Generation and registration of runaway electron beams during the breakdown of highly overvoltaged gaps filled with dense gases

Abstract

The breakdown of the gaps providing inhomogeneous electric field strength distribution fed by voltage pulses with subnanosecond risetime has been experimentally studied. Using a four-channel ICCD camera and an ultrafast streak camera, the dynamics of plasma glow in the space between a sharp-ended tubular and a plane electrodes during the prebreakdown stage of a nanosecond discharge has been investigated. In addition, the parameters of a runaway electron beam generated during this stage of the discharge in SF6, CO2, Ar, and N2 at pressures of up to 0.3, 0.7, 1.0, and 1.2 MPa, respectively, were measured with a collector mounted behind a thin-foil anode. The generation of a runaway electron beam and fast electrons contributes to the formation of a discharge in a diffuse form that is observed in the experiments under the conditions specified above. It was shown, that the time moment, at which a runaway electron beam is detected with the collector corresponds, approximately, to the time moment when the voltage across the gap reaches its maximum value.