Test Results of a Prototype HTS Current Lead With MgB2 and NbTi Superconducting Joints

Conventional vapor cooled current leads (CL) based on low-temperature superconductor are the major consumer of liquid helium in large-scale superconducting magnets-based nuclear fusion devices. Use of conduction-cooled, high-temperature superconductors (HTS) CL enable operation up to 80 K and saves significant cold capacity of cryo plant. Recently at Institute for Plasma Research, India, a 3.3 kA rated prototype HTS CL pair is developed with the help of Indian industries. It exploits various superconducting materials operating from 5 to 80 K. HTS module is based on commercially available rare earth cuprate oxide superconductor based BSCCO-2223 tapes. For testing purpose, we have developed bottom lap joints using composite magnesium diboride (MgB
₂
) wires as an intermediate between HTS module and NbTi: Cu cable that act as a shunt between CL pair. Such a hybrid concept is adopted as the next step to developing MgB
₂
superconducting current feeder which could be operated near 20 K and save cryogenic cost in future fusion machines. Here, we report the salient features, basic details of HTS CL, superconducting joints fabrication, its test set-up, and experimental results. The inference from test results is then reported and discussed in detail.