High Repetition Rate and Coherent Free-Electron Laser Oscillator in the Tender X-ray Range Tailored for Linear Spectroscopy

Fine time-resolved analysis of matter—that is, spectroscopy and photon scattering—in the linear response regime requires fs-scale pulsed, high repetition rate, fully coherent X-ray sources. A seeded Free-Electron Laser, driven by a linac based on Super Conducting cavities, generating 108–1010 coherent photons at 2–5 keV with 0.2–1 MHz of repetition rate, can address this need. The scheme proposed is a Free-Electron Laser Oscillator at 3 keV, working with a cavity based on X-ray mirrors. The whole chain of the X-ray generation is here described by means of start-to-end simulations.