Hollow cathode type ion source system including anode screen electrodes

Abstract

An ion source having an extremely high beam current density at low gas flow rates and therefore, low system pressures. The ion source includes an electrode system which consists of a cathode of, for example, spherical or cylindrical configuration which cathode encloses an anode having a pair of screen electrodes symmetrically disposed about and parallel to the plane of the anode, the anode and screen electrodes each having apertures formed therein. A gas inlet is formed in the cathode wall, preferably between the screen electrodes, and an ion beam outlet aperture of substantially the same size as the anode aperture is provided in the cathode. Upon application of suitable potentials to the anode, cathode and screen electrodes, the latter preferably being at a potential substantially equal to cathode potential, gas introduced through the gas supply inlet is ionised and the positive ions created are accelerated towards the cathode and emerge in a beam through the ion beam outlet aperture.

Dependencies are inferred from the claim text.