[Table of Contents]

Plasma and Fusion Research

Volume 10, 3405016 (2015)

Regular Articles

Spatial Distributions of Charged Particles and Plasma Potential before and during Beam Extraction in a Negative Hydrogen Ion Source for NBI
Shaofei GENG, Katsuyoshi TSUMORI1), Haruhisa NAKANO1), Masashi KISAKI1), Yasuhiko TAKEIRI1), Masaki OSAKABE1), Katsunori IKEDA1), Ken-ichi NAGAOKA1), Osamu KANEKO1), Masayuki SHIBUYA1) and NIFS NBI Group1)
SOKENDAI (The Graduate University for Advanced Studies), 322-6 Oroshi, Toki, Gifu 509-5292, Japan
1)
National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
(Received 25 November 2014 / Accepted 26 January 2015 / Published 19 March 2015)

Abstract

In order to understand the physics of the production and extraction mechanism of negative ions, experiments with a single Langmuir probe are carried out to investigate the local spatial distribution of the plasma in the vicinity of the plasma grid in a negative hydrogen ion source. The results show that the electron density is lower in the aperture region than that in its peripheral region. It is attributed to the cusp magnetic field introduced with the electron deflection magnets near the plasma grid. In addition, the linkage of the filter field with the electron deflection magnetic field contributes to the increment of electron density. The profile of plasma potential indicates that an electric field exists between the aperture and its peripheral region, and then a local negative ion flow can be introduced near the plasma grid.

Keywords

neutral beam injection, negative ion source, Langmuir probe, spatial distribution, magnetic field

DOI: 10.1585/pfr.10.3405016

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This paper may be cited as follows:

Shaofei GENG, Katsuyoshi TSUMORI, Haruhisa NAKANO, Masashi KISAKI, Yasuhiko TAKEIRI, Masaki OSAKABE, Katsunori IKEDA, Ken-ichi NAGAOKA, Osamu KANEKO, Masayuki SHIBUYA and NIFS NBI Group, Plasma Fusion Res. 10, 3405016 (2015).