Observation of nonlinear Landau damping of electrostatic waves in an electron beam-plasma system, 3

The nonlinear Landau damping and growth of electrostatic waves in an electron beam-plasma system in a magnetic field have been observed experimentally. The space charge waves of the beam decay nonlinearly into the Trivelpiece-Gould mode, satisfying the resonant condition ω0 - ω1 - (k sub(parallel)0 - k sub(parallel)1)v sub(parallel) = ωsub(c) (v sub(parallel) is the parallel velocity of plasma electrons). This nonresonant decay is due to the nonlinear interaction of two waves with the plasma electrons. The decay wave can be amplified exponentially by increasing the amplitude of the pump wave. Similarly, an externally launched small amplitude test wave, having the same frequency as the decay wave, can be amplified at the comparable rate. The nonlinear Landau damping coupling coefficient measured experimentally is compared with theory. The electron heating due to this nonresonant decay has also been observed experimentally. (author)