Abstract
Fine time-resolved analysis of matter - i.e. spectroscopy and photon scattering - in the linear response regime requires a fs-scale pulsed, high repetition rate, fully coherent X-ray source. A seeded Free-Electron Laser (FEL) driven by a Super-Conducting Linac, generating $10^{8}$-$10^{10}$ coherent photons at 2-5 keV with abou 0.5 MHz of repetition rate, can address this need. The seeding scheme proposed is the Echo-Enabled Harmonic Generation, alimented by a FEL Oscillator working at 13.6 nm with a cavity based on Mo-Si mirrors. The whole chain of the X-ray generation is here described by means of start-to-end simulations. Comparisons with the Self Amplified Spontaneus Emission and a fresh-bunch harmonic cascade performed with similar electron beams show the validity of this scheme.
Highlights
Fine time-resolved analysis of matter is currently performed with synchrotron radiation (SR) sources or with x ray free electron lasers (FELs), whose extremely brilliant pulses are able to detect matter in highly excited states dominated by non-linear response
We show the operation of a FEL in the tender X-ray range, based on enabled harmonic generation (EEHG)
A new generation accelerator complex is at the core of this coherent and compact facility dedicated and optimized to ultra-fast coherent x-ray spectroscopy and inelastic photon scattering, and to highly penetrating x-ray imaging of mesoscopic and macroscopic samples
Summary
Fine time-resolved analysis of matter is currently performed with synchrotron radiation (SR) sources or with x ray free electron lasers (FELs), whose extremely brilliant pulses are able to detect matter in highly excited states dominated by non-linear response. High gain harmonic generation (HGHG) multistage cascades [8], seeded by the harmonics of an IR laser generated in crystals [9] or in gases [10,11,12,13], have been demonstrated and applied up to few nm wavelengths [3]. Their implementation in the tender/hard x-ray range is highly demanding, while the extension to higher repetition rates, obtained by using oscillators [14] or lasers in cavity [15], has been studied sofar only theoretically. FEL oscillators [16,17,18,19,20,21] or regenerative amplifiers [22,23,24,25,26]
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