Vacuum 56(2000) 159-172 In the UK, Teer Coatings Ltd. were quick to recognise the potential of multiple magnetron systems, and, in early 1990s, developed a patented design of commercial and research scale CFUBMS systems[28]. In these, and other similar systems developed elsewhere[8,29], an even number of vertically opposed magnetrons surround the rotating substrate holder. Adjacent magnetrons have opposite magnetic polarities and the field lines are closed As stated above, such systems are capable of transporting high ion currents to the substrate. However, recent developments in magnetron design and the use of high strength rare earth magnets in the magnetic arrays have led to significant further increases in the magnitude of the ion currents drawn at the substrate. Early magnetrons generally made use of ferrite magnets which gave a maximum field strength of the order of 300-500 G at the target surface[27,30]. With improved magnetron design and the introduction of rare earth magnets, field strengths in excess of 1 kG are now obtainable at the