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

Abstract

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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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.