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Hamburg 2001 – scientific programme

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TT: Tiefe Temperaturen

TT 28: HF Anwendungen

TT 28.5: Talk

Friday, March 30, 2001, 11:45–12:00, J

Power dependencies of the surface impedance of YBCO — •Ermile Gaganidze1, Michael Fitsilis2, Roland Heidinger1, and Juergen Halbritter11Forschungszentrum Karlsruhe, IMF 1, Postfach 3640, D-76021 Karlsruhe, Germany — 2Institut fuer Elektrotechnische Grundlagen der Informatik, University of Karlsruhe, Hertzstrasse 16, D-76187 Karlsruhe, Germany

The application of HTS is obstructed by the nonlinear behavior of Z(T,f,Hrf) with rf field. The study of those nonlinearities profits by carefully calibrated rf measurements in the frequency and time domain, which yield δ Rs(Hrf) ∝ Hn ∝ δ Xs (Hrf). In contrast to δ Rs(Hrf) ∝ Hn, the ratio rXs/ δ Rs is independent of geometry factors and shows distinct T and f dependencies for various mechanisms and rf set-ups.

The high power rf response in the frequency domain yields nonlinear resonance curves, n and r values. The time domain measurements give useful insight about dynamics of the underlying nonlinear mechanisms. The results r ≃ 1 and n ≃ 1−2 are in line with Josephson fluxons in weak links, which may interact with dc fluxons threading through the weak links.

The weak links are quantified by R(T>Tc)-measurements with the help of percolation analysis yielding Rres (T< 0.8 Tc,f) in agreement with observations.

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