Observation of a beam-driven low-frequency mode in Heliotron J

L. G. Zang, S. Yamamoto, D. A. Spong, K. Nagasaki, S. Ohshima, S. Kobayashi, T. Minami, X. X. Lu, N. Nishino, S. Kado, P. Adulsiriswad, H. Okada, N. Kenmochi, S. Inagaki, J. X. Zhu, G. M. Weir, T. Mizuuchi, S. Konoshima, A. Ishizawa, D. L. YuZ. B. Shi, Yi Liu, L. W. Yan, J. Q. Li, Q. W. Yang, M. Xu, X. R. Duan, Yong Liu

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1 Citation (Scopus)

Abstract

A low-frequency electromagnetic mode (LF-mode) has been observed in a stellarator/heliotron device, Heliotron J. The LF-mode is observed only in neutral beam heated plasmas with a co-current, which increases the rotational transform. The observed LF-mode peaks at rho = 0.86-0.91, where rho = r/a is the normalized minor radius. The LF-mode propagates in the ion diamagnetic drift direction, and the poloidal mode number is m ∼ 6-8, determined with a combination of Mirnov coil arrays and 2D fast camera measurement. A high m number induces significant Doppler shift from the background ion flow. The frequency is corrected with both E × B rotation and the ion diamagnetic flow. The corrected frequency is almost consistent with the beta-induced Alfvén eigenmode gap evaluated with the STELLGAP code, although very close to the accumulation point. The mode could also be a global Alfvén eigenmode.

Original languageEnglish
Article number056001
JournalNuclear Fusion
Volume59
Issue number5
DOIs
Publication statusPublished - Mar 14 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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