1. ETSI Aeronáutica y del Espacio, Universidad Politécnica de Madrid, 28040 Madrid, Spain
2. Centro de Laseres Pulsados, Building M5, Science Park, Calle Adaja 8, Villamayor, 37185 Salamanca, Spain
3. INFN-LNF, Via Enrico Fermi 40, 00044 Frascati, Rome, Italy
4. Department of Fundamental Physics, University of Salamanca, 37008 Salamanca, Spain
5. Princeton Plasma Physics Laboratory, 100 Stellarator Road, Princeton, NJ 08536, USA
6. Departamento de Física y Matemáticas, University of Alcalá, Plaza de San Diego s/n, 28801 Madrid, Spain