Designing advanced filters for macroparticle removal from cathodic arc plasmas

Curved magnetic filters are commonly used with cathodic arcs to remove macr oparticles from the plasma stream, making them suitable for the preparation of smooth, dense and defect-free films. Plasma losses associated with thes e Biters are rather high. The highest reported ion current transported thro ugh a curved macroparticle filter is 2.5% of the are current. In this paper we show that it is possible to finely control both the shape and spatial p osition of the plasma beam as it passes through a curved magnetic filter by the addition of strategically placed current-carrying wires. Our modificat ions consisted of additional current loops at the entrance and exit of the filter to reduce the divergence of magnetic field lines there; a number of conducting wires were also placed outside the filter along its length to ce ntre the beam in the filter. We were able to improve the plasma transport e fficiency by modifying the paths of magnetic field lines through the 90 deg rees filter with the aid of computer calculation, achieving a filtered tita nium ion current up to 6.3% of the are current.