As the second-generation synchrotron of therapy facilities for cancer treatment, rapid-cycling synchrotrons (RCSs) can meet the requirement of growing patient numbers. Supeferric magnets employing high temperature superconducting (HTS) coil windings and iron cores have potential to reduce the construction cost and electricity consumption for practical RCSs. However, AC loss generated in the HTS coil windings when carrying AC current increases significantly due to the presence of iron cores, making AC loss reduction a critical issue for HTS RCS application. Therefore, developing methodologies for AC loss reduction in the HTS coil windings coupled with iron cores is an urgent task for HTS RCS application.In this work, we carry out 3D FEM (Finite element method) AC loss simulations in HTS coil assemblies coupled with an iron core by using the T-A formulation. The HTS coil assemblies are comprised of double pancake coils (DPCs) wound with coated conductors manufactured by Shanghai Superconductor Co. with an average self-field Ic of 193 A. Flux diverters are positioned at the ends of the HTS windings to suppress the perpendicular magnetic field to the wide-face of coated conductors in the end part of the coil windings, and the distance between the iron core and coil assemblies is varied to investigate AC loss dependence on the distance. The simulated AC loss values in the HTS windings are compared.Acknowledgments:This work was supported in part by the New Zealand MBIE under Contract No. RTVU1707 and in part by the SSIF “Advanced Energy Technology Platforms” under Contract No. RTVU2004. Yue Wu acknowledges financial supports from the CSC and the CSC/Victoria University of Wellington Scholarship.

Keywords: AC loss, iron core, superconducting coils, 3D T-A homogenization method