Optimization and stability of a high-gain harmonic generation seeded oscillator amplifier

The free-electron laser (FEL) community is interested in taking full advantage of the high-repetition-rates FELs run by superconducting machines while maintaining spectral properties achieved with external seeding techniques. Since feasibility seed lasers operating at a repetition-rate MHz and sufficient energy useful wavelength range, such as ultraviolet (UV) range challenging, seeded oscillator-amplifier scheme proposed instead for generation fully coherent high-repetition-rate radiation. process triggered an optical feedback system feeds radiation back to entrance modulator where it overlaps next electron bunch. Downstream from system, bunches are then used harmonic generation. We discuss optimization dedicated simulations we investigate stability this numerical simulations. As result, address control reflectivity resonator key parameter achieve stable HGHG Finally, show impact power fluctuations oscillator on bunching amplitude analytical simulated results. output FEL wavelengths considered 4.167 nm 60 nm.