Current transfer in MgB₂wires with different sheath materials

Abstract

The current transfer length in composite MgB2 wires with different metallic sheaths and filament numbers was analysed. The electric potential gradient along the wire in the vicinity of the current contact was monitored as a function of transport current in various external magnetic fields up to 14 T. In all samples the characteristic current transfer length is of the order of a millimetre, varying with detailed sheath composition in the range 0.35–2 mm. For the wires with a clear reaction layer at the filament/matrix interface, the electrical resistivity of the material constituting such a barrier was estimated.

Intra wire resistance and strain affecting the transport properties of Nb3Sn strands in cable-in-conduit conductors

“…Such a short current transfer length is in agreement with similar observations reported by Ekin [124]. According to the classical analytical model [130] and based on our intra-strand resistance data, the current transfer length is less than 0.1 mm.…”

“…From current transfer length measurements on Fe-sheathed MgB 2 wires [130], R was found to lie in the range ~2 to 6×10 11 Ωm 2 , which is even one order of magnitude higher than our results. For BSCCO, a range is given for R .…”

“…A number of well-established techniques allow measurement of the interfilament transverse resistance indirectly, in particular the determination of the selffield distribution [125]- [127]; the AC coupling losses at low frequency [119], [127]- [129]; and the current transfer length [130], [131]. However, these indirect methods yield an average transverse resistivity that comprises both matrix resistance and filament-to-matrix contact resistance.…”

Coupling currents and hysteresis losses in MgB2superconductors

“…In several studies, the contact resistance has been found to be significant for MgB 2 wires and to strongly vary between samples with different matrices [19][20][21]. In addition to the losses appearing in the metal matrix, the coupling currents influence the hysteresis losses.…”

Direct Measurement of Inter-Filament Resistance in Superconducting Multifilamentary NbTi and ${\rm Nb}_{3}{\rm Sn}$ Strands

“…Several methods were developed to assess the inter-filament transverse resistance, such as measurements of the self-field distribution [4], [5]; of the AC coupling losses at low frequency [3], [6], [7]; and of the current transfer length [8]. However, the outcome of these indirect measurement methods depends on sample shape, internal wire structure, outer copper shell, Cu/nonCu ratio and twist pitch [9].…”