18th IAEA Fusion Energy Conference

Alfven 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-60 Team¹⁾
1)Naka Fusion Research Establishment, Japan Atomic Energy Research Institute
2)Princeton Plasma Physics Laboratory
3)Kyoto University

Abstract.
Instabilities with frequency chirping in the frequency range of Alfven eigenmodes have been found in the domain of < β_h > and v_b// / v_A ~ 1 with high energy neutral beam injection in JT-60U. One instability appears with frequency inside the Alfven continuum spectrum and its frequency increases slowly to the Toroidicity induced Alfven eigenmodes (TAE) gap in an equilibrium change time scale of ~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 B_θ B_θ. Energy dependence of loss ions is observed and suggests the resonant interaction between energetic ions and a mode.