Design of Practical Superconducting DC Power Cable With REBCO Coated Conductors

critical current density of a superconductor in a parallel magnetic field. It was expected that a cable with a high current-carrying capacity could be realized with REBa2Cu3O7-σ (REBCO) coated conductors. However, the critical current density in most commercial coated conductors does not increase but slightly decreases with increasing parallel magnetic field. Nevertheless, the critical current density in the parallel magnetic field is remarkably higher than that in a normal in-plane magnetic field, and it is possible to construct a dc cable with a higher current-carrying capacity using this characteristic in comparison with conventional superconducting cables. In this paper, we propose a new design of dc power cable suitable for present commercial coated conductors. The optimal condition of the cable is discussed

Fabrication of 1 T Bi-2223 Superconducting Magnet with 92 mm Bore Diameter at 77 K

A Bi-2223 superconducting magnet for practical use in liquid nitrogen is designed and fabricated. Bi-2223 tapesprepared by ConTrolled Over Pressure (CT-OP) process are used for the winding, and the critical current at 77.3 K and self-field is in the range of 174–185 A. 28 double-pancake coils are resistively connected in series by copper terminals. Highcritical current tape is used for top and bottom double-pancake coils, since the magnetic field normal to the tape surface ishighest at the top and bottom of the magnet. Two iron plates at top and bottom of the magnet are used for reduction of thenormal component of magnetic field to the Bi-2223 tape, since the total performance of the magnet is determined by theminimum critical current at maximum normal magnetic field component to the tape. The inner bore diameter of the magnetis 92 mm. And the homogeneity of magnetic field of long-axis direction in 50 mmφ × 100 mm length is within 3%. Themaximum magnetic field at the center of the bore is over 1.0 T at 77.3 K.Proceedings of the Cryogenic Engineering Conference (2013) , June 17–21, 2013, Anchorage, Alaska, US

Round Robin Test of Residual Resistance Ratio of Nb3Sn Composite Superconductors

In this paper, a round robin test of residual resistance ratio (RRR) is performed for Nb3Sn composite superconductors prepared by an internal tin method by six institutes with the international standard test method described in IEC 61788-4. It was found that uncertainty mainly resulted from determination of the cryogenic resistance from the intersection of two straight lines drawn to fit the voltage versus temperature curve around the resistive transition. The measurement clarified that RRR can be measured with expanded uncertainty not larger than 5% with the coverage factor 2 by using this test method

Evaluation of Critical Current Density of FeAs-based Superconductors

In this review paper, we report the characteristics of the critical current density in FeAs based superconductors which is newly discovered by Hosono group of Tokyo Institute of Technology on 2008. Since the many specimens in present stage are not single crystals, there are two kinds of critical current density observed in the specimens which are so-called local and global critical current densities. Therefore, it is necessary to evaluate both kinds of critical current densities. The history effect in which the global critical current density shows different values in increasing and decreasing magnetic field is also observed when the specimens have the local and the global critical current densities. The wire which critical current is 180 A is successfully developed with using the knowledge of abovementioned characteristics of two kinds of critical current densities and the history effect

Flux pinning properties of (Nd, Eu, Gd)Ba2Cu3Oy (NEG-123) superconductors with 211 phase particles

Flux pinning properties were investigated by focusing on the origin of the high peak critical current density and the high irreversibility field for Nd0.33Eu0.38Gd0.28Ba2Cu3Oy (NEG-123) bulk superconductors with the addition of 211 secondary phase particles of volume fractions up to 10 mol%. It was found that a negative correlation exists between the peak critical current density Jcp and the irreversibility field Bi for various fractions of added 211 phase. This suggests that the mechanisms that determine Jcp and Bi are different. The 211 particles do not contribute to the peak effect neither directly through the pinning mechanisms of the condensation energy interaction nor indirectly with the aid of the order–disorder transition of flux lines. Other possible defects are nano-lamella structures. Although these defects do not directly contribute to the peak effect through the pinning mechanism of the condensation energy interaction, they may contribute to it with the aid of the order–disorder transition of flux lines. On the other hand, as Bi deteriorates with the addition of 211 particles, it is not determined by the flux pinning of 211 particles. The decrease in Bi is considered to be caused by the proximity effect of nano-lamella structures

Pinning property of Bi-2212 single crystals with columnar defects

The critical current density and the irreversibility field were measured before and after nickel ion irradiation for Bi-2212 single crystals in an optimally doped or an overdoped state in a magnetic field parallel to the direction of irradiation. The critical current density was theoretically calculated by using the summation theory and the flux creep-flow model. From the comparison with experimental results the condensation energy density was estimated for each specimen. These results are compared with a similar analysis on three-dimensional Y-123

Influence of anisotropy and pinning centers on critical current properties in Bi-2212 superconductors

The critical current density in Bi-2212 superconductors with various anisotropies irradiated by heavy ions was investigated in the medium temperature region to understand the effects of defect size and the anisotropy of the superconductor. It was found that the critical current density and the irreversibility field were larger for the specimen with larger defect and/or with smaller anisotropy. Introduction of stronger pinning centers and the optimization of the doping condition to improve the dimensionality are desired for further improvement of the critical current propertie