We have developed the high voltage power-supply unit for ingenerate high pressure due to underwater shockwave by discharging and electrical sparking consists of Cockcroft-Walton circuit. This power supply has the problem of the contact switch operation due to melting of materials of contact switch by electrical spark. We have studied the optimization of materials of contact switch by reducing energy loss and problem of operation. In this research, We changed material of contact switch metal to carbon. And verified that new contact switch made of carbon is effective to reduce energy loss and solve problem of contactor switch operation.
