The Simons Observatory: Magnetic Shielding Measurements for the Universal Multiplexing Module

Journal Article · Mon Sep 26 00:00:00 UTC 2022 · Journal of Low Temperature Physics

DOI: https://doi.org/10.1007/s10909-022-02875-w · OSTI ID:1998024

Huber, Zachary B.  ^[1]; Li, Yaqiong ^[2]; Vavagiakis, Eve M. ^[2]; Choi, Steve K. ^[2]; Connors, Jake ^[3]; Cothard, Nicholas F. ^[4]; Duell, Cody J. ^[2]; Galitzki, Nicholas ^[5]; Healy, Erin ^[6]; Hubmayr, Johannes ^[7]; Johnson, Bradley R. ^[8]; Keller, Ben ^[2]; McCarrick, Heather ^[6]; Niemack, Michael D. ^[2]; Wang, Yuhan ^[6]; Xu, Zhilei ^[9]; Zheng, Kaiwen ^[6]

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1. Cornell University, Ithaca, NY (United States); SLAC
2. Cornell University, Ithaca, NY (United States)
3. National Institute of Standards and Technology (NIST), Boulder, CO (United States); University of Colorado, Boulder, CO (United States)
4. NASA Goddard Space Flight Center, Greenbelt, MD (United States)
5. University of California San Diego, La Jolla, CA (United States)
6. Princeton University, NJ (United States)
7. National Institute of Standards and Technology (NIST), Boulder, CO (United States)
8. University of Virginia, Charlottesville, VA (United States)
9. Massachusetts Institute of Technology, Cambridge, MA (United States)

The Simons Observatory (SO) includes four telescopes that will measure the temperature and polarization of the cosmic microwave background using over 60,000 highly sensitive transition-edge bolometers (TES). These multichroic TES bolometers are read out by a microwave RF SQUID multiplexing system with a multiplexing factor of 910. Given that both TESes and SQUIDs are susceptible to magnetic field pickup and that it is hard to predict how they will respond to such fields, it is important to characterize the magnetic response of these systems empirically. This information can then be used to limit spurious signals by informing magnetic shielding designs for the detectors and readout. This paper focuses on measurements of magnetic pickup with different magnetic shielding configurations for the SO universal multiplexing module (UMM), which contains the SQUIDs, associated resonators, and TES bias circuit. The magnetic pickup of a prototype UMM was tested under three shielding configurations: no shielding (copper packaging), aluminum packaging for the UMM, and a tin/lead-plated shield surrounding the entire dilution refrigerator 100 mK cold stage. We also present measurements of the pickup in the UMM when aluminum feedhorns are installed. The measurements show that the aluminum packaging outperforms the copper packaging by a shielding factor of 8-10, and adding the tin/lead-plated 1K shield further increases the relative shielding factor in the aluminum configuration by 1-2 orders of magnitude. Furthermore, the addition of feedhorns provides a factor of 30 improvement when the tin/lead shield is not installed and a factor of 5 improvement when it is.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: Gordon and Betty Moore Foundation; National Science Foundation (NSF); USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1998024
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 3-4 Vol. 209; ISSN 0022-2291
• Publisher: Springer NatureCopyright Statement
• Country of Publication: United States
• Language: English