57 research outputs found
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
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
Cryogenic operation of a SiGe integrated circuit for control time domain SQUID multiplexing
This paper presents an ultra low noise instrumentation based on cryogenic electronic integrated circuit. We have designed an ASIC (Application Specific Integrated Circuit) in standard BiCMOS SiGe 0.35 μm AMS technology. The main functions of this circuit, the readout and the control of a 24 to 1 SQUID multiplexer, is presented. We also report the cryogenic operation of each part of this ASIC
SiGe Heterojunction Bipolar Transistor Operated At Liquid Helium Temperature
International audienc
The BRAIN project: looking for B-mode from Dome-C
Texte integral disponible sur http://proc.sf2a.asso.fr/sf2a06.phpInternational audienceThe detection and characterisation of Cosmic Microwave Background B-mode polarization is one of the next challenges in observational cosmology. This primordial polarization mode is only due to tensor perturbations of the metric produced by primordial gravitational waves, which could have been generated during the inflation epoch. With a signal of less than 0.1? K, B-mode measurement requires very sensitive experiments and also an extremely good control of instrumental effects. In this paper we present the BRAIN experiment, a bolometric interferometer devoted to B-mode detection. This new detection architecture allows to directly measure the Fourier modes of the Stokes parameters. High sensitivity is obtained by using low temperature bolometers while systematic effects are reduced by using the interferometric technique
Cryogenic Integrated Offset Compensation for Time Domaine SQUID Multiplexing
International audienceSuperconducting QUantum Interference Device (SQUID) multiplexing is an important issue in the use of large arrays of superconducting bolometers (TES). A Time Domain Multiplexer (TDM) combines input TES signals into one output signal using several SQUIDs. Different TESs, SQUIDs and amplifiers characteristics induce unavoidable different offsets on the multiplexed signal. Moreover, assuming the periodicity of the SQUID characteristic, the Flux Locked Loop (FLL) operating point is defined at modulo Phi_0 which could also leads to a large output offset. In multiplexed mode, offsets resulting from different pixels induce a parasitic signals often larger than the TES one. This offset signal drastically constrains the readout dynamic range and thus the maximum gain allowed. It also limits the signal-to-noise ratio, the FLL stability and the multiplexing frequency. Offset in SQUID readout is discussed and offset compensation for TDM is presented. Simulation shows the dynamic calibration and compensation on a simplified 4:1 TDM. Dynamic offset compensation is being implemented on a cryogenic BiCMOS SiGe integrated circuit operated at 4K for 128:1 TDM
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