QUBIC: The QU bolometric interferometer for cosmology

Abstract

One of the major challenges of modern cosmology is the detection of B-mode polarization anisotropies in the Cosmic Microwave Background. These originate from tensor fluctuations of the metric produced during the inflationary phase. Their detection would therefore constitute a major step towards understanding the primordial Universe. The expected level of these anisotropies is however so small that it requires a new generation of instruments with high sensitivity and extremely good control of systematic effects. We propose the QUBIC instrument based on the novel concept of bolometric interferometry, bringing together the sensitivity advantages of bolometric detectors with the systematics effects advantages of interferometry. The instrument will directly observe the sky through an array of entry horns whose signals will be combined together using an optical combiner. The whole set-up is located inside a cryostat. Polarization modulation will be achieved using a rotating half-wave plate and the images of the interference fringes will be formed on two focal planes (separated by a polarizing grid) tiled with bolometers. We show that QUBIC can be considered as a synthetic imager, exactly similar to a usual imager but with a synthesized beam formed by the array of entry horns. Scanning the sky provides an additional modulation of the signal and improve the sky coverage shape. The usual techniques of map-making and power spectrum estimation can then be applied. We show that the sensitivity of such an instrument is comparable with that of an imager with the same number of horns. We anticipate a low level of beam-related systematics thanks to the fact that the synthesized beam is determined by the location of the primary horns. Other systematics should be under good control thanks to an autocalibration technique, specific to our concept, that will permit the accurate determination of most of the instrumental parameters that would otherwise lead to systematics. (C) 2011 Elsevier B.V. All rights reserved

Intensity and polarization of the atmospheric emission at millimetric wavelengths at Dome Concordia

“…This parameter has to be taken into account when considering measurements with thermal detectors, such as transition edge sensor (TES) bolometers (like those planned for the QUBIC experiment), and when accounting for load variation on the bolometers themselves, and TES plus superconducting quantum interference devices (SQUIDs) working point tuning. We estimate a relative average variation, on a daily basis, of 0.9 per cent, consistent with one single tuning procedure per day needed (Battistelli et al 2011). Peaks of a few per cent have also been observed in limited cases.…”

Design, Fabrication, and Testing of a TiN/Ti/TiN Trilayer KID Array for 3 mm CMB Observations

“…We are specifically motivated by the design constraints for the QUBIC telescope [6], however, we have made an effort to keep the design as simple and as broadly applicable as possible.…”

QUBIC: Using NbSi TESs with a Bolometric Interferometer to Characterize the Polarization of the CMB

“…near San Antonio de los Cobres, in the Salta province. A full description of the QUBIC instrument is given in these proceedings [3] and in [4,5,6,7,8,9]. A schematic of QUBIC is shown in Fig.…”