Air Breakdown in the Field of Traveling Tem-Wave Assisted by Runaway Electrons

The method of dynamic time-domain reflectometry is used to investigate a pulsed breakdown of an air-filled coaxial line assisted by the traveling voltage wave with amplitude of about –100 kV. The TEM-wave radial electric field exposure time was ~1 ns. The field enhancer representing a protruding disk-type insert into the central electrode of the line created conditions for spatial breakdown localization. The data obtained have been compared with the artificial short-circuit mode for the radial line gap at the location of the enhancer. With increase in the voltage amplitude and the field distortion caused by the enhancer, the criteria for electrons to run away were satisfied. In this case, a flow of fast particles is formed which initiates the breakdown with increased voltage collapse rate and discharge current and decreased resistance.