M. Zannoni

QUBIC: The QU Bolometric Interferometer For Cosmology

The primordial B-mode polarisation of the Cosmic Microwave Background is the imprints of the gravitational wave background generated by inflation. Observing the B-mode is up to now the most direct way to constrain the physics of the primordial Universe, especially inflation. To detect these B-modes, high sensitivity is required as well as an exquisite control of systematics effects. To comply with these requirements, we propose a new instrument called QUBIC (Q and U Bolometric Interferometer for Cosmology) based on bolometric interferometry. The control of systematics is obtained with a close-packed interferometer while bolometers cooled to very low temperature allow for high sensitivity. We present the architecture of this new instrument, the status of the project and the self-calibration technique which allows accurate measurement of the instrumental systematic effects.

The Large-Scale Polarization Explorer (LSPE)

The LSPE is a balloon-borne mission aimed at measuring the polarization of the Cosmic Microwave Background (CMB) at large angular scales, and in particular to constrain the curl component of CMB polarization (B-modes) produced by tensor perturbations generated during cosmic inflation, in the very early universe. Its primary target is to improve the limit on the ratio of tensor to scalar perturbations amplitudes down to r = 0.03, at 99.7% confidence. A second target is to produce wide maps of foreground polarization generated in our Galaxy by synchrotron emission and interstellar dust emission. These will be important to map Galactic magnetic fields and to study the properties of ionized gas and of diffuse interstellar dust in our Galaxy. The mission is optimized for large angular scales, with coarse angular resolution (around 1.5 degrees FWHM), and wide sky coverage (25% of the sky). The payload will fly in a circumpolar long duration balloon mission during the polar night. Using the Earth as a giant solar shield, the instrument will spin in azimuth, observing a large fraction of the northern sky. The payload will host two instruments. An array of coherent polarimeters using cryogenic HEMT amplifiers will survey the sky at 43 and 90 GHz. An array of bolometric polarimeters, using large throughput multi-mode bolometers and rotating Half Wave Plates (HWP), will survey the same sky region in three bands at 95, 145 and 245 GHz. The wide frequency coverage will allow optimal control of the polarized foregrounds, with comparable angular resolution at all frequencies.

The Sky Polarization Observatory

Abstract The Sky Polarization Observatory (SPOrt) is an ASI-funded experiment specifically designed to measure the sky polarization at 22, 32 and 90 GHz, which was selected in 1997 by ESA to be flown on the International Space Station. Starting in 2006 and for at least 18 months, it will be taking direct and simultaneous measurements of the Stokes parameters Q and U at 660 sky pixels, with FWHM=7°. Due to development efforts over the past few years, the design specifications have been significantly improved with respect to the first proposal. Here we present an up-to-date description of the instrument, which now warrants a pixel sensitivity of 1.7 μK for the polarization of the cosmic background radiation, assuming two years of observations. We discuss SPOrt scientific goals in the light of WMAP results, in particular in connection with the emerging double-reionization cosmological scenario.

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

We discuss the design and expected performance of STRIP (STRatospheric Italian Polarimeter), an array of coherent receivers designed to fly on board the LSPE (Large Scale Polarization Explorer) balloon experiment. The STRIP focal plane array comprises 49 elements in Q band and 7 elements in W-band using cryogenic HEMT low noise amplifiers and high performance waveguide components. In operation, the array will be cooled to 20 K and placed in the focal plane of a ~0.6 meter telescope providing an angular resolution of ~1.5 degrees. The LSPE experiment aims at large scale, high sensitivity measurements of CMB polarization, with multi-frequency deep measurements to optimize component separation. The STRIP Q-band channel is crucial to accurately measure and remove the synchrotron polarized component, while the W-band channel, together with a bolometric channel at the same frequency, provides a crucial cross-check for systematic effects.

SAGACE : The spectroscopic active galaxies and clusters explorer

The SAGACE experiment consists of a mm/sub-mm telescope with a 3-m diameter primary mirror, coupled to a cryogenic multi-beam differential spectrometer. SAGACE explores the sky in the 100-760 GHz frequency range, using four diffraction-limited bolometer arrays. The instrument is designed to perform spectroscopic surveys of the Sunyaev- Zeldovich effects of thousands of galaxy clusters, of the spectral energy distribution of active galactic nuclei, and of the [CII] line of a thousand galaxies in the redshift desert. In 2008 a full phase-A study for a national small mission was completed and delivered to the Italian Space Agency (ASI). We have shown that taking advantage of the differential operation of the Fourier Transform Spectrometer, this ambitious instrument can operate from a Molniya orbit, and can be built and operated within the tight budget of a small mission. Copyright

Latest Progress on the QUBIC Instrument

QUBIC is a unique instrument that crosses the barriers between classical imaging architectures and interferometry taking advantage from both high sensitivity and systematics mitigation. The scientific target is to detect primordial gravitational waves created by inflation by the polarization they imprint on the cosmic microwave background—the holy grail of modern cosmology. In this paper, we show the latest advances in the development of the architecture and the sub-systems of the first module of this instrument to be deployed at Dome Charlie Concordia base—Antarctica in 2015.

A template of atmospheric O2 circularly polarized emission for cosmic microwave background experiments

We compute the circularly polarized signal from atmospheric molecular oxygen. The polarization of O 2 rotational lines is caused by the Zeeman effect in the Earths magnetic field. We evaluate the circularly polarized emission for various sites suitable for cosmic microwave background (CMB) measurements: the South Pole and Dome C (Antarctica), Atacama (Chile) and Testa Grigia (Italy). We present and discuss an analysis of the polarized signal within the framework of future CMB polarization experiments. We find a typical circularly polarized signal (V Stokes parameter) of ∼50―300 μK at 90 GHz looking at the zenith. Among the sites, Atacama shows a lower polarized signal at the zenith. We present maps of this signal for the various sites and we show typical elevation and azimuth scans. We find that Dome C presents the lowest gradient in polarized temperature: ~0.3 μK deg ―1 at 90 GHz. We also study the frequency bands of observation: around ν ≃ 100 GHz and ν ≃ 160 GHz, we find the best conditions because the polarized signal vanishes. Finally, we evaluate the accuracy of the templates and the signal variability in relation to our knowledge of and the variability of the Earths magnetic field and atmospheric parameters.

Efficient differential Fourier-transform spectrometer for precision Sunyaev-Zel’dovich effect measurements

Context. Precision measurements of the Sunyaev-Zel’dovich e↵ect in clusters of galaxies require excellent rejection of common-mode signals and wide frequency coverage. Aims. We describe an imaging, ecient, di↵erential Fourier transform spectrometer (FTS), optimized for measurements of faint brightness gradients at millimeter wavelengths. Methods. Our instrument is based on a Martin-Puplett interferometer (MPI) configuration. We combined two MPIs working synchronously to use the whole input power. In our implementation the observed sky field is divided into two halves along the meridian, and each half-field corresponds to one of the two input ports of the MPI. In this way, each detector in the FTS focal planes measures the di↵erence in brightness between two sky pixels, symmetrically located with respect to the meridian. Exploiting the high commonmode rejection of the MPI, we can measure low sky brightness gradients over a high isotropic background. Results. The instrument works in the range ⇠120 cm 1 (30600 GHz), has a maximum spectral resolution 1/(2 OPD) = 0.063 cm 1 (1.9 GHz), and an unvignetted throughput of 2.3 cm 2 sr. It occupies a volume of 0.7 ⇥ 0.7 ⇥ 0.33 m 3 and has a weight of 70 kg. This design can be implemented as a cryogenic unit to be used in space, as well as a room-temperature unit working at the focus of suborbital and ground-based mm-wave telescopes. The first in-flight test of the instrument is with the OLIMPO experiment on a stratospheric balloon; a larger implementation is being prepared for the Sardinia radio telescope.

A template of atmospheric

We compute the circularly polarized signal from atmospheric molecular oxygen. The polarization of O 2 rotational lines is caused by the Zeeman effect in the Earths magnetic field. We evaluate the circularly polarized emission for various sites suitable for cosmic microwave background (CMB) measurements: the South Pole and Dome C (Antarctica), Atacama (Chile) and Testa Grigia (Italy). We present and discuss an analysis of the polarized signal within the framework of future CMB polarization experiments. We find a typical circularly polarized signal (V Stokes parameter) of ∼50―300 μK at 90 GHz looking at the zenith. Among the sites, Atacama shows a lower polarized signal at the zenith. We present maps of this signal for the various sites and we show typical elevation and azimuth scans. We find that Dome C presents the lowest gradient in polarized temperature: ~0.3 μK deg ―1 at 90 GHz. We also study the frequency bands of observation: around ν ≃ 100 GHz and ν ≃ 160 GHz, we find the best conditions because the polarized signal vanishes. Finally, we evaluate the accuracy of the templates and the signal variability in relation to our knowledge of and the variability of the Earths magnetic field and atmospheric parameters.

O_2

SPOrt is a space experimental aimed at studying the polarization of the CMB and of the diffused Galactic Background in the microwave range (22-90 GHz). Here we present the project as well as its main scientific goals.