Magnetic design of an alternating gradient Canted-Cosine-Theta superconducting magnet for proton therapy

Canted-Cosine-Theta (CCT) magnets exhibit superior field quality and structural compactness in superconducting magnet schemes. When combined with an alternating gradient (AG) field, CCT magnets can be applied to proton therapy gantries to achieve a significantly increased momentum acceptance. This paper introduces design considerations for a 67.5 degree AG-CCT magnet for a proton therapy gantry, including the design and optimization of a magnetic field combined with an AG function. The calculation of the magnetic field used to simulate the CCT coil with multiple lines based on the Biot-Savart law is discussed in detail. Technical issues covering the choice of superconducting coils and layering scheme are also discussed.