Development of the high power mercury target and the bubbler installation

Haga, Katsuhiro  ; Kogawa, Hiroyuki  ; Wakui, Takashi  ; Naoe, Takashi   ; Futakawa, Masatoshi  

Cavitation damage caused by the pressure wave in mercury is the crucial issue for the high power mercury target. Microbubble injection into mercury is the technology to mitigate the pressure wave, and the techniques to generate microbubbles in mercury flow, and to achieve the proper distribution of microbubbles have been investigated. We developed the swirl type bubbler which can generate the microbubbles efficiently. We performed mercury flow experiments using the target mockup model. We found that the proper size of microbubbles were distributed in the target, but the void fraction was less than 10 at the bottom area, which was lower than an expected value. In order to increase the void fraction, we changed the design of the mercury flow channel, moving the bubbler position forward near the beam window. With the help of the swirl flow, the homogeneity of microbubbles distribution at the beam window will be improved and the void fraction at the bottom area will be increased.