On the observed energy of runaway electron beams in air

Abstract

Experiments with an air electrode gap have been performed where the current/charge of a picosecond beam of runaway electrons was measured over a wide range (up to four orders of magnitude) downstream of the absorbing foil filters. Measurements and calculations have made it possible to refer the beam current to the rise time of the accelerating voltage pulse to within picoseconds. It has been shown that, in contrast to a widespread belief, the runaway electron energies achieved are no greater than those corresponding to the mode of free acceleration of electrons in a nonstationary, highly nonuniform electric field induced by the cathode voltage. The experimental data agree with predictions of a numerical model that describes free acceleration of particles. It has been confirmed that the magnitude of the critical electric field that is necessary for electrons to go into the mode of continuous acceleration of electrons in atmospheric air corresponds to classical notions.

Generation of super-short avalanche electron beams in SF6

“…However, as shown Tarasenko, 2011;Tarasenko et al, 2005;2007;2008a;2008b;2013b), the runaway electron beam downstream of the foil anode consisted of two or three groups of electrons of different energies and the number of electrons with anomalous energy was not more than 10% . No RAEs with anomalous energy in atmospheric air were detected, like in the study by Mesyats et al (2011), and the energy of RAEs was assumed not to exceed eU m under any conditions. All other things being equal, comparison of the energy of RAEs in SF 6 and air demonstrated that the electron energy in air was higher than that in SF 6 , (Baksht et al, 2008).…”

The physical phenomena accompanying the sub-nanosecond high-voltage pulsed discharge in nitrogen

“…At the present is accepted that HV nanosecond discharge in pressurized gas is initiated by the runaway electrons (RAE) generated in the vicinity of the cathode and pre-ionizing the gas inside the cathode-anode (CA) gap while propagating towards the anode. There are many theoretical, 4 numerical 3,5-11 and experimental 3,[12][13][14][15][16][17][18][19] studies devoted to RAE generation during the nanosecond discharges. However, there is no generally accepted theory which can be used to describe the different experimental data obtained in experiments with cathodes having different forms, different CA gaps, gas type and pressure and different form and amplitude of the applied HV pulses.…”

“…Also in Ref. 19 using pico-second time-resolved diagnostics, the RAE with duration of $10 À10 s was described. Nevertheless, even in these experiments time resolution was !25 ps and thus does not allowing to obtain processes having smaller typical time duration.…”

Supershort avalanche electron beam inSF6and krypton

“…According to the research performed by Mesyats et al, all the energies of RAEs were not higher than eU m at atmospheric pressure in air [5,17]. In these papers, it was pointed that RAEs with anomalous energy were not obtained in atmospheric pressure air when voltage pulses with a rise-time of subnanosecond were applied across the discharge gap, indicating no RAEs with anomalous energy in atmospheric air existed.…”