Freeform three-mirror anastigmatic large-aperture telescope and receiver optics for CMB-S4

Creators: Gallardo, Patricio A.¹; Puddu, Roberto²; Harrington, Kathleen^{3, 1}; Benson, Bradford^{1, 4}; Carlstrom, John E.^{3, 1}; Dicker, Simon R.⁵; Emerson, Nick⁶; Gudmundsson, Jon E.^{7, 8}; Limon, Michele⁵; McMahon, Jeff^{1, 4}; Nagy, Johanna M.⁹; Natoli, Tyler¹; Niemack, Michael D.¹⁰; Padin, Stephen¹¹; Ruhl, John⁹; Simon, Sara M.⁴; the CMB-S4 Collaboration

1. University of Chicago
2. Pontificia Universidad Católica de Chile
3. Argonne National Laboratory
4. Fermilab
5. University of Pennsylvania
6. University of Arizona
7. Stockholm University
8. University of Iceland
9. Case Western Reserve University
10. Cornell University
11. California Institute of Technology

Abstract

CMB-S4, the next-generation ground-based cosmic microwave background (CMB) observatory, will provide detailed maps of the CMB at millimeter wavelengths to dramatically advance our understanding of the origin and evolution of the universe. CMB-S4 will deploy large- and small-aperture telescopes with hundreds of thousands of detectors to observe the CMB at arcminute and degree resolutions at millimeter wavelengths. Inflationary science benefits from a deep delensing survey at arcminute resolutions capable of observing a large field of view at millimeter wavelengths. This kind of survey acts as a complement to a degree angular resolution survey. The delensing survey requires a nearly uniform distribution of cameras per frequency band across the focal plane. We present a large-throughput (9.4° field of view), large-aperture (5-m diameter) freeform three-mirror anastigmatic telescope and an array of 85 cameras for CMB observations at arcminute resolutions, which meets the needs of the delensing survey of CMB-S4. A detailed prescription of this three-mirror telescope and cameras is provided, with a series of numerical calculations that indicates expected optical performance and mechanical tolerance.

Copyright and License

Data Availability

The optical design presented here can be reproduced using the tables in this document.

Funding

National Science Foundation (1935892, 2034402); Fermi Research Alliance, LLC (FRA) (DE-AC02-07CH11359); Swedish National Space Agency (SNSA/Rymdstyrelsen); Vetenskapsrådet (Reg. no. 2019-03959); European Commission (ERC, CMBeam, 101040169).

Acknowledgement

We acknowledge the valuable contribution of Richard Hills (1945–2022 [27]) to the optical design and optimization of the freeform three-mirror anastigmat presented here. We will sorely miss him. We acknowledge FONDEF ID21I10236 for supporting the licensing of the TICRA software, and the Geryon cluster at the Centro de Astro-Ingenieria UC, which was used for the full-wave calculations in this paper. BASAL CATA PFB-06, the Anillo ACT-86, FONDEQUIP AIC-57 and QUIMAL 130008 provided funding for the Geryon cluster. We thank Stig Busk Sørensen and the whole TICRA staff for their valuable help building the Grasp model. This document was prepared by the CMB-S4 collaboration using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA). JEG acknowledges support from the Swedish National Space Agency (SNSA/Rymdstyrelsen) and the Swedish Research Council. JEG also acknowledges support from the European Union.

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Resource type: Journal Article
Publisher: Optica Publishing Group
Published in: Applied Optics, 63(2), 310-321, ISSN: 1559-128X.
Languages: English