TY - JOUR AU - Rauer, Patrick AU - Bahns, Immo AU - Friedrich, Bertram AU - Casalbuoni, Sara AU - Di Felice, Massimiliano AU - Dommach, Martin AU - Freijo Martin, Idoia AU - Freund, Wolfgang AU - Grünert, Jan AU - Guetg, Marc AU - Karpics, Ivars AU - Karabekyan, Suren AU - Koch, Andreas AU - Kujala, Naresh AU - La Civita, Daniele AU - Liu, Jia AU - Maltezopoulos, Theophilos AU - Makita, Mikako AU - Mayet, Frank AU - Müller, Lukas AU - Rio, Benoit AU - Samoylova, Liubov AU - Schmidtchen, Silja AU - Scholz, Matthias AU - Silenzi, Alessandro AU - Strauch, Vivienne AU - Thoden, Daniel AU - Wohlenberg, Torsten AU - Vannoni, Maurizio AU - Yang, Fan AU - Decking, Winfried AU - Rossbach, Joerg AU - Sinn, Harald TI - Lasing of a cavity-based X-ray source JO - Nature VL - - SN - 0028-0836 CY - London [u.a.] PB - Nature Publ. Group M1 - PUBDB-2025-02445 SP - - PY - 2026 AB - Cavity-based X-ray Free Electron Lasers (CBXFELs) promise to transform thefield of hard X-ray science by delivering laser-like radiation with exceptional bril-liance, stability, and full three-dimensional coherence. At the European XFEL,we have constructed a proof-of-concept CBXFEL featuring a 133 m round-triphard X-ray cavity using diamond Bragg crystals. Here, we report the first las-ing with multi-pass gain in an X-ray cavity, marking a major milestone for thefield. Our results establish the feasibility of CBXFELs and open the door tonext-generation X-ray sources with unprecedented spectral purity and stability. LB - PUB:(DE-HGF)16 DO - DOI:10.1038/s41586-025-10025-x UR - https://bib-pubdb1.desy.de/record/633844 ER -