NONLINEAR INTERACTION OF AN ENVELOPING ELECTRON BEAM WITH A SURFACE PLASMA WAVE.

Numerical methods are used to investigate the nonlinear dynamics of a surface wave excited by an electron beam moving around a cylindrical or flat plasma surface. The mechanism which leads to saturation of the instability is the trapping of the beam particles by the wave field. The time evolution and the maximum value of the wave amplitude and the fraction of the beam energy which is transferred to the field are determined as functions of the plasma and beam thicknesses. The phase mixing of the trapped particles which results from the pronounced spatial inhomogeneity of the wave field causes the wave amplitude to increase monotonically to its maximum steady-state value.