Progress at LAMPF

268 Pages·1991·16.449 MB·English

by  Los Alamos National Laboratory

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Pro,tlressatLAMPF
January-Oecember 1989
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PROGRESASTLAMPF
Foreword
FOREWORD
We should ali take a great deal of pride in how ,,,.'ellthe Los Alamos Meson
Physics Facility (LAMPF) operated during 1989. A new mode of operation was
incorporated during the year,multiplexed polarized and unpolarized beam to
the external proton beam line (Line X).These two beams, together with the high-
and low-intensity H- beam for the Proton Storage Ring (PSR) and Weapons
Neutron Research (WNR), as well as the high-intensity H+ beam to Line A,
had LAMPF simultaneously running five separate types of beams to a variety
of experimental areas. Congratulations are in order to the accelerator operating
staff!
The optically pumped polarized ion source (OPPIS) was commissioned in
1989and should be incorporated into routine operation in 1990 at 60% polariza-
tion and at least 15/JA peak current.
Because of an effective effort throughout MP Division, the PSR has greatly
increased both its reliability and peak current. The LAMPF/PSR combination
delivered a time-average current of 60 irA at 20 Hz with an overall system re-
liability of 75%. As the spill time of a PSR pulse is 0.25/ts, the instantaneous
current is 12amperes, which corresponds to an instantaneous power of 10gi-
gawatts. While the bulk of the neutrons generated by the PSR protons at the
Manuel Lujan, Jr. Neutron Scattering Center (LANSCE) is used for research in
materials science, a group of nuclear physicists from Triangle Universities Nu-
clear Laboratory (TUNL), Los Alamos, Tri-University Meson Facility (TRIUMF),
and Delft have carried out a set of pioneering experiments studying parity vi-
olation using thermal-epithermal neutrons. The resulting data can be readily
analyzed using well-established concepts from the statistical theory of spectra.
This approach promises to be a very important development in nuclear physics.
In the area of continuing developments in experimental capability, the use
of polarized nuclear targets has become somewhat routine as two definitive mea.
surements were carried out involving charge exchange and elastic scattering of
pions from polarizc_ 1aC.The results from these new measurements are presently
being analyzed. There are plans formore experiments with polarized 1aCand _Li
at the Energetic Pion Channel and Spectrometer (,EPICS).The Medium-Resolution
Spectrometer (MRS) was commissioned near the end of the !ast cycle and imme-
diately achieved a resolution of 1.2MeV at800 MeV,very near the design goal of
1.0MeV. lt was also successfully operated in the (n,p) mode in the neutron beam
line. Thus, the Nucleon Physics Laboratory (NPL) is ready to go with Neutron
Time-of-Flight (NTOF), MRS, and OPPIS. We can look forward to a great in-
crease in the knowledge of the spin and isospin dependence ofnuclear structure
and reactions from nucleon-nucleus _attering experiments over the next five or
so years.
Looking to the future, we plan to put into operation in 1990a superconduct-
; ing rf cavity termed the SCRUNCHER on the Low-Energy Pion (LEP) beam line.
: The cavity is referred to as a SCRUNCHER because it compresses longitudinal
: phase space of the pion beam in either energy or time to satisfy the require-
ments of a given experiment. For example, at a fixed momentum resolution, by
vi
PROGRESS AT LAMPF
Foreword
compressing the beam in energy, it can increase the pion flux delivered to an
experiment by a factor of S.
In conjunction with LAMPF users and other leaders in the nuclear physics
community, we are undertaking an examination of future direction for LAMPF
in light of the most recent (1989) Nuclear Science Advisory Committee (NSAC)
Long-Range Plan for U.S. nuclear physics. Although it appears that a large-scale
upgrade to much higher energy at LAMPF is not possible for several years, there
are a variety of enhancements that offer exciting new physics potential. Among
those that draw a great deal of support from the LAMPF -user community is
the development of a bright pion be.am at ,-,10'_pions/second at 1 GeV to al-
low high-resolution studies in hypernucleus physics via the _-,K reaction. There
is also strong support among users to further develop the intense, low-duty
factor beams from the PSR for muon and neutrino physics. This would be a
truly unique source that would alleviate the present requirement atthe Line A
beam stop source for extensive and expensive active and passive shielding of
cosmic rays. Such a developmen_ will make neutrino physics appreciably eas-
ier and able to address a larger class of problems. There is also a community
of nuclear physicists who find the possibility of doing world-class fundamental
experiments with cold neutrons in the US. an exciting possibility. We are inves-
tigating the degree to which LAMPF/PSR/LANSCE can meet this requirement.
lt also emerged at the NSAC 1989 Long-Range Planning (LRP) meeting that a
large segment of the community was interested in carrying out research with
beams of exotic short-lived nuclei such as SHe, _1Li, etc. The most efficient way
to produce these nuclei in sufficient quantity is by the use of a0.6-1 GeV proton
beam to initiate spallation reactions on suitable heavy targets. The shor'-lived
nuclei are then extracted from the target and ionized for acceleration in an ap-
propriate post accelerator. LAMPF has in place the necessary proton beam and
infrastructure to b,_a natural site for such a facility We are also actively looking
into this possibility via a series of workshops and development plans.
Thus, at the present moment, we see many possibilities forthe future. How-
ever, they all require the necessary support to keep LAMPF a vital laboratory
at the forefront of nuclear science. We believe that the Department of Energy
wants us to continue in that role and expect that they will provide the resources
required to do the job.
Gerald T. Garvey
Director of LAMPF
vii
PROGRESSATLAMPF
Contents
CONTENTS ExperimentaAlreas...................................................... xii
LAMPFUsersGroup..................................................... 1
Twenty-Third Annual Meeting ........................................... 3
Committees ................................................................ 4
Workshops ................................................................ 6
, Visitors Center ........................................................... 8
Research................................................................... 11
Nuclear and Particle Physics ................................... ........ 13
EXPERIMENT791-- BNLAGS
A Study of Very Rare I__.Decays ................................... 13
EXPERIMENT960....BR
Measurement of AaT and Ac,/, in Free Neutron-Proton
Scattering Between 300 and SO0MeV ............................. 16
EXPERIMENT1035-- BR
Three-Spin Measurements in pp _ pp at 730 MeV ................... 19
EXPERIMENT1161....EPICS
Nuclear Structure Effects in DCX to the DIAS for 7_,7_,_°,a'2-Se....... 23
EXPERIMENTS581AND704-- Fermilab
Polarized Proton and Antiproton Experiments at Fermilab .......... 26
EXPERIMENT772.....Fermilab
Study of the Nuclear Antiquark Sea with the Drell-Yan
Process at 800 GeV ................................................ 30
EXPERIMENT1075....HIRAB
Interaction of Relativistic H- Ions with Matter ...................... 37
EXPERIMENT1121......HIRAB
High Excitations and Double Escape in the Negative
Hydrogen Ion ........................ ...... ....................... 41
EXPERIMENT1127--HIRAB
Multiphoton Detachment of Electrons from the H- ._on............. 46
EXPERIMENT811 ......LEP
Study of Unnatural Parity States in Nuclei Using
Low-Energy Pions ................................................ 49
viii
PROGRESS AT LAMPF
Contents
EXPERIMEN9T48-- LEP
The Role of Quasi-Deuterons in Pion Absorption on aLi............. 57
EXPERIMEN9T75-- LEP
Pion-Nucleus Single Charge Exchange at Threshold Energies ........ 59
EXPERIMEN1T023-- LEP
Analyzing Power Measurements for the (Tr+,7r°) Reaction on a
Polarized 13CTarget .............................................. 61
EXPERIMEN1T025---LEP
Pion Elastic Scattering from Polarized 1aC........................... 63
EXPERIMEN1T085--- LEP
Pion Absorption on Deuterium Below 20MeV ....................... 66
EXPERIMEN1T098-- LEP/Clamshell
Energy Dependence of Low-Energy Pion Double Charge
Exchange ......................................................... 67
EXPERIMEN2T25-- Neutrino-A
Measurement of the Exclusive Cross Section 12C(ue,e-)l"N(g.s.) .... 71
EXPERIMEN2T25-- Neutrino-A ,,
A Study of Neutrino-Electron Elastic Scattering ..................... 76
EXPERIMEN6T45-- Neutrino-A
A Search for Neutrino Oscillations .................................. 81
EXPERIMEN1T173--Neutrino-A
Search for Neutrino Oscillations with High Sensitivity in
the Appearance Channels u, --, u,_and Ft, --,/;e ................... 82
EXPERIMEN1T123.-- NTOF
The 160(p,n)16FReaction at 500 MeV ............................... 85
EXPERIMEN7T50....P:_-East
Reaction Mechanism of Inclusive Pion Double Cha-ge
Exchange in 4He .................................................. 90
EXPERIMEN1T103-- Pa-East
Inelastic Pion Scattering on 1aOAbove the A Resonance ............ 96
ix
PROGRESS AT LAMPF
Contents
EXPERIMEN1T107-- P3-East
Studies of Pion Double Charge Exchange Scattering at
Energies Above the A Resonance ................................ 100
EXPERIMENiT153- Pa-East
Quasifree Pion Charge Exchange at 500MeV....................... 104
EXPERIMEN1T015--PSR
A Large Cerenkov Detector for Neutrino Physics ................... 106
EXPERIMEN1T183-- PSR
The Study of Time Reversal and Parity Symmetries Using
Epithermal Neutrons ............................................ 109
EXPERIMEN9T69--SMC
MEGA: Search for the Rare Decay iL+---+e+7... ................... 111
Astrophysics .117
CYGNUS Project .... ............................................... 117
Atomic and Molecular Physics ......................................... 119
EXPERIMEN9T63-- SMC
First Direct Measurement of C_-l_Sticking in dt-ttCF ................ 119
EXPERIMEN1T151-- SMC
ExperimentalInvestigation of Muon-Catalyzed Fusion............. 126
Materials Science...................................................... 130
EXPERIMEN1T115
Magnetic Ordering in (YI_,.Pr,,Ba.2Cu:_O7as Evidenced by
Muon Spin Relaxation ........................................... 130
Nuclear Chemisla'y ..................................................... 137
EXPERIMEN1T100-- TOFI
Direct Mass Measurements Using the TOFI Spectrometer:
The Neutron-Rich Isotopes of Chlorine through h'on ............. 137
Radiation Effects ....................................................... 142
EXPERIMEN1T014-- Radiation-EffecFtsacility
Proton, Spallation-Neutron, and Fission Neutron Irradiation
of Copper 142
EXPERIMEN1T139-- BeamStopirradiationFacility
Testing of Radiation Resistance of Read-Out Chips for Use in
_ High-Rate Nuclear and Particle Physics Applications ............ 144
X
PROGRESS AT LAMPF
Contents
EXPERIMENT1165-- SpallationRadiationEffectsFacility
Synergetic Load Effects on the Beam Entry Window of a
High-Power Spallation Neutron Source .......................... 146
Radioisotope Production ................................................ 147
INC-11 Radioisotope Production Activities .......................... 147
Theory ................................................................. 150
Configuration Mixing as a Source of Three-Body Molecular
Formation it. Muon Catalyzed d-I Fusion ......... ............... 150
Neutron Radius Analysis in the Trinucleon System from
Pion Scattering ..................................................... 152
Report of the T-5 Theoretical Group ................................ 172
MP-Division Publications .............................................. 186
FacilityDevelopmen..t............................................... .. 211
OPPIS: The Optically Pumped Polarized Ion Source ................. 212
LAMPF and the Proton Storage Ring (PSR) Control
Systems and Operations .............................................. 215
PSR and WNR Beam Delivery Systems ................................ 217
201-MHz RF System Problems ............................. ............. 221
Computing Directions and Opt:ms for Data Acquisition
and Analysis at LAMPF ... .................................. ........ 223
Cost of the LAMPF Linac Extension ................................... 225
AcceleratorOperation.s.............................................. 227
Milestones 231
......
Appendixe.s............................................................. 239
Appendix A:
Experiments Run in 1989...................................... , .... 240
Appendix B:'
New Proposals During 1989........................................ 243
Appendix C:
L,AMPF Visitors During 1989....................................... 249
InformationforContributors
........................................... 259
xi
PROGRESSATLAMPF
ExperimentAalreas
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HRS HighResolullonSpoclromoler fl.,_ t _ ' __ Dm,..... 1.+4
MRS Medium.l:_esolulionSpectrometer " " "_.,,) U _ ............
TOFI Time.oi.Flight IsochronousSpectrometer ". /",,./-; • r. ....... PolarizedProtonsorH-
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xii