Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 31: Superconducting Electronics and Cryogenics: Poster Session

TT 31.12: Poster

Donnerstag, 8. September 2022, 15:00–18:00, P1

Noise Thermometers for Milli-Kelvin Measurements in High Magnetic Fields and for Micro-Kelvin Temperatures — •Pascal Willer, Christian Ständer, Nathalie Probst, Sarah Philips, Andreas Reiser, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University.

To measure the temperature in the presence of high magnetic fields is one of the big challenges in solid state physics labs. We recently started to construct a prototype of a cross-correlated, current sensing noise thermometer for mK-temperatures for application in high magnetic fields. The basic concept relies on the thermal movement of charge carriers in a resistor. DC-SQUIDs detect the corresponding noise signal which is then recorded via two identical but independent amplifier chains. The method of cross correlation is used to eliminate uncorrelated noise contributions from the amplifier chains. As resistor material we use an alloy of platinum and thungsten, Pt₉₂W₈, since this material is characterized by an extremely small temperature dependence of the electrical resistivity as well as the smallest magneto-resistance known to date. We show that this approach towards a relative primary thermometer for high magnetic fields is able to operate over a wide range of temperatures within less than 1% uncertainty.
Additionally, we developed a second noise thermometer based on an alloy of copper and silver called “CuSil” to measure down to µK-temperatures in the absence of magnetic fields.
We discuss the design and the necessary considerations of both thermometers and present first experimental results at mK temperatures.