Explosive, critical electron emission from dielectric induced by high-current-density electron beam injection; theoretical and computer simulation

Abstract

High-current density (HCD) electron beams of nanosecond pulse duration are applied for charge injection into various dielectrics to induce the critical electron emission from dielectric into vacuum. It is shown that critical electron emission induced by HCD injection of electrons arises in the form of a gigantic single pulse, which is of peak value of 10-1000 A and delayed from injection one for 1-20 ns. Delay time depends on the current density of the primary electron beam. Direct experimental evidence is obtained for the intense generation of free electrons and holes in the subsurface layer of a dielectric owing to the Poole-Frenkel effect and the impact ionisation of traps in a high electric field. This process is considered to be the main reason for the sharp transition of the ordinary low-current-density field electron emission to the high-power one. The latter is not uniform and accompanied by point explosions on the dielectric surface and ejections of ion plasmas from these points into vacuum. These explosions are considered as the main reason for the transition of the field electron emission from dielectric (FEED) to critical. The latter is the explosion electron emission of dielectrics (EEED). If the electron current to the emitting centers on the dielectric surface is maintained at the necessary value, then the critical electron emission always causes a vacuum discharge between the dielectric surface and metallic collector. The mechanism of EEED is discussed using computer simulation of the basic processes.