Detection chain and electronic readout of the QUBIC instrument

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 10⁻¹⁶ W/√Hz

Detection chain and electronic readout of the QUBIC instrument

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 10⁻¹⁶ W/√Hz

Mechanical anti-reflection Structure for optical devices in the mm band

A major challenge in the implementation of optical element in the millimetre band is to minimize the radiation loss caused by reflection. The widely used method is based on the realization of an Anti-Reflection Coating (ARC), which exploits the behaviour of interference the radiation generated by the deposition of one or more layers of polymeric material on the optical element, so as to obtain a unique surface having refractive index conveniently selected. The major limitations that affect the ARC, reside in the complexity of manufacturing, with consequent increase of costs, and possible bonding process issues after several cooling cycles; an essential feature to achieve measurements at these wavelengths. Here we report about an alternative and innovative technique based on the realization of a mechanical Anti-Reflection Structures (ARS), possibly a more simple and economic manufacture, based on the mechanical processing of the surface of a dielectric material. The antireflective behaviour is linked to the geometrical textureof the surface. The simulations of these ARS provide us a detailed analysis of the optical properties for dierent geometrical realizations. The results will be compared with those of the ARC and further experimentally validated. Particular attention is put on to the analysis of the possible presence of spurious polarization effects, because this type of technology could find employment in the realization of cold optical elements for telescopes devoted CMB observations

Pratiche didattiche tra centro e periferia nel Mediterraneo tardoantico

Un consistente numero di relatori italiani e stranieri è stato coinvolto in una vasta ricerca sulla diffusione dell'alfabetizzazione e della cultura nell'area del mediterraneo tardoantico (III-VI secolo)

Development of Kinetic Inductance Detectors for KIS

Millimetre-wave astronomical observations have an enormous discovery potential for the study of the earliest stages of the evolution of the universe, clusters of galaxies, high-redshift objects, and star formation regions. One of the challenges today is to perform observations with the finest an- gular resolution, in order to accurately investigate the nature of these astrophysical sources. While for spectroscopic investigations of point-like sources ALMA is the obvious solution, for contin- uum measurements of diffuse sources large single-dish telescopes (e.g. GBT, TML, IRAM, SRT, etc.) equipped with large-format bolometeric cameras provide a much higher mapping speed. Kinetic Inductance Detectors represent an interesting option for the detector array, due to their easiness to multiplex and their capability to efficiently tackle with atmospheric issues. We are de- veloping Aluminum Lumped Element KIDs for the 3 mm atmospheric window (W-band). While interesting performance of KIDs has already been demonstrated for the 1 and 2 mm windows, further technological development is needed for their use at longer wavelengths. In this contribu- tion we will describe a recent proposal for a new KID imager to be installed at the Sardinia Radio Telescope, the largest Italian radio astronomy facility. We will discuss detector requirements and we will show the results of optical tests of the first device

QUBIC-the Q & U bolometric interferometer for cosmology

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

Thermal architecture for the QUBIC cryogenic receiver

QUBIC, the QU Bolometric Interferometer for Cosmology, is a novel forthcoming instrument to measure the B-mode polarization anisotropy of the Cosmic Microwave Background. The detection of the B-mode signal will be extremely challenging; QUBIC has been designed to address this with a novel approach, namely bolometric interferometry. The receiver cryostat is exceptionally large and cools complex optical and detector stages to 40 K, 4 K, 1 K and 350 mK using two pulse tube coolers, a novel 4He sorption cooler and a double-stage 3He/4He sorption cooler. We discuss the thermal and mechanical design of the cryostat, modelling and thermal analysis, and laboratory cryogenic testing

Performance of NbSi transition-edge sensors readout with a 128 MUX factor for the QUBIC experiment

QUBIC (the Q and U Bolometric Interferometer for Cosmology) is a ground-based experiment which seeks to improve the current constraints on the amplitude of primordial gravitational waves. It exploits the unique technique, among Cosmic Microwave Background experiments, of bolometric interferometry, combining together the sensitivity of bolometric detectors with the control of systematic effects typical of interferometers. QUBIC will perform sky observations in polarization, in two frequency bands centered at 150 and 220 GHz, with two kilo-pixel focal plane arrays of NbSi Transition-Edge Sensors (TES) cooled down to 350 mK. A subset of the QUBIC instrument, the so called QUBIC Technological Demonstrator (TD), with a reduced number of detectors with respect to the full instrument, will be deployed and commissioned before the end of 2018. The voltage-biased TES are read out with Time Domain Multiplexing and an unprecedented multiplexing (MUX) factor equal to 128. This MUX factor is reached with two-stage multiplexing: a traditional one exploiting Superconducting QUantum Interference Devices (SQUIDs) at 1K and a novel SiGe Application-Specific Integrated Circuit (ASIC) at 60 K. The former provides a MUX factor of 32, while the latter provides a further 4. Each TES array is composed of 256 detectors and read out with four modules of 32 SQUIDs and two ASICs. A custom software synchronizes and manages the readout and detector operation, while the TES are sampled at 780 Hz (100kHz/128 MUX rate). In this work we present the experimental characterization of the QUBIC TES arrays and their multiplexing readout chain, including time constant, critical temperature, and noise properties

Simulations and performance of the QUBIC optical beam combiner

QUBIC, the Q & U Bolometric Interferometer for Cosmology, is a novel ground-based instrument that aims to measure the extremely faint B-mode polarisation anisotropy of the cosmic microwave background at intermediate angular scales (multipoles o