Optical Characterization of the Keck Array Polarimeter at the South Pole
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.
Additional Information© 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). The Keck Array is supported by the National Science Foundation, Grant No. ANT-1044978/ANT-1110087, and by the Keck Foundation. AGV gratefully acknowledges support from the National Science Foundation, Grant No. ANT-1103553. We are also grateful to Robert Schwarz for spending the winter at the South Pole in both 2011 and 2012 for this project, and to the South Pole Station logistics team. We thank our Bicep2, Keck Array, and Spider colleagues for useful discussions and shared expertise.
Published - 845226.pdf
Submitted - 1208.0844v1.pdf