Measuring time dependence of channel resistance for threshold electrostatic discharge*

Electrostatic discharge (ESD) from charged objects can be hazardous around electronics and combustible materials. Our group is using numerical models and experiments to better understand the energy that transfers through an threshold ESD channel. We constructed a low-inductance ESD discharge chamber that includes a storage capacitor and current-viewing resistor. While the spark resistance just after the initial breakdown can be measured by fitting to the the inductive decay of the current, at longer times the stored charge is depleted. To measure the conductivity for the later times we added a second storage capacitor in parallel that discharges slowly through a current-limiting resistor. By measuring the voltage on both sides of this resistor we can measure the current and voltage across the spark, and thereby estimate the resistance of the ESD channel as gas settles back down and the channel closes. We show, in air and argon, that the resistance of the spark gap is low during the inductive ringing, 3Ω, and quickly rises to 10Ω during the first 6μs after discharge. The resistance climbs exponentially to 200kΩ over 300μs. Using a fast gated camera we image the ESD to estimate the radius versus of time to gather information on the recombination process. LANL Publication ID: LA-UR-21-25764