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Parallel session P3-1: Status of reference design overview from P1 and P2 (chair: J. Ruhl)

Reference Instrument spreadsheet

Notes from session (Tuesday, March 6, 11:15-12:45)

Reference Design Discussion Notes: 06-Mar-2018

Telescope (Nils Halverson):

  • Small aperture tel. design: Motion to require <46 cm refractor, to enable silicon lenses. Comment from Kovac that simulations assumed something larger, he thinks 55 cm. Simulation group needs to check this. One backup would to allow larger (alumina) lenses for LF band.
  • Ruhl: Did you discuss multiple telescopes per mount for small aperture? Nils: No, we didnt. Some concern about BiCEP-array with 4 tubes might change requirements on mount. Kovac: Mentions that BICEP-array has costing for 4-tubes / small aperture option to help Reference design.

Cryostat and Optics (Abby Vieregg):

  • Overall, group made a lot of decisions, and moved surprisingly fast.

Detectors (Tom Cecil):

  • Also lots of progress on decisions
  • Only outstanding decision on spreadsheet was coupling technology, but agreed there should be some cost / sch / sci analysis, with others listed as strong options.

Readout (Amy Bender):

  • Decided we should use one technology, but couldn’t settle on which one.


  • How do we move Readout decision forward? Can we get teams / advocates for each technology and they can report back with more info that would help?
  • Keith mentioned that beam and polarization calibration wasnt discussed, would hope that its important aspect that goes into Reference design.
  • Ruhl mentions that detector testing wasnt discussed, e.g., but other things are missing too, that we might have missed.
  • Question about how TD group will be organized in future. Brad comments about proposal to organize telecons+groups around Reference design writing assignments. Carlstrom agrees, and that will be the place for TD group to give input.

Action Items / Homework:

  • Forecasting: Push through forecasting for 46 cm telescopes.
  • Forecasting: Push through forecasting at low-ell performance in Chile with just detector differencing .
  • Readout: Assemble a team in the next ~week, to assemble spec’s for readout to compare. Comparison should include NEP’s (e.g., phonon, photon, readout, etc.), and on-sky vs in-lab performance (different rows).
  • Readout: Need input from Reference Design writing team, to understand relative waiting for on-sky performance vs future technical promise. Action item uncertain.
  • Readout: Need input about Cost. Padin was volunteered to do this for uMUX, fMUX, tMUX.
  • Detectors: Toki and Sara will compare lenslet vs horn-coupled technology, and optimization for CMB-S4.