PHYSICAL AND NUMERICAL VERIFICATION OF DISCHARGE CALCULATIONS

Calculations of radio frequency discharge parameters, and to a lesser extent d.c. discharge parameters, are apparently highly sensitive to t he physical model used. It is essential to use an accurate, kinetic de scription of the plasma to obtain quantitatively correct results. Nume rical schemes also introduce possible errors, which must be tested for both versus alternative formulations and versus simple physical model s. This testing process is carefully considered in this paper. Within kinetic models a number of options exist, having different capabilitie s, the implications of which are examined here. Particle simulations a re discussed and ''mesh-based'' kinetic calculations are considered in detail. A mesh-based kinetic model is presented which closely replica tes the physical processes taking place and is consequently very effic ient and accurate. Its accuracy is nevertheless limited by the resolut ion of the mesh. Ways to improve accuracy, and their effects, are pres ented. Cross-checking of various different numerical formulations of t he calculations performed here shows that the results of each are esse ntially the same. Physical reasoning and simple estimates of discharge parameters are used to further substantiate the predictions for a par ticular discharge, and the processes taking place in an rf discharge i n helium are described in detail. It is argued that this sort of proce dure should be part of any numerical model, but especially in complex systems such as plasmas.