Simulation of surface discharge dynamics by means of cellular automata

Abstract

A dynamic model of a creeping discharge over a dielectric surface is presented. A discharge area (above a dielectric sheet separating a metal needle from a ground plain electrode) is presented as a system of gas sphere cells covering the dielectric. A discharge tree (conducting cluster) is represented by a nonlinear circuit consisting of capacitances, nonlinear conductances, and controlled sources. The sources simulate the potential caused by the needle electrode and free charge located in the neighboring cells. The coefficients for the controlled sources and cell capacitances are determined from the results of static field calculation. The effects of electron drift, impact ionization, and photoionization are involved into the conductance model. Physical parameters of the latter two processes are deduced from the experimental data available in the literature. The criteria for cell initiation are obtained for different applied voltages such that dynamic characteristics of the model correspond to the experimental ones. The experimental results for the nanosecond discharges are used here considering the streamer phase of discharge development. Further improvement of the conductance model is discussed with respect to plasma heating up to the temperatures enough for the streamer-to-leader transition. In addition to discharge patterns which were created to be similar to experimental Lichtenberg figures, the model allows us to determine such local properties of the discharge as current, voltage drop, loss, field, and charge distribution.