Electrical characteristics of breakdown phenomena

The phenomenology of breakdown in gases and liquids, and surface flashover at atmospheric pressures are investigated with high-speed electrical and optical diagnostics. The experiments utilize a 50Q coaxial transmission line system with an axial discharge and a load line to simulate a matched terminating impedance. DC breakdown, and in part pulsed breakdown, are characterized for argon gas, subcooled liquid nitrogen, biodegradable oil and vacuum. The discharge current and voltage are measured via transmission line current sensors and capacitive voltage dividers, which have a working range of 0.1 mA to IkA with temporal resolutions of 300 ps. Light emission is measured by photomultiplier tubes (800 ps risetime) and high speed photography. Some results indicate the presence of prebreakdown events preceding the main self-breakdown. These events occur microseconds before the main breakdown as nanosecond current and luminosity spikes.