Preliminary Conceptual Design Study on HTS Toroidal Field Coil for Compact High Magnetic Field Tokamak

By rapid development of high temperature superconductors (HTS), the HTS magnet has become an enabling technology for compact, high magnetic field tokamaks requiring larger current densities and higher magnetic fields where low temperature superconductors (LTS) have limitations. Thus, a preliminary conceptual design study on HTS magnet for toroidal field (TF) coil, a major component of compact and high field tokamak, is presented to investigate the possibility of the use of an HTS. General features relevant to a large-scale superconducting magnet are discussed such as electromagnetics, mechanical stress, protection, and cryogenics. Two types of HTS tapes are used to design TF coils for a tokamak that targets 9.2 T at its major radius 3.3 m: 1) Design A, using an HTS tape used in previous high field HTS magnets; and 2) Design B, using the same HTS tape with twice the performance. The results convey the possibility of HTS TF coil with currently available technology, but with the expense of a large amount of HTS tapes inferring that a reduction in the HTS tape cost is required. Improvement on the HTS TF coil design is needed using the unique characteristics of HTS. Hence, some of the challenges for HTS fusion magnet are addressed including performance degradation of conductors, quench detection and protection method, and joint for demountable TF coil.