Abstract: The improved ion source of the present invention includes upper and lower spaced apart but coaxially arranged magnetic pole rings having differing inner diameters. Because of the non-symmetry of the pole pieces or rings, the magnetic flux field created therebetween is non-symmetrical from top to bottom. This, and the arrangement and configuration of the anode ring located between the pole pieces, create an increased plasma region and higher plasma density resulting in increased thermal management, improved stoichiometry and increased density of the thin film devices being fabricated.