Spatial Growth of Waves in a Beam-Plasma System

An experiment on spatially growing electron plasma waves in a beam-plasma system is described. The properties of the electron beam and the plasma separately are known from accurate, independent measurements. Using a “test wave” technique, the dispersion of the waves in the presence and absence of the beam and their linear growth rate as a function of frequency were measured. The growth of a spectrum of waves from broad-band noise and the termination of the growth due to nonlinear effects were observed.