Optimization and stability analysis of the cascaded EEHG-HGHG free-electron laser

TL;DR

This paper designs and optimizes a cascaded EEHG-HGHG free-electron laser configuration for generating 1 nm wavelength FEL pulses, analyzing its stability and sensitivity to timing jitter through numerical simulations.

Contribution

It presents a novel optimized cascaded EEHG-HGHG scheme for soft X-ray FELs and systematically analyzes the impact of timing jitter on its performance.

Findings

Achieves 1 nm FEL pulses with 15 GW peak power.

Timing jitter of 3 fs causes 29.16% fluctuation in pulse energy.

Demonstrates the scheme's potential for stable, high-power soft X-ray generation.

Abstract

X-ray free-electron lasers (XFELs) are powerful tools to explore and study nature for achieving remarkable advances. Generally, seeded FELs are ideal sources for supplying full coherent soft x-ray pulses. Benefiting from the high-frequency up-conversion efficiency, the cascading configuration with echo-enabled harmonic generation (EEHG) and high-gain harmonic generation (HGHG) holds promising prospects for generating full coherent radiation at 1 nm wavelength. In this paper, we design and optimize EEHG-HGHG configuration using parameters of Shanghai High-Repetition-Rate XFEL and Extreme Light Facility. In addition, we systematically analyze the effect of relative timing jitter on the output FEL performance based on various start-to-end electron beams. The intensive numerical simulations show that the cascaded EEHG-HGHG scheme can achieve 1 nm FEL pulses with peak power up to 15 GW. Further sensitivity analysis indicates that the relative timing jitter between the electron beam and seed laser has a significant impact on the FEL performance. The RMS timing jitter of 3 fs can lead to the final output pulse energy fluctuations of 29.16%.