Space-charge-limited current density as a function of electron flow duration in an emissive diode

Abstract

From basic laws governing the flow of electrons in a plane diode, we obtain combined relations about boundaries of space-charge-limited current density variations in an electronic-injector diode when duration of emission is varying. Although diode geometry of effective injectors is generally more complicated than that of a plane diode, we point out how the simplest relations can be used with a relatively good approximation. Then typical temporal modes of diode operation are analyzed. For each one, we give characteristic equations connecting peak intensity, maximum charge, and current duration in the diode, and we determine their applicability. Then we define a time that is a typical limit between the two principal temporal operating regimes. Utilization of reduced variables permits application of the main results to many practical situations such as comparison between working performances of photoinjectors assisted by laser, and prediction of maximum peak current available at the diode output for a given duration.