Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 17: Cryogenic Detectors and Cryotechnique
TT 17.4: Talk
Wednesday, September 7, 2022, 10:15–10:30, H22
Flux ramp modulation based hybrid microwave SQUID multiplexer — •Constantin Schuster1,2, Mathias Wegner1,2, Christian Enss1, and Sebastian Kempf1,2 — 1Kirchhoff-Institute for Physics, Heidelberg University, Heidelberg — 2Institute of Micro- and Nanoelectronic Systems, Karlsruhe Institute of Technology, Karlsruhe
For the readout of cryogenic detector arrays, microwave SQUID multiplexers (µMUXes) are presently being developed. Using non-hysteretic rf-SQUIDs, each multiplexer channel transforms the detector signal into a change of amplitude or phase of a microwave signal probing the resonance frequency of a superconducting resonator. In this way, numerous detectors can be simultaneously read out by coupling multiple resonators to a common transmission line. The resonator bandwidth is adjusted according to the detector speed and sets a lower limit for the frequency spacing of resonators. This limit, however, can in practice only be reached if the fabrication accuracy is very high. As a result, the channel density is very often limited by fabrication rather than the inherent channel capacity of the transmission line. We present a hybrid microwave SQUID multiplexer combining two frequency-division readout techniques to allow multiplexing a given number of detectors with only a fraction of readout resonators. We present insights of our approach based on information theory and discuss benefits and drawbacks using Monte-Carlo simulations. We further discuss the performance of a prototype device indicating that our technique is very well suited for reading out ultra-large bolometric detector arrays.