Nonlinear excitation of acoustic waves in a double plasma device

In the double plasma device, ion acoustic waves are generated when the potential difference between the two plasmas is varied as Φ0sinωt. This perturbation at first affects only the ions since the electrons are repelled from the grid that separates the two plasmas. The analysis of the ion orbits near the grid leads to a source term in Vlasov’s equation for the ion distribution function. This source and therefore the ion acoustic wave depend nonlinearly on the exciting potential. Analytic and numerical results are given which show that the nth harmonic of the wave potential is proportional to Φn0 but is independent of ω when ω≪ωpi.