1. Sorbonne Universités, UPMC Univ. Paris 06, UMR 7588, CNRS, INSP, F-75005, Paris, France
2. LULI, École Polytechnique, CNRS, CEA, UPMC, route de Saclay, 91128 Palaiseau, France
3. Lawrence Livermore National Laboratory, Livermore, California 94551, USA
4. LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
5. Deptartment of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
6. Univ. Bordeaux, CNRS, CEA, CELIA (Centre Lasers Intenses et Applications), UMR 5107, F-33405 Talence, France
7. Instituto Superior Técnico, Av Rovisco Pais 1, 1049-001 Lisboa, Portugal
8. European XFEL GmbH, Notkestrasse 85, 22607 Hamburg, Germany
9. Institute for Material Dynamics at Extreme Conditions University of California, Berkeley 94720-7300, USA