1. Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
2. Princeton Plasma Physics Laboratory, P.O.Box 451, Princeton, NJ 08543, USA
3. Tritium Laboratory, Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany
4. EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon Oxon, OX14 3DB, UK