Geodesic acoustic modes (GAMs) in the multi-ion system are investigated. It was found that the high-frequency branch decreases with increase in effective ion mass. The low-frequency branch (ion sound wave, ISW) of the damping rate also becomes small. The ratio between the damping rate of GAM and ISW is found to become order of unity in the region of q < 4 (q is safety factor).
2008 by The Japan Society of Plasma Science and Nuclear Fusion Research