Mechanisms and Modeling of High Pressure Breakdown Physics in Ultra-Zero Air

In the high-pressure regime above 300-500 psig, voltage-breakdown models such as the Paschen’s law fail [1]. Below 300 psig the $E/p$ values suggest that the breakdown mechanism, specifically at high $E/p$ values is dominated by the ionization mechanism. As the air pressure is increased, the breakdown mechanism shifts from an ionization dominated regime to an attachment dominated regime at $E/p$ values below 30. Thus, current Paschen equations will over predict the breakdown voltage and the electric field at which high-pressure spark gaps can be operated. Notably, as the attachment mechanism starts to dominate the breakdown physics the breakdown field in a high-pressure spark gap asymptotes at 1-1.2 MV/cm. Using recent data collected at Sandia National Laboratories, we have implemented corrections to breakdown prediction modeling using COMSOL to predict the breakdown voltage that can be achieved in the high-pressure regime, from 500-1500 psig. This research highlights how these corrections to the breakdown prediction models are implemented and the results of the simulations are compared to our data as well as other small gap data. We also compare the model to published literature values and to large gap breakdown in the 0.6-cm to 1.0-cm regime.