Calculation of a two-temperature plasma composition: bases and application to SF6

In this paper we discuss the use of generalized Saha and Guldberg-Waage equations for calculating the composition of a two-temperature SF 6 plasma in a pressure range 0.1-1.6 MPa, for an electron temperature in the range 300-20 000 K. We compare two sets of two-temperature laws and we recommend the expressions proposed by the team from Eindhoven. Furthermore, knowing the great influence of the choice of the excitation temperature on the plasma composition, we propose, on the basis of a chemical kinetics approach, a simple general relation allowing the calculation of this temperature versus the electron temperature, the heavy particle temperature and the electron number density. The application of these relations to a real case of a two-temperature SF 6 arc plasma gives a realistic radial profile of the electron number density.