Highly-multiplexed microwave SQUID readout using the SLAC Microresonator Radio Frequency (SMuRF) electronics for future CMB and sub-millimeter surveys

Shawn W. Henderson, Zeeshan Ahmed, Jason Austermann, Daniel Becker, Douglas A. Bennett, David Brown, Saptarshi Chaudhuri, Hsiao Mei Sherry Cho, John M. D'Ewart, Bradley Dober, Shannon M. Duff, John E. Dusatko, Sofia Fatigoni, Josef C. Frisch, Jonathon D. Gard, Mark Halpern, Gene C. Hilton, Johannes Hubmayr, Kent D. Irwin, Ethan D. KarpelSarah S. Kernasovskiy, Stephen E. Kuenstner, Chao Lin Kuo, Dale Li, John A.B. Mates, Carl D. Reintsema, Stephen R. Smith, Joel Ullom, Leila R. Vale, Daniel D. Van Winkle, Michael Vissers, Cyndia Yu

Research output: Chapter in Book/Report/Conference proceedingConference contribution

35 Scopus citations


The next generation of cryogenic CMB and submillimeter cameras under development require densely instrumented sensor arrays to meet their science goals. The readout of large numbers (∼10,000-100,000 per camera) of sub-Kelvin sensors, for instance as proposed for the CMB-S4 experiment, will require substantial improvements in cold and warm readout techniques. To reduce the readout cost per sensor and integration complexity, efforts are presently focused on achieving higher multiplexing density while maintaining readout noise subdominant to intrinsic detector noise and presenting manageable thermal loads. Highly-multiplexed cold readout technologies in active development include Microwave Kinetic Inductance Sensors (MKIDs) and microwave rf-SQUIDs. Both exploit the high quality factors of superconducting microwave resonators to densely channelize sub-Kelvin sensors into the bandwidth of a microwave transmission line. In the case of microwave SQUID multiplexing, arrays of transition-edge sensors (TES) are multiplexed by coupling each TES to its own superconducting microwave resonator through an rf-SQUID. We present advancements in the development of a new warm readout system for microwave SQUID multiplexing, the SLAC Superconducting Microresonator RF electronics, or SMuRF, by adapting SLAC National Accelerator Laboratory's Advanced Telecommunications Computing Architecture (ATCA) FPGA Common Platform. SMuRF aims to read out 4000 microwave SQUID channels between 4 and 8 GHz per RF line. Each compact SMuRF system is built onto a single ATCA carrier blade. Daughter boards on the blade implement RF frequency-division multiplexing using FPGAs, fast DACs and ADCs, and an analog up-and down-conversion chain. The system reads out changes in flux in each resonator-coupled rf-SQUID by monitoring the change in the transmitted amplitude and frequency of RF tones produced at each resonator's fundamental frequency. The SMuRF system is unique in its ability to track each tone, minimizing the total RF power required to readout each resonator, thereby significantly reducing the linearity requirements on the cold and warm readout. Here, we present measurements of the readout noise and linearity of the first full SMuRF system, including a demonstration of closed-loop tone tracking on a 528 channel cryogenic microwave SQUID multiplexer. SMuRF is being explored as a potential readout solution for a number of future CMB projects including Simons Observatory, BICEP Array, CCAT-prime, Ali-CPT, and CMB-S4. In addition, parallel development of the platform is underway to adapt SMuRF to read out both MKID and fast X-ray TES calorimeter arrays.

Original languageEnglish (US)
Title of host publicationMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX
EditorsJonas Zmuidzinas, Jian-Rong Gao
ISBN (Print)9781510619692
StatePublished - 2018
Externally publishedYes
EventMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX 2018 - Austin, United States
Duration: Jun 12 2018Jun 15 2018

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


OtherMillimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX 2018
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


  • Cosmic Microwave Background (CMB)
  • FPGA-based RF Readout Electronics
  • Linearity
  • Microwave SQUID Multiplexing
  • MKIDs
  • Multiplexing
  • Tone tracking
  • Transition Edge Sensor Arrays


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