Recent progress in R&D for long pulse and ultra-high voltage components for the ITER HNB

Kashiwagi, Mieko; Umeda, Naotaka; Kojima, Atsushi; Yoshida, Masafumi; Tobari, Hiroyuki; Dairaku, Masayuki; Yamanaka, Haruhiko; Maejima, Tetsuya; Yamashita, Yasuo*; Shibata, Naoki; Watanabe, Kazuhiro; Hanada, Masaya

JAEA proceeds the R&Ds of high voltage components, such as 1MeV accelerator and high voltage power supply for the ITER neutral beam injector for heating (ITER HNB). In the 1MeV accelerator R&D, the target is to produce 1MeV beams during several tens of seconds using a five-stage multi-aperture accelerator. In the extraction grid, cooling capability is enhanced to accept electrons during long period and aperture offset is applied to correct the beam deflection due to magnetic fields in the accelerator. As the result, the heat load on the acceleration grids was reduced from 23% to 13%. The beam energy was increased from 0.9MeV to 1MeV at short pulse of 0.4s. The beam pulse was increased by a factor of one hundred, 60s, at 0.7MeV up to now. In the R&D of the power supply, a 1MV bushing of 1MV insulating transformer has been newly developed and a stable operation at 1.2MV with the margin of 20% was achieved for 3600s. Thus, the R&Ds for the ITER HNB is progressed as scheduled.