Nonlinear Wave Phenomena in an Electron-Beam Plasma

Abstract
An experiment has been carried out to investigate one-dimensional nonlinear evolution and formation of the localized structure of unstable waves in an electron-beam plasma. The plasma system is linearly unstable against electrostatic perturbations of frequencies lower than the critical frequency ω_cr (=ω_pe, plasma frequency), but is stabilized in its nonlinear stage by generating wave packets irregularly. The amplitude of each wave packet never grows infinitely. The average time width of the packets is inversely proportional to the linear growth rate γ, where γ α (nb/n0)^1/3ω_pe (nb: beam density, n0 : plasma density). The system is also unstable for an external rf-burst with a narrow time-width, and then finally becomes stable by the emission of a series of burst waves. The number of emitted bursts increases with the beam density.