Manfred Wilhelm

Die polarisierende wirkung von zweiphasigem indiumantimonid im ultraroten

Zusammenfassung Indium-Antimonid mit Einschlussen einer zweiten, elektrisch gut leitenden Phase kann optisch anisotrop wirken, wenn die Einschlusse aus parallel ausgerichteten dunnen Nadeln bestehen. Etwa 70 μ dicke Schichten aus InSbNiSb und InSbFeSb sind zur Verwendung als Polarisationsfilter im Ultraroten geeignet. Mit InSbNiSb-Filtern wird ein Polarisationsvermogen uber 0,99 erreicht. Durch Vergutung steigt die Durchlassigkeit des senkrecht zur Nadelrichtung schwingenden Lichtes auf uber 40 Prozent. Das an InSbMnSb reflektierte Licht wird teilweise polarisiert.

Development of A15 Multifilamentary Superconductors

The superconducting properties of bronze processed Nb3Sn multifilamentary conductors are dependent on the structure and the diffusion treatment of the conductor. The tin concentration of the bronze, the volume ratio bronze to niobium, the filament diameter and the filament distribution are significant. The current carrying capacity can be increased considerably by the suitable addition of third elements. On the other hand conductor properties are sensitively influenced by diffusion temperature and diffusion time. High diffusion temperatures favor a high critical temperature Tc and a high critical flux density Bc2, low diffusion temperatures promote a better flux pinning by the increasing number of grain boundaries. As a consequence optimal diffusion conditions for high critical currents at high fields, and high critical currents at low fields, are different. Finally the influence of mechanical stress on the superconducting properties has to be regarded. Depending on the composition of the conductors different compressive stresses are acting on the Nb3Sn layers.1–10

Herstellung von V3Ga- und Nb3Sn- multifilamentleitern hoher stromtragfähigkeit mit hilfe chemischer transportreaktionen☆

Abstract Composite wires containing vanadium or niobium filaments in a copper or bronze matrix can be charged with gallium or tin by the aid of chemical transport reactions. The reactions take place in a closed reaction chamber heated isothermally. Chemical transport is initiated by traces of water or iodine or hydrogenchloride. In short samples of the conductors appropriately annealed overall current densities up to 2·10 5 A/cm 2 (4.2 K; 5 T) were attained. Under certain experimental conditions the direction of the transport can be reversed. Then the greater part of the tin is extracted from its copper solution.

Fabrication and Properties of Multifilamentary BiPbSrCaCuO-2223 Tapes

Silver sheathed 2223-BiPbSrCaCuO single filamentary and multifilamentary tapes were prepared by the conventional powder in tube method [1–3]. The fabrication of the tapes by swageing and rolling is followed by a repeated cold pressing with an intermediate heat treatment to form a highly textured 2223-phase. The samples were investigated by EDX, REM, X-ray diffraction and critical current measurements. At 77 K the best single filamentary tapes showed critical current densities jc > 30 kA/cm2. In multifilamentary tapes jc-values up to 12 kA/cm2 were measured. In particular in single filamentary tapes a strong scattering in current carrying capability was observed, although they were all fabricated in the same way. Therefore we investigated the mechanical working process and the 2223-phase formation as a function of various nominal compositions and annealing conditions.

Properties of (NbTa)3Sn-Filamentary Conductors

Conductors with 3721 filaments were fabricated by the bronze route in commercial lengths. Optimal superconducting properties have been obtained with filaments of Nb-7.5 w/o Ta. High overall critical current densities were measured; e.g. j(15 T, 4.2 K)=3.4·104 A/cm2. The extrapolated Bc2 -values were high (about 26 T). The strain dependence or the critical current was lower for conductors with (Nb,Ta)3Sn filaments.