Nuclear heat and cold-thermal neutron intensity dependence on proton beam profile and incident position at the J-PARC spallation neutron source

Harada, Masahide   ; Kogawa, Hiroyuki  ; Naoe, Takashi   ; Wakui, Takashi  ; Haga, Katsuhiro  ; Meigo, Shinichiro   ; Oi, Motoki ; Takada, Hiroshi   

At spallation neutron source in J-PARC, 3 GeV and 1 MW proton beam hits into the mercury target and neutron beam is provided to neutron instruments. Changes of proton beam shape and position affect the structural integrity of the mercury target container and the neutron intensity providing to the neutron instruments. In the study, from the viewpoint of neutronics, changes of nuclear heat and neutron intensity were measured as the shape and the position of the proton beam were changed. The neutron intensity was measured with time-of-flight method using a He-3 counter at the neutron instrument, NOBORU. The nuclear heat was derived from the temperature rise rate of the thermocouple installed in the target container. The neutron intensity and nuclear heat were measured in each case of the proton beam condition. As a result of a comparison of the calculated value using the particle transportation calculation code (MCNPX and PHITS) with the measured one, it is in good agreement.