COMPARATIVE STUDY BETWEEN KINETIC AND THERMODYNAMIC CALCULATION OF COMPOSITION IN SF6 PLASMAS

International audienceIn this paper we compare the compositions calculated in chemical equilibrium for an SF6 plasma at atmospheric pressure, in the multi-temperature model and using kinetics (33 reactions involving 18 species). The ratio of the electron temperature Te to that of heavy species Th was calculated as a function of electron density and an intermediate temperature T* between Te and Th was introduced to cope with the relationship kf (T*)/kr(T*) = KX(T*) where kf and kr are the reaction rate coefficients (forward and reverse) and KX the equilibrium constant. The main difference between equilibrium and kinetic calculations lies in the densities of S+, S2+, SF+, F− and S− species between 2,000 and 6,000 K. The multi-temperature method gives results very different from those of the kinetic calculations even when the charge loss reactions are neglected. This is in contrast to what happens with H2 or N2