Development and application of a $^3$He Neutron Spin Filter at J-PARC

Abstract

We are developing a neutron polarizer with polarized 3 He gas, referred to as a 3 He spin filter, based on the Spin Exchange Optical Pumping (SEOP) for polarized neutron scattering experiments at Materials and Life Science Experimental Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC). A 3 He gas-filling station was constructed at J-PARC, and several 3 He cells with long spin relaxation times have been fabricated using the gas-filling station. A laboratory has been prepared in the MLF beam hall for polarizing 3 He cells, and compact pumping systems with laser powers of 30 W and 110 W, which can be installed onto a neutron beamline, have been developed. A 3 He polarization of 85% was achieved at a neutron beamline by using the pumping system with the 110 W laser. Recently, the first user experiment utilizing the 3 He spin filter was conducted, and there have been several more since then. The development and utilization of 3 He spin filters at MLF of J-PARC are reported.