Coherent, high repetition rate tender x-ray free-electron laser seeded by an extreme ultra-violet free-electron laser oscillator

A seeded FEL driven by a linac based on super conducting cavities, generating 10 8 –10 10 coherent photons per shot at 2–5 keV with 0.2–1 MHz of repetition rate, can address the need of a source devoted to fine analysis of matter using the linear spectroscopy technique. The seeding scheme described hereafter is a multi-stage cascade upshifting the radiation frequency by a factor 20–40. The x-ray range can be achieved with a seed constituted by a...