Study of photometric properties of high-pressure mercury discharge with thallium iodide additives (HgTℓI) using the ray-tracing method

Abstract

The photometric properties of HgTℓI high intensity discharge (HID) lamps have been calculated by solving the radiation transport equations in the discharge, using the ray-tracing method. The partial pressures of the various chemical species in the plasma are computed assuming the plasma is in local thermodynamic equilibrium (LTE), using a curve fit to an experimentally measured temperature profile. The plasma is also assumed to be fully mixed, implying a constant mercury/thallium ratio throughout the discharge tube. The spectral line broadening includes neutral Van der Waals and charged particle Stark broadening. The potential influence of ‘de-mixing’ on the spectra is also considered.