[en] Composite billets that function as starting stock for superconducting wire are produced by immersing an assembly of rods of a superconductor alloy or rods of a metal which is capable of forming a superconductor into a molten bath of normal material, thereby encasing the assembly within normal material, allowing the molten bath to solidify and form a rough as-cast billet and thereafter zone-melting the billet so as to remove all vestiges of shrinkage cracks, surface imperfections and internal inhomogeneities. 9 claims, 3 figures

[en] Superconducting magnets made of high current composites, often show their maximum performances to be limited by the so called degradation. One fundamental reason arises from the fact that if transposition of the filaments in a composite allows complete sharing of the transport current, twisting does not. As a result, the filaments behave collectively and the overall self field can give rise to a catastrophic flux jump. The question is: are the usual multifilamentary composites stable. If not, what current can be carried without instability problems. Reciprocally what composite is to be chosen in typical magnets to carry a given current. Expressions and curves act as very useful basis for determination of quenching currents in coils under various cooling

[en] Short communication

[en] The invention concerns a superconductor consisting of a number of superconducting filaments which are embedded in normally conducting material like, e.g., copper. In order to suppress coupling effects between th filaments in alternating magnetic fields, the filaments are snaked on circles with different radii around the longitudinal axis of the superconductor, each filament forming a helix concentrical with the conductor axis. If, on the other hand, the alternating magnetic field has a longitudinal component, two coils of different diameter are screening one another, which will cause magnetic instabilities and considerable alternating field losses. In order to prevent this, the filaments according to the invention are alternatingly snaked in opposite sense of rotation, each of the helices formed by the filaments describing a predetermined number of complete turns around the conductor axis in a linear segment corresponding to the alternating length. (FW)

[en] Short communication

[en] This study, 85K phase superconductive thin films in a B₍2-x)Pb_xSr₂Ca₂Cu₃O₍10+y) bismuth-copper-oxide system are obtained by synchronized deposition of Bi, Cu, CaF2, SrFZ compounds on Mg0 (t00) single crystal substrates annealed in 600-B40 0 C temperature range. The films are annealed in H20+Oz atmosphere for the removal of F (flouride) from the structure. Resistance-temperature measurements of the samples are analyzed via the d.c. method in the range of 77 K - 300 K. X-ray powder diffraction studies revealed which phases occured in the structure. No single-phase B5 K superconductivity is observed. The films are observed to grow along the c-axis due to reflections on the (OOQ (/=2, 4, 6... ) planes. Although various annealing conditions applied, the critical temperatures of the prepared films were not attamed above the liquid nitrogen temperature in the case of single-source evaporation. The critical temperatures, however, are obtained at higher levels when Bi metals is used as bismuth source and evaporated in a different boat. In addition, an improvement in the metallic behavior is observed

[en] Short communication

No abstract available

[en] We summarize progress in the development and application of metamaterial structures utilizing superconducting elements. After a brief review of the salient features of superconductivity, the advantages of superconducting metamaterials over their normal metal counterparts are discussed. We then present the unique electromagnetic properties of superconductors and discuss their use in both proposed and demonstrated metamaterial structures. Finally we discuss novel applications enabled by superconducting metamaterials, and then mention a few possible directions for future research. (review article)

[en] Short communication