1. Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Krakow, Poland
2. CCFE, Culham Science Centre, Abingdon OX14 3DB, United Kingdom
3. Istituto di Fisica del Plasma “P. Caldirola,” Milano, Italy
4. Department of Physics and Astronomy, Uppsala University, Sweden
5. IAP, National Institute for Laser Plasma and Radiation Physics, Bucharest, Romania