QUBIC I: Overview and ScienceProgram

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We report on an extensive test campaign of a prototype version of the QUBIC (Q & U Bolometric Interferometer for Cosmology) instrument, carried out at Astroparticle Physics and Cosmology (APC) in Paris. Exploiting the novel concept called bolometric interferometry, QUBIC is designed to measure the CMB polarization at 150 and 220 GHz from a high altitude site at Alto Chorillo, Argentina. The prototype model called QUBIC Technological Demonstrator (QUBIC-TD) operates in a single frequency band (150 GHz) and with a reduced number of baselines, but it contains all the elements of the QUBIC instrument in its final configuration. The test campaign included measurements of the synthesized beam and of the polarization performance, as well as a verification of the interference fringe pattern. A modulated, frequency-tunable millimetre-wave source was placed in the telescope far-field and was used to simulate a point source. The QUBIC-TD field of view was scanned across the source to produce beam maps. Our measurements confirm the frequency-dependent behaviour of the beam profile, which gives QUBIC the possibility to do spectral imaging. The measured polarization performance indicates a cross-polarization leakage less than 0.6%. We also successfully tested the polarization modulation system, which is provided by a rotating half wave plate. We demonstrate the full mapmaking pipeline using data from this measurement campaign, effectively giving an end-to-end checkout of the entire QUBIC system, including all hardware subsystems, their interfaces, and the software to operate the whole system and run the analysis. Our results confirm the viability of bolometric interferometry for measurements of the CMB polarization.

Section: Bolometric Interferometrymentioning

confidence: 98%

QUBIC III: Laboratory characterization

Torchinsky

Hamilton

Piat

et al. 2022

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“…In the landscape of CMB polarization experiments, QUBIC is currently the only instrument based on this concept that combines the sensitivity of transition edge sensor (TES) bolometers with the advantages of interferometers. The combination gives features including self-calibration, in-band spectral resolution, which we call spectral imaging [3,4], and interferometric rather than photometric instrumental systematic effects. In this paper we describe the design, manufacturing and testing of the horn-switch array developed for the QUBIC technological demonstrator (TD), a prototype instrument that will demonstrate the application of bolometric interferometry to CMB polarization measurements with dedicated sky observations carried out from the QUBIC site.…”

Section: Introductionmentioning

confidence: 99%

QUBIC VII: The feedhorn-switch system of the technological demonstrator

Cavaliere

Mennella

Zannoni

et al. 2022

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We present the design, manufacturing and performance of the horn-switch system developed for the technological demonstrator of QUBIC (the Q&U Bolometric Interferometer for Cosmology). This system consists of 64 back-to-back dual-band (150 GHz and 220 GHz) corrugated feed-horns interposed with mechanical switches used to select desired baselines during the instrument self-calibration. We manufactured the horns in aluminum platelets milled by photo-chemical etching and mechanically tightened with screws. The switches are based on steel blades that open and close the waveguide between the back-to-back horns and are operated by miniaturized electromagnets. The measured electromagnetic performance of the feedhorns agrees with simulations. In particular we obtained a return loss around –20 dB up to 230 GHz and beam patterns in agreement with single-mode simulations down to –30 dB. The switches for this prototype were designed and built for the 150 GHz band. In this frequency range we find return and insertion losses consistent with expectations (< –25 dB and ∼ –0.1 dB, respectively) and an isolation larger than 70 dB. In this paper we also show the current development status of the feedhorn-switch system for the QUBIC full instrument, based on an array of 400 horn-switch assemblies.

“…[2][3][4][5] ). The Q & U Bolometric Interferometer for Cosmology (QUBIC) [6][7][8], is a bolometric interferometer, combining the high mapping speed of bolometer arrays with the beam purity and control of systematic effects of interferometers. A block-diagram of the instrument is shown in the top panel of figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…For this reason heat switches and high con- ductivity heat paths are very important parts of this cryogenic system. In this paper, which is part of a set describing the current status of the QUBIC experiment [8,19,[24][25][26][27][28] we describe the design, fabrication, experimental optimization and validation of the QUBIC cryogenic system in the Technological Demonstrator (TD) configuration. This configuration differs from the Full Instrument (FI) configuration because the optical apertures are reduced in size, only one of the two focal planes (the transmitted one) is installed, and only 1/4 of the detectors (one wafer) is present.…”

Section: Introductionmentioning

confidence: 99%

QUBIC V: Cryogenic system design and performance

Masi¹,

Battistelli²,

Bernardis³

et al. 2022

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Current experiments aimed at measuring the polarization of the Cosmic Microwave Background (CMB) use cryogenic detector arrays with cold optical systems to boost their mapping speed. For this reason, large volume cryogenic systems with large optical windows, working continuously for years, are needed. The cryogenic system of the QUBIC (Q & U Bolometric Interferometer for Cosmology) experiment solves a combination of simultaneous requirements: very large optical throughput (∼40 cm2sr), large volume (∼1 m3) and large mass (∼165 kg) of the cryogenic instrument. Here we describe its design, fabrication, experimental optimization and validation in the Technological Demonstrator configuration. The QUBIC cryogenic system is based on a large volume cryostat that uses two pulse-tube refrigerators to cool the instrument to ∼3 K. The instrument includes the cryogenic polarization modulator, the corrugated feedhorn array, and the lower temperature stages: a 4He evaporator cooling the interferometer beam combiner to ∼1 K and a 3He evaporator cooling the focal-plane detector arrays to ∼0.3 K. The cryogenic system has been tested and validated for more than 6 months of continuous operation. The detector arrays have reached a stable operating temperature of 0.33 K, while the polarization modulator has operated at a ∼10 K base temperature. The system has been tilted to cover the boresight elevation range 20°-90° without significant temperature variations. The instrument is now ready for deployment to the high Argentinean Andes.