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.

9 pages, 15 figures