The design and development of a ring cathode electron gun as an evaporation source

The RG2 ring cathode gun is a simple application of electron beam heating. The gun described was developed to provide a relatively inexpensive source for evaporating a range of metals and oxides which were otherwise difficult or impossible to evaporate by conventional resistance heating. Following several stages of improvement the gun was progressively reduced in size and the 'optics', or focusing, improved so that in its existing state an area of approximately 2mm diameter is heated. It was decided to limit the accelerating voltage as far as possible to minimize the practical problems associated with its operation and also the manufacture of the power supply. As development proceeded it became apparent that the relatively low accelerating voltage chosen improved the flexibility of the gun. Two versions are manufactured, the first, equipped with a six position rotary hearth, and the second, utilising a single hearth, is intended to be used as one of a pair. The latter design was reduced in size even further in order to minimize the distance between two adjacent guns. (author)