Efficiency enhancement in a two-stream free electron laser with a helical wiggler

Abstract

Efficiency enhancement in a two-stream Free Electron Laser (FEL) by a tapered wiggler prior to saturation regime is treated. Wave-particle interaction is described by a set of nonlinear coupled differential equations in 1D approximation. The scaled vector potential correspond to the out-put power is plotted versus scaled axial distance. It was found, that, the output power was enhanced to a level of almost 51.79%. Bunching parameter was plotted and compared with the case of un-tapered wiggler field. It is found, that, bunching parameter increased when tapering of the wiggler is executed. Bunching of the electrons in a phase space is shown, too.