1. Max-Born-Institut, Max-Born-Str. 2a, 12489 Berlin, Germany
2. XFEL GmbH, Notkestr. 85, 22607 Hamburg, Germany
3. Vavilov State Optical Institut, Birzhevaya line 12, 199064 St. Petersburg, Russia
4. St. Petersburg University, 199064 St. Petersburg, University emb.6, Russia
5. Center of Relativistic Laser Science, Institute for Basic Science, Gwangju 500-712, South Korea
6. Technical University Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
7. ELI-DC International Association AISBL, c/o DESY – StandortZeuthen, Platanenallee 6, 15738 Zeuthen, Germany