1 School of Mathematics and Physics, Queen’s University Belfast, Belfast, UK
2 Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, UK
3 Gérard Mourou Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI, USA
4 SLAC National Accelerator Laboratory, Menlo Park, CA, USA
5 Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada
6 The John Adams Institute for Accelerator Science, Imperial College London, London, UK
7 ELI Beamlines Centre, Institute of Physics, Czech Academy of Sciences, Dolní Břežany, Czech Republic
8 Department of Applied Physics, Stanford University, Stanford, CA, USA
9 Department of Physics, SUPA, University of Strathclyde, Glasgow, UK
10 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic
11 Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
12 Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany