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 μ 1/4K 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.
Original language | English (US) |
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Title of host publication | Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII |
Editors | Jonas Zmuidzinas, Wayne S. Holland |
Publisher | SPIE |
ISBN (Electronic) | 9780819496218 |
DOIs | |
State | Published - 2014 |
Externally published | Yes |
Event | Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII - Montreal, Canada Duration: Jun 24 2014 → Jun 27 2014 |
Publication series
Name | Proceedings of SPIE - The International Society for Optical Engineering |
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Volume | 9153 |
ISSN (Print) | 0277-786X |
ISSN (Electronic) | 1996-756X |
Other
Other | Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII |
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Country/Territory | Canada |
City | Montreal |
Period | 6/24/14 → 6/27/14 |
Keywords
- BICEP2
- Cosmic microwave background
- Gravitational waves
- Ination
- Keck Array.
- polarization
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Computer Science Applications
- Applied Mathematics
- Electrical and Electronic Engineering