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arXiv · 1710.04326

Microwave SQUID Multiplexer demonstration for Cosmic Microwave Background Imagers

B. Dober·D. T. Becker·D. A. Bennett·S. A. Bryan·S. M. Duff·J. D. Gard·J. P. Hays-Wehle·G. C. Hilton·J. Hubmayr·J. A. B. Mates·C. D. Reintsema·L. R. Vale·J. N. Ullom
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Abstract

Key performance characteristics are demonstrated for the microwave SQUID multiplexer ($μ$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 $μ$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 $μ$MUX as a viable readout technique for future CMB imaging instruments.

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B. Dober, D. T. Becker, D. A. Bennett, S. A. Bryan, S. M. Duff, J. D. Gard, J. P. Hays-Wehle, G. C. Hilton, J. Hubmayr, J. A. B. Mates, C. D. Reintsema, L. R. Vale, J. N. Ullom. 2017-12-16. Microwave SQUID Multiplexer demonstration for Cosmic Microwave Background Imagers. https://doi.org/10.1063/1.5008527

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