Dr. Cristian Franceschet Profile

Dr. Cristian Franceschet

Dr at Universita' degli Studi di Milano

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Publications (14)

PROCEEDINGS ARTICLE | August 9, 2018

Concept design of the LiteBIRD satellite for CMB B-mode polarization

Proc. SPIE. 10698, Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

KEYWORDS: Telescopes, Mirrors, Polarization, Satellites, Physics, Space telescopes, Frequency modulation, Fermium, Antennas, Cryogenics

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PROCEEDINGS ARTICLE | July 9, 2018

The STRIP instrument of the Large Scale Polarization Explorer: microwave eyes to map the Galactic polarized foregrounds

Proc. SPIE. 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

KEYWORDS: Telescopes, Mirrors, Polarization, Sensors, Calibration, Receivers, Polarizers, Polarimetry, Microwave radiation

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PROCEEDINGS ARTICLE | July 9, 2018

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

Proc. SPIE. 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

KEYWORDS: Detection and tracking algorithms, Interferometers, Particles, Tellurium

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PROCEEDINGS ARTICLE | July 9, 2018

QUBIC: the Q and U bolometric interferometer for cosmology

Proc. SPIE. 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

KEYWORDS: Optical filters, Mirrors, Fringe analysis, Switches, Polarization, Interferometers, Sensors, Calibration, Manufacturing, Anisotropy

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QUBIC, the Q & U Bolometric Interferometer for Cosmology, is a novel ground-based instrument that has been designed to measure the extremely faint B-mode polarisation anisotropy of the cosmic microwave background at intermediate angular scales (multipoles of 𝑙 = 30 − 200). Primordial B-modes are a key prediction of Inflation as they can only be produced by gravitational waves in the very early universe. To achieve this goal, QUBIC will use bolometric interferometry, a technique that combines the sensitivity of an imager with the systematic error control of an interferometer. It will directly observe the sky through an array of 400 back-to-back entry horns whose signals will be superimposed using a quasi-optical beam combiner. The resulting interference fringes will be imaged at 150 and 220 GHz on two focal planes, each tiled with NbSi Transition Edge Sensors, cooled to 320 mK and read out with time-domain multiplexing. A dichroic filter placed between the optical combiner and the focal planes will select the two frequency bands. A very large receiver cryostat will cool the optical and detector stages to 40 K, 4 K, 1 K and 320 mK using two pulse tube coolers, a novel 4He sorption cooler and a double-stage 3He/4He sorption cooler. Polarisation modulation and selection will be achieved using a cold stepped half-wave plate (HWP) and polariser, respectively, in front of the sky-facing horns. A key feature of QUBIC’s ability to control systematic effects is its ‘self-calibration’ mode where fringe patterns from individual equivalent baselines can be compared. When observing, however, all the horns will be open simultaneously and we will recover a synthetic image of the sky in the I, Q and U Stokes’ parameters. The synthesised beam pattern has a central peak of approximately 0.5 degrees in width, with secondary peaks further out that are damped by the 13-degree primary beam of the horns. This is Module 1 of QUBIC which will be installed in Argentina, near the city of San Antonio de los Cobres, at the Alto Chorrillos site (4869 m a.s.l.), Salta Province. Simulations have shown that this first module could constrain the tensor-to-scalar ratio down to σ(r) = 0.01 after a two-year survey. We aim to add further modules in the future to increase the angular sensitivity and resolution of the instrument. The QUBIC project is proceeding through a sequence of steps. After an initial successful characterisation of the detection chain, a technological demonstrator is being assembled to validate the full instrument design and to test it electrically, thermally and optically.

The technical demonstrator is a scaled-down version of Module 1 in terms of the number of detectors, input horns and pulse tubes and a reduction in the diameter of the combiner mirrors and filters, but is otherwise similar. The demonstrator will be upgraded to the full module in 2019. In this paper we give an overview of the QUBIC project and instrument.

PROCEEDINGS ARTICLE | July 9, 2018

Preliminary scanning strategy analysis for the LSPE-STRIP instrument

Proc. SPIE. 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

KEYWORDS: Observatories, Telescopes, Polarization, Calibration, Polarimetry, Clouds, Earth's atmosphere, Microwave radiation, Jupiter, Saturn

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PROCEEDINGS ARTICLE | July 9, 2018

Simulations and performance of the QUBIC optical beam combiner

Proc. SPIE. 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

KEYWORDS: Staring arrays, Bolometers, Zemax, Mirrors, Fringe analysis, Polarization, Imaging systems, Sensors, 3D modeling, Optical simulations

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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 of 𝑙 = 30 − 200). Primordial B-modes are a key prediction of Inflation as they can only be produced by gravitational waves in the very early universe. To achieve this goal, QUBIC will use bolometric interferometry, a technique that combines the sensitivity of an imager with the immunity to systematic effects of an interferometer. It will directly observe the sky through an array of back-to-back entry horns whose beams will be superimposed using a cooled quasioptical beam combiner. Images of the resulting interference fringes will be formed on two focal planes, each tiled with transition-edge sensors, cooled down to 320 mK. A dichroic filter placed between the optical combiner and the focal planes will select two frequency bands (centred at 150 GHz and 220 GHz), one frequency per focal plane. Polarization modulation will be achieved using a cold stepped half-wave plate (HWP) and polariser in front of the sky-facing horns.

The full QUBIC instrument is described elsewhere^1,2,3,4; in this paper we will concentrate in particular on simulations of the optical combiner (an off-axis Gregorian imager) and the feedhorn array. We model the optical performance of both the QUBIC full module and a scaled-down technological demonstrator which will be used to validate the full instrument design. Optical modelling is carried out using full vector physical optics with a combination of commercial and in-house software. In the high-frequency channel we must be careful to consider the higher-order modes that can be transmitted by the horn array. The instrument window function is used as a measure of performance and we investigate the effect of, for example, alignment and manufacturing tolerances, truncation by optical components and off-axis aberrations. We also report on laboratory tests carried on the QUBIC technological demonstrator in advance of deployment to the observing site in Argentina.

PROCEEDINGS ARTICLE | July 9, 2018

Thermal architecture for the QUBIC cryogenic receiver

Proc. SPIE. 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

KEYWORDS: Optical components, Switches, Polarization, Sensors, Copper, Receivers, Computer aided design, Signal detection, Cryogenics, Temperature metrology

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PROCEEDINGS ARTICLE | February 23, 2018

Optical modelling and analysis of the Q and U bolometric interferometer for cosmology

Proc. SPIE. 10531, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XI

KEYWORDS: Modeling, Point spread functions, Mirrors, Polarization, Interferometers, Calibration, Optical simulations, Tolerancing, Near field optics

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PROCEEDINGS ARTICLE | July 19, 2016

Optical design and modelling of the QUBIC instrument, a next-generation quasi-optical bolometric interferometer for cosmology

Proc. SPIE. 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII

KEYWORDS: Staring arrays, Bolometers, Modeling, Modeling, Point spread functions, Mirrors, Optical design, Polarization, Sensors, Off axis mirrors, Anisotropy

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PROCEEDINGS ARTICLE | September 24, 2012

The Large-Scale Polarization Explorer (LSPE)

Proc. SPIE. 8446, Ground-based and Airborne Instrumentation for Astronomy IV

KEYWORDS: Telescopes, Contamination, Polarization, Sensors, Calibration, Polarimetry, Synchrotrons, Spatial resolution, Jupiter, Galactic astronomy

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PROCEEDINGS ARTICLE | September 24, 2012

A coherent polarimeter array for the Large Scale Polarization Explorer (LSPE) balloon experiment

Proc. SPIE. 8446, Ground-based and Airborne Instrumentation for Astronomy IV

KEYWORDS: Staring arrays, Telescopes, Electronics, Polarization, Sensors, Calibration, Polarimetry, Spatial resolution, Microwave radiation, Cryogenics

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PROCEEDINGS ARTICLE | July 6, 2006

Calibration and testing of the Planck-LFI QM instrument

Proc. SPIE. 6265, Space Telescopes and Instrumentation I: Optical, Infrared, and Millimeter

KEYWORDS: Switches, Waveguides, Sensors, Calibration, Amplifiers, Receivers, Temperature sensors, Radiometry, Cryogenics, Temperature metrology

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PROCEEDINGS ARTICLE | July 6, 2006

Data analysis of the Planck/LFI ground-test campaign

Proc. SPIE. 6275, Millimeter and Submillimeter Detectors and Instrumentation for Astronomy III

KEYWORDS: Switches, Waveguides, Calibration, Receivers, Space telescopes, Software development, Radiometry, Microwave radiation, Anisotropy, Data analysis

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PROCEEDINGS ARTICLE | October 8, 2004

Analysis of the pseudocorrelation radiometers for the low frequency instrument onboard the Planck satellite

Proc. SPIE. 5498, Millimeter and Submillimeter Detectors for Astronomy II

KEYWORDS: Modeling, Data modeling, Waveguides, Satellites, Amplifiers, Finite element methods, Radiometry, Thermal modeling, Temperature metrology, Instrument modeling

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Showing 5 of 14 publications

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