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A study is conducted to measure the critical current densities of several types of Bi-2212 round wires by the transport current methods at various temperatures. The conclusion states that the equivalent filament diameters are several times larger as compared with the actual filament size.

Nb3Al superconductors present promising performance compared to Nb3Sn conductors when processes by rapid heating/quenching process. An R&D program of Nb3Al conductors for future accelerator magnets. Several test wires of around 0.8 mm diameter, which have relatively small filament and low matrix ratio, are fabricated.

Nb3Al filaments are formed directly through rapid heating and quenching (RHQ) treatment in a Nb/Al-Cu precursor wire and show excellent superconducting properties. The wires with 1.32at percent Cu addition show intermediate J(sub c) vs. B curves between those of the 2.5at percent Cu added and non-Cu added wires.

Nb3(Al, Ge) conductors are prepared with a diffusion reaction process at a temperature around 1400 degree Celsius, from multifimamentary Nb/Al-25 at percent Ge precursors. The findings indicate that small matrix ratio of 0.8 and piece-length of 30 m is achieved in the precursor preparation without intermediate annealing.

Reporting a new fabrication approach to fabricate Nb/Al-Ge multifilamentary wire with fine Al-Ge microstructure cores, using a reel-to-reel intermediate rapid quenching (IRQ) technique is discussed. It is concluded that a reel-to-reel intermediate rapid quenching process dramatically converts the Al-Ge core structure into a very fine microstructure.

Heat-treatment conditions and procedures having to do with transformation-heat based up-quenching (TRUQ) processes of Nb[subscript 3]Al coils are investigated, and results are summarized.

Stability and protection of externally stabilized and internally stabilized rapid-heating, quenching and transformation (RHQT) Nb[subscript 3]Al superconductors are examined experimentally.

(Nb,Ta)3Sn superconductors produced by Nb/Ta-Sn composite methods, were studied to determine pinning characteristics.

Rapid-quenched and transformed Nb3A1 multifalamentary superconductors were observed following the incorporation of stabilizer to decrease NB-barrier thickness and increase volume fraction.

Rapid quenched and transformed Nb3A1 multifilamentary conductors were investigated to determine field and temperature dependence of critical current density.

A study factored the impact of magnetic field orientation into an analytical simple formula for penetration loss in superconducting tapes, such as BSCCO, that was developed in previous research. The penetration loss in a silver-sheathed Bi-2223 tape was measured in the range of 0 - 120 mT. The derived formula explained well the measured penetration loss with the Ag-sheathed Bi-2223 tape in the magnetic field parallel or perpendicular to the tape face, sufficiently above the penetration field.

For more than 30 years, Pb–Bi alloy and Wood's metal (50% Bi, 26.7% Pb, 13.3% Sn, and 10% Cd) have been used as representative superconducting solder intermedia to establish superconducting joints between NbTi and Nb3Sn wires in high-field nuclear magnetic resonance magnet systems. However, the use of Pb and Cd has been severely restricted by environmental regulations, such as the Restriction of Hazardous Substances Directive. Herein, a novel method of forming a superconducting joint between NbTi and Nb3Sn wires without Pb and Cd has been proposed. This approach is based on metallurgical bonding processes using a superconducting Nb-alloy intermedium, whose fine microstructure is maintained even after exposure to temperatures higher than 650 °C. Further, fine crystal defects become sources of magnetic flux pinning centers. Among transition elements close to Nb, Hf is considered the most suitable additive for realizing high-temperature-tolerable (HTT) superconducting Nb-alloy intermedia. Utilizing the HTT characteristic of Nb–Hf, a superconducting joint between Nb3Sn filaments and one end of the Nb–Hf alloy core was created by forming a superconducting Nb3Sn layer at the interface through a chemical reaction. The other end of the Nb–Hf alloy core was cold-pressed with NbTi filaments, to connect their active new surfaces to each other in order to create a superconducting joint. Ultimately, a superconducting joint between NbTi and Nb3Sn wires was realized with a high critical magnetic field (Bc2) of more than 1 T. The formation of the superconducting joint was confirmed by current decay measurements. This method of forming a superconducting joint is promising for application in environmentally friendly nuclear magnetic resonance magnet systems. [ABSTRACT FROM AUTHOR]

A numerical code is proposed for the finite element analysis of alternating current losses in high temperature superconductors. An n-value was used to represent the electromagnetic characteristics of the superconductors. The Ohm's law is employed as the constitutive equation and equivalent conductivity is taken as the function of electric field. The influence of n-value was studied through the numerically analysis of alternating current loss.

Experimental and theoretical studies were conducted on the ramp rate instability in Cu/NbTi multifilamentary superconductors caused by external longitudinal magnetic fields. The quench current of anticlockwise-twisted superconductors was found to be adversely affected in the positive longitudinal magnetic field parallel to the transport current during increasing ramp rate. Resulting stability limits were in agreement with experimental quench currents within an error rate of 17%.

Microstructural control of Nb3Sn wire is quite important for improving the critical current density (Jc). Elemental doping is an effective method to improve the microstructure. In previous work, we have shown that Zn doping of Nb3Sn wire suppresses Kirkendall voids formation, and promotes the Nb3Sn layer formation. As an effective method to dope with Zn, we have previously proposed a Nb/Cu-Ti/Sn-Zn diffusion-pair structural internal tin Nb3Sn wire. In this study, we investigated the effect of Zn doping on the microstructure and the superconducting characteristics of this system, using a single Nb/Cu-Ti/Sn-Zn structural diffusion couple. The Sn composition in the Nb3Sn layer of the Zn doped specimen is slightly slower than that of the non-Zn doped one. The microstructural analysis was carried out by Electron Back Scattered Diffraction (EBSD), Energy Dispersive X-ray Spectroscopy (EDX) and digital image analysis. The average grain size was decreased with Zn doping, leading to an improvement in layer Jc in a low magnetic field. The thickness of the Nb3Sn layer in the Zn doped specimen is also thinner than that in the non-Zn doped one. In the diffusion-pair structure used in this work, increasing of the Zn content in the Sn-Zn core sacrifices the Sn content in the core. A decrease of the Sn content would account for the smaller Nb3Sn thickness in the Zn-doped specimen. [ABSTRACT FROM AUTHOR]