Impact of electron-beam energy spread on the generation of high harmonics in seeded free-electron lasers
Open Access
- 6 April 2026
- journal article
- Published by American Physical Society (APS) in Physical Review Accelerators and Beams
- Vol. 29 (4)
Abstract
In seeded free-electron lasers (FELs), harmonic up-conversion of an external seed laser can be used to generate coherent emission at short wavelengths. The harmonic generation process is sensitive to the electron beam slice energy spread, which limits the highest harmonic conversion factor. We present here an experimental study of the impact of the slice energy spread on the FEL performance in two different harmonic generation schemes: high-gain harmonic generation and echo-enabled harmonic generation (EEHG). The slice energy spread is controlled by means of a laser heater installed in the low energy region of the linear accelerator that drives the FEL. The measurements of the FEL pulse energy as a function of the electron beam slice energy spread were performed at different harmonics. Our results confirm the robustness of EEHG to the slice energy spread and open the way toward fully coherent FEL pulses in the soft x-ray domain.Keywords
Funding Information
- Elettra-Sincrotrone Trieste
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