Runaway electron beams formed in atmospheric pressure air in a diode with dielectric films

The paper reports on a study of a supershort avalanche electron beam (SAEB) formed in atmospheric pressure air in a diode with dielectric films. The study shows that the number of electrons downstream of an Al foil anode increases gradually as a dielectric film 50 mu m thick is shifted from cathode to anode. With a film 100 mu m thick placed at 3 mm from the cathode, the number of electrons decreases similar to 4 times, whereas their number with the same foil placed at 1 and 11 mm decreases by no more than 30 %. It is supposed that the dielectric at 3 mm from the cathode substantially influences the formation of an ionization wave and that increasing its thickness causes a rapid decrease in SAEB amplitude.