Compact Rare-Earth Superconducting Cyclotron

A method for accelerating an ion in a cyclotron, comprising:

• injecting an ion into a chamber defined inside a magnetic yoke at an inner radius;
• providing a voltage from a radiofrequency voltage source to an electrode in the chamber to generate an oscillating field from the electrode that accelerates the ion in an outwardly spiraling orbit across a median acceleration plane;
• using a cryogenic refrigerator to maintain (a) superconducting coils on opposite sides of the median acceleration plane and (b) rare-earth poles at a temperature at or below that at which a rare-earth metal of the rare-earth poles transitions to a ferromagnetic state, wherein the rare-earth poles are separated by a gap of least 5 cm across the median acceleration plane and physically separated from the magnetic yoke across the median acceleration plane;
• providing a voltage to the superconducting coils to generate superconducting current in the superconducting coils, wherein the superconducting coils magnetize the rare-earth poles and the magnetic yoke, and wherein the superconducting coils, the rare-earth poles, and the yoke generate a radially increasing magnetic field in the median acceleration plane that accelerates the ion in an outwardly spiraling orbit from the inner radius to an outer extraction radius;
• and
• extracting the accelerated ion from the chamber at the outer extraction radius.