Pitting damage due to ca vital ion micro-bubble collapse is one of critical issue to realize a MW-scate mercury target for spallation neutron source. Micro-impact analysis was carried out to discuss the pit formation by mercury micro-jet impact. It was confirmed from the comparison between analytical and experimental results that D(depth)/R(radius) of pits is a useful parameter to estimate the impact velocity and surface hardening treatment is effective to suppress the pitting damage.
