1. National Institute of Fusion Science, Nagoya 464-01
2. Department of Electrical Engineering, Osaka Institute of Technology, Asahi-ku, Osaka 535
3. Department of Electrical Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606
4. Department of Electrical Engineering, Nagoya University, Nagoya 464-01
5. Plasma Science Center, Nagoya University, Nagoya 464-01