Gas Breakdown in Atmospheric Microgaps with Surface Protrusion on the Cathode

Abstract

Gas breakdown phenomenon in macrogaps has been widely studied and is well understood by the Paschen's law1,2. The breakdown mechanisms can be more complicated in microdischarge at atmospheric pressure, since the dimensions are sharply reduced, where the presence of surface protrusion on the electrode surface becomes important3, In this paper, by using a two-dimensional fluid model, breakdown voltages in microgaps are predicted based on the voltage-current (VI) characteristics. The obtained VI curve, which includes the dark discharge region, the Townsend discharge region and the subnormal glow region, identifies the breakdown voltage when the discharge current enters the subnormal region. The effects of the protrusion's size and aspect ratio on the breakdown voltage are compared. The results show that the protrusion's size has a more profound effect on the breakdown voltages than the aspect ratio. When the effective distance between the anode and cathode is fixed, the breakdown voltage has a minimum value as the aspect ratio increases. As the effective distance increases, the breakdown voltage with a surface protrusion increases faster than that without a protrusion, resulting in an intersection between the two curves. The current density distribution on the cathode surface and the effect of the micro gap aspect ratio on the breakdown voltage are also presented.