1. Japan Atomic Energy Research Institute, Mukoyama 801-1, Naka-machi, Naka-gun, Ibarak-ken, 311-0193 Japan, enoedam@fusion.naka.jaeri.go.jp
2. the University of Tokyo, Tokyo, Japan
3. Kyushu University, Fukuoka, Japan
4. Tohoku University, Sendai, Japan
5. Institute of Advanced Energy, Kyoto University, Uji, Japan
6. National Institute of Fusion Science, Toki, Japan