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(EXP2/05) Alfvén Eigenmodes Driven by Energetic Ions in JT-60U

K. Shinohara¹⁾, Y. Kusama¹⁾, G. J. Kramer²⁾, M. Takechi¹⁾, A. Morioka¹⁾, M. Ishikawa¹⁾, N. Oyama¹⁾, K. Tobita¹⁾, T. Ozeki¹⁾, S. Takeji¹⁾, S. Moriyama¹⁾, T. Fujita¹⁾, T. Oikawa¹⁾, T. Suzuki¹⁾, T. Nishitani¹⁾, T. Kondoh¹⁾, S. Lee¹⁾, M. Kuriyama¹⁾, N. N. Gorelenkov²⁾, R. Nazikian²⁾, C. Z. Cheng²⁾, G. Y. Fu²⁾, A. Fukuyama³⁾ and the JT-60U Team^1)
 
1) Japan Atomic Energy Research Institute, Naka-machi, Naka-gun, Ibaraki 311-0193, Japan
²⁾ Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08543, USA
³⁾ Department of Nuclear Engineering, Kyoto University, 606-8501 Japan

Abstract.  Instabilities with frequency chirping in the frequency range of Alfvén eigenmodes have been found in the domain of 0.1% < $\langle$$\beta_{h}^{}$$\rangle$ < 1% and v_b|/v_A $\sim$ 1 with high energy neutral beam injection in JT-60U. One instability appears with frequency inside the Alfvén continuum spectrum and its frequency increases slowly to the Toroidicity induced Alfvén eigenmodes (TAE) gap in an equilibrium change time scale of $\sim$ 200 ms. Another instability appears with frequency inside the TAE gap and its frequency changes very fast by 10-20 kHz in 1-5 ms. During the occurrence of Fast FS modes, abrupt large-amplitude events often appears with an enhanced drop of neutron emission rate and increase in fast neutral particle fluxes. The loss of energetic ions increases with the peak fluctuation amplitude of $\bar{B}_{\theta}^{}$/B_$\theta$. Energy dependence of loss ions is observed and suggests the resonant interaction between energetic ions and a mode.

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