On the generation and disruption of a picosecond runaway electron beam during the breakdown of an atmospheric-pressure gas gap

Abstract

The generation and disruption of the picosecond runaway electron beam in atmospheric pressure strongly overvolted gas gap is considered with emphasis on the runaway kinetics, the increase in emission current and plasma density, and beam instabilities. It has been shown that a few-nanosecond ten-kV prepulse gives rise to a streamer. Application of the main pulse (∼2 MV/ns) results in the runaway electron beam generation with the streamer electrons involved in the acceleration, and in increase of the electron emission from the cathode and the plasma density. At the high enough plasma density, fast beam instability disrupts the runaway electron beam.

Experimental and theoretical investigations of the conditions for the generation of runaway electrons in a gas diode with a strongly nonuniform electric field

“…This approximation was used to simulate the generation of a runaway electron beam at initial stages of breakdown in a gas gap with a nonuniform field [27]. A similar formula for the longitudinal field distribution in an electrode gap was used to simulate the generation and cutoff of a picosecond runaway electron beam [28]. Formula (7) provides a fairly qualitative approximation of the numerically calculated field distribution near the emitting edge of a tubular cathode [12].…”

On the dynamics of a subnanosecond breakdown in nitrogen below atmospheric pressures

“…These issues are under discussion in different research groups. [7][8][9][10][11][12][13][14] The processes involved in a breakdown in a highly overvolted gap should be studied both by experimental methods and by numerical simulation, because direct observation of subnanosecond processes with the measuring equipment available to date is extremely difficult. For successful simulation, it is required to choose a method which allows calculation of the breakdown dynamics.…”

On the consistency between ionization and trapped runaway electron acceleration in a pulsed discharge

“…This implies that as the plasma density reaches this level, there occurs the transition from a collision-dominated mode with ω pe < ν coll to a plasmaoscillation-dominated mode with ω pe > ν coll . The interruption of an REB due to plasma oscillations was proposed as a mechanism of its picosecond-scale disruption [17]. Recall that we have not considered here the explosive electron emission from the cathode that can substantially increase the plasma density [18,19].…”