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VAMAS TWA 16 promoted an international round robin test (RRT) on critical current (Ic ) measurement of RE-Ba-Cu-O (REBCO; RE=rare earth) superconductors to establish the transport Ic measurement method in liquid nitrogen bath without an external magnetic field. Ten laboratories from five countries participated in the RRT and tested commercially available REBCO superconductors. Ic and measurement conditions were reported. In parallel, intrinsic Ic nonuniformity of the superconductors were evaluated by reel-to-reel scanning Hall-probe microscopy for 10-m conductors. Statistical analyses of Ic provided uncertainty of the measurement method. Combined standard uncertainty was analyzed considering the intrinsic nonuniformity of Ic . The analysis indicated that the intrinsic nonuniformity has the largest contribution to the uncertainty of Ic. [ABSTRACT FROM AUTHOR]

Fujikura Ltd., Chiba, Japan, has developed stable and high-throughput production techniques for REBCO coated conductors (CC) by using large-area ion-beam-assisted-deposition (IBAD), and hot-wall type pulsed-laser-deposition (PLD). Recently, we have been attempting to dope BaMO3 (BMO, M: Zr or Hf) to REBCO layer in order to enhance in-field critical current density (Jc ). In the course of optimizing deposition conditions of PLD for BaHfO3 doped EuBCO films on IBAD templates, "high Jc condition" and "high growth rate condition" were found. For samples prepared under these conditions, the magnetic field angle dependence of Ic and REBCO thickness dependence were investigated. Finally, we succeeded in fabricating a 300-m-long CC with uniform Ic distribution at the high-growth-rate condition. The longitudinal Ic homogeneity (defined as standard deviation divided by average) at 77 K evaluated by magnetization method was 2.6%, which is comparable to nondoped conductors. Transport in-field Ic for the both end points were 1756 and 1786 A/cm at 30 K, 2 T, respectively. [ABSTRACT FROM AUTHOR]

We investigated the relationship between current capacity and local critical current distribution of a Cu-sheathed multifilamentary RE-123 coated conductor (CC). Patterning multifilamentary structure on CC will be a promising solution for reducing magnetization to assure spatial homogeneity and its temporal stability of magnet applications such as MRI and NMR. On the other hand, it will become more difficult to maintain the current capacity because a smaller defect can block the current flow in a narrower filament. Permitting electrical coupling among the filaments will work for maintaining current capacity because current can avoid such a defect by flowing into the adjacent filament. However, too small interfilamentary resistance will result in long time constant of filament coupling, which will affect spatial homogeneity and its temporal stability of magnet applications. Therefore, to design a multifilamentary CC satisfying the requirement from magnet applications, it is necessary to understand the quantitative impact of interfilamentary resistance of the multifilamentary CC on its current capacity under the influence of spatial variation of local critical currents. In this study, we estimated global critical current of a Cu-sheathed multifilamentary CC as a function of interfilamentary resistance by considering its local critical current distribution in each filament. As a result, it was confirmed that the electrical coupling among the filaments was very effective to improve the current capacity of such a multifilamentary CC especially for a section with spatially inhomogeneous local critical currents. Furthermore, it was also found that local heat generation could be significantly suppressed even for a section with relatively homogeneous local critical currents. [ABSTRACT FROM AUTHOR]

We have investigated the in-field critical current properties in BaZrO3-added (Y, Gd) Ba2Cu3O7-δ (YGdBCO)-coated conductor fabricated by using a multi-coating trifluoroacetates metal-organic deposition (MOD) method. We compared these properties with EuBCO-coated conductor fabricated by the pulsed laser deposition (PLD) method. The sample using the 30-nm oncecoat-layer-thickness donce shows superior in-field Jc down to 4.2 K than that of the previous standard coating using 170-nm-thick layer for each coating. From the analysis of E-J characteristics, an analytical expression for Jc as a function T and B has been derived. It was confirmed that the high Jc region in sample with donce = 30 nm is widely spread in high-temperature and high-magneticfield region. By comparison with the Jc properties of the BaHfO3 - added PLD CCs, the minimum Jc, which is estimated from magnetic field angle dependence, shows even higher value up to 5 T of magnetic field at 65 K and up to 3 T at 77 K. From these results, the new MOD-YGdBCO process using the thin once-coat-layerthickness is very promising for the practically important mid field region such as 3 to 5 T. [ABSTRACT FROM AUTHOR]