We measure linearly polarized beam patterns for a multi-moded concentrator and compare the results to a simple model based on geometric optics. We convolve the measured co-polar and cross-polar beams with simulated maps of CMB polarization to estimate the amplitude of the systematic error resulting from the cross-polar beam response. The un-corrected error signal has typical amplitude of 3 nK, corresponding to inflationary B-mode amplitude r ~ 10^{-3}. Convolving the measured cross-polar beam pattern with maps of the CMB E-mode polarization provides a template for correcting the cross-polar response, reducing it to negligible levels.
@article{arxiv.1801.08971,
title = {Polarized Beam Patterns from a Multi-Moded Feed For Observations of the Cosmic Microwave Background},
author = {A. Kogut and D. J. Fixsen},
journal= {arXiv preprint arXiv:1801.08971},
year = {2018}
}
Comments
16 pages including 8 figurers. Accepted for publication in the Journal of Astronomical Telescopes, Instruments, and Systems