IAEA Fusion Energy Conference 2010

Proceedings of the 23rd IAEA Fusion Energy Conference
Daejeon, 11-16 October 2010

Organized by the International Atomic Energy Agency
and hosted by the Government of the Republic of Korea


(FTP/1-1Ra) Demonstration of 500 keV Beam Acceleration on JT-60 Negative-ion-based Neutral Beam Injector

A. Kojima1), M. Hanada1), Y. Tanaka1), M. Kawai1), N. Akino1), M. Kazawa1), M. Komata1), K. Mogaki1), K. Usui1), S. Sasaki1), K. Kikuchi1), N. Seki1), S. Nemoto1), K. Oshima1), T. Simizu1), N. Kubo1), K. Oasa1), T. Inoue1), K. Watanabe1), M. Taniguchi1), M. Kashiwagi1), H. Tobari1), S. Kobayashi2), Y. Yamano2), L.R. Grisham3)
1) Japan Atomic Energy Agency, Naka, Ibaraki 311-0193, Japan
2) Saitama University, Saitama, Saitama-ken, 338-8570, Japan
3) Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA

Abstract.  Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. This is the first acceleration of the H- ions up to 500 keV at high-current of > 1 A. These successful productions of the high-energy beams at high current have been achieved by overcoming a poor voltage holding of the large negative ion sources with the grids of ∼2 m2. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6 - 7 times longer than that for the small-area grid (0.02 m2). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.

Full paper and slides available (PDF)