A compact superconducting cyclotron for the production of high intensity protons

This paper reviews a study of a compact superconducting cyclotron to accelerate 200 microamps of protons to 250 MeV. The basic cyclotron structure is the same as that developed in a previous study of a 250 MeV cancer therapy cyclotron, the chief difference in the study reported here being much higher beam current (x10,000) than in the therapy cyclotron to meet desired specifications for the 'Driver' accelerator of an ISOL type radioactive beam facility. The increase in current is far below (x1/50) the axial space charge limit of the proposed cyclotron, but longitudinal space charge requires changing the extraction system from a single turn to a multi-turn system thereby increasing beam losses. Leading design uncertainties, namely the overall efficiency of the multi-turn extraction system and the distribution of radioactivity generated by lost beam are addressed herein; results indicate reasonable residual activity in the cyclotron from the perspective of customary 'hands-on' maintenance operations.