Comparative Study between kinetic and thermodynamic calculation of composition in SF6 Plasmas
Résumé
For an SF6 plasma at atmospheric pressure the compositions calculated in chemical equilibrium, in the multi-temperature model and using kinetics (33 reactions involving 18 species) are compared. 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 2000 and 6000 K. The multi-temperature method gives results very different from those of the kinetic calculations even when neglecting the charge loss reactions. This is in contrast to what happens with H2 or N2.