Experimental study of the nonlinear interaction between a warm electron beam and a single wave

Abstract

We give a brief summary of an experimental observation of wave growth and saturation in a traveling wave tube modified so that a warm electron beam interacts with a single wave on the slow wave structure. This system has essentially the same physics as a weak warm beam plasma system but has a much lower inherent noise level. The growth rate and saturation level of the unstable wave are studied as a function of the beam parameters. We observe that, in the weak warm beam limit, the time-averaged beam distribution function develops a localized plateau. The electric field at saturation scales as the square of the linear growth rate of the wave. When the growth is stronger, the entire distribution function can become distorted.