Design of a magnetic system for an MCC 30/15 cyclotron and field formation with movable shims

To accelerate ions with different charge-to-mass ratios, isochronous dependences of the magnetic field that differ both in the mean value of the field and in its spatial distribution are needed. An approach to configuring such a field in isochronous cyclotrons using magnetic shims is suggested. Field maps obtained experimentally and via computer simulation to accelerate negative hydrogen and deuteron ions in an MCC 30/15 cyclotron intended for medical purposes are presented. The cyclotron was designed and fabricated in 2007–2009 in NIIEFA (St. Petersburg, Russia) and delivered to the University of Jyvaskyla (Finland).