Lifetime estimation of microbubble in mercury

Naoe, Takashi   ; Hasegawa, Shoichi   ; Bucheeri, A.; Futakawa, Masatoshi  

Cavitation damage is a critical issue in high power mercury targets for pulsed spallation neutron sources. Cavitation is induced by pressure wave which is caused by rapid thermal expansion of mercury. Microbubble injection into the mercury target has studied to mitigate the cavitation damage. Bubble condition: distribution and size, will affect the mitigation effect. It is important to estimate bubble lifetime to determine the bubble distribution and injection region because the microbubbles are disappeared by dissolution and diffusion. In this study, since mercury is an opaque liquid, a shrinking behavior of helium microbubbles in contact with an acrylic wall were observed and their lifetime was measured. The actual lifetime of microbubble suspended in the liquid was estimated from the observed bubbles. The lifetime of microbubble in mercury is longer than that in water.