Change of SF₆plasma properties by the inclusion of N₂at different admixture ratios

An inductively coupled plasma (ICP) model is developed/solved to investigate SF 6 -N 2 plasma properties at different gas ratios. The simulating work is divided into two parts: the thermophysical properties of the SF 6 -N 2 mixture at different ratios are calculated in the first part and the results thus obtained are used in the second part to predict plasma properties for the corresponding ratios of gas flow. The electrical conductivity does not vary significantly even at a 70% admixture ratio of N 2 . However, if we look from the other side, it is found that the electrical conductivity of the N 2 gas increases drastically to the level of pure SF 6 gas by a small percentage admixture of SF 6 with N 2 . In addition, the thermal conductivity has an additional peak centred at around 7000 K by the N 2 inclusion with SF 6 at any ratio. Other material properties (viscosity, density, enthalpy and specific heat at constant pressure) of SF 6 are found to vary considerably with the nitrogen admixture ratio of 30% or above. From the properties predicted by the rf-ICP model, it is realized that plasma properties of a SF 6 -N 2 mixture for an admixture ratio of N 2 up to about 20% are comparable with those for the pure SF 6 gas.