QUBIC: The QU Bolometric Interferometer for Cosmology
Battistelli, E. and Bau, A. and Bennett, D. and Berge, L. and Bernard, J.-Ph. and de Bernardis, P. and Bounab, A. and Breelle, E. and Bunn, E.F. and Calvo, M. and Charlassier, R. and Collin, S. and Cruciani, A. and Curran, D. and Dumoulin, L. and Gault, A. and Gervasi, M. and Ghribi, A. and Giard, M. and Giordano, C. and Giraud-Héraud, Y. and Gradziel, M. and Guglielmi, L. and Hamilton, J.-Ch. and Haynes, V. and Kaplan, J. and Korotkov, A. and Lande, J. and Maffei, B. and Maiello, M. and Malu, S. and Marnieros, S. and Masi, S. and Murphy, A. and Nati, F. and O'Sullivan, C. and Pajot, F. and Passerini, A. and Peterzen, S. and Piacentini, F. and Piat, M. and Piccirillo, L. and Pisano, G. and Polenta, G. and Prele, D. and Romano, D. and Rosset, C. and Salatino, M. and Schillaci, A. and Sironi, G. and Sordini, R. and Spinelli, S. and Tartari, A. and Timbie, P. and Tucker, G. and Vibert, L. and Voisin, F. and Watson, R.A. and Zannoni, M. (2011) QUBIC: The QU Bolometric Interferometer for Cosmology. Astroparticle Physics, 34 (9). pp. 705-716. ISSN 0927-6505
Context. One of the major challenges of modern cosmology is the detection of B-mode polarization anisotropies in the Cosmic Microwave Background. These originate from tensor fluctuations of the metric produced during the inflationary phase. Their detection would therefore constitute a major step towards understanding the primordial Universe. The expected level of these anisotropies is however so small that it requires a new generation of instruments with high sensitivity and extremely good control of systematic eects. Aims. We propose the QUBIC instrument based on the novel concept of bolometric interferometry, bringing together the sensitivity advantages of bolometric detectors with the systematics eects advantages of interferometry. Methods. The instrument will directly observe the sky through an array of entry horns whose signals will be combined together using an optical combiner. The whole set-up is located inside a cryostat. Polarization modulation will be achieved using a rotating half-wave plate and the images of the interference fringes will be formed on two focal planes (separated by a polarizing grid) tiled with bolometers. Results.We show that QUBIC can be considered as a synthetic imager, exactly similar to a usual imager but with a synthesized beam formed by the array of entry horns. Scanning the sky provides an additional modulation of the signal and improve the sky coverage shape. The usual techniques of map-making and power spectrum estimation can then be applied. We show that the sensitivity of such an instrument is comparable with that of an imager with the same number of horns. We anticipate a low level of beam-related systematics thanks to the fact that the synthesized beam is determined by the location of the primary horns. Other systematics should be under good control thanks to an autocalibration technique, specific to our concept, that will permit the accurate determination of most of the systematics parameters.
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