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Kamada, Masaki; Hanada, Masaya; Ikeda, Yoshitaka; Grisham, L. R.*
AIP Conference Proceedings 1097, p.412 - 420, 2009/03
To reduce heat loading of large-area, multi-aperture grids due to interception of negative ion beam, newly-designed field-shaping plates (FSPs) were installed in JT-60U negative ion source. Design of the FSPs based on results of 3D simulation of multiple-beamlets trajectory. It was found that overfocusing of outermost beamlet can be improved by thinner and farther FSP than previous FSP. Furthermore, positions of FSPs were adjusted in each horizontal row of apertures to suppress deflection of the ion beam due to dipole magnetic field for electron suppression. As test results of the newly-designed FSP, the newly-designed FSP significantly reduced the overfocusing of the outermost beamlet from -10 mrad to -5 mrad at 350 kV in acceleration voltage and the power loading of grounded grid from 9% to 7% of drain power. This level of the power loading is allowable in JT-60SA where the negative ion beam with 500 keV, 22 A for 100 s is required.
accelerator at JAEA for ITER NBTaniguchi, Masaki; DeEsch, H. P. L.*; Svensson, L.*; Umeda, Naotaka; Kashiwagi, Mieko; Watanabe, Kazuhiro; Tobari, Hiroyuki; Dairaku, Masayuki; Sakamoto, Keishi; Inoue, Takashi
AIP Conference Proceedings 1097, p.335 - 343, 2009/03
Kashiwagi, Mieko; Inoue, Takashi; Grisham, L. R.*; Hanada, Masaya; Kamada, Masaki; Taniguchi, Masaki; Umeda, Naotaka; Watanabe, Kazuhiro
AIP Conference Proceedings 1097, p.421 - 430, 2009/03
One of the issues in long pulse operation of large negative ion source with multiaperture accelerator is an excess heat loads on to grids by the beamlet deflection due to their space charge repulsion. To compensate this beamlet deflection, the beamlet steering technique by aperture offset was examined in a three dimensional beam analyses simulating D negative ion source of JT-60U. The result shows that proper aperture offsets of 
1.0 mm were enough to compensate each beamlet deflection. When the magnetic field for suppression of co-extracted electrons was applied, necessary aperture offset of 0.5 mm was necessary for 500 keV D ion beam in JT-60U in addition to the offset for compensation of space charge repulsion. The numerical analyses showed good agreement with the former experimental results and design study.
Kisaki, Masashi; Hanada, Masaya; Kamada, Masaki; Tanaka, Yutaka; Kobayashi, Kaoru; Sasao, Mamiko*
AIP Conference Proceedings 1097, p.344 - 352, 2009/03
The stripped electron trajectories in a large negative ion accelerator with multi-apertures and three acceleration stages, where non-uniform stray magnetic field is horizontally created, are calculated in the JT-60 negative ion source by the 3-D numerical code. The horizontal non-uniform stray field results in a significant power loss of the stripped electrons in the outmost acceleration channel on the grounded grid (GRG). The power loss in the outmost acceleration channel is more than twice higher than that in the central channel due to the weaker stray field although the total power loading on the GRG is by 25% larger than that by assuming a uniform stray field.
DeEsch, H. P. L.*; Svensson, L.*; Inoue, Takashi; Taniguchi, Masaki; Umeda, Naotaka; Kashiwagi, Mieko; Fubiani, G.*
AIP Conference Proceedings 1097, p.353 - 363, 2009/03
CEA Cadarache and JAEA Naka have entered into a collaboration in order to test a SINGAP accelerator at the Megavolt Test Facility (MTF) at Naka, Japan. Whereas at the CEA testbed the acceleration current was limited to 0.1 A, at JAEA 0.5 A is available. This allows the acceleration of 15 H beamlets in SINGAP to be tested and a direct comparison between SINGAP and MAMuG to be made. High-voltage conditioning in the SINGAP configuration has been quite slow, with 581 kV in vacuum achieved after 140 hours of conditioning. With 0.1 Pa of H
gas present in the accelerator 787 kV could be achieved. The conditioning curve for MAMuG is 200 kV higher. A beamlet divergence better than 5 mrad was obtained. SINGAP accelerates electrons to a higher energy than MAMuG. Based on the experiments described here, electron production by a SINGAP accelerator scaled up to ITER size was estimated to be too high for comfort.
