An efficient phase-shifting scheme for bolometric  additive interferometry

Charlassier, R.; Hamilton, J. C.; Bréelle, É.; Ghribi, A.; Giraud‐Héraud, Y.; Kaplan, J.; Piat, M.; Prêle, D.

doi:10.1051/0004-6361/200810306

Cited by 17 publications

(27 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In this perspective, redundancy turns out to be the crucial property to fulfill these two objectives, as shown in Charlassier et al (2009) and in the present article.…”

Section: Resultsmentioning

confidence: 53%

Self-calibration: an efficient method to control systematic effects in bolometric interferometry

Bigot-Sazy

Charlassier²,

Hamilton

et al. 2013

A&A

Self Cite

View full text Add to dashboard Cite

Context. The QUBIC collaboration is building a bolometric interferometer dedicated to the detection of B-mode polarization fluctuations in the cosmic microwave background. Aims. We introduce a self-calibration procedure related to those used in radio-interferometry to control a wide range of instrumental systematic errors in polarization-sensitive instruments.Methods. This procedure takes advantage of the need for measurements on redundant baselines to match each other exactly in the absence of systematic effects. For a given systematic error model, measuring each baseline independently therefore allows writing a system of nonlinear equations whose unknowns are the systematic error model parameters (gains and couplings of Jones matrices, for instance). Results. We give the mathematical basis of the self-calibration. We implement this method numerically in the context of bolometric interferometry. We show that, for large enough arrays of horns, the nonlinear system can be solved numerically using a standard nonlinear least-squares fitting and that the accuracy achievable on systematic effects is only limited by the time spent on the calibration mode for each baseline apart from the validity of the systematic error model.

show abstract

“…In this perspective, redundancy turns out to be the crucial property to fulfill these two objectives, as shown in Charlassier et al (2009) and in the present article.…”

Section: Resultsmentioning

confidence: 53%

Self-calibration: an efficient method to control systematic effects in bolometric interferometry

Bigot-Sazy

Charlassier²,

Hamilton

et al. 2013

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…The coefficients of the linear combination of visibilities arriving at each bolometer are just related to the phase-differences between different channels imposed by the optical combiner. This was explored in detail in (Charlassier et al, 2009) where we have shown that the visibility reconstruction can be done in an optimal way. Working with the visibilities, although it may seem logical as we are dealing with an interferometer, may not be the best approach however.…”

Section: Synthetic Imagementioning

confidence: 99%

“…4) defined by each possible pair of horns. Such a redundancy was shown to be crucial to ensure an optimal sensitivity of the bolometric interferometer (Charlassier et al, 2009) allowing for what we have called a "coherent summation of equivalent baselines". This means that all equivalent (or redundant) baselines need to experience the same phase difference configuration on the focal plane in order to maximize the signal to noise ratio of the visibilities, or of the synthetic images.…”

Section: Synthesized Beammentioning

confidence: 99%

See 1 more Smart Citation

QUBIC: the Q&U Bolometric Interferometer for Cosmology

et al. 2012

Self Cite

View full text Add to dashboard Cite

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 effects. 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 effects 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.

show abstract

“…In (Charlassier et al 2009), hereafter (C09), we introduced a simple formalism for the general design of a bolometric interferometer operating at a monochromatic frequency and showed that its phase shifting scheme must respect a property which we called "coherent summation of equivalent baselines". This scheme was optimized further in (Hyland et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Bandwidth in bolometric interferometry

Charlassier¹,

Bunn

Hamilton³

et al. 2010

A&A

Self Cite

View full text Add to dashboard Cite

Context. Bolometric interferometry is a promising new technology with potential applications to the detection of B-mode polarization fluctuations of the cosmic microwave background (CMB). A bolometric interferometer will have to take advantage of the wide spectral detection band of its bolometers to be competitive with imaging experiments. A crucial concern is that interferometers are assumed to be significantly affected by a spoiling effect known as bandwidth smearing. Aims. We investigate how the bandwidth modifies the work principle of a bolometric interferometer and affects its sensitivity to the CMB angular power spectra. Methods. We obtain analytical expressions for the broadband visibilities measured by broadband heterodyne and bolometric interferometers. We investigate how the visibilities must be reconstructed in a broadband bolometric interferometer and show that this critically depends on hardware properties of the modulation phase shifters. If the phase shifters produce shifts that are constant with respect to frequency, the instrument works like its monochromatic version (the modulation matrix is not modified), while if they vary (linearly or otherwise) with respect to frequency, one has to perform a special reconstruction scheme, which allows the visibilities to be reconstructed in frequency subbands. Using an angular power spectrum estimator that accounts for the bandwidth, we finally calculate the sensitivity of a broadband bolometric interferometer. A numerical simulation is performed that confirms the analytical results. Results. We conclude that (i) broadband bolometric interferometers allow broadband visibilities to be reconstructed regardless of the type of phase shifters used and (ii) for dedicated B-mode bolometric interferometers, the sensitivity loss caused by bandwidth smearing is quite acceptable, even for wideband instruments (a factor of 2 loss for a typical 20% bandwidth experiment).

show abstract

An efficient phase-shifting scheme for bolometric additive interferometry

Cited by 17 publications

References 25 publications

Self-calibration: an efficient method to control systematic effects in bolometric interferometry

Self-calibration: an efficient method to control systematic effects in bolometric interferometry

QUBIC: the Q&U Bolometric Interferometer for Cosmology

Bandwidth in bolometric interferometry

Contact Info

Product

Resources

About