1. CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
2. Laboratoire J. A. Dieudonne, UMR 7351, Universite Nice Sophia Antipolis, 06108 Nice Cedex 02, France
3. Institute for Plasma Research (IPR), Near Indira Bridge, Bhat, Gandhinagar 382 428, Gujarat, India