Test results of a 10 kA current lead using Ag/Au cladded Bi-2212 tubes [for ITER-FEAT coils]

In the frame of the European Fusion Technology Programme, the Forschungszentrum Karlsruhe (FZK) and the Centre de Recherches en Physique des Plasmas (CRPP) are developing a 70 kA current lead for the toroidal field coils of the International Thermonuclear Reactor (ITER-FEAT) using high-temperature superconductors (HTS). As a part of this task, two 5 kA HTS modules made of Bi-2212 bulk material cladded with an Ag/Au sheath have been ordered in the industry. The two HTS tubes were connected in parallel forming a 10 kA current lead that has been tested at CRPP. In addition to the steady state performance, the thermal transient behavior for loss of flow in the gas-cooled copper part has been studied. A special feature of the test equipment are small Hall probes providing information on the current distribution in the two HTS tubes. In spite of a considerably uneven current distribution the current lead could be safely operated in steady state at the nominal current of 10 kA.