Transverse dynamics of а surface wave excited by а wide electron beam.

A non-stationary two-dimensional theory of interaction of a surface wave and a wide sheet electron beam is developed. This theory is used for studying the problem of mode competition and non-coherent transverse distribution of the microwave field in the surface-wave generation process. According to numerical simulations based on a quasi-optical equation, transverse diffraction of surface wave provides stable stationary generation in a wide range of beam widths and currents. The developed theory can be applied both to surface-wave oscillator and to a Smith-Purcell free-electron laser, where surface pi-type eigenmode excitation provides the beam bunching and enhances the power of the Smith-Purcell radiation at the frequency harmonics of the surface wave. [ABSTRACT FROM AUTHOR]