Detailed study of HWP non-idealities and their impact on future measurements of CMB polarization anisotropies from space

Abstract

We study the propagation of a specific class of instrumental systematics to the reconstruction of the B-mode power spectrum of the cosmic microwave background (CMB). We focus on the non-idealities of the half-wave plate (HWP), a polarization modulator that is to be deployed by future CMB experiments, such as the phase-A satellite mission LiteBIRD. We study the effects of non-ideal HWP properties, such as transmittance, phase shift, and cross-polarization. To this end, we developed a simple, yet stand-alone end-to-end simulation pipeline adapted to LiteBIRD. We analyzed the effects of a possible mismatch between the measured frequency profiles of HWP properties (used in the mapmaking stage of the pipeline) and the actual profiles (used in the sky-scanning step). We simulated single-frequency, CMB-only observations to emphasize the effects of non-idealities on the BB power spectrum. We also considered multi-frequency observations to account for the frequency dependence of HWP properties and the contribution of foreground emission. We quantified the systematic effects in terms of a bias Δr on the tensor-to-scalar ratio, r, with respect to the ideal case without systematic effects. We derived the accuracy requirements on the measurements of HWP properties by requiring Δr < 10−5 (1% of the expected LiteBIRD sensitivity on r). Our analysis is introduced by a detailed presentation of the mathematical formalism employed in this work, including the use of the Jones and Mueller matrix representations.

Probing cosmic inflation with theLiteBIRDcosmic microwave background polarization survey

“…The goal of our second study is to set requirements on the accuracy needed to constrain departures of the HWP from the ideal setup. Requirements are set by imposing a threshold on the maximum bias ∆r that we could tolerate being due to a combination of HWP systematic effects, including the effect of frequency-dependent HWP parameters [306,307].…”

New physics from the polarised light of the cosmic microwave background

“…Miscalibration of polarisation-sensitive orientations of detectors on the focal plane of a telescope with respect to the sky as well as cross-polarisation coupling induced by systematics of beam [283][284][285][286] and optical components such as half-wave plates [287][288][289] yield α, hence a spurious B-mode power spectrum, C BB,o = sin 2 (2α)C EE . Reducing this to sufficiently small level required for the B-mode science sets a requirement for α, which is below 0.2 •290 or even below 0.1 •291 (see Fig.…”

Wide-field polarization angle measurements of a LiteBIRD low-frequency telescope scaled antenna

“…The Jones matrix for the rotating half-wave plate, boldJHWP, is discussed in Ref. 28. The Jones matrix for the feed, Jfeed, can be written as 27 Jfeed=(100η),where η represents the cross-polarization leakage of the detector.…”

“…The Jones matrix for the rotating half-wave plate, J HWP , is discussed in Ref. 28. The Jones matrix for the feed, J feed , can be written as 27 E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 4 ; 1 1 6 ; 5 8 7…”