Berlin 2024 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 35: Superconducting Electronics: SQUIDs, Circuit QED
TT 35.5: Talk
Wednesday, March 20, 2024, 10:30–10:45, H 2053
Design considerations for the optimization of λ-SQUIDs — •Constantin Schuster1 and Sebastian Kempf1,2 — 1Institute of Micro- and Nanoelectronic Systems, Karlsruhe Institute of Technology, Germany — 2Institute for Data Processing and Electronics, Karlsruhe Institute of Technology, Germany
Cryogenic microcalorimeters such as metallic magnetic calorimeters (MMC) or superconducting transition-edge sensors (TES) have become a mature technology and are presently used in various applications requiring an excellent energy resolution. While development on these established technologies continues to progress, we have recently introduced an alternative microcalorimeter concept, called λ-SQUID. It is based on the strong temperature dependence of the magnetic penetration depth of a superconducting material, affecting the current distribution within a superconducting wire and hence its kinetic and geometric inductance. We use this effect to build a detector in which the mutual inductance between a SQUID and an input coil carrying a constant current becomes temperature sensitive. In this contribution, we present theoretical considerations regarding the design of the sensing element in a λ-SQUID to yield an optimal sensitivity and energy resolution. We show that the noise contribution form the λ-SQUID can be minimised if the specific heat of the sensing element exactly equals the particle absorber. Additionally, we consider the influence of sensing- and input coil stripline width, thickness, and separation on the detector sensitivity using a modified geometric mean distance method adapted to superconductors.
Keywords: SQUID; microcalorimeter; X-ray spectroscopy; tunable gain