1. SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
2. Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA
3. Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
4. Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
5. Institut für Physik und Astronomie, Universität Potsdam, 14476 Potsdam, Germany