1. Chalmers University of Technology Institute for Electromagnetic Field Theory and Plasma Physics EURATOM/NFR Association, S-41296 Göteborg, Sweden
2. Royal Institute of Technology, AIfvén Laboratory Department of Fusion Plasma Physics, S-100 44 Stockholm, Sweden
3. Studsvik Nuclear, EURATOM/NFR Association S-61182 Nykoping, Sweden and Uppsala University, Department of Technology Theoretical Electrotechnics Group, Box 534, S-75121 Uppsala, Sweden