A liquid helium target system for a measurement of parity violation in neutron spin rotation

作者：Bass C D^*; Bass T D; Heckel B R; Huffer C R; Luo D; Markoff D M; Micherdzinska A M; Snow W M; Swanson H E; Walbridge S C

来源：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment , 2009, 612(1): 69-82.

DOI：10.1016/j.nima.2009.10.055

• Cold neutrons
• Cryogenic targets
• Liquid helium
• Neutron physics
• Nucleon-nucleon weak interaction
• Parity-violation
• Polarized neutrons

A liquid helium target system was designed and built to perform a precision measurement of the parity-violating neutron spin rotation in helium due to the nucleon-nucleon weak interaction The. measurement employed a beam of low energy neutrons that passed through a crossed neutron polarizer-analyzer pair with the liquid helium target system located between them. Changes between the target states generated differences in the beam transmission through the polarizer-analyzer pair. The amount of parity-violating spin rotation was determined from the measured beam transmission asymmetries. The expected parity-violating spin rotation of order 10(-6) rad placed severe constraints on the target design. In particular, isolation of the parity-odd component of the spin rotation from a much larger background rotation caused by magnetic fields required that a nonmagnetic cryostat and target system be supported inside the magnetic shielding, while allowing nonmagnetic motion of liquid helium between separated target chambers. This paper provides a detailed description of the design, function, and performance of the liquid helium target system. Published by Elsevier B.V.

• 出版日期2009-12-21