Fabrication of HTS Conductor Stacks for 20-kA Binary Current Leads for MagLab Series-Connected Hybrid and HFML Nijmegen Hybrid Magnets

The MagLab series-connected hybrid and the HFML Nijmegen hybrid outer superconducting coils each require a pair of binary current leads, comprised of a nitrogen vapor-cooled resistive section and a high-temperature superconducting (HTS) section, configured to minimize the heat load to the coils. The HTS sections of both pairs of leads are made with stacked and soldered Bi-2223 tapes supplied by Sumitomo. The MagLab fabricated and tested the tape stacks for both programs. The procedures and apparatus for fabricating the stacks and making the critical current measurements are described. Critical current and n-value measurement results are reported.