High power spallation targets for neutron sources are being developed in the world. Mercury target will be installed at the material science and life facility in J-PARC, which will promoted innovative science. The mercury target is subject to the pressure wave caused by the proton bombarding in the mercury. The pressure wave propagation induces the cavitation in mercury that imposes localized impact damage on the target vessel. The impact erosion is a critical issue to decide the lifetime of the target. The electro Magnetic IMpact Testing Machine, MIMTM, was developed to reproduce the localized impact erosion damage and evaluate the damage formation. Additionally, droplet impact analysis was carried out to investigate the correlation between isolate pit profile and micro-jet velocity. We confirmed that value of depth/radius was able to estimate micro-jet velocity. And the velocity at 560 W in MIMTM was estimated to be 225∼325 m/s. Furthermore, surface-hardening treatments inhibited pit formation in plastic deformation.
