1. Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ Scotland, United Kingdom, Department of Physics, University of Ioannina, GR-45110, Ioannina, Greece, TOPS Laser Facility, Department of Physics and Applied Physics, University of Strathclyde G4 ONG, Scotland, United Kingdom, and AWE plc., Aldermaston, Reading RG7 4PR, United Kingdom