High-temperature superconducting (HTS) magnets are widely regarded as the technology that could make compact, economically viable fusion power plants possible—but only if engineers can solve a layered set of problems spanning the superconducting tape itself, the immense forces inside each coil, and the interactions of a complete magnet system inside a reactor. A 2018 white paper by researchers from MIT, Princeton Plasma Physics Laboratory, Lawrence Berkeley National Laboratory, and Oak Ridge National Laboratory describes HTS as a "new game changing opportunity" that could significantly advance the economic and technical status of magnetic confinement fusion. Turning that opportunity into hardware is the hard part.
The Game-Changing Potential of HTS Magnets for Fusion
The physics case is straightforward: stronger magnetic fields confine a denser, hotter plasma, so a reactor can produce the same fusion power in a smaller volume. A Fusion Nuclear Science Facility design study, published through the Department of Energy's Office of Scientific and Technical Information, notes that HTS has been identified in the recent community plan for fusion energy as the potential game changer for enabling higher fusion power density and a smaller device size for that facility and future fusion pilot plants.
The material advantage is real. According to a superconducting magnet research white paper hosted by Princeton Plasma Physics Laboratory, REBCO-family compounds exhibit very high critical currents at temperatures well above that of boiling liquid nitrogen at 77 K, whereas the commonly used low-temperature superconductors NbTi and Nb3Sn must operate near the temperature of liquid helium. Higher operating temperatures and higher current-carrying capacity at high field are what allow designers to shrink the machine. But the same study is blunt that enabling high-field HTS magnets remains one of the main engineering challenges for optimizing machine size and system performance of advanced tokamaks.
