Defect structure of pitting damage of mercury cavitation by MIMTM

Yoshiie, Toshimasa*; Sato, Koichi*; Xu, Q.*; Futakawa, Masatoshi  ; Naoe, Takashi   ; Kawai, Masayoshi*

A mercury target in high-power spallation neutron sources is subjected to the pressure wave caused by proton beam. Subsequent formation and collapse of cavitation bubbles lead to cavitation damage on the target vessel, especially the beam window. The cavitation damage in Ni and austenitic stainless steel SUS304SS were studied by using MIMTM (electro-Magnetic IMpact Testing Machine) developed to simulate the damage. The existence of dislocations, stacking fault tetrahedra and vacancies was detected by positron annihilation lifetime measurement in Ni and non-cellar dislocation structures were observed by transmission electron microscopy in Ni and SUS316SS. High density of twins was also observed in SUS304SS. These results were compared with those of high speed compression test by using high speed projectile and proved that the cavitation damage by MIMTM corresponded to high speed deformation.