) and .-l«Fe and C«Mn (Ref. 15) from zero-field uSR 10-9. measurements. Figure 4 is a scaled plot of zTs vs T/Ts, reproduced from Ref. 11. - AgMn (1.8 at.%) • 10 Mezei has obtained good fits of %(t) data obtained AuFe (1.4 at.%) A 10-10 from NSE in Cuq5Mn5 to the form : CuMn (1.1 at.%) O

~~1 r = =r (7) fc dE , r.- J,, 10"-M. i i i i I j i i 1~~

T/Tg which was motivated by considerations of distributions of barrier heights for activated hopping. (Its validity is not necessarily a demonstration of the FIGURE 4. Dependence of the scaled effective cor- importance of such barriers, however.) A good fit was relation time zTg on reduced temperature T/Tg > 1 14 in three metallic spin-glass systems. obtained for £„ = 300 K and T0 = 6 X 10~ s. Scaled values of these parameters, together with Eqs, (6) and Data points: results of muon-spin-relaxation measurements. (7), yield the curve in Fig. 4. There is good agreement Curve: fit of Eq. (6) to neutron-spin-echo data for between the uSR and NSE data, with no adjustable RESEARCH—Materials Science 103

7(0) for the manganese magnetic moment at field muon spin relaxation to measure microscopic temperatures well above the glass transition Tg. The properties of the quasi-static and dynamic local muon linewidth in a field H at a temperature T has fields. An important advantage of the muon tech- been measured to be proportional to H/ T in both nique for these experiments is that muon relaxa- AgMn (3.0 at.%) and AgMn (0.3 at.%), with excellent tion can be measured in a negligible external field agreement over this wide concentration range in the (<10 mOe in this experiment). This is crucial for slope of the linewidth vs H/ T. The H/ T slope de- studying the ferromagnet to spin-glass transition be- termines the total coupling of the muon to the man- cause any applied field will affect the transition by ganese local moment, including both dipolar and inducing ferromagnetic order in the spin-glass RKKY contributions.14 From the known dipolar phase.21 coupling, we have determined the strength of the The main conclusions can be summarized as fol- muon local-moment RICKY coupling. The s-d ex- lows: change energy 7(0) for the manganese can then be 1. The zero-field quasi-static linewidth in the fer- calculated from the muon Knight shift in pure silver. romagnetic phase shows the manganese spins to Values for 7(0) from uSR can be compared with be statically ordered—not just the iron spins, as results from other Lxperimentai techniques. has been recently suggested."21 Thii rules out the possibility that the ferromagnet to spin-glass s-d exchange energy J(O) in transition at Ts might represent a freezing of 7(0) = 2.4(1) eV uSR linewidth paramagnetic manganese clusters, independent 7(0) =1.5 eV NMR linewidth of a ferromagnetic ordering of the iron spins. 7(0) = 0.9(7) cV neutron scattering Instead, we find that both transitions take place 7(0) = 0.3(1) eV electron spin resonance (ESR) in a single spin system, dominated by manganese. The j*SR value of 7(0) requires that the AgMn 2. The Curie temperature Tc = 8.25 ± 0.1 K can be linewidth from the combined RKKY and dipolar identified from the uSR data by the peak in the couplings be 46% higher than the predicted linewidth zero-field spin-lattice relaxation rate, and is from dipolar coupling alone. This anomalously large consistent with the determination of Tc from ac linewidth is in complete agreement with previous 19 susceptibility. Above Tc, muon relaxation rates high-temperature measurements on AgMn (1.6 scale with muon rates in the giant moment at.%). We conclude that the large muon linewidths in ferromagnet PdMn (2 at.%) (Ref. 24),indicating AgMn are from a surprisingly large RKKY coupling that dynamic effects near Tc in reentrant from the muon to the manganese local moment and PdFe Mn are dominated by the manganese thai this requires an s-d exchange energy 7(0) in spins and that the temperature dependence is disagreement with published results from ESR and the same as that in a ferromagnet without reen- neutron scattering. trant behavior.

PrfFeMn References One of the unsolved problems in spin-glass re- 1. "Progress at LAMPF, January-December 1983," search is the nature of the double transition in mag- Los Alamos National Laboratory report LA-10070- netic systems with random exchange. These systems PR (April 1984). exhibit a transition to a ferromagnetic state at a Curie temperature T , followed by a transition at a lower 2. D. E. MacLaughlin, L. C. Gupta, D. W. Cooke, R. c H. Heffner, M. Leon, and M. E. Schillaci, Physical temperature T to a spin-glass-like state. The wide x Review Letters 51, 927 (1983). variety of materials exhibiting the reentrant ferromagnetic phase suggests that the double transition 3. V. Kannella and J. A. Mydosh, Physical Review B 6, is a common feature of magnetic systems with com- 4220(1972). peting interactions.20 4. R. H. Heffner and D. E. MacLaughlin, Physical We have studied i lead-based reentrant fer- Review B29, 6048(1984). romagnet [/WFe(0.35 at.%)] Mn (5 at.%) using zero- 104 PROGRESS AT LAMPF—1984

5. F. Mezei, ZeitschriftfeurPhysik 255, 146(1972). 21. H. Maletta, G. Aeppli, and S. M. Shapiro, Journal of Magnetism and Magnetic Materials 31-34, 1367 6. A. Abragam, Principles of Nuclear Magnetism (1983). (Clarendon Press, Oxford, 1961). 22. S. Senoussi, A. Hamzic, and I. A. Campbell, Journal 7. H. Alloul, S. Murayama, and M. Chapellier, of Physics F .Metal Physics 10, 1223 (1980). Journal of Magnetism and Magnetic Materials 31-34,1353(1983). 23. A. Kettschau, J. Boysen, W. D. Brewer, and I. A. Campbell, Journal of Magnetism and Magnetic 8. H. Alloul, in the Proceedings of the Heidelberg Materials 37, LI (1983). Conference on Spin Glasses, J. L. van Hemmen and I. Morgenstern, Eds., Lecture Notes in Physics 24. S. A. Dodds, G. A. Gist, D. E. MacLaughlin, R. H. (Springer-Verlag, Berlin, 1983), p. 18. Heffner, M. Leon, M. E. Schillaci, G. J. Nieuwenhuys, and J. A. Mydosh, Physical Review B 9. F. Mezei and A. P. Murani, Journal of Magnetism 28,6209(1983). and Magnetic Materials 14, 211 (1979); and A. P. Murani, F. Mezei, and J. L. Tholence, Phvsica 108B, 1283(1981). *' 10. F. Mezei, Journal of Applied Phvsics 53, 7654 (1982). Muon-Spin-Rotation Studies of Dilute 11. R. H. Heffner, M. Leon, M. E. Schillaci, D. E. Magnetic Alloys MacLaughlin, and S. A. Dodds, Journal of Applied Physics 53, 2174(1982). • Experiment 571—SMC 12. Y. J. Uemura and T. Yamazaki, Journal of Los Alamos, Rice Univ., Univ. of California at Riverside, Magnetism and Magnetic Materials 31-34, 1359 Sandia National Labs. (1983) Spokesmen: S. A. Dodds (Rice Univ.), and R. H. Heffner 13. Y. J. Uemura, T. Yamazaki, D. R. Harshman, M. andM. E. Schillaci (Los Alamos) Semba, J. H. Brewer, E. Ansaldo, and R. Keitel, in the Proceedings of the Yamada Conference on As previously reported,' Exp. 571 has successfully Muon Spin Rotation and Related Problems, measured muon diffusion in fee materials other than Shimoda, Japan, 1983, and in Hvperfine Interac- copper and aluminum, using a novel technique de- tions 17-19, 453 (1984). veloped at LAMPF. The diffusion data provide a 14. R. E. Walstedt and L. R. Walker, Physical Review « basis for understanding the apparently anomalous 9,4857(1974). motion of muons in copper, aluminum, and bec 15. Y. J. Uemura, T. Yamazaki, R. S. Hayano, R. materials, and aid in the interpretation of results Nakai, and C. Y. Huang, Phvsical Review Letters from our other muon-spin-rotation experiments. 45,583(1980). Although our primary interest is in the diffusion 16. Y. J. Uemura. Ph.D. thesis, University of Tokyo parameters, which are well established in the temper- (1981). ature region of interest, recent theoretical developments lead us to believe that we may be able to 17. H. Sompolinsky and A. Zippelius, Phvsical Review B 25, 6860 (1982). extract additional information about the impurity muon interaction and measure the muon diffusion to 18. S. Kirkpatrick and D. Sherrington, Phvsical Review somewhat higher temperatures. In particular, the B 17,4304 (1978). magnetic field dependence of the muon relaxation 19. J. A. Brown, R. H. Heffner, T. A. Kitchens, M. rate is not correctly described by our original model, Leon, C. E. Olsen, M. E. Schillaci, S. A. Dodds, and which simplifies the dynamics of the magnetic im- D. E. MacLaughlin, Journal of Applied Physics 52, purity and totally neglects the effects of the muon- 1766(1981). induced electric field on the impurity. P. M. Rich- 20. G. J. Nieuwenhuys, B. H. Veiheek, and J. A. ards, of Sandia National Laboratory, has now de- Mydosh, Journal of Applied Phvsics 50, 1685 veloped a scheme for calculating the muon relaxation (1979). that takes both of these effects into account. The RESEARCH—Materials Science 105 approach is to use a memory function technique to that may open a new avenue of research using muon- obtain the full spectral density of the impurity spin spin rotation. The details of the experiment are re- fluctuations from a set of coupled differential equa- ported below. Measurements on V2O3, a band-type tions (256 for erbium) and then to use the numerical conductor, also have been performed. Several ques- solution to calculate the muon depolarization as a tions have arisen concerning the nature of the metal- function of field and temperature. As expected, the insulator transition in this material and the im- more accurate calculations differ significantly from portance of its exact crystal structure. the simpler model. We are currently incorporating these results into Fe3O4 the code used for fitting the data. The modified code also allows for an increase in the muon hopping An anomalous discontinuity in both the local field activation energy for muon sites near the impurity. and linewidth around T = 250 K has been reported Preliminary results show good agreement with the previously in zero-applied-field studies of magnetite.' observed temperature dependence of the depolariza- These results, although quite old, have not been tion rate, using crystal field and conduction electron- understood. Mossbauer linewidths suggest that in the impurity interaction parameters deduced from inde- semimetallic state of magnetite the electron hop time pendent susceptibility and electron-spin-resonance T at 247 K has the same value as the period of the (ESR) measurements. The diffusion parameters re- muon precession in zero-applied field. Consequently, main unaffected because they are insensitive to the cross relaxation may be taking place because the details of the interaction. We expect that the fitting magnetic environment fluctuates with a characteris- will be completed and the results will be prepared for tic time T, which is equal to the inverse of the publication soon. frequency co of muon-spin precession (an ~ 1). We have performed new experiments in which we change the magnetic fluctuation time t by changing Reference temperature and then "retune" the muon-spin-rota- 1. "Progress at LAMPF. January-December 1983," Los tion frequency through the application of an external Alamos National Laboratory report LA-10070-PR field along the direction of magnetization <111>. (April 1984) p. 113. The coupling among the oppositely oriented magnetic sublattices in this ferromagnet is considered much stronger than the coupling to the applied field. The assumption is made, therefore, that the total observed magnetic field is simply the algebraic sum of Muon Spin Rotation in the applied field and the preexisting internal field. Selected Magnetic Oxides The results of this experiment were positive, as • Experiment 639 — SMC shown in Figs. 1 and 2. As was observed for zero Texas Tech Univ., Univ. of Wyoming, Los Alamos, external field, the average field changes from a lower Technical Univ. of Eindhoven in The Netherlands value above the crossover temperature to a higher one below. This frequency change appears to de- Spokesmen: C. Bockcma (Texas Tech Univ.). A. B. Dcnisnn (Vniv. ofWyoniing). and D. IV. Coake( Los Alamos) crease as the value of the external field is increased. The temperature range over which the cross relaxation occurs is relatively sharp (~ 5 K) for al! values of Introduction external fields used. During the past year the work on magnetic oxides Although the interpretation of these data is still has turned toward an investigation of the metal- speculative, we note the following. The temperature insulator transition materials magnetite (Fe3O4) and dependence of x, as extracted from our data, appears vanadium trioxide (V2O,). Particular attention has to follow an Arrhenius law with an activation energy been given to those experiments that use the muon to near 0.1 eV. If this activation energy is due to electron probe physical effects not amenable to other standard or polaron hopping, an interesting comparison can be techniques. A new effect has been observed in Fe3O4 made with the conductivity (or resistivity) in this 106 PROGRESS AT LAMPF—1984

temperature region. Parker and Tinsley report2 that at temperatuves near and above the Curie temperature (850 K) the resistivity is activated with an activation energy of 0.1 eV. Further, it is known3 that near the Verwey transition (123 K) the activation o energy in the mobility of the n-type carriers also is about 0.1 eV, whereas the activation energy for the conductivity between 123 K and near 500 K. is very much lower, Honig states4 that for well-annealed crystals the conductivity conform? strictly to an Ar- rhenius law, but with a varying activation energy. This is indicated in tabular form below.

~~Temperature Range (Ref. 4) E(eV)~~

Below 7", .= 123K 0.110 123-200 K 0.0438 Above 200 K 0.0074 o It is not clear, therefore, what mechanism is produc- 200 220 240 260 280 300 ing u"1" relaxation. If it is caused by hopping electrons Temperature (K) (from Fe2+ to Fe3+), then to explain the conductivity in this temperature range the density of carriers must 5 FIGURE 1. Temperature dependence of the muon change with temperature as well? It is known from hyperfine frequencies at 0-, 2-, and 3-kOe applied diffuse neutron scattering that for temperatures lower Fields. To compare relative changes, zero fre- than 250 K, molecular polarons (coherent atomic quency has been arbitrarily chosen. Note the tem- group motion) exist, and it is believed that these play perature shift in the frequency jump; for all fields a role in aiding electron hopping. This motion may this jump is reversed at Ty. Typical error is ±0.20 MHz. have an activation energy that is different from the actual hopping barrier, and we may be observing these or related phonon effects. The change in local field also may be attributed to the conduction mechanism. If indeed the electron is moving along the chains of Fe2+-Fe3+ cations, the magnetic moments of these two ions would be averaged when the electron motion is faster than the muon-precession frequency but would appear as two static moments when the motion is slower than the rotation frequency.

~~V2O,~~

3.8 3.9 Muon-spin-rotation measurements have been made on V O as a function of temperature and 1000 /T 2 3 external applied field. Electric and magnetic measurements have established that V O is an in- FIGURE 2. Muon hyperfine frequency as a func- 2 3 tion of reciprocal temperature at which cross re- sulating antiferromagnet below about 150 K, whereas laxation occurs. An Arrhenius fit yields an activa- above this temperature the material is a tion energy of 0.11 eV. paramagnetic, high-resistivity metal. It is expected RESEARCH—Materials So/etice 107

that the local magnetic field in V:O3 will be primarily To determine the direction of the intrinsic internal 3+ of V magnetic dipolar origin and that the field field (Z?im), an external magnetic field (Bnl) was magnitude and direction can be readily calculated. applied along the hexagonal c axis and tie magnitude Results of the temperature dependence of the local of the vector sum (Sobs) was monitored. Figure 4 field at the muon site in the absence of an external shows the results of the experiment with the fits as a field are shown in Fig. 3. The measurements taken as function of G, the angle between the internal field and the sample was cooled down show a rather large shift the hexagonal c axis. Based on pure dpole calcula- in magnetic transition temperature from that tions, sites were found that gave the magnitude and previously determined. This shift currently is not direction of the field actually observed. These sites explained, although Uemura found6 a similar result are shown in Fig. 5. Such sites have buen found by and it is known that a large hysteresis exists. Bates,7 based on electrostatic calculations and + Depolarization rates were measured as a function substantiated by infrared experiments on H in of temperature both above and below the transition aluminum oxide (A1:O3). temperature of 134 K. Below 134 K the rates are Further work is needed to understand the tempera- 1.0-2.5 us"1, and the relaxation function fit suggests ture hysteresis effect. Also, we must take into consid- that the muon is stationary or diffusing only locally.. eration the known monoclinic crystal distortion Above this temperature a nearly constant Gaussian below the transition temperature, which will help us relaxation rate of 0.2 us"' was observed, which also to understand

~~20 32 _~~

~~15 -• - » - 28 y B*&y 24 10 - 20 y^ -, 1 16 - x^ 5 -~~

~~12 •~~

-•—• 4 a • » I « m 50 100 150 200 8 - Temperature (K) 4 \e=i74°>/ FIGURE 3. Temperature dependence of the local + f 1 i i t field at the p. site in V2O3 taken in zero external field. 0.25 0.50 0.75 1.00 1.25 1.50 BMt(kG)

FIGURE 4. Directional dependence of the intrinsic internal field^of V2O3 as a function of external applied field (B\ c axis); 0 is the angle between the internal field and the hexagonal c axis. 108 PROGRESS AT LAMPF— 1S84

V O STRUCTURE 5. Y. Yamada. N. Wakabayashi, and R. M. Nicklow, 2 3 Physical Review B 21,4692 (1980). 6. Y. j. Uemura, T. Yamazaki, Y. Kitaoka, T. Mitakigawa, and H. Yasuoka, Hyperfine Interactions 17-19,339(1983). 7. H. Engstrom, J. B. Bates, J. C. Wang, and M. M. Abraham, Physical Review B 21, 1520 (1980).

Holmium-lon Dynamics in Ho^Lu, xRh4B, • Experiment 640 — SMC Rice Univ., Los Alamos, Sandia National Labs., Univ. of California at Riverside, Texas Tech Univ. Spokesmen: S. A. Dodds(Rice Univ.), R. H. HeffnerfLos Alamos), and D. E. MacLaughlin (Univ. of California at Riverside)

Introduction For the last several years the study1 of rare-earth (RE) Rh4B4 compounds has provided a rich source of information regarding the interplay of magnetic and superconducting phenomena. Discovered by Mat- thias and co-workers,: the ferromagnetic, supercon- • Vanadium ducting, and paramagnetic phase boundaries are by now well known.3 In addition, a set of crystal-field I j Oxygen parameters recently has been determined4 that gives a general overall accounting of the magnetization, "Muon Site" (Field Observed) * susceptibility, and specific heat data for several of these magnetic compounds. 5 1 FIGURE 5. Muon-stopping sites for \2O3 deduced Our group has been studying ' magnetic ion from dipole calculations that are consistent with dynamics, primarily in the HovLu,_vRh4B4 system, the observed field magnitude and direction. using the muon-spin-relaxation (uSR) technique. Here we report low-field measurements for .v = 0.02 and A" = 0.005, which become superconducting at References Tc =* 11 K. The results are discussed in terms of a model8 for the holmium-ion dynamics involving a 1. "Progress at LAMPF, January-December 1983," single-ion conduction electron relaxation mechanism Los Alamos National Laboratory report LA-9709- in the presence of strongly perturbing crystalline PR (March 1983). electric fields. The results have been recently re- 2. R. Parker and C. J. Tinsley. Physica Stains Solid! A: ported.11 Applied Research 33, 189(1976).

3. A. J. M. Kuipers and V. A. M. Brabers. Physical Data Collection and Analysis Review £20, 594(1979). 4. J. M. Honig, Journal of Solid State Chemistrv 45, Zero- and longitudinal-field data were collected in 1-13(1982). forward- and backward-positron telescopes using the standard time-differential uSR technique10" in RESEARCH—Materials Science 109

+ which the time rate of change of the u polarization is The uSR rate varies as \/Tt <£ f0), where Aco and Fo are the local-field 2. there is a dramatic change in the temperature amplitude and spin-fluctuation rate, respectively. dependence of Fa in going from the fast- to the For dipolar coupling, (Aw)2 « .v\ where .v is the Ho3+ slow-fluctuation regimes; and + concentration. In this regime the measured u relaxa- 3. the temperature dependence of Fo in the super- tion function G,(t) is given by the root-exponential conducting state (also the slow-fluctuation re- m 13 form G.(t) = exp[-{t/T{) l as expected for a sys- gime) is unusual, as discussed below. tem of dilute magnetic ions. Also, the full u+ asymmetry (zero-time polarizat:on) is observed. These data are plotted in Fig. 1 (square symbols). As the figure shows, the measured 1/7", values do indeed have an x2 concentration dependence, indicating that the Fo is roughly independent of holmium-ion concentration. Furthermore, the temperature dependence is ccnsistent for a process with activation energies of 66 ± 8 K forx = 0.005 and 66 ± 1 K for* = 0.02.

~~Slow-Fluctuation Regime. In the quasi-static re- 12 gime (Am s> Fo), the uSR function is well described by~~

~~G.(0 = (1 - a) exp(-of) + a exp(-//T,) . (1) / Tj' FILLED SYMiOLS i.0.008 ' I OPEN SYMBOLS i-0.02~~

where l/r, ~ Fo, a » \/Tt, and a is a constant <1, 0.01 7 as reported earlier. 0.1 0.2 0.3 The quasi-static regime sets in at T < 9 K for I/T (K) A- = 0.02 and T < 6.5 K for .v = 0.005 in the superconducting state for both concentrations. The a parameter is temperature independent and is given FIGURE 1. Temperature dependence of the muon by o(.v = 0.02) = 11.5 ± 0.5 us"' (reported earlier7) spin-lattice relaxation rate 1/7", in 1 Ho,Lii| ,Rh4B4. The fllled-in symbols are for ando(x=0.005) = 3.2±0.05 us" , oro/yM « 130and x = 0.005; the open symbols, for x = 0.02. The 36 Oe, respectively. (The muon gyromagnetic ratio y,, circles are for the slow-fluctuation limit; the 2 1 1 = 8.51 X 10" Oe" us" .) Thus o varies linearly with squares, for the rapid-fluctuation limit (see text). concentration, as expected for a local-field, in- The superconducting transition temperature is de- 714 homogeneous linewidth. noted by Tc. 110 PROGRESSATLAMPF—1984

The first point suggests that the dominant relaxation energy is about 120 K. This discrepancy with the process is due to single-ion, conduction electron scat- measured value of 66 K may indicate that the crystal- tering (Korringa mechanism).15 Consequently, in the field parameters are not precisely known. superconducting state and in the absence of crystal- All of our measurements in the slow-fluctuation field effects, one might expect that the temperature regime T < 10 K are also below the superconduct- dependence of Fu would exhibit the usual exponential ing temperature Tc — UK. For a single-ion relaxa- decay for T < 0.5 T( with an activation energy cor- tion process the Korringa rate TK is expected to vary responding to the BCS gap parameter As. (Here, A5 =* as exp(-A/T) for T s 0.5 Tc. Previous "B NMR 16 16 19.5 K.) Indeed, this is observed using "B nuclear measurements in YRh4B4 with small amounts of magnetic resonance (NMR) in YRh4B4. In our case, gadolinium and erbium were used to infer a fluctua- however, an activated temperature dependence is tion rate of the RE spin varying as Tp in the super- found with an activation energy =10 K. We now conducting state, with p between 2 and 3 in low fields. discuss the temperature dependence of Fo in detail. The observed concentration dependence there sug- It is well established4 that the eigenstates of the gested a dominant spin-spin relaxation mechanism J — 8 Ho3+ multiplet possess the dominant crystal- (RICKY).13 By contrast, our uSR results5-7 in field symmetry of the RE Rh4B4 lattice. In an attempt HoA.Lu,_vRh4B4 for .v = 0.7 show a relaxation rate to understand the three main points listed above, the holmium-ion relaxation rate from conduction electron scattering has been calculated for the full crystal- field Hamiltonian using the methods and equations described in Ref. 8. To a first approximation the states of the easy-axis (oaxis) system are simply |±m> with no admixture, where m is the integer for quantization along the symmetry axis. Normally, one expects to have no relaxation within the degenerate |±8> ground-state doublet because there are no off- dibgonal matrix elements of J. This implies that relaxation would require an excitation through the ia complete splitting of 120 K appropriate to this system.4 However, we find that Am = ±4 terms in the crystal field produce a zero-field splitting in the ground state (and in some of the degenerate excited states as well), and thereby induce a slow ground- a! state relaxation process involving gfi (Ref. 17), the only nonzero component of the g tensor for this Ising system. The main features of the data are now discussed within the context of this model. The uSR 7*, is highly activated above about 10 K (in the fast- I/TCK) fluctuation regime), in qualitative agreement with the necessity for rapid relaxation to proceed through + excited states but with an activation energy of about FIGURE 2. Temperature dependence of the n one-half of the overall splitting. Figure 2 shows the spin-lattice relaxation rate 1/Jt in calculated ry [actually the zero-frequency compo- Hoo.o2Lu0.98Rh.|B., (data points). The solid curve for T~l < 0.1 shows the calculated (see text) temper- nent ] multiplied by the proper con- ature dependence of l/Tt in the fast-relaxation stants to give 1/r, in the fast-relaxation limit. There limit. For 7"1 > 0.1, the solid curves are the are no adjustable parameters other than IN(0) = 0.08, calculated values of l/T, for three assumed tem- where / is the exchange interaction and N(0) is the perature dependences of the Korringa scattering density of states. As noted above, the activation rate below the superconducting temperature Tc. RESEARCH—Materials Science 111 nearly the same as that for .v = 0.02; therefore, 3. M. B. Maple, H. C. Hamaker, D. C. Johnson, H. single-ion processes must be quite important in B. McKay, and L. D. Woolf, Journal of Less- Ho.vLu,_,Rh4B4. Common Metals 62, 251 (1978). The calculated l/T, for T < 10 K is shown in 4. B. D. Dunlap, L. N. Hall, F. Behroozi, G. W. Fig. 2, taking the Korringa coupling parameters to 2S Crabtree, and D. G. Niarchos, Physical Review B vary both as T and as exp(-As/T). In both cases 29,6244(1984). the coupling is normalized to be continuous at Te, above which it is proportional to T. For comparison 5. C. Boekema, R. H. Heffner, R. L. Hutson, M. the curve for no superconductivity also is given; the Leon, M. E. Schillaci, J. L. Smith, S. A. Dodds, details are discussed in Ref. 9. The theoretical agree- and D. E. MacLaughlin, Journal oj Applied Phys- ment is good, both for the order of magnitude of 1/T, ics 53, 2625 (1982). and for the temperature at which the relaxation 6. D. E. MacLaughlin, S. A. Dodds, C. Boekema, R. ceases to be highly activated (T — 7.8 K). H. Heffner, R. L. Hutson, M. Leon, M. E. As for the change in temperature dependence, we 57 Schillaci, and J. L. Smith, Journal of Magnetism note that in earlier work it was tempting to and Magnetic Materials 31-34,497 (1983). speculate that this change was strictly related to the onset of superconductivity because both occurred in 7. R. H. Heffner, D. W. Cooke, K. L. Hutson, M. the same temperature region. In the light of the Leon, M. E. Schillaci, J. L. Smith, S. A. Dodds, L. calculated results presented here and elsewhere,8 it C. Gupta, D. E. MacLaughlin, and C. Boekema, now appears that this crossover occurs near Tc by Journal of Applied Physics 55, 2007 (1984); and coincidence and that it is dominated by a changeover "Progress at LAMPF, January—December to relaxation within the doublet ground state. Similar 1983," Los Alamos National Laboratory report results can be seen in recently reported NMR studies LA-10070-PR (April 1984). on YRh4B4 with small concentrations of holmium, 18 8. P. M. Richards, in Magnetic Excitations and dymium, and terbium. Fluctuations. S. W. Lovesey, U. Balucani, F. In spite of the good agreement, a puzzling point Borsa, and V. Tognetti, Eds. (Springer-Verlag, remains: there is a small but definite concentration New York, 1984), p. 207. dependence to Fo in the superconducting state whereas almost none is observed in the normal state. 9. R. H. Heffner, D. W. Cooke, R. L. Hutson, M. E. This cannot be accounted for by assuming that F=F, Schillaci, J. L. Smith, P. M. Richards, D. E. MacLaughlin, and S. A. Dodds, in the Proceed- + .vF2 (for any reasonable single-ion Ft and RKKY ings of the 30th Annual Conference on F:) without contradicting the fact that there is little difference in r, between 2 and 70% holmium, both Magnetism and Magnetic Materials, San Diego, California, November 27-30, 1984 (to be pub- above and below Tc (Ref. 7). The data act as if there were a significant concentration dependence to the lished in the Journal of Applied Physics). manner in which the single-ion relaxation rate is 10. A. Schenck, Nuclear and Particle Physics at Inter- affected in the superconducting state, for which we mediate Energies, J. B. Warren, Ed. (Plenum have no explanation. Press, New York, 1976), p. 159; and J. H. Brewer and K. Crowe, Annual Review of Nuclear Science 28,239(1978). References 11. R. S. Hayano, Y. J. Uemura, J. Imazato, N. 1. "Proceedings of the International Conference on Nishida, T. Yamazaki, and R. Kubo, Physical Ternary Superconductors," G. K. Shenoy, B. D. Review 5 20, 850(1979). Dunlap, and F. Y. Fradin, Eds. (North-Holland, New York, 1981). 12. A. Abragam, The Principles of Nuclear Magnetism (Clarendon Press, Oxford, 1961). 2. B. T. Matthias, E. Corenzwit, J. M. Vandenberg, and E. Barz, Proceedings of the National 13. M. R. McHenry, B. G. Silbernagel, and J. H. Academy of Sciences 74, 1334 (1977). Wernick, Physical Review B 5, 2958 (1972). 112 PROGRESS AT LAMPF—1984

14. R. E. Walstedt and L. R. Walker, Physical Re- Three temperature regions of distinctly different u+ view B 9,4857 (1974). relaxation behavior are exhibited by UPt,. For T, < T < 1.75 K the rate in a n .••.- ; GO-Oe transverse field 15. H. Hasegawa, Progress of Theoretical Physics 21, is constant at 0.057 us'1 but falls to 0 in a 100-Oe 483(1959). longitudinal field. The magnitude and field de- 16. K. Kumagai and F. Y. Fradin, Physical Review B pendence of the muon-spin-relaxation (uSR) rate is 27,2770(1982). consistent with spin dephasing from |g5Pt nuclear dipoles. 17. J. M. Baker and B. Bleaney, Proceedings of the At T . there is a jump in the depolarization rate to Royal Society A24S, 156 (! 95S). t 0.072 us"1, which remains constant down to our 18. K. Kumagsl Y. Honda, and F. Y. Fradin, 17th lowest temperature of 0.165 K. Application of a 5000- Intrrriational Conference on Low Temperature Oe longitudinal field in this interval causes the re- Physics, Karlsruhe, Germany, August 1984. laxation rate to fall to 0. This suggests that the relaxation mechanism is associated with a static rather than a dynamic process, the origin of which is presently unknown. It seems unlikely that the increased rate is due to an external field in- Muon-Spin-Relaxation Studies of homogeneity. Using trim coils and a Hall probe, the Itinerant Magnets and Heavy-Fermion external field at the sample site was set to 0 within 10 Superconductors mOe. which is much smaller than the 175 mOe • Experiment 842 — SMC required for the observed rate increase. Similar zero- field measurements on UBe,, and the conventional Los Alamos, Rice Univ., Univ. of California at Riverside superconductor Pba,,In(), indicated no such anomaly Spokesmen: R. H. Heffner (Los Alamos) and D. E. at Tt.. We point out that although UPt, and UBe,, are MacLaughlin (Univ. of California at Riverside) both heavy-fermion superconductors, they behave quite differently with respect to their physical Much interest has been generated among con- properties, such as resistivity and specific heat. densed-matter scientists by the discovery of heavy- + 1 Above 1.75 K the zero-field u relaxation rate fermion systems, that is, compounds that behave as 1 Fermi liquids with large effective mass electrons rapidly falls to 0.02 us" , remaining constant to near 6 {m*~ 200 me). To date.eight such systems have been K. With increasing temperature, the rate exhibits a identified,' of which three have also been found to maximum near 12 K and subsequently falls slowly to 0 at 20 K. A similar peak in the basal-plane ac exhibit superconductivity—namely, CeCu2Si2 (Ref. 4 susceptibility data of UPt, has been reported by 2), UBeu (Ref. 3), and UPt3 (Ref. 4). Stewart et al. 7 have suggested the possible coexistence of bulk super- Frings et al. Therefore this relaxation rate peak may conductivity and spin fluctuations (paramagnons) in be associated with an intrinsic, but not yet under- UPt.,, which, if correct, would represent the only stood, magnetic effect in UPt,. known coexistent system in nature. Moreover, argu- The observed decrease in the relaxation at 1.75 K + ments have been promulgated56 suggesting that some may be due to a change of the u site. Longitudinal of these systen-.s exhibit a type of superconductivity field data taken at 5, 10. and 17 K show zero relaxa- + that is different from the usual metallic BCS super- tion, which indicates that the u is immobile at these conductors studied thus far. temperatures. Additional data near 1.75 K should + + clarify the situation regarding u motion. Positive muon (u ) spin relaxation measurements The 0- or 100-Oe transverse-field u+ relaxation rate on polycrystalline UPt, and UBe13 have been carried 1 out. Metallographic analysis on UPt, indicates that for UBel3 (T, = 0.89 K) is constant at 0.30 us" in the the sample contains less than 2% spurious phases and interval between 0.20 and 2.5 K. However, this rate falls to 0 by application of a 100-Oe longitudinal exhibits superconductivity below T, = 0.41 dz 0.02 K. + as determined by ac susceptibility measurements. field. These results suggest u spin dephasing by inhomogeneous ''Be nuclear moments. RESEARCH—Materials Science 113

References directional leaks at low temperatures, resulting in poor dilution refrigerator vacuum and a base mixing- 1. G. Stewart, Reviews of Modem Physics 56, 755 (1984). chamber temperature of only 235 mK that could be maintained for only ~ 1 h. A new design alleviated 2. F. Stegtich, J. Aarts, C. D. Bredl, W. Lieke, these problems, and we are now able to achieve a D. Meschede, W. Franz, and J. Schafer, Physical Re- mixing-chamber temperature of 78 mK. This tem- view Letters 43, 1892(1979). perature has been maintained for 3 days, indicating 3. H. Ott, H. Rudigier, Z. Fisk, and J. Smith, Physical that the system is thermally stable. Review Letters 50, 1595(1983). Installation of a 1° heat shield, which surrounds 4. G. Stewart, Z. Fisk, J. Willis, and J. Smith, Physical the counterflow heat exchanger and a portion of the Review Letters 52, 679 (1984). mixing chamber, further reduced our base tempera- 5. P. Anderson, Physical Review B 30, 1549 (1984). ture to 61 mK, For physical reasons, we cannot yet extend this shield all the way down to the sample to 6. D. Bishop, C. Varma, B. Batlogg, E. Bucher, Z. Fisk, further reduce the radiative heat load on the refriger- and J. Smith, Physical Review Letters 53, 1009 ator and sample, but we will implement this im- (1984). provement in the near future. 7. P. Frings, J. Franse, F. de Boer, and A. Menovsky, Additional modifications to the dilution refriger- Journal of Magnetism and Magnetic Materials ator and gas-handling units were made to enhance the 31-34,240(1983). overall reliability. A new wiring scheme was implemented that minimizes risks of broken leads and electrical shorts and also provides a more convenient access to the numerous electrical connectors mounted in the dilution refrigerator vacuum space. A by-pass line was included in the still plumbing line to Muon-Spin-Relaxation Dilution Refrigerator allow continuous pumping while isolating the D. W.Cooke(LosAlamos) booster pump during its warm-up period. The objective was to minimize helium-gas entrainment in the During the past year the muon-spin-relaxation cold diffusion pump oil by directing the gas flow (uSR) 3He-4He dilution refrigerator was com- through a by-pass line until the diffusion pump had missioned and integrated into the uSR spectrometer. attained its normal operating temperature. Final bench tests were completed in early May and With these modifications the uSR 3He-4He dilu- the refrigerator was used for the first time during the tion refrigerator is approaching its design value of 50 June run period. Its successful operation during that mK. During bench tests we achieved a mixing- time was followed by a second satisfactory run in chamber temperature of 61 mK and maintained 70 October. mK reliably with temperature regulation. Using a The major improvement that contributed to the potentiometric conductance bridge and automatic success of the dilution refrigerator was the redesign temperature controller, we demonstrated that ac- and construction of the 4He vessel. This container, curate temperature regulation could be achieved in which holds liquid helium used for precooling the the interval between 70 mK and 4 K. Additional dilution refrigerator and operating the 1 K plate, improvements are under active consideration. These provides access to the vacuum environment of the include installation of a larger counterflow heat ex- refrigerator components. The feedthroughs provid- changer, to further reduce the mixing-chamber tem- ing this access therefore must be high-quality, perature, and a more compact design of the electrical vacuum-tight joints that are not susceptible to cold and plumbing connections between the gas-handling leaks. The previous "He vessel was plagued by uni- units and the dilution refrigerator. 114 PROGRESS AT LAMPF—1984

Experimental Study of experiment showed that an increase by at least a Muon Beam Chopping for factor of 6 above the present data rates could oe Muon-Spin-Relaxation Experiments achieved with such a beam-chopping technique. In addition, the computer studies indicated that, with R. L. HutsonandR. H. Heffher (Los Alamos) proper beam tuning and the use of a beam chopper/separator working in a pulsed mode, the beam Introduction could be turned on and off fast enough to make the In July 1984 the final feasibility study of a beam- chopping concept work. chopping system for the LAMPF muon-spin-relaxa- Experimental tests in the fall of 1983 have shown tion (nSR) program was completed. The goal was to that the technique has no obvious flaws. The elec- show that data rate limitations caused by muon tronics for controlling the high-voltage switching for pileup at high muon rates can be circumvented by the chopper/separator worked satisfactorily, rough beam chopping. tuning of the muon beam was accomplished, and Muon-spin-rotation experiments involve measur- separation of muons and contaminant positrons in ing the intervals between the time of arrival of a the beam was observed. positive muon in a sample and the time when the muon decays into a positron. If more than one muon Results stops in a sample within a period of time shorter than about five muon lifetimes, it cannot be determined In July 1984 the fin'1 beam-chopping feasibility which muon is associated with the subsequently de- study was completed. Results of these measurements tected positron and thus the time interval cannot be are summarized in Table I. determined unambiguously. Therefore it is important that the instantaneous rate of arrival of muons Summary be kept roughly below 20 kHz to prevent a significant number of ambiguous data events. The results of this study met or exceeded expecta- To avoid these muon pileup problems, a new type tions; therefore, plans for a permanently located uSR of uSR experiment has been performed in which only facility are proceeding. This facility will occupy an one muon is allowed in the sample at a time. This is expansion of Cave A of the SMC and will comprise a accomplished by turning the muon beam off as soon chopper/separator, a bending magnet, two quadru- as a muon enters the sample and by keeping it off pole focusing magnets, a muon-spin rotator, and the until a decay is detected or until some specified time uSR spectrometer. The schedule is to have the system passes. After either of these conditions is satisfied, (minus spin rotator) operational in the summer of another muon can be allowed into the sample by 1985 and to incorporate the spin rotator within a year turning the beam back on. Calculations before the afterward. RESEARCH—Materials Science 115

~~TABLE I. Results of Measurements of Final Beam-Chopping Study.~~

~~1. Muon Beam Spot Sizes Beam Size Position of (Horizontal Times Vertical) Measurement (cm FWHM) Predicted Measured~~

Chopper slit 3.0 X 2.0 3.5 X 2.5 uSR sample 1.0 X 1.0 1.2 X 1.2 Because of multiple scattering of the low-momentum surface muons by the beam-profile monitor windows and the beam-channel vacuum window, the measured spot size is somewhat larger than the predicted size.

2. Muon Rate at the uSR Sample Position (Unchopped-Beam Mode) This rate measurement was done with a l.27-crn-diam scintillation counter placed at the sample position. Calculations indicated that the measured rate should have been roughly 23 kHz average, whereas a value of 16.2 kHz was obtained. This is most likely due to an imprecise specification of the channel apertures in the program TURTLE, which was used to predict the rates.

~~3. Beam Rise and Fall Times Rise Time (ns) Fall Time (ns)~~

~~Predicted =100 =100 Measured 160 60~~

~~4. Beam Extinction Efficiency (Beam Turned Off with Chopper) u rate (beam off)/H rate (beam on) = 1: 1540~~

~~5. Electron Contamination u/e ratio > 40~~

~~6. Measured Beam Asymmetry (Measure of Muon Beam Polarization) The asymmetry value was 0.20 or greater. This value is also typical for experiments done with decay muon beams.~~

7. Data Rates The chopper electronics available for this study required pulsing the beam no faster than once every 64 us. However, the data rates measured under these conditions indicate that a decrease of the pulse period to 15 us will result in an increase of the data rates by a factor of 6 to 7 over those currently attainable. This compares very well with the predicted factor of 6.

8. Background Calculations indicate that the backgrounds observed in this study are attributable to radioactive gas that diffuses from the LAMP'" A-2 target through the channel vacuum pipe to the vicinity of the uSR sample. With a thin gas barrier placed in the channel, it is estimated that backgrounds will be at least an order of magnitude smaller than those observed in experiments currently done with an unchopped decay muon beam. 116 PROGRESS AT LAMPF—19B4

Muon Channeling for The data from these experiments have not yet been Solid-State Physics Information completely analyzed; nevertheless, analysis to date has yielded some exciting results. For copper, com- • Experiment 787 — Biomed parison of the measurements with different crystal Los Alamos, Max Planck Institute at Stuttgart, Texas Tech orientations indicates that the octahedral and Univ., Technical Univ. of Munich, Univ. of Mississippi tetrahedral sites are occupied with roughly equal Spokesmen: G. Flik (Los Alamos/Max Planck Institute at probability near room temperature. At very low Stuttgart), K. Mater (Max Planck Institute at Stuttgart), temperatures (<70 K), however, the octahedral site is and .17. Paciotti (Los A lamos) strongly favored, with the transition occurring in the neighborhood of 150 K. This interpretation is consis- Muon-channeling experiments began this past tent with nSR results, which cover the temperature summer at the Biomedical channel at LAMPF. In region up to ~ 150 K. For iron-doped copper the these experiments, pions (JI+) are stopped in single + results are similar to those for pure copper above crystals, and the decay muons (u ), a small percent- 20 K; however, at about 10 K there is evidence for age of which are channeled by the crystal lattice, are pion trapping near the iron site. detected by a scintillation counter several meters from the crystal. The experiments are carried out in For tungsten (bec), the channeling signal observed vacuum to avoid scattering of the channeled parti- in the <111> direction at room temperature exhibits "cles, which are contained within an angular envelope the same peak shape as that observed in earlier SIN of < 1°. Constraints imposed by detector resolution measurements. The peak height remains roughly cause a long muon flight distance (7-13 m), which in constant down to ~ 100 K, after which it drops with turn results in low count rates. Because the channel- decreasing temperature. Our interpretation of this ing angle depends approximately on \fZ (crystal behavior is that above 100 K the pion is localized at atomic number), studies of low- to medium-Z tetrahedral sites and that below 100 K the channeling crystals arc practical only with very intense pion signal is weakened as a result of pion trapping by beams such as those available at the LAMPF Bio- molybdenum impurities (~50ppm). If correct, this medical channel. interpretation implies that the pion is very mobile at low temperatures—the estimated pion hopping rate The crystals studied included copper, iron-doped 12 1 is -7% of the Debye frequency (a> a 8 X 10 s" ) copper, tungsten, silicon, germanium, and gallium D at 30 K. These results are significant because there is arsenide. One objective if the experiments was to no other experiment that yields information on the determine the pion stopping site and, in some cases, behavior of hydrogen in tungsten. Where diffusion to compare the results with those obtained indirectly + and trapping are concerned, the 7t may be viewed as using muon-spin-relaxation (uSR) techniques. A a light isotope of hydrogen. Helitran continuous-flow cryostat was used to vary temperature in the range from 10 Y to room tempera- For the semiconductors, an additional question we ture. For each type of crystal, channeling measure- hope to answer is whether or not pionium is formed ments were made with different crystal orientations in analog with the muonium formation seen in uSR to determine the 7t+ stopping site(s). For example, in experiments. To this end the crystals were il- fee copper when the pion is localized at octahedral luminated with intense light to increase the charge interstitial sites, muon channeling will occur in the carrier population, which possibly could affect the <110> direction and blocking will occur in the rate of pionium formation. Preliminary analysis of and directions. For tetrahedral stop- the data seems to indicate that a light-on/light-off ping sites, however, blocking will occur in the <111> effect is observed in the channeling peaks; however, a direction and channeling in the <100> and <110> more definite conclusion requires further analysis directions, with a double peak expected in the last Information on the pion stopping sites also is being case. investigated. RESEARCH—Materials Science 117

Radiation-Effects Studies Material-damage parameters for 760-MeV protons and the neutron spectrum expected at target station 2 Design of an irradiation facility at the LAMPF A-6 were calculated. For copper metal, the helium- target station A-6 was completed. The facility will production to atomic-displacement rate in the neu- 4U0W controlled, in situ, radiation-effects studies in tron flux was near that expected in a fusion reactor the direct primary proton beam, as well as in a environment. neutron flux of about 6 X IOU cnT: sH that results In anticipation of the completed irradiation fa- from the primary beam's interaction with isotope- cility, where a large number of experiments can be production targets and the beam stop. Three inde- conducted simultaneously, a number of experi- pendent proton-irradiation inserts and twelve inde- ments* hav;- been identified, as summarized below: pendent neutron-irradiation inserts will be available. • radiation-produced point-defect/dislocation in- Capability for remote handling of irradiated speci- teraction observed by internal friction; mens is being developed. • radiation-produced point defects and defect Fabrication and installation are in progress. The clusters observed by field ion microscopy; scheduled date for completion of the facility is April • comparative study of the effect of varying 1985. helium-production rates on microstructural A foil-activation experiment1 was conducted in the evolution under irradiation; neutron flux at target station A-6 as a comparison • flux and spectrum map of the target station A-6 with previous Monte Carlo calculations. Good agree- neutron irradiation area; ment in both flux and spectrum was found; the spectrum resembles a fission spectrum with an additional high-energy tail (Fig. 1). *For related information, see Refs. 3 and 4.

~~1 1~~

~~9 IO' - in EBR-II ...:••••""'"•••••,. IO'8~~

~~7 i IO' i i IO'6 S1 o IO'5 LAMPF I014 i~~

~~3 \ IO' li r a> IO12 ..: i Q. i i RTNS-II i IO" :" r I IO10 t~~

~~in9 1 1 i i i i i J 1 10"7 io'6 10'5 io~4 IO'3 IO"2 IO'1 io° io' io2 103 Neutron Energy (MeV)~~

FIGURE 1. Flux per unit lethargy for target station A-6 at LAMPF, the Experimental Breeder Reactor (EBR-II) at Argonne National Laboratory-West in Idaho, and the Rotating Target Neutron Source (RTNS-II) at Lawrence Livermore National Laboratory. 118 PROGRESS AT LAMPF—1984

• nuclide production by spallation neutrons; Calculation of Displacement and • target-materials studies at the Spallation Neu- Helium Production at the tron Source (SNQ) at the KFA Laboratory in LAMPF Irradiation Facility Julich, Germany; M. S. Wechsler (Los Alamos/Iowa State Univ.), D. R. • radiation damage in samarium-cobalt perma- Davidson and W.F. Sommer (Los Alamos), andL. R. nent magnets; Greenwood (Argonne National Lab.) • radiation effects in optical materials for the free electron laser; Differential and total displacement and helium- • crack growth in 800-MeV proton- and neutron- production rates are calculated for copper irradiated irradiated alloy 718, which is a candidate for the by spallation neutrons and 760-MeV protons at LAMPF vacuum-to-air window; and LAMPF. The calculations are performed using the 1 • SIN target materials. SPECTER and VNMTC2"4 computer codes, the latter being specially designed for spallation radiation- damage calculations. For comparison, similar References SPECTER calculations are also described for irradia- 1. D. R. Davidson, W. F. Sommer, and R. C. Reedy, tion of copper in the experimental breeder reactor "Measured Radiation Environment at the Clinton P. (EBR-II) at the Argonne National Laboratory-West Anderson Los Alamos Meson Physics Facility Ir- in Idaho, and in the rotating target neutron source radiation Facility," accepted for publication in the (RTNSi-II) at Lawrence Livermore Laboratory. The Proceedings of the Twelfth International Sym- neutron energy spectra for LAMPF, EBR-II, and posium on Effects of Radiation on Materials, RTNS-II are plotted in Fig. 1. The displacement and Williamsburg, Virginia, June 18-20, 1984. helium-production cross sections are plotted in Figs. 2. M. S. Wechsler, L. R. Greenwood, W. F. Sommer, 2 and 3, respectively. and D. R. Davidson, "The Calculation of Radiation Damage Parameters for the Clinton P. Anderson Los Substantial contributions to displacement and Alamos Meson Physics Facility Irradiation Facility," helium production are due to neutrons in the high- accepted for publication in the Proceedings of the energy tail (above 20 MeV) of the LAMPF spallation Twelfth International Symposium on Effects of neutron spectrum; 26% of the displacements per Radiation on Materials, Williamsburg, Virginia, atom (dpa) and 95% of the atomic parts per million June 18-20, 1984. (appm) of helium are produced by high-energy neu- 3. O. T. Inal and W. F. Sommer, "Radiation Effects in trons. Secondary protons contribute only about 6% of Materials," accepted for publication in the Proceed- the dpa's produced by the spallation neutrons. The ings of the Sixteenth National Sample Technical results of the calculation for neutrons at LAMPF, Conference, Albuquerque, New Mexico, October EBR-II, and RTNS-II are listed in Table I. 9-11,1984. Still higher production rates are calculated for 4. M. W. Wechsler, W. F. Sommer, and D. R. irradiations in the direct proton beam. The produc- Davidson, "Internal Friction, Microstructure and tion rates are 6.3 X 10"7 dpa/s and 6.6 X 10~5 appm Radiation Effects," submitted to the Fifth Interna- helium/s, giving a ratio of 103 appm helium/dpa. In tional Symposium on Metallurgy and Materials Sci- ence, Symposium of Microstructural Characteriza- addition, a wide range of spallation recoil nuclei are tion of Materials by Non-Microscopical Techniques, produced. The production cross section for all spalla- Roskilde, Denmark, September 3-7, 1984 (LA- tion nuclei is about 1 b, as compared with 0.55 b for UR-84-1891). helium. These results will provide useful background information for research to be conducted at a new irradiation facility at LAMPF. RESEARCH—Materials Science 119

~~7 6 s 4 3 2 3 io' io" »o' io" io io" IO1 IO2 io Neutron Energy (MeV)~~

~~FIGURE 1. Neutron flux per unit lethargy for LAMPF, EBR-II, and RTNS-II. The proton current at LAMPF was 1 mA (compare with Fig. 1, p. 117).~~

~~ICf~~

~~•2 IO3 o CO to~~

o 10*

~~e o o o. in~~

~~ICP 4 io 10 10 10 10 10 10 Energy (MeV)~~

~~FIGURE 2. Displacement cross section vs energy as calculated by computer codes SPECTER and VNMTC. 120 PROGRESS ATLAMPF—1984~~

~~IO IO IO" IO Energy (MeV)~~

~~FIGURE 3. Helium-production cross section vs neutron energy based on ENDF/B-V (computer data file) and as calculated by computer code VNMTC.~~

~~TABLE I: Spectral-Averaged Radiation-Damage Parameters for LAMPF, EBR-II, and RTNS-II. LAMPF EBR-II RTNS-II~~

~~cp«o,ai(10I7n/m7s) 5.5 170 0.3 a£(keVb) 54 41 300 Mb) 720 540 4010 Arf(10-8dpa/s) 4 92 1.2 3 an(10- b) 13 0.037 52 7 Ka (10~ appm helium/s) 7 0.6 1.6 KJKd (appm heiium/dpa) 18 0.7 13~~

References 1. L. R. Greenwood, "Recent Developments in Neu- 3. K. Chen, Z. Fraenkel, G. Friedlander, J. R. Grover, J. tron Dosimetry and Radiation Damage Calculations M. Miller, and Y. Shimamoto, Physical Review 166, for Fusion Materials Studies" (to be published in the 949-967(1968). Journal of Nuclear Materials). 4. I. Dostrovsky, Z. Fraenkel, and G. Friedlander, 2. W. A. Coleman and T. W. Armstrong, Nuclear Sci- Physical Review 116,683-702 (1959). ence and Engineering 43,353-354 (1971). RESEARCH—Materials Science 121

Measured Radiation Environment at the Measured activation data and reaction cross sec- LAMPF irradiation Facility tions gave a primary proton flux of 5.4 X 1018 p/nr/s for a 600-uA current. This was a factor of 2 greater D. R. Davidson, R. C. Reedy, and W, F. Sommer (Los Alamos), andL. R. Greenwood (Aigv.me National Lab.) than the calculated proton flux based on the beam spot size and the current. The difference is caused by A foil activation dosimetry experiment was con- uncertainties in the proton spectrum and the proton ducted at the LAMPF beam-stop area to characterize cross sections. the radiation environment and to identify techniques Results of the calculation and dosimetry measure- for spallation radiation measurements. Foils were ment at the LAMPF beam stop gave good agreement irradiated for ~8 weeks in the primary proton beam for the neutron flux within the errors of the measured and in the spallation neutron flux in isotope produc- activities, flux, and cross sections. The present tion stringer 5. The STAY'SL computer code* was used measured flux can be used to evaluate proposed to determine the most probable spectrum, consider- experiments for the neutron irradiation facility. Ad- ing the measured activities, the input spectrum, and ditional cross sections and reactions are necessary to the activation cross sections. The measured spalla- improve the characterization up to 800 MeV. Shorter tion neutron flux was 5.5 X 10" n/nr/s/mA ± 7%. A irradiations at several locations in the new facility are previous Monte Carlo calculation2 gave a total neu- planned for the next run cycle. The computer calcula- tron flux of 6.0 X 1017 «/m-/s/mA ± 3%. Comparison tion will be repeated to gain better statistics, and of the measured and calculated fluxes gave a dif- comparisons will be made with the dosimetry ference of about 8%. The measured and calculated measurements. neutron energy spectra are shown in Fig. 1. The secondary proton flux at this location was 1 to 10% of References the spallation neutron flux. 1. F. G. Perey, Oak Ridge National Laboratory report ORNL/TM-6062(1971). *From Rcf. !. with modifications by L. R. Greenwood. 2. D. R. Davidson, W. F. Sommer, J. N. Bradbury, R. Argonne National Laboratory. E. Prael, and R. C. Little, Los Alamos National Laboratory document LA-UR-88-33 (1983).

A Study of Defects Produced in Tungsten by 800-MeV Protons Using Field Ion Microscopy New Mexico Inst. of Mining and Technology, Los Alamos STAY'SL Adjustment MCNP/HETC D. J. Farnum andO. T. Inal (New Mexico Inst. of Mining and Technology) and W. F. Sommer (Los Alamos)

Defects produced in tungsten by 800-MeV proton bombardment have been studied on the atomic scale with a field ion microscope.' A fluence measured by 10" radiochemistry of 1022 protons/m2 (~0.1 displace- T S S 4 S 1 Z IO' IO" IO I0 IO 10* 10"' 10° IO IO ments per atom) at a temperature of 300 K produced Neutron Energy (MeV) a measured vacancy concentration of 10~3. No vacancies were observed in the un-irradiated samples. Be- FIGURE cause vacancies are essentially immobile (Uv ~ 1. Spallation neutron spectra. The solid 61 line is based on the experimental activities; the 10" nr/s) at the irradiation temperature of 300 K, it dotted line, on the neutronics calculation. is believed that the observed concentrations are those 122 PROGRESS AT LAUPF—1984

~~FIGURE 1. Photograph of tungsten specimen made with field ion microscope.~~

of the radiation-produced vacancies that did not Further experiments are being conducted, aimed at spontaneously recombine. determining vacancy concentrations resulting from Additionally, a depleted zone was observed con- different fluences. In addition, the observed vacancy sisting of approximately 300 vacancies. One plane of concentration will be compared to that determined this zone is shown in Fig. 1. This "void" volume lies by resistivity measurements. Defect cluster shape along a [121] pole and has an elongated shape. It is and channeling will be evaluated from the field ion postulated that this damaged region was caused by a microscopy results. recoiling tungsten atom after it had undergone an intranuclear cascade following an interaction with an Reference incident proton. This type of defect may be the nucleus for subsequent void growth when the irradia- 1. D. J. Farnum et a!.. Journal of Nuclear Materials 122 tion is carried out in the void-growth temperature and 123, 996-1001(1984). region. BIOMEDICAL RESEARCH AND INSTRUMENTATION 123

Biomedical Research and effectiveness (RBE) of soft x rays is expected to be Instrumentation greater than that for hard x rays in this model, which has met with encouraging success' in describing early experiments.3 The large attenuation coefficients assocated with Radiobiology of Ultrasoft X Rays soft x rays requires great care when we perform M. R. Raju, S. Carpenter, J. Chmielewski, M. Schillaci, and dosimetry measurements. We make these measure- M. Wilder (Los Alamos) ments before and after each series of irradiations using an EG&G extrapolation ionization chamber (a The goal of this program is to elucidate the princi- parallel plate chamber with a cylindrical detector pal physical, chemical, and biological mechanisms of volume that can be varied in size). The window of radiation action in cells. The basic experiments for this detector, which is made of 55-ug/cnr-thick this program involve selected low- and high-energy x- stretched polypropylene coated with 5 nm of ray sources and include studies of cell killing, both evaporated nichrome for electrical conduction, al- with and without modifiers (for example, hypoxia), lows about 82% transmission of the 277-eV C-Ku determination of cellular age response, and measure- x rays. To date we have used C-K(1 (0.28-keV), Al-Ku ment of induced DNA strand breaks, mutations, and (1.5-keV), and Cu-Kn (8.0-keV) x rays to study cell chromosome aberrations. The theoretical effort in- killing (under both toxic and hypoxic conditions) and volves Monte Carlo-based radiation track simulation age response of Chinese hamster V-79 cells, compar- codes to generate energy-deposition events and to ing these results with those obtained with 250-keV- follow the subsequent diffusion of chemical species. peak x rays. Preliminary results of these experiments By combining the experimental and theoretical re- indicate that although the ultrasoft x rays are more sults, we plan to test assumptions used in existing effective in cell killing than are hard x rays, the models and to determine important parameters that variation in radiosensitivity as a function of cell cycle should be included in any model. Ultrasoft x rays is similar. Also, the oxygen-enhancement ratio (less than a few kiloelectron volts) provide a unique (OER) for ultrasoft x rays appears to be less than that tool for studying induced biological lesions because for Cu-Kn x rays. x rays produce photoelectrons with ranges much Although cell-survival curves were published shorter than cellular dimensions but equivalent to previously,3 our OER and age-response results are the size of DNA strands and metaphase new and may have profound implications for models chromosomes. of radiation action. The fact that there is essentially The most significant difference between low- and no difference between ultrasoft and hard x rays in the high-energy x rays is the range of secondary electrons variation of radiosensitivity with cell cycle may in- and, associated with this, the distribution of distances dicate that short electron tracks are of principal im- separating energy-deposition events along the elec- portance. The reduced OER for ultrasoft x rays tron tracks. For example, computer simulations' would be consistent with this interpretation if one show that for C-Ka x rays the energy-weighted dis- supposes that sublesions either must interact with tance distribution extends only to about 10 nm and is other sublesions or must be oxygen-fixed in order to strongly peaked at about 2 nm, whereas for 250-keV- produce lesions. Considering the magnitude of the peak x rays the distribution extends into the micron oxygen effect (OERs of 2 to 3), it would seem that a range and is very broad, peaking in the nanometer mechanism dealing with this effect should be an range. A considerable fraction (approximately one- integral part of any serious model of radiation action. third) of the dose deposited with hard x rays is due to For the near future we shall proceed along the lines nanometer-range electrons. of our present experiments, perhaps including addi- According to one model2 of radiation action, bio- tional x-ray energies and studying the effects of other logical lesions are produced by the interaction of modifiers. On the theory side, additional track calcu- sublesions, which correspond to individual energy- lations will be made for any new energies that are deposition events. Because of the significant dif- introduced, and we shall attempt to model the effects ferences in sublesion separations, the radiobiological of modifiers together with sublesion interactions. 124 PROGRESS ATLAMPF—1984

References further instrumentation development may be necessary to support this expanding program in 1. D. J. Brenner and M. Zaider, Radiation Research 99, 492(1984). Shanghai. The next report on this clincal research is expected late in 1985. 2. A. M. Kellerer and H. H. Rossi, Radiation Research 75,471(1978). Microwave Dosimetry 3. R. Cox, J. Thacker, and D. T. Goodhead, Interna- tional Journal of Radiation Biology 31, 561 (1977); The microwave dosimeters we have developed and D. T. Goodhead, J. Thacker, and R. Cox, Inter- have been tested by the U.S. Air Force and the U.S. national Journal of Radiation Biology^, 101 (1978). Navy, and two private firms have expressed an. interest in manufacturing these devices. The DOE has waived its patent rights on the invention to en- courage rapid commercialization, and transfer of the Instrumentation technology to the private sector is under way. No J. D. Doss (Los Alamos) further DOE-funded research will be performed on this project. A portable instrument, originally de- Ophthalmology signed to interrogate the dosimeter, can be used to read out electrochemical cells on a variety of other The project for modifying corneal shape to im- 1 devices. prove vision has reached the stage of final technology transfer to industry. Radtech, Inc., of Albuquerque, New Mexico, has obtained exclusive licenses on the Computer Modeling two DOE patents for a cornea-shaping probe and is A temperature-calculation code has been de- now developing commercial instruments based on veloped to be used in the hyperthermia program the Los Alamos prototypes. mentioned above. The first version, for predicting equilibrium temperature values in tissue, has already Hyperthermia been used to design a hyperthermia probe for use in a separate project—the treatment of cervical in- Testing of the Los Alamos hyperthermia instru- traepithelial neoplasia at the Truman Medical Center mentation for brain-cancer therapy in China, for- in Kansas City. Another version of the code, which merly limited to the treatment of massive tumor calculates transient temperature response, has been recurrences, has been expanded to include patients used in the Chinese project in the design of electrodes who have not yet had any therapy. These individuals for brain-cancer therapy. Work is under way to first undergo conventional surgical excision, fol- enhance the code by adding the capability to simulate lowed by rf hyperthermia at the margins of the ex- temperature measurement and control the feedback cision. system. This feature, which will enable calculation of Of 14 patients treated in this manner, posttreat- the complex response of tissue-temperature distribu- ment CAT scans show diminishing or stable lesions tion as a function of a variety of system parameters, in 3 cases. Although the small numbers treated and should be useful in a number of medical hyper- the brief follow-up time preclude making any con- thermia applications. clusions, the Chinese neurosurgeons, at Los Alamos during an October 1984 videotape showing of the procedure, stated that they consider these results to Reference be "very promising." 1. J. D. Doss and C. W. McCabe, "Portable Elec- An improved version of the hyperthermia probe trochemical Cell Interrogator," Los Alamos National was developed for treatment of larger volumes, and Laboratory report LA-10274-MS (November 1984). NUCU-AR CHEMISTRY 125

~~Nuclear Chemistry recoiling nuclei by using a combined energy and time-of-flight (TOF) technique.~~

Direct Mass Measurements in the Experimental Method and Results Light Neutron-Rich Region Using a Combined Energy and The experimental setup is shown in Fig. 1. We Ttme-of -Flight Technique used LAMPF's high-intensity 800-MeV proton beam to bombard a thin uranium target (300 to 450 • Experiment 308 — Thin Target Area ug/cm2) that was supported on a backing of pyrolytic 2 Los Alamos, Oregon State Univ., Utah State Univ., carbon (0.6 to 1.1 mg/cm ). Reaction products result- Brookhaven National Lab. ing from the fragmentation of uranium (or the spalla- Spokesman: G. W. Butler (Los Alamos) tion of carbon) were detected in the 45° flight tube of the thin target experimental area. The detection sys- Participants: C. Pillai. D. J. Vieira, G. W. Butler, J. M. tem consisted of (1) two secondary-electron, channd- Wouters, S. H. Rokni. K. Vaziri, andL. P. Remsberg plate (CP), fast-timing detectors7 (~25-ug/cnr Introduction carbon/Formvar foils) located approximately 285 and 468 cm from the target and (2) a gas ionization The most important measurements taken to test counter specially designed for this experiment" to atomic mass models have been those involving a obtain good energy and Z resolution. The counter, concentrated set of measurements that extend far operated with CF4 gas at 35-torr pressure, had a 1 from (J stability. Two excellent examples are the stretched polypropylene isolation window of ~70 isotopic series of mass measurements carried out on ug/cm2 and provided the following energy signals: 2 1 the alkali elements " and the a-decay-chain Q-value AE1, AE2, E, and Ercj. Data acquisition was triggered 17(U78 measurements originating from Hg (Refs. 5 and by a CP1 -CP2-AE1 -AE2-E-E" coincidence. A 6). Both provided extensive sets of new data that total of 17 parameters was recorded with each event, helped to reveal systematic deficiencies in a variety of of which 4 were primary parameters [TOF (CP1- atomic mass models. But extensive as these measure- CP2), AE1, AE2, E] and 13 were secondary ments were, each was limited by what could be parameters. We subsequently used secondary measured (that is, a particular isotopic sequence or a parameters during data analysis to stabilize or to particular decay chain). In the experiment described correct the data and to reject misidentified or unusual here we attempted to further extend mass measure- events. The experiment ran for 4 months, during ment capabilities by developing a more general ap- which time ~ 50-million events were recorded for 60 proach in which a whole array of nuclei that lie far different runs; the integrated beam current on the from stability can be measured simultaneously, inde- target was -4000 C. pendent of both N and Z. We demonstrated that direct mass measurements can be performed for fast- We determined the Z of each event by using a AE2-E or AE2-TOF table-look-up method, after which

~~INCIDENT FAST TIMING GAS IONIZATION BEAM DETECTORS COUNTER~~

~~COLL CP1 CP2 CATHODE~~

~~TOF AE, AE, E E,.,~~

~~WINDOW~~

~~FIGURE 1. Schematic of the experimental layout. 126 PROGRESS ATLAMPF—1984~~

corrections were made for gas-density variations and Figure 3 shows a plot of the difference between the mass dependences. The mass was calculated from the known mass5 and the extracted mass centroid (that is, total energy, TOF, and flight-path distance. The total 8 = massknown — mean) vs the mass number for the energy was determined by summing the energy de- range of nuclei measured in this experiment. We posited in the ion counter (that is, AE1 + AE2 + E) observe a smoothly varying surface of differences and the energy lost in the CP1/CP2 foils and gas- ranging from —0.15 amu for I5O to +0.11 amu for isolation window. The latter energy losses were calcu- 26Ne. These experimental deviations result from the lated using a method for which the AE2-E table difficulty of correctly determining the energy and served as a dE/dx table. The TOF used in the mass TOF on an absolute scale over a broad range of Z, A, determination was that derived from the target-to- and energy. CP2 timing, for which a beam pick-off method was To evaluate how fundamentally limiting these ex- employed." Although the TOF (CP1-CP2) measure- perimental deviations are to this technique, we at- ment had a timing uncertainty of ~ 300 ps, a slightly tempted to fit and extrapolate these deviations as a improved velocity measurement could be obtained function of A or Z. For isotopic sequences, a quad- from target-to-CP2 timing because of its longer flight ratic expression in A described the data well. In path. An effective timing and energy uncertainty of general, isotonic and isobaric sequences did not have 700 ps and 400 keV were obtained, respectively. The as many nuclides as did the isotopic series, and they mass resolution was typically l.O to 1.2% at the were difficult to fit and extrapolate. Instead, the collimator setting, which gave the best mass measure- difference between adjacent isotonic or isobaric ment accuracy per unit time. For all but the highest members was fit as a simple linear function of A. For energy ions, the mass resolution was limited by the each nuclide of interest, all three methods ex- energy resolution. Figure 2 shows the final mass trapolated to the same value within their respective spectra for nitrogen and fluorine. The centroid (more errors. In Table I (column 2), the weighted average of specifically the arithmetic mean) of each mass line the three extrapolated deviations is given for several was determined with a moments analysis approach. neutron-rich light nuclei. Comparing these to the

~~10 = (b) Z = 9 104 11 ,03~~

~~1 I 2 1/ 10 =— II 1\ fl 101 u 1 I 'l III 10 00 14 00 18.00 22.00 15.00 19.00 23.00 27 00 MASS(NITROGEN) UASS(KLUORINE)~~

~~Fic;i HK 2. The mass spectra for (a) nitrogen (Z= 7) and (b) fluorine (Z= 9) isotopes. NUCLEAR CHEMISTRY 127~~

~~p- 1 1 i—r 1 1 1 I~~

~~MASSfcnown - MEAN 1~~

~~t ' N-16 i 0.05 -- N-15 - .1 * • 00Q * 1 N=10 13 -0.05 - N=9 — ':•••' ..••• /' =12 i*=«\ V: •:~~

~~-0.10 _- N=7 N=n \. ' ''••.•' TJW y ••._ .-•' '••-.,.~~

~~/' ^ Z=9 -0.15 _- Z=7 / _ z=a 1 | 1 1 I 1 I 12 14 16 IB 20 22 24 26 28 MASS NUMBER~~

FIGURE 3. The measured mass deviation vs mass number. Isotonic and isotopic members are connected by dashed lines and labeled according to their Not Z. Errors are contained within the size of the data points unless otherwise indicated. known deviations (column 3) gives good agreement bound nuclei produced in fragmentation reaction? in every case. can be measured simultaneously, independent of We determined the masses of several neutron-rich their particular /V or Z. The main disadvantage of this light nuclei by adding the extrapolated deviation to approach is that both the energy and the TOF must the measured mass centroid. These masses are be measured accurately on an absolute scale. Al- quoted as mass excesses in column 4. Although the though small deviations of the mass centroids as a error bars are relatively large (2.6 to 8.0 MeV) for function of N and Z were observed in this experi- these measurements, we found excellent agreement ment, these uncertainties were largely removed by with the known masses (column 5). In all cases errors extrapolation of the smooth dependence observed for were limited by the statistical uncertainty of the mass known nuclei that lie closer to the valley of p stability. line centroid, not by the extrapolation error. We performed mass measurements for several neu- For the first time, the experimental masses of the tron-rich light nuclei ranging from I8C to 2eNe. In all previously unmeasured nuclei, :oN and 24F, were de- cases these measurements agree with the latest mass termined. These agree well with the systematic mass compilation of Wapstra and Audi.5 The masses of MN predictions of Wapstra and Audi.5 and :4F were determined for the first time. A report on this work was presented at the Seventh Summary International Conference on Atomic Masses and Fundamental Constants10 and a separate manuscript In this experiment we have demonstrated that is being prepared for publication.* direct mass measurements can be performed (although they are of low accuracy in this first attempt) by means of a combined energy and TOF method. This research represents the major part of the Ph.D. thesis This technique has the advantage that many particle- work of Chandra Pillai from Oregon State University. 128 PROGRESS AT LAMPF—1984

TABLE I. The Extrapolated Deviation Obtained from the Weighted Average of Three Inde- pendent Extrapolation Methods. These weighted averages (see text) are compared to the measured experimental deviations for several neutron-rich nuclei. The measured mass is determined by the addition of the extrapolated deviation to the determined centroidof each mass line. Masses given in square brackets are systematic predictions taken from Ref. 5. Extrapolated Measured Measured Known" Deviation Deviation Mass Excess Mass Excess A, 8,.x, (amu) 80bs (amu) (MeV) (MeV)

I7C -0.0107 (±0.0030) -0.0118 (±0.0044) 20.0 (±4.9) 21.025 (±0.035) I8C 0.0187 (±0.0041) 0.0211 (±0.0076) 22.7 (±8.0) 24.890 (±0.150) I9N -0.0046 (±0.0020) -0.0029 (±0.0026) 14.3 (±3.0) 15.867 (±0.047) MN 0.0288 (±0.0«33) 21.9 (±5.7) 122.10) -- 21O 0.0267 (±0.0018) 0.0261 (±0.0028) 8.7 (±3.1) 8.127 (±0.052) 22O 0.0634 (±0.0033) 0.0632 (±0.0059) 9.7 (±6.3) 9.443 (±0.087)

»F 0.0609 (±0.0023) 0.0597 (±0.0024) 4.5 (±3.1) 3.354 (±0.170) 0.1018 (±0.0027) — 8.3 (±4.5) [8.751 — 25Ne 0.0734 (±0.0020) 0.0735 (±0.0034) -2.2 (±3.6) -2.156 (±0.091) 26Ne 0.1114 (±0.0023) 0.1122 (±0.0054) -0.4 (±5.5) -0.440 (±0.072) "Reference S.

References 4. M. Epherre, G. Audi, C. Thibault, R. Klapisch, G. Huber, F. Touchard, and H. Wollnik, "Direct Mass 1. P. E. Haustein, "A Comprehensive and Critical Review of the Predictive Properties of the Various Measurements on Francium Isotopes and Deduced Mass Models." Proceedings of the Seventh Interna- Masses for Odd-Z Neighboring Elements," Nuclear tional Conference on Atomic Masses and Funda- Physics A34Q, 1-12(1980). mental Constants, Seeheim, West Germany, Sep- 5. A. H. Wapstra and G. Audi, "The 1983 Atomic tember 3-7, 1984 (Plenum Press, New York), in Mass Evaluation, Parts I-IV " (to be published in press. Nuclear Physics A). 2. C. Thibault, R. Klapisch, C. Rigaud, A. M. 6. U. J. Schrewe, E. Hagberg, H. Schmeing, J. C. Poskanzer, R. Prieels, L. Lessard, and W. Reisdorf, Hardy, V. T. Koslowsky, K. S. Sharma, and E. T. H. "Direct Measurement of the Masses of "Li and Clifford, "Decay Studies of the New Isotopes 26'3:Na with an On-Line Mass Spectrometer," Physi- l6-l63Hf," Physical ReiiewC 25, 3091-3103(1982). cal Review C12, 644-657 (1975). 7. A. M. Zebelman, W. G. Meyer, K. Halbach, A. M. 3. M. Epherre, G. Audi, C. Thibault, R. Klapisch, G. Poskanzer, R. G. Sextro, G. Gabor, and D. A. Huber, F. Touchard, and H. Wollnik, "Direct Landis, "A Time-Zero Detector Utilizing Measurements of the Masses of Rubidium and Isochronous Transport of Secondary Electrons," Cesium Isotopes Far from Stability," Physical Re- Nuclear Instruments & Methods 141, 439-447 view C19, 1504-1522(1979). (1977). NUCLEAR CHEMISTRY 129

8. C. Pillai, J. M. Wouters, D. J. Vieira, G. W. Butler, stants, East Lansing, Michigan, September 18-21, H. Sann, A. M. Poskanzer, A. Olmi, and K. v aziri, 1979, J. A. Nolen and W. Benenspn, Eds. (Plenum "Development, of a fGas Ionization Detector for Press, New York, 1980), pp. 69-75. Direct Mass Measurements at LAMPF," in the "Isotope and Nuclear Chemistry Division Annual 10. C. Pillai, D. J. Vieira, G. W. Butler, J. M. Wouters, Report FY 1983," Los Alamos National Laboratory S. H. Rokni, K. Vaziri, and L. P. Remsberg, "Direct report LA-10I30-PR (May 1984), pp. 200-204. Mass Measurements in the Light Neutron-Rich Re- gion Using a Combined Energy and TOF Tech- 9. D. J. Vieira. G. W. Butler, D. G. Perry, A. M. nique," Proceedings of the Seventh International Poskanzer, L. P. Remsberg, and J. B. Natowitz, Conference on Atomic Masses and Fundamental "Search for Light Neutron-Deficient Nuclei Constants, Seeheim, West Germany, Septem- Produced in 800-MeV Proton Spallation Reac- ber 3-7, 1984 (Plenum Press, New York), in press, tions," Proceedings of the Sixth International Con- Los Alamos National Laboratory document LA- ference on Atomic Masses and Fundamental Con- UR-84-2960 (September 1984).

Masses of Ground-State Baryons cal framework of the Friedberg-Lee nontopological Calculated with a soliton model.1 Nontopological Soliton Model The Friedberg-Lee model was first applied to the modeling of nucleons and deltas by Wilets et al.2 It was extended by Shakin et al.,1 who used a simplified R. S. Bhalerao* ./. Kunz,** Q. Haider, andL. C. Liu (Los Alamos) interaction to study mesons. However, neither of these groups has considered the hadrons involving Although quantum chromodynamics (QCD) is be- the strange quark or strange antiquark, nor have they lieved to be the correct theory for strong interactions, calculated one-gluon corrections. Our work has in- exact calculations based on this theory remain im- cluded 5 quarks so that we can study all ground-state practical even for a single hadron, not to mention for baryons. Also, we have calculated perturbatively nuclei. For this reason, many phenomenological color-electric and color-magnetic effects resulting models have been proposed to approximate QCD. from one-gluon exchange. The calculated masses, Here, we report our results of calculations of the magnetic moments, and charge radii are compared static properties of the ground-state octet Jp = (1/2)+ with available experimental data in Table I. The and decuplet J'' = (3/2)+ baryons within the theoreti- ratios gjgt- (not shown in Table I) were also calculated and will be given in a future report. As this work continues, our main efforts are "Currently at the Tata Institute of Fundamental Research. directed toward calculating one-gluon-exchange ef- Bombay, India. fects nonperturbatively, to include center-of-mass ""Currently at the University of Giessen. Federal Republic of Germany. corrections and to incorporate chiral invariance into the model. We also expect to examine the predictive power of this model for KN and AW interactions before it is applied to nuclear physics. 130 PROGRESS ATLAUPF—1984

~~TABLE I. Ground-State Properties of the Baryons Calculated with the Nontopological Soliton Model. Magnetic 2 J Masses (MeV) Moments (nm) lh(fm )~~

~~Particle AM£ Total Experiment Theory Experiment Theory~~

~~938.28 2.53 2.79 0.69 P 1090.56 -151.20 0.00 939.36 n 939.57 -1.68 -1.91 0.00~~

~~£+ 1189.36 2.49 2.38 0.77 £° 1249.03 -92.57 3.42 1159.88 1192.46 0.76 0.10 ir 1197.34 -0.98 -1.10 -0.58~~

~~A° 12^.03 -153.82 3.48 1098.69 1115.60 -0.53 -0.61 -0.10~~

~~1321.32 -0.42 -1.85 -0.51 1470.29 -158,29 4.07 1356.07 —0 1314.90 -f.30 -1.25 0.17~~

~~A++ 1230.87 1.68 1.34 A+ 1232.38 0.84 0.69 1090.56 145.76 0.00 1236.32 A° 1233.30 0.00 0.00 I i j ! A" -2.53 ! i -0.62~~

~~£•+ 1382.30 0.98 0.77 E*o 1249.03 119.75 3.27 1372.05 1382.00 0.11 - — 0.10 E*- 1387.40 -0.76 -0.58~~

~~1535.00 -0.65 — -0.51 1470.29 97.38 3.92 1571.59 1531.80 0.23 0.17~~

~~sr 1710.58 81.83 0.00 1792.41 1672.45 -1.63 — -0.43~~

"The parameters used are Mu = Md = 0, Ms = 350 MeV, n, = /2/4n = 2.9, ?, = 16.7, a = 236.1 fnT2, b = -11 613.0 fm"1, and c - 180 000. Here, Mq (q = u, d, s) stands for the bare quark mass, and g and /are, respectively, the quark-d and gluon-o Field-coupling constants. The quantities a, b, and c determine the potential of the scalar a Field (Refs. 1 and 2).

~~References~~

1. R. Friedberg and T. D. Lee, Physical Review D 15, 3. L. S. Celenza, C. M. Shakin, and R. B. Thayyullathil, 1694 (1977); and T. D. Lee, Physical Review D 19, "Covariant Description of Mesons as Non- 1802(1979). topologica! Solitons." Brooklyn College preprint 2. R. Goldflam and L. Wilets. Physical Review D 25, BCINT 84/091/129. 1951(1982). NUCLEAR CHEMISTRY 131

~~Distorted-Wave Impulse Approximation 0.3 Predictions for Pionic n Production I5il MeV 3 3 He(rr,n) H 0.2 L.C. Liu (Los Alamos)~~

As the energy of a pion incident on a nucleus O.I increases, various production channels become important in TTJV collisions. Consequently, at LAMPFII O energies pion-induced production will play impor- /s « 1542 MeV tant roles in pion-nucleus dynamics. The lowest ifi genuine two-body-reaction threshold is given by the 0.3 - reaction n~p —- T\n at TK =* 551 MeV (or \fs~ = 1488 MeV). The total reproduction cross section rises rapidly with pion energy and reaches a maximum of ~2.5 mb at Tn = 661 MeV (or j/T = 1550 MeV) (Ref. 1). In the energy region 7; = 0.6-1.0 GeV, the KN —* r\N reaction is the second most important nN inelastic channel—second only to pion-induced single-pion production. 0 In the SU(6) model, T| differs from rc° by having an « 1572 MeV additional 55 quark-antiquark pair in its wave function. The systematics of rjiVand K°N scattering could 0.2 yield information on the role of this 55 pair in meson- baryon interactions. As for (y,x\) and other modes of nuclear n. production, (7t,T]) reactions will allow us to O.I study r\N scattering. Because hadronic and electromagnetic reproduction processes are different, the details of x\N scattering extracted from different types -1.0 -0.6 -0.2 0.2 0.6 1.0 of nuclear reactions will complement one another. For simple kinematic reasons, the threshold for cos 9* nuclear (K,T|) reactions is much lower than for Tn = 551 MeV. For example, in nuclei with mass number FIGURE 1. Differential cross sections for n~p —* r\n A = V the kinematic reproduction threshold is T^ = vs the cosine of the production angle in the center- 460 MeV. In an ongoing LAMPF experiment,2 pions of-mass frame. Solid and dashed curves are ob- of energies T =* 500-550 MeV are being used. In this tained with off-shell-model parameters based on K nN phase shifts of Arndt* and Ref. 5, respectively. low-energy region, the basic nN-* r\N process is most likely to occur subthreshold. Existing theoretical models3 for the itJV—«• t\N amplitude are based either which reactions proceed by the formation of N* on a /^-matrix approach or on a Breit-Wigner type isobars. The model also takes into account the effects parameterization. These models do not contain form of the pion-production (nN— nnN) channel on these factors to allow a meaningful off-shell extrapolation amplitudes. The parameters of the model were de- of the amplitude for calculating (7t,T|) processes in a termined from KN phase shifts alone. The differential nucleus. They also cannot provide an r\N elastic- n'p — x\n cross sections predicted by the model are scattering amplitude, a quantity indispensable for compared with data in Fig. 1. The model also predicts calculating the final-state interaction in A(n,r\)B reac- an attractive 5-wave r\N interaction. tions. Recently, we have developed an off-shell model 4 *Rcfcrcncc 5. and information on Phase-Shift Solution FP84 (OSM) for nN—* n.jV and r\N-* i\N amplitudes. It is from R. A. Arndt. Virginia Polytechnic Institute and Stale a coupled-channel, separable-interaction model in University. August 1984. 132 PROGRESS AT WMPF—1984

~~0 60 120 IBO 0 30 60 90 120 160 30 100 i 1 1 1 I: : 1 1 1 : 3 3 Hefy,7?) H(g.s.)~~

~~Pu : cr = 7. ^b - a=3l.8/xb 10 cr -7.7 fib ^ 1 \~~

~~in \ Xs~~

~~- \ / • "° 0.1 \~~

~~- • \ - - \V'\ // 0.01 — V (a) ~~~

~~i 0.25 0.45 0.65 0.25 0.45 0.65 0.85 q(GeWc) q(GeV/c)~~

FIGI-RE 2. Differential cross sections for 'HeCn^^H (g.s.) for (a) at ftnlllb = 620 MeV/c and (b) at Av.iai, — 680 MeV/c. Dot-dashed curves are obtained with off-shell-model parameters based on the uV phase shifts of Ref. 5 and Arndt. Similarly, Ref. 6 was used for solid curves.

In Fig. 2(a) and (b) we present theoretical differen- distortions of the incoming pion and outgoing r\. The tial cross sections for the reaction 3He(7c~,n)3H ground nuclear wave function of 3He was derived from its 5 state (g.s.) at ^lab = 620 and 680 MeV/c, as predicted charge density, and corrections were made for the by our OSM using the amplitudes of Ref. 4. These finite size of the proton and the nuclear center-of- incident pion momenta correspond, respectively, to mass effects. The solid and dashed curves in Fig. 2(a) the lower and upper pion energies used in current and (b) were obtained through the use of the OSM experimental investigations.2 The calculations are parameters that were derived, respectively, from based on the distorted-wave impulse approximation CERN theoretical and Virginia Polytechnic Institute (DVVIA)—that is, on a one-nucleon n-production and State University KN phase shifts.4' The calcu- mechanism. We neglected the Fermi motion of the lated cross sections include both spin-flip and non- target nucleons but took into account nuclear binding spin-flip contributions. However, at these low effects on the basic KN — niV process and on the energies the spin-flip contributions are negligibly NUCLEAR CHEMISTRY 133 small. An inspection of the curves in Fig. 2(a) and (b) lead to the identification of important new physics, reveals the following interesting features: such as multinucleon ^-production processes, modi- 1. The minima of the cross sections always occur fication of A* resonances by a nuclear medium, and at a momentum transfer of — 560 MeV/c. This the dynamics of n. propagation inside a nucleus. indicates the diffractive feature of i] production that leads to the isobaric-analog nuclear state. References 2. Because of the kinematics of the (rc,rt) reaction, the range of momentum transfer accessible in 1. R. M. Drown et al., Nuclear Physics B153, 89 (1979) an experimental measurement depends on the and references therein. incident pion energy. This requires us to com- 2. J. C. Peng et al., LAMPF Experiment No. 852. pare differential cross sections at different 3. B. Carreras and A. Donnachie, Nuclear Physics B16, energies for the same momentum transfer. We 35 (1970) and references therein; P. N. Dobson, note that although the integrated cross section Physical Review 146, 1022 (1966); and S. F. Tuan, increases by a factor of—4, from ~8 ub at kM Physical Review 139, B1393 (1965). = 620 MeV/c to -32 ub at k = 680 MeV/c, uMb 4. R. S. Bhalerao and L. C. Liu, "An Off-Shell Model the differential cross section at any given for Threshold Pionic n, Production on a Nucleon and momentum transfer increases only by a factor for r|NiScattering," Los Alamos National Laboratcy of ~2. We conclude that about half of the document LA-UR-84-3384 (to be published in Physi- increase of the integrated production cross sec- cal Review Letters). tion is of kinematic origin. 5. D. J. Herndon et al., "nN Partial-Wave Amplitudes," 3. The OSM parameters based on the nN phase Lawrence Berkeley Laboratory report UCRL-2OO3O shifts lead to similar reproduction cross sec- (February 1970). tions (within 20%) for momentum transfers <0.5 GeV/c, but the discrepancy increases with 6. H. R. (ollard, L. R. B. Elton, and R. Hofstadter, the momentum transfer and reaches ~ 200% at "Nuclesr Radii," Landolt-Bornstein New Series, q = 0.8 GeV/c. Group i. Vol. 2, H. Schopper, Ed (Springer-Verlag, 4. Because the OSM parameters based on these Berlin-Heidelberg-New York, 1967), p. 32. two sets of nN phase shifts give n~p —> r\n cross sections equal to each other within a few per cent for q < 0.75 GeV/c (Fig. I) but lead to x\N- ProductiG n of Long-Lived Cosmogenic scattering phase shifts that differ from each Nuclides with High-Energy Beam-Stop other by about 50% (Ref. 4), we may interpret Neutrons this noted 1He(n:~,Ti)1H cross-section difference • Experim«nt691 — BSA-RAD at large momentum transfers as arising from different final-state r\N interactions. If this as- Los Alamos, Univ. of Cologne, Univ. of California at San sumption can be verified by other modes of Diego pion-nucleus n, production, the (7t,r|) reaction Spokesman: R, C. Reedy (Los Alamos) indeed provides a very promising avenue for Participants: P. Englert, S. Theis, andJ. R. Arnold studying r)-nucleon interactions. In conclusion, we believe that the results reported Considerable interest exists in simulation experi- here carry the most basic features of DWIA predic- ments fpr investigating cosmic-ray interaction with tions for (rc,r|) reactions leading to the isobaric-analog condensed matter in space. Residual stable and nucleus. It is our hope that experimental cross sec- radioactive nuclei ofspallation reactions carry useful 3 3 tions for He(7t~,n.) H (g.s.) reactions, which will soon time information about the histories of the cosmic be made available at LAMPF, will show some signifi- rays and of the targets (earth, moon, and meteorites).' cant deviations from the present DWIA prediction. In the past, most simulation experiments made use of We believe that understanding the discrepancies be- only instrumental detection methods for the induced tween DWIA predictions and experimental data will activities of short-lived isotopes produced from 134 PROGRESS AT LAMPF—1984

spallation.2"4 In meteorites or lunar samples, how- mm) or placed in boron nitride containers (wall ever, only a few short-lived isotopes have been thickness of 6 mm) to cut down the low-energy measured.56 The majority of accessible radioactive neutron flux in the samples—that is, to reduce the spallation products from galactic cosmic-ray (GCR) buildup of neutron-capture products, which were of interactions with these bodies710 are long-lived no importance for this experiment. Samples were isotopes such as 10Be, 26A1, 53Mn, and I29I, whose de- placed at different locations (approximately 20 cm tection requires radiochemical separation and special apart from each other) in an REF rtringer at the counting techniques. LAMPF beam-stop area and were irrauiated between The crucial problem in all of these experiments is 3 and 5 days. the simulation of the isotopic irradiation by and the After irradiation the monitor foil packages of each continuous energy distribution of incident particles production stack were removed and the individual in outer space, whereas the accelerators used provide foils were unwrapped and counted using solid-state monoenergetic charged particles. In addition, the gamma-ray spectrometers with automatic sample major component of the secondary cascade particles changers. Up to four counting cycles for interference in an extended extraterrestrial object are evaporation and half-life control were made. After careful surface and spallation neutrons." The Radiation-Effects Fa- etching, radiochemical separation of the long-lived cility (REF) stringers of LAMPF provide irradiation nuclides from the production targets was carried out, positions where samples can be exposed to high followed by measurements of the respective nuclei by fluxes of spallation neutrons of different energy spec- low-level gamma- and x-ray spectroscopy and tra, depending on the irradiation location, the dis- gamma-gamma coincidence techniques.13 placement from the beam line, and the targets in Saturation activities for monitor and production front of the A-6 beam stop. For a useful interpreta- foils were calculated from the disintegration rate at tion of the nuclide production in these irradiation the end of the irradiation with corrections for chemi- locations, knowledge about the neutron fluxes and cal yields (wherever radiochemistry was applied), energy spectra is needed. isotopic abundance, and neutron and gamma-ray self-shielding (where necessary). The beam history during the 3- to 5-day irradiations did not require Experimental Method corrections for nuclides with half-lives greater than A series of irradiations was performed at the REF about 3 days. in the LAMPF beam-stop area. Stacks of cos- mochemicaliy important target elements were exposed to high-energy neutrons. These stacks con- Results sisted of two components: (1) the production foils (0.5 to 1.0 g) for the long-lived spallation isotopes and Figure 1 illustrates the wide range of irradiation (2) the monitor foils (2 ug to 5 mg) for the short-lived conditions for the production of spallation nuclides isotopes and the intended dosimetry. The element in cobalt as a function of the neutron reaction Q sets for both components were identical: magnesium, value. These six foil packages were irradiated in aluminum, silicon, calcium, tantalum, manganese, different locations during the same run. The absolute iron, cobalt, nickel, copper, tellurium, barium, and residual nuclide yields reflect the variation of the lanthanum; the monitor component also contained integral neutron fluxes of the sample locations. The tungsten, lutetium, and gold [the last two of which position of package 2001 was directly underneath the have (n,xn) cross sections measured12 up to 28 MeV]. beam line whereas the position of 2006 was 50 cm Elements up to nickel are of cosmochemical re- away from 2001. As one can see, 2006 was exposed to levance for the production of radionuclides such as a significantly lower integral neutron flux than 2001. 10Be, 22Na, 26A1,44Ti, "Mn, 54Mn, and 59Ni. Elements In addition, the differences among the production with higher masses are targets for ]29l production. rates of radionuclides at positions 2001, 2005, and The individual foils were wrapped in high-purity 2006 increase with increasing Q values. This in- aluminum foil where necessary. The stacks were dicates differences in the energy distribution of neu- usually surrounded by cadmium (wall thickness of 2 trons at the respective positions, with the fluxes of NUCLEAR CHEMISTRY 135

10' neutron energies above the last measurement 59Co(n.x) (usually 20 to 28 MeV), the cross sections were estimated from nuclear systematics or theoretical calculations.12 For higher energies, measured cross 2001.2002 O 2003,2004 0 sections for the corresponding proton-induced reac- 13- « 10 2005 A tions were used. We included only reactions for 2006 0 which most of the production took place at energies where there were reasonably well-known cross sec- o o tions. The fluxes of high-energy particles were esti- 48 12 - mated mainly from the production of both V and 10 46Sc from iron. The use together of two radionuclides o that are on opposite sides of the valley of stability o 96 a 8. o 1 should reduce any possible effects of differences in B O & a the proton-induced cross sections relative to the neu- 1 S tron-induced cross sections for the same target-prod- < IO' - •> 8 CO * 9 uct pair. A The spectrum of particles in each foil package was (0 estimated by calculating the radionuclide production rates expected for a number of different spectra and 10 10 -10 -50 -100 -150 iterating the input spectra to give the best fit with the Reaction Q values measured activities in the monitor foils. The spectra that gave the best fits were similar to those used to calculate production rates of cosmogenic nuclides FIGURE 1. Atoms of various radionuclides produced from cobalt at six positions near the fairly deep in the moon." Several monitor reactions LAMPF beam stop. Products made by reactions were not used, as they gave results that were signifi- with high threshold energies are made in smaller cantly different from those for similar reactions on yields than those with lower thresholds, and the other target foils. For most foil packages, about 12 range of yields is larger for high-energy reactions reactions were used to estimate the particle spectrum than for those induced at low energies. Figure 2 shows the relative neutron energy spectra estimated for the extreme locations of 2001 and 2006 and for position 2005. For the highest energies, there high-energy neutrons reduced more, relative to those are probably significant fluxes of protons along with of low-energy neutrons, with increasing distance the neutrons. Figure 2 also shows that the normalized from the beam line. Similar results have been ob- flux spectra differ by half of a decade in the high- tained for radionuclide production in other elemental energy region for the location directly underneath the foils, such as iron, titanium, silicon, aluminum, and beam line compared to those farther out. Thus pack- magnesium. age 2001 experienced both a higher neutron flux and In the gold and lutetium monitor foils, production a significantly harder spectrum than 2006. Better rates of the l97Au(/7,3«) product l95Au and of the determinations of the neutron fluxes and energy spec- 175Lu(n,7/7) product IMLu could be obtained. To tra are in progress. The neutron/proton ratio in both characterize the neutron energy spectra in the irradia- irradiation positions for the low-energy region (<50 tion locations, activities from these (n,xn) reactions MeV) could be shown to be n/p > 100 by means of and from other selected neutron-induced reactions very low or undetected products from (p,xn) reac- such as Co(«..Yn), 27Al(«,a)24Na, Ti(n,p.vn), Ni(H,p.v«), tions.15 and Fe(«,.v) were included in the deconvolution of Table I summarizes the production rates of the the spectra. The excitation functions (cross sections longer lived species determined after radiochemical as a function of energy) for these monitor reactions separation. The production rates of the long-lived were evaluated from many measurements reported isotopes follow the trends for different neutron fluxes in the literature, similar to that done in Ref. 14. For and energy spectra established from the shorter lived 136 PROGRESS AT LAMPF—1984

~~Differential Neutron Fluxes in LAMPF Beam Stop Experiments~~

r—. 10"' 'in '§ c FIGURE 2. The differential fluxes of particles (mainly neutrons, especially at low energies) determined from activations in three packages of elemental foils near the LAMPF beam stop. Pack- age 2001 was the closest to the beam; package 1 2006 was about SO cm farther away. 2001 10"3

~~2005~~

~~5 2006~~

~~150 300 450 600 750 Neutron Energy [MeV]~~

~~TABLE I. Production of Selected Radionuclides in Various Target Elements Near the LAMPF Beam Stop for Three Foil Packages. Foil Packages (atoms g ') Target Product 2001 200S 2006~~

~~Aluminum 26A1 1.3 X1014 6.4 X 1013 4.1 X1013 22Na 3.2 X1013 1.7 X 10" 8.8 X1012 7Be 1.2 X1012 6.7 X 10" 3.8X10"~~

~~Titanium 44T| 1.6 X1012 1.2 X1012 5.2 X 10" 22Na 1.2X10" 4.9 X 1010 7Be 1.8X10" 5.5 X 1010~~

~~Iron "Co 2.0 X 1012 1.4 X1012 5.3X10" 22Na 3.2 X 1010 2.5 X1010 7Be 2.0X10" 1.4X10"~~

~~Cobalt 60Co 4.4 X 1015 1.7 X 10" 2.1 X 10" 58Co 3.0 X1014 1.8 X1014 1.0 X1014 57Co 1.0X10" 5.7 X1013 3.9 X1012 56Co 1.6 X1013 8.3 X 1012~~

Nickel 59Fe 9.7X10" 5.9 X 10" 3.5 X 10" 48y 8.4 X 1012 3.6 X 10n 1.8 X 1012 22 Na 2.6 X1012 1.8 X1010 6.5 X109 NUCLEAR CHEMISTRY 137 monitor isotopes. High-energy particles, monitored restrial matter, the spectra estimated for the various by reactions such as those making ~Na from nickel or foil packages were used to calculate expected ac- 7Be from aluminum, exhibit a steady decrease with tivities, which were then compared with the increasing distance from the beam line, whereas measured activities. For example, the activities 54 thermal and epithermal neutron fluxes derived from measured for Mn from iron foils near the beam stop the 59Co(«,y )60Co reaction still increase at 50 cm off were higher by about 40% than those calculated with the beam line (position 2006). the estimated fluxes and with measured cross sec- S4 54 Table II compares production ratios from sample tions for the Fe(H,/9) Mn reaction and for the 56 54 locations 1112 (similar to 2001) and 1113 (similar to Fe(p,«2p) Mn reaction. A similar discrepancy be- 2006) with those obtained in the iron meteorite tween observed and calculated activities exists for 53 9 Aroos and the stony meteorite Bruderheim. All re- Mn in extraterrestrial samples. " This disagree- sults for the simulation experiments are normalized ment between the measured activities and those cal- to the chemical composition of the meteorites. For culated using cross sections for proton-induced reac- Aroos only iron and nickel had to be considered. The tions is probably caused by significant differences in 54Mn/"Na ratios in our beam stop foils are much the cross sections for neutron-induced reactions com- higher than those in Aroos, indicating that particles pared to the corresponding proton-induced reactions. l0 7 with energies above several hundred million electron Recent measurements for Be in a meteorite imply volts were relatively more abundant in this iron that high-energy (100- to 1000-MeV) neutrons can l0 meteorite. This was expected, as primary particles of produce Be much better than protons with similar E > 1 GeV are present in cosmic rays. In general, the energies. Preliminary results from the LAMPF ir- conditions at the LAMPF beam stop seem to be radiations indicate that, for reactions with 7 suitable to simulate irradiation conditions very deep aluminum, neutrons make "Na and Be with lower in the lunar surface or in meteorites. For the produc- cross sections than do protons. In continuing this tion of nuclides produced by spallation with reaction study of the production of nuclides by high-energy thresholds :=50 MeV (such as for 26A1 and S3Mn), neutrons, we want to better determine the neutron production ratios from the meteorites and the simu- spectra and to study more reactions, including those lation experiments are similar, illustrating the role making cosmochemically important products such as 2(> 10 secondary neutrons play in the production of cos- A1 and Be. Irradiation positions with wide ranges mogenic radionuclides in extraterrestrial matter. of neutron spectra will help to determine excitation functions at high energies for a number of neutron- To test the cross sections that had been estimated induced reactions. or used" for several reactions important in extrater-

TABLE II: Comparison of Production Ratios of Cosmogenic Radionuclides in the Aroos and Bruderheim Meteorites and in this Simulation Experiment. Monitor Foils" Monitor Foils" Production Ratio Aroos 1112 1113 Bruderheini 1112 1113

~~54Mn/nNa 131 859 2200 1.1 54Mn/46Sc 16 27 48 16 27 43 54Mn/48V 5.2 9 15 2.9 9.3 16 54Mn/51Cr 1.8 2.2 2.9 0.9 2.3 3.1 54Mn/5~~

Conclusions 5. K. Marti, J. P. Shedlovsky, R. M. Lindstrom, J. R. Arnold, and N. G. Bhandari, in Meteorite Research, It has been shown that LAMPF beam-stop irradia- P. M. Millman, Ed. (R. Reidel Publishing Co., tion facilities provide neutron energy spectra that, Dordrecht, 1969), p. 246. with some restrictions, can be used to simulate the 6. M. Honda, K. Horie, M. Imamura, K. Nishiizumi, complex radiation environment on planetary sur- N. Takaoka, andK. Komura, Geochemical Journal faces or meteorites exposed to cosmic radiation. Neu- 14,83(1980). tron energy spectra were determined for each irradiation stack by multiple foil activation. The high fluxes 7. C. Tuniz, C. M. Smith, R. K. Moniot, T. H. Kruse, W. Savin, D. K. Pal, G. F. Herzog, and R. C. Reedy, of spallation neutrons were advantageous for the Geochimica Cosmochimica Acta 48, 1867 (1984). production of detectable amounts of long-lived species. Excitation functions for nuclear reactions in- 8. J. Thomas, P. Parker, G. F. Herzog, and D. Pal, duced by high-energy neutrons will be useful for Nuclear Instruments & Methods 211,511(1983). studies of particle spectra near thick targets irradiated 9. P. Englert and W Herr, Earth and Planetary Science by high-energy particles14 and of cosmogenic nuclides Letters 47, 361(1980). 1 in extraterrestrial matter. " 10. D. Elmore, H. E. Gove, R. Ferraro, L. R. Kilius, W. H. Lee, K. H. Chang, R. P. Beukens, A. E. Litherland, C. J. Russo, K. H. Pruser, M. T. Mur- Acknowledgment rell, and R. C. Finkel, Nature 286, 138(1980). We wish to thank Bob Brown for providing ir- 11. R. C. Reedy and J. R. Arnold, Journal of radiation facilities, Bruce Dropesky for laboratory Geophysical Research 77, 537 (1972). support, and health physics personnel (Group 12. B. P. Bayhursi, J. S. Gilmore, R. J. Prestwood, B. J. HSE-11) for their assistance. Wilhelmy, N. Jarmie, B. H. Erkkila, and R. A. Hardekopf, Physical Review C 12,451 (1975). References 13. S. Theis and P. Englen, "Production Rates of Long- 1. R. C. Reedy, J. R. Arnold, and D. Lai, Annual Lived Radionuclides in Artificially Irradiated High- Review of Nuclear and Particle Science 33, 505 Purity Targets: Application of Radiochemical Tech- (1983). niques to Simulation Experiments" (submitted to Radiochimica Acta). 2. M. Honda, Journal of Geophysical Research 67, 4847(1962). 14. R. D. Davidson, L. R. Greenwood, R. C. Reedy, and W. F. Sommer, in the Proceedings of the 12th 3. A. K. Lavrukhina, G. K. Ustinova, V. V. Malyshev, International Symposium on Effects of Radiation and L. M. Satarova, Atomic Energy 34, 23 (1973). on Material, in press. 4. R. Michel, H. Weigel, H. Kulus, and W. Herr, 15. H. Weigel, R. Michel, U. Herpers, and W. Herr, Radiochimica Acta 21, 169 (1974). Radiochimica Acta 21, 179(1974). RADIOISOTOPE PRODUCTION 139

Radioisotope Production ion-exchange systems were used to purify the eluent fractions, including ion exchange for cations in nitric acid to purify 46Sc, cation exchange in hydrochloric 7 Isotope Production and Separation acid—acetone to purify Be, and ion exchange with macroreticular resin in hydrochloric acid to purify 48 34 Group INC-3 Radioisotope-Production Activities V and Mn. The following table shows amounts of in FY 1984 products obtained in pure usable solutions (81 091 K. E. Peterson. M. A. On. F. //. Sewer, N../. Scgura, IV. A. mA-h in beam, 165 h in beam at end of Taylor, J. H'. Barnes, F. J. Steinkruger. K. E. Thomas, beam—275.3125). and P.M. Wanek A significant portion of the efforts of Group INC-3 Activity Recovered is tied to the production and supply of radioisotopes Activity at Calculated to for the medical research community. These rudio- End of Beam End of Beam Recovery isotopes are generally unavailable commercially or Isotope (mCi) (mCi) (%) can only be made in high yields at Los Alamos. Group INC-3 supplies these radioisotopes on a cost- 7Be 810 540 67 recovery basis to interested researchers. During FY 48y 2173 676 31 46 1984, 107 targets were irradiated at LAMPF. A sum- Sc 241 62 26 54Mn 278 4 mary of these targets is given in Table I. 2 A total of 49.66 Ci of 18 radioisotopes was shipped to 39 organizations around the world and to 5 groups at Los Alamos. These shipments are summarized in New Stringer and Targeting System at LAMPF for Table II. '"Xe —* '"I Production and Recovery

Isotope Separations from a ZnO Target M. A. Ott../. W. Banes. F. H. Seurer, N. J. Segura. W. A. Taylor. H. A. O'Brien, andD. C. Moody K. E. Thomas. A'. J. Seguru. and./. II'. Barnes Interest within the radiopharmaceutical com- Often, a major disadvantage to spallation produc- ini munity in obtaining high-purity I is rising, primar- tion of radioisotopes is the generation of multiple ily because of the development of radioiodinated radionuclide products, thereby requiring extensive agents that show promise in diagnosing cerebral separation procedures to obtain the desired product vascular defects (stroke). Previously, we reported in a pure state. This multiple radionuclide produc- results obtained from spallation reactions in CsCl tion, however, can eliminate the need to irradiate targets operated in the batch mode, where the yield of separate targets for each isotope desired. 123 I was in the range from 1 to 2 Ci at the end-of- A chemical separation procedure was developed to I2S 7 46 54 growth period. The amount of contaminating I, recover Be, Sc, and Mn from Zn-H:SO4 solutions however, was too high for many applications. obtained by irradiating zinc oxide in the proton beam Higher i:jI yields and reduced I251 contamination at LAMPF. The primary isotope of interest from this are possible with a system in which the radioxenon target is h7Cu; however, significant quantities of the parents can be swept from the in-beam target con- other three radionuclides also are present. The ZnO tinuously during irradiation and collected in an ap- was dissolved in sulfuric acid and an electroplating propriate growth chamber. At the end of irradiation, procedure was used to remove several curies of 67Cu. the growth chamber is detached and transported to a An extraction procedure using 2,4-pentanedione and vacuum line in the hot cell and the residual radio- back-extracting with 4 M of hydrochloric acid xenon is removed, leaving behind pure 123I. separates the isotopes of interest from the remaining During the past year at the LAMPF Isotope Pro- Zn-H SO solution. Cation exchange in a 2 4 duction Facility, a new isotope stringer with gas- hydrochloric acid—acetone solution is used to sweeping lines was installed and a gas-collection sta- separate the specific isotopes and to collect them in tion was constructed and installed. various fractions of the eluent in sequence. Several 140 PROGRESS AT LAMPF—1984

~~TABLE I. Medical Radioisotope Shipments — FY 1984.~~

~~Number of Amount Isotope Institution Shipments (mCi)~~

~~105Ag Los Alamos/Group INC-3 0.63 TOTAL 1 0.63~~

~~26 Al Atomic Energy of Canada, Ltd. 1 0.00002 California Institute of Technology 1 0.00038 Fisheries and Oceans Freshwater Institute 1 0.00003 TOTAL 3 0.00043~~

~~7Be Amersham International 1 20.0 Lovelace Biomedical 2 107.0 Oak Ridge Associated Universities 1 0.5 TOTAL 4 127.5~~

~~7Br Los Alamos/Group INC-3 12 562.0 University of New Mexico 4 319.5 Washington University 7 273.75 TOTAL 23 1 155.25~~

~~77Br University of California, Davis 1 1.5 Comp TOTAL 1 1.5~~

~~82Br Los Alamos/Group ESS-4 4 66.46 TOTAL 4 66.46~~

~~Atomic Energy of Canada, Ltd. 1 1 000.0 TOTAL 1 ? 000.0~~

~~lwCe Los Alamos/Group INC-11 1 0.094 TOTAL 1 0.094~~

67Cu Albert Einstein/Yeshiva University 7 320.84 California State University, Fullerton 8 974.4 Hospital for Sick Children, Toronto, Canada 9 1 396.0 IBM Research Center 2 30.2 Johns Hopkins Medical Institute 1 12.5 Los Alamos/Group INC-3 17 722.3 Los Alamos/Group LS-3 4 112.7 National Institutes of Health 2 226.8 New England Nuclear Corp. 2 261.9 University of California, Davis 10 1 543.67 University of Saskatchewan 3 124.9 USDA, Beltsville, Maryland 4 40.5 USDA, Grand Forks, North Dakota 1 5.0 TOTAL 70 5771.71

~~S '-Fe University of Nebraska Medical Center 1 409.8 TOTAL 409.8 RADIOISOTOPE PRODUCTION 141~~

~~TABLE I. Medical Radioisotope Shipments — FY1984 (Cont).~~

~~Number of Amount Isotope Institution Shipments (mCi)~~

68Ge Memorial Sloan-Kettering Cancer Center 5.0 Medical Research Council, Hammersmith Hospital London 70.0 Oak Ridge Associated Universities 5.0 Office des Ravonnement Ionisant, France 21.5 University of Chicago Radiation Protection Service 2.5 University of Liege, Belgium 36.6 University of Michigan 18.0 Washington University 50.0 TOTAL 8 208.6

~~"Ho EP-Isolde, CERN 1 1.0 TOTAL 1 1.0~~

~~22Na New England Nuclear Corp. 2 1 240.0 TOTAL 2 1 240.0~~

~~86Rb University of South Carolina/New England Nuclear Corp. 1 0.268 TOTAL 1 0.268~~

l2Sr E. R. Squibb & Sons 10 5 101.29 Medical Research Council, Hammersmith Hospital, London 3 3*0.236 E. R. Squibb & Sons/Sloan-Kettering Institute 1 154.1 E. R. Squibb & Sons/Sloan-Kettering/ University of Texas 1 300.0 University of California, Donner Laboratory 5 1131.88 University of Liege, Belgium 1 158.4 University of Wisconsin 1 146.5 TOTAL 22 7 382.406

~~48V California State University, Northridge 2 21.7 Los Alamos/Group HSE-8 1 0.5 TOTAL 3 22.2~~

~~-127Xe Brookhaven National Laboratory 4 32 220.0 TOTAL 4 32 220.0~~

~~m\ Hybritech, Inc. 2 20.15 Isotope Products Laboratories 1 8.0 New England Nuclear Corp. 2 16.26 University of Minnesota 1 8.0 TOTAL 52.41~~

~~Total Shipments: 156 Total Curies Distributed: 49.66 142 PROGRESS AT LAMPF—1984~~

~~TABLE H.a Targets Loaded at the Isotope Production Facility at LAMPF. Number of Target Primary Product Loadings~~

~~BaCI, 123! 3 CsCl 127Xe 14 CsCl i»! 7 RbBr 68Ge 11 Ni "Fe 8 Mo 77Brandr-Sr 21 ZnO 67Cu 21 Al "Na 4 In 10»Cd 7 KC1 32Si 1 EuO, 145Sm 1 Pb 195Au 3 MnCb 44Tj 3 Radiation damage~~

~~"From M. A. Ott, N. J. Segura, and F. H. Seurer (Los Alamos)~~

Stringer. The number 1 stringer at LAMPF has stainless steel cold trap inside a shielded container. been replaced with a new design to accommodate the This container is later transferred to the hot-cell continuous collection of gases produced by spalla- complex at INC Division where the '"I is removed. tion, in particular the radioxenon parents of I23I and The system is set up so that the time of collection can I2SI. The stringer is 7.9 m long with two rectangular be varied, depending on the quantity of I23I desired.

sections—one 4.6 m long filled with magnetite con- In a typical run, 144 g of molten BaCl2 is poured crete for shielding ai:d the second 3.7 m long without into the carrier reservoir through the gas-outlet hole. concrete shielding. The stringer was designed to ac- The container is then transported to LAMPF and cept standard carrier containers in addition to special connected to the stringer, remaining in place for stainless steel containers that allow the radioxenons repeated runs. The gas-circulation system is to be swept from the molten salt (CsCl or BaCl2) with pressurized to 20-psia helium, which serves as a a helium-gas stream. carrier for the radioxenons, and the generator is cooled in liquid nitrogen to trap the xenons Target Holder. The target carrier is also a new produced. Once gas circulation has begun, the con- design, with all welded seals except for the fittings tainer is placed in the beam. The activity in the that connect it to the stringer head to allow for generator is monitored through an ionization circulating gas over the target reservoir (5.7 by 5.7 by chamber detector. At the end of the run, the generator 1.5 cm) and for cooling-water circulation around the is disconnected from the manifold and enclosed in a reservoir. The helium inlet of the target reservoir is cask for transport to the hot-cell facility where the equipped with a gas deflector, which was installed to generator is removed from the cask and, after an minimize BaCK transport during the gas collection. appropriate growth period, the remaining xenons are removed by evacuation. The iodine in the generator Collection Station. A collection station was de- is extracted with hot 0.02-M NaOH. signed and fabricated to accumulate radioxenons in a RADIOISOTOPE PRODUCTION 143

Preliminary Results. Four runs gave the following and should provide a support system that can survive encouraging results. ever a generator lifetime of 2 or 3 years. First Run. A 2-h irradiation followed by a 2-h 1. Ogard,3 using basic AliO, as the ion-exchange growth period in the generator resulted in 556-mCi material, achieved a 50% yield of 109mAg with a i:3I with a l.2-mCi '-5I contamination (0.22%). An l01)Cd breakthrough of 2.8 X 10"4. additional 4-h growth period for the xenons that were 2. Ehrhardt et al.4 used zirconium phosphate ion- removed from the generator yielded another 188- exchange material to form a generator with a mCi i:3I with 1.3-mCi :25I (0.7%). 40-60% yield of ")9mAg with a 1(WCd break- Second Run. A 1-h irradiation followed by a 2-h through of 3 X 10~6. A cleanup column was growth period yielded 329-mCi '-'I with 0.60-mCi 125I needed to reduce breakthrough below 10"6. (0.18%). 3. Yano and Anger5 used alumina to achieve a Both runs occurred while the beam current was 32% yield of l(WmAg with a breakthrough of 2 X approximately 570 uA. 10"4. Third run. Another 2-h irradiation at slightly In all three cases the 20- to 40-year biological half-life higher beam current, followed by a 2-h growth of cadmium suggests that the l09Cd breakthrough is period, yielded 590-mCi i:i3 with 1.26-mCi l25I con- too high for use in patients.6 Therefore, we undertook tamination (0.21%). A second 4-h growth period the development of a llwCd —* 109mAg generator based yielded an additional 163-mCi '-'I with 1.1-mCi |:5I on an inorganic ion exchanger that would have a high (0.67%). 109mAg yield and lower IOTCd breakthrough. Fourth run. This run was attempted at the very end In our experiment, tin phosphate, a commericially of the LAMPF run cycle with a beam current of only available inorganic ion exchanger, was selected as the 470 uA. This current was approximately haif of that column material. The exchanger was ground and observed during most of this cycle, and as a result it sieved with the 80-115 mesh fraction retained for use appeared that the target was only partially melted in in the column. This fraction was slurried in a 0.1-M beam. Even so, a 4-h irradiation followed by a 4-h phosphate buffer and poured into a column to form a growth period yielded 524-mCi 1:'] and 1.95-mCi |:5I 1.5-cm' bed. The ion exchanger was then rinsed with (0.37%). a 0.1-M phosphate buffer at pH = 7.4 until the eluate More studies are currently under way to evaluate pH was 7.4. the effects of varying irradiation times and growth Cadmium-109 was produced at the beam stop at times on the quantity and purity of the I23I produced. LAMPF by 800-MeV proton irradiation of an in- dium metal target. The details of the recovery are given in Ref. 2. The stork solution of m''Cd was 109Cd — I09raAg Biomedical Generator evaporated to dryness and taken up in 200 uS of distilled water. A 5O-u8 aliquot was assayed for 109Cd F. J. Steinkniger, P. M. Wanek. and D. C. Moody content. The column was drained by gravity flow and Silver-109m, with a half-life of 39.6 s and a gamma a 5O-u8 aliquot of the lf)9Cd stock solution was placed ray at 88 keV (P.ef. 1), has potential as a dynamic on the top of the exchanger bed, followed with 100 uf imaging agent and, possibly, as a pediatric imaging of distilled water. The column was capped and al- agent. The availability of large quantities of l09Cd lowed to stand. m9 109m suggests the feasibility of a Cd — Ag generator The eluent combination was based on (1) decreas- in9 2 with a high Cd loading, perhaps in curie quantities. ing the reduction potential of Ag+ (£" = 0.8 V) by 2 3 Such parent loading will overcome the low intensity complexation with S:O7 forming Ag(S2O3); (F° = (3.62%) of the 88-keV gamma by providing a substan- 0.01 V) and (2) then reducing the complex to Ag" IO9m tial source o'.'daughter Ag. with a mild reducing agent, the hypothesis being thai A biomedical generator containing curie quantities reduced silver would not be readily readsorbed by the of 109Cd, with a half-life of 453 days, implies the use of inorganic cation exchanger and would be released to an inorganic ion-exchange material. Such materials the eluent. Two combinations were tested: (1)5% possess higher radiation resistance than do standard ascorbic acid and 5% phosphate buffer (pH = 7.4, ion-exchange resins based on organic solid phases 2 X 10-4-M Na,S,O,) and (2) 5% dextrose and 5% 144 PROGRESS AT LAMPF—1984

! Mcllvaine's buffer (pH = 3.8, 2 X 10~ -M, Na,S,O3). an eluent consisting of 5% dextrose and 5% Mcll- Both eluent combinations are approximately vaine's buffer (2 X 10~4-M Na^O.,), has exhibited a isotonic, but they would require pH adjustment steady daughter yield of 56% with a l09Cd break- before injection into patients. The standard elution through of 10~7. This stability has been demonstrated procedure was to draw a l.5-mft sample in approx- over a 6-month period using 527 samples, 1,5 mC in imately 7 s. The generator was then left static for 10 size. The breakthrough has beep slowly dropping, min to reestablish secular equilibrium before the next with some samples showing 10"8 values, We will elution. continue efforts to improve the l09mAg yield while The first eluent combination tested was the continuing to drop the parent breakthrough. We will ascorbic acid combination. Initial l09mAg recovery also perform experiments to determine what mecha- increased to a maximum of 75% and then decreased nism is operating on the column to learn whether u to a steady value of 48%. The lQ'Cd breakthrough reduction of the complexed silver to Ag plays any dropped rapidly into the range from 10~6 to 10~7 and part in silver elution from the column. remained steady. The cause of the decrease in 109mAg recovery is not known. References At sample 386 a regeneration process, consisting of 1. C. M. Lederer and V. Shirley, Table of Isotopes a 200-uB rinse with 0.05-M NaOH, was completed. (Wiley-Interscience, New York, 1978), p. 502. Following this rinse, UWmAg was eluted with the dex- 2. F. J. Steinkruger, G. E. Bentley, H. A. O'Brien, et al., trose combination. The IO9mAg yield gradually in- l09 "Production and Recovery of Large Quantities of creased to 56%, whereas the Cd breakthrough re- Radionuclides for Nuclear Medicine Generator Sys- 1 mained in the 10" range. tems," in Raclionuclide Generators, F. F. Knapp, Jr., At sample 520 the generator was left in a static and T. A. Butler, Eds., American Chemical Society condition for 3 months under the 5% Mcllvaine's Symposium Series 241 (1984), pp. 179-184. 109m buffer. After the storage period, elution of Ag was l09 l09m 109m 3. A. E. Ogard, "Preliminaries to a Cd — Ag continued with the dextrose combination. The Ag generator system," in the Proceedings of the Joint yield remained steady at 54%. After an initial in- American Chemical Society/Chemical Society of crease in '""Cd, its breakthrough returned to previous Japan Chemistry Congress, Honolulu. Hawaii, April low levels. 1979. gm The utility of'" Ag as an imaging agent was shown 4. G. J. Ehrhardt, L. Maoliang, W. F. Goeckeler, et al., by the elution directly from the generator into the "New IO9Cd/IO9mAg Generator System," in the stomach of a rat through a small plastic tube inserted Proceedings of the International Symposium on into the esophagus of the animal. The stomach was Single Photon Ultraslwrt-Lived Radionuclides, clearly visible, as was the tube in the esophagus. The Conf-830504, Washington DC, May 3-5, 1982, in tube was visible because acquisition of the image was press. initiated simultaneously with elution of the l09mAg. 5. Y. Yano and H. O. Anger, "Ultrashort-Lived Radio- Later, stomach dumping into the intestine and isotopes for Visualizing Blood Vessels and Organs," backup of the isotope in the esophagus were seen. Journal of Nuclear Medicine 9, 2-6 (1968). Both images resulted from the introduction of ap- 6. L. Friberg, G. Nordberg, and M. Piscator, "Cad- proximately 5 mCi of """"Ag. mium," in Toxicology of Metals, Vol. II, Environ- mental Health Effects Research Series Conclusions. A ""'Cd —* ":g"'Ag generator, based on EPA-600/1 -77-022 (1977), pp. 124-163. tin phosphate inorganic ion-exchange material and RADIOISOTOPE PRODUCTION 145

Radiopharmaceutical Labeling Research Porphyrins were selected as a class of chelating agents because they coordinate copper (II) readily3-6 and Radiolabeling Monoclonal Antibodies form stable complexes with copper7 and because they can be obtained with a variety of peripheral func- The objective of this research is to develop meth- tional groups for attachment to antibodies. We have ods of attaching radionuclides to monoclonal anti- investigated meso-tetra (4-carboxyphenyl) porphine, bodies and antibody fragments for use in tumor H TCPP, as a chelating agent for 67Cu because this imaging and internal radiation therapy. Monoclonal : porphyrin has water solubility and four carboxylic antibodies and their fragments are of interest because acid groups for conjugation to proteins. Th>_ metala- they enable the selective targeting of tumors. The tion of H TCPP by 67CuCU to form the copper labeled antibodies could be employed as carriers to 3 chelate 67CuTCPP has been optimized and can be transport radioisotopes to tumors,' thus minimizing performed in 30 min. total-body radiation dose and radiation damage to Conditions have been developed to separate normal tissue. Because the time required for labeled (l7Cu2+, H.TCPP, and "CuTCPP by preparative-scale antibodies to find the tumor antigen and deliver the 2 high-performance liquid chromatography (HPLC). dose to the tumor is estimated to be about 1-3 days, Carrier-added metalation of H TCPP with 67CuCl radionuclides with a 1- to 3-day half-life would be : : 23 has been performed in a 93% radiolabeling yield. In optimum for this purpose. Two of the radio- 67 77 the analogous preparative-scale no-carrier-added re- nuclides produced at LAMPF, Cu and Br, have the actions, radiolabeling yields of as high as 90% have suitable half-life and nuclear-decay properties for use been obtained. An ion-exchange chromatography in tumor imaging or therapy with radiolabeled anti- procedure has been developed to remove the paired bodies. These radionuclides and the efforts to prepare ion chromatography (PIC) reagent, heptafluoro- radiolabeled antibodies with them are described in butyric acid, which was introduced during HPLC. greater detail below. Removal of the PIC reagent is necessary when the We have used three different approaches to meet labeled porphyrin is to be used in biological studies this objective of labeling antibodies: (1) labeling because the PIC reagent can denature proteins. Thus, chelating agents with metal radionuclides, then con- high-purity, high-specific-activity "CuTCPP can be jugating the labeled chelating agents to antibodies; (2) readily prepared for animal biodistribution and anti- conjugating activated chelating agents to antibodies, body conjugation studies. During the LAMPF cycle followed by metalation with metal radionuclides; and that ran from June to October 1984, a total of 45 mCi (3) radiobrominating small molecules that can be of

F. J. Steinkruger and G. E. Bentley, "Production and D. S. Wilbur and Z. V. Sivtra, "Studies Toward Radio- Recovery of "Fe from an Irradiated Nickel Target," in halogenations of Fatty Acids: Radiopharmaceuticals for "Isotope and Nuclear Chemistry Division Annual Re- Evaluating the Heart," in "Isotope and Nuclear port FY 1983." Los Alamos National Laboratory report Chemistry, Division Annual Report FY 1983," Los Ala- LA-10130-PR (May 1984), pp. 79-80. mos National Laboratory report LA-10130-PR (May 1984), pp. 104-106. K. E. Thomas and W. A. Taylor, "Progress with Isotope Production from Molybdenum Targets," in "Isotope and Nuclear Chemistry Division Annual Report FY Group INC-3 Papers Accepted for Publication 1983," Los Alamos National Laboratory report LA-10130-PR(May 1984), pp. 80-81. D. S. Wilbur, "Structural Determinations of Some Chloroazepin-2,5-Diones Using a Lanthanide Shift Re- K. E. Peterson, M. A. Ott, F. H. Seurer, and K. E. agent," Los Alamos National Laboratory document LA- Thomas, "INC-3 Isotope Production Activities in FY UR-83-2233 (to be published in the Journal ofHeter- 1983," in "Isotope and Nuclear Chemistry Division ocyclic Chemistry). Annual Report FY 1983," Los Alamos National Labo- ratory report LA-10130-PR (May 1984), pp. 82-84. D. S. Wilbur, S. R. Garcia, M. J. Adam, and T. J. Ruth, "An Evaluation of the Introduction of Stable Nuclides J. W. Barnes. M. A. Ott, K. E. Thomas, and P. M. of Bromine into High Specific Activity Radiobromina- Wanek, "Iodine-123," in "Isotope and Nuclear tions," Los Alamos National Laboratory document LA- Chemistry Division Annual Report FY 1983," Los Ala- UR-84-997 (to be published in the Journal of Labelled mos National Laboratory report LA-10130-PR (May Compounds Radiopharmaceutical). 1984), p. 85. D. S. Wilbur and Z. V. Svitra, "Electrophilic Radio- G. E. Bentley and P. M. Wanek, "Characterization of brominations of Hippuric Acid: An Example of the LAMPF-Produced Radiohalogens," in "Isotope and Utility of Aryltrimethylsilane Intermediates," Los Ala- Nuclear Chemistry Division Annual Report FY 1983," mos National Laboratory document LA-UR-83-3686 Los Alamos National Laboratory report LA-10130-PR (to be published in the Journal of Labelled Compounds (May 1984), pp. 85-87. Radiopharmaceutical). S. Yan, H. A. O'Brien, F. J. Steinkruger, and W. A. M. D. Hylarides, A. A. Leon, F. A. Mettler, and D. S. 44 Taylor, "Recovery of Ti From a Proton-Irradiated Wilbur, "Synthesis of 1-Bromo-estradiol" (to be pub- 44 44 Vanadium Target Development of a Ti —» Sc Gen- lished in the Journal of Organic Chemistry). erator," in "Isotope and Nuclear Chemistry Division Annual Report FY 1983," Los Alamos National Labo- ratory report LA-10130-PR (May 1984), pp. 87-89. Group INC-3 Papers Submitted for Publication G. E. Bentley. F. J. Steinkruger, and W. A. Taylor, I. H. Scheinberg, A. G. Morell, R. J. Stockert, H. A. "Applications of Electrochemistry to Isotope Produc- O'Brien, Jr., and G. E. Bentley, "The Physiological Half- tion," in "Isotope and Nuclear Chemistry Division Life of Human Caerulophasmin in Relation to the Annual Report FY 1983," Los Alamos National Labo- Pathogenesis of Wilson's Disease" (submitted to ratory report LA-10130-PR (May 1984), pp. 90-91. Nature). R. S. Rogers, "Antibody Radiolabeling," in "Isotope D. S. Wilbur, chapter in Analytical and Chromalo- and Nuclear Chemistry Division Annual Report FY graphic Techniques in Radiopharmaceutical Chemistry, 1983," Los Alamos National Laboratory report and in the Proceedings of the 1984 National American LA-10130-PR (May 1984), pp. 91-93. Chemical Society Meeting, Los Alamos National Labo- ratory document LA-UR-84-2304. D. S. Wilbur, "Studies of Radiohalogenations Using Trimethylsilyl Intermediates: Radiohalogenations of J. M. Ritchey, A. J. Zozulin, D. A. Wrobleski, R. R. Amines for Brain Studies," in "Isotope and Nudear Ryan, H. J. Wasserman, D. C. Moody, and R. T. Paine, Chemistry Division Annual Report FY 1983," Los Ala- "An Organothorium-Nickel Phpsphido Complex with a mos National Laboratory report LA-10130-PR (May Short Th-Ni Distance. The Structure of 1984), pp. 93-102. Th(C5Me5)2(u-PPh2)2Ni(CO)2," Los Alamos National Laboratory document LA-UR-84-2497 (submitted to the Journal of the American Chemical Society). RADIOISOTOPE PRODUCTION 149//'

K. E. Thomas, "Isotope Production from Molybdenum P. M. Grant and P. M. Wanek, "Radiation-Induced Targets," Los Alamos National Laboratory document Redox Speciation of 77Br in Aqueous Solution as De- LA-UR-84-2671 (submitted \o Radiochimica Acta). termined by Ahion Chromatography," Los Alamos Na- tional Laboratory document LA-UR-84-3868 (sub- P. M. Wanek, F. J. Steinkruger, and D. C. Moody, mitted to Radiochimica Acta). "Separation of l09mAg from l0'Cd: A Biomedical Gen- erator," in the Proceedings at the Fifth Symposium on J. A. Mercer-Smith, A. Raudino, and D, D. Mauzerall, Nuclear Chemistry, Radiochemistry and Radiation "A Model for the Origin of Photosynthesis. III. The Chemistry, Los Alamos National Laboratory document Ultraviolet Photochemistry of Uroporphyrinogen," Los LA-UR-84-3736. Alamos National Laboratory document LA- UR-84-3267 (submitted to Photochemistry and Photobiology). THEORY 151

Theory ture' that sizable "one-step" contributions to DCX could occur through the A33 components of the nuclear wave functions [Fig. I (a)]. This idea provided a realization for a previously proposed two-component Unified Analysis of Pion phenomenological description2 of DCX for N > Z Single- and Double-Charge-Exchange nuclei. According to this picture, anomalies observed Scattering in the Resonance Region in l8O(ji+,7r)l8Ne to the double-isobaric-analog state (DI AS) occur as an interference between this one-step 5. J. Greene, C. J. Harvey, and P. A. Seidl(Univ. of Texas, and the more familiar sequential DCX on two Austin), R. Gilnian (Univ. of Pennsylvania), E. R. nucleons [Fig. l(b)]. This model has been used for Siciliano (Univ. of Georgia), andM. B. Johnson (Los 3 4 Alamos) subsequent explanations and predictions. We have made a detailed microscopic calculation of the terms5 We have made a pbenomenological analysis of all [Fig. l(a) and (b)]. We also evaluate the closely related existing data on pion single- and double-charge- process, shown in Fig. l(c), which we expect to be exchange scattering to isobaric-analog states at larger than that for Fig. l(a) because in the latter process one of the A is off shell. TK — 164 MeV. We use a theory in which both 33 reactions are described by the same optical potential, Virtual A33 in the ground state [Fig. l(a)] contribute U. The form of U is theoretically motivated and negligibly, contrary to recent expectations. On-shell separates explicitly the effects of nuclear structure A33 interactions [Fig. l(c)] can have a large effect and reaction dynamics. The latter is characterized through 7t + p exchange, and inclusion of these phenomenologically by two complex numbers, one terms improves agreement with experiment below for the isovector term and one for the isotensor term resonance. Data at the higher energies cannot be in U. explained by a simple combination of sequential Elastic scattering from selected N = Z nuclei is pion-nucleon scattering plus direct meson A<3 terms. independently fitted to determine the isoscalar terms in U. Realistic Skyrme III densities are used to describe the nuclear structure. We find one set of (a) (b) . parameters that describes the scattering throughout the periodic table. The striking N, Z, and A dependence predicted by the lowest order U and observed in the data is preserved. The data indicate the presence of a large, short-range, second-order (c) \ (d) isotensor term in t/that interferes with the sequential angle charge exchange to give the observed double- charge-exchange angular distribution.

A33 Dynamics in Pion Double Charge FIGURE 1. Feynman diagrams describing A33 Exchange processes that contribute to DCX and that are at A7. B. Johnson (Los Alamos). E. R. Siciliano (Univ. of issue in our work: Colorado). H. Toke (Michigan State Univ.), and A. (a) DCX to A.-,.-, components of the final nuclear Wirzha (State Univ. of New York. Stony Brook) state. DCX from A33 in the initial state is also considered; The expectation that pion double charge exchange (b) DCX through sequential scattering; (c) DCX through direct A33-nudeus interaction; (DCX) would be sensitive to the A33 presence in and nuclei has focused a great deal of attention on these (d) an important interaction contributing to re- reactions. Large DCX cross sections observed for sults shown in (a) and (c). The meson M N = Z nuclei, in particular, have led to the conjec- may be a n meson or a p meson. 152 PROGRESS AT LAMPF—1984

References fixed baryon number there is a strong local minimum in the energy fora particular ratio of the small radius 1. C. L. Morris et al., Physical Review C 25,3218 (1982). to the large radius of the torus. 2. S. J. Greene et al., Physical Review C 25,924 (1982). At the next level, we must take into account quark 3. P. A. Seidel et al., Physical Review Letters 50, 1106 interactions through the exchange of gluons. This (1983). requires careful treatment of divergences in the quark 4. H. T. Fortune et al.. Physical Review C 25, 2142 self-energies. Our conclusion is that the dinotor ap- (1982). pears to remain metastable, resisting compression, deformation, nucleon drip, and breaking instabilities. 5. M. B. Johnson, E. R. Siciliano, H. Toki, and A. We also have more qualitative notions about how the Wirzba, Physical Review Letters 52, 593 (1984). objects could be produced in nuclear collisions.

Pion Charge Exchange Toroidal Bag Nuclei and Anomalons from Oriented, Deformed Nuclei L. Castillejo (Univ. College, London), A. S. Goldhaberand H.-C. Chiang*andM. B. Johnson (Los Alamos) A. D.Jackson (State Univ. of New York, Stony Brook), andM. B. Johnson (Los Alamos) We have extended the theory of pion scattering to study charge-exchange reactions from oriented, de- An interesting kind of unification between hadron formed nuclei. We found that measurement of the physics and field theory is found in a system that we orientation asymmetry for pion charge exchange can have analyzed for a number of years and on which we lead to a determination of the deformation p^of the are about to submit a paper for journal publica- excess neutron distribution. We define the orientation—the "dinotor" or large toroidal MIT bag con- tion asymmetry taining many quarks. We have found that this structure should be rather close in energy per baryon to conventional nuclei and, quite possibly, metastable. This could be an explanation for anoinalons (nuclear As = (9) = dc^'dtl + of/o'dQ fragments with very short mean free paths), if anomalons are ever confirmed convincingly.

The work involves interesting concepts, which x ll have arisen in the context of magnetic monopoles, where da /dQ and da /dQ. are the cross sections for that concern the physical meaning of classical con- scattering from deformed nuclei, with perpendicular figurations of a non-Abelian gauge field. However, and parallel orientation, respectively, to the direction what we find most significant at this point is that the of the incident pions. Determination of As for single large toroidal bag, which is hard to rephrase in chiral charge exchange is difficult but feasible using the field language, seems to be a necessary consequence techniques developed in connection with earlier measurements of pion total cross sections from of the bag hypothesis; thus existence of anomalons l65 could vindicate (and nonexistence vitiate) the use of aligned Ho. bags as anything more than a crude device for de- Sensitivity of the orientation asymmetry to the scribing properties of the simplest hadrons. ratio of the deformation of the neutrons p^'to that of The work has several levels or stages of sophisti- the charge distribution p, is shown in Fig. 1. cation. At the first level, one considers the pure, simplest, original MIT bag model in which the total energy is the sum of the energy from free massless •Currently at the Institute of High-Energy Physics, Academia quarks bouncing around inside the bag and the Sinica, Beijing, China. energy that is proportional to the bag volume. For THEORY 153

~~As(0) 0.7 -~~

~~0.6 -~~

~~0.5~~

~~0.4~~

0.3 FIGURE 1. The asymmetries of 0° from l6SHo plotted as a function of B^/Bf at Tn = 180 MeV. The 0.2 solid curve indicates single charge exchange (it+,it°); the dashed curve, double charge exchange O.t (jf\iT); and the dash-dotted curve, the result for rc+ elastic scattering. We have taken Bf to be fixed at 0 0.8 I.O I.I I.2 I.3 the value 0.32. -O.I

~~-0.2~~

~~0.3 154 PROGRESS ATLAMPF—1984~~

On Muon Decay in Left-Right Symmetric various versions of SU(2)L X SU(2)R X U(l) models Electroweak Models by the experimental results of Refs. 5 and 6 and Peter Herczeg (Los Alamos) compare them in each case with the information on the parameters provided by other data. In the last Abstract section we summarize our conclusions. We discuss the implications of a recent measurement of the positron momentum spectrum end point The Experimental Result on the Positron Momentum in polarized muon decay for general SU(2)L X SU(2)R X U(I) electroweak models. Spectrum End Point The energy-angle distribution of positrons from + Introduction polarized u decays at rest is of the form* The main decay mode of the muon is an important dr(x,9) = A (N(x) - P(x)PMcos6 source of information on the structure of the leptonic (2TC)4 12 interactions. The dominant interaction responsible for the decay is known to have a V — A structure. In + radiative corrections) , (1) the minimal standard model of the electroweak interactions* the decay is entirely due to such an interac- where p and E are the positron momentum and tion. Although the minimal standard model is consis- energy, E() is the maximum positron energy, x = E/Eo, tent at present with all data, for many theoretical and 8 is the angle between the positron momentum + reasons it cannot be viewed as a complete theory. and the spin direction of u . (—PM) is the degree of This situation led to the formulation of various ex- longitudinal polarization of the u+ at the instant of u+ tensions of the model. In many theoretical schemes decay. The constant A is related to the muon lifetime. that go beyond the minimal standard model the main N(x), P(x), and A depend on the parameters of the decay mode of the muon receives contributions from underlying theory. interactions whose structure is different from V — A. The experiments of Refs. 5 and 6 determined the This inspired new efforts to improve the existing quantity accuracy of muon-decay experiments.** One of the recent experimental results comes from / P(x) + radiative corrections\ (2) a precise measurement of the positron momentum w' ~= - PM lim I I spectrum end point in polarized u+ decay.5" This x— 1 VN(x) + radiative corrections/ result was interpreted'7 in terms of the parameters of in the ratio some special versions of SU(2)L X SU(2)R X U(l) electroweak models. In this paper we investigate the constraints implied by the experimental results of = lim 1 + w' cos6 (3) Refs. 5 and 6 on the parameters of more general realizations of SU(2)L X SU(2)R X U(l) models.* In the next section we describe the experimental of the full positron spectrum and the part of the results of Refs. 5 and 6. The following section is a spectrum independent of P near the end point, w' brief review of the relevant aspects of SU(2) X M L was measured using two different techniques. In the SU(2) X U(l) models. In the subsequent section we R first experiment5 the positron spectrum was study the constraints imposed on the parameters of measured near the end point and for momenta in the direction opposite to the direction of the u+ spin, with the muon spin held by a longitudinal magnetic

*The SU(2)L X U(l) model, with only left-handed neutrino fields and with a Higgs sector consisting of a single Higgs doublet. *For general reviews see Ref. 8. Effects of possible nonzero **For reviews see Refs. 1-4. neutrino masses on the muon-decay spectrum have been fThe material in this paper will be submitted for publication. studied in Rcf. 9. THEORY 155 field. The second experiment6 measured the positron tions" emerged first in the framework of a class of spectrum asymmetry above x = 0.88 using a muon- grand unified theories. '- spin-rotation technique. In SU(2)L X SU(2)R X U( 1) eiectroweak models the The combined result of the two experiments is6 fermions are assigned to representations of the group in a left-right symmetric manner: the left- (right-) handed fermions are doublets of SU(2) [SU(2) ] and w > 0.9969 (90% confidence) (4) L R singlets of SU(2)R [SU(2)L]:* or equivalently quarks: « = K(1,TC)<0.0031 (90% confidence) . (5)

In Eqs. (4) and (5) w and R are the quantities w' and R' with the radiative corrections and the effects of the electron mass subtracted. The result (5) is consistent (7) with the prediction R — 0 of the minimal standard model.

~~leptons:~~

SU(2)L X SU(2)R X U(l) Electroweak Models The contrast between the V — A structure of the (TLTRY) = charged-current weak interactions and the vector nature of the electromagnetic and strong interactions is a puzzling aspect of the fundamental interactions. (TLTRY) = (0'/2-1 (8) An intriguing possibility is that the observed V — A structure of the charged current weak interactions is only approximate and that in reality both V — A and V + A currents participate. A model involving both where TL, TR, and Y are the generators cfSU(2)LX V — A and V + A currents was suggested before the SU(2)R X U(l). The corresponding coupling cons- advent of gauge theories by Lipmanov."' His La- tants are gL, gR, and g'. SU(2)L and SU(2)R generate grangian is of the form left-handed (V — A) and right-handed (V + A) interactions, respectively. The model contains four charged gauge bosons [Wf, Wf, see Eq. (12)], the photon, and two massive neutral gauge bosons. Dirac fermion masses are generated by nonzero vacuum expectation values of Higgs fields (one or more) of (6) the type (p ('/z'/zO). Additional Higgs fields must be introduced to break the gauge symmetry down to Uc.m. (1). A possible choice is to add the triplet fields AL(102) and AR(012), which can also generate Ma- where WL and WR are two distinct vector boson fields jorana mass terms for the neutrinos.M coupled to V — A and V + A currents, respectively. The effective four-fermion interaction resulting from In Eqs. (7) and (8) the primed fields are the gauge- Eq. (6) is parity conserving in the limit of equal group eigenstates. They are linear combinations of the mass eigenstates, u,d e,u v,,v: In terms masses for WL and WR. Parity violation appears as a consequence of a mass difference for the two inter- of the mass eigenstates the couplings of the charged mediate bosons. gauge-boson fields WL and WR to the fermions can be The simplest viable gauge theory that leads to a written as structure analogous to Eq. (6) requires SU(2)L X SU(2)R X U( I) as the gauge group. SU(2)L X SU(2)R X *For general reviews of SU(2)L X SU(2)R X U(l) models see U( I) models of the weak and electromagnetic interac- Ref. 13. 156 PROGRESS ATLAMPF—1984

gL the same way as the matrices UL and UR. Together wL they contain n(n — 1) mixing angles and n2 — n + 1 CP-violating phases. In general, both Dirac and Ma- W (9) 2\/2 R jorana mass terms are present in the Lagrangian. The mass eigenstates are then 2n Majorana neutrinos,l6 so that U and V are n X 2n matrices. The 2n X 2n matrix* where rL = yi(l - y5), TR = yx(l + y5) (the Dirac indices have been suppressed), and (15) d\ P= (10) is unitary. Equation (15) contains n(2n — 1) mixing angles and 2n2 CP-violating phases.l8 In what follows, E = (11) the explicit forms of the matrices U, V will not be needed. The effective Hamiitonian for muon decay resulting from Eq. (9) is given by The fields WL and WR are linear combinations of the L L) mass eigenstates W, and W2 H v'M yH 1 - ys)u

~~R) R + cRReyx( 1 + ys)v« v< y 1 + y5)u~~

~~WR = e"° (-sin C W, + cos C, W2) , (12) L) - y5K v™f{ 1 + y5)u~~

RI where £ is a mixing angle and to is a CP-violating + y5)v< vj.'-'yH 1 - y5)n + H.c, (16) phase. The matrices UL and UR are n X n unitary matrices (n = number of generations). UL and UR contain (together) n(n — 1) mixing angles and n2 — n + 1 CP-violating phases. For three generations their general form is15

~~(13)~~

~~eiocR~~

~~e-i(a+r+p) UR = (14) e-i(a+n+pl~~

where sJ-R s sin Q^R and clrR = cos 6^ R. The matrices (13) and (14) contain six mixing angles and seven CP-violating phases. If the neutrinos are Dirac fermions, U and V are *For the mixing matrices in the leptonic sector we use the n X n unitary matrices that can be parameterized in notation of Ref. 17. THEORY 157 where Implications of the Experimental Bound on R

In a general SU(2)L X SU(2)R X U(l) model the gt 81 right-handed quark mixing angles, the CP-violating phases, and the leptonic mixing matrices U and V are arbitrary. Also, the neutrino mass eigenstates can be Dirac or Majorana fermions. Before considering the gLgR general case, we shall discuss the implications of the bound (5) in several special cases of SU(2)L X SU(2)R X U(l) models, characterized by specific assump- gLgR , gLgR\ . „ „ = I - —; + —•, I sin^cosi;e ' = c (17) tions about the unknown quantities and the nature of \ smy 8m: / LR the neutrino states. In all the cases discussed below we make the restrictive assumption that the masses of the neutrinos that can be produced in \i decay are (mi and m: are the masses of W| and W:), and sufficiently small that their effect on the spectrum (18) can be neglected.* Dirac Neutrinos, No Mixing in the Leptonic Sector. (19) In this case the states (18) and (19) are given by

~~Note that |cRL= |cLR|. (22) For the ensuing discussion we shall also need the effective Hamiltonian for AS = 0 semileptonic processes. From Eq. (9) one obtains~~

Unitarity of U and V implies that |U | = |U | U = a C| M2 LL = I vci I = IV!: I = 1 • There is only one decay channel: + + + aRR ZM1 + C 1 + Ys)d u -* e + v, + v:. The functions N(x) and P(x) in Eq. (1) have the familiar form8

~~H.c, (20) _ / 4 ' m'\ \1 1 EjpJ (8 = e,u), where m,. / 1 — x\ + 6n — , aLL = cLL cos 9|- , Eo \ x / iri aRR = cRRe cos 9f ,~~

~~m aLR = cLRe cos 0f ,~~

~~and (23) "|iHl aRL = cRL cos Q\ , (21)~~

~~In Eq. (21) a is a CP-violating phase from U [see Eq. 4 R *lt appears that this requires mVJ/mM < 10"'- lO" (see M. (14)]. Doi et al., Ref. 7; see also Ref. 9). 158 PROGRESS AT LAMPF—1984 with (32)~~

~~3 3 2 Equations (24), (26), and (27) yield 4^ |KRR|~+|KLR| +|KRL|~~

~~(25) (33)~~

~~" •~~

~~3(|KLR|-— |KRL|~) In the following we treat the quantities 2 (26) I KLR | + | KRL |"~~

ml ' grmjj ' g(. and as small parameters and write Kik, T|ik, and p ... as power series in these variables, neglecting ierms 5 = 2 2 2 (27) 4 1 — IK I - higher than second order. We also neglect my/m 4 2 2 relative to one and (gRtygL) relative to g^m /gr.rn?. The existing bounds do not contradict these assump- where we have denoted tions. Introducing the notation

~~= K|k Cik/CLL (ik= RR. LR. RL) . (28) t = (34)~~

The constant A is given by gR my to = (35) gl m2 : 2 2 2 A=16|CLL| (1+|KRR| +|KLR| +|KLR| ) . (29) and Equations (24), (26), and (27) could have been simplified using the relation |KRL| = |KLR|, but we (36) shall keep them general for future reference. EL The muon polarization is given by*

~~I1 -tlml2- (30) we have~~

~~_ gi (m2/m5) + tan1!; _^ (37) where g[ 1 + (my/m2.) tan-^~~

~~= aik/aLL (ik = RR. LR. RD (31) ;) tan e"» ,(38) gL 1 + (mr/rn;) tan- £ For the quantity R [defined in Eq. (5)] one obtains gR (1 - mi/mj) tan C, _.~~

~~gL 1 + (my/m;) tan-^~~

~~•Reference 19: see also Ref. 20. 159~~

~~(40) = gL, co = 0, and UR = UL. The last relation implies that t,i = t and a = 0. Thus Eq. (48) simplifies to~~

~~(41) (49) and This expression was • "fs. 5 and 6 to interpret the experimental b .... 1. The experimental result (5) implies~~

~~—7 < 0.039 for any C, (50) mi The spectrum parameters and P^, are given by~~

~~: 2 p = -(1 - j KLR | - | KRL | ) =* -(1 - 2$ , (43) (with m, ^ 83 GeV, this means that m: > 420 GeV; for £ = 0. one would have my/m; < 0.028), and~~

< 0.056 for any mj/m] (51) (44) (for nv, — oc one would have C, < 0.039). The limit, Eq. (50), is the most stringent constraint (45) on my/m; from leptonic and semileptonic processes.* A tighter bound comes from the nonleptonic sector. Requiring that the contribution from :- l-2t2 , (46) right-handed currents to the KL — Ks mass difference iiMK not exceed the experimental value of AMK leads to the limit22 and mr -S3X 10"' (52) 2 2 m PM=l-2 |%R| -2|nRL| -

(47) The best limit on |£| from leptonic and semileptonic processes is provided by the p parameter in u decay.* The experimental value23 p = 0.7517 ± For the quantity R we find 0.0026 and Eq. (43) imply

~~(90%confidence) . (53) R - (48)~~

~~A stronger bound Let us consider some special cases:~~

~~Manifest Left-Right Symmetry.-' This term is used to describe SU(2)L X SU(2)R X U( 1) models, where gR *See Fig. 14 in Ref. 2. 160 PROGRESS ATLAMPF—1984~~

Itl 2=4X10r-i (54) <4X 10" (58) follows from an analysis of nonleptonic K decays.24 A new constraint* Thus, for manifestly left-right symmetric models the constraints on my/m2. and C, derived from nonlep- 1-3 tonic transitions are stronger at present than those 2X 10 (59) from leptonic and semileptonic processes. It should be noted, however, that they are less reliable, in view follows from searches for a time-reversal odd correla- of the uncertainties involved in calculations of tion ~(J) • p0 X pv in nuclear p decay. Equations (58) nonleptonic amplitudes. and (59) yield approximately the bound (54).

Pseudomanifest Left-Right Symmetry. In this case Nonmanifesi Left-Right Symmetry. Here 0jV= 0}; the left- and right-handed qu^: k-mixing angles are SR ^ gL> and CP violation is in general present. The quantity R is then given by Eq. (48). still equal, bu* CP violation is present. R is now For the quantity t [Eq. (34)], which replaces mj/ml in the muon-decay-spectrum parameters (but —1) + 2C-+ 4_ £ cos (a + U) (55) m-J m; not in PM), Eq. (48) implies

2 which implies the same bounds on C, and my/m , as t< 0.039 for any t0,^ and cos (a + to) . (60) those in Eq. (49).* The limit (53) from the p parameter is, of course unaffected. The constraints from the nonleptonic transitions Next we observe that cos Q\ = "cos 0C" = 1 (0C = described above are also unchanged. The bound in Cabibbo angle), so that Eq. (52) becomes15-5

~~m; (61) —4 |cos(c.-p)| < 3X 10- (56) and therefore~~

~~[P is defined in Eq. (14)]. A new constraint is 4t2, + 2Q + 4t,4 cos (a + to) < R . (62) provided by the CP-violating parameter E in KL — 2K~~

~~decays. From the requirement e| < |ecxp,| one ob- Hence** tains~~

~~|to|< 0.039 for any t, £g, and cos (a + to) (63) — |sin(a~P)| < 1.5 X (57) and~~

Equations (56) and (57) imply again the bound \Q < 0.056 for any t, t9, and cos (a + to) .(64) (52).1525 In the presence of CP violation the bound' (54) becomes •Reference 15: see also Ref. 26. **The bounds (63) and (64) correspond to | cos eV/- cos8f| > 1. Allowing cos B^/cos Gfto be as low as 0.90 would *For a given c = cos (a + to), one has from Eq. (55) increase the limits in (63) and (64) to 0.044 and 0.059, respec- mf/mf < 0.039(2 - cV'.and | Q < 0.056 (2 - c2)""'. tively. THEORY 161

~~The nonleptonic transitions in this case do not place <4.sx (70) limits on t, t8, or £g. The constraints from the KL — Ks mass difference and E are now-8~~

~~Thus Eqs. (60) and (63) are the most stringent bounds iS ifcfc?-sg5,fe «y sfc? available on t and te. The best limit on | £g| is~~

~~|Cel< 0.033, (71)~~

~~3 X 10~3, (65)~~

~~implied by the p parameter. and Majorana Neutrinos; No Mixing in the Leptonic Sector. The states (18) and (19) are~~

~~g^Tl/c^-s^ws^ v — ""^ ( TXI uuisT TX sin(ct ~ P ~~~

~~(72) 1.5 X 10~\ (66) and where (p is the phase of~~

~~(n = number of generations), where~~

~~The bounds (58) and (59) become~~

If both v +1 and v + can be produced in the decay, cos (a + co) cos Gf/cos Q\\ < 4 X 10" (67) n n 2 there are four possible final states, each governed by a different part of the Hamiltonian (16). The observed spectrum is indistinguishable from the spectrum for case (A), as long as the effects of the neutrino masses on the spectrum can be neglected. If both vn+, and vn+2 are heavy, the muon-decay Hamiltonian contains sin (a + co) cos 9f/cos B\\ < 2 X 10" (68) only the V — A part (involving V| and v2). Note that R = 0 also when only the state vn+2 is heavy. If the model has manifest or pseudomanifest sym- respectively. Hence Eqs. (52) and (54) are replaced by metry, the bound

i6 <5X 10" (73) ^rnr 1/ cjfcfc?- s?s5e R\ / sfcj 3 glml IA < 3X 10" (69) is implied in this case by semileptonic data, provided that further quark generations are absent or couple to and the u quark only weakly.29 The constraints (52) and 162 PROGRESS AT LAUPF—1984

~~(54) are, of course, independent of the structure of the The approximate expressions* for the spectrum leptonic sector. parameters and PM are now~~

Dirac Neutrinos; Mixing in the Leptonic Sector. For general matrices U and V the spectrum is an (79) incoherent sum of the spectra of u+ — e+ + Vj + Vj decays over the pairs (v v,) produced in the decay. h (80) As we are assuming that the produced neutrinos are light (see introduction to this section), the sum over 2 the pairs can be replaced by the sum Ijl], where the = I - 2t v,vM (81) primes indicate that the sums extend only over the mass eigenstates produced in the decay. By the same _ 3 assumption the set of neutrino mass eigenstates (82) 4 participating in 7c —»uv decays is the same as the one in muon decay. =; 1 - 2t-vt.v(1 (83) The observed spectrum is given by Eqs. (1) and (23) with parameters p, £,... that can be obtained from Eqs. (24)-(27) by the substitutions and

~~=M - 2ts VM - 2^; v^ - vMcos(a + a>) . (84)~~

~~|cLL|-u,U(1 , The quantity R is given by~~

~~|KRR| R = 2t- vovM 2Q vM vMcos(a + co). (85)~~

~~and The experimental result (5) implies~~

~~(74) : 0.039~~

~~where for any ta\/v(,, £g \/vM , and cos(a + co) , (86)~~

~~2 u8 = X|Uei| (8 = e,u) . (75) and 2 vB = 2: | vffi | (5 = e,u) , (76) i t« vM + c^vM + 2tB ^evp cos(a + co) < 0.039~~

~~for any t\/vL.vM . (87) and~~

vt = ve/u» (C = e,u) . (77) For a given c = cos (a + co), Eq. (87) yields |tH V^l 2 1 < 0.039 (1 -cY"' and |?g\/v7| < 0.039 (1 -c )" -. Hence for c = ±1 (which is not ruled out), Eq. (87) Similarly, PM is obtained from Eq. (30) by the substitution1920 *Notc that the value of | u,|(i =e.n) is in the vicinity of 1. This is evidenced by ihe good agreement between the measured and the predicted values of the W, mass, together with the ex- Note that if all the mass eigenstates can be produced perimental value of the n —» ev/n — |iv branching ratio. Therefore the spectrum parameters and PM can be expanded in the decay we have a, = v, = 1 and therefore the undi^r the same conditions as in case (A). mixing has no observable effect on the spectrum.7 THEORY 163

sets no uncorrelated constraint on tfl extending the definition of u, and vc [Eqs. (75) and Forc = ±l,Eq. (87) implies (76)] to include the general case, the quantity R is given by Eq. (85) regardless of the nature and number (88) of the neutrino mass eigenstates. With these defini- tions of ut and vc, Eq. (85) (given our approxima- The best limit on |Cg\/%l is provided by the p tions) is the most general expression for R in SU(2)L parameter. The experimental value and Eq. (79) im- X SU(2)R X U(l) electroweak models. The cor- ply responding bounds on the parameters are given in Eqs. (86) and (88).* Assuming that the additional < 0.047 (90% confidence) . (89) terms in the spectrum do not affect appreciably the experimental value of p (which is probably the case, as the p parameter describes the high-energy part of Combining (88) and (89) yields the spectrum), the bound (89) and consequently also <0.086 , (90) the bound (90) remain valid.

Conclusions which is the most stringent available bound on the quantity [tB \/%\. The purpose of this paper was to study the con- For manifest left-right symmetry and straints on the parameters of various realizations of pseudomanifest left-right symmetry, the bounds de- SU(2)L X SU(2)R X U( 1) electroweak models, implied rived from nonleptonic transitions have to be taken by recent measurements of the end point of the into account. Because the value* of |uM | is in the positron momentum spectrum in polarized muon neighborhood of 1, we have | vM | < 1; therefore, from decay. For all cases considered we have assumed that Eqs. (52) and (54) one obtains the neutrinos that are produced in the decay are sufficiently light that the effects of their masses on the (91) spectrum can be neglected. We have also assumed that quantities such as my/m; and C, can be treated as small parameters. and The various versions of SU(2)L X SU(2)R X U(l) models discussed can be divided into two classes: (1) (92) models where leptonic mixing is assumed to be absent or negligible and (2) models with arbitrary mixing in the leptonic sector. Majorana Neutrinos; Mixing in the Leptonic Sec- In cases where leptonic mixing is neglected, the tor. The most general Lagrangian contains both Dirac quantity R depends in the most general case (models and Majorana mass terms for the neutrinos. The complete set of mass eigenstates consists then of 2n *An attractive SU(2)L X SU(2)R X U( I) model with Majorana Majorana neutrinos (n = number of generations).16 neutrinos, which offers an explanation of the smallness of the For Majorana neutrinos additional terms (not masses of the usual neutrinos, was proposed in Ref. 14. The right-handed neutrinos in this mode! are heavy (> 100 GeV) proportional to neutrino masses) appear in the Majorana fermions that mix only weakly with the usual neu- muon-decay spectrum. However, with the effects of trinos. As a consequence, the first term in Eq. (85) cun be neutrino masses on the spectrum neglected, these neglected so that the only relevant constraint is Eq. (87). Also, terms do not survive in the limit x — 1.** Hence, vM = vM holds more accurately than can be assumed for the general case. Equation (87). with te = mf/mi £g = C, for R in this model, was first derived in Ref. 7. The authors of Ref. 7 have *See the preceding footnote. pointed out that there is no uncorrclated constraint from **See M. Doi, Ref. 9, and R. F. Shrock, Ref. 9. If all the mass R on my v^i/m^ ar>d £ NAV 'n ln's casc- eigenstates can be produced in the decay and the effects of the We note that because the model of Ref. 14 has manifest or neutrino masses on the spectrum can be neglected, then the pseudomanifest left-right symmetry, ;he bounds (52) and (54) mixing, as for Dirac neutrinos, has no observable effect on the are applicable. In addition, the limit (73) also holds, provided 2 spectrum because the additional terms vanish and ij | Ut, | = that further quark generations are absent or couple weakly to Si|V«|2=l(seeRef.7). the u quark. 164 PROGRESS AT LAMPF—1984

with nonmanifest left-right symmetry) on four References parameters: t, t9, ^, and cos(a + to) [Eq. (48)]. The 1. M. Strovink, in Weak Interactions as Probes of spectrum parameters p, {;,... are described by two of Unification, AIP Conference Proceedings No. 72, these (t, Q; the remaining two (and Q are involved Particles and Fields Subseries No. 23, G. B. Collins, in the muon polarization PM. The experimental result L. N. Chang, and J. R. Ficenec, Eds. (American for'/? [Eq. (5)] provides for this class of models the Institute of Physics, New York, 1981), p. 46. best available limit on t and te [Eqs. (60) and (63)]. It 2. M. Strovink, "Structure of the Charged Current implies also a stringent limit on £g, not much weaker Interactions," rapporteur talk presented at the than the best present limit (which comes from the Eleventh International Conference on Neutrino experimental value of the p parameter). For models Physics and Astrophysics, Dortmund, Germany, constrained further to have manifest or pseudo- June 11-16, 1984, preprint LBL-18231, August 1984. manifest left-right symmetry, bounds on t = te = mi/iru and £ derived from nonleptonic transitions 3. F. Scheck, "Weak Interactions: Conservation Laws, are more stringent at present than any of the con- Symmetries, Lorentz Structure," invited paper ax straints from leptonic or semileptonic processes. the Tenth International Conference on Particles In general there is unknown mixing in the leptonic and Nuclei (PANIC), Heidelberg, Germany, July 30-August 3, 1984, Mainz University preprint MZ- sector. Taking it into account, the quantity R is given TH/84-09, August 1984. by Eq. (85) (valid for any scenario regarding the neutrino mass eigenstates). It depends again on four 4. H. L. Anderson and W. W. Kinnison, in "Progress parameters [tV^v hy/W^, £g\/% and cos (a + co)], at LAMPF, January-December 1983," Los Alamos National Laboratory report LA-10070-PR (April which are now, however, functions of the elements of 1984), p. 79. the leptonic-mixing matrices. The experimental bound (5) yields the best available limit on 5. J. Carr et al., Physical Review Letters 51,627(1983). tV^H [Eq- (86)]. There are no uncorrelated con- 6. D. P. Stoker et al., "Search for Right-Handed Cur- straints from R on the other parameters, but com- rents Using Muon Spin Rotation," Lawrence bined wixh the limit on £g\/v~n provided by the p Berkeley National Laboratory preprint LBL-18935. parameter the constraint from R implies the most 7. M. Doi, T. Kotani, and E. Takasugi, Progress of stringent available bound on te\/v~M. The muon-decay Theoretical Physics 71, 1440 (1984). spectrum depends also on the parameter CgV^- not involved in R. The best available limit on i^V^o tne 8. A. M. Sachs and A. Sirlin, in "Muon Physics," V. Hughes and C. S. Wu, Eds. (Academic Press, New same as for i^y^ [Eq. (89)], comes from the p York, 1975), Vol. II, p. 49; and F. Scheck, Phvsics parameter. For models with manifest or pseudo- Reports 44, 187(1978). manifest left-right symmetry the constraints derived from nonleptonic transitions are again the most 9. J. Bahcall and R. B. Curtis, Nuovo Cimenlo 21,422 stringent. We note that the parameters involved in R (1961); A. Sirlin, in Proceedings of Muon Physics Workshop, TRIUMF, Vancouver, Canada, 1980, J. are independent of those constrained in p decay. For A. MacDonald, J. N. Ng, and A. Strathdee Eds., Majorana neutrinos further constraints on the TRIUMF publication TRI-81-1 (981), p. 8; R. E. parameters of SU(2)L X SU(2)R X U(l) models come Shrock, Physical Review D24, 1275 (1981), and from searches for neutrinoless nuclear double beta Physics Letters 112EI, 382 (1982); M. Doi, T. decay. However, unlike the parameters contained in Kotani, H. Nishiura, K. Okuda, and E. Takasugi, Progress of Theoretical Physics 67, 281 (1982), and R. these depend on the matrix elements Uci and VCJ, while independent of L' and V . Science Reports, College of General Education, Os- MJ Mi aka University 30,119(1981); P. Kalyniak and J. N. Ng, Physical Review D 25, 1305 (1982); and M. S. Dixit, P. Kalyniak, and J. N. Ng, Physical Review D Acknowledgments 27,2216(1983). I would like to thank H. L. Anderson, W. W. 10. E. M. Lipmanov, Yadernaya Fizika 6, 541 (1967) Kinnison, and M. Strovink for enlightening con- [Soviet Journal of Nuclear Physics 6, 395 (1968)]. versations on muon-decay experiments. THEORY 165

11. J. C. Pati and A. Salam, Physical Review Letters 31, 18. M. Doi, T. Kotani, H. Nishiura, K. Okuda, and E. 661 (1973), and Physical Review D 10, 275 (1974); Takasugi, Physics Letters 102B, 323 (1981); S. M. R. N. Mohapatra and J. C. Pati, Physical Review D Bilenky, J. Hosek, and S. T, Petcov, Ref 16; J. 11, 566, 2558 (1975); and G. Senjanovic and R. N. Schechter and J. W. F. Valle, Ref. 16; and M. Doi et Mohapatra, Physical Review D 12,1502 (1975). al., Ref. 17. 12. J. C. Pati and A. Salam, Ref. 11. 19. R. Shrock, Physical Review D 24, 1232 (1981). 13. R, N. Mohapatra, in New Frontiers in High Energy 20. M. Doi, T. Kotani, and E. Takasugi, Science Re- Physics, A. Perlmutter and L. F. Scott, Eds. (Plenum ports, College of General Education, Osaka Univer- Press, New York, 1978), p. 337; D. P. Sidhu, in sity 32, \9 (\9ZS). Neutrinos—75, proceedings of the International Conference on Neutrino Physics and Astrophysics, 21. M. A. Beg, R. V. Budny, R. N. Mohapatra, and A. Purdue University, 1978, E. C. Fowler, Ed. (Purdue Sirlin, Physical Review Letters 38, 1252 (1977). University Press, West Lafayette, Indiana, 1978); 22. G. Beall, M. Bander, and A. Soni, Physical Review and R. E. Marshak, R. N. Mohapatra, and R. Lc»m48, 848 (1982). Riazuddin, in Proceedings ofMuon Physics Work- shop, TRIUMF, Vancouver, Canada, 1980, J. A. 23. Particle Data Group, Reviews of Modern Phvsics 56, Macdonald, J. N. Ng, and A. Strathdee Eds., No. 2, Pan II, April 1984. TRIUMF publication TRI-81-1 (1981). 24. J. F. Donoghue and B. R. Holstein, Phvsics Letters 14. R. N. Mohapatra and G. Senjanovic, Physical Re- 1138,382(1982). view Letters 44, 912 (1980); and R. N. Mohapatra 25. H. Harari and M. Leuver, Nuclear Phvsics B233, and G. Senjanovic, Physical Review D 23, 165 221(1984). (1981). 15. P. Herczeg. Physical Review D 28,200 (1983). 26. P. Herczeg, in Proceedings of the Conference on the Intersections Between Particle and Nuclear Physics, 16. S. M. Bilenky and B. Pontecorvo, Lettere al Nuovo Steamboat Springs, Colorado, May 23-30, 1984, R. Cimento 17, 569 (1976); S. M. Bilenky, J. Hosek, E. Mischke, Ed., AIP Conference Proceedings No. and S. T. Petcov, Physics Letters 94B, 495 (1980); T. /2i( 1984), p. 904. Yanagida and M. Yoshimura, Progress of Theoreti- cal Phvsics 64, 1870 (1980); and J. Schechter and J. 27. A. L. Hallin et al., Physical Review Letters 31, W. F. Valle. Physical Review D 22, 2227 (1980). 661 (1973); and R. I. Steinberg et al., Physical Review Letters 33,41 (1974). 17. M. Doi, T. Kotani, H. Nishiura, K. Okuda, and E. Takasugi, Progress of Theoretical Phvsica 67, 281 28. P. Herczeg, "On CP-Violation in Left-Right Sym- (1982). metric Eleclroweak Models," to be published. 29. L. Wolfenstein, Physical Review D 29,2130 (1984). 166 PROGRESS AT LAMPF—1984

Report of the T-5 Theoretical Group contributions are at least as large as the first-order L Heller (Las Alamos) term. Moreover, our calculations show that both models lead to overbinding of the triton and indicate Briefly summarized here are a few of the research that further research into constructing realistic three- topics considered during 1984 by members of the nucleon-force models is required. Medium-Energy Physics Theory Group (T-5) of Theoretical Division at Los Alamos. These topics Spin Observables in AW —• AWir span a very wide range of subject matter, from conventional nuclear physics to physics of direct The PI PROD program has been extended to interest to LAMPF and to problems that could be calculate absolute cross sections and Wolfenstein addressed by LAMPF II. (spin-transfer) parameters for the medium-energy nucleon-nucleon reactions pp — pn+n. The model uses three-body amplitudes calculated in a unified, Three-Nucleon Force Calculations unitary way. It has no free parameters in the present Configuration-space, local-potential Faddeev form, which only includes one-pion-exchange forces calculations were expanded to include an initial between the nucleons and isobars. In general, the exploration of the effects of three-body forces on agreement with experiment is good in the region of 1 1 physical observables in the trinucleoa bound state. the A" " " resonance (the upper end of the proton Existing evidence for three-nucleon forces is momentum spectrum). At lower momenta, where the essentially circumstantial because proton and neutron might be expected to have strong • accurate binding-energy calculations for a variety final-state interactions, there are differences between of realistic nonrelativistic force models yield the theory and experiment. triton ground-state energies that are 1 ± 0.2 MeV Calculations of inclusive reactions such as pp —• too small, and pX using PIPROD can be done, but they are very • He form factor calculations do not yield a first computation intensive. Treating such reactions in zero at small enough momentum transfer and do terms of the (dominant) AW — NA transition not produce a secondary maximum of sufficient (followed by A decay) leads to a much simpler magnitude. calculation (hundreds of times faster in computation The angular dependence of a three-nucleon force, time) if one uses the spin-amplitude formalism we which depends simultaneously on the coordinates of developed in collaboration with Orsay colleagues all three interacting nucleons, might alleviate both of some time ago. One curious preliminary result is the these problems. Negative-energy states are a appearance of a relatively narrow structure in angle principal source of such a three-body force, when the and energy (<100 MeV full width in the AW center of non-nucleon degrees of freedom are frozen out of the mass) in the asymmetry parameter near 800 MeV. model space leaving only nucleon degrees of freedom to be taken into account. These same states lead to Pion Charge Exchange the large spin effects in Dirac multiple-scattering formalisms for proton-nucleus scattering that are not We have studied the problem of pion single and observed in ordinary nonrelativistic calculations. double charge exchange (SCX and DCX) at low Our calculations are the first nonperturbative energies. We find that DCX is extremely sensitive to estimates of such three-body-force effects in the the short- and intermediate-range wave functions of trinucleon ground state. We have investigated both the two-neutron system. The cross section for DCX is the Tucson-Melbourne (strongly repulsive at short largely determined from the neutron-neutron wave distances) and the Brazilian (Sao Paulo-Recife) function at distances < 1 fm. At 50 MeV it is certainly phenomenological two-pion-exchange, three- possible to obtain the forward peaking observed nucleon-force models. Most calculations of experimentally using conventional multiple additional binding from such forces have assumed scattering from nucleons, although the detailed first-order perturbation theory. Our results for the choice of angular distribution depends sensitively on Tucson-Melbourne force, conversely, are the choice of nucleon-nucleon wave function. nonperturbative: higher order perturbation theory Qualitative agreement with the magnitude of the THEORY 167

forward-angle cross section is obtained (by a factor and transition rates are then predicted very well. We of 2). discovered that the third,/" = 2+ state in l48Sm at an 150 At higher energies (>180 MeV) where the SCX to excitation energy of 1.66 MeV and in Sm at an the intermediate-analog state is very forward peaked, excitation energy of 1.19 MeV decays predominantly the classical Lane model is more appropriate. From by an isovector quadrupole transition to the ground 100-180 MeV, distortion of the pion wave function state, with the calculated transition rate agreeing with plays a dominant role, and a very careful treatment of the experimental value. this effect would be essential for the extraction of any A more sensitive probe of isovector transitions is information about correlations in the nucleus. the magnetic dipole transition because the neutron and proton gyromagnetic ratios have opposite signs. We have calculated this transition from the third 2+ Electromagnetic and Weak Constraints on states to the first 2+ states and find that the transition Nuclear Wave Functions rates are 10 to 100 times larger than other nearby An examination has been made of how precisely magnetic dipole transitions. To date these magnetic weak and electromagnetic probes determine the wave transitions have not been measured, but attempts to functions of nuclear states. The lowest lying T= 1/2 measure them and to test this conjecture are under and T = 3/2 states of the ,1 = 13 system have been way. If this conjecture is confirmed, it would be of selected as a case study because of the wide variety of interest to determine the separate neutron and proton data involving these states and because an accurate transition densities to these states by a combination knowledge of the wave functions of these states of medium-energy electron, proton, and pion scatter- would remove one of the major uncertainties in ing. calculations involving hadronic transitions such as pion charge exchange or photoproduction. Results show that the use of these wave functions could Renormalization of g-Boson Effects in the IBM change the cross sections for the latter reaction and Although low-lying quadrupole collective states of for electron-scattering form factors by factors of 2 nuclei consist primarily of nucleon pairs in angular from those obtained using Cohen-Kurath wave func- momentum states J = 0+(5) and J= 2f(Z>), there is tions, giving better agreement with data. This some admixture of J= 4+(G) pairs. Heretofore, the emphasizes the importance of using carefully con- IBM has treated only the 5 and d bosons that cor- strained nuclear-structure information in studies of respond to J = 0 and 2; we have now studied the role reaction mechanisms in nuclear media. of the g boson, which is mixed through a quadrupole interaction. We define a new df operator as a linear combination of the original rf* operator and the (Qg*) Low-Lying Isovector Excitations in Nuc'iei operator coupled to J= 2. where Q\& the quadrupole The recent discovery of the 7" = 1+ magnetic operator. For this purpose we introduced a unitary collective state in gadolinium at excitation energy transformation that actually transforms the original = 3 MeV demonstrates that isovector collective d* into this new d\ By choosing a proper mixing states can be quite low in excitation energy. The angle in this unitary transformation, one can include location of such states can give information about the most of the g-boson effect in low-lying collective difference between (1) the effective interaction be- states by the single-particle energy of the new d tween a neutron and proton and (2) the effective boson. The coupling between the new d boson and interaction between like nucleons in nuclei. No the new g boson then becomes minimal. Thus, we isovector transitions to ./" = 2+ states at low excita- can derive a renormalized s-dboson (IBM) Hamilto- tion energies have been identified to date. Using the nian that already :ontains most of the effects from interacting boson model (IBM) of nuclei, we believe the original g bosons. The validity of this re- that we have discovered examples of such tran- normalization has been checked by comparing the sitions. spectrum of an s-d-g boson Hamiltonian with the We used the IBM boson model of nuclei to fit spectrum of the renormalized s-d boson Hamiltonian selected energy levels and transition rates in a series that was obtained from the above s-d-g boson Hamil- of samarium isotopes. The remaining energy levels tonian by the unitary transformation. In other words, 168 PROGRESS AT LAMPF—1984 the microscopic foundation of the IBM that is built So far, a crude but easily calculable approximation by the s and d bosons can now be finally formulated. to the model produces reasonable values for the This unitary transformation technique is a quite average binding energy per nucleon and saturation of general one and can go beyond second-order this quantity in infinite nuclear matter. The crude perturbation. Hence, there should be applications to approximation also qualitatively reproduces the other many-body systems where some states outside enhancement of low-momentum quark components the explicitly treated subspace are strongly coupled to of nuclei that have been experimentally observed, the states in the subspace. European Muon Collaboration (EMC) effect. A more precise calculation has been undertaken for ''He and for X-AHe. This calculation involves the Heavy Dimesosis numerical solution of the Dirac equation for massless quarks, using the collective QCD potential of the A tundamental feature of the theory of quantum model. Even with a trial wave function consisting of chromodynamics (QCD) is the existence of an inter- just the symmetrized sum of quark wave functions in nal variable called color. To learn more about it we individual nucleons, large binding energies are found have examined a very simple system in which the that are due to the reduction of the quark kinetic color degree of freedom plays a significant energy of confinement. Unfortunately, this is more role—namely, two quarks and two antiquarks. With than compensated for by an increase in the color- only one Q and one Q, only one color singlet state is magnetic, spin-splitting energy between pairs of possible; therefore, color is not a true dynamical quarks, which occurs because of the delta-like com- variable. Two-color singlet states are possible for ponents and also because the quark pairs interact in a 2 (PQ , and consequently the color wave function six-dimensional color representation despite a vol- changes with the positions of the quarks. Using the ume-induced reduction in the reduced matrix ele- Born-Oppenheimer approximation to the MIT bag ment. It may be necessary to introduce color-space model, which has been very successful for studying correlations in the quark wave functions to observe v heavy meson systems such as '(cc) and T(bb), we binding. have obtained a hint that there may be a true bound state of CfQ2. Taking only the lower eigenvalue of the 2 X 2 potential matrix and solving the Schrod- Charge-Parity Violation in inger equation variationally, this state is bound by Left-Right JTymmetric Models about 200 MeV. We have to sob.; the coupled- We have studied aspects of charge-parity (CP) channel problem to confirm this result. If it persists violation in electroweak models based on the gauge we will regard it as a firm prediction of the bag model group SU(2)L X SU(2)K X (7(1). We have shown that and will recommend that experimentalists look for the contribution to the CP-violating parameter e' as a this new particle. Experts say that it probably has not result of W,-WH mixing could be as large as the been seen. present experimental limit for this quantity (~ 10~:). The question of how to distinguish a nonzero E' Quark Mode! of Nuclei caused by this and some other mechanisms was considered. We have shown that if a value of e' is We have continued development of this model, found near the present experimental limit, a time- which assumes that a QCD average potential can be rcversal-violating triple correlation involving nuclear defined using properties of QCD known from the polarization and lepton momenta is expected in neu- elementary particle spectrum. The short-to-medium tron (3 decay and |llNe decay and/or hyperon decays at range of nucleon interaction is principally due to the level of IO~4. (The present upper limit for this quark sharing among all of the nucleons in a nucleus. correlation in nuclear p decay is ~ 10"1; there is no Nuclear binding energies, excitation spectra, and significant limit as yet for the analogous term in other properties are then calculable without any free semileptonic hyperon decays.) We also find that the parameters. slope asymmetry in K± — 71*71*71* decays then may THEORY 169 be as large as l0":-l0"3 (the present upper limit is J. L. Friar, B. F. Gibson, and G. L. Payne, "Deuteron Forward Photodisintegration," Physical Review C 30, 441(1984).

LAMPFII J. L. Friar, B. F. Gibson, and G. L. Payne, "One-Pion- Exchange Potential Deuteron," Physical Review C 30, The following T-5 staff members have made con- 1084(1984). tributions to the LAMPF II proposal: B. F. Gibson, J. L. Friar, B. F. Gibson, and G. L. Payne, "Recent T. Goldman, R. R. Silbar, W. R. Gibbs, and P. Progress in Understanding Trinucleon Properties," An- Rosen. nual Review of Nuclear and Particle Science 34, 403 (1984). Group T-5 J. L. Friar, B. F. Gibson, G. L. Payne, and C. R. Chen, "Configuration Space Faddeev Continuum Calcula- Anyone wishing further information on these mat- tions: Nd 5-Wave Scattering Lengths with Tensor-Force ters may contact Group T-5 members J. L. Friar, W. Interactions," Physical Review C 30,1121 (1984). R. Gibbs, B. F. Gibson, V (Group Leader), J. N. W. R. Gibbs and W. B. Kaufmann, "Antiprotonic Ginocchio, T. Goldman, W. C. Haxton (on leave), L. Atomic Energy Levels Via the (p,p) Reaction," Physics Heller, P. Herczeg, and R. R. Silbar. H. Haberzettl, Letters 1458,1(1984). W. B. Kaufmann, and J. A. Tjon were long-term + visitors in T-5 during 1984. T. Otsuka, K. E. Schmidt, W. R. Gibbs, "The # -Nucleus Interaction," Proceed- and M. K. Singham held postdoctoral appointments ings of the Conference on Intersections Between Particle and Nuclear Physics, R. E. Mischke, Ed., AIP Con- in T-5, and D. Frazer and P. Siegel are Associated ference Proceedings No. 123 (1984), p. 859. Western University students who worked in T-5 during 1984. W. R. Gibbs, "The Antiproton-Nucleus Interaction," Proceedings of the Conference on Intersections Between Particle and Nuclear Physics, R. E. Mischke, Ed., AIP Group T-5 Publications Conference Proceedings No. 123 (1984), p. 574. B. F. Gibson, "Electromagnetic and Weak Interactions A. T. Aerts and L. Heller, "Hyperfine Structure of in Few Nucleon Systems," Proceedings of the I Oth Quarkonium States," Physical Review Z3 29, 513(1984). International Conference on Few-Body Problems in C.-R. Chen, G. L. Payne, J. L. Friar, and B. F. Gibson, Physics, Nuclear Physics A416, 503c (1984). "Convergence of Faddeev Partial Wave Series for B. F. Gibson and D. R. Lehman, "Structure of the 3H — Triton Ground State" (to be published in Physical Re- view C). n + d(d*) Vertexes," Physical Review C 29,1017 (1984). J. N. Ginocchio, "A Class of Exactly Solvable Poten- J. L. Friar, "Deuteron Forward Photodisintegration: tials, I. One-Dimensional Schrodinger Equation," An- Meson Currents and Relativity," invited lecture at the workshop "'Perspectives in Nuclear Physics at Inter- nals of Physics (New York) 152, 203 (1984). mediate Energies," Trieste, Italy, October 10-14, 1983, J. N. Ginocchio. "An SO8 Model of Collectivity in published in the Droceedings, S. Boffi, C. Ciofi degli Nuclei," in Bosons in Nuclei, D. H. Feng, M. Vallieres, Atti, and M. M. Giannini, Eds. (World Scientific Pub- and S. Pittel, Eds. (World Scientific Publishing Co., lishing Co., Singapore, 1984), p. 124. Singapore, 1984), p. 81. J. L. Friar and S. Fallieros, "Extended Siegert J. N. Ginocchio, "Medium Energy Probes and Nuclear Theorem," Physical Review C 29, 1645 (1984). Structure," Nuclear Physics A421, 369c (1984). J. L. Friar. "What Are Little Nuclei Made Of?" invited J. N. Ginocchio, "A Class of Exactly Solvable Poten- talk at the Few-Body Gordon Conference, Wolfeboro, tials, II. Three-Dimensional Schrodinger Equation," New Hampshire, August 15. 1984. Los Alamos National Laboratory document LA- UR-84-758 [to be published in the Annals of Physics J. L. Friar and E. L. Tomusiak, "Relativistically Cor- (New York)]. rected Schrodinger Equation with Coulomb Interac- tion." Physical Review C 29, 1537 (1984). J. L. Friar and S. Fallieros, "Deuteron Electric Polarizability," Physical Review C 29, 232 (1984). 170 PROGRESS ATLAMPF—1384

J. N. Ginocchio, "Medium Energy Probes and the Inter- P. Herczeg, "CP-Violation: The Standard Model and acting Boson Model," in Internationa! Workshop on Left-Right Symmetric Electroweak Models," in the Interacting Boson-Boson and Boron-Fermion Systems, Proceedings of the Conference on the Intersections Be- Olaf Scholten, Ed. (to be published by the World Scien- tween Particle and Nuclear Physics, R. E. Mischke, Ed., tific Publishing Co.), AIP Conference Proceedings No. 123 (1984), p. 904. J. N. Ginocchio, "Medium Energy Scattering and the D. R. Lehman, A. Eskandarian, B. F. Gibson, and L, C. Interacting Boson Model," invited talk, in International Maximon, "Momentum-Space Solution of a Bound- Workshop on Interacting Boson-Boson and Boson-Fer- State Nuclear Three-body Problem with Two Charged mion Systems, conference held at Gull Lake, Michigan, Particles," Physical Review C 29,1450 (1984). May 1984. B. H. J. McKellar and B. F. Gibson, "Nonmesonic J. N. Ginocchio, "Low-Lying Isovector Excitations in Decay of Heavy A Hypernuclei," Physical Review C30, Nuclei," invited talk, in International Symposium on 322(1984). the Nuclear Shell Model Honoring Igal Talmi, Drexel T. Otsuka and J. N. Ginocchio, 'isovector Low-Lying University, October 31-November 3,1984. Collective States and the Interacting Boson Model," Los T. Goldman, "Quark Tunnelling in Nuclei," Physics Alamos National Laboratory document LA- Letters 1468,143(1984). UR-84-3811 (to be published in Physical Review Letters). T. Goldman, "Quark Tunnelling in Hypernuclei," Proceedings of the Conference on the Intersections Be- T. Otsuka, "Independent-Pair Property of Condensed tween Particle and Nuclear Physics, R. E. Mischke, Ed., Coherent Fermion Pairs and Derivation of the IBM AIP Conference Proceedings No. 123 (1984), p. 799. Quadrupole Operator," Physics Letters 138B, 1 (1984). T. Goldman, "Family Problems," Proceedings of the T. Otsuka, "Microscopic Calculation for Deformed Nu- Conference on the Intersections Between Particle and clei," invited talk, in Interacting Boson-Boson and Nuclear Physics, R. E. Mischke, Ed., AIP Conference Boson-Fermion Systems, O. Scholten, Ed. (World Scien- Proceedings No. 123 (1984), p. 895. tific Publishing Co., Singapore, 1985). T. Goldman, "Neutrino Masses and Mixings—An T. Otsuka, "Microscopically Derived Interacting Boson 'SPVAT' Analysis," International Conference on Model," invited talk, in the Fifth International Sym- Baryon Nonconservation, Park City, Utah (to be pub- posium on Capture Gamma-Ray Spectroscopy and Re- lished in Proceedings of ICOBAN 84. D. Cline, Ed., lated Topics, S. Raman, Ed., conference held at Knox- p. 185), Los Alamos National Laboratory document ville, Tennessee, September 10-14, 1984 (to be pub- LA-UR-84-644(1984). lished in the AIP Conference Proceedings Series, 1985). T. Goldman, "Gluinonium: The Hydrogen Atom of G. L. Payne, W. H. Klink, W. N. Polyzou, J. L. Friar, Supersymmetry" (to be published in Physica D). and B. F. Gibson, "A Noncompact-Kernel Integral Equation for Three-Body Scattering: nd Quartet Equa- L._Heller and J. A. Tjon, "On Bound States of Heavy tion and Numerical Results," Physical Review C 30, (>'(? Systems," Los Alamos National Laboratory docu- 1132(1984). ment LA-UR-84-3219 (submitted to Physical Review D). P. B. Sicgel, W. B. Kaufmann, and W. R. Gibbs, "K+- Nucleus Elastic Scattering and Charge Exchange," L. Heller and J. A. Tjon, "Heavy Dimesons," to be Physical Review C 30, 1256 (1984). published in the Proceedings of the Santa Fe Meeting of the Division of Particles and Fields, American Physical R. R. Silbar, "Unitary, Unified Models for AW — Society, Santa Fe, New Mexico, October 31-November iVMt," Proceedings of the Conference on Intersections 3, 1984, Los Alamos National Laboratory document Between Particle and Nuclear Physics, R. E. Mischke, LA-UR-84-4046. Ed., AIP Conference Proceedings No. 123(1984), p. 645. P. Herczeg and T. Oka, "Study of Muon-Number- R. R. Silbar, M. W. McNaughton, and O. B. van Dyck, Violating Hyperon Decays," Physical Review D 29, 475 "Need for an Intense Polarized Source at LAMPF," Los (1984). Alamos National Laboratory report LA-10051-MS (April 1984). P. Herczeg and C. M. Hoffman, "Study of 7t° — u*?* Decays," Physical Review D 29, 1954 (1984). R. R. Silbar, C. Milner, M. Barlett, et al., "Observation of A-Hypemuclei in the 12C(jf\AT+)l2C Reaction" (submitted to Physical Review Letters). THEORY

R. R. Silbar and E. Piasetzky, "Isospin Dependence of D. Strottman and W. R. Gibbs, "High Nuclear Pion Absorption on Nucleon Pairs," Physical Review C Temperatures by Antimatter Matter Annihilation" (to 30, 1365E(1984). be published in Physical Letters B). R. R. Silbar. "Spin Dependence of AW and NNn Reac- S. J. Wallace and J. L. Friar, "Approximate Dirac tions and the Question of Dibaryon Resonances," Com- Scattering Amplitudes: Eikonal Expansion," Physical ments on Particle and Nuclear Physics 12,177(1984). Review C29,956(1984). R. R. Silbar and L. J. Curtis, "Self-Consistent Core R. B. Wiringa, J. L. Friar, B. F. Gibson, G. L. Payne, and Potentials for Complex Atoms: A Semiclassical Ap- C. R. Chen, "Faddeev-Monte Carlo Calculations of proach," Journal of Phvsics B: Atomic and Molecular Trinucleon Binding Energy with Three-Body Poten- Physics 17,4087 (1984). tials," Physical Letters 143B, 273 (1984). R, R. Silbar, "Theoretical Aspects of the Nucleon- Nucleon Workshop," in the Proceedings of the Mar- seilles Conference on High-Energy Spin Physics, Mar- seilles, France, September 2, 1984. PUBLICATIONS 173

MP-Division Publications P. D. Barnes, B. Bassalleck, R. A. Eisenstein, G. Frank- lin, R. Grace, C. Maher, P. Pile, R. Rieder, J. D. Ashery, D. F. Geesaman, R. J. Holt, H. E. Jackson, J. Szymanski, W. R. Wharton, J. R. Comfort, F. R. Specht, K, E. Stephenson, R. E. Segel, P. Zupranski, Takeutchi, J. F. Amann, S. Dytman. and K.. G. R. Doss, H. W. Baer, J. D. Bowman, M. D. Cooper, M. Leitch, A. "Pionic Fission Cross Sections on Lithium," Nuclear Erell. R. Chefetz. J. Comuzzi, R. P. Redwine, and D. R. Physics \402, 397 (1983). Tieger, "Isospin Effects in Pion Single-Charge-Exchange J. F. Benage, Jr., R. A. Stern, and R. R. Stevens, Jr., Reactions," Physical Review Letters 50,482 (1983). "Atomic Dipole Transitions Induced by Electrostatic L. G. Atencio, G. P. A. Berg, P. von Brentano, B. Plasma Oscillations," presented at the APS Plasma Brinkmoller. G. Hlawatsch, J. Meissburger, C. F. Physics Meeting, Boston, Massachusetts, October 29- Moore, C. L. Morris. D. Paul, J. G. M. Romer, M. November 2, 1984, Los Alamos National Laboratory Rogge, P. von Rossen, T. Sagefka, O. W. B. Schult, S. J. document LA-UR-&4-2206 (1984). Seestrom-Morris, and L. Zemlo. "The New Focal Plane T. Bergcman, C. Harvey, K.. Butterfield, H. Bryant, G. Detector for the Magnet Spectrometer Big Karl," sub- Comtet, D. Clark, P. Gram, D. MacArthur, M. Davis, J. mitted to Nuclear Instruments & Methods. Donahue, J. Dayton, and W. Smith, "Observation of the N. Auerbach, "Influence of Nucleon Internal Degrees of Stark Effect in n — 4 Level of Hydrogen in Fields up to 3 Freedom on the Strength of Electric Giant Resonances MV/cm," American Physical Society Meeting, Pitts- at Low Energies." Physical Review C 27, 1346 (1983). burgh, Pennsylvania, April 23-26, 1984, Los Alamos National Laboratory document LA-UR-84-490 (1984). N. Auerbach and A. Klein. "A Microscopic Theory of Muon Capture in Nuclei," Nuclear Physics A422, 480 R. Bertini, P. Birien, K. Braune, W. Bruckner, G. Bruge, (1984). H. Catz, A. Chaumeaux, J. Ciborowski, H. Dobbeling, J. M. Durand, R. W. Frey, D. Garreta, S. Janouin, T. J. N. Auerbach and A. Klein, "Excitation of Giant Re- Ketel, K. Kilian, H. Kneis, S. Majewski, B. Mayer, J. C. sonances in the Ca Isotopes in (Jt±.7Cu) Reactions," Nu- Peng, B. Povh, R. D. Ransome, R. Szwed, T.-A. Shibata, clear Physics A422, 501 (1984). A. Thiessen, M. Treichel, M. Uhrmacher, and Th. N. Auerbach and A. Klein, "Structure of Isovector Spin Walcher, "Z Hypernuclear States in (K~, TC*) Reactions Excitations in Nuclei." Physical Review C 30, 1032 on '-C." Physics Letters 136B, 29 (1984). (1984). R. S. Bhalerao and L. C. Liu. "Comparison of Approx- N. Auerbach, A. Klein, and E. R. Siciliano, "Isospin imate Chiral-Dynamical KN •* KKN Models Used for Composition of Giant Resonances and Asymmetries in ,4(7t,2jc) Calculations." Physical Review C 30, 224 7t+ vs re inelastic Scattering," Los Alamos National (1984). Laboratory document LA-UR-84-2002 (1984), sub- R. S. Bhalerao and L. C. Liu, "An Off-Shell Model for mitted to Physical Review Letters. Threshold Pionic r\ Production on a Nucleon and for r\N N. Auerbach, J. D. Bowman. M. A. Franey, and W. G. Scattering," Los Alamos National Laboratory docu- Love, "Reply to Comment on (p,n) and {n.p) Reactions ment LA-UR-84-3384 (1984). submitted to Physical as Probes of Isovector Giant Monopole Resonances," Review Letters. Physical Review C 30, 736(1984). C. Boekema, R. L. Hutson, M. Leon. M. E. Schillaci, S. N. Auerbach and A. Klein. "Transition Densities for A. Dodds. D. E. MacLaughlin, P. M. Richards, A. Charge-Exchange Components of Giant Isovector Re- Yaouanc, and D. W. Cooke, "Muon-Induced Crystal sonances and the Proton-Neutron Density Distribu- Field Splitting at Magnetic Impurities in Metals," Hy- tions in Nuclei." Physical Review C 27, 1818 (1983). perfine Interactions 17-19, 351 (1984). H. W. Baer. R. Bolton, J. D. Bowman, M. D. Cooper. F. E. D. Bush, Jr.. J. D. F. Gallegos, R. Harrison, V. E. Cverna, N. S. P. King, M. Leitch, H. S. Matis, J. Alster, Hart, W r. Hunter. S. E. Rislove, J. R. Sims, and W. J. A. Doron. A. Erell, M. A. Moinester, E. Blackmore, and Van Dyke, "LAMPF Transition-Region Mechanical E. R. Siciliano, "Study of Isovector Resonances with Fabrication," Los Alamos National Laboratory report Pion Charge Exchange," Nuclear Phvsics A396, 437c LA-10136-MS(July 1984). (1983). 174 PROGRESS AT LAMPF—1984

H.-C. Chiang and M. B. Johnson, "Pion Charge Ex- A. B. Denison, C. Boekema, R. Lichti, K. Chan, W. change from Oriented, Deformed Nuclei," Los Alamos Cooke, R. Hutson, M. Leon, and M. E. Schillaci, "Muon National Laboratory document LA-UR-84-2302 (1984), Spin Rotation Study of IAOj," to be published in submitted to Physical Review Letters. Journal of Applied Physics. E. Cclton, "Fixed-Target Option for the SSC," to be W, R. Ditzler, D. Hill, K. Imai, H. Shimizu, H. Spinka, published in the Proceedings of the Conference on the R. Stanek, K. Toshioka, D. Underwood, R. Wagner, A. Intersections Between Particle and Nuclear Physics, Yokosawa, G. R. Burlcson, W. B. Cottingame, S. J. Steamboat Springs, Colorado, May 23-30, 1984, Los Greene, J. J. Jarrner, and R. H. Jeppesen, "Measure- Alamos National Laboratory document LA- ment of the Difference in pp Total Cross Sections for UR-84-3627(1984). Pure Parallel and Antiparallel Transverse-Spin States (Aay) at T,, = 487, 639, and 791 MeV," Physical Review E. P. Colton, "Effect of Magnet Errors on Slow Extrac- D 27,680 (1983). tion," in Proceedings of the DPF Summer Study on the Design and Utilization of the Superconducting Super J. D. Doss, "Passive Dosimeters for rf and Microwave Collider, Snowmass, Colorado, June 23-July 13, 1984, Fields," Review of Scientific Instruments 55, 424-426 Los Alamos National Laboratory document LA- (1984). UR-84-3526(1984). J. D. Doss, "Corneal Temperature Distribution during E. P. Colton, "Longitudinal Tune Control in Synchro- Thermokeratoplasty," Los Alamos National Laboratory trons," to be published in the Proceedings of the Con- document LA-UR-84-3879 (1984), submitted to In- ference on the Intersections Between Particle and Nu- vestigative Ophthalmology & Visual Science. clear Physics, Steamboat Springs, Colorado, May 23-30, J. D. Doss and C. W. McCabe. "Portable Elec- 1984, Los Alamos National Laboratory document LA- UR-84-1953 (1984). trochemical Cell Interrogator," Los Alamos National Laboratory report LA-10274-MS (November 1984). E. P. Colton, "Slow Kaon Beams," to be published in R. W. Fergerson. "The Effects of Focusing on HRS the Proceedings of the Conference on the Intersections Focal-Plane Polarimeter Measurements,*" Los Alamos Between Particle and Nuclear Physics, Steamboat National Laboratory document LA-U R-84-1624 and Springs. Colorado, May 23-30, 1984, Los Alamos Na- tional Laboratory document LA-UR-84-1954 (1984). LA-1015-MS. R. ^. Fisher, M. M. Nielo, and V. D. Sandberg, "Im- D. W. Cooke, R. L. Hutson, M. E. Schillaci, J. L. Smith, possibility of Naively Generalizing Squeezed Coherent P. M. Richards. D. E. MacLaughlin, S. A. Dodds, and J. States," Physical Review D 29, 1107 (1984). A. Oostens, "Ho-Ion Dynamics in H0.vLu1-.rRh.4B4," to fr pub'.ished in Journal of Applied Physics. Z. Fraenkel, E. Piasetzky, and M. R. Clover, "Pion- Nucleus Absorption via the Deka-Nucleon Inter- M. D. Cooper, G. E. Hogan, and M. W. Ritter, "A mediate State," Physical Review C 30, 720 (1984). Suggestion for an Improved Search for u -> ry." Los Alamos National Laboratory document LA-UR-85-37'. B. J. Franczak, "Transitionless Lattices for LAMPFII," (1985). Los Alamos National Laboratory report LA-12060-MS (1984). W. B. CottingariK-, G. R. Burleson, M. Brown, R. Kiziah, D. Oakley. C. Milner. P. Seidl, and N. Tanaka, M. A. Franey and W. G. Love. "Nucleon-Nucleon t- "Floating-Wire Measureir.ents of the Magnet Used for Matrix Interaction for Scattering at Intermediate Large-Aiigle Pion-Nucleus Scattering at EPICS." Los Energies," Los Alamos National Laboratory document Alamos National Laboratory report LA-10201-MS LA-UR-84-3039 (1984), Physical Review C (in press.). (August 1984). J. S. Frank, C. M. Hoffman, R. E. Mischke. D. C. Moir, P. Denes. R. D. Diete: le. D. M. Wolfe, T. Bowles, T. J. S. Sarracino, P. A. Thompson, and M. A. Schardt, Dambeck. J. E. Simmons. T. S. Bhatia, G. Glass, and W. "Measurement of the Branching Ratio for the Rare B. Tippens. "Production of Positive Pions by 800 MeV Decay n° •* e+e~," Physical Review D 28,423 (1983). Protons on Carbon." Physical Review C 27, 1339 (1983). G. C. Giesler, "LAMPF Nuclear Chemistry Data Acqui- sition System," Proceedings of the Digital Equipment Users Society. USA, October 1983, p. 250, Los Alamos National Laboratory document LA-UR-83-3410(1983). PUBLICATIONS 175

G. C. Giesler, "LAMPF Nuclear Chemistry Data Acqui- C. M. Hoffman, J. S. Frank, R. E. Mischke, D. C. Moir, sition System," presented at the National Amaerican J. S. Sarracino, P. A. Thompson p.iv M. A. Schardt, Chemistry Society meeting, August 26-31, 1984, Phila- "Measurement of n'p •* ne+e~ at 300 MeV/c and a delphia, Pennsylvania, Los Alamos National Labora- Search for Scalar and Vector Bosons Heavier Than the tory document LA-UR-84-881. 7t"," Physical Review D 28, 660 (1983). S. J. Greene, C. J. Harvey, P. A. Seidl, R. Gilman, E. R. K. Holinde, M. B. Johnson, and R. Machleidt, "Hermi- Siciliano, and M. B. Johnson, "Unified Analysis of Pion tian Folded-Diagram Potentials in Nucleon-Nucleon Single- and Double-Charge-Exchange Scattering in the Scattering," Los Alamos National Laboratory docu- Resonance Region," Physical Review C 30,2003 (1984). ment LA-UR-85-404 (1985), submitted to Physical Re- view C. D. L. Grisham and J. E. Lambert, "The Remote Re- placement of a Target Cell at LAMPF," to be published J. R. Hurd, J. S. Boswell, R. C. Minehart, Y. Tzing, H. J. in the Proceedings of the 32nd Conference on Remote Ziock, K. O. H. Ziock, L. C. Liu, and E. R. Siciliano, Systems Technology, American Nuclear Society Annual "The Reaction (;t+,n+i/) on 6Li and |:C," submitted lo Meeting, New Orleans, Louisiana, June 1984, Los Ala- Physical Review C. mos National Laboratory document LA-UR-84-1626. C. H. Q. Ingram, P. A. M. Gram, J. Jansen, R. E. D. L. Grisham, J. E. Lambert, T. S. Baldwin, E. L. Mischke, J. Zichy, J. Bolger, E. T. Boschitz, G. Probstle, Ekberg, T. R. Hernandez, and J. L. Ray bun, "Remote and J. Arvieux, "Quasielastic Scattering of Pions from Operations and Viewing Using the Monitor System," "'0 at Energies Around the A(1232) Resonance," Physi- presented at the ANS/ENS International Meeting, cal Review C 27,1578(1983). Washington, D.C., November 11-16, 1984. Los Alamos National Laboratory document LA-UR-84-3458. M. B. Johnson, "What Are We Learning About Nuclei with Pions ai LAMPF?" presented at the International R. H. Heffner and D. G. Fleming, "Muon Spin Relaxa- School of Physics' Enrico Fermi Course XCI, "From tion," Physics Today 37,38 (1984). Nuclei to Stars" at Varenna. Italy, June 18-23, 1984, Los Alamos National Laboratory document LA- P. Herczeg and C. M. Hoffman, "Study of it" -> yfe* UR-84-3214(1984). Decays," Physical Review D 29, 1954 (1984). N. M. Hintz, M. A. Franey, M. M. Gazzaly, D. Cook, G. M. B. Johnson and D. J Ernst, "Field Theoretic Aspects S. Kyle, D. Dehnhard, S. J. Seestrom-Morris, G. W. of Meson-Nucleus Scattering," Phvskal Reviev C 27, Hoffmann, M. Barlett, G. S. Blanpied, J. A. McGill, J. B. 709(1983). McClelland, R. L. Boudrie, F. Irom, and G. Pauletta, M. B. Johnson and E. R. Siciliano, "Isospin De- :a 58 "High Spin States in Si and Ni," Physical Review C pendence of Second-Order Pion-Nucleus Optical Poten- 30,1976(1984). tial," Physical Review C11, 730 (1983). M. V. Hoehn. J. F. Amann. H: ii. Butler. W. K. Dawson. M. B. Johnson, E. R. Siciliano, H. Toki, and A. Wirzba, E. W. Hoffman, J. Hofteizer. M. O. Kaletka, W. W. "Au Dynamics in Pion Double Charge Exchange," Kinnison. T. Kozlov^ki, M. McNaughton, R. E. Mis- Physical Review Letters 52, 593 (1984). chke, M. A. Oothouut, R. V. Foore, E. B. Shera, S. Turpin. and J. M. Weuters, Long-Range Planning A. Klein, W. G. Love, and N. Auerbach, "Continuum Committee fo? LAMPF Computing Needs Report," Los Charge-Exchange Spectra and the Quenching of Alamos National Laboratory report LA-10103-MS Gamow-Teller Strength," Los Alamos National Labora- (June 1984). tory document LA-UR-84-2954 (1984), submitted to Physical Review Letters. C. M. Hoi'Ynan, 'Rare Muon Decays and Lepton- Family Number Conservation," lo be published in the M. Leon, "Resonant Mesonic-Molecule Formation in Proceedings of the 4th Course of the International Muon-Catalyzed d-t Fusion," Physical Review Letters School of Physics of Exotic Atoms on Fundamental 52,605(1984). Interactions in Low Energy Systems, Erice. Italy, March M. Leon, "Leon Responds." Physical Review Letters 53, 31-April 6, 1984, Los Alamos National Laboratory doc- 739(1984). ument LA-UR-84-1327. 176 PROGRESS AT LAMPF—1984

N. Lockyer, T. A. Romanowski, J. D. Bowman, C. M. C. L. Morris, "High Resolution Studies of Pion-Nucleus Hoffman, R. E. Mischke, D. E. Nagle, J. M. Potter, R. L. Reaction Mechanisms," invited valk at the Symposium Talaga, E. C. Swallow, D. M. Aide, D. R. Moffett, and J. on Delta-Nucleus Dynamics, Argonne National Labora- Zyskind, "Parity Nonconservation in Proton-Nucleus tory, Argonne, Illinois, May 1983, Los Alamos National Scattering at 6 GeV/c," Physical Review D 30, 860 Laboratory document LA-UR-83-1746. (1984). C. L. Morris, J. F. Amann, R. L. Boudrie, N. Tanaka, S. J. B. McClelland, "Focal Plane Polarimeter Design," J. Seestrom-Morris, L. C. Bland, P. A. Seidl, R. Kiziah, contributed talk at Magnetic Spectrometer Workshop, and S. J. Greene, "A Range-Nuclear Interaction Ab- College of William and Mary, October 10-12, 1983, Los sorber for Rejecting Mucns at EPICS," Los Alamos Alamos National Laboratory document LA-UR-84-866. National Laboratory document LA-UR-84-3934 (1984), submitted to Nuclear Instruments & Methods. J. B. McClelland, B. Aas, A. Azizi, E. Bleszynski, M. Bleszynski. M. Gazzaly, J. Geaga, N. Hintz, G. Igo, K. I. Navon, M. J. Leitch, D. A. Bryman, T. Numao, P. Jones, J. M. Moss, S. Nanda, A. Rahbar, J. Wagner, G. Schlatter, G. Azuelos, R. Poutissou, R. A. Burnham, M. Weston, and C. Whitten, Jr., "The Experimental De- Hasinoff, J. M. Poutissou, J. A. MacDonald, J. E. termination of the Effective Nucleon-Nucleon Interac- Spuller, C. K. Hargrove, H. Mcs, M. Blecher, K.. Gotow, tion for/>Nucleus Reactions ai Intermediate Energies," M. Moinesler, and H. Baer, "Pion Double Charge Ex- Xuclear Physics A3^6, 29c (1983). change at 50 MeV on UC," Physical Review Letters 52, 105(1984). J. B. McClelland, J. F. Amann, W. D. Cornelius, H. A. Thicssen, B. Aas, and R. W. Fergerson, "A Polarimeter F. E. Obenshain, F. E. Bertrand, E. E. Gross, N. W. Hill, for Analyzing Nuclear States in Proton-Nucleus Reac- J. R. Wu, R. L. Burman, M. Hamm, M. J. Leitch, R. D. tions Between 200 and 800 MeV," Los Alamos National Edge, B. M. Preedom, M. A. Moinester, M. Blecher, and Laboratory document LA-UR-84-1671 (1984), sub- K. Gotow, "Positive-Pion-Nucleus Elastic Scattering at mitted to Nuclear Instruments & Methods. 20 MeV." Physical Review C 27, 2753 (1983). M. W. McNaughton, H. Spinka, H. Shimizu, and K. Y. Ohkubo, and L. C. Liu, "Interference Effects in Johnson. "Spin Transfer in ''Li(pji) and 7L\(p,n) at 800 (n,nN) Reactions." Physical Review C30, 254 (1984). McV," Los Alamos National Laboratory document LA- UR-85-557, submitted to Nuclear Instruments & Meth- H. Ohnuma, F. Irom, B. Aas, M. Haji-Saeid, G. J. Igo, ods. G. Pauletta, A. K. Rahbar, A. T. M. Wang, C. A. Whitten, Jr., M. M. Gazzaly, J. B. McClelland, and f. C. Milner. M. Barlett. G. W. Hoffmann. S. Bart, R. E. Hasegawa, "Cross Sections and Analyzing Powers in the Chricn. P. Pile, P. D. Barnes. G. B. Franklin, R. Grace, (p,d) Reaction Around 500 MeV," Physics Letters 147B, H. S. Plendl, J. F. Amann, T. S. Bhatia, T. Kozlowski, J. 253(1984). C. Peng. R. R. Silbar, H. A. Thiessen. C. Glashausser, J. A. McGill, R. Hackenburg, E. V. Hungerford. and R. L. M. A. Plum, R. A. Lindgrcn, J. Dubach, R. S. Hicks, R. Stearns, "The Observation of Lambda-Hypernuclei in L. Huffman, B. Parker. G. A. Peterson, J. Alster, J. i: + + i: Lichtenstadt, M. A. Moinestcr. and H. Baer, "Isoscalar the C(;r ,K ),N C Reaction." submitted to Physical U Review Letters. and Isovector M4 Spin Transitions in C," Physics Letters 137B, 15(1984). R. E. Mischke, "Parity Nonconservation in Light Hadronic Systems," presented at the Tenth Interna- L. Ray and G. W. Hoffmann. "Systematic Study of tional Conference on Particles and Nuclei, Heidelberg. Relativistic and Nonrelativistic Impulse Approxima- Germany. July 30-Augusl 3, 1984. Los Alamos National tion Descriptions of 300-1000 McV Proton + Nucleus Laboratory document LA-UR-84-2480 (1984). Elastic Scattering," Physical Review C(in press). Y. Mori, K. Ikegami. A. Takagi. Z. Igarashi, S. W. Rcutcr. E. B. Shcra. M. V. Hochn, F. W. Hersman, Fukumolo. W. Cornelius, and R. York. "Optically T. Milliman. J. M. Finn. C. Hyde-Wright, R. Lourie. B. Pugh. and W. Bertoz/i. "Nuclear Charge Densities in Pumped Polarized H" Ion Source." Proceedings of the ; 3rd International Symposium on Production and Neu- the Transition Region: '" Os." Physics Letters 137B, 32 tralization of Negative Ions and Beams, AIP Conference (1984). Proceedings No. 111. Krsto Prelec. Ed. (American In- stitute of Physics. New York. 1984). pp. 769-771. PUBLICATIONS 177

W. Reuter, E. B. Shera, M. V. Hoehn, F. W. Hersman, R. R. Stevens. Jr., R. L. York, J. R. McConnell, and R. T. Milliman J. M. Finn, C. Hyde-Wright, R. Lourie, B. Kandarian, "Status of the New High Intensity H~ Injec- Pugh, and W. Bertozzi, "Ground-State and Transition tor at LAMPF," in Proceedings of the 1984 Linear Charge Densities in |1):Os," Physical Review C30, 1465 Accelerator Conference GSI-84-11, Seeheim, West (1984). Germany, May 7-11, 1984, N. Angerl, ud. (September 1984), pp. 226-228, Los Alamos National Laboratory B. G. Ritchie, R. S. Moore, B. M. Preedom, G, Das, R. document LA-UR-84-1234. C. Minehart, K. Gotow, W. J. Burger, and H. J. Ziock, "•7t+p Scattering at 65 to 140 MeV," Physics Letters G. Suazo and S. P. Koczan, "Standard Operating Proce- 125B, 128(1983). dure Gas Atmosphere Brazing Facility/LAMPF Equip- ment Test Laboratory," Los Alamos National Labora- Louis Rosen, "How Does One Reconcile Ethicai and tory report LA-10231-SOP (October 1984). Moral Values with Personal Loyalties? Case Studies: Facts and Fallacies About Nuclear Energy, and the Pros T. S. Subramanian, J. L. Romero, F. P. Brady, J. W. and Cons of a Nuclear Freeze," invited talk presented to Watson, D. H. Fitzgerald. R. Garrett. G. A. Needham, J. SPAR Incorporated Science, Philosophy, and Religion L. Ullmann, C. 1. Zanelli, D. J. Brenner, and R. E. Prael, Symposium, Air Force Weapons Laboratory, Albu- "Double Differential Inclusive Hydrogen and Helium querque. New Mexico. January 9-10, 1984. Spectra from Neutron-Induced Reactions on Carbon at 27.4, 39.7, and 60.7 MeV," Physical Review C 28, 521 Louis Rosen, "The Los Alamos Clinton P. Anderson (1983). Meson Physics Facility (LAMPF) Fifteen Years Later," Los Alamos National Laboratory document LA- G. W. Swift, A. Migliori, J. Wheatley, C. R. Waller, and UR-84-2031 (1984). G. Suazo. "Fabrication and Leak-Tight Furnace Brazing of Intricate Objects," Review of Scientific Instruments J. J. Rowsey, J. D. Doss, and A. Miranda. "Elec- 55,793(1984). trosurgical Keratoplasty," presented at the 1984 meeting of the American Academy of Ophthalmology, At- H. A. Thiessen, "LAMPF II," to .-> ^+7^ Reaction at0.8GeVand Effects of Mullicusp H Ion Source for Accelerator Applications," Dibaryon Admixtures." Physic Letters 126B, 164 Proceedings of the 3rd International Symposium on (1983). Production and Neutralization of Negative Ions and Beams, AIP Conference Proceedings No. Ill, Krsto R. R. Silbar. and E. Piasetzky, "Isospin Dependence of Prclec. Ed. (American Institute of Physics. New York. Pion Absorption on Nucleon Pairs." Physical Review C 1984). pp. 410-417. 29,1116(1984). G. R. Smitn, j. R. Shepard. R. L. Boudrie, R. J. Peterson. G. S. Adams, T. S. Bauer. G. J. Igo, G. Pauietta. C. A. Whittcn. Jr.. A. Wriekat, B. Hoistad, and G. W. Hoffman. "The (p.cl) Reaction at 800 MeV." Physical Review C 30, 593. (1984). 178 PROGRESS AT LAMPF— J934

R. L. York, R. R. Stevens, R. A. DeHaven, J. R. R. L. York, R. R. Stevens, Jr., K. N. Leung, and K. W. McConnell, E. P. Chamberlin, and R. Kandarian, "The Ehlers, "Extraction of H" Beams from a Magnetically Development of a High Current H~ Injector for the Filtered Multicusp Source," Review of Scientific Instru- Proton Storage Ring at LAMPF," presented at the ments 55,681 (1984). Eighth Conference on the Application of Accelerators in O. van Dyck and M. W. McNaughton, "LAMPF Research and industry, Demon. Texas, November Nuclron-Nucleon Program," in Proceedings of the 6th !2-l4, 1984, Los Alamos National Laboratory docu- International Conference on High Energy Spin Physics, ment LA-UR-84-3043. Marseille, France, September 16-20, 1984, Los Alamos National Laboratory document LA-UR-84-3378 (1984). PUBLICATIONS 179

Experimental Program Reports and Publications EXPS. 74,87 R. L. Boudrie, J. F. Davis, and J. B. McClelland, "Quasi-Free Scattering of Pions on V4He," Nuclear Wi.i's- EXP. 7 /i\sA408,417(1983). M. V. Hoehn and E. B. Shera, "Energies of the Muonic L and M Transitions of the Even-,4 Pb Isotopes," Physical EXP. 103 ReviewC30, 704(1984). J. L Clark, P. E. Haustein, T. J. Ruth, J. Hudis, and A. A. Caretto, Jr., "Energy Deposition Accompanying Pion EXP. 9 Double Charge Exchange: Radiochemical Study of the K. G. Boyer, "Pion Elastic and Inelastic Scattering from : 4 v 4tw 4iMII 54 ""Bi(7C ,7r "Avr""" )At Reactions," Physical Review C 27, -- Ca and Fe," Ph.D. Thesis, University of Texas, 1126(1983). Austin, Los Alamos National Laboratory report (Febru- ary 1984). EXPS. 120,363 D. H. Fitzgerald, "Polarization Parameters in nN Scat- EXP. 9 tering and Charge Exchange in the Region Between the K. G. Boyer, W. J. BraithwaUe, W. B. Cottingame, S. J. A and Roper Resonances," talk presented at the Con- Greene, L. E. Smith, C. F. Moore, C. L. Morris, H. A. ference on the Intersections Between Particle and Nu- Thiessen, G. S. Blanpied, G. R. Burleson, J. F. Davis, J. clear Physics, Steamboat Springs, Colorado, May 23-30, S. McCarthy, R. C. Minehart, and C. A. Goulding, l) ) ii! 1984, Los Alamos National Laboratory document LA- "Pion Elastic and Inelastic Scattering from •> ---'-'-- Ca LI R-84-1681 (1984). and 34Fe," Physical Review C 29, 182 (i 984). EXP. 225 EXP. 12 J. S. Frank, T. J. Bowles, R. L. Burman, R. D. Carlini, D. P. Schuler, K. Hardt, C. Gunther, K. Freitag, P. Herzog, R. F. Cochran, E. Piasetzky, V. D. Sandberg, R. C. H. Niederwestberg, H. Reif, E. B. Shera, and M. V. Allen, V. Bharadwaz, H. H. Chea, P. J. Doe, R. Hoehn, "Experimental Investigation of Low Lying Ex- : Hausammann, H. J. Mahler, K. C. Wang, D. A. cited States in '"Hg," Zeitsehrift fuer Phvsik A313, 305 Krakauer, and R. C. Talaga, "Observation of v,.-^ Elastic (1983). Scattering," presented at the XX5I International Con- EXPS. 13,310,448 ference on High Energy Physics, Leipzig, DDR, July L. C. Liu. "Diffraction Theory and the Double-Charge- 19-24, 1984, Los Alamos National Laboratory docu- Exchange Reaction laO(7t+,7c')ll(Ne," Physical Review C ment LA-UR-84-2325 (1984). 27, 1611(1983). EXP. 249 EXPS. 18,310,393 B. Hoistad, M. Gazzaly, B. Aas, G. Igo, A. Rahbar, C. M. B. Johnson and E. R. '.iciliano, "Isospin De- Whitten, G. S. Adams, and R. Whitney, VJ + 45 pendence of Second-Order Pio,-Nucleus Optical Poten- " He(p,K ) HeBS Reactions at 800 MeV," Physical tial," Physical Review C 27, 731(1983). Review C 29, 553(1984). EXPS. 18,310,393 EXP. 303 M. B. Johnson and E. R. Siciliaio, "Pion Single and D. Ashery, D. F. Geesaman, R. J. Holt, H. E. Jackson, J. Double Charge Exchange in the Resonance Region: R. Specht, K. E. Stephenson, R. E. Segel, P. Zupranski, Dynamical Corrections," Physical P."vicw C 27, 1647 H. W. Baer. J. D. Bowman, M. D. Cooper, M. Leitch, A. (1983). Erell, J. Comuzzi, R. P. Redwine, and D. R. Tieger, "Inclusive Pion Single-Charge-Exchange Reactions," EXP. 31 Physical Review C 30, 946 (1984). J. S. Frank. R. L. Burman. D. R. F. Cochran, P. Nemethy, S. E. Willis, V. W. Hughes, R. P. Redwine, J. EXPS. 310,448,777,849 Duclos, H. Kaspar, C. K. Hargrove, and U. Moser, S. J. Greene. C. J. Harvey, P. A. Seidl, R. Gilman, E. R. "Reply to Direct Comparison Between the y-Ray Fluxes Siciliano, and Mikkel B. Johnson, "A Unified Analysis from Proton Beam Dumps at LAMPFand SIN," Physi- of Pion Single- and Double-Charge-Exchange Scattering cal Review D 28, 1790 (1983). in the Resonance Region," Los Alamos National Labo- ratory document LA-UR-84-2030 (1984), Physical Re- EXP. 32 view C(in press). F. C. Gaille. V. L. Highland, L. B. Auerbach, W. K.. McFarlane, G. E. Hogan, C. M. Hoffman, R. J. Macek. EXPS. 317,368,498 R. E. Morgado, J. C. Pratt, and R. D. Werbeck, "Precise W. B. Couingame, K. G. Boyer. W. J. Braithwaite, S. J. Measurement of the Pion Charge-Exchange Forward Greene, C. J. Harvey, R. J. Joseph, D. B. Holtkamp, C. Differential Cross Section at 522 MeV/c." Physical Re- F. Moore, J. J. Kraushaar, R. J. Peterson, R. A. Ristinen, view 0 30,2408(1984). J. R. Shepard, G. R. Smith, R. L. Boudrie, N. S. P. King, 180 PROGRESS AT LAMPF—1984

C. L. Morris, J. Piffaretti. and H. A. Thiessen, "Inelastic Morris, and K. Jones, "Excitation of E2 Transitions in Pion Scattering from i:C," Los Alamos National Labo- J"Ca by 334-McV Protons," Physical Review C 30, 709 ratory document LA-UR-84-2506 (1984), submitted to (1984). Physical Review C. EXP. 400 EXP. 349 R. D. Bolton, J. D. Bowman, R. Carlini, M. D. Cooper, Y. Ohkubo, N. T. Porile, C. J. Orth, and L, C. Liu, M. Duong-van, J. S. Frank, A. L. Hallin, P. Heusi, C. M. "Excitation Functions of the '-7I{it,7tvii) Reactions in the Hoffman, F. G. Mariam, H. S. Matis, R. E. Mischkc, D. Region of the (3,3) Resonance," Physical Review C 27, E. Nagle, V. D. Sandbcrg, G. H. Sanders, U. Scnnhauscr, 1146(1983). R. L. Talaga, R. Werbeck, R. A. Williams, S. L. Wilson, E. B. Hughes, R. Hofstadter, D. Grosnick, S. C. Wright, Exi-s. 368,539 G. E. Hogan, and V. L. Highland, "Search for the Muon- J. A, Carr. F. Petrovich. D. Halderson, D. B. Holtkamp, Number-Nonconserving Decay u •* <'W," Physical and W. B. Cottingame, "Stretched Excitations and the Review Letters 53, 1415 (1984).' Spin-Dependent Part of the Pion-Nucleon Interaction," Physical Review C 27, 1636(1983). EXP. 400 R. Bolton, R. Carlini. J. Bowman, M. Cooper, A. Hallin, EXP. 369 J. Frank. C. Hoffma.i, H. Matis, R. Mischke, D. Naglc, C. L. Blilic, D. Dehnhard, M. A. Franey, D. H. Gay, D. F. Mariam, V. Sandberg, U. Scnnhauscr, G. Sanders, R. B. Holtkamp, S. J. Seestrom-Morris, P. J. Ellis, C. L. Morris, and D. J. MiUcncr, "Isospin Structure of Trans- Werbeck, R. Williams, R. Hofstadter, E. Hughes, S. itions in 17O from Inelastic Pion Scattering at 164 MeV," Wilson, J. Rolfc, S. Wright, D. Grosnick, G. Hogan, V. submitted to Physical Review C. Highland, and M. D. Van, "The Crystal Box: Rare Decays of the Muon," Proceedings of the Conference on Exi>s. 375,571 Low Energy Tests of Conservation Laws in Particle M. E. Schillaci. C. Boekema, R. H. Heffner, R. L. Physics. Blacksburg, Virginia (1983). A1P Conference Hutson, M. Leon. C. E. Olson, S. A. Dodds, D. E. Proceedings No. 114, Particles and Fields Subserics No. MacLaughlin, and P. M. Richards, "Muon Diffusion in 33 (American Institute of Physics, New York, 1984), pp. Noble Metals," in Electronic Structure and Properties of 242-243. Hydrogen in Metals, P. Jena and C. B. Satterthwaite, Eds. (Plenum. New York, 1983), pp. 507-512. EXP. 400 A. L. Hallin, R. D. Bolton, J. D. Bowman, M. Duong- EXPS. 375,571 van. J. S. Frank, P. A. Heusi. C. M. Hoffman, G. E. M. E. Schillaci, R. H. Heffner. R. L. Hutson. M. Leon, Hogan. F. Mariam, H. Matis. R. E. Mischke. D. E. D. W. Cooke, A. Yaouanc. S. A. Dodds, P. M. Richards, Nagle. V. D. Sandberg, G. H. Sanders. U. Sennhauser, D. E. MacLaughlin, and C. Boekema, "Magnetic Field R. Talaga, R. D. Werbeck, R. A. Williams, S. L Wilson, Dependence of Impurity-Induced Muon Depolarization E. B. Hughes. R. Hofstadter. D. Grosnick. S. C. Wright, in Noble Metals," Hvperfine Interactions 17-19, 351 and V. L. Highland, "The Los Alamos Crystal Box (1984). Experiment: A Search for u •+ dy. u -»cy-j, and u •* cee" to be published in the AIP Conference Proceedings on the EXP. 392 M. L. Bariett. G. W. Hoffmann. J. A. McGill, R. W. Intersections Between Particle and Nuclear Physics, Fcrgcrson, L. C. Milner, J. A. Marshall. J. F. Amann, B. Steamboat Springs, Colorado. May 23-30. 1984, Los E. Bonncr, and J. B. McClelland, "Forward-Angle Alamos National Laboratory document LA- Elastic/5/i Spin-Depolarization and -Rotation UR-84-2130. Parameters at 0.8 GeV." Physical Review C 30, 279 EXP. 400 (1984). V. D. Sandberg, L. Bayliss. M. Dugan. J. S. Frank. T. Gordon, G. Han, C. M. Hoffman. G. E. Hogan. H. S. EXP. 392 J. A. Marshall. "A Measurement of the Wolfenstein Matis. G. H. Sanders, and H. P. von Gunten. "A Fast Parameters for Proton-Proton and Proton-Neutron Analog Mean-Timer," Los Alamos National Laboratory Scattering at 500 MeV.'" Ph.D. Thesis, University of document LA-UR-84-2019, to be published in Nuclear Texas, Austin. Los Alamos National Laboratory report Instruments & Methods. LA-10171-T (July 1984). EXP. 401 EXP. 399 M. D. Cooper. H. W. Baer. R. Bolton. J. D. Bowman, F. D. J. Horen. F. E. Bertrand, E. E. Gross. T. P. Sjoreen. Cverna. N. S. P. King, M. Lcitch, J. Alster, A. Doron, A. Erell, M. A. Moinestcr, E. Blackmore, and E. R. D. K. McDaniels, J. R. Tinsley. J. Lisantti. L. W. 15 + l5 Swersson. J. B. McClelland. T. A. Carey. S. J. Seestrom- Siciliano. "Angular Distribution for N(Tt ,ji") O(g.s.) PUBLICATIONS 181 at 7; = 48 MeV," Physical Review Letters 52, 1100 Exi\ 427 (1984). T. L. Estle, "Some Simple Thoughts About the Structure of Anomalous Muonium," llyperjine Interactions Exes. 401,404,607 17-19,585(1984). J. D. Bowman and M. D. Cooper, "Pion Charge Ex- change and Nuclear Structure," Los Alamos National Exi\ 427 Laboratory document LA-UR-83-3097 (1983), Com- T. L. Estle. K. W. Blazey, C. Boekema. and R. H. ments on Nuclcur and Particle Phvsics 12, 299-310 Heffner, "Muon Spin Rotation Experiments on a L1 (1984). Silicon Crystal Doped with C7' IIyperilne Interactions 1719,615(1984). Exi>. 404 J. A. Faucctt, B. E. Wood, D. K. McDaniels. P. A. M. Exv. 427 Gram, M. E. Hamm, M. A. Oothoudt. C. A. Goulding, T. L. Estle and D. A. Vanderwater, "Theory of Double L. \V. Swenson. K. S. Krane. A. W. Stetz. H. S. Plcndl, J. Eleclron-Muon Resonance." Physical Review li 27, Nonon, H. Funsicn. and D. Joyce, "Kinematically 3962(1983). Complete Measurement of the (n-,n'p) Reaction on i:C Exi\ 427 at 220 MeV." Physical Review C30, 1622 (1984). T. L. Estle. M. E. Warren. C. Bockema. and R. H. Exi\ 407 Heffner. "Low Frequency Double Electron Muon Reso- D. .1. Farnum, W. F. Sommer. and O. T. Inal, "A Study nance (DEMUR) in Fused Quartz." llyperline Interac- of Defects Produced in Tungsten by 800-MeV Protons tions 17-19, 575 (1984). Using Field Ion Microscopy," Journal of Nuclear E\RS. 432,531 Materials 122-123, 996-1001 (1984). K. W. Jones. "Elastic and Inelastic Scattering of Exi\ 112 Polarized Protons from Carbon-12 at 400. 600. and 700 N. Auerbach, M. B. Johnson. A. Klein, and E. Siciliano. MeV." Ph.D. Thesis. Rutgers University. Los Alamos "Nuclear Structure Effects in Pion Single-Charge Ex- National Laboratory report LA-10064-T (April 1984). change." Physical Review C 29, 526 (1984). Exi-s. 432,531 Exi\ 412 K. W. Jones. C. Glashausser, S. Nanda. R. de D. B. Holtkamp, S. J. Seestrom-Morris. D. Dehnhard. Swiniarski. T. A. Carey. W. Cornelius. J. M. Moss. .1. B. H. W. Baer, C. L. Morris. S. J. Greene, C. J. Harvey. D. McClelland. S. J. Secstrom-Morris. J. R. Comfort. J.-L. Kurath. and J. A. Carr. "Pion Scattering to 4 States in Escudie. M. Gazzaly. N. Hintz. G. Igo. M. Haji-Saeid. UC." Los Alamos National Laboratory document LA- and C. A. Whitlcn. -'Study of the 18.30 and 19.40 MeV UR-84-2055. submitted to Physical Review C. Slates in 'C in Intermediate Energy Proton Scattering." Physics Letters 128B. 281 (1983). Exrs. 412,607 H. W. Bacr. "Study of Giant Resonances with Pions." Exes. 465, 548 presented at the International Symposium on Nuclear R. S. Rundberg. B. .1. Dropesky. G. C. Giesler. G. W. Spectroscopy and Nuclear Interactions. Osaka Univer- Butler. S. B. Kaufman, and E. P. Steinberg. "Excitation sity, Osaka. Japan. March 21-24. 1984. Los Alamos Functions of Pion Single Charge Exchange Reactions in National Laboratory document LA-UR-84-1293. "Al. '-Sc. and "T'u." Physical Review CM), 1597 (1984). Exi-s. 412,607 Exi>. 470 A. Erell. J. Alster. .1. Lichtcnstadi. M. A. Moinester. .1. D. J. A. McGill. G. W. Hoffmann. M. L. Barlett. R. W. Bowman. M. D. Cooper. F. Irom. H. S. Matis. E. Fergcrson. E. C. Milner. R. E. Clirien. R. .1. Sutter. T. Piasetzky. U. Sennhauser. and Q. Ingram. "Properties Kozlowski. and R. L. Slearns. "Proton + Nucleus In- of the Isovecior Monopole and Other Giant Resonances clusive (/»./»') Scattering al 8(10 MeV." Physical Review C in Pion Charge Exchange."" Physical Review Let ten 52, 29.204(1984). 2134(1984). F.xi'. 492 EXF. 427 C. L. Hollas. D. J. (remans. R. D. Ransome. P. .1. Riley. C. Boekcma. "Some Characteristics of Muun Stales in B. E. Bonner. M. VV. McNaughu.n. and S. Wood. "The Silicon." Philosophical Miixuzme B47, 331 (1983). Energy Dependence of the 90' pp Elastic Scattering Depolarization Parameter and Amplitudes Between (1.9 Exi\ 427 and 1.5 GeV/e." Physics Letters 143B, 343 (1984). J. A. Brown. R. H. Hcffner. M. Leon. S. A. Dodds. T. L. Estle. and D. A. Vanderwater. "Double Electron-Muon EXP. 492 Resonance Experiments on Muonium in Quail/." M. W. McNaughton. B. E. Bonner. O. B. van Dyck. S. Physical Review li 27, 3980 (1983). Tsu-Hsun. H. Ohnuma. C. L. Hollas. D. .1. Cremans. 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H. McNaughton, P, J. Riley. R. F. Rodebaugh, Shcn- txp. 499 Wu Xu, S. E. Turpin, B. Aas. and G. S. Weston, "Thep- R. H. Heffner, M. Leon, M. E. Schillaci, D. E. C Analyzing Power Between 100 and 750 MeV," Los MacLaughlin. and S. A. Dodds, "Muon Spin Relaxation Alamos National Laboratory document LA-UR-85-392, Measurements of the Fluctuation Modes in Spin-Glass submitted to Nuclear Instruments & Methods, •igMn," Journal of Magnetism and Magnetic Materials 31-34,1363(1983). EXP. 495 C. L. Morris, N. Tanaka, R. L. Boudrie, L. C. Bland, H. EXP. 499 T. Fortune, R. Gilman, S. J. Seestrom-Morris, C. F. R. H. Heffner and D. E. MacLaughlin, "Comparison of Moore, and D. Dehnhard, "Small Angle Pion Inelastic Spin-Glass Dynamics Determined by the Muon-Spin- Scattering from i:Cat 162 MeV," Physical Review C 30, Relaxation and Neutron Spin-Echo Techniques," Physi- 662(1984). cal Review B 29, 6048 (1984).

EXP. 498 EXP. 499 I. P. Auer, W. R. Ditzler, D. Hill. K. Imai, H. Spinka, R. D. E. MacLaughlin, L. C. Gupta, D. W. Cooke, R. H. Stanek. K. Toshioka, D. Underwood. R. Wagner, A. Heffner, M. Leon, and M. E. Schillaci, "Evidence for Yokosawa, E. W. Hoffman, J. J. Jarmer, G. R. Burleson, PowiT-Law Spin-Correlation Decay from Muon Spin W. B. Coliingame, S. J. Greene, and S. Stuart, "Meas- Relaxation in AgMn Spin-Glass." Physical Review Let- urement of Aa/. and Cu. ~ 85:0,0) in Proton-Proton ters 51,927 (1983). Scattering Between 300 and 800 MeV," Physical Review EXP. 512 D 29, 2435 (1984). W. R. Ditzler, D. Hill, K. Imai, H. Shimizu, H. Spinka, EXP. 499 R. Stanek, K. Toshioka, D. Underwood, R. Wagner, A. S. A. Dodds, G. A. Gist, R. H. Heffner, M. Leon, D. E. Yokosawa, G. R. Burleson. W. B. Cottingame, S. J. MacLaughlin. J. A. Mydosh. G. J. Nieuwenhuys. and M. Greene, J. J. Jarmer, and R. H. Jeppeson, "Measure- E. Schillaci. "Muon Spin Relaxation in Ferromagnetic ments of the Spin-Spin Correlation Parameter Css = ft/Mn," Hyperjine Interactions 17-19,467 (1984). (S.S-,0,0) at 487, 639, and 791 MeV." Physical Review D 29,2137(1984). EXP. 499 S. A. Dodds, G. A. Gist. D. E. MacLaughlin. R. H. EXP. 517 Heffner, M. Leon, M. E. Schillaci, G. J. Nieuwenhuys, G. Glass, T. S. Bhatia, J. C. Hiebert. R. A. Kenefick. L. and J. A. Mydosh, "Muon Spin Relaxation in a Random C. Northcliffe. W. B. Tippens, J. G. J. Boissevain, .1. J. Ferromagnet: ft/Mn." Physical Review B 28, 6209 Jarmer. J. E. Simmons, D. H. Fitzgerald. J. Holt. A. (1983). Mokhlari, and G. E. Tripard, "Measurements of Spin- Correlation Parameter .-1\\ and Analyzing Power at 90° EXP. 499 1 for /;pillppoi - dit Between 500 and 800 MeV." Physical G. A. Gist and S. A. Dodds. "Zero-Field Muon-Spin- Review Letters 53, 1984 (1984). Resonance Linewidths in Dilute Magnetic Alloys," Physical Review B 30, 2340 (1984). F\p. 518 G. Glass. T. S. Bhatia, J. C. Hiebert, R. A. Kenefick. S. EXP. 499 Nath, L. C. Northcliffe, W. B. Tippens, D. B. Barlow. A. R. H. Heffner. D. W. Cooke. M. Leon. M. E. Schillaci, Saha, K. K. Seth, J. G..!. Boissevain, J. J. Jarmer. J. E. D. E. MacLaughlin. and L. C. Gupta, "Muon Spin Simmons. R. H. Jeppesen. and G. E. Tripard, Relaxation Measurements of Spin-Correlation Decay in "Measurements of Spin-Correlation Parameters .1;, Spin-Glass . l,?Mn." Hvperfine Interactions 17-19, 463 and .-l.sv. for/jp -» n.d Between 500 and 800 MeV." (1984). Physical Review C 31, 288 (1985). EXP. 499 EXPS. 522,625 R. H. HelTner. M. Leon, and D. E. MacLaughlin, "Spin- J. L. Ullmann, J. J. Kraushaar. T. G. Mastcrson, R. j. Glass Dynamics Determined from Muon Spin Relaxa- tion and Neutron Spin Echo Measurements." Hyperfme Peterson. R. S. Raymond. R. A. Ristinen, N. S. P. King, Interactions 17-19, 457 (1984). R. L. Boudrie. C. L. Morris. R. E. Anderson, and E. R. Siciliano, "Pion Inelastic Scattering to Giant Re- EXP. 499 sonances and Low-Lying Collective States in 1!SSn and R. H. Heffner, M. Leon. M. E. Schillaci. S. A. Dodds. G. 4"Ca," Physical Review C 31, 177 (1985). A. Gist. D. A. MacLaughlin. J. A. Mydosh, and G. J. EXP. 539 Nieuwenhuys. "Muon Spin Relaxation in Spin Glass Pc/Mn." Journal of Applied Physics 55, 1703 (1984). C. J. Harvey. H. W. Baer, J. A. Johnstone. C. Morris, S. J. Seestrom-Morris, D. Dehnhard, D. B. Holtkamp, and PUBLICATIONS 183

U S. J. Greene, "Elastic it"* and n Scattering on C at 164 EXP. 561 MeV," Los Alamos National Laboratory document LA- M. J. Leitch, R. L. Burman, R. Carlini, S. Dam, V. UR-84-2433 (1984), submitted to Physical Review C. Sandbcrg, M. Blechcr, K. Gotow, R. Ng, R. Auble, F. E. Bertrand, E. E. Gross, F. E. Obenshain. J. Wu, G. S. EXPS. 539,622 Blanpied, B. M. Preedom, B. G. Ritchie, W. Bertozzi, C. J. Harvey, H. W. Baer, R. L. Boudrie, C. L. Morris, D. M. V. Hynes. M. A. Kovash, and R. P. Redwine, "Pion- B. Holtkainp, and S. J. Greene, "Elastic and Inelastic + Nuclcus Elastic Scattering at 80 MeV," Physical Review Scattering of rc and JT from '-C Near the A3, Reso- C 29, 561 (1984). nance," Los Alamos National Laboratory document LA-UR-84-1732 (1984), submitted to Physical Review EXP. 567 C. B. G. Ritchie, G. S. Blanpied, R. S. Moore, B. M. Preedom, K. Gotow, R. C. Minehart, J. Boswell, G. Das, EXPS. 540,583 H. J. Ziock, N. S. Chant, P. G. Roos, W. J. Burger, S. G. S. Weston, "Elastic Scattering of Polarized Protons Gilad, and R. P. Redwine, "Reaction n+ + il-d + pat 65 on Deuterium at 800 MeV," Ph.D. Thesis, University of to 140 MeV," Physical Review C 27, 1685 (1983). California, Los Angeles, Los Alamos National Labora- tory report LA-10174-T (July 1984). EXP. 572 C. L. Morris, S. J. Greene. R. Gilman, H. T. Fortune, J. Exp. 543 D. Zumbro, J. A. Faucett, G. R. Burleson. K. S. Dhuga, N. T. Porile, A. A. Caretto, B. J. Dropesky, C. J. Orth. L. P. A. Seidl, S. Mordechai, and C. F. Moore, "Properties C. Liu, and G. C. Giesler, "Recoil Measurement of the i: z of the ™Po(O\r= 22) Double Isobaric Analog Reso- C(Tt .7tA0"C Reaction Between 90 and 350 MeV." nance," Los Alamos National Laboratory document Physical Review C 29, 2239 (1984). LA-UR-84-3900 (1984). submitted to Physical Review EXP. 545 Letters. R. D. Brown, J. R. Cost, and J. T. Stanley, "Irradiation- Induceci Decay of Magnetic Permeability of MetGlas EXP. 580 S. J. Seestrom-Morris, M. A. Franey. D. Dehnhard, D. 2605S-3," Los Alamos National Laboratory document B. Holtkamp, R. L. Boudrie. J. F. Amann, G. C. LA-UR-84-875 (1984). Journal of Nuclear Materials (in |1 11 idzorek. and C. A. Goulding, " C(p.//) C* Reaction at press). '/;, = 547 MeV," Physical Review C 30, 270 (1984). EXP. 546 B M. K. Netkens. W. J. Briscoe, A. D. Eichon. D. H. EXP. 581 Fitzgerald, J. A. Holt, A. A. Mokhtari. J. A. Wightman. T. G. Masterson, J. J. Kraushaar. R. J. Peterson, R. S. M. E. Sadler, R. L. Boudrie. and C. L. Morris, "Test of Raymond, R. / . Ristinen, J. L. Ullmann. R. L. Boudrie, Charge Symmetry in 7tt and iC Elastic Scattering on D. R. Gill, E. F. Gibson, and A. W. Thomas, "Charge Tritium and 'He." Physical Review Letters 52, 735 Symmetry in Pion-Deuteron Elastic Scattering," Physi- (1984). cal Review C 30, 20\0 {1984). EXP. 587 EXP. 558 P. A. Seidl, M. D. Brown. R. R. Kiziah. C. F. Moore. H. T. Bergcman, C. Harvey, K. B. Builcrfield. H. C. Bryant, Baer. C. L. Morris, G. R. Burleson, W. B. Cottingame, S. D. A. Clark, P. A. M. Gram. D. MacArthur. M. Davis, J. B. Donahue, .1. Dayton, and W. W. Smith. "Shape J. Greene. L. C. Bland. R. Gilman. and H. T. Fortune. Resonances in the Hydrogen Stark Effect in Fields up to "Pion Double Charge Exchange on T = 1 Nuclei." 3 MV/cm." Physical Review Letters 53, 775(1984). Physical Review C 30, 973 (1984). EXP. 595 EXP. 558 Y. Ohkubo, C. J. Orth. D. ). Vicira. and L. C. Liu, "The P. A. Seidl. M. D. Brown. R. R. Kiziah. C. F. Moore, H. 41< Baer. C. L. Morris. G. R. Buiieson. W. B. Cottingame. S. (7t,7t/V) Reaction in Ca." Physical Review C 31, 510 J. Greene, L. C. Bland, R. Gilman. and H. T. Fortune. (1985). ""C(7i\7r )"O Near the A,, Resonance." Physical Re- EXPS. 598,746 view C 30. 1076(1984). R. R. Kiziah, M. D. Brown, C. J. Harvey, D. S. Oakley, EXP. 559 D. P. Saunders. P. A. Seidl, C. F. Moore, W. B. Cot- G. C. Phillips. E. A. Umland, G. S. Mutchler, J. B. tingame. R. W. Garnett, S. J. Greene, G. A. Luna, G. R. Roberts. M. Duong-van. J. A. Buchanan. J. B. Donahue. Burleson. and D. B. Holtkamp. "Pion Inelastic Scatter- J. C. Allred. B. W. Noel. T. A. Mulera, Bjorne Aas, and ing to the Low-Lying Excited States of ''Li," Physical Review C 30, 1643(1984). B. W. Mayes. "A Novel Neutrino Detection System." Suclear Instruments & Methods 221, 334-346 (1984). 184 PROGRESS AT LAMPF—1984

EXPS. 598,746 McNaughton, H. Ohnuma, O. B. van Dyck, S. Tsu- R. R. Kiziah, "Pion Inelastic Scattering to the First Hsun. S. E. Turpin, B. Aas, and G. S. Weston, "D.vv, DLL, Three Excited States of Lithium-6," Ph.D. Thesis, Air Av;.. DiA and P for pp * pp at 600 to 800 MeV," Physical Force Weapons Laboratory, Kirtland Air Force Base, Review CM, 1251 (1984). Los Alamos National Laboratory report LA-1O257-T EXP. 639 (October 1984). C. Boekema, "Muon Hyperfine Interactions in Magne- EXP. 616 tic Oxides," Hyperfine Interactions 17-19, 305 (1984). J. B. McClelland, J. M. Moss, B. Aas, A. Azizi, E. EXP. 639 Bleszynski, M. Bleszynski, J. Geaga, G. Igo, A. Rahbar, C. Boekema, V. A. M. Brabers, A. B. Denison, R. H. J. B. Wagner, G. S. Weston, C. Whitten, Jr., K. Jones, S. Heffner, R. L. Hutson, M. Leon, C. E. Olsen, and M. E. Nanda, M. Gazzaly, and N. Hintz, "Complete Measure- Schillaci, "Muon Spin Rotation Study on Magnetite," ment of Polarization-Transfer Observables for the Re- l2 r Journal of Magnetism and Magnetic Materials 31-34, action C(p,p') -C* at 500 MeV." Physical Review Let- 709(1983). ters 52,98 (1984). EXP. 639 EXP. 617 C. Boekema, A. B. Denison, and K. J. Riiegg, "Muon H. J. Ziock, C. Morris, G. Das, J. R. Hurd, R. C. ++ Spin Rotation in Antiferromagnetic Oxides," Journal of Mvnehart, L. Orphanos, and K.. O. H. Ziock, "A Magnetism and Magnetic Materials 36, 111 (1983). Resonance in a " B Nucleus," Physical Review C 30,650 (1984). EXP. 639 C. Boekema, A. B. Denison, D. W. Cooke, R. H. Hef- EXP. 626 fner, R. L. Hutson, M. Leon, and M. E. Schillaci, J. A. McGill, C. Glashausser, K. Jones, S. K. Nanda, M. "Hyperfine Field Calculations: Search for Muon Stop- Barlett, R. Fergerson, J. A. Marshall, E. C. Milner, and r ping Sites in Fe.iOj," Hvperfine Interactions 15-16, 529 G. W. Hoffmann, "Inclusive (p,p ) Cross Sections and (1983). Analyzing Powers for 'H and [2C in the Delta Region," Physics Letters I34B, 157(1984). EXP. 639 C. Boekema. R. L. Lichti, V. A. M. Brabers, A. B. EXP. 630 Denison. D. W.Cooke. R. H. Heffner. R. L. Hutson, M. S. K. Nanda, C. Glashausser, K. W. Jones, J. A. McGill, Leon, and M. E. Schillaci, "Magnetic Interactions, T. A. Carey, J. B. McClelland, J. M. Moss, S. J. Bonding, and Motion of Positive Muons in Magnetite," Seestrom-Morris, J. R. Comfort, S. Levenson, R. Segel, Physical Review B 31, 1233 (1985). and H. Ohnuma, "10.23 MeV Ml Transition in the 48Ca(/5,p)4SCa* Reaction at 319 MeV," Physical Review EXP. 640 C 29, 660 (1984). R. H. Heffner. D. W. Cooke, R. L. Hutson, M. Leon, M. E. Schillaci, J. L. Smith, A. Yaouanc, S. A. Dodds, L. C. EXP. 634 Gupta, D. E. MacLaughlin, and C. Boekema, "Effects of R. W. Harper, V. Yuan, H. Frauenfelder, J. D. Bowman, Superconductivity on Rare-Earth Ion Dynamics in R. Carlini, R. E. Mischke, D. E. Nagle, R. L. Talaga, and (Ho.vLui -vRh4B4," Journal of Applied Physics 55, 2007 A. B. McDonald, "Parity Nonconservation in Proton- (1984). Water Scattering at 1.5 GeV/c," Physical Review D 31, 1151(1985). EXP. 640 D. E. MacLaughlin. S. A. Dodds, C. Boekema, R. H. EXP 635 Heffner, R. L. Hutson, M. Leon, M. E. Schillaci, and J. S. Tsu-Hsun. B. E. Bonner, M. W. McNaughton. O. B. L. Smith, "Muon Spin Relaxation Mechanisms in van Dyck, G. S. Weston, B. Aas. E. Bleszynski. M. Ternary Rare-Earth Rhodium Borides." Journal of Bleszynski, G. J. Igo, H. Ohnuma, D. J. Cremans, C. L. Magnetism and Magnetic Materials 31-34,497 (1983). Hollas, K. H. McNaughton. P. J. Riley, R. F. Rodebaugh, S.-W. Xu, and S. E. Turpin, "Measure- EXPS. 655,659 ments of the Spin-Rotation Parameters fororf -*~pd L. C. Bland. R. Gilman. G. S. Stephans. G. P. Gilfoyle, Elastic Scattering at 496, 647, and 800 MeV," Los H. T. Fortune, C. L. Morris. S. J. Seestrom-Morris, S. J. Alamos National Laboratory document LA- Greene, P. A. Seidl. R. R. Kiziah, and C. F. Moore, UR-83-3484 (1983), Physical Review C (in press). "Forward-Peaked Angular Distributions Observed in (7i,7i') on Light Nuclei," Physics Letters 144B, 328 EXP. 636 (1984). C. L. Hollas, D. J. Cremans, K. H. McNaughton. P. J. Riley. R. F. Rodebaugh. S.-W. Xu, B. E. Bonner. M. W. PUBLICATIONS 185

EXP. 672 at the ACS Division of Nuclear Chemistry and Tech- S. J. Seestrom-Morris, C. L. Morris, J. M, Moss, T. A. nology meeting, St. Louis, Missouri, April 8-13, 1984, Carey, D. Drake, J.-C. Dousse, L. C. Bland, and G. S. Los Alamos National Laboratory document LA- Adams, "Measurement of \K+/K~ Cross Section Ratio UR-83-3140. for the Giant Quadrupole Resonance in :0!tPb," Los Alamos National Laboratory document LA- EXP. 741 UR-84-3814 (1984), submitted to Physical Review Let- T. A. Carey, K. W. Jones, J. B. McClelland, J. M. Moss, ters. L. B. Rees, N. Tanaka, and A. D. Bacher, "Complete Polarization Transfer Measurements in Inclusive EXP. 698 Proton Scattering from Deuterium and Pb and the EMC Y. Tanaka, R. M. Steffen, E. B. Shera, W. Reuter, M. V. Effect," Physical Review Letters 53, 144 (1984). Hoehn, and J. D. Zumbro, "Measurement and Analysis |7M7? l7!i |7g IS EXPS. 741,741U of Muonic X Rays of "Hf," Physical Review C30, 350 (1984). T. A. Carey, K. W. Jones, J. B. McClelland, J. M. Moss, L. B. Rees. N. Tanaka, and A. D. Bacher, "Inclusive E ,\ 698 Scattering of 500-MeV Protons and Pionic Enhance- Y. Tanaka, R. M. Steffen, E. B. Shera, W. Reuter. M. V. ment of the Nuclear Sea-Quark Distribution," Physical Hoehn, and J. D. Zumbro, "Measurement and Analysis Review Letters 53, 144 (1984). of the Muonic X Rays of l5lEu and l5AEu." Physical Review C 29, 1897(1984). ° EXP. 745 J. D. Zumbro, E. B. Shera, Y. Tanaka, C. E. Bemis, Jr., EXP. 698 R. A. Naumann, M. V. Hoehn, W. Reuter, and R. M. Y. Tanaka, R. M. Steffen, E. B. Shera, W. Reuter, M. V. Steffen, "E2 and E4 Deformations in ^-^.IS.IJS^" Hoehn, and J. D. Zumbro, "Systematics of Ground- Physical Review Letters 53, 1888 (1984). State Quadrupole Moments of Odd-.-l Deformed Nuclei Determined with Muonic A/ X Rays," Physical Renew EXP. 749 C 29, 1830(1984). S. J. Greene, W. B. Cottingame, G. R. Burleson, L. C. Bland, R. Gilman, H. T. Fortune, C. L. Morris, D. B. EXP. 701 Holtkamp, and C. F. Moore, "Dim-active Angular Dis- C. L. Morris, "Pion Induced Double Charge Exchange tribution for l('O(jt+,7u^)l6Ne(g.s.)," Physical Review C and Delias in Nuclei," invited talk presented at the 1983 27,2375(1983). Annual Meeting of the APS and the American Associa- tion of Physics Teachers, New York, January 24-27, EXPS. 749,780 1983, Los Alamos National Laboratory document LA- R. Gilman. H. T. Fortune, L. C. Bland, R. R. ICiziah. C. UR-82-3222. F. Moore, P. A. Seidl, C. L. Morris, and W. B. Cot- tingame, "Nonanalog (n",7t+) Double Charge Exchange IS EXP. 703 on O," Physical Review C 30, 962 (1984). S. J. Seestrom-Morris, D. Dehnhard, C. L. Morris, L. C. Bland. R. Gilman. H. T. Fortune. D. J. Millener, D. P. EXPS. 777,849 Saunders, P. A. Seidl. R. R. Kiziah, and C. F. Moore, P. A. Seidl, C. F. Moore, S. Mordechai, R. Gilman, K. S. "M4 Transitions Observed in Pion Inelastic Scattering Dhuga, H. T. Fortune, J. D. Zumbro, C. L. Morris, J. A. I? Faucett, and G. R. Burleson, "The Energy Dependence on N." Los Alamos National Laboratory document lll + ill LA-UR-84-3367 (1984), submitted to Physical Review of O(7t ,7c^) Ne(g.s.)," Los Alamos National Labora- C. tory document LA-UR-84-3373 (1984), submitted to Physical Review Letters. EXP. 727 n M. Leon, "Resonant Mesomolecule Formation in EXP. 778 Muon-Catalyzed cl-l Fusion." Physical Review Letters D. Dehnhard, D. H. Gay, C. L. Blilie. S. J. Seestrom- 52,605(1984). Morris, M. A. Franey, C. L. Morris, R. L. Boudrie, T. S. Bhatia, C. F. Moore, L. C. Bland, and H. Ohnuma, EXP. 727 "Excitation of the lf State in 4SCa (10.1 MeV) by In- M. Leon and James S. Cohen, "Ortho- and elastic Scattering of 7t~ and TC4," Physical Review C 30, Paradeuterium Effects in Muon-Catalyzed Fusion " Los 242(1984). Alamos National Laboratory document LA- UR-84-2689, submitted to Physics Letters A. EXP. 780 R. Gilman, H. T. Fortune, L. C. Bland, R. R. Kiziah, C. EXP. 730 F. Moore, P. A. Seidl, C. L. Morris, and W. B. Cot- B. J. Dropesky. S. Yan. L.-C. Liu. R. Bhalerao. and G. C. lingame, "l4Be via Pion Double Charge Exchange," Giesler. "Single Pion Production by Pions," presented Physical Review C 30, 958 (1984). 186 PROGRESS AT LAMPF—1984

EXP. 783 EXP. 834 E. Piasetzky, P. A. M. Gram, D. W. MacArthur, G. A. Y. Tanaka, R. M. Steffen, E. B. Shera, W. Reuter, M. V. Rebka, Jr., C. A. Bordner, S. Hoibraten, E. R. Kinney, J. Hoehn. and J. D. Zumbro, "Pionic M X-Rays ofIWl l6ltEr L. Matthews, S. A. Wood, D. Ashery, and ,1. and 17('Hf," Physics Letters I43B, 347 (1984). Lichtenstadt, "Pion-lnduced Pion Production on the Deuteron," Physical Review Letters 53, 540 (1984), EXP. 858 R. Gilman, H. T. Fortune, K. S. Dhuga, P. H. Kutl, L, C. EXP. 791 Bland, R. R. Kiziah, C. F. Moore, P. A. Seidl, C. L. D. F. Geesaman, R. D. Lawson, B. Zeidman, G. C. Morris, and W. B. Cottingame, "Energy Dependence of Morrison, A. D. Bacher, C. Olmer, G. R. Burleson, W. Angular Distributions in the Nonanalog Pion Double B. Cottingame, S. J. Greene, R. L. Boudrie, C. L, Morris, Charge Exchange Reaction l(1O(7t+,7T)1"Ne(g.s.)," Physi- R. A. Lindgren, W. H. Kelly. R. E. Segel, and L. W. cal Review C 29, 2395 (1984). Swenson, "Quenching of Isoscalar Spin-Flip Strength in MFe," Physical Review C 30, 952 (1984). EXP. 869 A. Badertscher, S. Dhawan, P. O. Egan, V. W. Hughes, EXP. 796 D. C. Lu. M. W. Ritter, K. A. Woodle, M. Gladisch, H. K. K. Seth. M. Kaletka, S. Iversen, A. Saha, D. Barlow. Onh, G. zu Putlitz, M. Eckhause, J. Kane, F. G. D. Smith, and L. C. Liu, "Core-Excitation Effects in Mariam, and J. Reidy, "Formation of Muonium in the Pion Double Charge Exchange," Physical Review Let- 25 State and Observation of the Lamb Shift Transi- ters 52, 894 (1984). tion," Physical Review Letters 52, 914 (1984). INSTRUMENTATION AND COMPUTING

Clamshell Spectrometer end. The wire chambers, with each plane identical in R. Boudrie size and construction to those used at EPICS, are delay-line read-out drift chambers' in both The new low-energy pion spectrometer at the LEP coordinates and have an active area of 90 by 20 cm. channel was commissioned at the beginning of the To minimize the material thickness in the focal summer 1984 production period This device, using a plane, redundant chamber planes were not used; single dipole with a non-uniform field, is unique instead, the left-right ambiguity of the anode wires among pion spectrometers. In conventional non- was determined by differentiating the current pulses uniform spectrometers, the field is a function of the induced on the cathode field-defining wires, as de- distance from a central ray with radius R. In this scribed in Ref. 1. spectrometer (as well as in "orange-sector" beta spectrometers), the pole faces are planes with an air gap increasing along the particle trajectory, as shown in Fig. 1. The particles enter the air gap in a region of relatively high field, move into a region of lower field, and then leave after again passing a high-field region. The name of the spectrometer came about because \ the appearance of the pole pieces is similar to a clamshell. r The design of the Clamshell was dictated by these SECTION A A constraints: 1. The spectrometer must match the achromatic tune of the LEP channel, with • a horizontal spot size of ±15 mm, • a small achromatic vertical spot size, and • momentum resolution down to 0.15%. 2. It must have • a large solid angle (40 msr) and large momentum acceptance (±15%), possibly with degraded resolution up to ±30%: • a minimum pion flight path (therefore no quadrupoles or front chambers); and • a maximum central momentum of 200 McV/c (104-MeV pion energy). 3. It must provide large scattering angles up to 140°. The design allows for the spectrometer to move 30 cm farther back from the target to attain scattering angles between 100 and 140°. with a reduction in solid angle from 40 to 12 msr. The spectrometer is portable and can be physically installed and aligned in 1 day. Fiui'KE 1. Schematic view of the Clamshell spec- The focal plane was instrumented with two trigger trometer. scintillators (80 by 15 cm), with phototubes at each 187 188 PROGRESS AT LAMPF—1984

During the initial development period with beam, -etu. u t^° sliding-seal scattering chamber was not available, so :acuum windows were positioned at the channel -200.0 exit and the spectrometer entrance. An additional «C(ifW*' trigger scintillator in front of the spectrometer was g.s. T-jr-80 MeV -lao.o easily installed and greatly improved the trigger rate. The wire chambers were calibrated and then the 0.90' resolution was optimized,1 with vertical angle terms -160.0 up to second order allowed in the polynomial de- 1 scribing the outgoing pion momentum. A typical -140.0 missing-mass spectrum, shown in Fig. 2, includes the additional vacuum windows and a total of ~30 cm -120.0 of air before and after the target. It also includes the complete dngular acceptance of ±100 mrad in both -100.0 vertical and horizontal entrance angles. The resulting U— 600 KaV energy resolution at 80-MeV pion energy is 600 keV (0.5% momentum resolution). -BO.00 Both vertical and horizontal scattering angles were -60.00 calibrated. It is extremely important to know horizontal scattering angles because the kinematic 4.4 shift dp/dQ over the large angular acceptance of the -40.0.0 spectrometer is significant. This calibration was ac- 1 complished by using niasks as slits at the entrance of -20.00 the spectrometer and thin carbon rods as targets. Pions elastically scattered from the rod and colii- mated by a slit provide a well-determined scattering 5.0 0.0 5,0 10.0 angle. A set of these elastic events is matched with MISSiNG MASS (MeV) position and angle in the focal-plane wire chambers, and ihe scattering angle can then be fitted to a FIGURE 2. Missing-mass spectrum without vacuum coupling at the target. The incident polynomial in position and angle of the focal-plane positive pion energy is 80 MeV, the scattering quantities. Scattering angle resolutions in both the 2 angle is 90°, and the target is 230-mg/cm CH2. vertical and horizontal directions of 12 mrad rms were obtained over the complete ±100-mrad acceptance. with vacuum coupling. The spectrometer angle was After 2 weeks of development the scattering fixed at 30° to maintain a vacuum with the sliding- chamber still was not available. However, the first seal mechanism and the incident pion energy was approved experiment, JT* elasiic scattering at 50 and kept at 50 MeV. A bootstrap procedure (to tune the 65 MeV on 58-H)64Ni, did not need the best resolution. channel and reoptimize the spectrometer) produced Absolute cross sections were obtained out to scatter- resolution of 360 keV (0.4% in momentum), as ing angles of 120°. With a 1.6-mm trigger scintillator shown in Fig. 3. before the spectrometer, energy resolutions of less Efforts are under way to correct the problems with than 700 keV were obtained. the sliding-seal scattering chamber so that we can After this initial experiment, the scattering start on the long list of experiments. Development chamber became available. However, problems de- work during the summer will seek to improve back- veloped when the spectrometer and sliding seal ground rejection and to improve the momentum moved under vacuum. At the same time, a water leak resolution to 0.2%. To optimize the channel and developed in the LEP channel, limiting the max- spectrometer together, the 0° configuration will be imum pion energy to 50 MeV. A short development used. A low-intensity proton beam will be delivered period of 2 days was taken to optimize the resolution to Area A during development periods, and the full INSTRUMENTATION AND COMPUTING 189

Time-of-Flight Isochronous Spectrometer I2corr-.Tr*) -70.00 Los Alamos, Clark Univ., Iowa State Univ., Utah State 50 MeV Univ., Univ. ofGiessen J. M, Warners. D. J. Vieira, II. Wollmk*G. W. Butler. K. 30° -60.00 Vaziri**J. R. Sims. J. W. Van Dyke, D. C. Clark. J. R. Zerwekh. J. H. Gill. D. D. Kercher, andJ. D. Little

-50.00 Introduction This report is the second in a series of progress reports describing the design and construction of the -40.00 time-of-flight isochronous (TOFI) spectrometer and 360 KeV its associated secondary beam line. TOFI, which is being constructed jointly by INC and MP Divisions, -30.00 is designed to measure in a systematic fashion the ground-state masses of the light neutron-rich nuclei with A < 70 that lie far from the valley of (3 stability. -20.00 In the past year we ordered all the long-lead items necessary for construction of the spectrometer and installed the first half of the secondary beam line. -10.00 Furthermore, a major portion of the control system for both the spectrometer and beam line was designed and installed. This annual report briefly summarizes the current status of the spectrometer and describes 0.0 2.0 4.0 MISSING MASS (MeV) in some detail the design and installation of the first half of the transport line. For a summary of the FIGURE 3. Missing-mass spectrum with vacuum scientific goals and overall design of the TOFI spec- 1 coupling at the target. The incident positive pion trometer, see the 1983 Progress at LAMPF report. energy is 50 MeV, the scattering angle is 30", and the target is 228-mg/cm212C. Secondary-Beam-Transport Line In February we began installing the secondary- phase-space pion beam will be run directly through beam-transport line by unstacking the shield wall the spectrometer. between the LAMPF switchyard and the TOFI room. Since then, all of the optical and vacuum elements References have been installed, up to the first beam box in the TOFI room, and the wall has been restacked. The 1. C. L. Morris. Nuclear Instruments & Methods 196, optical and vacuum elements include a quadrupole 263(1982). triplet that captures a portion of the recoils from the 2. R. L. Boudrie et al., IEEE Transactions on Nuclear target, a mass filter that filters out the light, high- Science NS-26,4588 (1979). intensity reaction products (protons, deuterons, and alphas) produced in a variety of proton-induced reactions, and a final triplet that focuses the filtered beam down to a magnified image of the source. To

*Currcntly at the University of Giessen, Gcissen, West Germany. "Currently at Utah Stale University. 190 PROGRESS AT LAMPF—1984

characterize its operation, the first section of line has been tuned with various alpha sources and reaction products from 800-MeV protons on thorium. The tuning process is divided into three steps: 1. focusing the beam to obtain an image of the 400 source, 2. determining the transport line's energy- transmission window, and 3. characterizing the electrostatic defiector-dipole 200 magnet combination to determine its mass filtering ability. To focus the beam, a new multiwire proportional counter has been built that is position sensitive (0.05 cm FWHM for alpha particles) in both the .v (b) and y directions (see the following contribution in 300 this report by Vaziri et al.). A good image (1.0 by 1.4 cnr) was produced at the first focal point of the transport line from a :4'Am source (0.6 cm diameter) 200 located 30 cm behind the target position in the thin target scattering chamber.

To determine the energy-transmission window for 100 the transport line, a single E detector was used in conjunction with a multiline alpha source (a com- 8 9 bination of " Gd and " Th). Figure l(a) shows the Jjl J4 J reference spectrum and Fig. I (b)-(d) shows the ob- o served energy spectra of the souice when the trans- 300 (c) _ port line is set for an energy of 3.2, 5.4, and 8.4 MeV, respectively. By comparing line intensities measured at different energy or momentum settings of the 200 transport line, we have deduced the relative transmission vs momentum deviation &p/p for the first half of the transport line (see Fig. 2). These data show that the momentum transmission of uie transport 100 line is hp/p — 26% (FWHM), which is much larger than that required for the spectrometer, 8 p/p = 4%. To investigate the filtering properties of the mass

~~filter, a AE-E solid-state telescope was used to iden- 150 (d) tify protons, deuterons, tritons, 3He, and alphas,~~

100 M8 2M FIGURE 1. Energy spectra of a Gd plus Th alpha source that illustrates the energy transmission of the {First half of the transport line. Part (a) shows the reference spectrum when a source is 50 located directly in front of the detector, and (b), (c), and (d) show spectra from a source located at target position when the line is tuned for 3.2, 5.4, J «, and 8.4 MeV, respectively. 3 6 9 ENERGY INSTRUMENTATION AND COMPUTING 191

~~-50 -25 0 25 50 2.0 2.5 3.0 3.5 4.0 6p/p(%) Mass-to-Charge Ratio Setting (amu/Q)~~

FIGURE 2. Momentum transmission of the first FIGURE 3. The mass-to-charge transmission of the half of the transport line, as determined from the first half of the transport line for alphas (dashed alpha-source line intensities shown in Fig. 1. line) and tritons (solid line), as emitted from a thorium target. The transport line is set for a central momentum-to-charge value of 190 (Me which are produced in 800-MeV proton-induced reactions on a thorium target. For this test the transport line was set for a particular momentum-to-charge is lor an additional x-y steering magnet, needed after value and then the mass filter was tuned for various the first quadrupole triplet to correct for any mis- mass-to-charge ratios. By comparing the intensity of alignment of the beam axis produced by the the alphas and trilons at various mass-to-charge set- target/collimator/firsi triplet combination. Finally, tings, we obtained the masr,-to-charge transmission an additional detector box, located in front of the for the first half of the transport line (Fig. 3). A clear electrostatic deflector, will be used to tune the first filtering of the neighboring mass-to-charge species is quadrupole triplet more precisely and to steer the observed. More specifically, at a setting optimized for beam to the midplanes of both the electrostatic de- tritons (that is, A/Q = 3), those species with mass-to- flector and the dipole bending magnet of the mass charge ratios of 2 or less are reduced by more than filter. two orders of magnitude. {Background events result- We have also made progress on the control system ing from single- and multiple-wall scattering limited for both the secondary beam line and the spec- the measurement of the reduction factor.) This mass- trometer. This control system is different from previ- to-charge filtering is particularly important in our ous control systems used at LAMPF in that a micro- future experiments because the protons, deuterons, processor controls all of the interlock logic needed to and alpha panicles are produced with yields that arc, safeguard the system. Such a system is more flexible 5 4 3 respectively, 10 , 10 . and 10 times larger than those as the spectrometer develops: in addition, installa- of the ions for which measurements are planned. tion of the control system is greatly simplified be- These tests pointed out several improvements that cause only a single coaxial cable is needed to connect must be made before the line will achieve optimum the central processing unit to the remote in- performance. The first is the addition of antiscatter- put/output chassis from which the various devices ing collimators in the shape of springs that will line are driven. All of the controls needed to run the the inside of the beam lines. The second requirement magnets, electrostatic deflector, and vacuum system 192 PROGRESS AT LAMPF—1984 are in place; only the devices that they control remain deformation that has been observed in the neutron- to be installed. This work has been completed for the rich sodium region.14 first half of the transport line, and it is now fully operational. References 1. D. J. Vieira, J. M. Wouters, G. W. Butler, H. Spectrometer Wollnik. L. P. Remsberg, and D. S. Brenner, "TOFI (Time-of-Flight Isochronous) Spectrometer for the All long-lead items for the construction of the Mass Measurements of Nuclei Far from Stability," in spectrometer have been received or are on order. "Progress at LAMPF. January-December 1983," Los Specifically, the four dipoles that constitute the spec- Alamos National Laboratory report LA-10070-PR trometer have been designed and the appropriate (April 1984). pp. 121-124, coils and stands have been received. The iron cores 2. J. M. Wouters, D. J. Vieira. H. Wollnik. H. A. Enge. for the magnets are being manufactured and as- .1. R. Sims, D. C. Clark, el al.. "Time-of-Flight sembled; they should arrive during the early part of Isochronous (TOFI) Spectrometer," in the "Isotope FY 1985. The first magnet will then be set up for and Nuclear Chemistry Division Annual Report mapping and optimizing of the magnetic field. Dur- FY 1983," Los Alamos National Laboratory report ing the same period we plan to fabricate on site the LA-10130-PR(May 1984), pp. 179-182. vacuum tanks for the four dipoles. An order has 3. D. J. Vicira, D. S. Brenner, G. W. Butler. A. M. already been placed for the special nonmagnetic Poskanzer, L. P. Remsberg, H. Wollnik, and J. M. stainless steel. Wouters, "Tuncup of the Time-of-Flight Spec- trometer for Direct Mass Measurements." LAMPF Experiment 752 (August 1982). In the Future 4. C. Thibault. R. Klapisch. C. Rigaud, A. M. During the coming year our effort will be directed Poskanzer. R. Prieels, L. Lessard, and W. Reisdorf, toward four tasks, which we will try to accomplish by "Direct Measurement of the Masses of "Li and the spring of 1985: :(lO:!Na with an On-Line Mass Spectrometer," Phvsi- 1. installation of the second half of the transport cal Review C 12, 644(1975). line and incorporation of improvements to the first half, as outlined above. Once completed, the entire transport line will be tested to characterize and optimize its performance; 2. assembly, testing, and mapping of the first dipole magnet, which will be trimmed by vari- A Low-Pressure, Multistep, Multiwire ous adjustment features built into the design of Proportional Counter for the Time-of-Flight the magnet (see the INC-Division Annual Re- Isochronous Spectrometer port. FY 1983, for details2); • Experiment 752 — Thin Target Area 3. trimming of the remaining three magnets, alter the first dipole magnet is fully understood and Utah State Univ., Los Alamos, Clark Univ. appropriately trimmed (all four magnets will be Spokesman: D. J. I ieira (Los Alamos) trimmed in a similar fashion); and Participants: A.'. I aziri (Utah Stale i'niv.J: G. H'. Butler, 4. assembly of the magnets to form the spec- D. J. I'ieira. andJ. M. U outers (Los Alamos): and D. S. trometer. We will then characterize and op- Brenner (Clark Univ.) timize the performance of the system, which will predominantly involve minimizing the A low-pressure, multistep. muHiwire proportional TOF spread through the spectrometer for a counter (MSMWFC) has been developed for the particle with a given mass-to-charge ratio. characterization and testing of the time-of-flight The first experiment, scheduled for summer/fall isochronous (TOFI) spectrometer and its associated 1985. will allow us (1) to further test and optimize secondary-beam transport line. This type of counter TOFI with low-Z. neutron-rich fragmentation was selected because of its high sensitivity, large products and (2) to study the rapid onset of prolate dynamic range, and good position (0.2 mm FWHM) INSTRUMENTATION AND COMPUTING 193 and timing (180 ps FWHM) resolution.1 Furthermore, because the counter operates at low gas H> pressures (1-10 torr) and high electric-field strengths, which enable short collection times, it can be used as a transmission counter with thin gas-isolation windows and it can operate at high counting rates. Here we discuss the basic operating principle of the MSMWPC, describe the technical details of the detector and signal processing, and report on the performance we have measured for alpha particles and Particle fission fragments. The MSMWPC, which consists of five wire-harp planes, is shown in Fig. 1. The central plane is the anode (at a voltage of+VI), the outermost planes are cathodes (at a voltage of —V2). and the inner two planes are at ground potential. The counter operates as a combined parallel-plate avalanche counter -V2 -V2 (PPAC) and multiwire proportional counter (MWPC). Because of the large cathode voltage, an FIGURE 1. Top-view schematic of the multistep, avalanche is produced between the cathode and the multiwire proportional counter operation. ground planes when an ion passes through the counter. This avalanche is then transferred into the MWPC stage (created between the ground and anode also are obtained. Position information is derived planes), where '.he signal is further amplified by the from the ground (position) planes using a delay line large electric-field gradient existing around the anode readout, and timing information is obtained from the wires. High gains, typically 10-80 times larger than fast-anode signal.1 those of single-step counters, are achieved using this A picture of the detector is shown in Fig. 2. All the multistep process, and, because the process enables wire-harp planes, with 3-mm spacing between planes, good signal-to-noise ratios, ions of low energy ioss are made of 20-um-diam gold-plated tungsten wires

~~FIGURE 2. The counter and its components. 194 PROGRESS AT LAMPF— 1904~~

spaced I mm apart and mounted on a 3-mm-thick Tests of the MSMWPC have been made using G-10 printed circuit board with a 73- by 73-mm: various a sources and a :52Cf fission source. A mask opening. Every four wires on the position planes are with 0.5-, 1.0-, and 2.0-mm-diam holes was placed in connected to one tap on a type PE 20611 delay line front of the detector. Figure 3 shows position spectra (5-ns delay/tap). To improve the signal-lo-noise obtained for a mixed "9Th-usGd alpha source. As- ratio, the signals derived from each end of the delay suming uniformly illuminated apertures and ignoring line are amplified using board-mounted Motorola scattering by the windows, gas, and wires, we calcu- MAI 10 X5 amplifiers, and the position of the ion late a projected image diameter (FWHM) at the x- passing through the counter is deduced from the and r-position planes of 1.01 and 1.07 mm, respec- measured timing difference using standard electron- tively, and we observe a position resolution (FWHM) ics. Each wire plane has a transparency and screening ofl .07 ±0.06 and 1.39 ±0.10 mm, respectively. For efficiency of 98 and 86%, respectively. Anode timing a 0.5-mm-diam hole, a position resolution (FWHM) is taken directly from the anode plane. A pressure- of 0.86 ± 0.22 and 0.97 ± 0.14 mm was measured. regulated gas-handling system supplies a continu- Reducing the above, an intrinsic position resolution ous flow of isobutane gas to the detector, and thin of 0.50 ± 0.20 mm (FWHM) was deduced for alpha (~ 80-ug/cnr) polypropylene foils supported on a particles. No walk in position (<0.1 mm) with anode grid of 0.5-mm-diam stainless steel wires spaced 25 amplitude or energy was found. Similar position mm apart arc used as gas-isolation windows. resolution performance was measured for -52Cf fission fragments.

~~"" (a)~~

~~I I MFWHM = 1.39-JV- x Position (mm) I 10~~

~~y Position (mm)~~

FIGURK 3. Position spectra obtained at a pressure of 4.5 torr, an anode voltage of +500 V, and a cathode voltage of-250 V through a multiple-hole mask at the (a) x-plane and (b) j'-plane locations. The spacing between the holes is 10 mm and the diameter of each hole is 0.5,1.0, and 2.0 mm, as reflected by the height of each peak. The flat background is attributed to a low-level, internal contamination of the counter resulting from exposure to 252Cf and alpha sources. INSTRUMENTATION AND COMPUTING 195

Detector timing tests were performed between two ns for fission fragments and I. I ± 0.2 ns for alpha MSMWPCs and a silicon counter. The gas counters particles. were operated in both the MWPC (with the cathode Although our findings are not as impressive as voltage turned off) and the MSMWPC modes for those reported in Ref. 1, the counter served us well in comparison. When properly adjusted (cathode volt- the characterization of the first half of the TOFI age — anode voltage), the MSMWPC mode gave transport line (see contribution by Wouters et al.). comparable or only slightly worse (~IO%) timing Further use of the detector is planned for defining results than those obtained for the MWPC mode. and optimizing the performance of the transport However, when the cathode/anode voltages were line/spectrometer and for the forthcoming TOFI ex- adjusted to give the largest signal amplitude (as in the periments. position measurements above), timing performance This detector is based on a similar detector built by was degraded by ~35%. In Fig. 4, a 25:!Cf fission- Los Alamos Group P-3. We thank A. I. Gavron and J. fragment timing spectrum measured between an G. Boissevain for their help. MSMWPC and a silicon counter is shown. Through a series of such measurements the intrinsic MSMWPC Reference timing resolution was determined to be 0.55 ±0.10 I. A. Breskin, R. Chcchik. Z. Frankcl, P. Jacobs, I. Tserruya. and N. Zwang, Nuclear Instruments & Methods 221, 363 (1984).

~~FWHM = 0.69 ns~~

~~82 Time (ns)~~

~~FIGURE 4. The 252Cf fission-fragment time spectrum obtained between a silicon counter and a MSMVVPC operated at a pressure of 2.5 torr, VI = +270 V, and V2 = -270 V. 196 PROGRESS AT LAMPF—1984~~

EPICS and HRS and helium pumps on the floor and connecting them to the target system through flexible metal bellows Polarized Targets at HRS lines. An overhead view of the target and plumbing system is shown in Fig. 2. A longitudinally (L) polarized target was mounted A JHe/4He dilution refrigerator of • ~ 100-mW at HRS during cycle 41. Capable of polarizing both capacity was borrowed from KEK to cool the target protons and deuterons. it was used to study few- volume (2 by 2.5 by 5 cm) to ~ S 7 mK. The supercon- nucleon interactions at forward-scattering angles into ducting magnet was borrowed from Argonne Na- the Coulomb-nuclear interference region. Collaborat- tional Laboratory. ing groups in the development of this target system The assembly started on the HRS floor in early were UCLA; the University of Minnesota; the Na- February 1984. Simultaneously, the magnet was tional Laboratory for High Energy Physics (KEK) tested in the staging area. A nitrogen leak developed and the Universities of Kyoto. Hiroshima, and from the magnet heat shield into the insulating Nagoya in Japan; and Los Alamos. vacuum. The internal leak location was pinpointed Polarized-target technology has evolved about and entries were cut through the stainless steel shell aligning the nuclear magnetic moment in the direc- for the repair. Operational capability was achieved in tion (parallel or antiparallel) of a strong (25-kG) late June with a proton target. The proton (deuteron) applied magnetic field. This posed significant target material was l,2-propanediol(-d8). Typical challenges at the HRS. The 3.6-msr acceptance of proton (deutcron) polarizations were 70% (35%). HRS requires the least possible magnetic distortion of particles scattering from the target. L-type field For experimental results, see also in this volume geometry is usually supplied by surrounding the the reports from experiments 583U, 709, 790, and target volume with an air-core, superconducting, 685. At the conclusion of these experiments in Sep- Helmholtz-type magnet. Such magnets have fragile tember, the dilution refrigerator and related equip- internal coil supports (for minimizing heat leaks) and ment were returned to KEK. The magnet is next strong fringe fields because there is no confining iron assigned to Exp. 815 and afterward will be returned to core. These fragile supports necessitate a minimum Argonne. field in the vicinity of the iron HRS frame. A frozen-spinor technique was used to satisfy these EPICS Resolution constraints. At temperatures near 1 K, the polariza- C. L. Morris and N. Tanaka 4 4 tion lifetime varies as fi and inversely as T" , where During the spring i 984 shutdown several repairs B is the holding magnetic field and T is the tempera- and upgrades were made to the channel and spec- ture. Lowering the target temperature to the 10 mK trometer system. The fixed-collimator, first variable region allows reducing the magnetic field strength to jaw, and multipole magnet were replaced in 3-10 kG while maintaining polarization lifetimes of coordination with the A-l target-box replacement, all about 10-100 h. Active polarization still requires by remote handling. Figure 3 is a sketch of the 25 kG, so a system for mounting the target hardware geometry and Fig. 4 is a photograph of the jaw as- (magnet, refrigerator, target polarimeter, and beam sembly. The multipole magnet was built by the Uni- monitors) on platforms and moving the magnet away versity of Colorado. from the spectrometer pivot during polarization was Near the beginning of the summer 1984 produc- designed. After polarizing, the target temperature was tion period, the spectrometer front wire chamber was lowered ("freezing" the spin), the magnetic field was replaced with a new chamber having only half the decreased, and the target was replaced over the spec- number of planes (two each, .v and y), capable of trometer pivot. resolving the left-right ambiguity by means of the Two views diagramming the experimental layout induced cathode pulse. Reducing the number of are shown in Fig. 1. The refrigerator, magnet, liquid- planes and filling the inactive layers in the chamber helium supplies, target polarimeter. and beam assembly with helium resulted in halving the mate- monitors were mounted above the pivot on plat- rial thickness, as shown in Table I, and improving the forms capable of traveling 1 m upstream. Vibration missing-mass resolution from 140 to 100 keV isolation was accomplished by mounting the vacuum FWHM at 180 MeV [Fig. 5(a)]. One also notes INSTRUMENTATION AND COMPUTING 197

~~Evaporator Pump Package~~

~~3He gas cart Superconducting Separator Pump (a)~~

~~Superconducting Magnet Power Supply~~

~~3He Pump Package~~

~~LC-Q-12~~

~~Beam -~~

~~Dilution Refrigerator~~

Polarized Target "7Control Racks Superconducting Magnet Control NMR Electronic Rack Rack 1000-tLHeDewar JOT Superconducting Magnet Rnerator '-11/34 Mixing Chamber (Carcinotron) Vacuum Pump Packagi ., Cooling System tot Carcinotron

~~LIQUID-HELIUM RESERVOIR~~

~~iUPERCONDUCTING MAGNET~~

~~He PUMP LINES LIQUID-HELIUM DEWAR (b)~~

~~MOVING MECHANISM FOR DILUTION REFRIGERATOR~~

~~FIGI RK 1. Plan (a) and elevation (b) views of polarizcd-target components at the HRS pivot. CO OB~~

~~FIGURE 2. Overhead photograph of the polarized-target system in place at the HRS pivot. INSTRUMENTATION AND COMPUTING 199~~

~~FIGURE 3. Assembly drawing of EPICS front end, showing fixed collimator, movable jaws, and multipole magnet.~~

~~TABLE I. Changes to EPICS Front Chamber.~~

~~4 Thickness (mg/cnr) p/Trilli (X10 ) Material Old New Old New~~

~~Argon 18 4.2 9.1 2.1 17 4.0 3.8 0.9 Helium 0 2.3 0.0 0.2 Mylar 23 19.4 5.7 4.8~~

~~TOTAL 58 29.9 18.6 8.0 200 PROGRESS AT LAMPF—1984~~

~~FIGURE 4. Inner assembly of movable jaws used in EPICS front end. INSTRUMENTATION AND COMPUTING 201~~

~~r-60 -BOO~~

~~-40~~

~~—200~~

~~1200 -100. 100 -100 '-50 (a) FIGURE 6. Projection of missing mass over limited -400 angular acceptance.~~

-300 on the HRS computers have tripled tape capacity and doubled the rate. A similar change will be made to EPICS. The EPICS PDP-U/45 was replaced by a VAX-11/730 at the beginning of cycle 40 with very few difficulties. The VMS operating system user interface was similar enough to that available under =--0 RSX-11M that users familiar with the old system -50 '50 100 -100 adapted quite well. (b) The VAX-11/730 processes data at about the same rate as the PDP-11/45 but does not have any of the FIGURE 5. memory limitations of the old 16-bit machine. How- (a) Projection of missing mass over complete ever, user terminal response time on the VAX was + 93 angular acceptance for 180-MeV it on Nb, sluggish compared to that for the PDP-11/45. Almost target density 600 mg/cnr. all of this can be attributed to the time it takes for (b) Two-dimensional plot of missing mass and vertical scattering angle. Units of missing VMS to spawn a task (5 s on the VAX-11/730). mass are 10 keV per .t-axis scale, and units Because the Q program makes heavy use of this of angle are 0.1 mrad per j'-axis scale. spawning feature when starting and stopping runs as well as when displaying histograms, a substantial degradation of terminal response results. Although [Fig. 5(b)] that resolution was correlated with vertical some improvement can be achieved by restructuring (dispersion plane) scattering angle and that it is even the way tasks are done, the VAX-11/730 will never be better for negative angles than for positive angles. as fast as the PDP-11/45 in this regard. It was con- With reduced acceptance, resolution of 80 keV can be cluded that the best option was to replace the obtained (Fig. 6). VAX-11/730 with a VAX-11/750, which is about twice as fast. As of mid-December the VAX-11/750 had been installed and was operating. As expected, Data System terminal response (as well as event-processing speed) J. Amann has been improved by a factor of 2, bringing terminal The Data-Analysis Center (DAC) VAX computer response back to the level experienced with the spooling and replay capability was completed for the PDP-11/45. EPICS and HRS RSX-11M and -1 ID data tapes. Additional upgrades planned before the beginning New 6250-bpi tape drives and larger system buffers of cycle 42 are the addition of a large (456-Mbyte) 202 PROGRESS AT LAMPF—1984

disk lo ihc EPICS VAX. to be used for spooling tapes face so that UNIX programs can run transparently for replay, and an Ethernet connection between the under VMS. Implementation of EUNICE also made EPICS VAX and the "DAC. An order has also been available the word processing tools for which UNIX placed for a VAX-11/750 and a 456-Mbytc disk for is known. HRS. This will replace the on-line PDP-11/45 and should double the capacity for on-line event analysis. Networking Networking capabilities in the DAC were signifi- Data-Analysis Center cantly increased during 1984. Specifically, access to remote networks, such as TELENET, was made .\I. lloclm ami /;. Hoffman easier through the C-Division computers. In addition, the DAC acquired dial-out modems and soft- Cluster ware so that users could transfer files between DAC The most dramatic change in the operation of the machines and other computers over phone lines. Data-Analysis Center (DAC) has been the implemen- Progress was made in providing a local area network tation of a VAX cluster. The cluster is a network of linking data-acquisition computers with the DAC. loosely coupled VAX computers tied together with a Such a network provides a convenient means lo high-speed network and sharing common disks. The transfer files between data-acquisition and analysis cluster concept reduces problems with file ac- systems and may provide a means to share some cessibility because the common disks arc readable common resources, such as printing facilities. An from all VAXes in ihc cluster. Software support for Elhcrnel connection between the DAC and EPICS the cluster is available in VMS Version 4.0, and the counting house was implemented in 1984, and DAC served as a test site for this version in order to further expansion of the network is planned for 1985. make use of the cluster concept as early as possible. That proved to be a rather painful process for both DAC staff and users because the cluster software was Parallel Processor not debugged and the features in Version 4.0 added A major project in the data-acquisition section in considerable overhead lo the system memory re- the pnst year was a special-purpose multiprocessor quirements. The memory in all the cluster machines system lo analyze data generated ai LAMPF. In this was increased to at least 8 Mbytes to improve the system microcomputers are given separate buffers of interactive response time, which was hampered be- data (events) to process. Because the computers exe- cause of the insufficient memory to support user cute exactly the same code but run independently of processes. Scratch disk space also was increased in each other, this buffer processor system is the cluster when all local disks were converted lo enormously simpler than a general-purpose parallel scratch space and two additional RA81 Winchester processing system. Such a system could also be used disks were purchased. A second HSC-50 disk and on line to reduce computer dcadtime and increase the tape controller was obtained so that no single poinl of fraction of events analyzed on line. Off line the failure would eliminate access to the common disks. system could be used lo reduce the load on the DAC Presently, three of the four VAXes in ihc DAC arc VAXes. part of the cluster. During the year requirements for the system have been defined, hardware for a prototype system UNIX (PDP-11/730s and Ethernet) has been selected, and the system software has been designed. For experi- System software was enhanced with the addii ion of ments with many calculations per event, a buffer DECalc, a spread-sheet program for the VAX. processor system costing less than $20 000 can EUNICE, a UNIX environment package that is provide the performance of a VAX-11/780. It is layered on VMS, was added to VAX machine expected that the prototype system will be ready for MPFG0. EUNICE translates UNIX system calls to testing in the spring of 1985. VMS system calls and provides a UNIX-like inter- INSTRUMENTATION AND COMPUTING 203

Q System The program incorporates considerable detail: for instance, minimum bend radius of conductor, layer- During 1984 both Q replay and data acquisition to-layer turn transitions, allowance for insulation, using VAXes and the VMS operating system were and a transverse-field uniformity of 1.0%. Physical fully implemented and released to users. VAX data dimensions of the magnet arc calculated in addition acquisition was used successfully in experiments at to the electrical and cooling parameters. A sketch of EPICS at LAMPF, at the Bates Linear Accelerator in the magnet cross section is plotted along with the Massachusetts, and at the Bevalac at Lawrence coordinates in the proper format for input to the Berkeley National Laboratory. The EPICS POISSON program (POISSON is the magnetic-field cal- VAX-11/730 system was upgraded to a VAX-11/750 culation program used lo help achieve higher order at the end of 1984 to improve on-line response and field corrections). Finally, magnet material and fabri- performance. Another VAX-11/750 is being cation costs are calculated using current costs for purchased for HRS. copper, iron, and machining and fabrication. All new VAX data-acquisition systems are being EMD is a user-friendly program that prompts the equipped with 6250-bpi tape drives (Kennedy user at several stages of the calculation for specific 9400s). These drives were evaluated during If84 at input. Its design solutions compared with parameters HRS with positive results. of several existing magnets prove its accuracy. We A project has been started to evaluate running estimate that the time required for preliminary microprogrammable branch drivers (MBDs) and the magnet design has been reduced from 3-5 h to less Q system on Q-bus machines (micro-PDPs and than 15 min. micro-VAXes) because these computers would be The program was written by Ann Aldridgc, Group cost effective for use at LAMPF. C-3. with guidance from Dick Hutson, MP-3, using A new version of the Q-acquisition-language design algorithms provided by members of the MP-8 (QAL) compiler, which is used by experimenters to stall specify CAMAC operations for Q data acquisition, has been completed. This new version allows additions of new QAL functions to the language to be Magnet Mapper made relatively easily and allows the user to add II'. Foreman support for new CAMAC modules easily. Development by Group MP-I of a new magnet- Expert Magnet Design Program mapping control system for use by the Group MP-8 magnet-mapping section was completed in Novem- E. D. Bush ber 1984. The new system provides support for An EMD program is now available to assist in the • a Scntcc NMR magnetometer interfaced through design of H-framc bending magnets. The program is CAMAC; an example of expert software, wherein decision algo- •an HP-3456 digital voltmeter, controlled via a rithms are built around a specialized knowledge base general-purpose interface bus link based in to reach a practical solution to a problem presented CAMAC; by the interactive user. • magnet temperature input through the HP-3456 Given such information as particle type, energy, digital voltmeter; bend angle, and clear aperture, the program designs a • magnet power-supply shunt voltage input magnet. It designs the vacuum chamber, allows through the HP-3456 digital voltmeter; clearance between the magnet poles and the vacuum • the new intcgralor electronics (flip-coil current lo chamber for alignment, designs the magnct-corc voltage) designed by A. Browman; cross section, and designs the coil using one of five • moving-coil data acquisition using the new inte- available LAMPF-slandard conductors that satisfies grators; the current density, pressure-drop, tempcrature-risc, • rotating-coil data acquisition, using the existing and water-velocity requirements. The user can input Rawson Lush probes; and specific parameters or allow the program to use built- • data acquisition using the existing Hall probes. in default values that will produce a feasible design. 204 PROGRESS AT LAMPF—1984

The software runs on a Digital Equipment Corpor- a special environment for proper operation. Re- ation (DEC) micro-PDP and uses the fixed disk for covery of partially completed operations is supported data storage. CAMAC operation is supported by a by a restart option, and an auto-dialer alarm system is Kinetic Systems 3912 type U single-crate controller used to notify operators of problems, allowing long and a device driver that was written for this project. runs to be made safely while unattended. More infor- The reconfiguration of the hardware has allowed mation on the system may be found in LAMPF construction of a smaller system that does not require internal documents MP-1-3450-1 and MP-1-3450-3. STATUS OF LAMPFII

~~(The following is the just chapter. Executive Summary, of the recently prepared LAMPF II report, "A Proposal to Extend the Intensity Frontier of Nuclear and Particle Physics to 45 GeV.")~~

Executive Summary clei, the field theory of the strong interaction, quantum chromodynamics (QCD), is being applied to the We propose to construct and operate LAMPF II, a nuclear many-body problem. high-intensity, medium-energy synchrotron addition To be sure, all three of these perspectives are to the Clinton P. Anderson Meson Physics Facility at needed to contribute to the principal endeavor of the Los Alamos National Laboratory This new fa- nuclear physics, a comprehensive understanding of cility will the nucleus and its response to external probes. In- • provide the nation's principal capability to ad- deed, even to attack only the newest frontier requires dress the frontiers of nuclear physics with an a complementary set of probes, consisting of high- unmatched array of light-hadronic probes, energy electrons, relativistic heavy ions, and high- • probe physical regimes beyond the standard energy light hadrons. model of the strong and electroweE k interactions, Electrons are the best projectiles for the study of • provide unique opportunities to address the the response of the charged constituents of nuclei, quark/gluon frontier in a manner complemen- described by the electromagnetic currents. In the tary' to other forefront facilities in nuclear and newest picture the charged constituents are the particle physics, and quarks that have charges of —('A) and +(%) of an «• provide key facilities for basic research and electron charge. Electrons interact with nuclear mat- education to a generation of scientists in the ter primarily through the electromagnetic force. 1990s and well into the next century. Thus, a very important class of nuclear processes is LAMPF II will consist of accessible with electrons—those processes excited by • a 6-GeV, 170-uA booster accelerator and a charged, nonhadronic probe. • a 45-GeV. 34-uA, 3-Hz main synchrotron, with a Nuclei, however, consist of both quarks and 50% duty factor. gluons. Typically, the quarks carry only about half of The injector accelerator will be the existing 800-MeV, the momentum content of nuclear matter. The 1-mA LAMPF linac. With its relatively high energy gluons, which bind the quarks through the color and compact emittancc, the LAMPF linac is superior force, carry the remainder. Gluoris are not electrically to any other existing potential injector. A broad array charged. Thus, electron probes are unable to directly of beams will serve research programs using kaons, stimulate a significant class of nuclear responses. pions, protons, anliprotons, muons, and neutrinos. High-energy collisions of heavy nuclei, produced These beams will provide the capability to probe by rclativistic heavy-ion accelerators, can create the the underlying behavior of quarks and gluons in high density and high temperature in nuclear matter nuclear matter. This is the essential frontier of nu- in which the many-body modes of quark and gluon clear science today; it is the extension of the historical behavior can be studied: (I) heavy ions provide tools development of nuclear physics. The early descrip- to test the gross behavior of this hadronic matter tion of nuclei using only bound nuclcons evolved to under extraordinary conditions and (2) rclativistic include the second treatment of nuclear behavior hea\y-ion collisions can produce a rich mixture of up with explicit meson properties. LAMPF has been a and down valence quarks, virtual sea quarks, and key tool in this endeavor. Nuclear science is embrac- color gluons, heated to high temperature or coming a third and even more fundamental constituent pressed to high density. picture, emphasizing quarks and gluons. To explore the consequences of q'iark/gluon substructure in nu- 205 206 PROGRESS AT LAMPF— J984

We propose to provide nuclear physics wilh a third would mediate family-changing interactions above and complementary tool, light hadrons. The princi- 10s GeV. This mass is already an order of magnitude pal advantage of light hadronic probes is selectivity. higher than the mass scale to be probed by the Like electrons, these probes are charged and therefore Superconducting Super Collider! are sensitive to electromagnetic properties. Like The weak bosons, which carry known parity- heavy ions, these probes access both the quarks and violating weak currents, were directly observed in gluons. By selecting the appropriate hadron 1983 by a high-energy experiment with masses in the beam—choosing from a menu of kaons, antiprotons, 80- to 100-GcV range. The bosons, which may serve pions, and protons—the experimenter can choose the to restore parity symmetry at very high unification quark content of the beam and thereby select the energies, must be far more massive lo account for the nuclear characteristic to be investigated. Op- maximal violation of parity symmetry seen at low portunities for frontier research wilh nuclei using a energies. The current lower limit on the right- light-hadron facility such as LAMPF II will be un- handed IV boson is 380 GeV, set nol by a direct matched in the versatility and breadth of capabilities search at a high-energy laboratory but by precise offered. studies of ordinary muon decay at a high-intensity Although several of the selected programs of sci- low-energy muon beam! ence we have identified may be addressed at existing The LAMPF II booster and main ring accelerators facilities, there is no current prospect anywhere to arc of relatively simple design, incorporating a num- advance this forefront of nuclear physics in a con- ber of technological innovations. The high energy of certed and timely manner. Isolated programs at high- the main ring beam, 45 GeV, will be unique in energy physics accelerators and scattered efforts at affording the flexibility required to address quark and other laboratories fall short by a factor of 100 in the ginon degrees of freedom in nuclei. These ac- rate at which this research may be advanced. The celerators will be the foundation for a new generation vitality of nuclear physics in the next generation will of research. depend strongly on the availability of a facility with The experimental facilities include two new areas, the range of capabilities promised by the LAMPF II providing high-energy hadron beams and neutrinos. project. A continuing renaissance in nuclear physics The existing LAMPF meson area will be upgraded, will be within the reach of LAMPF II. providing facilities for medium-energy hadron LAMPF II will provide the principal facility for the beams. next generation of profound tests of questions in Construction of the LAMPF II accelerators will particle physics. The very high-energy facilities now cost $280 million, and experimental facilities for the being exploited or planned by the high-energy physics initial research program will cost an additional $172 community directly access particular higher mass million, including the cost of upgrading existing scales that could provide answers to key questions LAMPF experimental areas. With construction about the family structure of fundamental particles beginning in FY 1988, neutrino and pulsed muon and the possibility of constructing a unified treat- beams will be available for initial use in FY i 992 and ment of the forces of nature. Some or all of the the full facility will be operational in FY 1995. answers sought may lie outside the mass ranges providing an unprecedented combination of high- opened by these accelerators. The history of nuclear purity, high-intensity hadron beams. and subnuclear physics has taught us that sensitive LAMPF II will provide the physics community experiments at relatively low energies can often un- with a diverse spectrum of capabilities to probe fun- cover ihe critical clues of high-energy phenomena. damental questions in strong-inleraction physics and Striking examples, in which current limits on the in elcclrowcak physics. In this summary, we survey rales of many rare decays of muons. pions, and kaons the principal physics topics lo be addressed by where family number is not conserved, now provide LAMPF II, the conceptual design of the accelerator experimental evidence nol possible with high-energy and experimental facilities, the project costs and facilities. The current limit on one rarc-kaon decay schedule, and the unique resources thai Los Alamos can be used to bound the mass of the boson that National Laboratory will bring lo bear on this project. STATUS OF LAMP? II 207

Scientific and Technical Summary The traditional view of nuclear behavior uses only nucleons (protons and neutrons) interacting via two- Strong-Interaction Physics body potentials. Physics often must resort to such simplifications, trading away detail (and momen- Nuclear physics is predominantly concerned with tarily intractable problems) for clarity and utility. the study of the response of nuclei to external stimuli This model describes many characteristics of nuclei, in an attempt to uncover the way in which nuclei are but relies on effective potentials and phenomenologi- bound together and the nature of the constituent: cal models with adjustable parameters. This ap- from which nuclei arc assembled. proach conceals flaws and makes such models uncer- Nuclei can be viewed as consisting of nucleons tain tools to use in predicting nuclear behavior in bound by a potential that is described by the ex- unexplored physical regimes. When discrepancies oc- change of mesons. The individual nucleons and cur, it is not known whether the difficulties originate mesons consist of quarks, bound by the raw strong in the models or whether they occur because contact interaction that is due to the exchange of color has been lost with more fundamental structures. gluons. During the last decade the principal force in nuclei, which is the strong interaction, has been Nuclear physics has long treated the potentials in described by a promising gauge theory, quantum which nucleons are bound as arising from a strong chromodynamics (QCD). force carried by meson exchanges, with the lightest mesons (pions) dominating this exchange interac- With both the fundamental constituents and the tion. Thus, on a distance scale larger than the nucleon field theory apparently kno^

This approach ignores the fundamental physics quarks. It will become possible to carry out sensitive essential for understanding normal nuclear matter, studies of nuclei in which one or more nucleons is the regime in which quarks are still confined. This is replaced by a hyperon (a strange nucleon) or, in the an intermediate-distance scale, between the ex- more modern constituent description, in which one tremely short distances of asymptotic freedom and or more strange quarks are embedded among the up the long and medium distances associated with the and down quarks in the nucleus. LAMPF II kaon nucleon and meson pictures. This subasymptotic beams can be viewed as strange-quark beams. The regime is the frontier of strong-interaction nuclear new nucleon created in such studies differs from physics, which can be studied by beams of electrons, naturally occurring nucleons, thus populating a new heavy ions, and light hadrons at appropriate energies. realm of nuclear states and producing excitations However, as indicated earlier, only light-hadronic with distinct signatures, A new world of nuclear probes provide the capability to selectively probe matter can be created and tested against meson, both the quark and gluon content of nuclear matter. nucleon, and quark descriptions. LAMPF II will permit a broad assault on this exciting Contemporary nuclear problems accessible in new frontier. LAMPF II hypernuclear studies include testing for The two main research areas to be addressed by the existence of stable, doubly strange dibaryons: nuclear physics in the next decades are states in which two strange nucleons are created and • the understanding of the relevant degrees of free- bound together or, alternately, assemblies of six dom required to explain the nucleus and quarks including two strange quarks. Such dibaryons • the nature of quark confinement in nuclear mat- are predicted by nuclear "bag" models, major con- ter. tenders to explain quark confinement. LAMPF II LAMPF II will provide the nuclear physicist with beam intensities are likely prerequisites for the suc- the three principal tools required to address these cessful search for such a rare phenomenon. studies. These tools will be used to do experiments The anomalously weak spin-orbit force felt by • inserting a "test charge" in the form of the lambda hyperons bound in certain hypernuclei has strange quark into the nucleus to probe the nu- led scientists to seek experiments that might dis- clear volume; tinguish between the traditional hadron and modern • scattering a gamut of traditional hadron probes quark pictures. These alternate descriptions predict (such as pions, protons, and kaons) to sample the very different sigma hyperon spin-orbit forces. The variety of length and time scales that characterize flux and beam purity provided by LAMPF II will the hadronic response of nuclear matter; and permit the high-resolution spectroscopy needed to • depositing the high energies and momenta avail- test these predictions. able in LAMPF II beams in nuclei, creating An exotic form of'He, containing a bound lambda extreme conditions. hyperon. has been found to have a peculiarly weak In applying each of these three tools, a number of binding energy. Promising but untested justification specific research areas deserve identification. It is from emerging quark models has been offered, per- always difficult to specify particular experiments to haps not explicable in traditional hadron pictures. be carried out a decade hence, but having described Again, we will likely develop a real explanation only the capabilities afforded by LAMPF II. today's with the unique beams of the LAMPF II facility that perspective provides a guide as to how one might can test the consequences of such explanations in begin these exciting studies. other systems. Extremely narrow states in sigma hypernuclei, hy- Inserting the Strange Quark into the Nucleus. Hy- pernuclei with strangeness greater than unity, and pernuclear physics is the study of the nucleus with a studies of the strangeness-changing part of the new dimension. LAMPF II will permit a major ad- nuclcon-nucleon weak force are other examples of vance beyond conventional nuclear studies limited the exotic research to be done in nuclear physics, for to neutrons and protons or, alternately, up and down which the intense meson beams of LAMPF II are needed. STATUS OF LAMPF II 209

Scattering LAMPF II Hadron Beams from Nuclei. nucleons do indeed depend on the nucleus in which The unfolding of the assortment of length and time they are measured, demonstrating in a convincing scales in nuclear responses will be advanced dramati- way that the nuclear environment influences quarks. cally by the intense, pure hadron beams that LAMPF LAMPF II can be used to explore this exciting insight II will deliver. The choice of hadron probe will select with a complementary study of the Drell-Yan pro- the nuclear feature to be tested. For example, un- cess. In this process, a quark (or antiquark) from a matched intense beams of antiprotons will be useful beam hadron annihilates with an antiquark (or in studying the relativistic approach to ground state quark) from the target, leading to the production of a properties of nuclei, a treatment that has grown out of virtual photon that subsequently decays into a pair of recent meson factory research with protons. The leptons. It has recently been shown that a high- formation of pions within nuclei, resulting from anti- precision study of the Drcll-Yan process performed proton annihilation, can be compared to ordinary in a manner similar to the EMC experiment (measur- cohereni production from nuclei with pion beams, ing the anomalous dependence of this process on the revealing whether these annihilation pions mimic atomic number) could lead to a definitive choice "real" pion behavior and leading to the unfolding of among competing models of the EMC effect. The key the space-time evolution of hadronic interactions. To to this sensitivity is the complementary way in which carry out this structured program in which time the virtual sea and real valence quark distributions of scales of about 1 fm/c arc investigated, pion the target enter in the cross sections for deep inelastic momenta up to 1.5 GeV/c arc required. The lepton scattering and the Drell-Yan process. Proton necessary antiproton momentum is 8-10GeV/c. beam energies near the LAMPF II energy of 45 GeV Only a facility with the high energy and high intensity are excellent for these studies. In fact, the energy of LAMPF II will be able to provide pure, high- dependence of the appropriate range of the dilepton intensity beams at these momenta. cross section favor this energy rather than higher LAMPF II K.+ beams will provide a strikingly energies. different projectile. Unlike the strong annihilation of Uilepton production using LAMPF II K+ and K~ the antiquarks in an antiproton entering a nucleus, beams (su and 5/7) can uncover the poorly understood the strange antiquark in K+ encounters no real virtual sea quark distributions in nuclei. The K+ (valence) strange quark in nuclear matter and thus probes the sea primarily, but the K~ probes both the annihilation does not take place. It remains stable valence and sea quarks. The intensity of LAMPF II and active, therefore, to probe the entire nuclear beams will facilitate the comparative studies needed volume, and its comparatively weak scattering can be to do these experiments. treated with precision. Even more tantalizing are the The existence of bound gluon states, called recent results indicating that low-energy K+-nucleon gluonium, which are mesons constituted without scattering is well described by nucleon-quark dis- quarks, is one of the basic predictions of QCD, and tributions. This unprecedented example of how a the search for such mesons will be the subject of a low-energy interaction tests modern constituent new hadron spectroscopy at LAMPF II. Only with models implies that the K+ can directly reveal the such dedicated facilities will a comprehensive study quark densities in a nucleus, not just in a nucleon. of this subject, fraught with small cross sections and The duality of quarks in nucleons and quarks in large backgrounds, advance in a meaningful and nuclei can thus be confronted with the high-purity, timely manner. The novel nature of gluonium makes high-flux K* beams to be produced at LAMPF II. it an essential part of the advancement of hadronic The nature of quark confinement and the quark- nuclear physics. gluon degrees of freedom in nuclear physics will be uncovered in several crucial research programs at Depositing Energy in Nuclear Matter with High- LAMPF II. Recent striking evidence for quark Energy Beams. The response of nuclear matter at degrees of freedom in nuclei has emerged in the deep extreme temperature and density has been identified inelastic-scattering experiments of the CERN Euro- in many forums as a particularly attractive way to pean Muon Collaboration (EMC). These experi- address quark physics. Under some combinations of ments have shown that quark distributions in these conditions, a startling transition of nuclear 210 PROGRESS AT LAMPF— 19B4

matter to a plasma of quarks and gluons is predicted. in 1983 of the quanta of the weak interaction, the W The identity of individual nucleons vanishes. Rel- and / bosons, which together with the photon ativislic collisions among heavy ions have been iden- mediate the entire known range of clectroweak tified as a promising way to search for this postulated processes. plasma. Antiproton annihilations in nuclei arc a Just as ihc classical synthesis of Maxwell broke complementary way to achieve extreme conditions down only a generation later in the face of radioactive in nuclei. The release of annihilation pious decay and other new phenomena, we can expect to energetically heats a small volume of nuclear matter, find that today's theories require extension. and this heat spreads to the rest of the nucleus, LAMPF II will test the limits of the electroweak cooling the original hot region. A region that is large theory in crucial ways. enough and still hot enough to see the plasma effect is Physicists have moved rapidly to attempt the com- expected to appear at energies above those studied to bination of the candidate gauge theory of the strong dale—that is, for antiproton momenta above 2 interaction QCD with the elcctroweak theory. This GeV/c. theory, constructed with minimal assumptions (no Detailed intranuclear cascade and hydro- assumption about nature not required by experimen- dynamical calculations strongly suggest that an- tal evidence), is known as the standard model. In the nihilation of antiprotons and antideutcrons in this standard model all of nature's mesons and baryons, energy range would heal a porlion of a target nucleus and their strong, weak, and electromagnetic interac- into the regime where the quark/gluon phase transitions, can be described by combinations of nature's tion is predicted to exist. Even if this spectacular building blocks, the fundamental fermions. bound by transition eludes the expectant nuclear science com- nature's glue, the mediating color gauge bosons. munity, the sludy of nuclei at the accessible These are the bosons that carry the strong interaction, temperatures and densities is of substantial interest, the gluons, and the W, /, and the photon, which carry the weak and electromagnetic interactions. Our model is a minima! one, though. Outstanding ques- Eleetroweak-Interaction Studies of the tions confront us. We do not understand why there Standard Model and Its Extensions are three gauge groups (at least) of these bosons [arranged in mathematical groups called SV(3)(. The study of clectroweak interactions, an impor- SU(2),,, and £'(!)„] or why these objects have the tant frontier of panicle physics, will be the second particular masses they exhibit. major arena for LAMPF II research. The problems The fermion building blocks appear to fit into traditionally probed by low-and medium-energy par- three known, and curiously symmetric, families as licle physics, long pursued in parallel to the activities well. Pairs of quarks (up and down, strange and at high-energy laboratories, will expand greatly. The charm, top and bottom) and leptons (electron and Superconducting Super Collider (SSC), the Tcvairon electron-neutrino, muon and muon-neutrino, tau and SPS, and the SLC LEP. and HERA will pursue and tau-ncutrino) can be organized into three sets. higher mass scales in the hierarchy of particles. Arc these groupings truly meaningful? Why arc some LAMPF II will be the stage for an unmatched pursuit transitions among these families observed, but others of the low-energy manifcstalions of these higher mass never appear? Why do these objects have their ob- scales and for significant tests of the dynamics of the served masses, and are the neutrinos truly massless? standard model, a vital complementary thrust forward. Theories of grand unification postulate that all of these separate groups collapse together at some The principal advance of the last generation of supreme energy. Attempts arc being made to treat particle physics was the unification of the elec- quarks and leptons as interrelated. The question of a tromagnetic and weak forces in a single theory. Com- possible underlying relation between the bosons and parable to the landmark derivation of Maxwell's fermions has been raised. Are they fundamentally equations in the late nineteenth century in which the different? Are these objects themselves constructed electric and magnetic fields were united, the elec- of more basic constituents? Can nature's fourth force, trowcak theory is consistent with all known physical gravity, be included in an even more grandiose observations, especially the long-awaited observation STATUS OF LAMPFII 211 synthesis? At its most reductionist extreme, the goal More realistically, detectors and data-acquisition sys- of particle physics is a single, elegant, and concise tems for such experiments will probably be de- theory that explains, at least in principle, all of the veloped after the first generation of LAMPF II ex- physical phenomena in the universe. periments, in which the raw flux available would be A frontal assault on these questions is being made used instead to tailor beam phase space and deliver by the high-energy particle physics community. truly pure kaon beams to researchers. LAMPF II will High-energy accelerators may directly produce new provide the capability and flexibility for all of these higher mass objects that may clarify the organization possibilities. of the pantheon of elementary constituents. Higher Neutrino masses stand out from the general par- energy research will likely clarify the transition region ticle mass enigma because neutrinos historically were in which some of the separation between families and thought to be massless, although it is now clear that forces is reduced and nature's anticipated underlying there is no fundamental reason for this presumption. symmetry is restored. Complete surprises will almost One class of LAMPF II experiments would search for certainly emerge. massive neutrinos in decays such as K —•• uv and A pursuit so compelling, the very cutting edge of A.'-— uv, in which the decay lepton energy distribu- physics, should not be left only to these new high- tion might display structure. A distortion of the 7t+ energy facilities. Even within their enormous energy spectrum in K' — rc1 vv, caused by massive neutrinos, range, the key insights may be experimentally inac- would be another appealing indicator. In each of cessible. Experiments at nonaccclcrator facilities and these experiments the extraordinary flux, purity, and at low- and medium-energy laboratories will be in- optical flexibility of LAMPF II beams will dramati- valuable, indeed essential, in uncovering the subtle cally improve the prospects for new physical ad- signatures of higher energy phenomena. Some studies vances. will be unique to these laboratories. LAMPF II neutrino beams will provide an un- The most immediate examples of the utility of equalcd opportunity to search for the subtle oscilla- LAMPF II in particle physics are the study of decays tion of specific neutrino types into other neutrino that violate family conservation, charge-parity (CP) types. This oscillation is a likely occurrence if neu- nonconservation, and neutrino mass measurements. trinos have mass. The experiments search for LAMPF II beams will provide fluxes of muons, changes in the proportions of various neutrino types kaons, and pions ideal for extending searches for along the beam direction. The high flux and continu- family-nonconserving decays of these particles ous availability of the neutrino beams at LAMPF II beyond present limits by many orders of magnitude. will be a major advantage over current neutrino The kaon beams at LAMPF II will be spectacular, beams because the neutrino-oscillation signal will providing flux two orders of magnitude more intense likely be observable only with many detected events than that previously available, with great flexibility and the smallest possible backgrounds. to achieve purity and optical control. The current In addition to searching for entirely new physics limit on the decay ATA —• jac is <2X 1O~'. If the process phenomena that may force extensions of the standard K, —• ue were mediated by a heavy family gauge model, LAMPF II beams will be a prime source of boson, the current limit on this decay would set a precise tests of the standard model. One dare not lower limit of W GeV on the mass of this boson. As assume that the standard model is complete and we have pointed out earlier, this mass is already an accurate, so it must be confronted with ever more order of magnitude higher than the scale directly stringent challenges. accessed by the SSC. In experiments under way we The scattering of muon neutrinos on electrons is a : i: hope to probe the 10"' range in a 2000-h run. If 10 clean, direct measure of the leading parameter of the were reached, this mass limit (dependent on the 1/4 electroweak theory, the dectroweak mixing angle 9,,. power of the measured branching ratio) would be LAMPF II will be the first opportunity for real s pushed to about 7 X 10 GeV. The proposed 2000-h precision in this area, with the possibility of event search could be accomplished in 1 day of running at samples with 104 scatterings observed. Current ex- u LAMPF II! A 1-year run could reach 10" , cor- periments are accumulating a few hundred events. responding to a boson mass limit of 2 X 10'' GeV! High-energy accelerators will refine our knowledge of 212 PROGRESS AT LAMPF—19B4 the masses of the W and Z bosons and of 6,, at high The main ring, approximately 1324 m in circum- energies. LAMPFII results will complement this ference, will provide 45-GeV protons with an average work and permit the energy-dependent radiative cor- current of 34 uA at 3 Hz. The beam will have a rections in the standard model to be tested. This is microstructure of pulses <2 ns long and separated by the only known quantitative test of the field-theoreti- 16 ns, ideal for timing measurements in many experi- cal aspects of the electroweak theory. It is comparable ments. in significance to the study of g—2 in the early days of The beam from the main ring will be extracted quantum electrodynamics (QED). slowly and transported to an area providing beams of CP nonconservation is one of our generation's kaons, pions, and antiprotons with energy

LAMPFII Experimental Areas Area H: • 35-GeV separated kaon and antiproton beam, LAMPF II will provide three powerful experimen- • 35-GeV unseparated kaon and antiproton tal areas. beam, and • Area A will receive the main ring beam via slow • a double-arm spectrometer area. extraction and will be a substantial revision of These beams include a capability at LAMPF II for the existing LAMPF meson area. It will provide research with each particle type, over all accessible two primary beam targets and an arrav of low- energies. energy secondary beams and spectromi. icrs. • Area H will receive the main ring beam via slow extraction and will be a new high-energy area Project Schedule and Costs with two primary targets. Detailed cost estimates and project schedules have • Area N will receive the booster beam via fast been prepared by Los Alamos personnel and external extraction, providing facilities for neutrino and consultants. This proposal is supplemented by com- pulsed muon physics. panion documents prepared by our consultants. The design of these facilities emphasizes A consulting team from Science Applications In- • high beam intensity; ternational Corporation (S1AC) has prepared a com- • high beam brightness: plete work-breakdown and cost estimate, including • high beam purity; engineering design and inspection (ED&I), installa- • high resolution for nuclear physics: tion, project management, and 25% contingency. The • high beam availability: costs, in January 1985 dollars follow. • multiple ports: • complete coverage of all the beam energies and Dollars particle types available at LAMPF II, including (in Millions) v. A', rt. u. />. and polarized protons; and • Booster 120 • flexibility to meet the requirements of future • Main Ring 160 physics experiments. • Experimental Area N 29 The areas are conservatively designed, building • Experimental Areas A and H 143 especially on the extensive experience at LAMPF in transporting and targeting high-intensity beams. At- The construction schedule contained in the SIAC tention has been paid to reducing costs through the Management Plan and Schedule Report and in the use of such techniques as underground areas to re- Preconccptual Site Plan prepared by Parsons, duce shielding costs, shared primary beam target Brinkerhoff, Quade. and Douglas call for construc- cells, and careful choice of remote-handling tech- tion to be completed in 1994, given a 1988 start. nology. Neutrino area beams will be usable in 1992, with all The beams to be provided will include beams in production in 1995. Area N: • neutrino source, with pion focusing horn, and Unique Resources of Los Alamos National • pulsed muon channel; Laboratory and the User Community Area A: • 0.4- to 0.8-GcV hypernuclear and stopped kaon LAMPF II will provide the nuclear science com- beam. munity with an essential capability for its attack on • 0.7- to l.2-GeV/c kaon beam and spectrometer. ihc frontier problems of nuclear and particle physics. • l.O- to 2.0-GeV/c kaon beam and spectrometer. To be assured that this powerful capability is de- • 2- to 10-GeV/c kaon and antiproton beam. veloped with utmost efficiency, building on scien- • wide-band neutral kaon beam. tific, technical, and managerial capabilities essential • stopped muon channel, and to the endeavor and already in place, the resources, • test beam; and people, facilities, and expertise at Los Alamos will be 214 PROGRESS AT LAMPF—1984 crucial. The scientific accomplishments of the nu- existing high-energy, low-intensity facilities, to ensure clear and particle physics programs at LAMPF and the utility and reliability of the facility. The technical the development of the scientific interests of this expertise at LAMPF in materials science, radiation- community are consistent with the goals of the hardened components, remote handling, beam trans- LAMPF II program. port, and shielding are unique national resources. The Clinton P. Anderson Meson Physics Facility Indeed, these abilities are well known to define the (LAMPF), the largest of the meson factories and the useful limits of any high-intensity accelerator labora- single largest facility in medium-energy physics, has tory. LAMPF has led the world meson-factory com- had as one of its major goals the bridging of the gap munity in each of these areas. between nuclear and subnuclear physics. This goal In addition to the technical and operational ex- was formulated during the early 1960s, and LAMPF perience acquired in operating a high-intensity labo- has carried out a broad program of ambitious re- ratory for more than 15 years. Los Alamos possesses search in both areas. That the frontier of nuclear unique assets. Embedded in one of the nation's larg- physics is once again intertwined with the intellectual est and most capable multidisciplinary laboratories, product of high energy-physics is not an accident. the medium-energy physics program at Los Alamos That the proposed extension of the LAMPF facility has long benefited from the extraordinary collection described in this document is once again concerned of scientific and technical assets that have been avail- with the overlap of these two fields is a natural able. The medium-energy program has supported, extension of the scientific and technical activities of critiqued, and reinforced, in crucial ways, these other the medium-energy research community. Indeed, programs as well. More specifically, the LAMPF during the last 5 years an extraordinary' dialogue accelerator surpasses any other facility as the injector between the two poles of medium-energy physics has for a new higher energy, high-intensity facility. The taken place in a series of important workshops—at existing LAMPF beams, and the new Proton Storage Santa Cruz in 1983. Steamboat Springs in 1984. and Ring provide unmatched facilities for developing and at laboratories in Canada, the United States, and proving prototype systems for the LAMPF II ac- Europe. LAMPF II will provide this community with celerator and experimental areas. the facilities and tools needed to probe the dynamics The intellectual challenges that have been pursued of nuclear matter with light-hadronn: probes and to by the community of researchers using the Los Ala- exploit nuclei and medium-energy beams and tech- mos facilities have been met with notable success. A niques that will test the limits of the models provided substantial record of achievement in scientific areas to us by high-energy particie physics. Thus. bridging the nuclear and panicle domain has been LAMPF II is the intellectual extension of the present- accumulated. The natural development of this day medium-energy physics effort. pursuit has quite properly followed the growth of new Furthermore, the technical challenges that must be interests and outlooks in nuclear and particle physics. met to construct and operate a high-energy, high- The intellectual goals of LAMPF II are the goals of intensity proton accelerator laboratory are domi- the medium-energy physics community. nated by the difficulties presented in the transport Apart from its intrinsic scientific merit. LAMPF II and targeting of high-intensity beams. The operation will continue our contribution to the nation by of LAMPF II will require the technologies painstak- providing an important part of the knowledge and ingly developed over the years at LAMPF and other people babo essential to our nation's security and meson factories, far more than those found at the well-being. FACILITY DEVELOPMENT

LAMPF Upgrade for the Table I is a comparison of the old and new situ- ations in the major subsystems affected by the up- Proton Storage Ring grade. Most of the changes are discussed in the The capabilities for pulsed neutron research at following sections, except for the PSR itself and LAMPF are being enhanced by adding a Proton the new (1984) transition region, both described in Storage Ring (PSR) to the Weapons Neutron Re- last year's Progress Report.' The table shows that the search (WNR) facility. This addition entails several PSR in the long-bunch mode, 12-24 Hz, replaces the major modifications to the accelerator in order to WNR fast-kicker mode. This achieves an ~103 in- support the operation of the PSR and still retain the crease in neutron flux per microsecond for slow- present level of flexibility in delivering beams to the neutron research. The new transition region permits o'her areas. Some facets of the upgrade include separate longitudinal and transverse tuning of H+ • a new high-intensity (20-mA-peak) H" ion source and H~/P~ beams between the drift-tube and side- and injector, coupled linacs. • a new H" beam-transport line leading to the drift- tube linac, Reference • a major rebuilding of the switchyard, and • a change in operating modes. 1. "Progress at LAMPF, January-December 1983," Los Alamos National Laboratory report LA-10074-PR (1983), pp. 172-190.

~~TABLE I. LAMPF Beam-Sharing Comparison Before and After the PSR. Area Old (1984) New (1985)~~

Injectors Injector A: H+ for Lines A and D New Injector B: H for Line D Injector area transport No fast beam switching H~/P~ fast switching Line D chopper in Hf line Line D chopper in H~ line Linac No competition for rf power H+ and H~ compete for rf power Time-shared dual energy Time-shared dual energy Transition region Separately tune H+ and P" Added constraint to tune H Switchyard Line D kicker Line D kicker excluding Lines A and X excluding Line X Line D can take end of macropulse Line D can take end of macropulse Line D Slow kick for Line E Long kick for Line E Slow kick for WNR with micropulsing Long kick for WNR with micropulsing Fast kick for WNR Long kick for PSR Short kick on standby and for PSR development

~~215 216 PROGRESS AT LAMPF—1984~~

H Injector magnets around the outer cylindrical surface. The R. L. York, R. S. Stevens, R. A. DeHaven. J. R. McConneil, end plates contain 4 rows of magnets to complete the E. P. Chamberlin, and R. Kandahan full-line-cusp geometry with 8 of the 10 rows. Two tungsten filaments (1.5 mm diameter by Introduction. The Proton Storage Ring (PSR) re- 170 mm long) are mounted in the end plates to quires a high-peak-current H~ beam for injection at provide primary electrons to produce the arc dis- 800 MeV. Consequently a new H~ injector for charge. The filaments are positioned so that most of LAMPF was required, capable of 20-mA-peak nor- the emission surface is in the magnetic-field-free malized emittance under 1 mm-mrad and reliable region. The filament holders are covered with boron operation at 10% duty facior. An accelerator version nitride cylinders with molybdenum caps to prevent of the multicusp, surface-production, negative-ion sputtering erosion of the holders. source has been developed and installed at LAMPF The cesium transfer tube, isolated from the source to meet these requirements. housing to limit its participation in the arc discharge, and the converter surface are made of molybdenum. Development of the New H~ Ion Source. The multi- The converter shaft is covered with quartz to reduce cusp, surface-production H" ion source was or- current drain on the converter power supply. Water iginally developed for neutral beam injectors at Law- cooling is provided to the filament holders, end rence Berkeley National Laboratory by Ehlers and plates, repeller, converter electrode, and magnets. Leung.' However, as their goal was a low-brightness The source housing is cooled only indirectly through 1-A beam and our goal was a high-brightness 20-mA contact with the individual magnet holders and typi- beam, the development program at LAMPF followed cally operates at 40°C. a different course, concentrating on increased brightness. Early experiments proved that the emittance of the extracted H~ beam was almost completely determined by the geometrical admittance of the ion CUSPED-FIELD MAGNETS source. This means that the ion beam produced on the surface of the converter electrode has sufficiently CONVERTER large emittance to fill the phase-space region determined by the aperture stops of the source. Thus, the emittance of the extracted FT ion beam is determined by the diameter of the converter (38 mm), the size of the exit aperture in the repeller electrode (10 mm), and the flight path from the converter to the exit aperture (126 mm), as shown in Fig. 1. All ion- source prototypes were built with geometrical admit- tances thai restricted the beam to a normalized emittance of < 1.2 mm-mrad (normalized means multiplied by Py/7u. where (3y = Lorentz factor = momentum/mass). In this geometry the curvature of the converter surface affects brightness. Initial studies have shown that a converter surface that is a spherical cap with a radius equal to the distance from the converter surface to the exit aperture yields ~ 25% more H~ cur- FILAMENTS CESIUM CELL & TRANSFER TUBE rent than a flat converter surface. REPELLER The final design of the multicusp surface-produc- ELECTRODE tion H~~ ion source is shown in Fig. 1. The source employs a cylindrical, stainless steel housing 200 mm FIGURE 1. The multicusp, surface-production H in diameter and 230 mm long, with 10 rows of ion source. FACILITY DEVELOPMENT 217

The H ion beam is extracted through a break in cusped field in the extraction region rejects almost all the cusp-field confinement geometry. The magnets of the secondary electrons formed on the converter are positioned symmetrically around the source while only slightly shearing the extracted H" ion housing, extending the length of the cylinder except beam in the horizontal plane. However, as the beam along the beam axis. Here, a section of 2 line-cusp is much larger than the extraction aperture, this magnet has been removed and replaced by two shearing action does not affect the JC-.V symmetry of similar magnets positioned above and below the the extracted beam and only introduces a few per cent extraction aperture in a symmetric manner, as shown emittance growth in the horizontal plane. in Fig. 2(a). This magnet arrangement essentially re- The source is operated with the arc pulsed rather tains the plasma-confinement geometry while than dc, which helps extend filament lifetime and providing an almost magnetic-field-free path for apparently allows the converter to become recoated beam extraction. All of the magnets around the with cesium while the arc is off. Starting the arc with a cylinder and the end plates are samarium-cobalt high-voltage spike improves turn on and permits magnets except those in the area of the beam axis, lower arc power and gas flow. which are Alnico-8 magnets. Plots of the magnetic Cesium is transferred continuously onto the con- field on axis and at one edge of the extraction verter through a tube from the cesium oven. aperture are shown in Fig. 2(b). The small dipole- Molybdenum has been proven to be the best converter material, based on H" yield and resistance to

~~(a)~~

~~CUSPED-FIELD PLASMA REPELLER MAGNETS ELECTRODE~~

~~OIPOLE CUSPED-FIELD MAGNETS~~

~~EXTRACTION APERTURE~~

~~150~~

~~100 BOTTOM EDGE FIGURE 2. OF (a) The dipole, cusped-field magnet arrange- 50 EXIT APERTURE ment at the exit of the source. CO (b) Plots of the magnetic field along the beam CO axis.~~

~~-50 ON AXIS~~

~~-100~~

-150 8 12 16 20 Z AXIS (cm) 218 PROGRESS AT LAMPF—19S4 sputtering.2 Beam brightness proved very dependent included in the dome transport line to permit source on converter diameter as well as on arc current. The operation at constant duty factor. present design operates at 60-A arc current and has a The ion source, its power supplies, control system, 38-mm-diam converter. The performance of the and the beam-transport system are housed in a 3.4- source is now a 20-mA H~ beam with a normalized by 4.6- by 3,4-m Cockcroft-Walton high-voltage emittance of H& mm-mrad. equipment dome. Alternating-current power is supplied to the dome through a two-stage isolation trans- Lifetime Tests. The source liftlwne at full current former. The operating power requirement is -36 and 10% duty is ~200 h and is limited by failure of kW. The dome transport system is sketched in Fig. 3. the filaments. Burnout occurs at the center of the filaments shortly after a 6% reduction in filament Injector Control System. The primary control sys- diameter occurs. If thermal evaporation of filament tem uses a microcomputer and CAMAC crate at material were the only factor in determining loss of ground level, a crate in the 650-kV dome, and a third filament material, a lifetime more than 50% longer crate in the 100-kV enclosure, all connected by fiber would be expected. Therefore, the observed lifetime optic data links. The computer displays and controls implies that sputtering by plasma ions is responsible the binary and analog settings from the injector con- for one-third of the material loss of these filaments. trol room. The operator interface is through a display Because initial operation will be at reduced current screen format similar to the line-by-line format in the and duty, source lifetime should be tolerable until Central Control Room (CCR). The dome hardware improved filaments are developed. configuration is mapped in a channel table in the computer, as at CCR. Some high-voltage transient H~ Injector and Transport. The H~ cusp-field ion protection was added to the dome-level modules. source was designed to minimize the ratio of electron Resistance to damage from arc downs has been ex- current to extracted H~ current. The slightly positive cellent. A back-up control system, "Injector Local (+2 V) biasing of the repeller electrode at the exit of Control," is also installed. the source reduces the extracted electron current to 25% of the H~ ion current. However, even this rel- Injector Operation. Injector commissioning in- atively small current could be a potent source of volved solving a number of difficult problems with x rays at an energy of 750 keV. This problem was transients from the high-power and high-voltage avoided1 by using an intermediate stage of accelera- components. Most troublesome were 100-kV arc tion to 100 keV followed by magnetic analysis. This downs. Several modifications, such as adding series solution also offered the opportunity to incorporate resistance to the 100-kV supply, have made the prob- instrumentation and emittance-matching equipment lem manageable. Activities will now concentrate on upstream of the 650-kV main column. A deflector is achieving reliable operation at modest current and

~~DEFLECTOR PLATES BENDING MAGNET STEERINGMAGNET STEERING MAGNET SO'LENOIDAVALVE VALVE • ELECTRON TRAP~~

~~STEERING MAGNET WIRE SCANNER CURRENT ION SOURCE SOLENOID MONITOR~~

FIGURE 3. Beam-transport line inside the high-voltage equipment dome. FACILITY DEVELOPMENT 219 duty for initial DSR operation. The upgrade to full 2. R. L. York and R. R. Stevens, Jr., in "Proceedings of current will follow. the Third International Symposium on the Produc- tion and Neutralization of Negative Ions and Beams," Brookhaven National Laboratory report (November 1983), p. 410. References 3. R. R. Stevens, Jr., R. L. York, J. R. McConnell, and 1. K.. W. Ehlers and K. N. Leung, Review of Scientific R. Kandarian, in the Proceedings of the 1984 Linear Instruments 51, 721(1980). Accelerator Conference, Seeheim/Darmstadt, West Germany. May 1984, Los Alamos National Labora- tory document LA-UR-84-1234.

H Transport Line 3. the new line had to transport a high-intensity //. S. Butler H" beam without degrading its quality, that is, without inducing a significant growth in its The starting point for the design of the new H~ line emiuance. was the old injector area transport system, sketched Figure l(b) shows the design for the transport in Fig. l(a). There was strong motivation to preserve system that emerged after all the competing require- as much of the present system as possible to mini- ments were resolved. The essential features of the mize the cost of the upgrade without compromising + design were proposed by Mark Jakobson, a LAMPF H operation. On the other hand, there were three consultant from the University of Montana. new requirements on the H" line: Requirement /, multiplexing the P" and H~ beams 1. the new system had to switch between P~ and on the same macropulse, was satisfied by introducing H~ sufficiently rapidly to share one rnacropulse, an electrostatic inflector at the intersection of the P~ as shown in Fig. 2(a); and H~ lines. When the infle<~*or is energized, the P~ 2. the H~ line had to provide special beam time beam is delivered to the accelerator. The inflector structures for various Weapons Neutron Re- voltage is to have a 40-us fall time, so that the line can search (WNR) facility and Proton Storage Ring be switched to H~ during the same time a kicker (PSR) operating modes, which required fast magnet in the switchyard is energized to deliver the gating and programmable micropulse chop- beam to the PSR. ping, as shown in Fig. 2; and 220 PROGRESS ATLAMPF—19S4

~~H* INJECTOR~~

~~MECTOH~~

~~•a- SPIN PftECESM~~

~~(a)~~

~~H*LINE~~

~~POLARlMETER PREBUNCHER POLARIZED LINE~~

~~(b)~~

~~11.95 m~~

FIGURE 1. (a) The old injector area transport system, (b) the design for the new system, and (c) the H~ transport design beam envelopes. The previous injector area transport system had no provision for fast switching between H~ and polarized (P~) injectors; the new system has an electrostatic inflector to switch between H~ and P~. The modulator function in the deflector permits slow turn on of the H" current pulse by modulating the microstructure. The chopper can add any repetitive micropulse structure to the macropulse. FACILITY DEVELOPMENT 221

~~K- (0) SHORT KICK AREA A~~

~~-LINE D~~

~~16) —H 750 fit I— LONG KICK FOR PSR~~

~~AREA A~~

FIGURE 2. Some possible beam time structures from injector transport: (a) fast beam switching between H" and P" with H+ truncated before H" high intensity starts and (b) the P~/H~ switching between macropulses. One macropulse is H with chopping pattern for PSR injection.

Requirement 2, time structuring, implied the addi- emittance would not grow significantly from space- tion of a low-frequency (16.77-MHz) buncher and a charge effects. The beam profile calculated for the fast rise-time (5-ns) chopper. Component placement new H~ line adheres to these guidelines, as seen in was critically tight. To make space for these devices, Fig. l(c). the two 45° bending magnets were collapsed into a In addition to the equipment depicted in Fig. l(b), single bend of 90 — 9 = 81 °. Because the buncher adds there are seven steering magnets in each plane, six a large beam energy spread, it had to be located current monitors, and four emittance stations to downstream of the highly dispersive bend; the chop- verify the beam profile along the line and to ensure per is upstream. The 9° bend to the accelerator center that the beam entering the linac is properly matched. line was a compromise that keeps the dispersion at an After the design goals for the H" line were satisfied, acceptable level but allows enough separation be- the H+ and P~ lines were modified to conform to the + tween the H~ and H lines for the focusing elements. new design with a minimum number of changes. In Requirement 3 was satisfied by judicious place- the P~ line, a deflector was added to permit source ment of the quadrupole lenses along the beam. The operation at constant duty factor regardless of ac- beam optics with space charge was studied using a celerated beam duty, and a 750-keV polarimeter 1 code developed by Mark Jakobson and Robert Hay- system [using the 6Li(/?,He) exothermic reaction] is den of the University of Montana. These calculations being developed. showed that if the minimum size of the beam were October 22, 1984, was the starting date for the kept larger than a 4- to 5-mm radius and if the peak- shutdown to upgrade the PSR. The whole system is to-valley ratio (maximum beam size ratioed to the scheduled for completion by mid-February, allowing next smaller waist) were kept less than 4:1, then the 222 PROGRESS AT LAMPF—1984

2 months for development before the start of the next sign for the new switchyard allows compromise tun- production cycle. ing of the two H~ beams fur near-maximum transmission and appropriate matching into Lines D and X without degradation of the H+ beam for Line A. Reference 1. R. J. Hayden and M. J. Jakobson, "The Space Charge Design Considerations in the New Switchyard. Fig- Computer Program SCHAR," IEEE Transactions of ure 1 is a sketch of the revised portion of the Nuclear Science NS-30 (4), 2540-2542 (1983). switchyard. The separation of H+/H" beam is achieved in the first 4.5° bending magnet. The H+ beam is then transported by means of the overhead dogieg to Line A. The high-intensity H~ beam is Switchyard deflected into Line D by the pulsed 1.15° kicker D. Fitzgerald magnets, which have 40-us rise times to permit fractional use of a macropulse.' The separation of the H~ Introduction. Before the construction of the beams is then completed by the 4.55° septum magnet. Proton Storage Ring (PSR), the H* beam was The P~ beam for Line X. which is on only when the directed toward Line D by a kicker magnet upstream kicker is off, drifts through the field-free region of the of the dc magnets separating H~/P~ for Line X and septum magnet. H+ for Line A. With PSR operations, H~ will be sent down Line D; therefore, a major reconfiguration of The first important design criteria were simplicity the beam-splitting system was required. In the new of operation and sufficient flexibility to produce configuration, the separation of H+ and H~ beam is high-transmission tunes simultaneously for all three still accomplished by means of a dc magnet. The H" beams. The second consideration has the greatest beam for Line D is then separated from that for Line effect for the two H~ beams because they share a X by means of a pulsed kicker magnet followed by a relatively large number of beam-transport elements septum magnet. The time-sharing constraints now and because the energy of the Line X beam is variable also are considerably different. The beam optics de- between 200 and 800 MeV. Extensive beam optics

j^-fiE*

~~-~H«(UNE A)~~

~~ELEVATION VIEW~~

FIGURE 1. Horizontal and vertical views of the new switchyard. The H+ and H~ beams are separated by a 4.5° vertical (V) bend; FT and P~ are separated in the horizontal (H) plane by the kicker (KI) and the 4.55° septum magnet. For clarity, the plan view omits the overhead portion of Line A. FACILITY DEVELOPMENT 223 studies indicate that the new design will provide References acceptable tunes for both lines and for all energies in 1. G. A. Sawyer, "Progress at LAMPF, January-Decem- Line X for a wide variety of initial beam parameters. ber 1983," Los Alamos National Laboratory report Beam losses can occur because of (1) magnetic field LA-10070-PRO984), pp. 173-174. errors that give rise to effective emittance growth of 2. D. H. Fitzgerald, "Magnetic Field Criteria and beam halos or (2) stripping of H" ions to neutral or Measurements in the Revised LAMPF Switchyard," positive charge. to be available in a Los Alamos National Laboratory Upper limits for field errors were set by requiring LA-UR document. that the resultant angular deflection in the beam halo be less than the rms angular divergence of the beam. (The defining apertures for the high-intensity beams were designed to be a minimum of 7 times the beam Beam Time-Sharing Considerations rms radius. It is useful, therefore, to use this defini- J. Bergstcin tion, 7o\ as the halo radius.) This leads to fairly stringent field uniformity requirements for the Before the spring 1985 operating cycle, the Line D magnets. These requirements were typically ±0.05% kicker magnet was in a section of the switchyard in the integrated fields of bending magnets over an beam-transport area common to both positive- and appreciable fraction of the field volume and, for negative-ion beams. Consequently, any beam time quadrupole magnets, <1% for higher multipole com- assigned to Weapons Neutron Research (WNR) fa- ponents. Similar considerations of the centroid shifts cility operation reduced beam duty factors available produced by magnet misalignment showed that suffi- to Experimental Area A (H+) and the HRS and NPL ciently good alignment can be obtained using or- area (H~ or P" in Line X). dinary techniques. With the new switchyard beam-transport layout, H~ beam stripping is minimized by keeping mag- the Line D kicker magnet affects only negative-ion netic fields under ~4 kG and by having vacuum of at beams. Any beam diverted to Line D for use by the 7 least 10~ torr. The field constraint sometimes re- Proton Storage Ring (PSR), WNR, or Line E directly quired longer magnetic elements. reduces full-energy beam duty factor available to the Simplified operation is especially helped by early Line X nucleon areas. Because of rf power limita- separation of H+ and H~ beams. The design approach tions, LAMPF cannot accelerate two high-intensity was to achieve separated functions, permitting se- beams simultaneously. Therefore, any high-intensity quential rather than coupled adjustments. beam delivered to Line D will also directly reduce the Instrumentation will be basically the same as in the H+ duty factor available to Area A. old switchyard. Toroidal current pickups will For at least the next year, the PSR will operate only measure beam current, and wire scanners will in the long-bunch mode, injecting high peak current measure profiles. Because beam emittances will be and delivering beam to WNR target 1. WNR target 2 obtained by calculation from the beam profiles, the will operate in the micropulse mode, using low- wire-scanner locations were chosen with this in intensity beam. Line E may use either high- or low- mind. Ion-gauge vacuum monitors have been added. intensity beam. Beam pulses to these three areas will be interlaced, with each receiving all or a part of one Construction and Installation. The new magnets or more macropulses each second. Chopping patterns were extensively mapped. A detailed description and will be imposed by a chopper control and pattern analysis of the results of the measurements will soon generator (CCPG) controlling a beam chopper in the 2 be available. Removal of the old switchyard compo- LAMPF H" low-energy transport. The present nents was completed in the first week of the 1984-85 Line D kicker power supply limits Line D to 20% of shutdown. Installation stayed ahead of schedule, and LAMPF beam duty factor. commissioning is eagerly awaited. 224 PROGRESS AT LAMPF—1984

A typical allocation of beam pulses under dual- monitored by the VAX analog of the SEL-840 line- energy operation would be (per second) 70 for Line A, by-line system for remote information and control 35 for Line X, 12 for PSR, and 3 for Line E. The equipment. This is a capability that the SEL-840 does micropulsed mode for WNR (low average current), not have. in addition, can run simultaneously with Line A and We had established an interim goal of being able to without reducing low-energy duty for Line X. sustain operations through the VAX in the event of During PSR commissioning and for other Line D the SEL-840 failure. The third operator's console was tuning and development there will be significant changed over to the VAX and equipped with touch periods when only a small portion of a LAMPF screens, equivalent to the push buttons on the old macropulse can be accepted. In this mode short consoles. We focused on a list of the minimal kicking will be used and the Line D beam pulse will necessary programs to be ready for a demonstration coincide with the last few microseconds of a normal run in August 1984. Although incomplete, the dem- H+ beam pulse, which will be truncated to avoid onstration showed that the SEL-840 was 3-4 times overloading the accelerating cavities. Beam pulses to faster in response than the VAX. Line X will be truncated 40 us before the start of each Following this demonstration a relatively simple Line D pulse to allow for Line D kicker turn on. change was made to the VAX control-system soft- In summary, the expected normal mode of PSR ware that made an across-the-board improvement of operation will reduce Lines A and X duty in equal 2 in the speed of the VAX system. One of the proportion, nominally 10%, in both single- and dual- concepts that the VAX system was built on was to energy production. centralize as much as possible those functions that are common to many of the control application programs. The change that was made was at the Central Control Computer center of the data-taking routines and thus made a S. Brown global improvement. Now that the operational software is mostly in The project to convert the accelerator control sys- place, we are concentrating on the list of tuning tem from the present SEL-840 to a Digital Equipment programs. Many of these will be ready by the time Corp. (DEC) VAX-11/780 passed two milestones this Proton Storage Ring (PSR) tuning begins. At that year. This required that most of the fundamental time the VAX will move into production status. control system supporting applications programs be Many of the programs required to run the "new" finished. accelerator will be found only on the VAX. We are In January 1984 the VAX program STAT beginning to look forward to turning the SEL-840 off. (analogous to the SEL-840 program 734) was used by operators to monitor beam and rf status and to turn beams on and off. The demonstration provided some feedback from operations concerning ease of use and Target-Cell and Beam-Stop functionality, with the result that improvement of Replacements system rcsponse lime surfaced as a major issue. Following this demonstration, the emittance pro- The Area A target cells were first rebuilt for high- gram on the VAX was used for the development of intensity beam during the Great Shutdown of the new high-intensity H~ ion source. It was opera- 1974-75. In the spring of 1983 the A-2 target cell was tional, for H~ only, by its target date of April 9 and replaced, in the spring of 1984 the A-l target cell was had full functionality by June 1. At about this time replaced, and in the winter 1984-85 shutdown the the VAX control system became capable of handling beam-stop area A-6 is being totally rebuilt. The fol- devices that are found in CAMAC crates as well as lowing article describes the A-2 job: it is based on a devices that are much more intelligent combinations conference report' that received the best paper award of hardware and software in the various remote from the American Nuclear Society. The second computers. Both of these types of devices can be article is a report on the A-6 upgrade. FACILITY DEVELOPMENT 225

A-2 Target Cell The new target-chamber design concept is shown D. L. Grisham andJ. E. Lambert in Fig. 1. The cylindrical design is superior to the original rectangular design from the standpoint of In 1982, water and vacuum leaks at A-2 began thermal gradients and associated thermal stresses. developing at a rate that presented serious operating The cooling of the copper collimators is by helical problems. Much of the instrumentation became in- water passages machined in the copper, and the main operable, and the cooling water flow had to be re- shell is cooled by water passages in the annular space duced to minimize leakage. To continue running it between the inner and outer jackets. Vacuum joints was necessary to install a thinner target to com- in high heating areas (near the target) were eliminated pensate for the reduced cooling. Although repairs by moving them to the outer end of the collimators, were continually made, reliability of the A-2 target which were made into an integral part of the cell was compromised to the point where total re- chamber. placement of the target chamber became the only The problem of building to match the five vacuum viable solution. ports in the actual target cell was met by making an The original target chamber was rectangular in alignment transfer fixture that could be adjusted, shape with brazed copper cooling coils on the outside using remote handling, to mate ts the flanges in surfaces. Most of the water-leak problems were due to place; the fixture could then be removed and used as cracking of the copper tubes at or near the braze a model for the target-chamber fabrication in the joints. Vacuum leaks at the joints connected to down- shop. stream and secondary-line collimators were a com- Starting in January 1983, faulty components were mon occurrence from high-temperature thermal cy- stripped from the target cell. New doublets for P3 and cling. A new design concept was required, plus a SMC and a new target-cell triplet were put in place scheme to ensure that the rep'acment would precisely with their new beam pipes and flanges open. Next, match the five existing vacuum ports—the main the alignment transfer fixture was placed in the eel! 1 beam pipe entrance and exit, pipes to P and SMC, with its five flanges matched to the outgoing pipes and the target-insertion location. and ports. Then the fixture was removed and used to

~~-SHIELD DRIVE FLANGE~~

~~PVDS COLLIMATOR SMC COLLIMATOR~~

~~TO SMC~~

~~PROTON' BEAM COVER~~

~~FIGURE 1. Sectioned isometric view of the A-2 target cell. 226 PROGRESS AT LAMPF—1984~~

make a mating assembly jig, which represented the • a containment "box" surrounding the target cell. five outgoing ports but now in a radiation-free en- Its purpose is to retain activated gas to allow vironment. Flange alignment on the new chamber radioactive decay; was made true to the assembly jig and checked in • handling of activated components with a place once before removal for the final welds. specially designed, remotely operated shielded The development of these techniques illustrates cask; the advanced state of remote-handling concepts and • improved biological shielding and the elimina- techniques achieved at LAMPF to support reliable tion of voids and cracks in support of the neu- operation with a proton beam current near I uA. trino experimental program. Additionally, the neutron shielding for the neutrino-electron scattering experiment was improved by the replace- Reference ment of some of the steel shielding by depleted I. D. L. Grisham and J. E. Lambert, "The Remote uranium; Replacement of a Target Cell at LAMPF," Los Ala- • improved capability for neutron and proton ir- mos National Laboratory document LA-UR-1626 radiation studies, nuclear chemistry studies (1984). (helium-gas jet and an improved fast "rabbit" system), and solid-state physics; • improved diagnostics by relocating sensitive Upgrade of the electrical connections to a less hostile environ- A-6 Target/Beam Stop ment free of radiation; D. L. Grisham and W. E. Sommer • placement of cooling water services in an accessible area; and Design of the major components for an upgrade of • placement of control and monitoring equipment target station A-6 has been completed. This design in a beam-on accessible area. emphasized and included the following features: These features are shown in Fig. 1. • vertical insertion and extraction of components, Fabrication of major components will be complete each on a separate biological shield insert; in January 1985. The present A-6 target cell is being • services, such as cooling water and instrumenta- prepared for the new installation by use of remote tion, for each component provided from an ac- handling, and installation will take place January cessible area at the top of the target station; through April.

~~INSTRUMENTATION CLOSED LOOP HELIUM SYSTEM~~

~~WATER COOLING MANIFOLD~~

~~FIGURE 1. Sketch of beam-stop assembly.~~

~~ISOTOPE PRODUCTION TARGETS BEAM DEGRADED PROFILE MONITOR PROTON IRRADIATION EXPERIMENTS~~

~~VACUUM TO AIR WINDOW ACCELERATOR OPERATIONS~~

This report covers operating cycles 40 and 41. The accelerator was in operation from December 6, 1983, TABLE I. Beam Statistics for Cycles 40 and 41. through February 3, 1984, and again from June 18 Cycle 40 Cycle 41 through October 22, 1984. Beams were provided for research for 165 days and for experimental area de- Number of experiments served 30 52 velopment for 1 day. A summary of information on H+ scheduled beam (h) 1266 2356 the beams provided is given in Table I. scheduled beam (h) 1242 2352 + Machine operation was smooth, with H beam + 0 intensities ranging up to 950 uA. Reliability was H beam availability (%) 70" beam availability (%) 76" poor, however, especially during cycle 41, with a few major failures causing significant amounts of down- H+ average current (uA) 755 815 time. The worst of these was a water-to-vacuum leak average current (nA) 10 10 at the A-6 window that necessitated its replacement H+ beam duty factor (%) 7-10.5 7-10.5 and cost 10 days of downtime to Area A. A large P~ beam duty factor (%) 3-10.5 3-10.5 water leak on the quad triplet downstream of the A-5 + "These numbers represent beam availability for the original sched- target forced a reduction in H beam intensity. High ule for cycle 41, which was to end October 1,1984. Because of the temperatures at the rf window on tank 3 of the low beam availability, however, the facility was kept in operation Alvarez linac forced a reduction in duty factor to a for an additional 21 days, providing 2034 h of H+ beam and 2190 h maximum of 8%, and a momentary vacuum loss at P1 of P~ beam. These totals represent 86 and 93%, respectively, of the originally scheduled beam hours for cycle 41. destroyed the 10-cm profile monitor harps in Area A. A summary of unscheduled facility downtime during research shifts is given in Table II. Because some of the outages were concurrent, the total is greater A new experimental station, Line E, located just than the beam downtime. south of the Weapons Neutron Research (WNR) facility, received beam for the first time during cycle 41.

~~TABLE II. Unscheduled Machine Downtime from December 6,1983, to October 22,1984. Category Downtime (h) Per Cent of Total~~

201-MHz amplifiers and transmission lines 196 15 805-MHz amplifier systems 127 10 Vacuum leaks 370 29 Magnets 90 7 Magnet power supplies 43 3 Interlock systems 28 2 Ion sources and Cockcroft-Walton hv supplies 202 16 Cooling-water systems 23 2 Computer control and data acquisition 61 5 Production targets 56 4 Power interruptions (lightning and other causes) 97 7

~~TOTAL 1293~~

~~227/^ MILESTONES CLINTON P. ANDERSON MESON PHYSICS FACILITY~~

1968 Official Ground Breaking February 15, 1968 Spinoff: Adoption of LAMPF Accelerating Structure for X-Ray Therapy and Radiography Machines ca 1968 1970 5-MeV Beam Achieved June 10, 1970 Adoption of a LAMPF-Standard Data-Acquisition System August 1970 1971 100-MeV Beam Achieved June 21, 1971 211-MeV Beam Achieved August 27, 1971 1972 800-MeV Beam Achieved June 9, 1972 Spinoff: First Use of Electrosurgical Forceps in Open-Heart Surgery (University of New Mexico) September 13, 1972 Discovery of -36Th (Experiment Zero) September 25,1972 Dedication to Senator Clinton P. Anderson September 29, 1972 Spinoff: First Hyperthermic Treatment of Animal Tumors October 1972 1973 First H~ Injector Beam March 28, 1973 First Simultaneous H+ and H~ Beams May 4, 1973 Beam to Area B July 15, 1973 First Experiment (#56) Received Beam August 24, 1973 First Meson Production, Beam to Area A August 26, 1973 1974 Beam to Area A-East February 6, 1974 First Medical Radioisotope Shipment July 30, 1974 Usable 100-|iA Beam to Switchyard September5, 1974 Pi-Mesic Atoms with "Ticklish" Nuclei October 13,1974 First Experimental Pion Radiotherapy October 21, 1974 First Tritium Experiment (80 000 Ci) November 1974 Start of Great Shutdown December 24,1974 1975 New Precise Measurements of Muonium Hyperfine-Structure Interval and u+ Magnetic Moment 1975-77-80 Q Data-Acquisition Software Operational June 1975 Spinoff: First Use of 82Rb for Myocardial Imaging in Humans (Donner Lab, Lawrence Berkeley National Laboratory) June 1975 Spinoff: First Hyperthermic Treatment of Human Cancer (University of New Mexico) July 11, 1975 Accelerator Turn On August 1, 1975 229 230 PROGRESS AT LAMPF—19B4

~~MILESTONES (Cont.)~~

Acceptable Simultaneous 100-uA H+ and 3-uA H Beams to Switchyard September 14, 1975 Production Beam to Area B October 7,1975 1976 First Pions Through EPICS March 18, 1976 Production Beam in Areas A and A-East: End pf Great Shutdown April 5, 1976 Muon-Spin-Rotation Program June 1976 Spinoff: First Hyperthermic Treatment of Cancer Eye in Cattle (Jicarilla Reservation) June 3, 1976 100-uA Production Beam in Area A August 1976 Experiment in Atomic Physics (H~ + laser beam): Observation of Feshbach and Shape Resonances in H~ October 1976 Double Charge Exchange in I6O: LEP Channel October 5, 1976 Start Up of Isotope Production Facility October 15, 1976 HRS Operation Begins November 1976 Maintenance by "Monitor" System of Remote Handling Fall 1976 1977 Proton Beam to WNR March 12,1977 Polarized Proton Beam Available April 1977 Spinoff: First Practical-Applications Patent Licensed to Private Industry April 12, 1977 Pion Radiotherapy with Curative Intent May 1977 Proton-Computed Tomography Program June 1977 Experimental Results at Neutrino Facility July 1977 Cloud and Surface Muon Beams: SMC July 1977 EPICS Operation Begins August 1977 300-uA Production Beam in Area A Fall 1977 1978 AT Division Established January 1, 1978 it0 Spectrometer Begins Operation February 1978 Operation of Polarized-Proton Target Spring 1978 Successful Water-Cooled Graphite Production Target November 1978 1979 . Spinoff: First Thermal Modification of Human Cornea (University of Oklahoma) July 11, 1979 600-uA Production Beam in Area A November 1979 New Limit on u. —• ey December 1979 1980 Experimental Measurement of the Strong-Interaction Shift in the 2p-ls Transition for Pionic Hydrogen 1980-81-82 Commercial Production of Radioisotopes January 1980 Spin Precessor Begins Operation February 1980 Data-Analysis Center Operational April 1980 MILESTONES 231

~~MILESTONES (Cont.)~~

Variable-Energy Operation June 1980 Single-Isobaric-Analog States in Heavy Nuclei June 1980 Spinoff: First Use of S2Rb for Brain Tumor Imaging in Humans (Donner Lab,Lawrence Berkeley Laboratory) September 1980 Production of Fast Muonium in Vacuum Fall 1980 Double-Isobaric-Analog States in Heavy Nuclei October 1980 Focal-Plane Polarimeter Operational at HRS October 1980 Safety Award to LAMPF Users Group, Inc., for Working One Million Man-Hours Since 1975 Without a Disabling Injury October 27, 1980 New Measurement of Pion Beta Decay—Improved Test of Conserved-Vector Current November 1980 1981 First Excitation of Giant Dipole Resonance by Pion Single Charge Exchange March 1981 First Excitation of Isovector Monopole Resonance in l20Sn and '"'Zr by Pion Single Charge Exchange March 1981 Search for Critical Opalescence in J0Ca September 1981 1982 Average Beam Current of LAMPF Accelerator Established at 750 uA 1982 Staging Area Constructed 1982 Particle Separator Installed at SMC 1982 "Dial-a-Spin" Capability on Line B Permits Different Spin Orientations for HRS, Line B, and EPB Simultaneously 1982 Time-Projection Chamber in Operation 1982 Improved Test of Time-Reversal Invariance in Strong Interactions January 1982 Search for Parity Nonconservation in pp Scattering November 1982 dt Fusion Catalyzed by Muons November 1982 1983 LAMPF Accelerator Produces Proton Beam of 1.2 mA February 7, 1983 First Observation of vt,-e~ Scattering October 1983 Result for Asymmetry in ~pp Scattering Caused by Parity Violation: A,= (2.4 ± 1.1) X l(T7at800MeV November 1983 1984 Total Cross Section for v,,-e~ Scattering: 44 cr=l(T £v(GeV)cnr May 1984 Branching Ratio for u+ — e+e+c~ Probes Mass Range to 10 TeV October 1984 APPENDIXA LETTER FROM LAMPF USERS GROUP SUPPORTING LAMPFII

~~February 11, 1985 LAMPF Liaison Office Los Alamos National Laboratory Mail Stop H831 Los Alamos,New Mexico 87545 (505) 667-5759 (FTS) 843-5759~~

~~LAMPF USERS GROUP, INC. Dr. John P. Schlffer BOARD OF Chairman, Nuclear Science Advisory Committee DIRECTORS Axgoane National Laboratory 203 9700 South Cass Avenue~~

Chairman. Argonne, IL 60439 RoMrt Hedwme Dear Dr. Schiffer: Massachusetts institute ol Technology On behalf of the LAMPF Users Group, we want to convey our strong Pater 0 Barnes support for the "Proposal to Extend the Intensity Frontier of Carnegie-Mellon University Nuclear and Particle Physics to 45 GeV (LAMPF II)". The LAMPF users have been heavily involved since about 1980 in the efforts ..'times N. Bradbury to bring forward such a proposal. The LAMPF II Workshops, which Los Alamos Nation*! Laboratory helped so much to define the broad physics motivation for the Liaison Office proposal, were very well attended; at these meetings users con- S67-c051 tributed many of the crucial ideas that can now be found in George 6urisson polished form in the new proposal. Seeing the importance of a New Mexico Stcte unified attack on the fundamental problems of both strong- and University weak-interaction physics, we sought and received the advice of a Donald Geesaman wide cross section of nuclear and particle physicists through our Argonne National Science Policy Advisory Committee and its Nuclear Physics Laboratory Subcommittee. The vigorous discussion of new physics by these Charles Glasnausser committees proved invaluable in focusing our attention on the Ru'.gets University most important problems in contemporary nuclear and particle physics. It is these problems that are addressed in the new Bai'ry M Preedom University ot proposal; it is these problems which the present generation of South Carolina LAMPF users 'Jant to solve with LAMPF II.

JohnD Waiecka Stanlord university Our interest is LAMPF II grows naturally out of our present experimental programs at LAMPF itself. When LAMPF began, the pion, though obviously necessary in obtaining a microscopic description of many nuclear processes, nevertheless! seemed an exotic particle to manv low-energy nuclear physicists. It was enticing and has proved very exciting for many of these physicists to crosa this barrier and carry out experiments with the pion itself. The quark is the pion of the 1980s. The frontier of nuclear physics, the goal which is most exciting for the present generation of nuclear physicists and the one which will stimulate a new generation of nuclear physicists, is the resolution of the nuclear many-body problem in terms of both quark- gluon and nteson-nucleon degrees of freedom. To do this, we need abundant sources of quarks in many different manifestations, such as kaons, antiprotons, high-energy pions and protons, even as lambdas, sigmas, and very short-lived resonances propagating in nuclei. We need these beams as vital probes complementary to electrons and heavy ions. The very important electro-weak interaction studies that would be possible with LAMPF II have 233 234 PROGRESS AT LAMPF—13B4

~~Dr. John P. Schlffer —2— February 11, 1985~~

also been well documented. A significant number of LAMPF users have been involved for years In such experiments and are eager to take advantage of the extraordinary capabilities LAMPF II would offer.

The natural location for such a proton accelerator is Los Alamos. LAMPF is a superb injector for a higher energy, high-flux accelerator. The Los Alamos National Laboratory has unmatched technical resources available for building and operating an accelerator such as LAMPF II; these same resources will also provide critical backup tor the experimental program. Finally, and very impor- tantly for us, LAMPF is widely known as being particularly hos- pitable to outside users.

We believe that our strong support: for the LAMPF II proposal is representative of that of the great majority of the approximately 600 members of the LAMPF Users Group. We strongly urge that NSAC give the proposal serious and expeditious consideration.

~~Yours truly,~~

~~The Board of Directors, LAMPF Users Group~~

~~Robert Redwine, Chairman Donald GeeSaman~~

~~Peter D. Barnes Charles Glashausser_^~~

~~Barcy M. Freedom tUf'et/^ /,,~~

~~John D. Walecka~~

Cy: Dr. James E. Leiss, Office of High Energy and Nuclear Physics Dr. Enloe T. Ritter, Office of High Energy and Nuclear Physics CRM-4 (2), MS AI50 LAMPF Liaison Office File APPENDIX B EXPERIMENTS RUN DECEMBER 6,1983—OCTOBER 22,1984

~~Beam No. Channel Hours Experiment Title~~

~~225 NEUTRINO-A 3053 A Study of Neutrino Electron Elastic Scattering~~

~~267 ISORAD 3052 Preparation of Radlolsotopes for Medicine and the Physical Services Using the Lampf Isotope Production Facility~~

~~308 TTA 1025 An Attempt to Make Direct Atomic Mass Measurements in the Thin Target Area~~

~~400 SMC 1707 Crystal Box Search for the Rare Decays y+ e e e~, u + e Y, and u + +~~

~~401 LEP 324 Study of the Isobaric Analog Charge Exchange Reaction 15N(TT+,TT°)15O~~

~~P3 557 High Precision Study of the u+ Decay Spectrum~~

~~499 SMC 157 Muon Longitudinal and Transverse Relaxation Studies in Spin-Glass Systems~~

~~523 LEP 88 Study of 14C(TT+,TT°)14N Reaction~~

~~545 RADAMAGE-1 2628 Fusion Materials Neutron Irradiations - A Parasite Experiment~~

~~573 EPICS 149 Pion Scattering from 24Mg and 26'Mg~~

~~586 EPB 704 A Study of the Effects of Very Strong Electric Fields on the Structure of the H" Ion~~

~~607 LEP 383 Study of Isovector Giant Resonances with Pion Charge Exchange 235 236 PROGRESS ATLAMPF—1984~~

~~Beam No. Channel Hours Experiment Title~~

~~632 HRS 56 Can Proton Density Differences Be Extracted from Medium Energy p-Nucleus Elastic Scattering Data?~~

~~639 SMC 78 Muon Spin Rotation Study of Muon Bonding and Motion in Select Magnetic Oxides~~

~~640 SMC 99 Transverse and Longitudinal Field Measurements in Selected Ternary Metallic Compounds~~

~~649 HRS 88 *Be(p,Ti~) Reaction at 650 MeV~~

~~660 HRS 190 Measurement of Polarization Parameters for Ml Transitions in the 90Zr(p,p')90Zr and 116Sn(p,p')116Sn Reactions at 500 MeV~~

~~665 BR 699 The Measurement of the Initial State Spin Correlation Parameters C,, and Cg, in n-p Elastic Scattering at 500, 650, and 800 MeV~~

~~685 HRS 439 Spin Correlations in the Reaction p"(d", d)p at 500 MeV~~

~~690 EPB 45 Simulations of Cosmic-Ray-Produced Gamma Rays from Thick Targets~~

~~691 BSA-RAD 329 Simulation of Cosmic-Ray Production of Nuclides by Spallation-Produced Neutrons~~

~~705 P3 417 Study of Pion Absorption in ^e On and Above the (3,3) Resonance~~

~~708 EPB 1076 A Measurement of the Depolarization, the Polarization, and the Polarization Rotation Parameters and the Analyzing Power for Che Reaction pp + pit n~~

~~709 HRS 388 Measurements of A™, A—,, anandd AAgg.. iin the Coulomb Interference Region at 650 and 800 MeV APPENDIX B: EXPERIMENTS RUN 237~~

~~Beam No. Channel Hours Experiment Title~~

~~724 SMC 286 Measurement of the Lamb Shift in Muonium~~

~~727 BIOMED 706 Measurement of the Efficiency of Muon Catalysis in Deuterium-Tritium Mixtures at High Densities~~

~~741 HRS 163 Investigation of the Longitudinal-Spin Response of Pb and Implications of Spin-Transfer Form Factors for Nonnucleon Degrees of Freedom in Nuclei~~

~~748 EPICS 157 Measurement of (nn/np)2 for 2+ Transitions in T = 1 Nuclei~~

~~752 TTA 633 Tuneup of the Time-of-Flight Spectrometer for Direct Atomic Mass Measurements~~

~~756 EPICS 208 + - 4 if or IT Inelastic Scattering From He—An Examination of Isospin-Symmetry Breaking~~

~~761 HRS 119 Q Measurements at 650 MeV on 40Ca~~

~~768 HRS 84 Development of 0° Capabilities at the HRS Facility~~

~~769 BSA-RAD 1025 Proton Irradiation Effects on Candidate Materials for the German Spallation Neutron Source (SNQ)~~

~~770 BR 1738 The Measurement of np Elastic Scattering Spin Correlation Parameters with L- and S-type Polarized Beam and Target Between 500 and 800 MeV~~

~~774 HRS 120 Excitation of Giant Multipole Resonances in sh-Shell Nuclei via Medium Energy Proton Inelastic Scattering~~

~~776 LEP 949 Study of the 16O(ir+ ,n°p) Reaction~~

~~777 EPICS 643 Angular Distributions for DCX on ^C and 180 238 PROGRESS ATLAMPF—1984~~

~~Beam No. Channel Hours Experiment Title~~

~~778 EPICS 138 Continuation of the Study of the Ml Transition in Ca by the Inelastic Scattering of TT+ and~~

~~782 EPICS 125 Elastic Scattering of TT+ and IT" from 3He and 4He Between 88.5 and 194.3 MeV~~

~~787 BIOMED 707 Muon Channeling for Solid State Physics Information~~

~~791 EPICS 299 Isoscalar Quenching in the Excitation of 8" States in 52Cr~~

~~792 EPB 337 Measurement of Parity Violation in the p-p and p-Nucleon Total Cross Sections at 800 MeV~~

~~795 HRS 254 A Precision Test of Charge Independence~~

~~797 EPICS 309 The Study of Giant Resonances and Low-Lying Collective States In ^°Zr by Inelastic IT" and ir+ Scattering~~

~~803 HRS 130 Cross-Section and Analyzing-Power Measurements in the Ml, M2 Region in 9^Zr and 88Sr at 318 MeV~~

~~804 P3 1605 Measurement of the Asymmetry Parameter in TT~ + p •*• y + n Using a Transverse Polarized Target~~

~~809 EPICS 108 Study of (p~p) and (ir+p) Reactions with Epics~~

~~814 LEP 193 ir+/ir~ Nuclear Elastic Scattering from Ni and Sn Isotopes at Energies Between 30 and 80 MeV~~

~~815 EPB 241 Measurements of A^ , Sg., and A,, in pp pmr+ at 500, 580, 650, 720, and^800 MeV APPENDIX B: EXPERIMENTS RUN 239~~

~~Beam No. Channel Hours Experiment Title~~

~~825 P3 415 Investigation of the NA Interaction via p+D + PP+N~~

~~826 EPICS 635 Isospin Dependence of Nonanalog Pion Double Charge~~

~~832 EPB 157 Gamma Ray Angular Correlation for 12C(p,p')12C(15.U)~~

~~833 EPICS 203 Continuation of the Investigation of Large-Angle Pion-Nucleus Scattering~~

~~837 HRS 108 Measurement of Spin-Flip Cross Sections up to co on 40-MeV Excitation in 5BNi and *uZr~~

840 EPICS 298 Inelastic Pion Scattering from 160 at T = 120 and 200 MeV *

~~842 SMC 320 ySR Shift and Relaxation Measurements In Itinerant Magnets~~

~~843 EPICS 93 A Search for A»_ Components of Ground-State Nuclear Wave Functions~~

~~850 LEP 228 Study of the Mass and Energy Dependence of Low Energy Pion Single Charge Exchange at 0°~~

~~851 HRS 55 Search for Recoil-Free Delta Production and High Spin States in the 208Pb(p,t)206Pb Reaction at E = 400 MeV~~

~~852 P3 67 Measurements of (ir* ,N) Reactions on Nuclear Targets to Study the Production and Interaction of Ti-mesons with Nuclei~~

~~853 HRS 57 Measurement of Wolfenstein Parameter at 650 MeV and DE/dn at 500, 650, and 800 MeV for pd + pd Elastic Scattering 240 PROGRESS AT LAMPF—1984~~

~~Beam No. Channel Hours Experiment Title~~

~~859 P3 334 Study of the A Dependence of Inclusive Pion Double-Charge-Exchange in Nuclei~~

~~862 EPICS 60 Study of the Ml Transition in 88Sr by the Inelastic Scattering of ir+ and ir~~~

~~869 SMC 231 Higher Precision Measurement of the Lamb Shift in Muonium~~

~~871 BIOMED 282 Coincident Nuclear Gamma-Ray and ironic X-Ray Study of IT Absorption at Rest on C~~

~~875 BIOMED 481 Radiobiology of Pions~~

~~877 BIOMED 30 The Microdosimetry of Error Induction in Microelectronics~~

~~878 HRS 31 A Signature for Relativistic Density Squared Effects in Proton-Nucleus Scattering at 500 and 800 MeV~~

~~884 LEP 285 Pion Double Charge Exchange on at Low Energies APPENDIX C NEW PROPOSALS DURING 1984~~

~~No. Spokesmen Title~~

~~875 M.R. Raju Radiobiology of Pions Los Alamos~~

~~876 M.W. McNaughton Spin Transfer Measurements for NP Los Alamos Elastic~~

~~877 J.F, Dicello The Microdosimetry of Error Induction in Clarkson Univ. Microelectronics~~

~~J.F. Dicello,III Clarkson Univ.~~

~~878 G.W. Hoffmann A Signature for Relativistic Density Univ. of Texas,Austin Squared Effects in Proton-Nucleus Scattering at 500 and 800 MeV~~

~~L, Ray Univ. of Texas,Austin~~

~~879 G.W. Hoffmann Characteristic Difac. Signature in Univ. of Texas,Austin Large-Angle p + °Ca Elastic Scattering at 500 MeV~~

~~M.L. Barlett Univ. of Texas,Austin~~

~~880 G.W. Hoffmann Large Angle Triple Scattering Parameter Univ. of TexasjAustin Measurements for Elastic Hydrogen and Quasielastic Deuterium and Carbon Scattering at 800 MeV~~

~~M.L. Barlett Univ. of Texas,Austin~~

~~241 242 PROGRESS AT LAMPF—1984~~

~~No. Spokesmen Title~~

~~881 CD. Goodman Quasifree Axial Response Functions for Indiana Univ. Pb and 2H Using the (p,n) Reaction~~

~~J.B. McClelland Los Alamos~~

~~T.A. Carey Los Alamos~~

~~882 D.H. Fitzgerald Measurement of the Differential Cross Los Alamos Section for ir~p •>• Tr°nat 10, 20 and 40 MeV~~

~~J.D. Bowman Los Alamos~~

~~P.A. Heusi Los Alamos~~

~~883 B. Hoistad A Study of the Reaction Mechanism for the Gustaf Werner Inst. 2H(p\Y)3He Reaction at 800 MeV~~

~~G.S. Adams Univ. of South Carolina~~

~~884 H.W. Baer Pion Double Charge Exchange on at Los Alamos Low Energies~~

~~M.J. Leitch Los Alamos~~

~~885 G.Pauletta Measurement of K,. , for the f>p + Univ. of Texas,Austin dir+ Reaction at £ 30 and 800 MeV~~

~~M.M. Gazzaly Univ. of Minnesota~~

~~N. Tanaka Los Alamos APPENDIX C: NEW PROPOSALS 243~~

~~No. Spokesmen Title~~

~~886 F. Sperisen Measurement of Beam-Target Spin UCLA Correlation Coefficients in Elastic pd Backward Scattering~~

~~G.J. Igo UCLA~~

~~887 B. Aas Proton-to-Deuteron Polarization Transfer UCLA Measurement in Elastic pd Backward Scattering~~

~~F. Sperisen UCLA~~

~~888 A.L. Hallin Study of the- Decays IT •»• e v Y Los Alamos and IT + e e e~~~

~~889 S.B. Kaufman Correlations Between Coincident Charged Argonne Nat. Lab Particles Emitted in Pion-Nuclear Reactions~~

~~890 G.Pauletta Measurement of A., for the Reaction Univ. of Texas.Austin pp + dir+ at 350 and 400 MeV~~

~~M.M. Gazzaly Univ. of Minnesota~~

~~N. Tanaka Los Alamos~~

~~891 J.B. McClelland Development of Zero Degree Spin-Flip Los Alamos Measurements at HRS~~

~~S.K. Nanda Univ. of Minnesota~~

~~892 H.-J. Ziock A Study of the (iT+,TT+d) Reaction UCLA in bLi, Li, C, and JC 244 PROGRESS AT LAMPF—1984~~

~~No. Spokesmen Title~~

~~K.O.H. Ziock Univ. of Virginia~~

~~893 H.T. Fortune Pion Scattering from Ni Isotopes Univ. of Pennsylvania~~

~~J.D. Zumbro Univ, of Pennsylvania~~

~~894 A. Saha Study of the Neutron-Proton Quadrupole Univ. of Virginia Boson Densities in the Germanium Region~~

~~K,K. Seth Northwestern Univ.~~

~~895 A. Saha Study of the 1BA-2 Model Plus Univ. of Virginia Configuration Mixing in the Germanium Region~~

~~K.K. Seth Northwestern Univ.~~

~~896 N.M. Hintz A Test of the Dirac Treatment of Univ. of Minnesota Proton-Nucleus Inelastic Scattering~~

~~897 B.J. Dropesky Pion Single Charge Exchange in 7Li to Los Alamos the Isobaric Analog Ground State of 7Be~~

~~898 C.L.Morris Pion Elastic Scattering from - A Los Alamos Test of Charge Symmetry~~

~~899 J.D. Bowman A Measurement of the Neutron Deformation Los Alamos of 165Ho by Pion Single Charge Exchange~~

~~J.N. Knudson Arizona State Univ.~~

~~J.R. Comfort Arizona State Univ. APPENDIX C: NEW PROPOSALS 245~~

~~No. Spokesmen Title~~

~~900 B. Aas Spin-Rotation Measurements on ^0 and UCLA 208Pb at 320 and 650 MeV~~

~~G.J. Igo UCLA~~

~~M. Bleszynski UCLA~~

~~901 B.L. Roberts Radiative u-Capture in Boston Univ.~~

~~E. Austin Boston Univ.~~

~~902 F.W. Hersman Inelastic Scattering of 500 MeV Univ. of New Hampshire Polarized Protons from Sr: Determination of Neutron Transition Densities~~

~~K.K. Seth Northwestern Univ.~~

~~903 N.M. Hintz A Study of Transition Nuclei in the Rare Univ. of Minnesota Earth Region by Proton Inelastic Scattering~~

~~904 H.T. Fortune Mass Dependence of Nonanalog DCX Univ. of Pennsylvania~~

~~R. Gilman Univ. of Pennsylvania~~

~~905 B.M.K. Nefkens Elastic and Inelastic Scattering of UCLA ir= on H and He to Test Charge Symmetry, Compare Form Factors, and Investigate the Reaction Mechanism~~

~~906 H.T. Fortune DCX on 44Ca Univ. of Pennsylvania~~

~~R. Gilman Univ. of Pennsylvania 246 PROGRESS AT LAMPF—1984~~

~~No. Spokesmen Title 907 C. Glashausser Spin Excitations in 40Ca and 48Ca Rutgers Univ.~~

~~K.W. Jones Los Alamos~~

~~S.K. Nanda Univ. of Minnesota~~

~~908 K.K. Seth Angular Distribution for the Northwestern Univ. 42Ca(Tr+,O Ti (g.s.) Reaction at 290 MeV~~

~~909 K.K. Seth Excitation Functions for the ir+d -»• Northwestern Univ. pp Reaction~~

~~910 K.K. Seth Study of the Analog DCX Transition Northwestern Univ. 88Sr0r+,TT~)88Zr (17.2 MeV)~~

~~911 H.T. Fortune A Systematic Study of TT+ and TT~ Univ. of Pennsylvania Scattering to 2+j States in Ni, Zn, Ge, and Se~~

~~J.D. Zumbro Univ. of Pennsylvania~~

~~S.J. Seestrom-Morris Univ. of Minnesota~~

~~912 R.J. Peterson Transverse Elastic Scattering of Pions Univ. of Colorado from Odd-Mass Targets~~

~~913 R.J. Peterson Pion Charge Exchange to a Spin Univ. of Colorado Excitation..Using the Reaction~~

~~914 G.H. Sanders Measurement of the Analyzing Power of a Los Alamos Muon Polarimeter for Use in a Search for Muon Polarization in the D«cay K^ $ UU~~

~~W.W.Kinnison Los Alamos APPENDIX C: NEW PROPOSALS 247~~

~~No. Spokesmen Title~~

~~915 A. Fazely Double 6-Decay Matrix Elements for Lousiana State Univ. | 90 1 "inJ AiOTe and 1JUTe from nonanalog DCE Reaction~~

~~916 E. Bleszynski Nuclear Information from Small Angle UCLA p-Nucleus Elastic Scattering~~

~~G.J. Igo UCLA~~

~~M. Bleszynski UCLA~~

~~917 R.J. Peterson Pion Charge Exchange to Delta-Hole Univ. of Colorado States of Complex Nuclei~~

~~918 A. Saha Study of the Microscopic Structure of Univ. of Virginia the Calcium Isotopes~~

~~J.J. Kelly Univ. of Maryland~~

~~919 A. Saha Microscopic Structure of s-d Shell T=l Univ. of Virginia Nuclei~~

~~J.J. Kelly Univ. of Maryland~~

~~920 E. Piasetzky Study of the 3He(it",ir°p) Los Alamos Reaction by Detecting Neutral Pions and Protons in Coincidence~~

~~S. Gilad MIT~~

~~921 E. Piasetzky Study of the 3He, 3H (ir+, Los Alamos ir°p) Reactions by Detecting Neutral Pions and Protons in Coincidence~~

~~S. Gilad MIT « 248 PROGRESS ATLAMPF—1984~~

~~No. Spokesmen Title~~

~~922 G.R, Burleson DCX on Light Nuclei New Mexico State Univ.~~

~~H.T. Fortune Univ. of Pennsylvania~~

~~923 H.T. Fortune Pion Double Charge Exchange on 20Ne ^ Univ. of Pennsylvania 22Ne, and 40Ar~~

~~S. Mordechai Univ. of Texas.Austin~~

~~924 K.W. Jones Cross Sections and Analyzing Powers for Los Alamos Elastic and Inelastic Scattering of Protons from "N~~

~~S.J. Seestrom-Morrls Univ. of Minnesota~~

~~925 C.L.Morris Measurement of M and M for Los Alamos Tr ansitions to States ift °»" and~~

~~926 K.W. Jones A Study of 'Stretched' M4 Transitions In Los Alamos p-Shell Nuclei Using Intermediate Energy Polarized Protons~~

~~S.J. Seestrom-Morrls Univ. of Minnesota~~

~~927 J.A. Faucett Investigation of Non-Analog L^uble New Mexico State Univ. Charge Exchange Between 50 Metf and 120 MeV~~

~~J.D. Zumbro Univ. of Pennsylvania~~

~~928 G.W. Hoffmann ? + n quaslelastic Scattering from Univ. of Texas,Austin Deuterium~~

~~J.B. McClelland Los Alamos~~

~~M.L. Barlett Univ. of Texas,Austin APPENDIX C: NEW PROPOSALS 249~~

~~No. Spokesmen Title~~

~~929 R.D. Brown Crack Growth in 800 MeV Proton and Los Alamos Neutron Irradiated Alloy 718~~

~~930 J.R. Cost Radiation Damage in Samarium-Cobalt Los Alamos Permanent Magnets~~

~~R.D. Brown Los Alamos~~

~~931 B.E. Newman Radiation Effects in Optical Materials Los Alamos for the Free Electron Laser~~

~~R.D. Brown Los Alamos~~

~~932 J.R. Cost Radiation Damage in Magnetically Soft Los Alamos Crystalline and Amorphous Alloys~~

~~R.D. Brown Los Alamos~~

~~933 F. Irom Study of the Mass and Energy Dependence Los Alamos of Ultra Low Energy Pion Single Charge Exchange~~

~~J.D. Bowman Los Alamos~~

~~934 J.C. Peng Inclusive (ir,n) Reactions in Nuclei Los Alamos~~

~~J.E. Simmons Los Alamos~~

~~935 G.R. Ringo The Development of a Source of Argonne Nat. Lab. Ultra-Cold Neutrons at the Line E Beamdurap~~

~~J.D. Moses Los Alamos~~

~~936 D.R. Davidson Dosimetry Experiment to Characterize the Los Alamos Radiation Environment at LAMPF Target Station A-6 25G PROGRESS AT LAUPF—1984~~

~~No. Spokesmen Title~~

~~937 R»C Minehart The Reactions (it,it') and (it,ir'p) on Univ. of Virginia JHe and He at Energies Above the (3,3) Resonance~~

~~938 D.K. Dehnhard Measurement of Spin Transfer Observables Univ. of Minnesota in the 4He(p,p')4He reaction at 500 MeV~~

~~S.K. Nanda Univ. of Minnesota~~

~~939 J.B. McClelland Tests of a New Relativistic Impulse Los Alamos Approximation for Inelastic Proton Scattering at 500 MeV~~

~~J.R. Shepard Univ. of Colorado~~

~~T.A. Carey Los Alamos~~

~~+ 940 DnK. Dehnhard Elastic Scattering of ii and ir~ Univ. of Minnesota from *He at Large Angles~~

~~G.R. Burleson New Mexico State Univ.~~

~~941 D.E.MacLaughlin Muon Spin Relaxation Studies of Univ. of Calif..Riverside Disordered Spin Systems~~

~~R.H. Heffner Los Alamos~~

~~S.A. Dodds Rice Univ.~~

~~942 B.J. Dropesky Measurement of Low Energy Cross Sections Los Alamos for the ^CdT.irN)1^ Reactions~~

~~M.J. Leltch Los Alamos APPENDIX C: NEW PROPOSALS 251~~

~~No. Spokesmen Title~~

943 J.-N. Yu Microstructural Evolution and Mechanical Inst. of Atomic Engery,Chi Property Changes in 316 SS AS, and Mo under Irradiation with Different Displacement/Helium Production Rates and Ratios

~~W.F. Sotnmer Los Alamos~~

~~944 CM. Hoffman Feasibility Study for an Experiment to Los Alamos Search for Muonium & Antimuonium Conversion J.R.Kane College of William & Mary~~

~~VaW. Hughes Yale Univ.~~

~~945 C.F. Moore DCX on Nickel Univ. of Texas,Austin~~

~~K.S. Dhuga New Mexico State Univ.~~

~~R. Gilman Univ. of Pennsylvania~~

~~946 B.M.K. Nefkens Elastic Scattering on He UCLA~~

~~947 D.K. Dehnhard Measurements of Large-Angle Univ. of Minnesota Pion-Deuteron Scattering~~

~~G.R. Burleson New Mexico State Univ.~~

~~948 B.G. Ritchie Pion Absorption on Quasideuterons in Arizona State Univ. 6Li0r+,2p)~~

~~950 K.K. Seth Mass of the Extremely Neutron Rich Northwestern Univ. 252 PROGRESS AT LAMPF—1984~~

~~No. Spokesmen Title~~

~~951 M. Artuso A Systematic Search for Narrow Dibaryons Northwestern Univ. in the p" + d p + X Reaction~~

~~K.K, Seth Northwestern Univ.~~

~~952 K.K. Seth Measurements of Analog DCX on Ca and Northwestern Univ., Mg at Low Energies~~

~~953 M. Blecher Testing the Pion-Nucleus Optical VPI and State Univ. Potential Via Low Energy n~ Elastic Scattering APPENDIX D VISITORS TO LAMPF DURING 1984~~

Bjarne Aas, UCLA Gary S. Blanpied, Univ. of South Carolina David L. Adams, UCLA Marvin Blecher, Virginia Poly. Inst. & State Univ. Gary S. Adams, Univ. of Souih Carolina Elizabeth H. Bleszynski, UCLA EricG. Adelberger, Univ. of Washington David J. Blevins, Consuiiant. New Mexico Steven D. Adrian, Abilene Christian Univ. Charles L. Blilie, Univ. of Minnesota Richard C. Allen, UC. Irvine Carolus Boekema, Texas Tech Univ. John C. AHred, Consultant. New Mexico Joe H. Booth, Abilene Christian Univ. Peter W. F. Alons, Univ. of Colorado Michael J. Borden, New Mexico Inst. of Mining & Tech. Jonas Alster, Tel-Aviv Univ. DaegS. Brenner, Clark Univ. Aharon Amittay, Yale Univ. Herbert Breuer, Univ. of Maryland Alan N. Anderson, EG&G. Idaho Nance L. Briscoe, UC. Irvine Bryon D. Anderson, Kent State Univ. William J. Briscoe, George Washington Univ. Daniel H. Anderson, UCLA Mark D. Brown, Univ. of Texas Eduardo I. Andrade, Rice Univ. Michael A. Bryan, Univ. of Texas Hans-Jurgen Arends, Catholic Univ. of America Howard C. Bryant, Univ. of New Mexico Richard A. Arndt, Virginia Poly. Inst. & State Univ. James A. Buchanan, Rice Univ. Klaus-Peter Arnold, Univ. of Heidelberg William J. Burger, MIT Marina ArtUSO, Northwestern Univ. Barry L. Burks, Oak Ridge Daniel Ashery,Tel-A\i\ Univ. Michael G. Burlein, Univ. of Pennsylvania Ronald L. Auble, Oak R.ige George R. Burleson, New Mexico State Univ. Leonard B. Auerbach, Temple Univ. Marshall Burns, Univ. of Texas Naftali Auerbach, Tel-Aviv Univ. Mary J. Burns, Univ. of New Mexico David A. Axen, TRIUMF Augustine J. Caffrey, EG&G. Idaho Alireza Azizi, UCLA James A. Carr, Florida State Univ. Andrew D. Bacher, Indiana Univ. Gregory P. Casaus, New Mexico State Univ. Mark G. Bachman, Univ. of Texas Costas Cassapakis, Science Applications, Inc.. California Andreas Badertscher, Yale Univ. Kwai-Chow B. Chan, Texas Tech Univ. Stephen D. Baker, Rice Univ. Nicholas S, Chant, Univ. of Maryland Jon A. Bakken, Princeton Univ. Herbert H. Chen, UC. Irvine Barry Barish, Caltcch Huan-Ching Chiang, Inst. of High-Energy Physics, PRC Martin L. Barlett, Univ. of Texas Katherine W. C. Choi, Louisiana State Univ. David B. Barlow, UCLA/Northwestern Univ. Michael H. Clark, Rice Univ. Bernd Bassalleck. Univ. of New Mexico Benjamin L.Clausen, Univ. of Colorado Dana R. Beavis, W. Riversiue John M. Clement, Rice Univ. Michael E. Beddo, New Mexico Slate Univ. Anthony S. Clough, Univ. of Surrey Donald R. Benton, Univ. of Maryland Stanley Cohen, Drexel Univ. T. H. Bergeman, State Univ. of New York. Stony Brook Joseph R. Comfort, Arizona State Univ. Barry L. Herman, Lawrence Livermore Lab. Getievieve R. Comtet, Centre Nat. de la Recherche Sci. Fred E. Bertrand, Oak Ridge David C. Cook, Univ. of Minnesota Hans A. Bethe, Cornell Univ. William Cottingame, New Mexico State Univ. William W. Bewley, UC. Riverside Gerard M. Crawley, Michigan State Univ. Tarlochan S. Bhatia, Texas A&M Univ. Gerald G. Crough, UCLA Louis Bimbot, Univ. of Paris An-Zhi Cui, Inst. of Atomic Energy. PRC Terry J. Black, Abilene Christian Univ. Stephen T. Cummings, Univ. of Texas Leslie C. Bland, Indiana Univ./Univ. of Texas Richard E. Cutkosky, Carnegie-Mellon Univ. 253 254 PROGRESS AT LAMPF— J984

James A.. Dalton, Abilene Christian Univ. Robert VV. Garnett, New Mexico State Univ. Herbert G. Daniel, Tech. Univ. of Munchcn GilGatoff, r,:JT Gourisankar Das, Univ. of Virginia M. Magdy Gazzaly, Univ. of Minnesota Sunayana Datta, Temple Univ. Donald F. Geesaman, Argonne Alfred R. de Angelis, Rutgers Univ. Edward F. Gibson, California State Univ. Rene de Swiniarski, Univ. de Grenoble Shalev Gilad, MIT Dietrich Dehnhard, Univ. of Minnesota Ronald A. Gilman, Univ. of Pennsylvania Peter P. Denes, Univ. of New Mexico Grant A. Gist, Rice Univ. Arthur B. Denison, Univ. of Wyoming Michael Gladisch, Univ. of Heidelberg Kalvir S. Dhuga, NMSU/Univ. of Pennsylvania Charles Glashausser, Rutgers Univ. John F. Dicello, Clarkson Univ. George Glass, Texas A&M Univ. John F. Dicello III, Clarkson Univ. Roy J. Glauber, Harvard Univ. Byron D. Dieterle, Univ. of New Mexico A. S. Goldhaber, State Univ. of New York, Stony Brook W. Rodney Ditzler, Argonne Charles D. Goodman, Indiana Univ. Donald C. Dodder, Consultant, New Mexico Jeffrey S. Gordon, UCLA Stanley A. Dodds, Rice Univ. William Gorn, UC. Riverside George W. Dodson, MIT Kazuo Gotow, Virginia Poly. Inst. & State Univ. Peter J. Doe, UC, Irvine Scott C. Graessle, Abilene Christian Univ. Hermann J. Donnert, Kansas State Univ. Michael C. Green, Argonne Edward G. Donoghue, Rutgers Univ. Chilton B. Gregory, Univ. of New Mexico Minh V. Duong-van, Rice Univ. David P. Grosnick, Univ. of Chicago Mark J. Dwyer, Univ. of Pennsylvania Edward E. Gross, Oak Ridge Morton Eckhause, 'oil. of William & Mary Franz L. Gross, Coll. of William & Mary Jean-Pierre Egger, Univ. de Neuchatel William Haberichter, Argonne Andrew D. Eichon, UCLA Ronnie VV. Harper, Ohio State Univ./Univ. of Illinois Judah M. Eisenberg, Tel-Aviv Uni.. Carol J. Harvey, Univ. of New Mexico Mohammed Emadi-Babaki, George Washington Univ. Hiromi Hasai, Hiroshima Univ. Jon M. Engeiage, UCLA Rene Hausammann, UC. Irvine Peter A. J. Englert, Univ. of Koln John C. Hiebert, Texas A&M Univ. Adoram Erell, Tel-Aviv LJniv. Virgil L. Highland, Temple Univ. David J. Ernst, Texas A&M Univ. Daniel A. Hill, Argonne Debi J. Erpenbeck, Rutgers Univ. Roger E. Hill, Univ. of New Mexico Jorge A. Escalante, Univ of South Carolina Norton M. Hintz, Univ. of Minnesota John A. Faueett, New Mexico State Univ. /Univ. of Oregon Gerald VV. Hoffmann, Univ. of Texas Aii Fazely, Louisiana State Univ. Gary E. Hogan, Temple Univ. Raymond VV. Fergerson, Univ. of Texas Steinar Hoibraten, MIT Brian E. Fick, Virginia Poly. Inst. & State Univ. Bo Hoistad, Univ. of Texas Randall J. Fisk, Valparaiso Univ. Karl F. Holinde, Univ. of Bonn Gottfried Flik, Max-Planck Insl. Charles L. Hollas, Univ. of Texas Carlos A. Fontenla, New Mexico State Univ. Barry R. Holstein, Univ. of Massachusetts H.Terry Fortune, Univ. of Pennsylvania Daniel J. Horen, Oak Ridge Zeev Fraenkel, Weizmann Inst. of Science Masaharu Hoshi, Hiroshima University Bernhard J. Franczak, Gsellsch. fur Schwerionf. Ying-Chiang Huang, Temple Univ. Michael Franey, i 'niv. of Minnesota E. Barrie Hughes, Stanford Univ. Melvin S. Freedman, Argonne Vernoii W. Hughes, Yale Univ. Stuart J. Freedman, Argonne Jon R. Hurd, Univ. of Virginia Hiroshi Fujisawa, Univ. of Minnesota George J. Igo, UCLA Clyde B. Fulmer, Oak Ridge Shigaru Ishimoto, KEK Herbert O. Funstea, Coll. of William & Man.' Kazuo Iwatani, Hiroshima Univ. LAMPF VISITORS 255

Harold E. Jackson, Argonne Ta-Yung Ling, Ohio State Univ. Mark J. Jakobson, Univ. of Montana Jerry E. Lisantti, Univ. of Oregon Randolph H. Jeppesen, Univ. of Montana Stanley Livingston, Consultant, New Mexico Kenneth F. Johnson, Argonne Earle L. Lomon, MIT Steven E. Jones, EG&G, Idaho David Lopiano, UCLA JanKallncJET Daniel C. J. Lu, Yale Univ. John R. Kane, Coll, of William & Mary Henry J. Lubatti, Univ. of Washington Ju Hwan Kang, Univ. of New Mexico Malcolm H. Macfarlane, Indiana Univ. Klaus Kaspar, Gsellsch. fur Schwerionf. David J. Mack, Univ. of Maryland Thomas E. Kasprzyk, Argonne John R, Mackenzie, Florida State Univ. Sheldon Kaufman, Argonne Douglas MacLaughlin, UC. Riverside William B. Kaufmann, Arizona State Univ. Richard Madey, Kent State Univ. Robert A. Kenefick, Texas A&M Univ. Kazushige Maeda, Tohoku Univ. Steve H. Kettell, Yale Univ. Hansjuerg Mahler, UC, Irvine Aman U. Khan, UC, San Diego Karl G. Maier, Max-Planck Inst. George J.Kim, UCLA Paul A. Mansky, MIT Edward R. Kinney, MIT Jill Ann Marshall, Univ. of Texas Leonard S. Kisslinger, Carnegie-Mellon Univ. William G. Marterer, Louisiana State Univ. Rex R. Kiziah, Univ. of Texas Xavier K. Maruyama, Nat. Bureau of Standards Jf.mes N. Knudson, Arizona State Univ. Akira Masaike, KEK Dale S. Koetke, Valparaiso Univ. Lynn Massagli, Univ. of New Mexico Donald D. Koetke, Valparaiso Univ. Terrence S. Mathis, UNM Cancer Center Donald K. Kohl, Consultant, New Mexico Howard S. Matis, Lawrence Berkeley Lab. Robert S. Kowalczyk, Argonne June L. Matthews, MIT Daniel A. Krakauer, Univ. of Maryland Bjorn E. Matthias, Yale Univ. Jack J. Kraushaar, Univ. of Colorado Bill W. Mayes, Univ. of Houston Alan D. Krisch, Univ. of Michigan Robert E. McAdams, Utah State Univ. Jeffrey W. Kruk, Rice Univ. James E. McDonough, Temple Univ. Yunan Kuang, Yale Univ. John A. McGill, Rutgers Univ. Dieter Kurath, Argonne Carl McHargue, Oak Ridge Peter H. Kutt, Univ. of Pennsylvania Kok-Heong McNaughton, Univ. of Texas Gary Kyle, SIN William J. Metcalf, Louisiana State Univ. Robert A. Lamb, Univ. of Surrey Zoran Milanovic, UCLA K. Dean Larson, Univ. of New Mexico Daniel W. Miller, Indiana Univ. Bryan E. Laubscher, Univ. of New Mexico Cas Milner, Univ. of Texas Charles M. Laymon, Univ. of Pennsylvania Ralph C. Minehart, Univ. of Virginia Christopher P. Leavitt, Univ. of New Mexico Chandrashekhar Mishra, Univ. of South Carolina VVen-Piao Lee, TRIUMF Joseph H. Mitchell, Univ. of Colorado Frieder Lenz, SIN Joseph W. Mitchell, Ohio State Univ. Kevin T. Lesko, Argonne Keith E. Mitchell, Abilene Christian Univ. Samuel M. Levenson, Northwestern Univ. Murray Moinester, Tel-Aviv Univ. Matthew S. Licholai, U.S. Naval Academy Alireza Mokhtari, UCLA Jechiel Lichtenstadt, Tel-Aviv Univ. Alfredo Molinari, Univ. of Torino Roger L. Lichti, Texas Tech Univ. C. Fred Moore, Univ. of Texas B. Joseph Lieb, George Mason Univ. Shaul Mordechai, Univ. ofTexas/Univ. of Pennsylvania David A. Lind, Univ. of Colorado Sanjoy Mukhopadhyay, Northwestern Univ. V. Gordon Lind, Utah State Univ. Gordon S. Mutchler, Rice Univ. Richard A. Lindgren, Univ. jf Massachusetts Ramesan Nair, Florida State Univ. Alan G. Ling, UCLA Takemi Nakagawa, Tohoku Univ. 256 PROGRESS ATLAMPF—1984

Sirish K. Nanda, Univ. of Minnesota/Rutgers Univ. Raymond F. Rodebaugh, Univ. of Texas Subrata Nath, Texas A&M Univ. George P. Rodriguez, Georgia Inst. of Tech. Robert A. Nauraann, Princeton Univ. Sayed H. Rokni, Utah State Univ. B. M. K. Nefkens, UCLA Thomas A. Romanowski, Ohio State Univ. Charles R. Newsom, UCLA Philip G. Roos, Univ. of Man-land Benwen Ni, Yale Univ. Serge L. Rudaz, Rice Univ. Michael Nicholas, Univ. of Mississippi Charles J. Rush, Ohio State Univ. Lee C. Northcliffe, Texas A&M Univ. Michael E. Sadler, Abilene Christian Univ. David S. Oakley, Univ. of Texas David P. Saunders, Univ. of Texas Yuji Ohashi, UCLA Royce O. Sayer, Oak Ridge Hajime Ohnutna, Tokyo Inst. of Tech. H. Reiner Schaefer, Yale Univ. Pedro OUlataguerre, UCLA John P. Schiffer, Argonne Shoji Okumi, Nagoya Univ. Alan Scott, Univ. of Georgia Glenil A. Olah, Abilene Christian Univ. Susan Seestrom-Morris, Univ. of Minnesota Jean M. Oostens, Illinois lnst. of Tech. Colin J. Seftor, George Washington Univ. Herbert Orth, Yale Univ./Univ. ul'Mainz Ralph E. Segel, Northwestern Univ. O. Harry Otteson, Utah State Univ. Peter A. Seidl, Univ. ofTexas Paul V. Pancella, Rice Univ. Kamal K. Seth, Northwestern Univ. Brett L. Parker, Univ. of Massachusetts Madhu Sethi, Northwestern Univ. Gianni Pauletta, UCLA/l iniv. of Texas Tomikazu Shima, Argonne Charles F. Perdrisat, Coll. of William & Mary Hajime Shimizu, Argonne Roy J. Peterson, Univ. of Colorado Frank T. Shively, Lawrence Berkeley Lab. Fred L. Petrovich, Florida State Univ. Rickey L. Shypit, Univ. of Surrey LongD. Pham, MIT Edward R. Siciliano, Univ. of Georgia Leo E. Piilonen, Princeton Univ. Margaret L. Silbar, Consultant, New Mexico Chandra Pillai, Oregon State Univ. Daniel M. Slate, Univ. of New Mexico Ginger A. Pinnick, Arizona State Univ. Elton S. Smith, Ohio State Univ. Lawrence S. Pinsky, Univ of Houston Kaleen J. Smith, Abilene Christian Univ. Hans S. Plendl, Florida State Univ. L. Cole Smith, Univ. of Virginia Barry M. Preedom, Univ. of South Carolina Winthrop W. Smith, Univ. of Connecticut Dean L. Preston, Univ. of New Hampshire Daniel I. Sober, Catholic Univ. of America Vina A. Punjabi, Coll. of William & Mary Rayappu Soundranayagam, Northwestern Univ. Arthur M. Rask, Argonne Franz Sperisen, UCLA Mohini W. Rawool, New Mexico State Univ. Harold M. Spinka, Argonne Glen A. Rebka, Univ. of Wyoming Keshav N. Srivastava, Virginia State Univ. Edward F. Redish, I 'niv. of Maryland Robert VV. Stanek, Argonne Robert P. Redwine, MIT Rolf M. Steffen, Purdue Univ. James J. Reidy, Univ. of Mississippi George S. F. Stephans, Argonne Horst Dieter Renipp, Max-Planck Inst. William B. Stevenson, Temple Univ. Louis P. Remsberg, Brookhavcn James E. Stewart, Univ. of New Mexico James H. Richardson, Consultant. New Mexico David P. Stickland, Princeton Univ. Peter J. Riley, Univ. of Texas Carey E. Stronach, Virginia State Univ. G. Roy Rin jo. Argonne Takenori Suzuki, Hachinohe Inst. of Tech. Haris Riris, Univ. of Virginia L. Wayne Swenson, Oregon State Univ. Robert A. Ristinen, Univ. of Colorado Miki S. Takeda, Northwestern Univ. Barry G. Ritchie, Univ. of Maryland Richard L. Talaga, Univ. of Maryland Michael \V. Ritter, Stanford Univ./Yalc Univ. Yasutoshi Tanaka, Purdue Univ. Warren M. Roane, Abilene Christian Univ. Peter C. Tandy, Kent State Univ. Donald A. Roberts, Unix, of Wyoming Robert L. Tanner, Consultant. New Mexico LAMPF VISITORS 257/^.$"

Morton F. Taragin, George Washington Univ. Gary S. Weston, UCLA Raphael M. Thaler, Case Western Reserve Univ. C, Steven Whisnant, Univ. of South Carolina Alan K. Thompson, Rice Univ. R. Roy Whitney, Univ. of Virginia T.Neil Thompson, UC, Irvine Charles A. Whitten, UCLA Mark Timko, Ohio State Univ. Bryan H. Wildenthal, Drexel Univ. Benjamin Titov, uc, Irvine Keniner B, Wilson, Consultant, New Mexico John W, Tobin, New Mexico State Univ. Robert R. Wilson, Columbia Univ. Christoph Tschalar, SIN Steven L. Wilson, Stanford Univ. Vatche B. Tutundjian, Arizona State Univ. James D. Wing, Consultant. New Mexico John L. Ullmann, Univ. of Colorado David R. Wolf, Virginia Poly. Inst. & Slate Univ. David G. Underwood, Argonnc Stephen A. Wood, Tel-Aviv Univ. Albert Van Der Kogel, UNM Cancer Center Kim A. Woodle, Yale Univ. Gordon J. YanDalen, UC, Riverside James Worthington, Consultant. Washington Kantran Vaziri, Utah State Univ. Dennis H. Wright, Virginia Poly. Inst. & Slate Univ. Bruce J. Ver West, Arco Oil & Gas Co. S. Courtenay Wright, Univ. of Chicago V, V. Verbinski, Sci. Applications. Inc.. California Shen-Wu Xu, Univ. of Texas Victor E. Viola, Indiana Univ. Ichiro Vliniiiuchi, Nihon Univ. Wolfram Von VVitsch, Rice Univ. Ming-Jen Yang, Univ. of Chicago Roberta J. Wade, Univ. of New Mexico Akihiko Yokosawa, Argonne Robert G. Wagner, Argonnc Jin-Nan Yu, Inst. of Atomic Energy. PRC John D. Walecka, Stanford Univ. Vincent Yuan, Univ. of Illinois Robert L. Walker, Consultant. New Mexico Larry Zamick, Rutgers Univ. Stephen J. Wallace, Univ. of Man-land Benjamin Zeidman, Argonnc Russell E. Walstedt, Bell Laboratories. Murray Hill Qiuan Zhu, Rice Univ. Angel T. M. Wang, UCLA Ren-Yuan Zhu, Caltech Keh-Chung Wang, UC. Irvine John J. Zimerle, Ohio State Univ. Zhi-Fu Wang, Inst. of Atomic Energy. PRC Hans J. Ziock, UCLA Cary M. Warren, UC. Riverside Klaus O. H. Ziock, Univ. of Virginia John W. Watson, Kent State Univ. Robert Ziock, UCLA Monroe S. Wechsler, Iowa State Univ. John D. Zumbro, Univ. of Pennsylvania/Princeton Univ. Charles A. Wert, Univ. of Illinois INFORMATION FOR CONTRIBUTORS

Progress at LAMPF is the progress report of MP Division of Los Alamos National Laboratory. In addition it includes brief reports on research done at LA.MPF by researchers from other institutions and Los Alamos National Laboratory divisions. Progress at UMPFis published annually on April 1. This sc! ires that manuscripts be received by January 1. Published material is edited to the standards of the Style Ma, uie American Institute of Physics. Papers are not refereed, hence presentation in this report does not constitute professional publication of the material nor does it preempt publication in other journals. Readers should recognize that results reported in Progress at UMPFare sometimes preliminary or tentative and that authors should therefore be consulted in the event that these results are cited. Contributors can expedite the publication process by giving special care to the following specifics:

~~1. When possible, furnish computer files together with hardcopy of paper. Progress at LAMPF can accept files from computers, stand-alone word processors, and personal computers.~~

~~2. Drawings and figures submitted should be of quality suitable for direct reproduction after reduction to single-column width, 8? mm (3-1/4 in.).~~

~~3. Figure captions and table headings must be furnished.~~

4. References must be complete and accurate. If a reference cites a paper submitted for publication, the title of the paper must be given. For legal reasons the term private communication cannot be used in Progress at LAMPF. Credit for unpublished information may be given in footnotes, provided the name, organization, and date are cited.

~~5. Abbreviations and acronyms should be avoided if possible (in figures and tables as well as text), and when used must be defined.~~

~~6. All numerical data should be given in SI units.~~

~~7. Authors are reminded that it helps the reader to have an introduction, which states the purpose(s) of ihe experiment, before presentation of the data.~~

Research reports should be brief but complete. A list of recent publications relating to the experiment, for separate tabulation in this report, is much appreciated. Contributors are encouraged to include as authors all participants in experiments so that they may receive credit for authorship and participation. Questions and suggestions should be directed to John C. Allred, Los Alamos National Labora- tory, MS H850, Los Alamos, NM 87545.

~~tj. U.S. GOVERNMENT PRINTING 0FFICE:1985-567-034 I JKXJ65 259~~