Quasi-Linear Saturation in Free Electron Lasers

Abstract

Saturation mechanisms of free electron lasers are investigated in the Compton regime. It is found that saturation occurs due to quasi-linear energy spreading of the electron beam in the case of multi-mode excitation. Although the energy conversion efficiency remains low even if many modes are taken into account, it can be improved to more than 50% by reaccelerating the electrons with a traveling RF wave.