Test of a continuously polarized 3He neutron spin filter with NMR-based polarization inversion on a single-crystal diffractometer

Abstract Spin filters based on the large spin dependence of the neutron absorption cross-section by 3 He are currently being applied in neutron scattering. We report here the construction and test of a 3 He neutron spin filter that incorporates (1) in situ continuous optical pumping to maximize the time-averaged polarization and maintain a stable 3 He polarization during experiments, and (2) low-loss adiabatic-fast-passage inversion of the 3 He polarization to eliminate the need for a neutron spin flipper. The device was successfully tested at the single-crystal diffractometer at the Intense-Pulsed Neutron Source, Argonne National Laboratory. This device can be used in measurements of static magnetic-materials as well as magnetic-relaxation phenomena with long relaxation times.