UMICH-2015: Instrumentation I break-out session 2

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Goals: Analyze technology status and progress needed to read out direct detectors on the scale of CMB-S4. Please note that direct coherent amplification of CMB signals (with HEMT or other amplifiers) is covered in the detector session.

  1. Identify requirements for CMB-S4 polarimeter readout electronics, including both cryogenic and room-temperature components
  2. Review status of existing technologies with particular attention to assessing feasibility for scaling to the total pixel count of CMB-S4 (order of 500,000 total across multiple platforms) and cost
  3. Identify work that needs to be done in order to complete maturation of candidate technologies.

Please come prepared to describe readout techniques for CMB detectors as described above. If you have a slide to add, please post it on the wiki. If you think of additional questions or topics for debate, please add those as well.


CMB Polarimeter readout technology

  1. Time-division multiplexing for TES Bolometers
  2. Frequency-division multiplexing for ac-biased TES Bolometers
  3. Microwave-resonator multiplexing for dc-biased TES Bolometers: microwave SQUIDs, KPUPs, or direct readout with quantum-limited amplifiers
  4. Microwave-resonator readout of MKIDs

Top-level requirements for discussion


  • O($100 / pixel) is too much
  • O($10 / pixel) is about right
  • O($1 / pixel) may not be worth the R&D cost

Noise lower than the sensor

Scalable to O[500,000] sensors

  • Physical size of components
  • sub-Kelvin mass of components
  • Power dissipation per pixel
  • Focal-plane interconnects

Can wirebonds from each pixel out of the focal plane work for CMB-S4?

Bump-bond hybridization?

On-wafer multiplexing elements? (LC resonators coupled to TESs or MKIDs)

Acceptable crosstalk

  • Nearest neighbor
  • Distant pixel

Acceptable sub-Kelvin mass

Acceptable power dissipation at all T stages

Readout components

  1. Cryogenic requirements
  2. Focal-plane interconnects / hybridization
  3. Wiring requirements
  4. Room-temperature electronics requirements

Advantages/Disadvantages, Systematic Mitigation Strategy

  1. Technological maturity
  2. Fabrication complexity, yield, uniformity
  3. Scalability to order [500,000] detectors
  4. Cost

Required Work or Studies

  1. What is technological readiness?
  2. What are unknowns?
  3. What is timeline for development?