An approach for faster high field magnet technology development

The Superconducting Magnet Program at LBNL has developed a magnet design supporting our new Subscale Magnet Program, that facilitates rapid testing of small superconducting racetrack coils in the field range of 10-12 Tesla. Several coils have been made from a variety of Nb₃Sn/Cu cables, insulated, wound, reacted, potted and assembled into a small reusable yoke and shell loading structure. Bladder and key technology have provided a rapid and efficient means for adjusting coil pre-stress during both initial assembly, and between thermal cycles. This affords the opportunity to test moderately long rectangular cable samples under "magnet conditions" on a time scale considerably closer to that for traditional short-sample cable tests. We have built and tested four coils with the initial aim of determining the feasibility of reducing overall conductor costs with "mixed-strand" cables. Details of cost reduction improvements, coil construction, magnet structure, and assembly procedures are reported, along with the relative performance of the mixed-strand coil.