Design of SuSI - Superconducting Source for Ions at NSCL/MSU - I. The Magnet System

An ECR ion source is being designed to initially serve as a test bench for development and later will replace the existing 6.4 GHz SC-ECRIS. This ECRIS will operate at 18+14.5 GHz microwave frequencies. The radial magnetic field will be produced by a superconducting hexapole coil, capable of 1.5 T at the aluminum plasma chamber wall (R=50 mm). The axial trapping will be produced with six superconducting solenoids enclosed in an iron yoke. We will present the Flexible Axial Magnetic Field Concept, introduced for the first time in this design, which will allow tuning the distance between the plasma electrode and resonant zone in the plasma. The distance between the two axial magnetic maxima will be also tunable in the range of 340 to 460 mm.