Sep 20 – 24, 2021
America/Vancouver timezone

Beam Instability in the Vicinity of Beam Extraction Region of Negative Ion Source

Not scheduled
Poster Ion sources for fusion Poster Session 2


Kenichi Nagaoka (National Institute for Fusion Science, Japan)


Beam focusing is an important issue for application of negative ion beams. In particular, the beam focusing of RF type negative ion source for ITER has been intensively studied. Recently, the plasma fluctuation in the negative ion source is recognized to be able to affect the beam focusing.
In this study, the sheath stability was investigated both theoretically and experimentally. It is found that the beam instability become unstable in the negative ion presheath. To confirm the effect of beam instability, the fluctuations of source plasma and beamlet were simultaneously measured in the experiment. No significant correlation between the source plasma fluctuation and the beamlet shape was observed. It should be noted that spontaneous fluctuation in the beam extraction region does not affect the beam focusing, and RF field effect in RF negative ion source is the next step of this study.

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Funding Information JSPS KAKENHI(17H03002, 18KK0080), NIFS19KLER103

Primary authors

Haruhisa Nakano (National Institute for Fusion Science) Katsuyoshi Tsumori (National Institute of Fusion Science, SOKENDAI (The Graduate University for Advanced Students)) Kenichi Nagaoka (National Institute for Fusion Science, Japan) Katsunori Ikeda (National Institute for Fusion Science) Masaki Osakabe (NIFS) Masashi Kisaki Mr Ryoya Nakamoto (Nagaoka University of Technology) Dr Shinji Yoshimura (National Institute for Fusion Science) Mr Taiga Hamajima (Nagoya University) Dr Toru Sasaki (Nagaoka University of Technology) Dr Yutaka Fujiwara (National Institute for Fusion Science)

Presentation materials