1. State Key Laboratory of Particle Detection and Electronics, Department of Modern Physics, University of Science and Technology of China, 230026 Hefei, China
2. School of Physics and Information Technology, Shaanxi Normal University, 710119 Xian, China
3. Max Planck Institute for the Structure and Dynamics of Matter (MPSD), 22761 Hamburg, Germany
4. Center for Free-Electron Laser Science (CFEL), 22761 Hamburg, Germany