DESIGN, CONSTRUCTION AND DEVELOPMENT OF AN APPARATUS FOR THE TRANSPORT-CURRENT CHARACTERIZATION OF HIGH-TEMPERATURE SUPERCONDUCTORS AT A RANGE OF TEMPERATURES AND MAGNETIC-FIELDS

In this paper we describe the development of an apparatus based on an original design for conventional superconductors by Hudson et al.1 and improved by Hampshire and Jones2 . The latter is capable of measuring critical currents up to 500 A in fields up to 16 T at a range of temperatures from 2.2 K to around 20 K. This is a preliminary effort at extending the temperature range to enable the characterization of high-temperature superconductors across the full J - T plane and in fields up to 18 T. Full thermodynamic consideration is given, along with a treatment of magnitude and sources of error. Silver-clad superconducting wire in short sample coil format is investigated, with comments on the limitations of the apparatus thus observed. Representative results are discussed with reference to the disputed 'flux-lattice melting' effect occasionally observed in bulk samples of BiSCCO on inorganic substrates3, and in short (< 3 cm) lengths of silver-clad BiSCCO4,5. It is speculated that the use of silver-clad BiSCCO in lengths between 10 and 100 cm, requiring significant transport currents, may help clarify the process of current transport and magnetic flux pinning.