Advanced magnet systems for fusion would greatly benefit from the use of high-temperature superconductors (HTS). The operation of compact fusion magnets at the high currents and fields needed to enable adequate plasma confinement and net energy output results in strong forces within the magnet windings. Advanced high-strength conductors are thus needed to enable the development of future HTS magnets for fusion systems. This proposal seeks to develop high-strength composite HTS Conductor on Round Core (CORC®) cables for fusion magnets. The approach is to develop and integrate advanced micro- composites within the non-superconducting CORC® cable core, which is normally made up of a solid metallic conductor, to double or even triple the conductor strength without sacrificing the normal-state conductivity of the cables that is important for magnet protection. During Phase I of the program, we will develop advanced CORC® cables with integrated metallic micro-composites. Mechanical and conductivity measurements of the composites will be performed at cryogenic temperatures and compared to other metals and alloys. Short high-strength composite CORC® cables will then be manufactured and mechanical and conductivity measurements will be performed and compared to typical CORC® cables. An additional design optimization and testing step will be used to develop a much more robust fusion magnet cable. During Phase II, we will expand the conductor development to exceed an irreversible stress of 500 MPa. The final goal of the Phase II program will be the demonstration of a higher strength self-supporting CORC® coil tested under the combination of high currents and backgroundfields of 14 T, resulting in a hoop stress of over 400 MPa. High-strength composite HTS CORC® Cables will enable high-field HTS magnets capable of operating at high currents, high stress levels, and even at elevated temperatures. This allows development of the next generation of fusion magnets, accelerator magnets for high-energy physics experiments, proton cancer treatment facilities and scientific magnets. These magnets will also benefit superconducting magnetic energy storage systems for use in the power grid and within the Department of Defense.
