Shamrai K. Theory of radio-frequency power absorption in helicon plasmas.

The thesis deals with theoretical study of linear processes of electromagnetic wave excitation and rf power absorption, and with some nonlinear processes in plasmas of helicon sources of three different types. For the source with an internal antenna, resonance character of the power absorption on quasi-helicon modes is ascertained. For the source with an external antennas, the efficient rf power absorption is found to arise from a cooperative mechanism of linear mode conversion of helicon waves into quasi-electrostatic waves; resonance and anti-resonance properties of the source excitation are ascertained; and spatial characteristics of the absorption and dependences of plasma impedance on antenna design and various physical parameters are determined. For the source with a planar antenna, characteristics of excited electromagnetic waves and dependences of the rf power absorption on physical and geometrical parameters are ascertained. On basis of the power balance in helicon discharges, the reasons forabrupt density jumps at continuous variation of various external parameters are clarified. For conditions of helicon plasmas, linear and parametric mechanisms of ion acoustic wave excitation, ponderomotive phenomena, and the process of stochastic electron acceleration are analyzed. The results are compared with experimental data from various sources.