Performance of a Test Coil Wound From Defect-Tolerant Second-Generation Cable

Here, we report the performance of a coil wound from a defect-tolerant superconducting cable. The cable is comprised of a stack of four 2 mm wide filaments. The defect tolerance is achieved by continuous current sharing between the filaments. The current sharing is assisted by fusing the filament with a directed hot air stream during the winding process. To demonstrate the defect tolerance, each of the four filaments in the cable was cut on purpose, resulting in the superconducting layer breakage every 1.2 meters. The coil was tested in a magnetic field up to 1 T at 77 K, and at 4.2 K. We show that despite discontinuities in each of the filaments, the winding demonstrated no dissipation below the critical current down to the level of 10 nV over 5 meters of winding. We propose the design of a multi-filamentary cable that would be tolerant to current blocking defects several meters apart. Finally, we propose a standard for defect-tolerance of a multi-filamentary second-generation cable.