R&D on mercury target for spallation neutron source to improve the durability under high power operation, 2

Kawashima, Hiroyuki; Kogawa, Hiroyuki  ; Futakawa, Masatoshi  ; Soyama, Hitoshi*; Kuji, Chieko*; Tanaka, Nobuatsu*

In the J-PARC mercury target, helium gas bubbles are injected to mitigate cavitation damage. However, it was recently shown that this injected gas bubbles may cause the damage. In this study, we focused on the local impact force generated when the bubbles collapse, as the first step to propose the optimum condition of the injected gas bubbles. Bubble behavior generated by the underwater spark discharge method near a wall surface was taken by the high-speed camera. At the same time, the vibration on the wall surface due to local impact force was measured with a laser Doppler vibrometer. In addition, bubble behavior was calculated by Keller-Miksis equation. Relationship between local impact force and bubble behavior will be discussed.