Analytical Modeling of Magnetization Losses in Twisted Stacked HTS Conductors

The European post-ITER fusion demonstrator reactor (DEMO) design activities have been ongoing for several years in the framework of the EUROfusion Consortium. The designs proposed for the DEMOnstration Fusion Power Plants (DEMO) magnets include options based on high-temperature superconducting (HTS) technology, namely as an Insert in the Central Solenoid (CS). This work describes the development of tools for the calculation of magnetisation losses in a twisted-stacked HTS cable, which represents one of the most promising configurations of HTS fusion Cable-in-Conduit conductors (CICC). This geometry cannot be tackled with the straightforward application of 1D or 2D models, given their inability to describe the twisting of the tape stacks. However, the methodology proposed in this work allows one to treat the twisting of the conductors by discretizing them in a set of straight pieces. A set of analytical equations is developed to compute the instantaneous power losses in the slab approximation. This fast, easy-to-use, open-access tool, can be employed for the computation of AC losses in the central solenoid modules of a tokamak. In particular, we have applied the model to study the HTS insert of the DEMO central solenoid.