The transport critical current density, JC, was measured at 4.2K for MgB2 monofilamentary and 7-, 19- and 37-stack multifilamentary strands. Simple, one-step heat treatments (HT) were used, with temperatures of 675 and 700C, and times from 10 to 40min. Most measurements were performed on 1m segments of strands wound onto barrel holders. Transport properties of monofilament, 7-, 19- and 37-stack strands were compared, and the influence of CuNi and monel outer sheaths was investigated. HT optimization studies were performed on various strands. Transport JC values of 0.8mm OD strands reached 2 x 105A/cm2 at 4T and 4.2K (1µV/cm), and 1.15 x 106A/cm2 at 4.2K and zero field. Smaller 10-filament wires with ODs as small as 0.25mm (40µm filaments) exhibited good performance in some cases. The temperature and field dependences of the transport JC were also measured; a typical example was 2 x 104A/cm2 at 4K, 20T.

Transport Properties of Multifilamentary, in situ Route, Cu-Stabilized MgB2 Strands - One Metre Segments and the JC(B,T) Dependence of Short Samples. M.D.Sumption, M.Bhatia, M.Rindfleisch, M.Tomsic, E.W.Collings: Superconductor Science and Technology, 2006, 19, 155-60