1. Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580, Japan
2. Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580, Japan
3. National Institute for Fusion Science, Toki 509-5292, Japan
4. Teikyo University, Omuta 835-8580, Japan
5. Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga 816-8580, Japan
6. Faculty of Arts and Science, Kyushu University, Fukuoka 819-0395, Japan
7. Japan Atomic Energy Agency, Rokkasho 039-3212, Japan