High-power critical electron emission from dielectric induced by high-current-density electron beam injection and its transition to vacuum breakdown

Since 1975, the authors´ laboratory has been investigating the critical electron emission from dielectrics into vacuum with nanosecond time resolution using high-current-density electron accelerators. It allowed them to clear up some intrinsic properties of the critical electron emission induced by electron beam injection: (1) the emission pulse is delayed for several nanoseconds from the injection pulse; (2) the peak value of the emission current reaches 100-1000 A; (3) direct experimental evidence is obtained for intense electron-hole generation by superhigh electric field in subsurface layer of dielectric-this process is discovered to be the main reason of the transition to critical electron emission; (4) critical emission is not uniform and accompanied by point explosions on the dielectric surface and by injections of ion plasmas from these points into vacuum; and (5) transition of critical emission to vacuum breakdown has been observed