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Description
We present the magnet design of an adjustable-field isochronous permanent magnet cyclotron concept, capable of accelerating protons to 18 MeV. Within the cyclotron, the permanent magnet is distributed about the cyclotron return yoke above and below the midplane in rotatable cones. With an outer radius of 1.36 m and height of 1.22 m, the design can replicate the field strength (up to 2.3 T peak) and pole gap of the IBA Cyclone(R) Kiube. We consider efficient application of permanent magnet material, and report the resulting, simulated magnetic field, RF frequency, rough estimate of total power and other properties of the machine. For use as a radio-pharmaceutical cyclotron, we find an 18F production target would cause much less activation in neodymium permanent magnets than in samarium-cobalt permanent magnets, resulting in a strong preference for using the former in such a cyclotron. The torque required to turn the permanent magnet cones to adjust the field is found to be below 2800 Nm, and no demagnetisation due to applied magnetic field is expected for the case of neodymium magnets.
