SINGLE-STAGE 5-GHZ ECR-MULTICHARGED ION-SOURCE WITH HIGH MAGNETIC-MIRROR RATIO AND BIASED DISK

A low-cost, single-stage 5 GHz electron cyclotron resonance (ECR) multicharged ion source (MCIS) has been constructed for various atomic collision experiments. It features an axial magnetic field with a mirror ratio of up to five, and a magnetic hexapole field produced by a simple Nd-Fe-B permanent-magnet assembly. A disk probe axially mounted near the ECR resonance zone opposite to the ion extraction, and negatively biased with respect to the ECR plasma potential, permits reduction of the appropriate neutral feeding gas pressure by an order of magnitude, resulting in greatly improved ion charge state distributions, as normally offered by two-stage ECR-MCIS only. We present performance' data for multicharged ion production from Ar and N2, including measured ion current emittances.