1. Institute for Fusion Theory, Hiroshima University Higashisenda Nakaku, Hiroshima 730, Japan
2. Okayama University, Faculty of Engineering Tsushima Naka, Okayama 700, Japan
3. Japan Atomic Energy Research Institute Naka Fusion Research Establishment, Nakagun, Ibaraki 311-01, Japan
4. Kyoto University, Plasma Physics Laboratory Gokasho, Uji 611, Japan