1. National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292, Japan
2. Laboratorio Nacional de Fusión, CIEMAT, Av. Complutense 40, Madrid 28040, Spain
3. Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, USA
4. Institute of Physics, Opole University, ul. Oleska 48, Opole 45-052, Poland