Nondissipative Addressing for Time-Division SQUID Multiplexing

International audienceRecent and future astronomical instruments are based on a focal plane mapped by a large array of superconducting bolometers. Cryogenic analog multiplexing readout techniques, based on superconducting quantum interference devices (SQUIDs), are currently developed to achieve the readout of large arrays of this kind of low noise background-limited detectors. To effectively reduce the number of cryogenic wires (particularly, SQUID biasing), line/column addressing is currently used in time-division multiplexing, i.e., same biasing is applied to a few SQUIDs (on a line) of different columns. This technique should dramatically increase power consumption if parallel biasing is applied via resistors to isolate each column; the power budget is particularly limited on this kind of front-end cryogenic readout. A design with one transformer per SQUID is also used to read out SQUID biased in series with no excess of consumption and crosstalk. We propose here a new biasing technique using simple surface-mounted capacitors, which is easier to implement. These capacitors are used to parallel bias SQUIDs without additional Joule effect while minimizing crosstalk. However, capacitors do not allow dc biasing and need a current mean value equal to zero to avoid biasing source saturation. We have then tested square current biasing through capacitors on a commercial SQUID. This measurement shows that capacitors are able to proper bias SQUID and then to perform a nondissipative addressing for time-division SQUID multiplexing

The Gamma Cube: a new way to explore the gamma-ray sky

International audienceWe propose a new concept to allow the tracking of electrons in a gamma-ray telescope operating in the 5–100 MeV band. The idea of this experiment is to image the ionizing tracks that charged particles produce in a scintillator. It is a pair creation telescope at high energy and a Compton telescope with electron tracking at low energy. The telescope features a large scintillator transparent to the scintillation light, an ad-hoc optical system and a high resolution and highly sensitive imager. The performance perspectives and the advantages of such a system are outstanding but the technical difficulties are serious. A few years of research and development within the scientific community are required to reach the TRL level appropriate to propose the Gamma Cube in response to a flight opportunity

QUBIC: The QU Bolometric Interferometer for Cosmology

One of the major challenges of modern cosmology is the detection of B-mode polarization anisotropies in the CMB. 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. 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 interference fringes will be imaged on two focal planes (separated by a polarizing grid) tiled with bolometers. 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.Comment: 12 pages, 10 figures, submitted to Astronomy and Astrophysic

Large bolometer arrays with superconducting NbSi sensors for future space experiments

International audienceNew techniques in microelectronics allow to build large arrays of bolometers filling the focal plane of submillimeter and millimeter telescopes. The expected sensitivity increase is the key for the next generation of space experiments in this wavelength range. Superconducting bolometers offer currently the best prospects in terms of sensitivity and multiplexed readout. We present here the developments led in France based on NbSi alloy thermometers. The manufacturing process of a 23 pixel array and the test setup are described

QUBIC: the Q&U 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

Planck early results: first assessment of the High Frequency Instrument in-flight performance

The Planck High Frequency Instrument (HFI) is designed to measure the temperature and polarization anisotropies of the Cosmic Microwave Background and galactic foregrounds in six wide bands centered at 100, 143, 217, 353, 545 and 857 GHz at an angular resolution of 10' (100 GHz), 7' (143 GHz), and 5' (217 GHz and higher). HFI has been operating flawlessly since launch on 14 May 2009. The bolometers cooled to 100 mK as planned. The settings of the readout electronics, such as the bolometer bias current, that optimize HFI's noise performance on orbit are nearly the same as the ones chosen during ground testing. Observations of Mars, Jupiter, and Saturn verified both the optical system and the time response of the detection chains. The optical beams are close to predictions from physical optics modeling. The time response of the detection chains is close to pre-launch measurements. The detectors suffer from an unexpected high flux of cosmic rays related to low solar activity. Due to the redundancy of Planck's observations strategy, the removal of a few percent of data contaminated by glitches does not affect significantly the sensitivity. The cosmic rays heat up significantly the bolometer plate and the modulation on periods of days to months of the heat load creates a common drift of all bolometer signals which do not affect the scientific capabilities. Only the high energy cosmic rays showers induce inhomogeneous heating which is a probable source of low frequency noise.Comment: Submitted to A&A. 22 pages, 6 tables, 21 figures. One of a set of simultaneous papers for the Planck Missio

Planck pre-launch status : The Planck mission

Peer reviewe

The Large Imaging Spectrometer for Solar Accelerated Nuclei (LISSAN): A next-generation solar γ-ray spectroscopic imaging instrument concept

Models of particle acceleration in solar eruptive events suggest that roughly equal energy may go into accelerating electrons and ions. However, while previous solar X-ray spectroscopic imagers have transformed our understanding of electron acceleration, only one resolved image of γ-ray emission from solar accelerated ions has ever been produced. This paper outlines a new satellite instrument concept—the large imaging spectrometer for solar accelerated nuclei (LISSAN)—with the capability not only to observe hundreds of events over its lifetime, but also to capture multiple images per event, thereby imaging the dynamics of solar accelerated ions for the first time. LISSAN provides spectroscopic imaging at photon energies of 40 keV–100 MeV on timescales of ≲10 s with greater sensitivity and imaging capability than its predecessors. This is achieved by deploying high-resolution scintillator detectors and indirect Fourier imaging techniques. LISSAN is suitable for inclusion in a multi-instrument platform such as an ESA M-class mission or as a smaller standalone mission. Without the observations that LISSAN can provide, our understanding of solar particle acceleration, and hence the space weather events with which it is often associated, cannot be complete

Matthew Flinders et la mise en cartes d’un nouvel espace indo-pacifique

At the turn of the nineteenth century, the Royal Navy captain Matthew Flinders concluded a circumnavigation and hydrographical survey of Australia. He drew most of the charts of his voyage when, returning to England during the Napoleonic wars, he was detained for more than six years in Mauritius, which at that time was the French Isle de France. Against a background of commercial ambitions and maritime and colonial rivalries between European nations, governments and institutions increasingly relied on maps as one of their fundamental form of knowledge to shape their enterprise.The paper investigates how Flinders’s charts participated in the construction of a new maritime space that connected Australia to the Indian Ocean and the world maritime space. It reflects that the making up of Flinders’s maps was influenced by their spatial and local contexts. It highlights the network of institutions and individuals above and beyond Flinders’s maps that controlled or informed them

Le discours français de géographie régionale et l'Indochine coloniale : Les modèles des thèses de Charles Robequain et Pierre Gourou

Original PhD: February 2003Version française en document annexe: 2007This PhD investigates the discourse of two theses of the French School of Regional Geography, "le Thanh Hoá: étude géographique d' une province annamite", by Charles Robequain and "Les paysans du Delta tonkinois: étude de géographie humaine", by Pierre Gourou, published respectively in 1929 and 1936.The two works are analyzed as discourses (chapters 1 and 2) that are compared to other 1920's and 1930's discourses, and deconstructed through a contextual approach related to three major conditions: the context of the French school of geography, the colonial context and the Far Eastern context (Chapters 3 to 7)The thesis concludes on the way two geographers with similar backgrounds and working on the same field have constructed two distinct discourses representative of their French culture. In the meantime, these two discourses remain relevant in the construction of a French and Vietnamese knowledge that highlights the internal functioning of Vietnamese peasantry.Ce PhD revisite les premières thèses françaises de géographie régionale traitant de l'Extrême-Orient, "le Thanh Hoá, étude géographique d'une province annamite" de Charles Robequain, et "les paysans du Delta tonkinois, étude de géographie humaine" de Pierre Gourou, publiées la première en 1929 et la seconde en 1936.Ces deux œuvres sont analysées en tant que discours (chapitres 1 et 2) qui sont comparés aux autres discours de l'Entre-deux-guerres et déconstruits à travers une approche contextuelle répondant à trois conditions majeures: les contextes de l'École française de géographie, colonial, et extrême-oriental, analysés dans les chapitres 3 à 7.Le chapitre de conclusion met en lumière la manière dont deux géographes ayant reçu une formation universitaire similaire et travaillant sur le terrain colonial ont construit deux discours contrastés qui s'apparentent à leur culture française tout en participant parallèlement à la mise en place d'un savoir franco-vietnamien rendant compte des mécanismes de fonctionnement internes de la paysannerie vietnamienne