Experimental determination of the nonlinear interaction in a one dimensional beam‐plasma system

Recent theories have shown that the instability driven by a cold, weak electron beam in a one‐dimensional plasma is stabilized when the unstable wave grows to an amplitude sufficient to trap the electron beam. Quantitative measurements of the instability confirm every prediction of the theory: the maximum wave amplitude, monochromaticity of the unstable mode, harmonic content of the mode, and wavelength of the slow oscillation in wave amplitude. The electron beam goes through the same patterns in phase space and time‐averaged f(v) as predicted. Both scaling and absolute magnitudes agree with theory.