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The NPDGamma experiment measures the parity-violating (PV) gamma asymmetry from polarized cold neutrons captured on protons at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The (PV) neutron spin asymmetry A γ of photons from polarized cold neutron capture on protons is proportional to the ΔI=1 long range weak meson coupling $h_{\pi }^{1}$ between nucleons in the hadronic weak interaction (HWI). Liquid para-hydrogen production data taking concluded in April 2014 and once the background aluminum asymmetry measurements are complete, the PV asymmetry A γ can be extracted. Preliminary results of the analysis of A γ are presented.

Temperature measurement and control are important in brute force polarization experiments. We discuss the installation and use of3He melting curve thermometers in a crystat used to polarize a TiH2 target. Comparison is made between the melting curve thermometers and the60CoCo nuclear orientation thermometer, which is often used in such experiments. The melting curve thermometers provide increased temperature resolution and sensitivity, and were used in a feedback heating system to control temperature to ±5.5 μK at 16.5 mK. The3He melting curve and the60CoCo temperature scales are found to agree within 2% at 15 mK. The present status of the melting curve scale and the effect of a magnetic field on melting curve thermometry are also discussed.

Measurements of the transverse polarization-transfer coefficient \(\) for the reaction \(\)H\(\)He are reported for outgoing neutron energies of 1.94, 5.21, and 5.81 MeV. This reaction is important both as a source of polarized neutrons for nuclear-physics experiments, and as a test of theoretical descriptions of the nuclear four-body system. Comparison is made to previous measurements, confirming that the \(\)H\(\)He reaction can be used as a polarized neutron source with the polarization known to an accuracy of approximately 5%. Comparison to R-matrix theory suggests that the sign of the \(\) phase-shift parameter is incorrect. Changing the sign of this parameter dramatically improves the agreement between theory and experiment.