QUBIC: Using NbSi TESs with a Bolometric Interferometer to Characterize the Polarization of the CMB
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QUBIC: Using NbSi TESs with a Bolometric Interferometer to Characterize the Polarization of the CMB M. Piat, et al. [full author details at the end of the article] Received: 31 July 2019 / Accepted: 13 March 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Q & U Bolometric Interferometer for Cosmology (QUBIC) is an international ground-based experiment dedicated in the measurement of the polarized fluctuations of the Cosmic Microwave Background. 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 in 2048 NbSi transition edge sensors (TESs) cooled to 350 mK.The voltage-biased TESs are read out with time domain multiplexing based on Superconducting QUantum Interference Devices at 1 K and a novel SiGe application-specific integrated circuit at 60 K allowing to reach an unprecedented multiplexing factor equal to 128. The QUBIC experiment is currently being characterized in the laboratory with a reduced number of detectors before upgrading to the full instrument. I will present the last results of this characterization phase with a focus on the detectors and readout system. Keywords TESs · TDM · CMB
1 Introduction The measurement of the curl component of the polarization of the Cosmic Microwave Background (CMB), the so-called B-modes, is one of the most difficult challenge of the observational cosmology. Its detection would provide valuable information about the primordial universe, inflation theory as well as quantum gravity. Currently observing or planned CMB experiments share the same detection strategy: they are imagers able to perform high sensitivity observations of the sky thanks to background-limited broadband detectors but are all subject to similar instrumental systematic effects. In interferometers what is formed on the focal plane are the Fourier modes of the sky radiation produced by an array of spatially correlated antennas. Generally, such instrumental configurations suffer low sensitivity and the impossibility of exploiting background-limited broadband direct detectors. The great
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Journal of Low Temperature Physics
Fig. 1 Left: Schematic of the QUBIC instrument. The window aperture is about 40 cm; the cryostat is about 1.41 m in diameter and 1.51 m in height; Right: 3D rendering of the inner part of the cryostat. TES, transition edge sensor (Color figure online)
advantage of interferometric instruments resides in their capability of controlling systematic effects. Measurements of the scalar component of the CMB polarization, the E-modes, have been performed in the past with such instrumental configuration (CBI [1], DASI [2]). In this context, the Q and U Bolometric Interferometer for Cosmology (QUBIC) currently presents a un
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