High-current Density CORC® Wires for Use in Accelerator Magnets

Accelerator magnets that are currently being used in high-energy physics experiments are limited to a maximum magnetic field of less than 20 T because superconductivity in the low- temperature superconductors from which the magnets are constructed breaks down at higher fields. The next generation of accelerator magnets needs to be made from high-temperature superconducting magnet cables. The requirement of operating these fragile materials at high current densities while experiencing high stresses makes this very challenging. This proposal seeks to develop high-temperature superconducting CORC® magnet wires that would have a current density of 600 A/mm2 and a critical current of 10 – 20 kA at 4.2 K and 20 T, and bendable to 30 mm diameter, which would enable the next generation of accelerator magnets that operate at 20 T and above. During Phase I of the program, we will develop the next generation of highly flexible CORC® wires from superconducting tapes with 25 m thick substrates. We will ensure that the CORC® wires retain at least 80 % of the performance when bent to a diameter of less than 50 mm and have a current density of 400 A/mm2 and critical current exceeding 5 kA at 20 T. During Phase II, the CORC® wire performance will be increased to 600 A/mm2 with critical current exceeding 8 kA at 20 T by winding them from even thinner tapes with substrates as thin as 20 m. At the same time, the flexibility of CORC® wires will be increased to allow bending to a diameter of 30 mm. Commercial applications and other benefits: High-temperature superconducting magnet wires that have a high current and high current density at 20 T, while being bendable to diameters less than 30 mm, will enable some of the next generation of high-energy physics magnets, proton cancer treatment facilities, practical fusion magnets, 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.