NONLINEAR-THEORY OF A MICROWAVE PROBE IN A PLASMA

Electric-field and plasma perturbations near a spherical microwave pro be are investigated. The system is thoroughly studied at resonance con ditions; the electric-field structure, which is governed by a high non -uniformity of the plasma and by the nonlinear nature of the phenomena involved, is analyzed. Under these conditions, the electric field is shown to be localized near the surface of the probe. Asymptotic method s are applied to the determination of the main probe and perturbation characteristics: the depth of the field penetration into the plasma, t he mean amplitude and the change in the antenna impedance (in comparis on with the vacuum one). The main modes of probe operation, which are characterized by the stability of both the field structure and the par ameters of the processes, are investigated. A qualitative analysis is made of the behavior of the system in the phase plane. The bifurcation parameters are determined. Our main results are shown to agree well w ith the results obtained by using the asymptotic technique.