Measurement of ESD plasma propagation on a positively charged ring coupon

Dielectric surfaces such as those on solar arrays are susceptible to surface charging in the space environment. With sufficient charging, a spontaneous arc can occur, triggering an outward-propagating electrostatic discharge plasma. The propagation parameters of this plasma determine the amplitude and duration of potentially damage-inducing current transients. Previous experiments attempting to characterize propagation speeds have used varying geometries, methods, and analysis, yielding widely-varying results. Experiments were conducted at The Aerospace Corporation on a novel test article designed to explicitly measure ESD plasma propagation. Electron beam impingement was used to produce a positive electric potential on dielectric surfaces (a.k.a. “inverted gradient”) and ESD-induced current transients on substrate electrodes were measured. Various propagation parameters are derived and discussed.