A Magnetic Extraction Channel for a 30-Inch AVF Cyclotron

The emittance and spot size of a cyclotron´s external beam is strongly affected by the magnetic fringe field of the cyclotron. This paper describes the design and performance of a magnetic channel which produces a nearly circular low emittance beam at the cyclotron exit port by controlling the fringe field gradients. The prediction and realization of desirable fringe field grzadients is discussed, and the performance of the magnetic channel in The Cyclotron Corporation´s Model CS-15 Cyclotron is reported.