  A novel parallel plate model is proposed that divided the electron cloud into
three parts at saturation, and it is studied in detail using both an analytical
approach and PIC (Particle In Cell) code simulations. As one part of the
electron cloud, ribbons modes are suggested by tracking the trajectory of
individual particle, and the aim of this mode form is to simplify the progress
of multipacting effect in the parallel plate so as to be eliminated by
optimizing RF parameters. The micro-pulse electron gun (MPG) has demonstrated
the potential to address the need for high peak and average current electron
beams, hence studying the multipacting in MPG is essential. On the basis of
multipacting studying in the parallel plate, it is clear that increasing the
cavity voltage is of interest in yielding high quality beams in the gun.
