Design and fabrication of a 70 kA current lead using Ag/Au stabilized Bi-2223 tapes as a demonstrator for the ITER TF-coil system
In the frame of the European Fusion Technology Programme, the Forschungszentrum Karlsruhe and the Centre de Recherches en Physique des Plasmas, CRPP, Villigen, develop a 70 kA current lead to demonstrate the feasibility of the usage of High Temperature Superconductors (HTS) for the current leads of the ITER TF coils. Design and fabrication of the conventional heat exchanger that covers the temperature range from 65 K to room temperature is done at the Forschungszentrum Karlsruhe. The HTS module connects the current feeder terminal at 4.5 K with the conventional heat exchanger and is cooled only by heat conduction from the cold end. Its design and fabrication has been performed by American Superconductor, AMSC. This module consists of Bi-2223 Ag/Au tapes embedded in stainless steel carriers with copper end caps. It is highly instrumented with voltage taps, temperature sensors and Hall probes. The integration with the heat exchanger and the current feeder terminal is carried out at the Forschungszentrum Karlsruhe. The current lead will be tested in the TOSKA facility in the first months of 2004. The paper describes the design, fabrication and results of pretests carried out at AMSC and Forschungszentrum Karlsruhe.