Field and temperature dependence of critical currents in industrially manufactured high-Tc wires and tapes

In the frame of the European Fusion Technology Programme, CRPP Villigen evaluated the performance of currently available commercial High-Tc wires and tapes in view of their suitability for magnet coils in future fusion reactors. We measured the critical current of Bi-2212 round wire and Bi-2223 tapes from two different manufacturers at temperatures up to 77 K. Magnetic fields up to 12 T were applied parallel as well as normal to the plane of the tapes (always normal to the current direction) to investigate the materials' anisotropy. At temperatures up to about 50 K and in sufficiently high fields we observed that the critical current decreases exponentially with the magnetic field in the 2223 tapes. In the same regime the Ic values were significantly different for increasing and decreasing field (hysteresis), most likely related to the different magnetisation states of the samples and therefore the local magnetic fields at the grain boundaries. High-Tc tapes and particularly round wires are promising candidates for conductors in fusion magnets because of their excellent high-field properties. They also show potential for the use at temperatures above 4.2 K in the 12 to 15 T range if cooling between 20 and 50 K became an attractive alternative to helium-based refrigeration. Our measurements show that the required current densities are already available industrially