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BICEP2 and Keck Array: upgrades and improved beam characterization

Buder, I. and Aikin, R. W. and Bock, J. J. and Brevik, J. A. and Crill, B. P. and Filippini, J. P. and Golwala, S. R. and Hildebrandt, S. R. and Hristov, V. V. and Hui, H. and Kefeli, S. and Lueker, M. and Mason, P. and Staniszewski, Z. K. and Teply, G. P. and Weber, A. C. (2014) BICEP2 and Keck Array: upgrades and improved beam characterization. In: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. Proceedings of SPIE. No.5193. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 915312. ISBN 978-0-8194-9621-8.

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Searching for evidence of inflation by measuring B-modes in the cosmic microwave background (CMB) polarization at degree angular scales remains one of the most compelling experimental challenges in cosmology. BICEP2 and the Keck Array are part of a program of experiments at the South Pole whose main goal is to achieve the sensitivity and systematic control necessary for measurements of the tensor-to-scalar ratio at σ(r) ~0:01. Beam imperfections that are not sufficiently accounted for are a potential source of spurious polarization that could interfere with that goal. The strategy of BICEP2 and the Keck Array is to completely characterize their telescopes' polarized beam response with a combination of in-lab, pre-deployment, and on-site calibrations. We report the status of these experiments, focusing on continued improved understanding of their beams. Far-field measurements of the BICEP2 beam with a chopped thermal source, combined with analysis improvements, show that the level of residual beam-induced systematic errors is acceptable for the goal of σ(r)~ 0:01 measurements. Beam measurements of the Keck Array side lobes helped identify a way to reduce optical loading with interior cold baffles, which we installed in late 2013. These baffles reduced total optical loading, leading to a ~ 10% increase in mapping speed for the 2014 observing season. The sensitivity of the Keck Array continues to improve: for the 2013 season it was 9:5 μK _/s noise equivalent temperature (NET). In 2014 we converted two of the 150-GHz cameras to 100 GHz for foreground separation capability. We have shown that the BICEP2 and the Keck Array telescope technology is sufficient for the goal of σ(r) ~ 0:01 measurements. Furthermore, the program is continuing with BICEP3, a 100-GHz telescope with 2560 detectors.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Bock, J. J.0000-0002-5710-5212
Crill, B. P.0000-0002-4650-8518
Filippini, J. P.0000-0001-8217-6832
Golwala, S. R.0000-0002-1098-7174
Mason, P.0000-0002-7963-7420
Additional Information:© 2014 Society of Photo-Optical Instrumentation Engineers (SPIE). August 19, 2014. The Bicep2 and the Keck Array projects have been made possible through support from the National Science Foundation (grant Nos. ANT-0742818, ANT-0742592, ANT-1044978, ANT-1110087, and ANT-1145172), the W. M. Keck Foundation, the Canada Foundation for Innovation, and the British Columbia Development Fund. The development of antenna-coupled detector technology was supported by the JPL Research and Technology Development Fund and grants 06-ARPA206-0040 and 10-SAT10-0017 from the NASA APRA and SAT programs. The development and testing of focal planes were supported by the Gordon and Betty Moore Foundation at Caltech. The computations in these proceedings were run on the Odyssey cluster supported by the FAS Science Division Research Computing Group at Harvard University. Tireless administrative support was provided by Irene Coyle and Kathy Deniston. We are grateful to Steffen Richter as our 2010-2012 Bicep2 winter-over, and to Robert Schwarz as our 2011-2014 Keck Array winter-over. We thank the staff of the US Antarctic Program and in particular the South Pole Station without whose help this research would not have been possible. We thank our BICEP1 and SPIDER colleagues for useful discussions and shared expertise.
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Canada Foundation for InnovationUNSPECIFIED
British Columbia Development FundUNSPECIFIED
JPL Research and Technology Development FundUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Harvard UniversityUNSPECIFIED
Subject Keywords:Inflation, Gravitational waves, Cosmic microwave background, polarization, BICEP2, Keck Array
Series Name:Proceedings of SPIE
Issue or Number:5193
Record Number:CaltechAUTHORS:20150615-094055757
Persistent URL:
Official Citation:I. Buder ; P. A. R. Ade ; Z. Ahmed ; R. W. Aikin ; K. D. Alexander, et al. "BICEP2 and Keck array: upgrades and improved beam characterization", Proc. SPIE 9153, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII, 915312 (August 19, 2014); doi:10.1117/12.2055713
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58238
Deposited By: Ruth Sustaita
Deposited On:15 Jun 2015 17:45
Last Modified:10 Nov 2021 22:01

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