Toroidal Alfvén eigenmodes driven with ICRF accelerated protons in JT-60U negative shear discharges

Y. Kusama, H. Kimura, T. Ozeki, M. Saigusa, G. J. Kramer, T. Oikawa, S. Moriyama, M. Nemoto, T. Fujita, K. Tobita, G. Y. Fu, R. Nazikian, C. Z. Cheng

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40 Citations (Scopus)

Abstract

On JT-60U, for the first time in negative shear plasmas, toroidicity induced Alfvén eigenmodes (TAEs) with frequencies in the range of 90 to 110 kHz and toroidal mode numbers n = 5-8 were observed after a broadening of the density profile due to sequential partial collapses during ion cyclotron range of frequency (ICRF) heating. TAEs are more stable in negative shear plasmas than plasmas with a monotonically increasing q profile. The TAE stability was analysed with the NOVA-K code. It was found that the stability is highly sensitive to the gap alignment just inside qmin and that the theoretical results are consistent with the experimental results. In a weak central magnetic shear discharge, modes with very rapid frequency chirping were observed during ICRF heating. The frequencies of these modes rapidly increased from ∼30 kHz up to ∼110 kHz in a period of ∼150 ms. The large frequency chirping is not well understood by the present theory.

Original languageEnglish
Pages (from-to)1215-1223
Number of pages9
JournalNuclear Fusion
Volume38
Issue number8
DOIs
Publication statusPublished - 1998 Dec 1
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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