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

摘要

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.