Plasma and Fusion Research
Volume 10, 3405045 (2015)
Regular Articles
- Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka-shi, Ibaraki 311-0193, Japan
Abstract
To produce high current density (> 200 A/m2), high-energy (> 1 MeV) negative ion beams for long pulse duration time (1 hour) for International Thermo-nuclear Experimental Reactor (ITER), the suppression of the direct interception of the negative ions with the grids has been carefully investigated with studying the deflection angle by aperture displacement technique. The non-linear dependence of the deflection angle appears at the aperture diameter of > 14 mm on a steering control grid (SCG). From this dependence, the aperture diameter and the offset distance of the SCG has been designed to be 16 mm and 0.7 mm, respectively and tested in a prototype accelerator for ITER. Each of the beamlets on the multiple apertures is properly steered with compensation of the deflection due to the residual magnetic field in the accelerator and the grid power loading was significantly reduced. It resulted in a 10% enhancement of the accelerated beam current.
Keywords
ITER, neutral beam injection, accelerator, negative ion, beam steering control, electrostatic lens, space charge, MeV accelerator
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This paper may be cited as follows:
Junichi HIRATSUKA, Masaya HANADA, Naotaka UMEDA, Atsushi KOJIMA, Mieko KASHIWAGI, Kazuhiro WATANABE, Hiroyuki TOBARI and Masafumi YOSHIDA, Plasma Fusion Res. 10, 3405045 (2015).