Continuous- and batch-processed MgB2/Fe strands -: transport and magnetic properties

The tube filling/forming powder-in-tube (PIT) technique was employed at Hyper Tech Research for the continuous processing of MgB2/Fe composite strand. Demonstration lengths of up to 70 m of 1.2 mm diameter precursor strand-an Fe-clad Mg + B elemental powder mixture-have so far been produced. Short samples of this strand, heat treated for 3-30 min/800-950 degreesC, have yielded transport critical current densities (J(c)) of 2-3 x 10(4) A/cm(2) at 4 K/4 T, 4 x 10(4) A/cm(2) at 4 K/2 T, and at 4 K in self field an extrapolated J(c) of at least 2 x 10(5) A/cm(2). Batch-processed PIT MgB2/Fe strands and tapes were made at the University of Wollongong's Institute for Superconducting and Electronic Materials. These were the focus of magnetization- and magnetic-shielding studies. Depending on the thickness of the Fe sheath, the superconducting core could be completely shielded at low fields (e.g. below 2 kOe). Taking this into account, the magnetic J(c) is extracted, and found to be comparable to the extrapolated transport value. (C) 2002 Elsevier Science B.V. All rights reserved.