SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 58: Poster: Superconductivity II

TT 58.25: Poster

Donnerstag, 30. März 2023, 15:00–18:00, P2/OG3

Noise thermometers for mK- and µ K-temperatures in high magnetic fields — •Pascal Willer, Christian Ständer, Nathalie Probst, Andreas Reiser, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany.

To measure the temperature in the presence of high magnetic fields is one of the big challenges in solid state physics labs. We developed 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 motion of charge carriers in a bulk metal resistor. Two 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 materials we use the alloys Ag₆₀Cu₄₀ as well as Pt₉₂W₈, the latter being 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 cover the complete temperature range below 4 K. We discuss the design and the necessary considerations of both thermometers and present first experimental results at mK temperatures.