A modular apparatus for use in high-precision measurements of parity violation in polarized eV neutron transmission`

Abstract

We describe a modular apparatus for use in parity-violation measurements in epithermal neutron-nucleus resonances with high instantaneous neutron fluxes at the Manuel Lujan Jr.\ Neutron Scattering Center at Los Alamos National Laboratory. This apparatus is designed to conduct high-precision measurements of the parity-odd transmission asymmetry of longitudinally polarized neutrons through targets containing nuclei with p-wave neutron-nucleus resonances in the 0.1-10 eV energy regime and to accommodate a future search for time reversal violation in polarized neutron transmission through polarized nuclear targets. The apparatus consists of an adjustable neutron and gamma collimation system, a \(^3\)He-${}^4$He ion chamber neutron flux monitor, two identical cryostats for target cooling, an adiabatic eV-neutron spin flipper, a near-unit efficiency \(^6\)Li-\(^{7}\)Li scintillation detector operated in current mode, a flexible CAEN data acquisition system, and a neutron spin filter based on spin-exchange optical pumping of ${}^3$He gas. We describe the features of the apparatus design devoted to the suppression of systematic errors in parity-odd asymmetry measurements. We describe the configuration of the apparatus used to conduct a precision measurement of parity violation at the 0.7 eV p-wave resonance in ${}^{139}$La which employs two identical ${}^{139}$La targets, one to polarize the beam on the p-wave resonance using the weak interaction and one to analyze the polarization.

arXiv comment43 pages, 23 figures

References in corpus (7)

• Optically Polarized ${}^3$He
• Measurement of the Neutron Lifetime by Counting Trapped Protons in a Cold Neutron Beam
• Angular Distribution of $\gamma$-rays from Neutron-Induced Compound States of ${}^{140}$La
• On the Search for Time Reversal Invariance Violation in Neutron Transmission
• Statistical Theory of Parity Nonconservation in Compound Nuclei
• Time reversal invariance violation in neutron-nucleus scattering
• Measurement of the absolute neutron beam polarization from a supermirror polarizer and the absolute efficiency of a neutron spin rotator for the NPDGamma experiment using a polarized ${}^3$He neutron spin-filter

Cited by in corpus (2)

• Particle Physics at the European Spallation Source
• Strong CP violation in nuclear physics