Mitigation of NBI-driven Alfvén eigenmodes by electron cyclotron heating in the TJ-II stellarator

K. Nagaoka, T. Ido, E. Ascasíbar, T. Estrada, S. Yamamoto, A. V. Melnikov, A. Cappa, C. Hidalgo, M. A. Pedrosa, B. Ph Van Milligen, I. Pastor, M. Liniers, M. A. Ochando, A. Shimizu, L. G. Eliseev, S. Ohshima, K. Mukai, Y. Takeiri

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Abstract

Alfvén eigenmode (AE) activity driven by NBI-produced fast ions is observed in TJ-II plasmas. A two-step response of the measured AEs to electron cyclotron heating (ECH) power is seen. In a first step, the continuous character of the unstable AEs changes to a chirping character of the marginally unstable AEs when moderate values of ECH power are applied to the NBI-only-heated plasma. In a second step, a significant reduction of the AE amplitude is observed when the ECH power is doubled. This stabilizing effect has been experimentally confirmed both on a shot-by-shot basis and along a single discharge by means of ECH modulation. The observed stabilizing effect is stronger with on-axis ECH than with off-axis ECH power injection.

Original languageEnglish
Article number072004
JournalNuclear Fusion
Volume53
Issue number7
DOIs
Publication statusPublished - Jul 1 2013
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Nagaoka, K., Ido, T., Ascasíbar, E., Estrada, T., Yamamoto, S., Melnikov, A. V., ... Takeiri, Y. (2013). Mitigation of NBI-driven Alfvén eigenmodes by electron cyclotron heating in the TJ-II stellarator. Nuclear Fusion, 53(7), [072004]. https://doi.org/10.1088/0029-5515/53/7/072004