Computational design studies for an ion extraction system for the Oak Ridge National Laboratory ECR ion source

A three-electrode system for optimally extracting, high-intensity, multi-charged ion beams from an all-permanent-magnet, "volume"-type, ECR ion source, has been computationally designed. Beams of highest quality and transportability are extracted whenever the angular divergence is minimum. Under this condition, the plasma boundary has an optimum curvature, the angular divergence is consequently minimum; the perveance, the extraction gap, and the current density each have optimum values. Results obtained from computational simulation studies of the extraction optics are found to closely agree with those derived from elementary analytical theory for extraction of space-charge-dominated beams.