Measurements of parity violation in a search for candidate resonances for a test of time-reversal invariance in neutron absorption

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:5591721

Coulter, K P

Parity violation in neutron resonance absorption has been used in a search for candidate resonances for a new class of tests of time reversal invariance. Time reversal non-invariant effects in neutron absorption could be enhanced under the same conditions which lead to enhanced parity violation. This experiment therefore searched for parity violation in p-wave resonances to identify resonances appropriate for such time reversal test. The parity non-conserving cross section asymmetry P = ({sigma}{sub +} {minus} {sigma}{sub {minus}})/({sigma}{sub +} + {sigma}{sub {minus}}) was measured at resonances in four targets: {sup 155}Gd, {sup 165}Ho, {sup 235}U, and {sup 139}La. The experiment used a pulsed epithermal neutron beam and employed, for the first time, a spin-exchange optically-pumped polarized {sup 3}He neutron spin filter. Longitudinally polarized neutrons which passed through the sample were detected with a {sup 6}Li glass scintillator. A non-zero effect was observed at a 3.616 eV resonance in {sup 155}Gd: P = 1.2 {plus minus} 0.4%. Effects consistent with parity conservation were observed at a 5.6 eV resonance in {sup 165}Ho and a 0.290 eV resonance in {sup 235}U: P = 4.6 {plus minus} 4.0% and 0.1 {plus minus} 0.3%, respectively. The previously observed parity violation of P = 8.4 {plus minus} 1.1% at the 0.734 eV resonance in {sup 139}La was used to assist in the measurement of the neutron polarization. In addition to reporting the results of this experiment, this dissertation discusses the enhancement mechanisms responsible for the large parity violating effects. It also describes the method of spin exchange optical pumping used to produce dense, gaseous targets of polarized {sup 3}He and such a target's use as a neutron spin filter. A review of the proposed time reversal tests, including the experimental configurations, the suggested enhancements, and the consequences of the measurements included in this work is given.

• Research Organization: Princeton Univ., NJ (United States)
• OSTI ID: 5591721
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
GADOLINIUM 155 TARGET
NEUTRON REACTIONS
HOLMIUM 165 TARGET
LANTHANUM 139 TARGET
P INVARIANCE
NEUTRONS
RESONANCE ABSORPTION
T INVARIANCE
TESTING
URANIUM 235 TARGET
CROSS SECTIONS
P WAVES
RESONANCE
ABSORPTION
BARYON REACTIONS
BARYONS
ELEMENTARY PARTICLES
FERMIONS
HADRON REACTIONS
HADRONS
INVARIANCE PRINCIPLES
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEONS
PARTIAL WAVES
TARGETS
663430* - Nucleon-Induced Reactions & Scattering- (1992-)
663560 - Nuclear Mass Ranges- A=90-149- (1992-)
663570 - Nuclear Mass Ranges- A=150-189- (1992-)
663590 - Nuclear Mass Ranges- A=220 & Above- (1992-)
662120 - General Theory of Particles & Fields- Symmetry
Conservation Laws
Currents & Their Properties- (1992-)