1. LAPLACE, CNRS, Université de Toulouse, Toulouse, France
2. Swiss Plasma Center (SPC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
3. CEA, IRFM, F-13108 St. Paul lez Durance, France
4. CNR-Institute for Plasma Science and Technology, Bari, Italy