Decoupler development at J-PARC neutron source facility

Oi, Motoki ; Harada, Masahide   ; Teshigawara, Makoto   

J-PARC neutron source facility is 1MW pulsed spallation neutron source in Japan. There are three liquid hydrogen moderators, one is for high intensity, the others are for short pulse neutron beam. In order to make short pulsed neutron beam, neutron absorber called decoupler is attached around the moderators. Characteristics of the decoupler is described by the neutron cut-off energy (Ed). In J-PARC, Ed of 1eV is realized by the Ag-In-Cd decoupler at the 1MW spallation neutron source. Due to the radiation damage and burn-up of the decoupler material, we have to replace these moderator and reflector assembly in near future. For the second moderator and reflector assembly, we developed a Au-In-Cd alloy as a low activation material. Ed of Au-In-Cd alloy is 1eV. Activation of the Au-In-Cd is much lower than that of Ag alloy. We manufactured the Au-In-Cd alloy and processed the alloy by ourselves. Finally, it was installed into the moderator and reflector assembly.