Local observations of fast ion responses to energetic particle modes using a directional probe in the Compact Helical System (CHS)

K. Nagaoka, M. Isobe, K. Toi, K. Goto, T. Ito, Y. Todo, M. Osakabe, S. Ohshima, A. Shimizu, A. Fujisawa, H. Nakano, Y. Takeiri, K. Y. Watanabe, T. Akiyama, Y. Yoshimura, C. Suzuki, S. Nishimura, K. Matsuoka, S. Okamura

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Abstract

Bursting energetic particle mode (EPM) and fast ion loss induced by the EPM have been observed and experimentally investigated in the Compact Helical System (CHS). A directional probe method was newly applied to neutral beam heated plasmas for fast ion measurement, and it successfully revealed fast ion behaviour inside the last closed flux surface (LCFS) during bursting EPMs. A convective oscillation was observed only inside the LCFS, and drives little loss of fast ions. An anomalous loss of fast ions produced by the phase difference between the fast ion oscillation and the EPM with m = 3/n = 2 was observed in the outward shifted configurations. Another anomalous loss of fast ions due to EPMs with m = 2/n = 1 was also observed in the inward shifted configuration. The characteristics of the fast-ion-loss flux are different from those observed in the outward shifted configurations, and the loss mechanism seems to be related to a mode mixture between the EPM and a low frequency mode.

Original languageEnglish
Article number084005
JournalNuclear Fusion
Volume48
Issue number8
DOIs
Publication statusPublished - Aug 1 2008
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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