28th International Conference on Low Temperature Physics (LT28), Gothenburg, 09-16, August, 2017, Sweden
Zusammenfassung
The primary magnetic field fluctuation thermometer (pMFFT) is a SQUID-based noise thermometer for temperatures below 1 K, which complies with metrological requirements. It combines two signal channels in order to apply the cross-correlation technique, but it requires statistically independent noise signals for proper operation. In order to check the limit of the cross-correlation readout, we have performed zero measurements in the millikelvin range in a setup that is identical to the pMFFT, except for the removed temperature sensor. We examined the influence of different parameters such as SQUID working point or flux-lock loop parameters on the minimum cross-correlation signal down to 24 mK and below 100 kHz. Depending on the configuration, typical minimum SQUID-referred cross-power spectral densities of 1.5 × 10−15Φ20 /Hz or even smaller values were observed. For the pMFFT, considering its thermal noise spectrum, these flux densities correspond to a device noise temperature of ≤ 2.5 µK, thereby ensuring a negligible uncertainty contribution at the lower end of the PLTS-2000 (0.9 mK).
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Open Access Gold
Rechteinformation
CC BY 3.0 ; Creative Commons Attribution 3.0 License
Themenbereich der Metrologie
Thermometrie
Zitierung
Kirste, A. & Engert, J. (2018). Cross-correlation limit of a SQUID-based noise thermometer of the pMFFT type. Journal of Physics: Conference Series, 969(1), 1–6. http://doi.org/10.1088/1742-6596/969/1/012083
