National Institute for Fusion Science, Toki 509-5292, Japan author s e-mail: fujisawa@nifs.ac.jp
Department of Electronics, Nagoya University, Nagoya 464 8603, Japan author s e-mail: sasaki@nuee.nagoya-u.ac.jp
Tokai University, Hiratsuka 259-1292, Japan author s e-mail: hirose@keyaki.cc.u-tokai.ac.jp
Chubu University, Kasugai 487-8501, Japan author s e-mail: sokajima@isc.chubu.ac.jp
Nagoya University, Nagoya 464-8601, Japan author s e-mail: hori@nuee.nagoya-u.ac.jp
Nagasaki University, Nagasaki 852-8521, Japan author s e-mail: plasma@net.nagasaki-u.ac.jp
Shizuoka University, Hamamatsu 432-8561, Japan authoe s e-mail: tmnagat@ipc.shizuoka.ac.jp