As the 4th lecture of the series on high-temperature superconducting materials, this article provides an overview of REBa 2 Cu3Ox (RE: Y and rare earth) wires (so-called coated conductors) from the fabrication process to future prospects. Development of coated conductors has progressed rapidly in the last decade and the properties of coated conductors are approaching the market requirements for practical superconducting devices such as power cables, transformers, SMES and rotating machinery. Several venders have started to sell coated conductors. The fabrication processes of coated conductors and their properties are briefly reviewed so that non-specialists can understand coated conductors during their use in designing HTSC devices. The future prospects of coated conductors for practical applications are discussed as well.
This paper reports thermal diffusivities of Bi-system and Y-system tape conductors. First, we measure temperature traces of the bundled conductors for the heater disturbance at conduction cooling conditions. Obtained results are modeled and analyzed using one-dimensional as well as two-dimensional heat balance equations. We show that the analysis results can successfully reproduce the experimental results for a wide temperature range from 20 to 77 K. On the basis of such results, we also clarify that the thermal diffusivity, in the perpendicular direction to the tape surface, of the Y-system conductors are five orders of magnitude lower than that of the Bi-system ones. Our results indicate that the consideration of such low thermal diffusivity is important for the conduction-cooled magnet design.