1. National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan
2. Interdisciplinary school of Engineering and science, Kyushu University, 6-1 Kasuga-kouen, Kasuga 816-8580, Japan
3. Nippon Kucho Service Co. Ltd., 239-2 Terugaoka, Meitou-ku, Nagoya 465-0042, Japan