1. National Institute for Fusion Science, Toki 509-5292, Japan
2. Kyoto University, Kyoto 6060-8501, Japan
3. Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, Anhui, 230031, China +86-551-5591397
4. Tohoku University, Sendai 980, Japan
5. Kyushu Tokai University, Kumamoto 862, Japan
6. Toyama University, Toyama 930-8555, Japan
7. University of Tokyo, Tokyo 113, Japan
8. Kyushu University, Fukuoka 812-8581, Japan