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Characteristics of a Large Diameter Radio-Frequency Negative Hydrogen Ion Source

Yuko SASAKI, Sho TAKAYAMA, Haruhisa NAKANO¹⁾, Atsushi KOMURO, Kazunori TAKAHASHI and Akira ANDO

Department of Electrical Engineering, Tohoku University, 6-6-05 Aoba-yama, Sendai, Miyagi 980-8579, Japan

1)

National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan

(Received 30 November 2015 / Accepted 7 April 2016 / Published 10 June 2016)

Abstract

The characteristics of a 230-mm-diameter radio-frequency (rf) negative hydrogen ion source are investigated by the measurements of electron density and temperature. A hydrogen plasma is produced by an inductively coupled discharge operated with an rf frequency of 300 kHz and a power of a few tens of kW, where a field-effect-transistor-based inverter power supply is used as an rf generator. The ion source has a magnetic filter for reduction of the electron temperature near the plasma grid used for the extraction of a negative ion beam. A high electron density greater than 10¹⁸ m⁻³ is successfully obtained for an operating gas pressure of 0.3 Pa. The electron temperature near the plasma grid is observed to decrease to about 1 eV with increasing magnetic field strength of the magnetic filter.

Copyright (c) 2016 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

RF ion source, NBI, ion source, negative hydrogen ion, FET-based inverter rf power supply

DOI: 10.1585/pfr.11.2405088

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