Microwave SQUID Multiplexer demonstration for Cosmic Microwave Background Imagers

• Published in: arXiv.org
• Main Authors: Dober, B, Becker, D T, Bennett, D A, Bryan, S A, Duff, S M, Gard, J D, Hays-Wehle, J P, Hilton, G C, Hubmayr, J, Mates, J A B, Reintsema, C D, Vale, L R, Ullom, J N
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 16.12.2017
• Subjects: Big Bang theory; Bolometers; Cosmic microwave background; Crosstalk; Mapping; Microwave probes; Multiplexing; Noise; Noise levels; Noise prediction; Physics - Instrumentation and Methods for Astrophysics; Power spectral density; Superconducting quantum interference devices; Variations
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1710.04326

Key performance characteristics are demonstrated for the microwave SQUID multiplexer (\(\mu\)MUX) coupled to transition edge sensor (TES) bolometers that have been optimized for cosmic microwave background (CMB) observations. In a 64-channel demonstration, we show that the \(\mu\)MUX produces a white, input referred current noise level of 29~pA\(/\sqrt{\mathrm{Hz}}\) at -77~dB microwave probe tone power, which is well below expected fundamental detector and photon noise sources for a ground-based CMB-optimized bolometer. Operated with negligible photon loading, we measure 98~pA\(/\sqrt{\mathrm{Hz}}\) in the TES-coupled channels biased at 65% of the sensor normal resistance. This noise level is consistent with that predicted from bolometer thermal fluctuation (i.e., phonon) noise. Furthermore, the power spectral density exhibits a white spectrum at low frequencies (\(\sim\)~100~mHz), which enables CMB mapping on large angular scales that constrain the physics of inflation. Additionally, we report cross-talk measurements that indicate a level below 0.3%, which is less than the level of cross-talk from multiplexed readout systems in deployed CMB imagers. These measurements demonstrate the \(\mu\)MUX as a viable readout technique for future CMB imaging instruments.