Berlin 2024 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 18: Superconductivity: Poster
TT 18.66: Poster
Monday, March 18, 2024, 15:00–18:00, Poster C
Novel Susceptibility Thermometer for mK-Temperatures Based on Au:Er Micro-Fabricated on a Al2O3 Substrate — •Wassily Holzmann, Nathalie Probst, Andreas Fleischmann, Andreas Reifenberger, Andreas Reiser, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University
Limited options exist for thermometers at mK- and sub-mK- temperatures that combine speed, high sensitivity, and reliability. Here, we present a novel concept of a susceptibility thermometer based on the paramagnetic alloy Au:Er 2000 ppm that has the potential to meet these requirements. To ensure optimal thermal contact, the 9 µm thick Au:Er sensor sputter deposited on a copper sheet is pressed onto superconducting meander-shaped readout coils with 6 µm pitch, micro-fabricated on a Al2O3 wafer, using springs. Two such coils, filled with Au:Er, and two empty coils form a wheatstone-like bridge with the filled coils opposed. The inductance of the empty coils is chosen to balance the bridge at a specific temperature, where the thermometer can be operated as extremly sensitive zero-detector, fully independent of any overall gain drift. The coils have a combined length of 129 m, which results in an voltage signal that can be readout with room temperature electronics. For certain applications, this can serve as an individual fixed point for precise temperature stabilization. The imbalance due to the paramagnetic contribution of the Au:Er at all other temperatures is used to establish a temperature scale by calibration with another thermometer, in our case a noise thermometer. We will discuss the design, fabrication, readout, and operation.
Keywords: thermometry; susceptibility