1. Hitachi Ltd., Energy Research Laboratory, 2-1, Omika-cho 7-chome Hitachi-shi, Ibaraki-ken, 319-12 Japan
2. Japan Atomic Energy Research Institute Naka Fusion Research Establishment, Naka-machi, Naka-gun Ibaraki-ken 311-01, Japan
3. Japan Atomic Energy Research Institute Tokai Research Establishment, Tokai-mura, Naka-gun, Ibaraki-ken, 319-11, Japan