Widely tunable two-color x-ray free-electron laser pulses

We demonstrate the generation of widely tunable two-color x-ray free-electron laser (FEL) pulses at SwissFEL. In a split-undulator configuration, each color is produced in different undulator section, and chicane between two sections allows for variable time separation up to 500 fs. show an unprecedented photon energy ratio colors about three (350 915 eV), with individual pulse having peak power few gigawatts duration down femtosecond level. Moreover, we reduction required length via optical klystron mechanism time-resolved diagnostics FEL utilizing same beam setup as generation. The unique combination pair offers opportunities study ultrafast x-ray-induced transfer relaxation processes physics, chemistry, biology.Received 21 February 2022Accepted 4 April 2022DOI:https://doi.org/10.1103/PhysRevResearch.4.L022025Published by American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution this work must maintain attribution author(s) published article's title, journal citation, DOI.Published SocietyPhysics Subject Headings (PhySH)Research AreasBeam diagnosticsX-ray lasersPhysical SystemsFree-electron lasersLinear acceleratorsAccelerators & BeamsAtomic, Molecular OpticalParticles Fields