A large area polarized 3He neutron spin filter

Abstract A large area polarized 3 He neutron spin filter has been developed and tested in long-term operation. The polarizer cells have area 50 cm 2 and larger allowing access to a large area neutron beam. Polarization of 3 He up to 57 ± 1 % was measured by monitoring the neutron transmission through the 3 He. The polarization was maintained over the course of several weeks, but the maximum attainable polarization declined over the course of a year-long run as the cell degraded, possibly due to long-term exposure to the neutron beam at high temperatures. The resulting neutron polarization and transmission are velocity dependent and are optimized for 5 A. Cell construction, polarizer design, performance, and polarimetry are described in this paper.