Local Measurement of Current Density by Magneto-Optical Current Reconstruction in Normally and Overpressure Processed Bi-2223 Tapes

Magneto-optical current reconstruction has been used for detailed analysis of the local critical current density (Jc) variation in monocore Bi-2223 tapes. We find, even in high quality tapes with bulk transport Jc ~ 40 kA/cm^2 (77K, 0T), that there exist local regions which possess current densities of more than 200 kA/cm^2. Overpressure processing at 148 bar significantly improved Jc to 48 kA/cm^2 by improving the connectivity. For the overpressure-processed sample we find that the current distribution is more uniform and that the maximum local current density at 77 K is increased almost to 300 kA/cm^2.Comment: Presented at Applied Superconductivity Conference, Houston, August 4th -9th, 200

Development of high critical current density in multifilamentary round-wire Bi2Sr2CaCu2O8+x by strong overdoping

Bi2Sr2CaCu2O8+x is the only cuprate superconductor that can be made into a round-wire conductor form with a high enough critical current density Jc for applications. Here we show that the Jc(5 T,4.2 K) of such Ag-sheathed filamentary wires can be doubled to more than 1.4x10^5 A/cm^2 by low temperature oxygenation. Careful analysis shows that the improved performance is associated with a 12 K reduction in transition temperature Tc to 80 K and a significant enhancement in intergranular connectivity. In spite of the macroscopically untextured nature of the wire, overdoping is highly effective in producing high Jc values.Comment: 4 figure

Disorder effects on the superconducting properties of BaFe1.8_{1.8}Co0.2_{0.2}As2_2 single crystals

Single crystals of superconducting BaFe$_{1.8}$Co$_{0.2}$As$_2$ were exposed to neutron irradiation in a fission reactor. The introduced defects decrease the superconducting transition temperature (by about 0.3 K) and the upper critical field anisotropy (e.g. from 2.8 to 2.5 at 22 K) and enhance the critical current densities by a factor of up to about 3. These changes are discussed in the context of similar experiments on other superconducting materials

Artificial pinning centers in MgB2 superconducting bulks

The optimization of MgB2 superconducting properties is extremely important for practical application. The introduction of an effective artificial pinning center in this material can enhance its critical current density efficiently. In this paper, VB2 is described as a material that provides effective pinning in the MgB2 bulks. The simultaneous addition of SiC as a carbon source is also analyzed. The samples were prepared using ball milling under a controlled atmosphere and heat treatment with a continuous argon flux. As a result, the superconducting properties could be optimized due to the effective improvement in the pinning behavior as well as with the carbon doping.Fil: Da Silva, L.B.S.. Universidade de Sao Paulo; BrasilFil: Serquis, Adriana Cristina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Bariloche.; ArgentinaFil: Hellstrom, Eric. Florida State University; Estados UnidosFil: Rodrigues, D.. Universidade de Sao Paulo; Brasi

Investigation of Optimal Approaches to Assessing the Megacity Innovative Potential

The authors of the article set a goal to identify the most accurate and economical methods for assessing the innovative potential of megacity in terms of the used resources. For that purpose, methods were selected, calculations were carried out for two of them, which were suitable for the goal and described in detail in the methodological literature. The results of two other methods presented in the public domain for comparable periods of time for three selected regions were used. The study used materials from Russian and foreign sources. Based on the results of the work done, certain conclusions were made that allow a more accurate selection of methods for assessing the innovative potential of cities, considering the objectives of such an assessment, as well as the resource availability of a group of researchers. A critical view is also presented on the further application of all methods, which requires researchers of the local innovation potential to have the accuracy, objectivity in assessments, and independence in their interpretation