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) current leads 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 K to 80 K. HTS module is based up 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 a 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 are then reported and discussed in detail.