Alfvén eigenmodes driven by Alfvénic beam ions in JT-60U

K. Shinohara, Y. Kusama, M. Takechi, A. Morioka, M. Ishikawa, N. Oyama, K. Tobita, T. Ozeki, S. Takeji, S. Moriyama, T. Fujita, T. Oikawa, T. Suzuki, T. Nishitani, T. Kondoh, S. Lee, M. Kuriyama, G. J. Kramer, N. N. Gorelenkov, R. NazikianC. Z. Cheng, G. Y. Fu, A. Fukuyama

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Abstract

Instabilities with frequency chirping in the frequency range of Alfvén eigenmodes have been found in the domain 0.1% < 〈β h〉 < and v b||/v A ∼ 1 with high energy neutral beam injection in JT-60U. One instability with a frequency inside the Alfvén continuum spectrum appears and its frequency increases slowly to the toroidicity induced Alfvén eigenmode (TAE) gap on the timescale of an equilibrium change (≈200 ms). Other instabilities appear with a frequency inside the TAE gap and their frequencies change very quickly by 10-20 kHz in 1-5 ms. During the period when these fast frequency sweeping (fast FS) modes occur, abrupt large amplitude events (ALEs) often appear with a drop of neutron emission rate and an increase in fast neutral particle fluxes. The loss of energetic ions increases with a peak fluctuation amplitude of B̃ θ/B θ. An energy dependence of the loss ions is observed and suggests a resonant interaction between energetic ions and the mode.

Original languageEnglish
Pages (from-to)603-612
Number of pages10
JournalNuclear Fusion
Volume41
Issue number5
DOIs
Publication statusPublished - 2001 May 1

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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    Shinohara, K., Kusama, Y., Takechi, M., Morioka, A., Ishikawa, M., Oyama, N., Tobita, K., Ozeki, T., Takeji, S., Moriyama, S., Fujita, T., Oikawa, T., Suzuki, T., Nishitani, T., Kondoh, T., Lee, S., Kuriyama, M., Kramer, G. J., Gorelenkov, N. N., ... Fukuyama, A. (2001). Alfvén eigenmodes driven by Alfvénic beam ions in JT-60U. Nuclear Fusion, 41(5), 603-612. https://doi.org/10.1088/0029-5515/41/5/313