[en] At the University of New Hampshire we have a program of polarizing ³He samples for use as targets in electron scattering experiments, neutron spin filters, and for magnetic resonance imaging. The objective of this poster was to give an introduction to polarized ³He neutron spin filters and to outline the fabrication of spin-exchange polarized ³He neutron spin filters at UNH for two recent measurements at LANSCE

[en] High precision fundamental neutron physics experiments have been proposed for the intense pulsed spallation neutron beams at JSNS, LANSCE, and SNS to test the standard model and search for new physics. Certain systematic effects in some of these experiments have to be controlled at the few ppb level. The NPD Gamma experiment, a search for the small parity-violating γ-ray asymmetry A_Y in polarized cold neutron capture on parahydrogen, is one example. For the NPD Gamma experiment we developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5 cm x 9.5 cm pulsed cold neutron beam with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to rf neutron spin flippers based on adiabatic fast passage. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically polarized ³He neutron spin filters. The efficiency of the spin rotator was measured at LANSCE to be 98.8 ± 0.5% for neutron energies from 3 to 20 meV over the full phase space of the beam. Systematic effects that the rf spin rotator introduces to the NPD Gamma experiment are considered