Abstract
The free-electron laser (FEL) community is interested in taking full advantage of the high-repetition-rates of FELs run by superconducting machines while maintaining the spectral properties achieved with external seeding techniques. Since the feasibility of seed lasers operating at a repetition-rate of MHz and with sufficient energy in a useful wavelength range, such as the ultraviolet (UV) range is challenging, a seeded oscillator-amplifier scheme is proposed instead for generation of fully coherent and high-repetition-rate radiation. The process is triggered by an external seed laser while an optical feedback system feeds the radiation back to the entrance of the modulator where it overlaps with the next electron bunch. Downstream from the feedback system, the electron bunches are then used for harmonic generation. We discuss the optimization of dedicated simulations and we investigate the stability of this scheme with numerical simulations. As a result, we address the control of the reflectivity of the resonator as a key parameter to achieve a stable HGHG seeded radiation. Finally, we show the impact of the power fluctuations in the oscillator on the bunching amplitude with analytical and simulated results. The output FEL radiation wavelengths considered are 4.167 nm and 60 nm.
Highlights
Cavity-based free-electron laser (FEL) are a well-established technology for generation of radiation in a wide range of wavelengths
A regenerative amplifier free electron lasers (RAFELs) requires only a few passes to reach saturation and the requirements on reflectivity are relaxed since it is a high-gain FEL and it consists of a low Q resonator
The repetitionrate of FLASH of 1 MHz would require a cavity of 300 m roundtrip length, while for the 4.5 MHz of the European XFEL this would be reduced to 66 m
Summary
Cavity-based FELs are a well-established technology for generation of radiation in a wide range of wavelengths. A RAFEL requires only a few passes to reach saturation and the requirements on reflectivity are relaxed since it is a high-gain FEL and it consists of a low Q resonator Another concept that is under investigation is the FEL oscillator (FELO) in the x-ray wavelength range and down to 0.1 nm [13,14,15] as a direct source of radiation. The requirements for tunable sources with tens of μJ of pulse energy, excellent stability, less than 1% rms energy fluctuations and wavelength stability below 1% rms with respect to the spectral bandwidth, make these lasers being considered as beyond the state of the art This scheme is proposed as an alternative solution for generation of high-repetition-rate seeded FEL radiation. The simulation results here are more detailed and in addition, the optimization of the simulations is discussed and the stability of this scheme is investigated This approach overcomes the limitation of requiring high-repetition-rate seed lasers. The repetitionrate of FLASH of 1 MHz would require a cavity of 300 m roundtrip length, while for the 4.5 MHz of the European XFEL this would be reduced to 66 m
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
