Fabrication and Testing of the 20 kA Binary Current Leads for the NHMFL Series-Connected Hybrid Magnet

A pair of binary vapor-cooled/high-temperature-superconducting current leads were fabricated at the National High Magnetic Field Laboratory (NHMFL) and tested at the High Field Magnet Laboratory (HFML) at the Radboud University Nijmegen. The leads supply current to the NHMFL series-connected hybrid magnet. Details of the fabrication are discussed, including that of the resistive and high-temperature-superconducting parts and the integration of the two sections. A test assembly was made, including the pair of current leads, a jumper made from NbTi cable-in-conduit, instrumentation, and mounting hardware. The test facility includes a liquid nitrogen supply vessel and a closed-loop supercritical helium supply system, to replicate the cooling used in the magnet assembly. Results from the testing of the leads to the full operating current, and under simulated loss-of-cooling conditions are presented.