Development of forced flow cooled current leads for fusion magnets

During the past 15 years, the Institut fur Technische Physik of the Forschu ngszentrum Karlsruhe, Germany, has developed current leads cooled by forced -flow supercritical helium in the current range from 20 to 80 kA. The desig n is based on a separation of the current carrying part and the heat exchan ger part as well as the presence of the so-called superconductor inserts ma de of Nb3Sn wires inside the conductor in the heat exchanger area which all ows the operation of the current lead at minimum helium mass flow in a wide current range. The paper describes the design and construction of the curr ent leads as well as operation results obtained during various tests perfor med in the coil test facility TOSKA at the Forschungszentrum. Karlsruhe. (C ) 2001 Elsevier Science Ltd. All rights reserved.