Analysis and optimization of a free-electron laser with an irregular waveguide

TL;DR

This paper develops a self-consistent reduced model of a free-electron laser with an irregular waveguide, using nonlinear dynamics and evolutionary computation to optimize waveguide profiles for enhanced efficiency.

Contribution

It introduces a generalized reduced FEL model incorporating complex electron dynamics and waveguide scattering, and applies evolutionary algorithms for waveguide optimization.

Findings

Efficiency improved by a factor of 5-6 with optimized waveguide profiles.

Optimal operation in the magnetoresonance regime enhances FEL performance.

Numerical simulations confirm the effectiveness of the optimized waveguide designs.

Abstract

Using a time-dependent approach the analysis and optimization of a planar FEL-amplifier with an axial magnetic field and an irregular waveguide is performed. By applying methods of nonlinear dynamics three-dimensional equations of motion and the excitation equation are partly integrated in an analytical way. As a result, a self-consistent reduced model of the FEL is built in special phase space. The reduced model is the generalization of the Colson-Bonifacio model and takes into account the intricate dynamics of electrons in the pump magnetic field and the intramode scattering in the irregular waveguide. The reduced model and concepts of evolutionary computation are used to find optimal waveguide profiles. The numerical simulation of the original non-simplified model is performed to check the effectiveness of found optimal profiles. The FEL parameters are chosen to be close to the parameters of the experiment (S. Cheng et al. IEEE Trans. Plasma Sci. 1996, vol. 24, p. 750), in which a sheet electron beam with the moderate thickness interacts with the TE01 mode of a rectangular waveguide. The results strongly indicate that one can improve the efficiency by a factor of five or six if the FEL operates in the magnetoresonance regime and if the irregular waveguide with the optimized profile is used.