THE BREAKDOWN AND GLOW PHASES DURING THE INITIATION OF DISCHARGES FORLAMPS

High intensity discharge (HID) lamps are often initiated by the applic ation of one or more short, high-voltage, breakdown pulses superimpose d on a 50 or 60 Hz generator voltage. A successful transition from the breakdown event to steady-state operating conditions in HID lamps req uires that the lamp-circuit system be adequate to sustain the plasma c reated during breakdown until the electrodes are heated to thermionic temperatures. In this article, we use a one-dimensional (in the axial direction) transient discharge model to study the conditions needed to sustain the cold-cathode discharge after a breakdown event has occurr ed. While the application of our one-dimensional model to real lamps i s approximate, we find that the model predictions are consistent with experimental results in HID lamps, a few of which are presented here. The main conclusion from this work is that, after breakdown, the volta ge necessary to sustain a glow discharge is dependent on the source im pedance, the gas composition, and on the plasma density created by the breakdown event. (C) 1997 American Institute of Physics.