1. York Plasma Institute, The University of York, York YO10 5DQ, United Kingdom
2. Central Laser Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, United Kingdom
3. Laboratoire de Physique de Gaz et des Plasmas, UMR 8578 CNRS, Orsay, France
4. LASERIX, Centre Laser de I'Universite Paris Sud, Federation Lumiere-Matiere, FR2764, 91405 Orsay Cedex, France
5. Centro de Fisica de Plasmas, Instituto Superior Técnico, Av. Rovisco pais 1, 1049-001, Lisbon, Portugal