Current status of the development of the He spin filter in JAEA

Okudaira, Takuya; Oku, Takayuki   ; Sakai, Kenji ; Ino, Takashi*; Hayashida, Hirotoshi*; Hiroi, Kosuke  ; Shinohara, Takenao   ; Kakurai, Kazuhisa*; Aizawa, Kazuya  

He spin filter is a neutron polarization device composed of polarized He gas and alkali metal encapsulated into a special glass cell. Since a neutron absorption cross section of He has very large spin dependence, a polarized neutron beam for a wide energy range can be obtained passing through the polarized He gas. He nuclei are polarized irradiating a circularly polarized laser, which is referred to as Spin Exchange Optical Pumping method. The development of the He spin filter is ongoing in JAEA. Recently a spin flip technique of He using frequency sweep NMR and a measurement system of He polarization using electron paramagnetic resonance were developed. Additionally, a vacuum system to make He spin filter is also constructed.