Status of an Apparatus to Measure the Parity-odd Neutron Spin Rotation in $^{4}$He

The weak interaction between nucleons is sensitive to quark-quark correlations in the nucleon and provides an opportunity to test the Standard Model in the low energy strongly interacting limit. Recent advances in theory [1] [2] coupled to the measurement of the weak pion exchange component of the NN weak interaction imply predictions for parity-odd neutron spin rotation in $^{4}$He of $d\phi/dz = 9 \pm 3 \times 10^{-7}$ rad/m. The previous measurement of $d\phi/dz = [+2.1 \pm 8.3(stat.) \pm 2.9(sys.)] \times 10^{-7}$ rad/m [3] lies just outside the theoretical value. A new non-magnetic pump and target system and other upgrades to the NSR apparatus can enable an experimental sensitivity approaching $< [\pm 1.0(stat.) \pm 1.0(sys.)] \times 10^{-7}$ rad/m [4] on the NG-C beam at NIST. This would constitute the first Standard Model test of strangeness-conserving nonleptonic weak interactions. The status of the NSR apparatus will be presented. \\ \\{[1]} S. Gardner, W. C. Haxton, and B. R. Holstein, Ann. Rev. Nucl. Part. Sci. \textbf{67}, 69, 024001, (2017).\\{[2]} R. Lazauskas and Y.-H Song, Phys. Rev. C {\bf 99}, 054002 (2019).\\{[3]} H. E. Swanson, {\it et al.}, Accepted to Phys. Rev. C., (2019).\\{[4]} W. M. Snow, {\it et al.}, Rev. Sci. Inst. \textbf{94}, 055101, (2015).