High-power critical electron emission from dielectric induced by injection of high-current-density electron beam

High-current-density 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 high-current-density injection of electrons arises in the form of gigantic single pulse, which is of peak value of 10-1000 A and delayed from injection one for 120 ns. Delay time depends on the current density of electron beam being injected. The direct experimental evidence is obtained for intense generation of free electrons and holes in subsurface layer of a dielectric due to Poole-Frenkel effect and impact ionization of traps in high electric field. And this process is considered to be the first main reason for the transition of the ordinary low-current-density electron emission to the high-power critical one. The last is not uniform and always accompanied by point explosions on the dielectric surface and ejections of ion plasmas from these points into vacuum. And these explosions are considered as the second main reason for the transition of the ordinary electron emission to the critical one. So the last is explosion electron emission of dielectrics (EEED). If the electron current to the emitting centers on the dielectric surface is maintained at the needed value then the critical electron emission always causes the vacuum discharge between the dielectric surface and metallic collector. The mechanism of EEED is discussed using the computer simulation of the basic processes.