| IT05 · Observation of Confinement Degradation of Energetic Ion due to Alfvén
Eigenmodes in weak shear plasmas on JT-60U
M. Ishikawa, M. Takechi, K. Shinohara, Y. Kusama, G. Matsunaga, V. A. Krasilnikov 1, Yu. Kashuck1
, M. Isobe2, T. Nishitani, A. Morioka, M. Sasao4, C. Z. Cheng4, N. N. Gorelenkov5, G. J.
Kramer5, R. Nazikian5, and JT-60 team
Japan Atomic Energy Agency, Naka-Shi, Ibaraki 319-0193, Japan
1 Troitsk Institute of Innovating and Fusion Research, Troitsk, Moscow region 142092, Russia
2 National Institute for Fusion Science, Toki-Shi, Gifu 509-5292, Japan
3 Department of Engineering, Tohoku Univ., Sendai-Shi, Miyagi 980-8578, Japan
4 National Space Organization, Hsin Chu City 300, Taiwan
5 Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543, USA
Abstract: Confinement degradation due to Alfvén Eigenmodes has been investigated with negative ion based injection at ~
370 keV into weak shear plasmas on JT-60U. The AEs with a rapid frequency sweeping and then saturation as the minimum
value of safety factor (qmin) decrease have been observed. These frequency behavior can be explained by reversed-shear induced
AE (RSAE) and the transition from RSAE to TAE. Reduction rate of total neutron emission rate in the presence of AEs is
evaluated by calculation with Orbit Following Monte-Carlo code taking into account changing in bulk plasmas. The changes in
total neutron emission rate and CX-NP flux suggested energetic ion transport due to these AEs. The evolution indicates
confinement of energetic ions is degraded due to AEs. In particular, it is found confinement degradation is maximum during
transition from RSAE to TAE and the maximum reduction rate (ΔSn/Sn)MAX is estimated ~ 45
%.
Note: In special issue in Nuclear Fusion
- volume 46, issue 10
http://www.iop.org/EJ/toc/0029-5515/46/10
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Synopsis (pdf)