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Electric Potential Structure in the Extraction Region of the Negative Hydrogen Ion Source

Shingo MASAKI¹⁾, Kenta MAESHIRO²⁾, Katsuyoshi TSUMORI^1,3) and Motoi WADA²⁾

1)

Department of Fusion Science, SOKENDAI (The Graduate University for Advanced Studies), Toki, Gifu 509-5292, Japan

2)

School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0394, Japan

3)

National Institute for Fusion Science, Toki, Gifu 509-5292, Japan

(Received 9 January 2019 / Accepted 4 June 2019 / Published 14 August 2019)

Abstract

Plasma parameters were compared in the extraction region of a negative hydrogen (H⁻) ion source between the discharge sustained by tungsten (W) and tantalum (Ta) high temperature cathodes. A hydrogen plasma driven by the Ta filament showed lower electron temperature and higher ratio of positive ion saturation current to negative ion/electron saturation current than a plasma excited by the W filament. Plasma potential indicated different spatial distribution along the direction of H⁻ ion extraction corresponding to the voltage biased on the plasma electrode. These results are correlated to the intensities of the H⁻ ion extraction current.

Copyright (c) 2019 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

negative hydrogen ion, plasma parameter, Langmuir probe, negative ion extraction, filament material

DOI: 10.1585/pfr.14.3401136

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