High energy, high current accelerator development for ITER NBI at JADA

Kashiwagi, Mieko; Taniguchi, Masaki; Dairaku, Masayuki; DeEsch, H. P. L.*; Grisham, L. R.*; Svensson, L.*; Tobari, Hiroyuki; Umeda, Naotaka; Watanabe, Kazuhiro; Sakamoto, Keishi; Inoue, Takashi

At JAEA, beam parameters achieved by the MAMuG (multi-aperture multi-grid) accelerator were increased to 0.32 A H at the ion current density of 140 A/m and 796 keV at the beam energy. This was achieved as the result of countermeasures to handle unexpected heat load by backstream positive ions. A test of SINGAP (single-aperture single-gap) accelerator, which was performed at JAEA under an ITER R&D task agreement. The objective of this study was to compare the two different accelerator concepts (SINGAP and MAMuG) at the same test facility. As the result, it was concluded that the MAMuG accelerator was more suitable for the ITER NBI because of its better voltage holding and less electron acceleration. A simulation is in progress for space charge repulsion of beamlets in the JT-60U accelerator. An aperture offset steering was suggested effective at exit of extractor for compensation of the beamlet deflection due to its own space charge.