Development of the Au-In-Cd alloy for low-activation thermal neutron absorber for spallation neutron source

Oi, Motoki ; Teshigawara, Makoto   ; Harada, Masahide   ; Kasugai, Yoshimi  

The Japan Spallation Neutron Source (JSNS) is a 1 MW pulsed neutron source of the Japan Proton Accelerator Research Complex (J-PARC). In order to produce the neutron beams with narrow width and fast decay, thermal neutron absorber (decoupler) is adopted to the moderator. For the first moderator, we developed a Ag-In-Cd decoupler. However, Ag-In-Cd decoupler also has a disadvantage of residual radioactivity, such as 108 mAg. The authors have focused on the development of a low activated decoupler for the second moderator. A combination of gold(Au), indium(In) and cadmium(Cd) was selected as the decoupler material. From the viewpoint of neutronics, we found that the Au-In-Cd decoupler provided three orders of magnitude lower radioactivity than the Ag-In-Cd one without sacrificing the neutronic performance. However, there were almost no data about Au-In-Cd alloy production. Purpose of this study is development of the Au-In-Cd alloy.