It was recalled that, in mono- and multifilamentary wires with small diameters, an homogeneous and fine-grained phase was required for high transport currents while reaction with the sheath had to be avoided. Taking this into account, very thin steel-reinforced MgB2 wires were developed. In situ phase formation in the wire from Mg+B powders was chosen to be the most favourable method for achieving good grain connectivity and high transport currents. The current lead wires were tested by using transport current measurements, and the mechanical performance was investigated by using applied tensile and bending strains. With an improved processing route, and applying low-temperature annealing, the superconducting properties of standard undoped in situ MgB2 wires could be further improved and critical current densities of 38kA/cm2 at 6T and 10kA/cm2 at 8T, 4.2K could be achieved.

Development and Performance of Thin Steel Reinforced MgB2 Wires and Low-Temperature in situ Processing for Further Improvements. W.Goldacker, S.I.Schlachter, B.Obst, B.Liu, J.Reiner, S.Zimmer: Superconductor Science and Technology, 2004, 17, S363-8