In-situ measurement of the permittivity of helium using microwave NbN resonators

Abstract

By measuring the electrical transport properties of superconducting NbN quarter-wave resonators in direct contact with a helium bath, we have demonstrated a high-speed and spatially sensitive sensor for the permittivity of helium. In our implementation a $\sim 10^{-3}$ mm${}^3$ sensing volume is measured with a bandwidth of 300 kHz in the temperature range 1.8 to 8.8 K. The minimum detectable change of the permittivity of helium is calculated to be $\sim 6\times$$10^{-11}$ ${\epsilon }_0$/Hz${}^{1/2}$ with a sensitivity of order $10^{-13}$ ${\epsilon }_0$/Hz${}^{1/2}$ easily achievable. Potential applications include operation as a fast, localized helium thermometer and as a transducer in superfluid hydrodynamic experiments.

arXiv comment4 pages, 3 figures

References in corpus (8)

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• First observation of the thermal Sunyaev-Zel'dovich effect with kinetic inductance detectors
• Superconducting granular aluminum resonators resilient to magnetic fields up to 1 Tesla
• Thin film dielectric microstrip kinetic inductance detectors
• Catastrophic magnetic flux avalanches in NbTiN superconducting resonators