LTE Deviations as Function of radial position in Hg High-Pressure Discharge Lamps
Résumé
In the electric discharge plasma the electrons pick up energy from the electric field and partially transfer it to the heavy particles by collisions. Due to the relatively large difference between electron and heavy species mass, the energy exchange between them is rather inefficient. Thus, even in atmospheric pressure Hg discharges, the electron temperature may be substantially higher than the heavy particle temperature. We developed a model based on hydrodynamic conservation equations for electrons and gas particles. This equation set is solved by using a 2-D semi-implicit finite element scheme. Our results confirm quantitatively the existence of thermal equilibrium deviations in a such type of discharges. Furthermore, we show that, in a such type of discharges, the hot core is anyway closer to thermal equilibrium than the outer discharge jacket. As example, when pressure is relatively high (3 atm) the relative deviation on the axis is less than 0.5% however the same value becomes higher than 5% in the outer discharge regions. A similar behaviour is detected in the case of high arc currents.