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In this contribution, different concepts for mechanically reinforced MgB2 wires with high transport currents are presented and characterised. It is shown that the achieved critical transport currents depend strongly on the conductor concept, the choice of the precursor route and the applied treatment method., Comment: 17 pages, 13 figures, to be published in "Studies of High Temperature Superconductors, Vol. 45", edited by A. Narlikar (Nova Science Publishers, N.Y., 2002)

Monofilamentary MgB2-wires with a 2- or 3-component sheath containing mechanical reinforcing stainless steel (SS) were prepared and characterized. In direct contact to the superconductor Nb, Ta or Fe was used. For a selection of samples with a Fe and Fe/SS sheath, we investigated the transport critical current behaviour in magnetic fields changing systematically the geometrical shape from a round wire to a flat tape. A strong increase of the current densities in flat tapes was observed and possible reasons for this are discussed. Reinforcing the sheath in the outer layer with different amounts of stainless steel leads to a systematic field dependent decrease of the transport critical current density with increasing steel amount. This is an indication for a pre-stress induced degradation of the critical currents in MgB2 wires and first Ic-stress-strain experiments seem to confirm this observation and interpretation., Comment: 12 pages, 5 figures. Submitted to Physica C (Proceedings of EUCAS 2001)

We prepared and characterized monofilamentary MgB2 wires with a mechanically reinforced composite sheath of Ta(Nb)/Cu/steel, which leads to dense filaments and correspondingly high transport currents up to Jc = 10^5 A/cm^2 at 4.2 K, self field. The reproducibility of the measured transport currents was excellent and not depending on the wire diameter. Using different precursors, commercial reacted powder or an unreacted Mg/B powder mixture, a strong influence on the pinning behaviour and the irreversibility field was observed. The critical transport current density showed a nearly linear temperature dependency for all wires being still 52 kA/cm^2 at 20 K and 23 kA/cm^2 at 30 K. Detailed data for Jc(B,T) and Tc(B) were measured., Comment: 21 pages, 13 figures, revised version, to be published in Supercond. Sci. Technol