Meshing Guidelines
When simulating a CCP discharge it is necessary to well resolve the plasma sheath region. A poorly resolved sheath makes the convergence difficult and can lead to physically incorrect results. Quantities that clearly show a poor mesh resolution are the electron temperature and the power absorbed by the electrons. A visual inspection to these quantities is always a good practice and can be done by plotting the results while solving to identify problems at an early stage.
Industrial CCP reactors have very large aspect ratios with the gap between electrodes being about 3 cm and the reactors radius about 30 cm. Using an unstructured mesh (with the same scale in the r and z directions) in such reactor can lead to a very large number of degrees of freedom because the axial direction needs to be very well resolved. The excessive meshing in the radial direction can be avoided by uncoupling the resolution in the radial and axial directions with the use of a mapped mesh. When using a mapped mesh it is important to convert the mesh (use the Convert feature in the mesh node) to avoid spurious patterns in the electron temperature.