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Superconducting Nb-film LC resonator

A. Finne, L. Groenberg, R. Blaauwgeers, V. B. Eltsov, G. Eska, M. Krusius, J. J. Ruohio, R. Schanen, I. Suni

physics.ins-detarXiv:physics/0012052

Abstract

Sputtered Nb thin-film LC resonators for low frequencies at 0.5 MHz have been fabricated and tested in the temperature range 0.05--1 K in magnetic fields up to 30 mT. Their Q value increases towards decreasing temperature as sqrt(T) and reaches 103 at 0.05 K. As a function of magnetic field Q is unstable and displays variations up to 50%, which are reproducible from one field sweep to the next. These instabilities are attributed to dielectric losses in the plasma deposited SiO2 insulation layer, since the thin-film coil alone reaches a Q > 105 at 0.05 K.

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