Development of the Hg target in the J-PARC neutron source

A liquid mercury target system for the MW-class pulsed spallation neutron source is installed at the Materials and Life science experimental Facility (MLF) of J-PARC. MW-class proton bombardment of the mercury brings about intensive pressure waves that impact on mercury target vessel repeatedly at 25 Hz and can remarkably degrade the structural integrity and the lifetime of the vessel. In order to realize the high-power mercury target, R and D on the pressure wave mitigation technology is carried out experimentally and theoretically. One of the promising methods to mitigate the pressure waves is to inject microbubbles into the mercury. The microbubbles exhibit three effects for the mitigation: absorption, attenuation and suppression. An in-situ diagnostic system for measuring the dynamic responses induced by the pressure waves is installed in the Japan Spallation Neutron Source (JSNS). In this paper, we briefly describe the strategy to realize the high-power mercury target in the JSNS.