Development and application of a He neutron spin filter at J-PARC

Okudaira, Takuya; Oku, Takayuki   ; Ino, Takashi*; Hayashida, Hirotoshi*; Kira, Hiroshi*; Sakai, Kenji ; Hiroi, Kosuke  ; Takahashi, Shingo*; Aizawa, Kazuya  ; Endo, Hitoshi*; Endo, Shunsuke   ; Hino, Masahiro*; Hirota, Katsuya*; Honda, Takashi*; Ikeda, Kazutaka*; Kakurai, Kazuhisa*; Kambara, Wataru*; Kitaguchi, Masaaki*; Oda, Tatsuro*; Oshita, Hidetoshi*; Otomo, Toshiya*; Shimizu, Hirohiko*; Shinohara, Takenao   ; Suzuki, Junichi*; Yamamoto, Tomoki*

We are developing a neutron polarizer with polarized He gas, referred to as a 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 He gas-filling station was constructed at J-PARC, and several 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 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 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 He spin filter was conducted, and there have been several more since then. The development and utilization of He spin filters at MLF of J-PARC are reported.