1. FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, member of Trilateral Euregio Cluster, PO Box 1207, 3430 BE Nieuwegein, The Netherlands
2. Phystex, The Netherlands and A. F. Ioffe Physical-Technical Institute, Polytechnicheskaya 26, 194021 St. Petersburg, Russia