1. Institute for Nuclear Research, Prospekt Nauky 47, Kyiv 03680, Ukraine
2. Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85748 Garching, D-17489 Greifswald, Germany
3. National Institute for Fusion Science Oroshi-cho 322-6, Toki, 509-5292, Japan