NONLINEAR CHARACTERISTICS OF A SMITH-PURCELL FREE-ELECTRON LASER

We investigate a two-dimensional model of the Smith-Purcell free-elect ron laser composed of a parallel plate waveguide with a grating graved on one plate, and a planar relativistic electron beam is drifting at a constant distance above the metallic grating. With the aid of partic le simulation, we discuss the growth characteristics of the electromag netic wave and efficiency enhancement in energy transfer from the elec tron beam to the electromagnetic wave, allowing for the nonlinear prop erties of the electron beam. From the result of numerical simulation, even if we take into account the nonlinear properties of the electron beam, the beam-wave synchronism is found to be kept for a longer time by gradually increasing the slot width of the metallic grating in acco rdance with the decrease in the drift velocity of the electron beam, l eading to the sufficient efficiency enhancement in energy transfer. (C ) 1998 Scripta Technica.