US Patent 9271385 Magnetic structure for circular ion accelerator

A magnet structure for use in a circular ion accelerator, such as e.g. a synchrocyclotron comprises a cold-mass structure including superconducting magnetic coils (20, 25), at least one dry cryocooler unit (10, 11, 12, 13) coupled with the cold-mass structure for cooling the latter and a magnetic yoke structure (30) with a return yoke (35) configured radially around said coils (20, 25). The return yoke (35) comprises an opening in which said dry cryocooler unit (10, 11, 12, 13) is received so as to be in thermal contact with said cold-mass structure.