Sep 20 – 24, 2021
America/Vancouver timezone

Effect of RF Electric Field on Beam Focusing in Negative Ion Source Plasma

Sep 24, 2021, 10:00 AM
Parallel Session (Contributed Oral) talk Ion sources for fusion


Mr Taiga Hamajima (Nagoya University)


Optimization for beam focusing of negative ions is one of the important issues for developing neutral beam injector (NBI) for ITER. Low beam divergence less than 5 mrad has been realized with Filament-Arc (FA) type negative ion sources. On the other hand, the divergence with Radiofrequency (RF) type sources is over 2 times larger than that obtained with FA sources, and the ITER requirement on the divergence less than 7 mrad has not been achieved so far.
In this study, the beam focusing is investigated when the RF electric field is externally applied in the beam extraction region of the FA source (NIFS-RNIS). A RF antenna is installed in the beam extraction region, and the RF electric field with a frequency range of 4-8 MHz is applied. A beamlet shape is measured, and the responses of beamlet width and beamlet axis position to the RF field are experimentally observed. It is found that the beam focus of negative ions is deteriorated with the RF electric field.

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Primary author

Mr Taiga Hamajima (Nagoya University)


Mr Ryoya Nakamoto (Ngaoka University of Technology) Kenichi Nagaoka (National Institute of Fusion Science, Nagoya University) Haruhisa Nakano (National Institute for Fusion Science) Engrhyt Rattanawongnara (The Graduate University for Advanced Studies, SOKENDAI) Katsuyoshi Tsumori (National Institute of Fusion Science, SOKENDAI (The Graduate University for Advanced Students)) Katsunori Ikeda (National Institute for Fusion Science) Masashi Kisaki Shingo Masaki Kenji Miyamoto Masaki Osakabe (NIFS) Prof. Kazunori Takahashi (Tohoku University) Shinji Yoshimura (National Institute for Fusion Science)

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