Mr
Panith Adulsiriswad
(Graduate School of Energy Science, Kyoto University)
Magnetohydrodynamic (MHD) and energetic particle hybrid simulation code, MEGA, is applied to Heliotron J, an advanced stellarator/heliotron device with low magnetic shear, helical axis, and finite vacuum magnetic well. Due to the low magnetic shear, the global Alfvén eigenmode (n/m=2/4) has been dominantly observed, along with the energetic particle mode (n/m=1/2) in the experiment. In a recent experiment, a low frequency mode has also been observed when the plasma current is ramped up to a certain threshold. A bump at the high energy tail of the energetic particle distribution is observed in Heliotron J experiment for particles with low pitch angle, due to the significant charge-exchange loss at the 
peripheral region. It is gradually changed to the slowing-down distribution for particles with high pitch angles. The objective of this paper is to clarify the interaction between energetic particles and magnetohydrodynamic waves in the experiment and present the dependency of the energetic particle-driven mode on the equilibrium energetic particle distribution function. In this calculation, MHD equilibrium is based on the low bumpiness (low toroidal magnetic mirror) configuration. The slowing-down and the bump-on-tail distributions are utilized to study the dependency of energetic particle mode and global Alfvén eigenmode on the energy distribution. The n/m=1/2 energetic particle mode and the n/m=2/4 global Alfvén eigenmode have been successfully reproduced in the simulation. Both the n/m =1/2 and 2/4 modes are dominantly destabilized by two velocity ranges of the passing energetic particles, which are 7 to 14 keV, and 20 to 24 keV, where the injection energy is 28 keV. This results in no significant difference in the linear growth rate of the mode, despite changing the location of the distribution peak in energetic particle energy distribution. The discrepancies between the simulation and the experiment will be discussed for further improvement.
| Country or International Organization |
Japan
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Mr
Panith Adulsiriswad
(Graduate School of Energy Science, Kyoto University)
Prof.
Akihiro Ishizawa
(Graduate School of Energy Science, Kyoto University)
Prof.
Hiroyuki Okada
(Institute of Advanced Energy, Kyoto University)
Prof.
Kazunobu Nagasaki
(Institute of Advanced Energy, Kyoto University)
Prof.
Satoshi Yamamoto
(Naka Fusion Institute, National Institutes for Quantum and Radiological Science and Technology)
Prof.
Shigeru Konoshima
(Institute of Advanced Energy, Kyoto University)
Prof.
Shinichiro Kado
(Institute of Advanced Energy, Kyoto University,)
Prof.
Shinji Kobayashi
(Institute of Advanced Energy, Kyoto University)
Prof.
Shinsuke Ohshima
(Institute of Advanced Energy, Kyoto University)
Prof.
Takashi Minami
(Institute of Advanced Energy, Kyoto University)
Prof.
Tohru Mizuuchi
(Institute of Advanced Energy, Kyoto University)
Prof.
Yasushi Todo
(National Institute of Fusion Science)
Prof.
Yuji Nakamura
(Graduate School of Energy Science, Kyoto University)
