Revisiting the Anomalous rf Field Penetration into a Warm Plasma
Authors: Igor D. Kaganovich, Oleg V. Polomarov, and Constantine E. Theodosiou
Date of PPPL Report: June 2005
Accepted for publication in: IEEE Transactions on Plasma Science: Special Issue — Nonlocal, Collisionless Electron Transport in Plasmas – June 2006
Presented at the Nonlocal, Collisionless Phenomena in Plasmas Conference, 2–4 August 2005, at the Princeton Plasma Physics Laboratory, Princeton, New Jersey.
Radio-frequency [rf] waves do not penetrate into a plasma and are damped within it. The electric field of the wave and plasma current are concentrated near the plasma boundary in a skin layer. Electrons can transport the plasma current away from the skin layer due to their thermal motion. As a result, the width of the skin layer increases when electron temperature effects are taken into account. This phenomenon is called anomalous skin effect. The anomalous penetration of the rf electric field occurs not only for transversely propagating to the plasma boundary wave (inductively coupled plasmas) but also for the wave propagating along the plasma boundary (capacitively coupled plasmas). Such anomalous penetration of the rf field modifies the structure of the capacitive sheath. Recent advances in the nonlinear, non-local theory of the capacitive sheath are reported. It is shown that separating the electric field profile into exponential and non-exponential parts yields an efficient qualitative and quantitative description of the anomalous skin effect in both inductively and capacitively coupled plasma.