Optical modeling of systematic uncertainties in detector polarization angles for the Atacama Cosmology Telescope
arxiv(2024)
摘要
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 measurements. 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 90–220 GHz to be at the tenth 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 can inform
polarization angle systematic uncertainties for current and future microwave
polarimeters, such as the CCAT Observatory, Simons Observatory, and CMB-S4.
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