Numerical Simulation of Townsend Discharge, Paschen Breakdown and Dielectric Barrier Discharges

Practical understanding of electrical discharges between conductors or between conductors and dielectrics is instrumental for the development of novel charging devices for Digital Printing Applications. The work presented on this paper focuses on fundamental aspects related to the inception of electrical discharges and breakdown in the initial stages (few 100's of mu s) to a detail hard to match with experimental techniques. Numerical simulations of 1-D Townsend and Dielectric Barrier Discharges (DBDs) are performed using a commercial Finite Element package (COMSOL). A combined fluid model for the electron and Ion fluxes is used together with a local field approximation on a 1-D domain comprised of Nitrogen gas. The renowned Paschen breakdown result is successfully predicted numerically. Results are shown for the transient Townsend discharge that leads to this breakdown offering insight into the positive feedback mechanism that enables it. These transient results show how impact ionization combined with cathode secondary emission generate increasing waves of positive ions that drift towards the cathode again self feeding the discharge process. The simulation is then extended to predict the nature of a DBD in the case of a single voltage pulse.