J-PARC MLFの大強度ビームコミッショニングの現状

抄録

In the Japanese Spallation Neutron Source (JSNS) of Japanese Proton Accelerator Research Complex (J-PARC), the proton beam with a high power of 1 MW was successfully introduced to the mercury target. In 2015, the beam operation with the power of 500 kW has started. As increasing the beam power, the pitting damage to the target vessel becomes serious. To mitigate the damage, reduction of the peak current density at the target is important for high power beam operation. In order to reduce the peak current density, a beam flattening system with non-linear beam optics using octupole magnets has been developed. It was found that a considerably flat distribution could be obtained with the octupole magnets. The calculated beam profile showed good agreement with the experimental result for 0.8 MW. The peak current density can be reduced as much as 30 %, which mitigates 76 % of the pitting damage at the vessel of the target.