Electrodynamic analysis of HTS conductors for fusion magnets and for non insulated coils

The advent of high-temperature superconducting (HTS) materials has ushered in a new era of technological possibilities, propelling them to the forefront of cutting-edge scientific endeavors. HTS devices are frequently subjected to time dependent transport currents and external magnetic fields during operation, leading to energy losses within the HTS, namely AC losses, a phenomenon that can potentially compromise device performance. Accordingly, the development of robust tools for accurately estimating AC losses in HTS devices and predicting the behavior of the device during operation is of crucial importance. Conventional approaches, such as finite element method (FEM) models, offer commendable predictive capabilities, yet they suffer from substantial computational costs and are often not compatible with the time scale of the design and prototyping phases of HTS device development. The computational time of 3D FEM models is prohibitively high in the cases of complex magnet geometry like the central solenoid of a Tokamak fusion reactor. To address this limitation, this thesis investigates alternative solutions: analytical formulae for the assessment of the instantaneous power dissipation, which were applied to study the losses in the central solenoid of the DEMO machine, and a 3D lumped parameter model employed in the study of tapes and no insulation HTS (NI-HTS) coils. The proposed solutions, although not accurate as a full 3D FEM model which remains the most reliable tool for the analysis of HTS devices, offer significant advantages over conventional approaches. The main advantages are reduced computational time, enhanced model flexibility, and improved scalability for complex device geometries.