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TT: Fachverband Tiefe Temperaturen

TT 29: Poster Session: Cryogenic Particle Detectors and Cyotechnique

TT 29.10: Poster

Montag, 12. März 2018, 15:00–19:00, Poster B

Cross Correlated Noise Thermometer for Milli-Kelvin Temperatures — •Christian Ständer, Andreas Reifenberger, Felix Mücke, Marius Hempel, Daniel Richter, Sebastian Kempf, Andreas Fleischmann, Andreas Reiser, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University.

Within our search for easy-to-use reliable thermometers for milli-Kelvin and micro-Kelvin temperatures we developed a noise thermometer, where the Johnson noise of a massive cylinder of high purity (5N) silver is monitored simultaneously by two current sensing dc-SQUIDs. Operating both SQUIDS in voltage biased mode in 2-stage SQUID configurations allows to reduce the power dissipation as well as the noise of the SQUIDS to a minimum. By cross-correlating the two SQUID signals the noise contribution of the read-out-electronics is suppressed to a marginal level even at micro-Kelvin temperatures. To further reduce the correlated amplifier noise we fabricated SQUIDs with a new design featuring minimal coupling of input and feedback coil. We compare two thermometers of this type to a previously developed noise thermometer in the temperature range from 3K down to 4mK. Statistical uncertainties below 0.5% are achieved within 10s of measurement time. Within this uncertainty no self-heating was observable at base temperature.