A liquid helium target system was designed and built to perform a precisionmeasurement of the parity-violating neutron spin rotation in helium due to thenucleon-nucleon weak interaction. The measurement employed a beam of low energyneutrons that passed through a crossed neutron polarizer--analyzer pair withthe liquid helium target system located between them. Changes between thetarget states generated differences in the beam transmission through thepolarizer--analyzer pair. The amount of parity-violating spin rotation wasdetermined from the measured beam transmission asymmetries. The expectedparity-violating spin rotation of order $10^{-6}$ rad placed severe constraintson the target design. In particular, isolation of the parity-odd component ofthe spin rotation from a much larger background rotation caused by magneticfields required that a nonmagnetic cryostat and target system be supportedinside the magnetic shielding, while allowing nonmagnetic motion of liquidhelium between separated target chambers. This paper provides a detaileddescription of the design, function, and performance of the liquid heliumtarget system.
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