1. Center for Free-Electron Laser Science, Deutsches Elektronen Synchrotron, Notkestrasse 85, 22607 Hamburg, Germany
2. Collaborative Innovation Center for IFSA, School of Physics and Astronomy, Shanghai Jiao Tong University, 200240 Shanghai, China
3. Department of Physics and The Hamburg Centre for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany