Coupled Electrical and Optical Characterization of Electrostatic Discharges*

Electrostatic discharge (ESD) can harm electronics and sensitive materials. ESDs that are limited by stored charge on objects of moderate size are closer to threshold than arc switches. We are studying the energy transfer and plasma dynamics in ESDs. We develop numerical models and make electrical and optical measurements to understand the time dependent resistance and electron and neutral density evolution in ESDs.

Our home built ESD chamber has a storage capacitor and current-viewing resistor. To obtain time-dependent electron and neutral density profiles, we analyze two-color Mach-Zehnder interferograms with wavelet transforms and Abel inversion. The fast-framing cameras are currently triggered on the leading edge of the spark; a UV triggering pulse will allow us to measure the earlier ESD phases.

Coupling our electrical and optical measurements allows us to determine how much of the resistance changes are attributed to the evolution of the electron density. The rise in ESD channel resistance following the initial breakdown occurs in distinct phases. In the 1-10us timeframe, we see a rise in resistance without density changes, pointing to plasma cooling as the cause. The combination of these data sets informs our models of the spark evolution and low-temperature recombination.