Development of a 20 kA high temperature superconductor current lead

The reduction of static heat load in superconducting magnet systems is of great importance because of reduction of refrigeration power and operational costs. The major elements that determine the heat load are the current leads. The use of high temperature superconductors (HTS) in current leads was found to have great advantages because of the low thermal conductivity of the HTS material as well as the capability of carrying transport current without resistive losses if operating below the critical temperature. In the framework of the European Fusion Technology Programme, a development program has been carried out for design and construction of a 68 kA current lead for the toroidal field (TF) coils of the International Thermonuclear Experimental Reactor, ITER, using HTS. The material selection, based on test results of I kA current leads, favoured the use of Bi-2223 stabilized tapes because of the higher thermal stability. Two 10 kA HTS modules were manufactured in industry and tested in a test facility at CRPP. Subsequently, the two 10 kA HTS modules were connected in parallel to form a 20 kA HTS module, The performance test covered the electrical and thermal behaviour in both steady-state and transient operation. Current sharing was observed between two modules in the 20 kA current lead and the quench current was evaluated to about 30 kA at the design conditions. The results suggest that it is possible to satisfy all requirements needed for the current leads of the ITER TF coils if the scale-up of this HTS current lead is performed with the same design concept. (C) 2001 Elsevier Science Ltd. All rights reserved.