Reflectometry of Picosecond Emission and Discharge Processes in a Gas-Filled High-Voltage Coaxial Line

Abstract

Emission and discharge processes during the passage of high-voltage subnanosecond pulses with variable amplitude and duration along a gas-filled coaxial transmission line (CTL) are studied. Homogeneous CTL as well as CTL with special disk inserts (electric field enhancers initiating electron emission processes) on its central electrode were used. Data on the propagation and distortion of pulses were obtained and analyzed for different gases (nitrogen, hydrogen, SF6, and air) in a wide range of pressures. The voltage/field ranges and pulse durations are established where the role of runaway electrons (RAEs) appearing near the enhancer is essential in the breakdown development. It is shown that the effect of RAEs can be suppressed by shortening the voltage pulse even for hydrogen, which has a reduced static breakdown field and a high rate of ionization. It is also demonstrated that the RAE generation is abruptly replaced by the explosive electron emission from the enhancer edge with decreasing pressure from atmospheric to technical vacuum.