Simons Observatory: characterizing the Large Aperture Telescope Receiver with radio holography

Journal Article · Thu Dec 01 00:00:00 UTC 2022 · Applied Optics

DOI: https://doi.org/10.1364/ao.470138 · OSTI ID:1909886

Chesmore, Grace E.  ^[1]; Harrington, Kathleen ^[1]; Sierra, Carlos E. ^[1]; Gallardo, Patricio A. ^[2]; Sutariya, Shreya ^[1]; Alford, Tommy ^[1]; Adler, Alexandre E. ^[3]; Bhandarkar, Tanay ^[4]; Coppi, Gabriele ^[5]; Dachlythra, Nadia ^[3]; Golec, Joseph ^[1]; Gudmundsson, Jon  ^[3]; Haridas, Saianeesh K. ^[4]; Johnson, Bradley R. ^[6]; Kofman, Anna M. ^[4]; Iuliano, Jeffrey ^[4]; McMahon, Jeff ^[7]; Niemack, Michael D. ^[8]; Orlowski-Scherer, John ^[4]; Perez Sarmiento, Karen ^[4] ; Puddu, Roberto ^[9]; Silva-Feaver, Max ^[10]; Simon, Sara M. ^[11]; Robe, Julia ^[4]; Wollack, Edward J.  ^[12]; Xu, Zhilei  ^[13]

---

1. University of Chicago, IL (United States)
2. University of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP)
3. Stockholm University (Sweden)
4. University of Pennsylvania, Philadelphia, PA (United States)
5. University of Milano-Bicocca, Milan (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Milano (Italy)
6. University of Chicago, IL (United States). Enrico Fermi Institute
7. University of Chicago, IL (United States); University of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP); University of Chicago, IL (United States). Enrico Fermi Institute; University of Virginia, Charlottesville, VA (United States)
8. Cornell University, Ithaca, NY (United States)
9. Pontificia Universidad Católica de Chile, Santiago (Chile)
10. University of California, San Diego, CA (United States)
11. Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
12. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
13. Massachusetts Institute of Technology (MIT), Cambridge, MA (United States)

Here, we present near-field radio holography measurements of the Simons Observatory Large Aperture Telescope Receiver optics. These measurements demonstrate that radio holography of complex millimeter-wave optical systems comprising cryogenic lenses, filters, and feed horns can provide detailed characterization of wave propagation before deployment. We used the measured amplitude and phase, at 4 K, of the receiver near-field beam pattern to predict two key performance parameters: 1) the amount of scattered light that will spill past the telescope to 300 K and 2) the beam pattern expected from the receiver when fielded on the telescope. These cryogenic measurements informed the removal of a filter, which led to improved optical efficiency and reduced sidelobes at the exit of the receiver. Holography measurements of this system suggest that the spilled power past the telescope mirrors will be less than 1%, and the main beam with its near sidelobes are consistent with the nominal telescope design. This is the first time such parameters have been confirmed in the lab prior to deployment of a new receiver. This approach is broadly applicable to millimeter and submillimeter instruments.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE; USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: AC02-07CH11359
• OSTI ID: 1909886
• Report Number(s): FERMILAB-PUB-22-111-PPD; arXiv:2207.07040; oai:inspirehep.net:2621856
• Journal Information: Applied Optics, Journal Name: Applied Optics Journal Issue: 34 Vol. 61; ISSN 1559-128X
• Publisher: Optical Society of AmericaCopyright Statement
• Country of Publication: United States
• Language: English