1. Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, Hamburg 22607, Germany
2. Faculty of Electrical Engineering, Helmut Schmidt University, Holstenhofweg 85, Hamburg 22043, Germany
3. Department of Physics, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom
4. The Hamburg Centre for Ultrafast Imaging CUI, Luruper Chaussee 149, Hamburg 22761, Germany