Particle-in-cell simulations of microdischarges with extremely small characteristic sizes

Abstract

Summary form only given. Characterized by its small size (<;1 mm), a microdischarge has some unique features that do not exist in its large-scale counterpart. A very interesting feature of microdischarges is the significant impact of field emission when gap size is extremely small (usually <;10 μm). Because of the small size of a microdischarge, field emission can be ignited by applying a reasonable electric potential, and the current production can be quite sensitive to the field strength. This work considers the interaction between the microdischarge and field emission under various gas pressures, from low vacuum to atmospheric. One dimensional particle-in-cell Monte Carlo collision simulations show a significant enhancement of the field emission current due to the existence of ions. Ions generated in the microgap move much slower than their electron counter parts such that a positive space charge accumulates, altering the electric field in the electrode gap. Because of the sensitivity of field emission to the electric field, as predicted by the Fowler-Nordheim equation, even a slight change in electric field caused by the ionic space charge can lead to a significant enhancement of field emission. Understanding this interplay between the microdischarge and field emission will lead to greater insight in the breakdown process in microscale electrode gaps as well as reveal how field emission fundamentally affects microdischarge properties.