An electron gun that generate an electron flow and the application of this gun to produce rf energy or for injectors. The electron gun includes an electrostatic cavity having a first stage with emitting faces and multiple stages with emitting sections. The gun also includes a mechanism for producing an electrostatic force which encompasses the emitting faces and the multiple emitting sections so electrons are directed from the emitting faces toward the emitting sections to contact the emitting sections and generate additional electrons and to further contact other emitting sections to generate additional electrons and so on then finally to escape the end of the cavity. A method for producing a flow of electrons.