FIELD EMISSION ELECTRON GUN UTILIZING MEANS FOR PROTECTING THE FIELD EMISSION TIP FROM HIGH VOLTAGE DISCHARGES

摘要

A field emission electron gun comprises a field emission tip as its source of electrons. A first anode is spaced downstream from the tip and when a voltage is applied between the first anode and the tip, electrons from the tip are accelerated toward the first anode. An opening in the first anode limits the angular spread of the electron beam. A second anode is spaced downstream from the first anode and when a voltage is applied between the second anode and the tip, the energy level of the electrons at the image or specimen plane is controlled. The electrostatic field between the first and the second anode brings the electron beam into focus.