Spallation neutron source at J-PARC and its cryogenic hydrogen system

Kato, Takashi; Aso, Tomokazu ; Tatsumoto, Hideki; Hasegawa, Shoichi   ; Otsu, Kiichi

The JAEA and the KEK are collaborating in the construction of the Japan Proton Accelerator Research Complex (J-PARC). The J-PARC has four science experimental facilities, a materials and life science experimental facility, a nuclear and particle experimental facility, a neutrino experimental facility, and a nuclear transmutation facility (planned for the future). At the materials and life science experimental facility, a spallation neutron source has been constructed to provide experiment users with neutron beams that have the world's highest pulse intensity. Neutrons produced using spallation reaction should possess a high energy of MeV order, but neutrons used for experiments should have energy of a low meV order. Therefore, an effective material that is capable of moderating neutron energy is required. That material is supercritical hydrogen; and the spallation neutron source should therefore be equipped with a cryogenic hydrogen system that provides supercritical hydrogen to the neutron energy moderating system. This paper discusses the spallation neutron source and the cryogenic hydrogen system.