Updates on the operation of the MLF neutron target at J-PARC and perspectives for future operation

Haga, Katsuhiro  ; Naoe, Takashi   ; Wakui, Takashi  ; Kogawa, Hiroyuki  ; Saruta, Koichi   ; Kinoshita, Hidetaka   ; Teshigawara, Makoto   ; Harada, Masahide   ; Sakai, Kenji 

In April 2023, the pulse intensity of proton beam was raised to the highest record of 950 kW for the first time for long term user operation of Materials and Life Science Experimental Facility (MLF). The pulse intensity corresponds to the beam power at the 3GeV rapid cycle synchrotron (RCS) outlet and is the dominant factor of the pitting damage of the mercury target vessel by pressure waves. This accomplishment means that the goal of the stable operation of the neutron source with 1 MW was almost achieved. Since the proton beam pulses at RCS outlet are shared between MLF and 30GeV main ring (MR), the beam power at MLF becomes smaller than that at RCS outlet. The minimum beam share of MLF is planned to be reduced to 86.2 % in 2028. In order to achieve 1 MW operation at MLF, the pulse intensity needs to be increased to 1.16 MW, and the mercury target should endure the pulse intensity higher than 1 MW. In addition, we must cope with the serious issues of storage space and disposal of the highly radioactivated used target vessels. Now R&D of the mercury target vessel is going on to extend the target operation time and to reduce the volume of the used target vessel. Thus, more effective pitting damage mitigation technology and a new target design which can be disassembled by present remote-handling tools are going to be developed. In this presentation, present status of the neutron source of MLF and future operation plan will be shown.