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In Korea, the superconducting power cable has been developed since 2001, with the basic specifications of 22.9 kV/50 MVA. The superconducting power cable can carry more than 2 to 5 times higher electric power compared with conventional ones. It is important to test the DC critical current related with its power capacity before applying to the real power grid. In 1995, several international standards organizations including IEC, decided to unify the use of statistical terms related with "accuracy" or "precision" in their standards. It was decided to use the word "uncertainty" for all quantitative (associated with a number) statistical expressions. In this paper, we measured DC critical current of 22.9 kV/50 MVA superconducting power cable with several voltage tap and analyzed the uncertainty with these results. These analyzed results can be applied the standardization of the superconducting power cable [ABSTRACT FROM AUTHOR]

Proton irradiations on superconducting bulk materials and thin films have enabled to enhance the critical current density and the upper critical field in the mixed state due to increased vortex pinning. We investigated the microwave surface resistance (Rs) of proton-irradiated YBa2Cu3O7-δ (YBCO) films grown on LaA1O3 (LAO) substrates. The intrinsic Rs was measured at ∼8.5 GHz at temperatures of 7–90 K with the effects of the finite film thickness taken into account. Significant reduction in the Rs of YBCO films were observed at temperatures of 40 K to 70 K when the films were irradiated with 20 MeV proton for 10 minutes to the fluence of 0.47 × 1015 ions/cm2 with the value of 100 μ∖ of the proton-irradiated one at 60 K appearing significantly lower than the corresponding one of 100 μ∖ before irradiation. However, at temperatures below 20 K, the R5 of the irradiated YBCO films was higher than that of the YBCO film before irradiation with the residual Rs of the former appearing higher than that of the latter. No significant changes in the Rs of YBCO films were observed when the films were irradiated with 20 MeV proton for 30–120 minutes to the fluences of 1.4 × 1015 to 5.7 × 1015ions/cm2. The reduction in the R5 of proton-irradiated YBCO films at 40–70 K was attributed to enhanced impurity scattering rate of ∼ 2 × 1012/s compared to a value of ∼ 7.6 × 1011/s for unirradiated YBCO. [ABSTRACT FROM AUTHOR]

We propose a modified two-tone method that could be used for sensitive measurements of the intrinsic microwave surface impedance (Zs) of thin superconductor films and the tanδ of a low-loss dielectric. An open-gap resonator scheme is used to measure the penetration depth (l) of thin superconductor films and extract the intrinsic Zs of the superconductor films from its measured Reseff and l. We use a very small gap of 10 μm between the top plate and the rest parts of the resonator. The tanδ of rutile in the low 10-7 range and the dielectric constant as high as ∼ 110 are observed at temperatures below 10 K at ∼ 15.2 GHz, which enable to measure the Rs of the 10 mm-in-diameter YBCO films as low as ∼ 100 μΩ at the same frequency (f). The discrepancy between the Rseff at ∼ 15.2 GHz and that at ∼ 8.5 GHz scaled to ∼ 15.2 GHz appears less than 2% when the relations of Rs ∝ f² and tanδ ∝ f are used. We describe usefulness of our measurement method for measuring the intrinsic microwave properties of various superconductor samples. [ABSTRACT FROM AUTHOR]

We have measured the temperature dependence of the microwave surface impedance and the nonlinear response of high-quality MgB[sub 2] films on c-cut sapphire at temperatures below 40 K. MgB[sub 2] films with surface resistance (R[sub s]) as low as 0.02 mΩ at 8 K and 8.5 GHz were prepared in an ex-situ process by annealing a boron layer in magnesium-rich environment. The nonlinear properties of the MgB[sub 2] films were investigated as a function of temperature by means of higher-order harmonic-generation measurements in patterned coplanar waveguide devices. We find that the nonlinear responses of devices fabricated from MgB[sub 2] films were substantially higher than the nonlinear responses of similar devices fabricated from YBa[sub 2]Cu[sub 3]O[sub 7-δ] thin films at the same reduced temperature. We also compared the nonlinear responses of surface ion-milled MgB[sub 2] films with as-grown films and found that the ion-milled films gave lower nonlinear responses at temperatures below 24 K. The consequences of these measurements for passive microwave device applications of MgB[sub 2] films are also discussed. [ABSTRACT FROM AUTHOR]

The new superconductor MgB[sub 2] may prove useful for microwave applications at intermediate temperatures. MgB[sub 2] films with the thickness of 300-400 nm have surface resistance R[sub s] less than 10 µΩ at a frequency (ω/2π) of 8.5 GHz and 7 K, and ∼ 1.5 mΩ at 87 GHz and 4.2 K. The critical temperature (T[sub C]) of these films is ∼ 39 K when they are prepared under optimum conditions. The R[sub s] appears to scale as ω² up to 30 K. After surface ion-milling, a reduction of the T[sub C] and an enhanced resistivity p(T[sub C]) are observed consistently at 8.5 GHz and 87 GHz along with a reduced R[sub s] at low temperatures. The observed ρ(T[sub C]) - T[sub C] relation and the uncorrelated behavior between ρ(T[sub C]) and R[sub s] values measured at low temperatures are well explained in terms of the two-gap model, with the observed ρ(T[sub C]) - T[sub C] relation attributed to the properties of the large gap, and the R[sub s] at lower temperatures reflecting the properties of the small gap, with an enhanced gap energy due to increased interband scattering. This study suggests that the interband scattering should be enhanced to improve the low temperature microwave properties of MgB[sub 2] films and that the ion-milling process must be performed with great care to preserve the high quality of MgB[sub 2] films. [ABSTRACT FROM AUTHOR]

Precise measurements of the surface resistance of high temperature superconducting (HTS) thin films using transmission mode dielectric resonators requires accurate knowledge of the unloaded Q factor (Q[sub o]). So far, the most accurate method of Q[sub o] determination for transmission mode resonators is the Transmission Mode Q Factor (TMQF) technique based on the processing of S-parameters (S[sub 21], S[sub 11], S[sub 22]). The technique accounts for parasitic effects including noise, crosstalk, coupling reactance and coupling losses but does not yet take into account the impedance mismatch between the test ports of the vector network analyzer and the inputs to the resonator. Discrepancies between measured and ideal S-parameters due to the mismatch lead to inaccuracies in coupling coefficient computations. This causes undesirable error in the calculated Q[sub o]. We present measurements of Q[sup o] obtained using the TMQF technique for mismatched and matched connections between the test ports of the vector network analyzer and the inputs to the dielectric resonator. These results are compared with values obtained using the traditional Insertion Loss method. [ABSTRACT FROM AUTHOR]

We have studied the microwave surface impedance of large YBCO films on as-prepared MgO substrates and on annealed MgO substrates with 50 mm in diameter. YBCO films were prepared by pulsed laser deposition. The surface resistance (R[sub S]), homogeneity in the R[sub S], and structural properties of YBCO on annealed MgO appeared improved compared with those of YBCO on as-prepared MgO. The reduced R[sub S] of YBCO films on annealed MgO is attributed to improved in-plane orientation of the YBCO grains in the films with local variations in the in-plane orientation of YBCO grains correlated well with the R[sub S] for both YBCO films on as-prepared MgO and those on annealed MgO. [ABSTRACT FROM AUTHOR]

Studies the microwave and structural properties of YBa[sub 2]Cu[sub 3]O[sub 7-gamma] superconducting films on R-cut sapphire buffered with post-annealed CeO[sub 2] layer. Surface morphology and structures of CeO[sub 2] layers and YBCO films; X-ray diffraction patterns of YBCO films.

Focuses on axially symmetric TE01delta mode of a parallel plate dielectric resonator to investigate the effects of the finite high temperature superconducting films on resonant frequency. Description of dielectric-loaded cavity resonators; Comparison of the experimental and calculated values of resonant frequency.

An analysis of the axially symmetric TM/sub 011/ mode in a dielectric-loaded cavity is presented and a technique of using a TM/sub 011/ mode dielectric-loaded cavity is introduced for measurements of microwave surface resistances of HTS thin films. A dielectric resonator with /spl epsiv//sub r//spl ap/39 is used for this purpose. It turned out that Q of the TM/sub 011/ mode dielectric-loaded cavity is very sensitive to the surface resistance of the material at the bottom plate, especially to the surface resistance of the area under the dielectric resonator, which can be used to investigate local microwave properties of large HTS thin films in a nondestructive, simple way. Experiments on YBCO thin films with the dimensions of /spl sim/2/spl times/2 cm/sup 2/ are performed using this technique, which revealed inhomogeneity in the microwave surface resistance of the thin films at different sites and demonstrated the usefulness of this technique. [ABSTRACT FROM PUBLISHER]