Development of CORC® wires for use in canted cosine theta 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 enable the next generation of accelerator magnets that operate at 20 T and above. They will be tailored for use in canted cosine theta accelerator magnets, which is a design in which the stresses on the conductor are limited. During Phase I of the program, we will develop CORC® wires with a current density of at least 300 A/mm2 at 4.2 K and 20 T, while ensuring that they retain at least 80 % of the performance when bent to a diameter of less than 40 mm. We will design a canted cosine theta insert magnet based on CORC® wires, which would be operated inside an outsert made from low temperature superconductors, with the goal to increase the total magnetic field to at least 20 T. The CORC® wire performance will be increased to 600 A/mm2 at 20 T and several prototype canted cosine theta insert magnets will be constructed and tested during Phase II of the program. The development of high current density magnet wires made from high-­‐temperature superconductor and magnets wound from these wires is necessary for the US to maintain their leadership position in superconductivity research, materials science, and high-­‐energy physics research. Commercial Applications and Other Benefits: High-­‐temperature superconducting magnet wires that have a high current density at 20 T, while being bendable to diameters less than 40 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 for application within the Department of Defense.