Vacuum arc plasma transport through a magnetic duct with a biased electrode at the outer wall

Metal plasma formed by a vacuum arc plasma source can be passed through a t oroidal-section magnetic duct for the filtering of macroparticles from the plasma stream. In order to maximize the plasma transport efficiency of the filter the duct wall should be biased, typically to a positive voltage of a bout 10-20 V. In some cases it is not convenient to bias the duct, for exam ple if the duct wall is part of the grounded vacuum system. However, a posi tively biased electrode inserted into the duct along its outer major circum ference can serve a similar purpose. In this article, we describe our resul ts confirming and quantifying this effect. We also show the parametric depe ndence of the duct transport on the experimental variables. (C) 1999 Americ an Institute of Physics. [S0034-6748(99)01008-4].