HTS Conductors in Electromagnetic Systems of Future Fusion Facilities

Electromagnetic systems (EMS) of the largest and ambitious modern fusion scientific facilities, such as ITER—the most eminent international project under construction—rely upon a well-developed industry of low-temperature superconductor (LTS) wires. At the same time, a number of state and private research companies demonstrate increasing interest towards high-temperature superconductors (HTS) as a basic material for more compact EMS operating at a higher magnetic field. Two reasons underlie this interest. The first one is a huge progress in the development of HTS conductors confirmed by construction and tests of several magnets made with commercially available HTS wires, which demonstrate stable operation at a magnetic field beyond 30 T. The second reason is economical assessments of funds and time expenses needed for the construction of “thermonuclear power plants” in the future. The assessments have shown that optimal EMSs for such facilities should be compact (small-size), operate at a magnetic field at a level of at least 18–22 T and temperature of 10–25 K with a design current density of 70–100 A/mm2. Only high-temperature superconductors can show such performance. The construction of HTS systems requires attaining new solutions for traditional design problems and revising design criteria for major EMS elements such as winding conductors, joints, cryogenic, diagnostic, and protection systems, and insulation. Reflecting some technical solutions presented in open sources for such projects as SPARС and ST-HTS [1, 2] and taking into account the first results of theoretical and experimental programs performed in support of the conceptual design of a tokamak with reactor technologies (TRT) [3], the authors suggest discussion on the basic principal and design criteria of modern HTS EMS for fusion.