arXiv subjects

Alessandro Paiella

Publications and source records attributed to Alessandro Paiella.

9 recordsLinked to original sources

arXiv2026

Combining Systematic Effects in CMB Polarization Experiments through map-based simulations: application to LiteBIRD's HWP non-idealities and detectors non-linearity

We quantify the impact of coupled instrumental systematics on next-generation CMB polarization experiments targeting primordial $B$-mode polarization, with a focus on the forthcoming \textit{LiteBIRD} satellite mission. We study the interplay between the non-linear response of Transition-Edge Sensor (TES) bolometers and Half-Wave Plate (HWP) non-idealities, in particular synchronous signals arising from differential emissivity. We develop a map-based formalism that captures the resulting intensity-to-polarization leakage by explicitly solving the binning map-making equations, avoiding the need for computationally expensive time-ordered data simulations. We apply this framework to \textit{LiteBIRD}, adopting its baseline scanning strategy and frequency configuration, and perform analyses at both single- and multi-frequency levels, including Galactic foregrounds and blind component separation. We find that while detector non-linearity and HWP non-idealities individually induce negligible bias on the tensor-to-scalar ratio $r$, their coupling can generate non-trivial contamination, driven by large signals such as the solar dipole and amplified in high-frequency channels by foreground leakage. From these results, we derive joint requirements on detector non-linearity and HWP differential emission, and discuss their implications for the instrument design and calibration strategy of \textit{LiteBIRD} and future CMB polarization missions targeting $r \lesssim 10^{-3}$.

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arXiv2026

Flux jump correction in the QUBIC TES data pipeline

Flux jumps occur in the readout electronics of Transition Edge Sensor (TES) detectors coupled to Superconducting Quantum Interference Devices (SQUIDs), as a consequence of the periodic transfer function of SQUIDs in the superconducting regime. These events manifest as discontinuities in the Time Ordered Data (TOD) and can significantly degrade the quality of the measured signals. In this work, we present an automated pipeline to identify and correct flux jumps in the calibration data of the QUBIC (Q \& U Bolometric Interferometer for Cosmology) instrument, designed to measure the B-mode polarization of the Cosmic Microwave Background (CMB). Using data from multiple observation campaigns, we characterize the statistical properties of flux jumps and compare them with expectations based on the electronic configuration of the instrument. The proposed pipeline successfully corrects these events, allowing the recovery of affected data and enabling their use in subsequent CMB analysis.

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arXiv2024

Systematic effects induced by half-wave plate differential optical load and TES nonlinearity for LiteBIRD

LiteBIRD, a forthcoming satellite mission, aims to measure the polarization of the Cosmic Microwave Background (CMB) across the entire sky. The experiment will employ three telescopes, Transition-Edge Sensor (TES) bolometers and rotating Half-Wave Plates (HWPs) at cryogenic temperatures to ensure high sensitivity and systematic effects mitigation. This study is focused on the Mid- and High-Frequency Telescopes (MHFT), which will use rotating metal mesh HWPs. We investigate how power variations due to HWP differential emissivity and transmittance combine with TES nonlinear responsivity, resulting in an effective instrumental polarization. We present the results of simulations for the current HWP design, modeling the TES deviation from linearity as a second-order response. We quantify the level of acceptable residual nonlinearity assuming the mission requirement on the tensor-to-scalar ratio, $δr < 0.001$. Moreover, we provide an accuracy requirement on the measurement of TES responsivity nonlinearity level for MHFT channels. Lastly, we present possible mitigation methods that will be developed in future studies.

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arXiv2022

In-flight polarization angle calibration for LiteBIRD: blind challenge and cosmological implications

We present a demonstration of the in-flight polarization angle calibration for the JAXA/ISAS second strategic large class mission, LiteBIRD, and estimate its impact on the measurement of the tensor-to-scalar ratio parameter, r, using simulated data. We generate a set of simulated sky maps with CMB and polarized foreground emission, and inject instrumental noise and polarization angle offsets to the 22 (partially overlapping) LiteBIRD frequency channels. Our in-flight angle calibration relies on nulling the EB cross correlation of the polarized signal in each channel. This calibration step has been carried out by two independent groups with a blind analysis, allowing an accuracy of the order of a few arc-minutes to be reached on the estimate of the angle offsets. Both the corrected and uncorrected multi-frequency maps are propagated through the foreground cleaning step, with the goal of computing clean CMB maps. We employ two component separation algorithms, the Bayesian-Separation of Components and Residuals Estimate Tool (B-SeCRET), and the Needlet Internal Linear Combination (NILC). We find that the recovered CMB maps obtained with algorithms that do not make any assumptions about the foreground properties, such as NILC, are only mildly affected by the angle miscalibration. However, polarization angle offsets strongly bias results obtained with the parametric fitting method. Once the miscalibration angles are corrected by EB nulling prior to the component separation, both component separation algorithms result in an unbiased estimation of the r parameter. While this work is motivated by the conceptual design study for LiteBIRD, its framework can be broadly applied to any CMB polarization experiment. In particular, the combination of simulation plus blind analysis provides a robust forecast by taking into account not only detector sensitivity but also systematic effects.

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arXiv2021

The Crab Nebula as a Calibrator for wide-beam Cosmic Microwave Background polarization surveys

We analyze the effect of polarized diffuse emission in the calibration of wide-beam mm-wave polarimeters, when using the Crab Nebula as a reference source for both polarized brightness and polarization angle. We show that, for CMB polarization experiments aiming at detecting B-mode in a scenario with a tensor to scalar ratio $r \sim 0.001$, wide (a few degrees in diameter), precise ($σ_Q$ , $σ_U$ $\sim$ 20 $μ$$K_{CMB}$ arcmin), high angular resolution ($< \mathrm{FWHM}$) reference maps are needed to properly take into account the effects of diffuse polarized emission and avoid significant bias in the calibration.

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arXiv2021

A Polarization Modulator Unit for the Mid- and High-Frequency Telescopes of the LiteBIRD mission

The LiteBIRD mission is a JAXA strategic L-class mission for all sky CMB surveys which will be launched in the 2020s. The main target of the mission is the detection of primordial gravitational waves with a sensitivity ofthe tensor-to-scalar ratio δr <0.001. The polarization modulator unit (PMU) represents a critical and powerful component to suppress 1/f noise contribution and mitigate systematic uncertainties induced by detector gain drift, both for the high-frequency telescope (HFT) and for the mid-frequency telescope (MFT). Each PMUs based on a continuously-rotating transmissive half-wave plate (HWP) held by a superconducting magnetic bearing in a 5K environment. In this proceeding we will present the design and expected performance of the LiteBIRD PMUs and testing performed on every PMU subsystem with a room-temperature rotating disk used as a stand-in for the cryogenic HWP rotor.

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arXiv2020

A chemically etched corrugated feedhorn array for D-band CMB observations

We present the design, manufacturing, and testing of a 37-element array of corrugated feedhorns for Cosmic Microwave Background (CMB) measurements between $140$ and $170$ GHz. The array was designed to be coupled to Kinetic Inductance Detector arrays, either directly (for total power measurements) or through an orthomode transducer (for polarization measurements). We manufactured the array in platelets by chemically etching aluminum plates of $0.3$ mm and $0.4$ mm thickness. The process is fast, low-cost, scalable, and yields high-performance antennas compared to other techniques in the same frequency range. Room temperature electromagnetic measurements show excellent repeatability with an average cross polarization level about $-20$ dB, return loss about $-25$ dB, first sidelobes below $-25$ dB and far sidelobes below $-35$ dB. Our results qualify this process as a valid candidate for state-of-the-art CMB experiments, where large detector arrays with high sensitivity and polarization purity are of paramount importance in the quest for the discovery of CMB polarization $B$-modes.

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arXiv2019

QUBIC: Exploring the primordial Universe with the Q\&U Bolometric Interferometer

In this paper we describe QUBIC, an experiment that will observe the polarized microwave sky with a novel approach, which combines the sensitivity of state-of-the art bolometric detectors with the systematic effects control typical of interferometers. QUBIC unique features are the so-called "self-calibration", a technique that allows us to clean the measured data from instrumental effects, and its spectral imaging power, i.e. the ability to separate the signal in various sub-bands within each frequency band. QUBIC will observe the sky in two main frequency bands: 150 GHz and 220 GHz. A technological demonstrator is currently under testing and will be deployed in Argentina during 2019, while the final instrument is expected to be installed during 2020.

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arXiv2017

Exploring cosmic origins with CORE: gravitational lensing of the CMB

Lensing of the CMB is now a well-developed probe of large-scale clustering over a broad range of redshifts. By exploiting the non-Gaussian imprints of lensing in the polarization of the CMB, the CORE mission can produce a clean map of the lensing deflections over nearly the full-sky. The number of high-S/N modes in this map will exceed current CMB lensing maps by a factor of 40, and the measurement will be sample-variance limited on all scales where linear theory is valid. Here, we summarise this mission product and discuss the science that it will enable. For example, the summed mass of neutrinos will be determined to an accuracy of 17 meV combining CORE lensing and CMB two-point information with contemporaneous BAO measurements, three times smaller than the minimum total mass allowed by neutrino oscillations. In the search for B-mode polarization from primordial gravitational waves with CORE, lens-induced B-modes will dominate over instrument noise, limiting constraints on the gravitational wave power spectrum amplitude. With lensing reconstructed by CORE, one can "delens" the observed polarization internally, reducing the lensing B-mode power by 60%. This improves to 70% by combining lensing and CIB measurements from CORE, reducing the error on the gravitational wave amplitude by 2.5 compared to no delensing (in the null hypothesis). Lensing measurements from CORE will allow calibration of the halo masses of the 40000 galaxy clusters that it will find, with constraints dominated by the clean polarization-based estimators. CORE can accurately remove Galactic emission from CMB maps with its 19 frequency channels. We present initial findings that show that residual Galactic foreground contamination will not be a significant source of bias for lensing power spectrum measurements with CORE. [abridged]

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