Temperature determination for arcs in sulphur hexafluoride accounting for demixing

Methods of temperature determination for arcs in sulphur hexafluoride (SF6) are presented for the temperature range from 9000 to 20000K. Temperatures are derived from combinations of measured S I, S II, F I and F II absolute line intensities and computed equilibrium plasma composition data by means of iterative procedures. Demixing effects are accounted for as both the temperature and the fluorine to sulphur concentration ratio M are determined from the measured data. The methods are applied to experimental line intensity data obtained from steady-state wall-stabilised arcs in SF6at atmospheric pressure, at axis temperatures of about 15000K. Simple approximation formulae are given for calculating the various partition functions at a pressure of p=1 bar for M=6, 12, 24 and 48; and at p=2, 4, 8 and 16 bar for M=6.