1. Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland
2. Department of Physics, University of Tartu, EE-50411 Tartu, Estonia
3. European XFEL, Holzkoppel 4, DE-22869 Schenefeld, Germany
4. Division of Synchrotron Radiation Research, Lund University, Box 118, SE-22100 Lund, Sweden