Affiliation:
1. Cornell University
2. The University of Chicago
3. University of Pennsylvania
4. Flatiron Institute
5. Yale University
6. University of Oslo
7. Princeton University
8. West Chester University
9. NASA/Goddard Space Flight Center
Abstract
We present an estimate of the Atacama Cosmology Telescope (ACT)
detector polarization angle systematic uncertainty from optics
perturbation analysis using polarization-sensitive ray tracing in CODE
V optical design software. Uncertainties in polarization angle
calibration in CMB measurements can limit constraints on cosmic
birefringence and other cosmological parameters sensitive to
polarization leakage. Our framework estimates the angle calibration
systematic uncertainties from possible displacements in lens positions
and orientations, and anti-reflection coating (ARC) thicknesses and
refractive indices. With millimeter displacements in lens positions
and percent-level perturbations in ARC thicknesses and indices from
design, we find the total systematic uncertainty for three ACT
detector arrays operating between 90 and 220 GHz to be at the
10th of degree scale. Reduced lens position and orientation
uncertainties from physical measurements could lead to a reduction in
the systematic uncertainty estimated with the framework presented
here. This optical modeling may inform polarization angle systematic
uncertainties for current and future microwave polarimeters, such as
the CCAT Observatory, Simons Observatory, and CMB-S4.
Funder
Canada Foundation for
Innovation
University of Pennsylvania
Princeton University
National Science Foundation