A Study of a Duoplasmatron Ion Source with an Expansion Cup

This work describes a study of the Duoplasmatron ion source for the purpose of investigating the conditions necessary to improve its performance. First a general review is made of theoretical considerations involved in the source's plasma mechanism and the geometry of the extraction system. Then the experimental work deals with the arc discharge characteristics as well as the source's performance when the beam is extracted with a simple Pierce extracting electrode. Through an invar anode insert a 70 mA was obtained at 35 kV. The main improvement was then due to beam extraction from an expansion cup which rendered a 300 mA beam at a lower voltage of 18 kV. The use of different anode materials has indicated the influence of magnetic field penetration on plasma focusing within the expansion cup. A beam current reaching 1 ampere was noticed when a non-magnetic anode was used.