Magnetic Field Design for a Combined Fixed Frequency and Frequency Modulated Cyclotron

A modification of the 185 MeV synchrocyclotron at the Gustaf Werner Institute, Uppsala, is under way. The reconstructed cyclotron will operate with frequency modulation for protons in the upper energy range (110-200 MeV), while low energy protons and heavier particles will be accelerated in fixed frequency isochronous mode. Circular trim coils will be used to adjust the basic field in order to keep focusing properties and the phase-energy motion within required limits with frequency sweep as well as with constant frequency. Valley coils will be used for harmonic corrections at the centre and at the extraction radius, where they also will provide some gradient correction.