Development of 3He polarized neutron spin filters at KEK

Development of neutron spin filters based on polarized gaseous 3He is underway at KEK. Spin-exchange optical pumping is employed to polarized 3He nuclei. Quartz glass cells and sapphire cells are studied as 3He containers. Spin relaxation times of more than 200 h have been observed for quartz glass cells with 3He pressures of 3 atm. Using a pulsed neutron beam, polarizations of 3He were measured for a quartz glass cell and a sapphire cell with 3He pressures of 3 atm to be 54±2% and 63±1%, respectively.