1. European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
2. SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
3. Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305, USA
4. Atomic Weapons Establishment, Aldermaston, Reading, Berkshire RG7 4PR, United Kingdom
5. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
6. Centre for Fusion, Space & Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
7. Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
8. Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
9. Dipartimento di Fisica, Universita di Trento, via Sommarive 14, Povo 38123, TN, Italy
10. School of Mathematics and Physics, Queen’s University Belfast, University Road, BT7 1NN Belfast, United Kingdom
11. Universität Rostock, Institut für Physik, Albert-Einstein-Straße 23-24, 18051 Rostock, Germany
12. Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
13. Helmholtz-Institut Jena, Fröbelstieg 3, 07743 Jena, Germany
14. Physics Department, University of Nevada at Reno, Reno, Nevada 89506, USA