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(EXP1/19) Global MHD Modes Excited by Energetic Ions in Helitron/Torsatron Plasmas

K. Toi, M. Takechi¹, S. Takagi¹, G. Matsunaga¹, M. Isobe, T. Kondo², M. Sasao, D. S. Darrow³, K. Ohkuni¹, 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. Nikai¹, S. Nishimura, S. Okamura, M. Osakabe, A. Shimizu¹, Y. Shirai², C. Takahashi, K. Tanaka, T. Watari, Y. Yoshimura

National Institute for Fusion Science, Toki-shi 509-5292, Japan
¹ Dep. Energy Eng. Science, Nagoya Univ., Nagoya 464-8603, Japan
² The Graduate Univ. for Advanced Studies, Toki-shi, 509-5292, Japan
³ Princeton Plasma Physics Laboratory, Princeton, N.J., U.S.A.

Abstract.  In the CHS heliotron/torsatron, fishbone instabilities(FBs) and toroidal Alfven eigenmodes(TAEs) are observed for the first time, in NBI heated plasmas where small beam driven current is induced. Pulsed increase in energetic ion loss flux is detected by an escaping ion probe during the m=3/n=2 FBs(m,n: poloidal and toroidal mode numbers). The sawtooth crash is often induced by the m=2/n=1 FBs. The current driven internal kink mode and pressure driven interchange modes are thought to be relevant MHD instabilities to FBs. TAEs with n=1 and n=2 are identified, and localized near the plasma core region where fairly low magnetic shear would be realized by the small net plasma current. So far, the observed TAEs do not lead to enhanced loss of energetic ions because of low magnetic fluctuation level.

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