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Author(s):
K. Toi, M. Takechi, S. Takagi, G. Matsunaga, M. Isobe, T. Kondo, M. Sasao, D.S. Darrow, K. Ohkuni, S. Ohdachi, R. Akiyama A. Fujisawa, M. Gotoh, H. Idei, K. Ida, H. Iguchi, S. Kado, M. Kojima, S. Kubo, S. Lee, K. Matsuoka, T. Minami, S. Morita, N. Nikai, S. Nishimura, S. Okamura, M. Osakabe, A. Shimizu, Y. Shirai, C. Takahashi, K. Tanaka, T. Watari and Y. Yoshimura
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Title:
Global MHD Modes Excited by Energetic Ions in Heliotron/Torsatron Plasmas
Date of publication:
Oct. 1998
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Key words:
IAEA, fusion energy conference, Yokohama
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Abstract:
In NBI heated plasmas of the CHS heliotron/torsatron where the beam driven current with a peaked profile is induced, m=2/n=1 and m=3/n=2(m,n : poloidal and toroidal mode numbers) fishbone instabilities are observed for the first time. Pulsed increase in energetic ion loss flux is detected by an escaping ion probe during the m=3/n=2 mode. The sawtooth crash is often induced by the m=2/n=1 mode. The current driven internal kink mode is thought to be destabilized by the presence of energetic ions, having a character of pressure driven interchange mode. Toroidal Alfven eigenmodes(TAEs) with n=1 and n=2 are also identified for the first time in NBI heated plasmas. TAEs localize near the plasma core region with fairly low magnetic shear realized by the small net plasma current, and do not lead to enhanced loss of energetic ions because of low fluctuation level.
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