Feasibility Study of HTS Current Leads With MgB2 Shunt for Tokamak Application

Gas helium cooled HTS/MgB
₂
based hybrid superconducting current feeders system have potential benefits in terms of better temperature margin and cryo stability for superconducting tokamaks and accelerators. As a proof of principle, a hybrid current feeders system comprising of a 3.3 kA rated prototype HTS current leads (CL) pair equipped with a meter long in-house developed MgB
₂
shunt is recently tested at the Institute for Plasma Research (IPR). The prototype HTS CL and its bottom MgB
₂
shunt is tested up to the maximum rated current of 3.3 kA with a ramp rate up to 300 A/s. The heat exchanger (HX) part is cooled using liquid nitrogen (LN
₂
). The HTS module utilizes BSCCO-2223 tapes. The bottom MgB
₂
shunt section is cooled near 5 K–10 K using cold helium gas from a liquid helium Dewar. Prior to helium cooling, HX is pre-cooled to 80 K by utilizing LN
₂
that allows HTS module and bottom MgB
₂
shunt section conduction cooing thus optimizing and saving helium consumption. The scarcity of liquid helium in the market makes HTS/MgB
₂
based superconducting current feeders a prominent candidate for large scale SC magnets application. The integrated test set-up is equipped with necessary sensors and diagnostics for detailed characterization. The temperature distribution at various sections of CL are reported in detail under cold and charging conditions. Here, we report the detailed experimental characterization results for HTS CL equipped with MgB
₂
shunt under cold conditions. The main outcomes from the experiment are presented and discussed in detail.