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 coherent flash in the extreme ultraviolet range provided by an FEL oscillator operating at 12-14 nm. The whole chain of x-ray generation is described by means of start-to-end three-dimensional simulations.