Hi all Below is a draft abstract I'm planning to submit for SPIE 2014. The deadline is Monday, and I'm currently in transit to Pole so that makes coordination a bit difficult. I plan to submit when it is Monday in NZ time, after ECW issue. I will try to address all comments received by that time; although, I may not be able to email you back until later. Also, I haven't slept in ~30 hours, so if this email is incoherent, that's why. Eric especially let me know if you want me to put something to integrate better with your abstract. Although I'm not planning to say anything about BICEP3 besides a brief advertisement, I'm CCing BICEP3 list in case they want anything more/less. Title: BICEP2 and Keck Array: Upgrades and Improved Beam Characterization Finding evidence for inflation by detecting B-modes in the cosmic microwave background (CMB) polarization at large angular scales remains one of the most compelling experimental challenges in cosmology today. BICEP2 and the Keck Array are part of a program of experiments at the South Pole whose main goal is to demonstrate the sensitivity and systematic control necessary for tensor-to-scalar ratio r <~ 0.01 measurements. Beam imperfections that are not sufficiently accounted for are a major potential source of spurious polarization that could interfere with that goal. The strategy of BICEP2 and Keck Array is to completely characterize their telescopes' polarized beam response with a combination of in-lab, pre-deployment, and on-site calibrations. I will 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 below r ~ 0.01. Similar measurements have been made for the Keck Array. On-site measurements of Keck Array showed unexpected side lobes that were terminating on the absorptive telescope forebaffles. Follow-up lab measurements confirmed these side lobes were due to inadequate blackening of the cryogenic telescopes, and in late 2013 the five telescopes were upgraded on site with improved interior baffles. These baffles have substantially reducted total optical loading, leading to a ~ 10% increase in mapping speed for the 2014 observing season. The sensitivity of Keck Array continues to improve: for the 2013 season it was 9.5 uK*sqrt(s) NET. In 2014 we converted two of the 150 GHz cameras to 100 GHz for foreground separation. The sensitivity at 100 GHz is ~ 20 uK*sqrt(s) per camera. We have shown that the BICEP2/Keck telescope technology is sufficient for the goal of measuring r at the 0.01 level. We expect to publish such measurements soon. Furthermore, the program is continuing with BICEP3, a 100-GHz telescope with ??? detectors. Immanuel Buder Postdoctoral Fellow Harvard-Smithsonian Center for Astrophysics (office) 617 495 7567 (office) 160 Concord Ave., M-114C (mail) 60 Garden St. MS 42 Cambridge, MA 02138 ibuder(a)gmail.com <mailto:ibuder@gmail.com> <mailto:ibuder@cfa.harvard.edu> _______________________________________________ Bicep2-list mailing list Bicep2-list(a)lists.fas.harvard.edu https://lists.fas.harvard.edu/mailman/listinfo/bicep2-list