  The 28 GHz ECR(Electron Cyclotron Resonance) ion source is under development
to supply various beams from proton to uranium at RISP(Rare Isotope Science
Project). The superconducting magnet system for a 28 GHz ECR ion source
consists of four solenoid coils and a saddle type sextupole. To meet the design
requirement of ECR ion source, a numerical simulation was accomplished by using
the KOBRA3-INP to optimize the extraction system which is the three dimensional
ion optics code. The influence of the three dimensional magnetic field and the
space charge effect was considered to extract the highly charged ion beam. In
this paper, the design results of the extraction system were reported in
detail.
