Properties and flux pinning of Cu-Nb superconductors with nanometric-scale pinning centers

The introduction of normal phases into the superconducting phases is one of the most efficient forms to improve the pinning center densities and the critical current densities J/sub c/ of superconductors. Controlled generation of pinning centers with a projected distribution can contribute to estima...

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Bibliographic Details
Published in:	IEEE transactions on applied superconductivity Vol. 15; no. 2; pp. 3389 - 3392
Main Authors:	Rodrigues, D., Rodrigues, C.A., Silveira, E.B., Romao, E.G.M.
Format:	Journal Article Conference Proceeding
Language:	English
Published:	New York, NY IEEE 01-06-2005 Institute of Electrical and Electronics Engineers The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:	Applied sciences Artificial pinning centers COMPOSITES Copper Critical current density Cu-Nb CURRENT DENSITY Electrical engineering. Electrical power engineering Exact sciences and technology Fabrication FLUX PINNING FLUXES Force control Materials Niobium PHASES PINNING Proximity effect Proximity effect (electricity) Superconducting filaments and wires SUPERCONDUCTIVITY SUPERCONDUCTORS Temperature Tin transport properties Wire drawing Electric resistance measurement Critical current density Temperature dependence Scanning electron microscopy Flux line Nb3Sn Electrical conductivity Deformation Transport properties Optimization method Proximity effect Cu-Nb Meissner effect Composite material Optimization Artificial pinning centers Coherence length Electrical measurement Flux pinning Critical temperature Composite superconductor Comparative study
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Summary:	The introduction of normal phases into the superconducting phases is one of the most efficient forms to improve the pinning center densities and the critical current densities J/sub c/ of superconductors. Controlled generation of pinning centers with a projected distribution can contribute to estimate the pinning forces and mechanisms acting on the flux lines and to determine procedures to improve J/sub c/. The introduction of nanometric-scale Cu regions into the Nb filaments region during the fabrication of Cu-Nb (or Cu-Nb/sub 3/Sn) composite superconductors changes the properties of the superconducting phase, mainly due to the proximity effect. The present work shows the development and characterization of Cu-Nb composites prepared by successive bundlings followed by swaging and wire drawing, leading to dimensions of the Cu regions as small as 43 nm. The samples were characterized by SEM and by the measurements of electrical resistivity as a function of temperature, critical temperatures T/sub c/, J/sub c/ vs. H, and F/sub p/ vs. H, in different steps of deformation and different dimensions of Cu and Nb, in comparison to the superconducting coherence length /spl xi/. The results helped to determine the influences of the Cu presence and of the proximity effect on the superconducting properties, leading to important conclusions useful to the optimization of J/sub c/ in superconductors.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	1051-8223 1558-2515
DOI:	10.1109/TASC.2005.848915