Optical Characterization of the Keck Array Polarimeter at the South Pole

• Main Authors: Vieregg, A. G., Aikin, R., Bock, J. J., Brevik, J. A., Dowell, C. D., Filippini, J. P., Golwala, S. R., Hristov, V. V., Lueker, M., Nguyen, H. T., O'Brient, R., Runyan, M., Staniszewski, Z., Teply, G.
• Other Authors: Holland, Wayne S., Zmuidzinas, J.
• Format: Book Part
• Language: English
• Published: Society of Photo-Optical Instrumentation Engineers (SPIE) 2012
• Subjects: Austral; South Pole; South pole
• Online Access: https://authors.library.caltech.edu/71473/; https://authors.library.caltech.edu/71473/1/845226.pdf; https://authors.library.caltech.edu/71473/2/1208.0844v1.pdf; https://resolver.caltech.edu/CaltechAUTHORS:20161025-153533537

The Keck Array (SPUD) is a set of microwave polarimeters that observes from the South Pole at degree angular scales in search of a signature of Inflation imprinted as B-mode polarization in the Cosmic Microwave Background (CMB). The first three Keck Array receivers were deployed during the 2010-2011 Austral summer, followed by two new receivers in the 2011-2012 summer season, completing the full five-receiver array. All five receivers are currently observing at 150 GHz. The Keck Array employs the field-proven BICEP/ BICEP2 strategy of using small, cold, on-axis refractive optics, providing excellent control of systematics while maintaining a large field of view. This design allows for full characterization of far-field optical performance using microwave sources on the ground. We describe our efforts to characterize the main beam shape and beam shape mismatch between co-located orthogonally-polarized detector pairs, and discuss the implications of measured differential beam parameters on temperature to polarization leakage in CMB analysis.