Statement on PETRA IV – The ultimate 4D X-ray Microscope of the Deutsches Elektronen-Synchrotron (DESY), March 2026

At the request of the Federal Ministry of Research, Technology and Space (BMFTR), the German Science and Humanities Council (WR) carried out a science-driven assessment of projects for large research infrastructures as part of a national prioritisation process. For this purpose, a committee was set up. The aim was to recommend the most promising projects to the BMFTR for inclusion on a shortlist; nine projects were ultimately selected, including PETRA IV – The ultimate 4D X-ray Microscope. At the same time, the BMFTR asked the WR to individually evaluate the projects on the shortlist to ensure that they will be established in the best possible way and that the recommendations from the assessment of the prioritisation phase are followed up. For the evaluation of PETRA IV, the committee set up a working group which wrote an evaluation report. On the basis of this evaluation report, the committee adopted the present scientific policy statement.