Design of the Axial Injection System for the NSCL Cyclotrons

The NSCL is designing an Electron Cyclotron Resonance source to be used in conjunction with its two superconducting cyclotrons, the K500 (in operation) and the K800 (under construction). The ECR beam will be injected through an axial hole. The high magnetic field in the cyclotron center (30 - 50 kG) limits the first orbit radius of curvature imposing strict limitations on the size of the deflection element used to bend the beam into the median plane. We have studied two different schemes to deflect the beam: electrostatic mirrors and spiral inflectors. The former are mechanically simpler, but the spiral inflectors give more freedom on the positioning of the first injected orbit. Results of these calculations as well as central region design and complementary focussing elements in the axial line are presented.