Plasma and Fusion Research

Volume 21, 1202034 (2026)

Rapid Communications

First Plasma Experiment of Electron Cyclotron Resonance Heating by Optical Vortex Beam in Heliotron J
Zongyuhui HE1), Kazunobu NAGASAKI2), Toru TSUJIMURA3), Yasuhisa ODA4), Shinji KOBAYASHI2), Shigeru INAGAKI2), Shinichiro KADO2), Fumiyoshi KIN2), Shinichiro INAGAKI2), Shigeru KONOSHIMA2), Tohru MIZUUCHI2), Naoki KENMOCHI5)
1)
Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
2)
Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
3)
Kyoto Fusioneering Ltd., Heiwajima, Ota-ku, Tokyo 143-0006, Japan
4)
Department of Mechanical Engineering, Setsunan University, Neyagawa, Osaka 572-8508, Japan
5)
National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Gifu 509-5292, Japan
(Received 11 December 2025 / Accepted 13 April 2026 / Published 19 June 2026)

Abstract

Plasma experiments on electron cyclotron resonance heating (ECRH) using a high-power optical vortex beam (OVB) have been demonstrated for the first time in the Heliotron J stellarator/heliotron device. The OVB is generated by a spiral phase plate in a 70 GHz ECRH system. Plasmas are successfully sustained up to the second harmonic extraordinary (X) mode cut-off density. Virtually identical performance in terms of stored energy and density limits confirms the injection of the OVB as a heating tool comparable to Gaussian beams. These first results showed that the OVB is a possible method for the research on wave and plasma physics in magnetically confined fusion systems.

Keywords

electron cyclotron resonance heating, optical vortex beam, Heliotron J

DOI: 10.1585/pfr.21.1202034

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