Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany, Institute of Physics Belgrade, Pregrevica 118, 11080 Belgrade, Serbia, Vinca Institute of Nuclear Sciences, Belgrade, Serbia, Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, D-22607 Hamburg, Germany, Department of Physics, S. P. Pune University, Pune, India, SLAC National Accelerator Laboratory, Menlo Park, California, USA, Elettra – Sincrotrone Trieste SCpA, 34149 Basovizza, Trieste, Italy, Helmholtz-Zentrum DresdenRossendorf (HZDR), Bautzner Landstraße 400, 01328 Dresden, Germany, European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany, German Aerospace Center (DLR), Institute of Optical Sensor Systems, Rutherfordstraße 2, 12489 Berlin, Germany, and Institute of Optics and Atomic Physics, Technical University of Berlin, Strasse des 17 Juni 135, 10623 Berlin, Germany. *Correspondence e-mail: nikola.stojanovic@desy.de