R&D on pressure-wave mitigation technology for pulsed high-power mercury targets; Bubble flow simulations

Haga, Katsuhiro  ; Futakawa, Masatoshi  ; Kogawa, Hiroyuki  ; Wakui, Takashi  ; Naoe, Takashi   ; Yamazaki, Shogo*; Tanaka, Nobuatsu*

Pressure wave, which is caused by the thermal shock in mercury at the moment the high intense proton beams bombard mercury, is a crucial issue to realize a pulsed high-power mercury target for spallation neutron sources. R&D on pressure wave mitigation technologies is carried out in JSNS. Micro-bubbles injection into mercury is one of prospective technologies to mitigate the pressure waves. The CFD simulation was carried out to investigate the injected bubble distribution in our mercury target that is influenced by bubble size and bubbling location. Also, the micro-bubbles effect was experimentally investigated from the viewpoint of pitting damage in the mercury loop with MIMTM (electro-Magnetic IMpact Testing Machine) and examined numerically from the viewpoint of bubble dynamics. As results, we confirmed that the micro-bubble is very effective to reduce the pressure response and pitting damage.