Numerical analysis of the ionization of gaseous methane induced by pulsed electron beams

Abstract

The contributions of beam electrons (the first term) and secondary electrons (the second term) accelerated by the electric field induced by two pulsed electron beams (Febetrons 705 and 706) to the total ionization of methane in the pressure range of 10 to 760 Torr were calculated by a numerical analysis. The fraction of the secondary electrons neutralized during the pulse duration was also evaluated. The computation result showed that, for a Febetron 705, the ionization is mainly due to the first term and that most of the secondary electrons produced are neutralized during the pulse duration. For a Febetron 706, the contribution of the second term is large even at 300 Torr and the secondary electrons recombine only by 20%–30% with ions during the pulse duration. For this beam, the effect of the induced electric field remains after the pulse. The mean secondary electron energy during the pulse also was estimated.