A New Algorithm for Optimizing the Field Quality of Curved CCT Magnets

While the required coil geometry for a specified transverse field pattern of straight canted-cosine-theta (CCT) magnets is well known, the same geometry—after the application of a bending transformation—would introduce unwanted field components in a magnet with a strong curvature. In this article, we introduce a coherent framework to define the field quality in curved magnets, and to construct the required 3-D winding geometry of CCT coils, without finite-element software. The method is applicable in general for any magnet configuration where the effective longitudinal current density distribution in the transverse plane can be related to the winding geometry in a unique way. The method is demonstrated on CCT magnet models being developed for the Heavy Ion Therapy Research Integration Plus European H2020 project.