Assessment of the performance of a 20 kA REBCO current lead

In the framework of a worldwide effort investigating the design of high-current High Temperature Superconductor (HTS) current leads (CLs) composed of REBCO, a 20 kA HTS CL developed at the Karlsruhe Institute of Technology (KIT) based on the JT-60SA CL design, but replacing the Bi-2223 tapes by brass-stabilized REBCO tapes, has been recently tested in the CuLTKa facility at KIT to investigate its steady state and transient performance. The thermal-hydraulic CURLEAD code developed at KIT, recently upgraded in a collaboration between KIT and Politecnico di Torino and validated in both steady state and transient (pulsed) operation, was applied predictively, i.e. before the tests were performed, to support the test strategy of the REBCO CL, which is presented here. The prediction was used to define the set point for the steady state tests, both with and without current, while transient simulations were used to define the number of current pulses needed to reach periodic operation conditions for given current waveforms. The comparison between predictions and experimental results is presented here, showing good agreement between the two in all operating conditions. Interpretive simulations, which took into account the experimental results of parameters, like, e.g., the contact resistance of the HTS module to both the heat exchanger and the cold end copper, are finally presented, showing as expected an even better capability to reproduce the experimental traces, giving confidence in the reliability of CURLEAD for future applications.