Intrinsic surface impedance of YBa2Cu3O7-delta- and SmBa2Cu3O7-delta-coated conductors measured non-invasively by using a dielectric resonator method

Abstract

Realization of a high critical current density (J(c)) on the order of 10(6) A/cm(2) at 77 K for long, thick, high-temperature superconductor (HTS)-coated conductors makes it possible to use the coated conductors for both small-scale and large-scale applications. YBa2Cu3O7-δ (YBCO)- and SmBa2Cu3O7-δ (SmBCO)-coated conductors with respective critical current densities (J(c)) of I X 10(6) A/cm(2) (77 K) and 1.2 X 10(6) A/cm(2) (77 K) were grown oil flexible, biaxially textured Ni tapes with a width of 10 mm and a thickness of ∼ 70 μ m. The intrinsic surface resistance and the penetration depth of the coated conductors were measured using a, rutile-loaded resonator and a sapphire-loaded resonator at the respective resonant frequencies of ∼ 8.5 GHz and ∼ 19.5 GHz at temperatures below 90 K. Intrinsic surface resistance (R-s) values of ∼ 440 μ&UOmega; and ∼ 360 μ&UOmega; were observed at 77 K and ∼ 8.5 GHz for YBCO- and SmBCO-coated conductors, respectively; these values are comparable to those for YBCO films on dielectric single-crystal substrates. The surface resistance of a 2.50 nm-thick SmBCO-coated conductor appeared to increase a little after it was wound around a 30-mm-diameter rod. Our results demonstrate the usefuluess of the dielectric resonator method for quality control of long HTS-coated conductors and the possibility of using the HTS-coated conductors for relatively small cavity resonators.