LiteBIRD, the next-generation cosmic microwave background (CMB) experiment, aims for a launch in Japan’s fiscal year 2032, marking a major advancement in the exploration of primordial cosmology and fundamental physics. Orbiting the Sun-Earth Lagrangian point L2, this JAXA-led strategic L-class mission will conduct a comprehensive mapping of the CMB polarization across the entire sky. During its 3-year mission, LiteBIRD will employ three telescopes within 15 unique frequency bands (ranging from 34 through 448 GHz), targeting a sensitivity of 2.2 μK-arcmin and a resolution of 0.5° at 100 GHz. Its primary goal is to measure the tensor-toscalar ratio r with an uncertainty δr = 0.001, including systematic errors and margin. If r ≥ 0.01, LiteBIRD expects to achieve a > 5σ detection in the ℓ = 2–10 and ℓ = 11–200 ranges separately, providing crucial insight into the early Universe. We describe LiteBIRD’s scientific objectives, the application of systems engineering to mission requirements, the anticipated scientific impact, and the operations and scanning strategies vital to minimizing systematic effects. We will also highlight LiteBIRD’s synergies with concurrent CMB projects.
In this paper we present the European Low Frequency Survey (ELFS), a project that will enable foregrounds-free measurements of the primordial B-mode polarization and a detection of the tensor-to-scalar ratio, r, to a level σ(r) = 0:001 by measuring the Galactic and extra-galactic emissions in the 5–120 GHz frequency window. Indeed, the main difficulty in measuring the B-mode polarization comes from the fact that many other processes in the Universe also emit polarized microwaves, which obscure the faint Cosmic Microwave Background (CMB) signal. The first stage of this project is being carried out in synergy with the Simons Array (SA) collaboration, installing a 5.5–11GHz (X-band) coherent receiver at the focus of one of the three 3.5m SA telescopes in Atacama, Chile, followed by the installation of the QUIJOTE-MFI2 in the 10–20 GHz range. We designate this initial iteration of the ELFS program as ELFS-SA. The receivers are equipped with a fully digital back-end that will provide a frequency resolution of 1MHz across the band, allowing us to clean the scientific signal from unwanted radio frequency interference, particularly from low-Earth orbit satellite mega constellations. This paper reviews the scientific motivation for ELFS and its instrumental characteristics, and provides an update on the development of ELFS-SA.
We develop a continuously rotating achromatic half-wave plate (HWP) for LiteBIRD. An achromatic HWP is made of five-layer sapphire plates following a Pancharatnam design. The two surfaces employ broadband anti-reflection (AR) sub-wavelength structures (SWS) fabricated with ultra-short pulsed laser ablation. For designing AHWP with SWS, we fabricated three representative structures using laser ablation. One has a symmetric SWS shape and the other two have different asymmetric shapes in ordinary and extraordinary directions. We modeled five-layer AHWP with SWS based on fabricated shapes and numerically evaluated their transmittance, modulation efficiency, and phase of the modulated signal using the rigorous coupled-wave analysis (RCWA) method. We also added instrumental polarization (IP) as the figure-of-merit, which is a conversion of unpolarized to polarized light. IP creates an undesired modulated signal, which may cause a non-linear response in a bolometric detector. The typical cause of IP is the imperfection of AR SWS. From calculations, we did not find a significant difference in IP among the three cases. However, we found the impact on the modulation efficiency because the retardance depends on the SWS shapes. Furthermore, the retardance depends on frequency. We numerically analyzed the impact of the extra retardance from SWS on the overall AHWP performance. We show one of the three cases has the broadest modulation efficiency by compensating for the frequency dependence of the retardance from the SWS and the AHWP sapphire stacks.
QUBIC (Q and U bolometric interferometer for cosmology) is an international ground-based experiment dedicated to the measurement of the polarized fluctuations of the cosmic microwave background (CMB). It is based on bolometric interferometry, an original detection technique which combines the immunity to systematic effects of an interferometer with the sensitivity of low temperature incoherent detectors. QUBIC will be deployed in Argentina, at the Alto Chorrillos mountain site near San Antonio de los Cobres, in the Salta province. The QUBIC detection chain consists of 2048 NbSi transition edge sensors (TESs) cooled to 320 mK. The voltage-biased TESs are read out with time domain multiplexing based on superconducting quantum interference devices (SQUIDs) at 1 K and a novel SiGe application-specific integrated circuit (ASIC) at 60 K allowing an unprecedented multiplexing (MUX) factor equal to 128 to be reached. The current QUBIC version is based on a reduced number of detectors (1/4) in order to validate the detection technique. The QUBIC experiment is currently being validated in the lab in Salta (Argentina) before going to the site for observations. This paper presents the main results of the characterization phase with a focus on the detectors and readout system.
The Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to shows the feasibility of the combination of interferometry and bolometric detection. The electronic readout system is based on an array of 128 NbSi Transition Edge Sensors cooled at 350mK readout with 128 SQUIDs at 1K controlled and amplified by an Application Specific Integrated Circuit at 40K. This readout design allows a 128:1 Time Domain Multiplexing. We report the design and the performance of the detection chain in this paper. The technological demonstrator unwent a campaign of test in the lab. Evaluation of the QUBIC bolometers and readout electronics includes the measurement of I-V curves, time constant and the Noise Equivalent Power. Currently the mean Noise Equivalent Power is ~ 2 x 10-16W= p √Hz
QUBIC (a Q and U Bolometric Interferometer for Cosmology) is a next generation cosmology experiment designed to detect the B-mode polarisation of the Cosmic Microwave Background (CMB). A B-mode detection is hard evidence of Inflation in the ΛCDM model. QUBIC aims to accomplish this by combining novel technologies to achieve the sensitivity required to detect the faint B-mode signal. QUBIC uses technologies such as a rotating half-wave plate, cryogenics, interferometric horns with self-calibration switches and transition edge sensor bolometers. A Technical Demonstrator (TD) is currently being calibrated in APC in Paris before observations in Argentina in 2021. As part of the calibration campaign, the spectral response of the TD is measured to test and validate QUBIC's spectro-imaging capability. This poster gives an overview of the methods used to measure the spectral response and a comparison of the instrument data with theoretical predictions and optical simulations.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.