1. Japan Atomic Energy Research Institute Naka Fusion Research Establishment 801-1 Mukoyama, Naka-machi, Naka-gun, Ibaraki-ken 311-0193, Japan
2. Research Organization for Information Science & Technology 2-4 Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki-ken 319-1106, Japan