1. Faculty and Graduate School of Engineering, Kyushu University: Moto-oka 744, Nishi-ku, Fukuoka 819-0395, Japan
2. Graduate School of Engineering, Kyushu University: Moto-oka 744, Nishi-ku, Fukuoka 819-0395, Japan
3. National Institute for Fusion Science, Oroshi-cho 322-6, Toki-city, Gifu 509-5292, Japan
4. Faculty of Engineering, Nagoya University, Furo-cho, Chigusa-ku, Nagoya 464-8601, Japan