1. CEA, IRFM, 13108 St. Paul-Lez-Durance, France
2. Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
3. CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
4. Institute of Plasma Physics ASCR, Za Slovankou 1782/3, 182 00 Prague 8, Czech Republic