Free-Electron-Laser Model without the Slowly-Varying-Envelope Approximation

A mathematical model is presented which describes the evolution of electromagnetic radiation in a free-electron laser (FEL), without any stringent assumptions regarding the envelope of the radiation pulse. The derived set of equations is nearly identical to the traditional set, which needed the assumption of a slowly varying radiation amplitude and phase. Although rapid variations in the radiation envelope do have influence on the dynamics of the electrons, ignoring this fact does not cause excessive errors. Consequently, it is concluded that the region of validity of the traditional FEL equations is much larger than has been realized sor far

The Effects of Slippage and Diffraction in Long-Wavelength Operation of a Free-Electron Laser

The Free-Electron Laser user facility FELIX produces picosecond optical pulses in the wavelength range of 5-110 mu m. The proposed installation of a new undulator with a larger magnetic period would allow extension towards considerably longer wavelengths. This would result in the production of extremely short, far-infrared pulses, with a duration of a single optical period or even less. In order to investigate the pulse propagation for free-electron lasers operating in the long wavelength limit, a three-dimensional simulation code was developed. Using the FELIX parameters, with the addition of a long-period undulator, the effects of slippage, diffraction losses, changes in the filling factor, as well as the effects of the optical cavity geometry were studied for wavelengths up to 300 mu m, with electron pulses in the ps regime. It is shown that slippage effects are less restrictive for long wavelength operation than the increasing losses due to optical beam beam action

Influence of the Radial Mode Structure on the Losses in the Felix Hole-Coupled Resonators

FELIX uses a hole in one of the optical cavity mirrors as a convenient, broadband method of outcoupling. In this contribution we present a preliminary study of the mode structure in the FELIX optical resonators, and compare the results with a computer analysis