Neutron target for high-intensity operation at J-PARC MLF

Haga, Katsuhiro  ; Naoe, Takashi   ; Kogawa, Hiroyuki  ; Wakui, Takashi  ; Kinoshita, Hidetaka   ; Harada, Masahide   

In April 2024, the beam power at MLF attained 950 kW for the first time for long term user operation, and the beam power at the 3 GeV rapid cycle synchrotron (RCS) outlet was raised to 1 MW. This accomplishment means that the goal of the stable operation of the neutron source with 1 MW was almost achieved at last, and it's time to go on to the new stage of the neutron source R&D. There are two major challenges for the mercury target in the next stage. One is to attain the long-term operation of a mercury target. The service life of the target vessel is primarily determined by cavitation damage that occurs on the inner surface due to the injection of high-intensity pulsed proton beams. Until now, the vessel has been replaced annually to inspect the extent of the damage. However, based on the damage data obtained during 1 MW high-power operation, it has been determined that the vessel can withstand long-term operation for more than two years. Therefore, a new target vessel, which was replaced in 2024, is scheduled to be used for an extended period through 2027. Furthermore, since there are plans to increase the pulse intensity of the RCS in the future, it will be necessary to develop more effective pitting damage suppression techniques and new target vessels that can withstand even stronger proton beam pulses. In this presentation, the present status of the neutron source of MLF and future operation plans will be shown.