Nonlinear features of radio-frequency sheaths and the self-consistent role of steady currents

Sheath potentials formed on the material surfaces of plasma facing components are dramatically enhanced by the application of radio-frequency (RF) power in the ion-cyclotron (IC) range of frequencies. The resulting rectified sheath potentials lead to several important effects such as the sputtering of impurities from the wall material and the formation of convective cells via steady-current systems. Analytic tools are used to describe the self-consistent enhancement of the sheath potential together with the global electromagnetic field sourced by an ICRF antenna. Nonlinear features associated with RF sheath-plasma interactions are elucidated and their importance for experimental regimes is assessed. Direct current (DC) effects are incorporated into the model and their importance in sheath regulation is highlighted.