A large area polarized 3He neutron spin filter

A large area polarized 3He neutron spin filter has been developed and tested in long-term operation. The polarizer cells have area 50cm2 and larger allowing access to a large area neutron beam. Polarization of 3He up to 57±1% was measured by monitoring the neutron transmission through the 3He. 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 5Å. Cell construction, polarizer design, performance, and polarimetry are described in this paper.