An electron gun (10) includes an electron multiplier (22, 22null, 22null, 110) has a receiving end (50, 50null, 50null) for receiving primary electrons and an output end (54, 54null, 54null) that emits secondary electrons responsive to primary electrons arriving at the receiving end. An electron emitter (20, 20null, 20null, 102) is arranged at the receiving end of the electron multiplier for supplying primary electrons thereto. At least one of an electrical and a magnetic focusing component (14, 16) is arranged at the open output end of the electron multiplier for focusing the secondary electrons to define an electron beam. In a suitable embodiment, the electron multiplier includes a generally conical substrate (74, 90) and an electron mirror (52, 521, 522, 523, 921, 922) including a high secondary electron yield film (70) disposed on an outer surface of the conical substrate.