Phase stability of electrical discharges in the plasma display cell

In response to a sustaining signal impressed across a Plasma Display Panel, a cell in an "on" state exhibits a sequence of pulse discharges that occur once in each half-cycle when the cell voltage meets the Townsend breakdown condition. Experiments with Plasma Display Panels, and also, earlier observations On larger insulated gas discharge cells have shown that the firing times are precisely defined in phase. We suggest that this phase regularity is maintained by a mechanism which relates the intensity of a pulsed discharge to the slope of the exciting voltage at the time of the discharge. A small perturbation in the firing time of a discharge, therefore, changes the intensity of that discharge, The corresponding change in accumulated charge on the cell wall then changes the firing time of the next discharge in the sequence in a way that reduces the original perturbation. In the succeeding discharges the perturbation diminishes to zero exponentially. The analysis, presented in this paper, shows that the magnitude of the charge-slope relation, and the wave form of the sustaining voltage combine to determine the stability and the relaxation time of the process. In particular it shows that the perturbation can be effectively damped out in several cycles--a condition frequently observed. The talk will be illustrated by photographs of oscillograms which show different relaxation times in the approach to equilibrium.