Showing papers by "Michael Tinkham published in 1981"
47 citations
TL;DR: In this paper, a review of in situ formed multifilamentary composites is presented and their superconducting and mechanical properties are discussed in terms of the underlying physical mechanisms, including strengthening, fluxpinning and coupling mechanisms.
Abstract: Recent developments on in situ formed multifilamentary composites are reviewed and their superconducting and mechanical properties discussed in terms of the underlying physical mechanisms. The evidence is presented for a strong size dependence of the strengthening, flux-pinning and coupling mechanisms and, in turn, the composite normal-state and superconducting transport properties. The importance of the composite microstructure and micro-geometry is illustrated with data on Cu-Nb, Cu-Nb 3 Sn and Cu-V 3 Ga conductors. In particular densely spaced interfaces are shown to interact effectively with both matrix crystal dislocations and flux-line lattice, resulting in strongly anisotropic material properties. The importance of the proximity-effect coupling is discussed for Nb 3 Sn-based composites below the microstructural percolation threshold where the self-field critical current densities (normalized to the filament volume fraction) reached values of 1.4 × 107A/cm2. At high fields, the performance of Cu-V 3 Ga in situ composites is significantly better than that of Cu-Nb 3 Sn conductors, with typical normalized values of J c of 1.4 × 107A/cm2at 18 Tesla and 4.2 K. Possible use of Cu-Nb in situ composites in high-field magnet design is also discussed in view of their remarkable strength (up to 2.9 GPa at 77 K) and high normal-state conductivity.
26 citations
TL;DR: In this article, the upper critical field of NbCu in situ formed tape composites was measured and found to be anisotropic, in good agreement with the predictions of the Ginzburg-Landau model.
Abstract: We have measured the upper critical field of NbCu in situ formed tape composites and found it anisotropic. The angular dependence of Hc2 is in good agreement with the predictions of the anisotropic Ginzburg-Landau model.
4 citations
TL;DR: In this paper, it was shown that the behavior of high resistance/square (R ▱ ) clean superconducting films near the thickness at which electrical conduction begins is dominated by a few paths across the film and thus should not be interpreted as a Kosterlitz-Thouless transition.
Abstract: Superconducting films with high resistance/square (R ▱ ) have been widely studied as a model of the Kosterlitz-Thouless transition. We show that the behavior of high R ▱ clean films near the thickness at which electrical conduction begins is dominated by a few paths across the film and thus should not be interpreted as a Kosterlitz-Thouless transition. Instead, this behavior is consistent with a simple percolation model for the connectivity fluctuations across the film.
2 citations