Published May 2020 | Version Accepted Version
Journal Article Open

Optical Characterization of the Keck Array and BICEP3 CMB Polarimeters from 2016 to 2019

Abstract

The BICEP/Keck experiment (BK) is a series of small-aperture refracting telescopes observing degree-scale cosmic microwave background (CMB) polarization from the South Pole in search of a primordial B-mode signature. This B-mode signal arises from primordial gravitational waves interacting with the CMB and has amplitude parametrized by the tensor-to-scalar ratio r. Since 2016, BICEP3 and the Keck Array have been observing with 4800 total antenna-coupled transition-edge sensor detectors, with frequency bands spanning 95, 150, 220, and 270 GHz. Here we present the optical performance of these receivers from 2016 to 2019, including far-field beams measured in situ with an improved chopped thermal source and instrument spectral response measured with a field-deployable Fourier transform spectrometer. As a pair differencing experiment, an important systematic that must be controlled is the differential beam response between the co-located, orthogonally polarized detectors. We generate per-detector far-field beam maps and the corresponding differential beam mismatch that is used to estimate the temperature-to-polarization leakage in our CMB maps and to give feedback on detector and optics fabrication. The differential beam parameters presented here were estimated using improved low-level beam map analysis techniques, including efficient removal of non-Gaussian noise as well as improved spatial masking. These techniques help minimize systematic uncertainty in the beam analysis, with the goal of constraining the bias on r induced by temperature-to-polarization leakage to be subdominant to the statistical uncertainty. This is essential as we progress to higher detector counts in the next generation of CMB experiments.

Additional Information

© 2020 Springer Nature Switzerland AG. Received 31 August 2019; Accepted 05 February 2020; Published 24 February 2020. The BICEP/Keck projects have been made possible through a series of Grants from the National Science Foundation including 0742818, 0742592, 1044978, 1110087, 1145172, 1145143, 1145248, 1639040, 1638957, 1638978, 1638970, and 1726917, by the Gordon and Betty Moore Foundation, by the Keck Foundation, and by the Grant 55802 from John Templeton Foundation. The development of antenna-coupled detector technology was supported by the JPL Research and Technology Development Fund and NASA Grants 06-ARPA206-0040, 10-SAT10-0017, 12-SAT12-0031, 14-SAT14-0009 and 16-SAT16-0002. The development and testing of focal planes were supported by the Gordon and Betty Moore Foundation at Caltech. Readout electronics were supported by a Canada Foundation for Innovation grant to UBC. The computations in this paper were run on the Odyssey cluster supported by the FAS Science Division Research Computing Group at Harvard University. The analysis effort at Stanford and SLAC is partially supported by the U.S. DoE Office of Science. We thank the staff of the U.S. Antarctic Program and in particular the South Pole Station without whose help this research would not have been possible. We thank all those who have contributed past efforts to the BICEP/Keck series of experiments, including the Bicep1 team. Tireless administrative support was provided by Kathy Deniston, Sheri Stoll, Irene Coyle, Donna Hernandez, Dana Volponi, and Julie Shih.

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Additional details

Identifiers

Eprint ID
101528
DOI
10.1007/s10909-020-02392-8
Resolver ID
CaltechAUTHORS:20200225-100023216

Funding

NSF
OPP-0742818
NSF
OPP-0742592
NSF
OPP-1044978
NSF
PLR-1110087
NSF
OPP-1145172
NSF
OPP-1145143
NSF
OPP-1145248
NSF
OPP-1639040
NSF
OPP-1638957
NSF
OPP-1638978
NSF
OPP-1638970
NSF
OPP-1726917
Gordon and Betty Moore Foundation
W. M. Keck Foundation
John Templeton Foundation
55802
JPL Research and Technology Development Fund
NASA
06-ARPA206-0040
NASA
10-SAT10-0017
NASA
12-SAT12-0031
NASA
14-SAT14-0009
NASA
16-SAT16-0002
Canada Foundation for Innovation
Harvard University
Department of Energy (DOE)

Dates

Created
2020-02-25
Created from EPrint's datestamp field
Updated
2023-03-16
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Astronomy Department