Optical and Electron Beam Requirements for an Optical Undulator FEL

Abstract

Counterpropagating strong electromagnetic radiation is interesting as a short-period “optical undulator”. This work presents a basic discussion concerning the requirement for electron beam quality in an optical undulator FEL. In the Compton and cold electron beam regime, the emittance ε of the electron beam is limited to be γε<0.16\\frac{(1+K^{2} / 2)^{3/2}}{\\sqrt{N}K}λU at the beam waist of the optical undulator of which the field is produced by focusing electromagnetic radiation such as a high-power molecular laser. Further discussion suggests that a high-quality, long-pulsed electron beam from UCSB's accelerator might promise FEL operation in the ultraviolet or shorter wavelength regions using a high-power CO2 laser undulator.