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(EX8/6) Alfvén eigenmodes and their Impact on Plasma Characteristics in JT-60U

   
Y. Kusama , R. Nazikian , G. J. Kramer , H. Kimura , M. Saigusa , T. Ozeki , G. Y. Fu , K. Tobita , T. Oikawa , K. Shinohara , T. Kondoh , M. Moriyama , F. V. Tchernychev , M. Nemoto , A. Morioka , M. Iwase , N. Isei , T. Fujita , S. Takeji , M. Kuriyama , C. Z. Cheng , K. W. Hill , and the JT-60 Team 
 
Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Naka-machi, Naka-gun, Ibaraki-ken, 311-0193, Japan

Abstract
In weak or reversed magnetic shear plasmas of JT-60U , the excitation and the stabilization of Alfvén eigenmodes and their impact on energetic ion confinement were investigated with the negative-ion- based neutral beam injection at 330-360 keV. Toroidicity-induced Alfvén eigenmodes (TAEs) were observed in weak shear plasmas with $\rm\langle\beta_h\rangle \ge 0.1\%$ and $\rm0.4 \le v_{b\vert\vert}/v_A \le 1$. The stability of TAEs is consistent with the predictions by the NOVA-K code. New burst modes and chirping modes were observed at a higher beta regime of $\rm\langle\beta_h\rangle \ge 0.2\%$. The effect of TAEs, burst modes and chirping modes  on the fast ion confinement is small so far. The strongly-reversed shear plasma with the internal transport barrier suppresses Alfvén eigenmodes.

       

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