Plasma and Fusion Research

Volume 15, 2401029 (2020)

Regular Articles

Development of Cs-Free Negative-Ion Source by Sheet Plasma
Keito HANAI, Toshikio TAKIMOTO, Hiroki KAMINAGA, Akira TONEGAWA, Kohnosuke SATO1) and Kazutaka KAWAMURA
Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan
1)
Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
(Received 7 January 2020 / Accepted 17 March 2020 / Published 13 May 2020)

Abstract

The use of cesium leads complicates ion source operation and requires regular maintenance for continuous operation. The development of a negative-ion source without Cs seeding is desired in neutral beam injectors. A magnetized-sheet plasma producing negative ions using volume production without Cs seeding was designed. The experiment was performed by a TPDsheet-U and tested using steady-state hydrogen plasma. Two different types of grid structures were used in the experiment to extract the negative-ion beam: single- and multi-aperture grids. The multi-aperture grids have been developed to achieve more beam current. The negative hydrogen ions were successfully extracted from the sheet plasma using both single- and multi-aperture grids. The current densities of the ion beams increased with increasing discharge current and extraction voltage. At an extraction voltage of 9.5 kV and a discharge current of 80 A, the approximate current density of the negative hydrogen ion beam was 8.4 mA/cm2 for the case of single-aperture grids. At an extraction voltage of 9.5 kV and a discharge current of 50 A, the approximate current density of the negative hydrogen ion beam was 23 mA for the case of multi-aperture grids.

Keywords

neutral beam heating, negative-ion source, volume production, Cs-free, sheet plasma, TPD-type plasma source

DOI: 10.1585/pfr.15.2401029

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