Magnetic field dependence of the critical current in MgB2 and Bi-2223 superconducting tapes fabricated by the powder-in-tube method

The transport properties of powder-in-tube processed superconducting tapes based on the Bi-2223 and MgB₂ compounds were measured at liquid helium temperature as a function of the magnetic field amplitude and orientation with respect to the conductors. Critical current measurements on short samples were performed in a magnetic field up to 20 T. From this data, we found that commercial multifilamentary Bi-2223 tapes, in spite of the well-established processing route, show some differences over a standard common trend, if manufactured by different suppliers. Nevertheless they all carried remarkable transport currents up to the highest magnetic field of measurement. The transport properties of MgB₂ tapes presented very different features depending on the thermo-mechanical treatment they were subjected to during the fabrication process. A small critical current was measured at a field as high as 16 T on a multifilamentary MgB₂ tape. In the magnetic field domain below 1 T, MgB₂ tapes carried critical currents in excess of 1000 A at a critical current density of greater than 4·10⁵ A/cm².