1. Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816
2. Graduate School of Energy Science, Kyoto University, Uji, Kyoto 611
3. Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611
4. Faculty of Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606
5. National Institute for Fusion Science, Nagoya 464-01