Development of 1 MeV accelerator and HV bushing at JAEA toward ITER neutral beam system

Umeda, Naotaka; Taniguchi, Masaki; Kashiwagi, Mieko; Dairaku, Masayuki; Hanada, Masaya; Tobari, Hiroyuki; Watanabe, Kazuhiro; Sakamoto, Keishi; Inoue, Takashi

The R&D of MeV class accelerator and high voltage bushing toward ITER neutral beam system are in progress at JAEA. To demonstrate the 1 MeV class negative ion beam acceleration, a MeV accelerator has been developed at MeV Test Facility. A H ion beam of 320 mA (current density: 140 A/m) was successfully accelerated up to 796 keV by fixing air leak in the ion source chamber caused by heat loading due to backstream positive ions. For development of the HV bushing, a half-size ( 800 mm) mockup single stage bushing was manufactured and tested, that demonstrated the dc voltage holding capability of up to 220 kV. Electrostatic analyses and design of the HV bushing are in progress, in which some design improvements are suggested to reduce electric field strength on the surface of ceramic insulator.