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STUDIES OF NUCLEAR STRUCTURE USING -
NEUTRONS AND CHARGED PARTICLES
Final Progress Report e~
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WERNER TORNOW
Triangle Universities Nuclear-Laboratory
Duke University
BOX 90308
Durham, North Carolina 27708-0308
1 September 1998
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PREPARED FOR THE U. S. DEPARTMENT OF ENERGY
UNDER GRANT NUMBER DE-FGOf-91-ER4t1619
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DISCLAIMER
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.
TUNL XXXVII
PROGRESS REPORT
1 SEPTEMBER 1997-31 AUGUST 1998
TRIANGLE UNIVERSITIES NUCLEAR LABORATORY
DUKE UNIVERSITY
NORTH CAROLINA STATE UNIVERSITY
UNIVERSITY OF NORTH CAROLINA AT CHAPEL HILL
Box 90308, DURHAM, NORTH CAROLINA 27708-0308, USA
Work described in this Progress Report is supported by the United States Department of
Energy, Office of High Energy and Nuclear Physics, under:
Grant No. DE-FG05-91ER40619 (Duke University),
Grant No. DE-FG05-88ER40441 (North Carolina State University), and
Grant No. DE-FG05-88ER40442 (University of North Carolina).
Contents
Introduction ix
Personnel xvii
1 Fundamental Symmetries in the Nucleus 1
l.l Parity-Mixing Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Parity Violation with Polarized Epithermal Neutrons (The TRIPLE
Collaboration) - General . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 Parity Violation with Polarized Epithermal Neutrons (The TRIPLE
Collaboration) - Status of Experiments and Analysis . . . . . . . . . 3
1.1.3 Parity-Violation Tests with Charged Particles . . . . . . . . . . . . . 5
1.2 Quantum Chaos in Nuclei.. . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2.1 Transition-Strength Distributions . . . . . . . . . . . . . . . . . . . . 8
1.2.2 Energy-Level Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 Internucleon Reactions 12
2.1 Neutron-Proton Interaction. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.1 Measurements of Spin-Dependent ii – @’Total Cross Sections . . . . 12
2.1.2 Extraction of the Mixing Angle c1 for n-p Scattering . . . . . . . . . 14
2.1.3 On the 3S1-3D1 Mixing Parameter El Discrepancy Near l% =, 15 MeV 16
2.1.4 Results of the TUNL Neutron-Proton Scattering Length Experiment 18
2.2 Neutron-Neutron Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.1 Measurement of the 1So Neutron-Neutron Scattering Length Using
the 2H(7r- ,wq) Reaction: LAMPI? E1286 . . . . . . . . . . . . . . . 22
2.2.2 Results of the TUNL Neutron-Neutron Scattering Length (a~~)
25
Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.3 Progress of ann Measurement from a Cinematically Incomplete n-d
Breakup Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3 Proton-Deuteron Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.3.1 Proton-Deuteron Elastic Scattering at Ec.m.=432 keV . . . . . . . . 31
...
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TUNL XXXVII 1997-98 Contents
2.3.2 Cross Section and Tensor Analyzing Powers for Proton-Deuteron Scat-
teringat EC,~, =0.667 MeV . . . . . . . . . . . . . . . . . . . . . . 33
2.3.3 The Energy Dependence of the Nucleon-Deuteron Analyzing Power
Puzzle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.3.4 Measurement of the Neutron-Deuteron Analyzing Power at En =
2.0 MeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.3.5 Status of Neutron-Induced Deuteron Breakup Cross-Section Measure-
mentsat 16.0 MeV . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.3.6 Scaling Properties of the Longitudinal and Transverse fi-;Total Cross-
Section Differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3 Dynamics of Very Light Nuclei 44
3.1 Four and Five-Nucleon Reactions . . . . . . . . . . . . . . . . . . . . . . . . 44
3.1.1 Polarization Transfer in the 3H(@’,ii)3He Reaction and the 0- Level in
4He . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.1.2 The 4He(~,dd) Reaction at ET = 150–250 MeV . . . . . . . . . . . . 46
3.1.3 Measurements of the 3He(d,p)4He Reaction at Low Energies . . . . . 49
3.2 Measurements of D States of Very Light Nuclei Using Transfer Reactions . 52
3.2.1 Analyzing Powers of (6fll,d) Reactions and the D State of 6Li . . . . 52
3.3 Radiative-Capture Reactions and Few-Nucleon Systems . . . . . . . . . . . 55
3.3.1 The Study of the 2H(@’,-y)3He and lH(~~)3He Reactions below 80 keV 55
33.2. 2H(~,-y)4He Reaction at.E~= 100 keV . . . . . . . . . . . . . . . . 57
3.3.3 A Study of 3H(j7,~)4He for EPbelow 80 keV . . . . . . . . . . . . . . 58
3.3.4 Angular Distribution Coefficients for ~-Ray Polarizations Produced
in Polarized Capture Reactions . . . . . . . . . . . . . . . . . . . . . 60
4 Nuclear Astrophysics 61
4.1 Radiative-Capture Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.1.1 Cross-Section Studies of the 7Li@,~)8Be Reaction at Low Energies . 61
4.1.2 The Spin-Parity of the 7.478 MeV State of 1°B from the 9Be(fl,~)10B
Reaction at280keV . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.1.3 The llB(@’,~)12C Reaction below 115 keV . . . . . . . . . . . . . . 64
4.1.4 Measurement of the Mean Lifetime for the Astrophysically Important
E. = 6.79 MeV Subthreshold State in 150 Using the Doppler Shift
Attenuation Method . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
4.1.5 Sub-Coulomb a Transfers on 12C . . . . . . . . . . . . . . . . . . . . 68
4.1.6 The 160(~,a)12C Reaction at Stellar Energies . . . . . . . . . . . . . 70
4.1.7 Investigation of 22Ne(p,~)23Na and 23Na(p,~)24Mg Using (3He,d)
Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.1.8 Thermonuclear Reaction Rate of 23Mg(p,~)24Al . . . . . . . . . . . . 74
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Contents TUNL XXXVII 1997-98
4.1.9 Determination of the 24Mg(P,?)25Al Reaction Rate at LOW Stellar
Temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.1.10 Low–Energy Resonance Strengths for Proton Capture on Mg and Al
Nuclei . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.1.11 Explosive Hydrogen Burning of 27Si, 31S, 35Ar and 39Ca in Novae and
X–ray Bursts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.1.12 Study of the 40Ca(3He,t)40Sc Reaction . . . . . . . . . . . . . . . . . 83
4.2 Nucleon Induced Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.2.1 The ‘Be(@’,d)8Be and ‘Be(~,a)6Li Reactions at Low Energies . . . . 85
4.2.2 Search for the 13~=351 keV Resonance in Sscl(’y,a)sjs . . . . . . . . 86
4.3 Radioactive Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.3.1 Nuclear Astrophysics with Radioactive Beams . . . . . . . . . . . . . 87
5 Rare Nuclear Processes 90
5.1 Double-Beta Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.1.1 Measurement of the @/3 Decay Rate of 1°0Mo to the First Excited 0+
State in l°ORu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.1.2 Production ofa1°2Rh Source . . . . . . . . . . . . . . . . . . . . . . 91
5.1.3 Search for the Neutrinoless @#?Decay Rate of 76Ge to the First Excited
State in 76Se . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.1.4 Possible Nonconservation of Electric Charge and Search for a
AQ=21nteraction . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5.2 Exponential Decay Law... . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.2.1 Measurement of Lifetime of 209Bi and Test of the Exponential Decay
Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
6 Sub-Nucleonic Degrees of Freedom 95
6.1 Electromagnetic Form Factors of Nucleons . . . . . . . . ‘. . . . . . . . . . . 95
6.1.1 Measurements of Electromagnetic Form Factors of the Nucleons by
Recoil Polarization: JLAB E93-027, E93-038 and E89-033 . . . . . . 95
7 The Many-Nucleon Problem 99
7.1 Phenomenology of Preequilibrium Nuclear Reactions . . . . . . . . . . . . . 99
7.1.1 Equilibrium Shell Corrections . . . . . . . . . . . . . . . . . . . . . . 99
7.1.2 Proton Total Reaction Cross Sections . . . . . . . . . . . . . . . . . 101
7.1.3 Compensating for ~-Ray Competition with Secondary Protons . . . 102
7.2 Neutron Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...104
7.2.1 Sensitivity Tests on Parameters of the Nucleon-Nucleus Dispersive
Optical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . ...104
7.2.2 Analyzing Power Measurements for 12C(n,n)12C from 2.2 to 8.5 MeV 107
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TUNL XXXVII 1997-98 Contents
7.3 Nuclear Data Evaluation for A=3–20 . . . . . . . . . . . . . . . . . . . . . 110
7.3.1 Data-Evaluation Activities . . . . . . . . . . . . . . . . . . . . . . . 110
7.3.2 ENSDF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
7.3.3 World-Wide Web Services . . . . . . . . . . . . . . . . . . . . . . . . 111
8 Nuclear Instruments and Methods 112
8.1 Tandenl Accelerator Operation.. . . . . . . . . . . . . . . . . . . . . . . . 112
8.1.1 Tandem Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
8.2 KN Accelerator Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
8.2.1 KN Accelerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
8.2.2 Laboratory Improvements and Modifications . . . . . . . . . . . . . 115
8.3 Nuclear Astrophysics Facility . . . . . . . . . . . . . . . . . . . . . . . . . . 116
8.3.1 Construction of the LENA Laboratory . . . . : . . . . . . . . . . . . 116
8.4 Polarized Ion Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
8.4.1 Atomic Beam Polarized Ion Source . . . . . . . . . . . . . . . . . . . 118
8.4.2 Lamb-Shift Polarimeter. . . . . . . . . . . . . . . . . . . . . . . . . 118
8.4.3 New Plasma Ionizer.. . . . . . . . . . . . . . . . . . . . . . . . . . 120
8.4.4 Proposed Studies of Light Nuclei with Increased Polarized Beam In-
densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
8.5 Polarimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
8.5.1 Calibration of a 4He(@’,p) Proton Polarimeter . . . . . . . . . . . . . 125
8.5.2 A Proton Polarimeter for Polarization-Transfer Studies . . . . . . . 126
8.5.3 Hall B Moller Polarimeter at JLAB . . . . . . . . . . . . . . . . . . 128
8.6 Polarized Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
8.6.1 Calibrating Target Polarization in a Polarized Neutron - Polarized
Proton Transmission Experiment . . . . . . . . . . . . . . . . . . . . 130
8.6.2 Construction and Operation of a Dynamically Polarized Deuterium
Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
8.7 Gas-Jet Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
8.7.1 Progress Towards an Operational Gas-Jet Target . . . . . . . . . . . 134
8.8 HIGSFacility atthe DFELL . . . . . . . . . . . . . . . . . . . . . . . . . . 135
8.8.1 Preliminary Plans for a Frozen Spin Deuteron Target at the HIGS
Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
8.8.2 Pair Spectrometer for the HIGS Facility at the DFELL . . . . . . . 135
8.9 KamLAND Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.9.1 The Vetoof KamLAND . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.10 Detector Developments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
8.10.1 Analog Fiber-Optics Pulse Transmission Circuitry . . . . . . . . . . 139
8.10.2 Digital Triggers for Low Count Rates . . . . . . . . . . . . . . . . . 1.40
8.11 Data-Acquisition Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
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Contents TUNL XXXVII 1997-98
8.11.1 New Data-Analysis and Data-Acquisition Systems for TUNL . . . . 141
Appendices 144
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