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arXiv · 0905.0395

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

C. D. Bass·T. D. Bass·B. R. Heckel·C. R. Huffer·D. Luo·D. M. Markoff·A. M. Micherdzinska·W. M. Snow·H. E. Swanson·S. C. Walbridge
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Abstract

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.

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C. D. Bass, T. D. Bass, B. R. Heckel, C. R. Huffer, D. Luo, D. M. Markoff, A. M. Micherdzinska, W. M. Snow, H. E. Swanson, S. C. Walbridge. 2009-05-04. A liquid helium target system for a measurement of parity violation in neutron spin rotation. https://doi.org/10.1016/j.nima.2009.10.055

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