Numerical analysis and experimental investigation of discharge characteristics in a ring dielectric line surface‐wave processing plasma apparatus

Discharge characteristics in ring dielectric line surface‐wave processing plasma (RDL‐SWP) apparatus are studied both numerically and experimentally. To numerically simulate electromagnetic waves in SWP apparatus with a cylindrical discharge chamber such as RDL‐SWP apparatus, a three‐dimensional computer code is developed, employing Cartesian coordinates to allow simulation of both the plasma and rectangular waveguide connected to the chamber. The finite difference time domain (FDTD) method is the basis of the numerical code. Electron density and temperature profiles are measured experimentally in Ar plasma using a movable single probe and the optical emission patterns are studied. It is found that peaks in the electron density profiles coincide with intense optical emissions. For profiles across bulk plasmas with densities higher than cut‐off, diffusion effects are found to be more dominant than localized plasma effects produced by surface waves. In particular, by comparison of numerical and experimental results, the applicability and limitations of a plasma model in which uniform electron density is assumed are evaluated.