THE CHEMICAL-COMPOSITION OF PLASMAS GENERATED IN HIGH-PRESSURE DISCHARGE LAMPS CONTAINING TIN AND SODIUM-HALIDES

In order to model high pressure discharge lamps which contain metal halides, the chemical composition in the plasma region is required. We have developed a procedure for calculating the composition of a plasma in local thermodynamic equilibrium, between 1500 and 6000 K, including the effect of radial diffusion. Mixtures of tin halides and sodium halides, when added to high pressure mercury discharges, produce highly efficient white light sources. We report a detailed study of the SnCl//2 plus NaCl (50:50) system and a preliminary investigation of the SnCl//2 plus NaI (50:50) system together with the plasma compositions for the corresponding lamps. These results show that radial diffusion has a highly significant effect on the plasma composition.