Summary: | The Bicep2 and Keck Array experiments are designed to measure the polarization of the cosmic microwave background (CMB) on angular scales of 2-4 degrees (ℓ = 50–100). This is the region in which the B-mode signal, a signature prediction of cosmic inflation, is expected to peak. Bicep2 was deployed to the South Pole at the end of 2009 and is in the middle of its third year of observing with 500 polarization-sensitive detectors at 150 GHz. The Keck Array was deployed to the South Pole at the end of 2010, initially with three receivers—each similar to Bicep2. An additional two receivers have been added during the 2011-12 summer. We give an overview of the two experiments, report on substantial gains in the sensitivity of the two experiments after post-deployment optimization, and show preliminary maps of CMB polarization from Bicep2. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). The Bicep2 and Keck Array projects have been made possible through support from the National Science Foundation (grant Nos. ANT-1044978 / ANT-1110087), the Keck Foundation, the Canada Foundation for Innovation, and the British Columbia Development Fund. Detector development has been made possible by the generous support of the Gordon and Betty Moore Foundation. RWO gratefully acknowledges support from the Kavli Institute for Particle Astrophysics and Cosmology. We are grateful to Steffen Richter as our 2010-12 Bicep2 winter-over, and to Robert Schwarz as our 2011-12 Keck Array winter-over. The Bicep2 and Keck Array teams would also like to thank the South Pole Station staff for logistical support. We thank our Bicep and Spider colleagues for useful discussions and shared expertise. Published - 84521A.pdf
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