Continous multi-keV electron beam source using a hollow cathode

A multi-kilovolt, compact electron beam source is being developed for use in a laboratory plasma physics experiment to simulate the energetic electron population present in the magnetosphere and the associated space plasma physics phenomena. In parallel, a similar source is intended for welding and metal forming applications. The source operates by extracting electrons from a hollow cathode plasma that has been biased to the required beam voltage. The hollow cathode operates in the mTorr pressure range (Argon) at approximately 400V and current up to about 150mA (power supply limited) in a uniform 100G field. A variety of electron extraction geometries have been implemented, including grids and plates of differing thicknesses and hole diameters, yielding a largest extraction efficiency of approximately 30%. The thermal management problem of continuous operation is solved by making the hollow cathode wall also serve as a vacuum wall so that it may be cooled externally.