Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 22: Superconductivity – Poster I

TT 22.20: Poster

Montag, 9. März 2026, 18:00–20:00, P1

Optimization of cross-type dc-SQUIDs for the readout of MMCs — Alexander Stoll, •Lukas Münch, Daniel Hengstler, Andreas Reifenberger, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University, Germany

Readout chains of ultra-low-temperature detector systems often limit the achievable energy resolution. Even superconducting quantum interference devices (SQUIDs), the state-of-the-art sensors for cryogenic detectors such as metallic magnetic calorimeters (MMCs), typically dominate the white-noise regime. The energy sensitivity of a dc-SQUID є ∼ T√LC is mainly set by the inductance, intrinsic Josephson junction capacitance, and temperature. While the inductance is fixed for practical reasons, the capacitance can be reduced by moving from a window-type to a cross-type junction geometry. Furthermore, the operation temperature of the SQUIDs which typically decouples from the much lower mixing chamber temperature due to heat dissipation in the shunt resistors, can be lowered. Following an idea from Stephen Boyd and coworkers (to be published), we divide the cooling fins into multiple sectors across the shunt resistor to improve electronic heat dissipation. We describe the fabrication of cross-type dc-SQUIDs for MMC readout, emphasizing the role of CMP-based processing in achieving high wafer-scale yield and uniformity on three-inch wafers. Finally, we present their characterization and compare the noise performance to earlier dc-SQUID generations.

Keywords: dc-SQUIDs; Nb/Al-AlOx/Nb trilayer; microfabrication; hot electron effect; white noise