Paschen's curve in microgaps with an electrode surface protrusion

Abstract

Paschen's curve in microgaps with a hemi-ellipsoidal protrusion on the electrode surface is studied using a two-dimensional fluid model. The breakdown voltage is identified when the discharge enters the subnormal region, according to voltage-current characteristics. It is found that the breakdown in a microgap with a surface protrusion on the electrode can result in a combined Paschen's curve, which transits from long-gap (distance between the cathode and anode without the presence of protrusion) behavior at low pressure to short-gap (distance between the protrusion apex to the opposite electrode) behavior at high pressure. As gas pressure decreases, the length of the optimal discharge path increases, automatically moving from the top of the protrusion to its side surface and then to the wider non-protrusion electrode gap. The effects of the protrusion height and radius as well as the discharge polarity on the Paschen's curve are examined in detail. The effects of the protrusion aspect ratio on field enhancement are also considered. This work provides insights into the design of microgaps with controlled breakdown voltage across many orders in pressure via engineered electrode morphology.