Modeling the breakdown and glow phases during the ignition of HID lamps

Summary form only given. HID lamps are often ignited by one or more short, high voltage pulses (trigger pulses) superimposed on the low frequency, generator voltage. We have developed a self-consistent, fluid model of transient glow discharges to study the breakdown and glow phases in HID lamps from the time of the application of the trigger pulse(s) to the time when there is a fully-developed, quasi-steady state glow discharge. The transition to the thermionic arc is not considered here. Using this model we have investigated the influence of the height, width and number of trigger pulses on the generator voltage required to achieve a steady-state glow discharge. The model we use is one-dimensional, and the fundamental variables are the charged particle densities and the potential as functions of distance between the electrodes and time. The charged particles are described by their continuity equations and these are solved simultaneously with Poisson´s equation for the potential distribution. We suppose that there are free electrons present in the gap when the trigger pulse is applied. Results are given for Ar and Ar-Hg discharges.