Application of Coupling Resonance to Electron-Beam Conditioning for Free-Electron Lasers

Abstract

Coupling resonances can be used to control the phase–space configuration of a charged-particle beam. Here we study a compact storage ring, which enables one to achieve a wide variety of emittance manipulations. A simple analytic model and numerical examples are given to demonstrate the fundamental features of the coupled beam motion near resonance. As a possible application of the present idea, free-electron lasers (FELs) are studied. It is shown that, by employing a nonlinear coupling resonance, the phase–space distribution of an electron beam can be optimized for high FEL gain. A three-dimensional simulation code is used to confirm that the “conditioned” electron beam from the coupling storage ring improves the performance of the subsequent FEL system.