Monte Carlo simulation of radiation trapping in electrodeless lamps: a study of collisional broadeners and isotopic abundances

Summary form only given, as follows. Electrodeless gas discharges are finding increasing applications as lighting sources, especially for Ar/Hg based fluorescent lamps. The particulars of resonance radiation trapping from Hg are an important consideration in the design of these sources. For simple geometries, analytical forms of the radiation trapping factor can be obtained. For current lamp designs, however, the geometries are more complex and the densities of absorbers and emitters are not uniform. To address these complexities, a Monte Carlo model for resonance radiation transport has been developed which accounts for frequency resolved absorption and emission using partial frequency redistribution algorithms. Isotope effects and hyperfine splitting have also been incorporated into the model. The radiation transport model has been integrated into a 2-dimensional self-consistent plasma equipment model which accounts for electromagnetics, electron energy transport and heavy particle transport while solving Poisson's equation. For the conditions of interest (100s mTorr, 10s W), there can be significant spatial variations in the gas temperature and composition. Species resolved gas temperatures and densities are therefore fed-back to the radiation transport model to properly account for broadening mechanisms, and absorption and emission probabilities. Results from the model will be discussed for the effects of foreign gas broadening in gas mixtures (e.g., Ar-Xe-Hg) on trapping and exit spectra of Hg 254 nm and 185 nm radiation of various isotopic abundances. The consequences of resonance broadening resulting from mercury-mercury collisions on the trapping factors will also be discussed.