Asymptotic Analysis of AC Microscale Gas Breakdown *

Characterizing radiofrequency (RF), microwave (MW), and direct current (DC) breakdown in microscale gaps is critical for multiple applications, such as cold-plasma based limiters and protection shields, which offer an enhanced solution for protecting electronics against high power electromagnetic radiation due to their self-sustainability and reconfigurability. While prior studies considered transitions between RF and MW at macroscale¹ and DC at microscale², a full asymptotic theory linking RF, MW, and DC breakdown at microscales remains elusive. This study considers microscale MW breakdown due to field emission (FE) and avalanche using matched asymptotic analyses considering small (FE) and large (Townsend avalanche (TA)) ionization for DC and low (RF) and high (MW) frequencies to derive relevant scalings at microscale. We study the impact of gas, pressure, and frequency on the breakdown voltage parametrically, and quantify FE and TA contributions. Furthermore, we compare to preliminary results from particle-in-cell simulations and discuss relevance to device design.

¹A. M. Loveless and A. L. Garner, Phys. Plasmas 24, 104501 (2017).

²A. L. Garner, et al., IEEE Trans. Plasma Sci. 48, 808-824 (2020).