Energy distribution of runaway electrons generated by a nanosecond discharge in atmospheric-pressure air

Spectrum of fast electrons in a subnanosecond breakdown of air-filled diodes at atmospheric pressure

“…In recent years, the generation of beams of fast electrons (runaway electrons) has been the subject of increasing interest [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. It was shown that in atmospheric pressure air, the FWHM of the e-beam current pulse is ∼0.1 ns at a generator voltage ranging to over ∼100 kV [4], and the amplitude of the e-beam current downstream of the gas diode foil can reach ∼50 A [8,12].…”

“…The authors of [21] also point out that the attenuation curves of the e-beam current downstream of the foils are indicative of polyenergetic fast electrons in the discharge; however, no electron spectrum is given in the paper. Later on, the spectra of runaway electrons arising in a breakdown of air gaps at atmospheric pressure in an inhomogeneous electric field were much addressed in the literature [1,4,6,[8][9][10][11][12][13][14][15]22]. This problem is of fundamental importance, since high-energy electrons and x-ray quanta produced on deceleration of electrons at the anode can markedly affect the gas breakdown and the space form of the nanosecond discharge.…”

“…The number of fast electrons with anomalous energy, in this case, is relatively small and is less than 10% for a tubular cathode. Measurements of the electron energy distribution [13][14][15] and energies of x-ray quanta using attenuation in foils give indirect evidence for the presence of three groups of electrons found in [4,6]. However, the procedure of electron spectrum reconstruction employed in [6,13,15] provides for essential a priori information on the spectrum under reconstruction.…”

“…Measurements of the electron energy distribution [13][14][15] and energies of x-ray quanta using attenuation in foils give indirect evidence for the presence of three groups of electrons found in [4,6]. However, the procedure of electron spectrum reconstruction employed in [6,13,15] provides for essential a priori information on the spectrum under reconstruction. If this information was not taken into account, one attenuation curve would give several different spectra with equal reliability.…”

Detection of x-ray emission in a nanosecond discharge in air at atmospheric pressure

“…6 However, the upper limit of applicable regime of the streamer mechanism is uncertain, and some studies have suggested that two to three times self-breakdown voltage should be the upper limit. [6][7][8] A simple way to characterize and quantify the runway role of fast electrons is through x-ray measurements. The collision ionization induced by the runaway behavior of fast electrons is considered to be more rapid and more effective compared with the space photoionization in the conventional streamer mechanism.…”