Commissioning of the cryogenic hydrogen system in J-PARC; First cool-down operation with helium

Tatsumoto, Hideki; Aso, Tomokazu ; Kato, Takashi; Otsu, Kiichi; Hasegawa, Shoichi   ; Maekawa, Fujio  ; Futakawa, Masatoshi  

In J-PARC, an intense spallation neutron source (JSNS) driven by a 1-MW proton beam has been constructed. A cryogenic hydrogen system, which provides supercritical hydrogen at the temperature of around 20 K and the pressure of 1.5 MPa to the moderators and absorbs nuclear heating in the moderators, has been completed in November 2007 and the commissioning has been started. As a first step, the primary cryogenic operations were conducted by using helium, instead of hydrogen. We confirmed the system soundness at operation temperature, and established operation method of the cool-down process. The cryogenic tests have been successfully completed without problems.