Inverter type high voltage DC power supply for negative-ion-based neutral beam injectors

A design of a high-voltage DC power supply for future neutral beam injectors (NBI) is presented together with the latest R&D results for a 100-kV, 5-A, 5-kHz inverter-type power supply. A negative-ion based NBI is used for heating and current drive in the JT-60U (JAERI Tokamak-60 upgrade) and the FER (Fusion Experimental Reactor). For a high-voltage DC power supply of 500-1000 kV, an inverter-type DC power supply has been adopted. It consists of low-voltage converters, inverters, step-up transformers, and high-voltage rectifiers. Ion sources are protected from electrical breakdowns by stopping the inverters. As the first step, the same system was used in the 100-kV, 5-A acceleration power supply of the JAERI (Japan Atomic Energy Research Institute) electron-beam irradiation stand. The power supply is based on 5-kHz inverters. After the dummy load test, the power supply operated in conjunction with a plasma electron gun, and a 100-keV, 4-A electron beam has already been extracted