Calculation and Analysis of a Self-Shielded 13-MeV Cyclotron Magnetic Field

Abstract

A self-shielded four-sector 13-MeV cyclotron magnet has been designed for positron-emission tomography (PET). Compared with the previous one, which was built for the first time in Korea in 2003, this newly designed cyclotron is superior because it is compact and the stray field is reduced. An isochronous field was achieved by placing several side shims and by slightly varying the vertical magnet gap along the radius of the cyclotron. We show that the phase excursion is maintained within +/- 5 rf degrees and that the vertical and the horizontal focusing frequencies are sufficiently away from harmful structural resonances. The expected total power consumption, which is less than 15 kW, is moderate.