Modeling of highly loaded fluorescent lamps

Summary form only given, as follows. Numerical modeling of the positive column of fluorescent lamps under conditions of high current density are of current interest, particularly in view of recent developments in electrodeless lamps. Current models tend to overestimate radiation output, and consequently the maintenance electric field in these discharges. Under highly loaded conditions, mercury-rare gas fluorescent lamps exhibit strong mercury depletion on axis (cataphoresis), and an understanding of resonance radiation transport under these conditions is therefore vital to the development of models with a predictive capability. We have explored the effect of radial cataphoresis on resonance radiation trapping for situations in which the radiation transport is dominated by foreign gas broadening, Doppler broadening, or resonance collisional broadening of the spectral line. Several different production rates per unit volume of resonance (excited) atoms have also been studied. It is advantageous in many cases to parameterize the trapped decay rate in terms of the total number of ground state atoms in the positive column independent of their radial distribution. The results of this work have been included in a numerical model of the positive column and the predicted influence on discharge parameters will be presented for cases of interest to highly loaded lamps.