Superconductor Technology Group
- Preparation and evaluation of large-area superconducting oxide thin films, and development of a fault-current limiting element -

For the purpose of industrial application of superconductors to electric power devices, microwave devices, etc., we investigate materials preparation and evaluation technologies, device technologies, as well as basic physics and theory.

In a superconductor a large current flows without electric resistance. However, a resistance sets in if the current becomes larger than a specific value, the critical current. If such a current continues to flow, the temperature of the superconductor increases due to Joule heating, and eventually it goes to the normal state and gives much higher resistance. Using such characteristics of a superconductor, we can produce a new electric power device, a fault-current limiter (FCL), which limits a fault current in the power grid in case of short circuit. Currently our group is mainly engaged in research on the fabrication and evaluation technology (Fig. 1) of large-area superconducting thin films that are used for FCL. We are also developing high power-density FCL elements (Fig. 2) in collaboration with other groups in AIST.

Fig. 1 ( left ) Distribution of the critical current density Jc (left figure in MA/cm2) and the n-values (indices of power-law I-V characteristics) in a YBa2Cu3O7 thin film (1 cm x 6 cm) used to prepare an FCL element. The measurement of n-values in addition to Jc facilitates the detection of degraded segments.

Fig. 2: AIST-original, superconducting thin-film FCL element with a Au-Ag alloy shunt layer, which can withstand high electric fields in case of short circut.

Superconductor Technology Group

AIST Tsukuba Central 2, Tsukuba, Ibaraki 305-8568 Japan
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