BICEP2 and Keck Array: upgrades and improved beam characterization

Zmuidzinas, Jonas, Buder, I., Ade, Peter A. R. ORCID: https://orcid.org/0000-0002-5127-0401, Ahmed, Z., Aikin, R. W., Alexander, K. D., Amiri, M., Barkats, D., Benton, S. J., Bischoff, C. A., Bock, J. J., Bonetti, J. A., Brevik, J. A., Bullock, E., Burger, B., Crill, B. P., Davis, G., Dowell, C. D., Duband, L., Filippini, J. P., Fliescher, S., Golwala, S. R., Gordon, M. S., Halpern, M., Hasselfield, M., Hildebrandt, S. R., Hilton, G. C., Hristov, V. V., Hui, H., Irwin, K. D., Karkare, K. S., Kaufman, J. P., Keating, B. G., Kefeli, S., Kernasovskiy, S. A., Kovac, J. M., Kuo, C. L., Leitch, E. M., Lueker, M., Mason, P., Megerian, K. G., Netterfield, C. B., Nguyen, H. T., O'Brient, R., Ogburn, R. W., Orlando, A., Pryke, C., Reintsema, C. D., Richter, S., Schwarz, R., Sheehy, C. D., Staniszewski, Z. K., Sudiwala, Rashmikant ORCID: https://orcid.org/0000-0003-3240-5304, Teply, G. P., Thompson, K. L., Tolan, J. E., Turner, A. D., Vieregg, A. G., Weber, A. C., Wiebe, D. V., Wilson, P., Wong, C. L. and Yoon, K. W. 2014. BICEP2 and Keck Array: upgrades and improved beam characterization. Presented at: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII, Montréal, Quebec, Canada, 22 June 2014. Proc. SPIE 9153, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. , vol.9153 Society of Photo-optical Instrumentation Engineers, p. 915312. 10.1117/12.2055713

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Abstract

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 Sereport 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. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Item Type:	Conference or Workshop Item (Paper)
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Publisher:	Society of Photo-optical Instrumentation Engineers
ISSN:	0277-786X
Last Modified:	01 Nov 2022 09:58
URI:	https://orca.cardiff.ac.uk/id/eprint/89799

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