Spatially Growing Plasma Waves and Their Nonlinear Effects by Beam Modulation

Spatial behaviours of electron plasma waves due to beam-plasma instability have been studied with a waveguide antenna which did not give any disturbance on the plasma. The observed growth rates are in agreement with those obtained by linear theory considering the plasma temperature. The criteria of validity of linear theory and the saturation of wave amplitude are also discussed. The electron beam modulated with microwave frequency gives rise to a strong electron plasma wave which shows the amplitude oscillation phenomena. The experimental value of its wave length agrees with the theoretical one on the order of magnitude. The modulation was applied to the beam. The intensity of waves showed a dip when the modulation frequency was varied near the receiving frequency.