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TT: Fachverband Tiefe Temperaturen

TT 11: Superconductivity: Poster

TT 11.43: Poster

Montag, 17. März 2025, 15:00–18:00, P4

dc-SQUIDs with distributed lossy lines to damp LC resonances — •Nicolas Kahne, Anna Ferring-Siebert, Daniel Hengstler, Fabian Krämer, David Mazibrada, Lukas Münch, Alexander Stoll, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University

SQUIDs are sensitive superconducting magnetic flux to voltage converters, whose operation is based on the Josephson effect. In particular at mK temperatures this sensitivity can be degraded by LC-resonances in inductances and capacitances of different structures of the SQUID design. To damp the resonances and reduce their influence on the SQUID characteristics, lumped-element resistors are commonly placed into the SQUID circuitry, which need precise simulations to determine the appropriate resistance values and positions.
In this contribution we show results for a dc-SQUID with a new damping strategy, using lossy lines for the input coil and the feed lines. For the input coil we use a thin gold layer which is fabricated in a bilayer process underneath the superconducting coil. For the parallel pair feed lines, on the other hand, we damp inductively through large areas of gold on top which are galvanically decoupled by an insulating layer. We compare the different damping schemes for single dc-SQUIDs and two-stage dc-SQUID setups, regarding the resonance features in their SQUID characteristics and noise contributions. For future designs we also plan tests with SQUID-washers made of lossy lines.