Influence of different processes of the electron emission on the ultrahigh charging of a dust particle in plasma by the energetic e-beam.

Abstract

Abstract Results of numerical modeling of dynamics of ultrahigh charging of the dust particle surrounded with plasma and irradiated by an electron beam with high electron energy are given in the presented work. The e-beam was created by the pulsed open discharge in strongly overvoltage regime.The maximum negative charge accumulated on the irradiated particle is defined by the intensity of processes of charging and discharging of a target. In general, the process of charging is defined by e-beam parameters (its energy and the current density) while the discharging of a target depends on many processes, such as delivery of positive ions from the plasma onto a negatively charged target and also an emission of electrons from a target surface. In its turn, the electron emission from a surface is caused by the various processes including kinetic emission of electrons due to impact of the target by fast ions, secondary electron emission by e-beam, thermo-emission and auto-emission of electrons in case of strong heating of a particle and emergence of the strong electric field on a surface of the highly charged target. The ultrahigh charging of the dust particle irradiated by an e-beam with the energy of 25 keV was modeled. Results of numerical calculations about influence of the listed above discharging processes of a target on its maximum negative charge and potential have shown that the greatest contribution to the target discharging process belongs to the kinetic electron emission caused by fast positive ions.