1. Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
2. Department of Physics, University of Hamburg and the Hamburg Centre for Ultrafast Imaging, 22761 Hamburg, Germany
3. Center for Free-Electron Laser Science, DESY and The Hamburg Centre for Ultrafast Imaging, 22761 Hamburg, Germany
4. Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark