Stepwise Ionization of Xenon in RF Plasma Display Panels

The efficiency for conversion of electrical energy to visible photons in typical Plasma Display Panels(PDP's)conditions (3-10%Xe in Ne, 100's of kHz, 500 torr, 100 microns) is low (about 1 lumen/watt). The main factor limiting the efficiency is the energy lost in heating ions in the sheaths. RF excitation (10's of MHz) would therefore be more efficient, and investigations of RF PDP's are underway. We present here a study of the role electron-impact ionization of the xenon metastable atoms on the ionization balance in RF PDP's. In this study, rate equations for the resonance, R, and metastable, M, atoms are coupled to our fluid model of PDP's. Cascading from and excitation to the higher excited states are included via one parameter. Uncertainties in the excitation transfer rates and branching ratios for cascading to R and M preclude a more precise treatment. For 3%Xe in Ne, 400 torr, and 40 MHz, direct ionization dominates the ionization balance. Stepwise ionization is important for low discharge powers and high xenon concentrations.