Nouveaux concepts pour les matrices de bolomètres destinées à l'exploration de l'Univers dans le domaine millimétrique

Depuis sa découverte en 1964, l étude du Fond Diffus Cosmologique dans le domaine des longueurs d ondes millimétriques est devenue un enjeu majeur de la recherche expérimentale dans le domaine de la cosmologie. En particulier, ses anisotropies en température, mesurées pour la première fois par le satellite COBE puis plus finement par l expérience WMAP et le satellite PLANCK. L existence prédite d anisotropies de polarisation du Fond Diffus Cosmologique est fait actuellement parti du champ d expérimentation privilégié de l étude du CMB. En effet, la preuve d existence des modes B de polarisation, signature unique des ondes gravitationnelles primordiales, fait actuellement l objet d une recherche expérimentale intensive par le biais notamment de l instrument BICEP2 qui aurait détecté sa signature en 2014 dans des valeurs du rapport tenseur sur scalaire r = 0,2. Le projet QUBIC fait parti de ces expériences destinées à révéler les modes B de polarisation grâce à son instrument basé sur la technique des interféromètres et sur le développement de matrice de bolomètres, demandant un champ d investigation poussé englobant, entre autre, la physique des solides, la physique des basses températures et la cosmologie. La thèse présentée ici se situe dans ce cadre, avec pour objectif l élaboration d une matrice de bolomètres dont la performance et l optimisation devrait permettre d acquérir la sensibilité nécessaire à l observation des modes B de polarisation. Les différentes techniques expérimentales acquises au CSNSM d Orsay permettent en effet d envisager l optimisation des éléments clé de la matrice de bolomètre en s appuyant notamment sur l alliage amorphe de NbxSi1-x pour l élaboration d un senseur thermique optimisé, et sur un matériau novateur, l alliage de titane-vanadium, pour la mise au point d un absorbeur de rayonnement supraconducteur efficace, dont la faible chaleur spécifique doit permettre d atteindre un temps de réponse du détecteur de l ordre de la dizaine de milliseconde, valeur du temps de réponse nécessaire à une lecture efficace du signal du Fond Diffus Cosmologique. Le manuscrit de thèse ici présent a pour ambition de développer les principes physiques nécessaires au champ d investigation du travail à accomplir. Ainsi, cette étude propose d élaborer les différents éléments d un bolomètre, réunissant un senseur thermique optimisé ainsi qu un absorbeur de rayonnement de faible chaleur spécifique, permettant d envisager la mise au point d une matrice de bolomètres optimisée dans le cadre du projet QUBIC dont la campagne d observation est prévue courant 2015 au dôme C du pôle Sud.Since its discovery in 1964, the study of the Cosmic Microwave Background (CMB) in the field as of millimetre-length wavelengths became a major stake of experimental research in the field of cosmology. In particular, its anisotropies in temperature, measured for the first time by satellite COBE then more finely by the experiment WMAP and the PLANCK satellite. The predicted existence of anisotropies of polarization of the Cosmic Microwave Background is currently been part of the privileged field of experimentation of the study of the CMB. Indeed, the proof of exists modes B of polarization, single signature of the paramount gravitational waves, currently is the object of an intensive experimental research by the means in particular of the instrument BICEP2 which would have detected its signature in 2014 in values of the tensor report on scalar R = 0.2. Project QUBIC makes party of these experiments intended to reveal the modes B of polarization thanks to its instrument based on the technique of the interferometers and the development of bolometers array, asking for a thorough field of investigation including, amongst other things, the solid state physics, the physics of the low temperatures and cosmology. The thesis presented here is within this framework, with for objective making of a bolometers array whose performance and optimization should make it possible to acquire the necessary sensitivity to the observation of the B-mode polarization. The various experimental techniques acquired with the CSNSM of Orsay indeed make it possible to consider the optimization of the key elements of the bolometers array while being pressed in particular on amorphous alloy of NbxSi1-x for making of an optimized thermal sensor, and on an innovative material, titanium-vanadium alloy, for the clarification of an effective superconducting absorber of radiation, whose low specific heat must make it possible to reach a response time of the detector about ten millisecond, value of the response time necessary to an effective reading of the signal of the Cosmic Microwave Background. The manuscript of thesis here present has as an ambition to develop the physical principles necessary to the field of investigation of work to be achieved. Thus, this study proposes to work out the various elements of a bolometer, joining together a thermal sensor optimized as well as an absorber of radiation of low specific heat, making it possible to consider the clarification of a bolometers array optimized within the framework of the project QUBIC whose observation campaign is envisaged during 2015 with the dome C of the south pole.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

High-impedence NbSi TES sensors for studying the cosmic microwave background radiation

Precise measurements of the cosmic microwave background (CMB) are crucial in cosmology, because any proposed model of the universe must account for the features of this radiation. Of all CMB measurements that the scientific community has not yet been able to perform, the CMB B-mode polarization is probably the most challenging from the instrumental point of view. The signature of primordial gravitational waves, which give rise to a B-type polarization, is one of the goals in cosmology today and amongst the first objectives in the field. For this purpose, high-performance low-temperature bolometric cameras, made of thousands of pixels, are currently being developed by many groups, which will improve the sensitivity to B-mode CMB polarization by one or two orders of magnitude compared to the Planck satellite HFI detectors. We present here a new bolometer structure that is able to increase the pixel sensitivities and to simplify the fabrication procedure. This innovative device replaces delicate membrane-based structures and eliminates the mediation of phonons: the incoming energy is directly captured and measured in the electron bath of an appropriate sensor and the thermal decoupling is achieved via the intrinsic electron-phonon decoupling of the sensor at very low temperature. Reported results come from a 204-pixel array of Nb$_{x}$Si$_{1-x}$ transition edge sensors with a meander structure fabricated on a 2-inch silicon wafer using electron-beam co-evaporation and a cleanroom lithography process. To validate the application of this device to CMB measurements, we have performed an optical calibration of our sample in the focal plane of a dilution cryostat test bench. We have demonstrated a light absorption close to 20% and an NEP of about 7$\times10^{-16}$ W/$\sqrt{Hz}$, which is highly encouraging given the scope for improvement in this type of detectors.Comment: 6 pages, 10 figures. arXiv admin note: text overlap with arXiv:1005.0555 by other author

Tunable Superconducting Properties of a-NbSi Thin Films and Application to Detection in Astrophysics

We report on the superconducting properties of amorphous NbxSi1-x thin films. The normal-state resistance and critical temperatures can be separately adjusted to suit the desired application. Notably, the relatively low electron-phonon coupling of these films makes them good candidates for an "all electron bolometer" for Cosmological Microwave Background radiation detection. Moreover, this device can be made to suit both high and low impedance readouts

Characterization of the phonon sensor of the CRYOSEL detector with IR photons

The sensitivities of light Dark Matter (DM) particle searches with cryogenic detectors are mostly limited by large backgrounds of events that do not produce ionization signal. The CRYOSEL project develops a new technique where this background in a germanium cryogenic detector is rejected by using the signals from a Superconducting Single Electron Device (SSED) sensor designed to detect the phonons emitted through the Neganov-Trofimov-Luke effect by the e$^-$h$^+$ pairs as they drift in a close-by very high-field region. A tag on signals from this device should suppress the heat-only background. The measurement of the response to IR laser pulses of the first CRYOSEL prototype show the relevance of such sensor technology.Comment: 9 pages, 3 figures, LTD2

Detection chain and electronic readout of the QUBIC instrument

The Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to shows the feasibility of the combination of interferometry and bolometric detection. The electronic readout system is based on an array of 128 NbSi Transition Edge Sensors cooled at 350mK readout with 128 SQUIDs at 1K controlled and amplified by an Application Specific Integrated Circuit at 40K. This readout design allows a 128:1 Time Domain Multiplexing. We report the design and the performance of the detection chain in this paper. The technological demonstrator unwent a campaign of test in the lab. Evaluation of the QUBIC bolometers and readout electronics includes the measurement of I-V curves, time constant and the Noise Equivalent Power. Currently the mean Noise Equivalent Power is ~ 2 x 10⁻¹⁶ W/√Hz

Detection chain and electronic readout of the QUBIC instrument

The Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to shows the feasibility of the combination of interferometry and bolometric detection. The electronic readout system is based on an array of 128 NbSi Transition Edge Sensors cooled at 350mK readout with 128 SQUIDs at 1K controlled and amplified by an Application Specific Integrated Circuit at 40K. This readout design allows a 128:1 Time Domain Multiplexing. We report the design and the performance of the detection chain in this paper. The technological demonstrator unwent a campaign of test in the lab. Evaluation of the QUBIC bolometers and readout electronics includes the measurement of I-V curves, time constant and the Noise Equivalent Power. Currently the mean Noise Equivalent Power is ~ 2 x 10⁻¹⁶ W/√Hz

Prototyping a High Purity Germanium cryogenic veto system for a bolometric detection experiment

International audienceThe use of High Purity Germanium detectors operated in ionization mode at cryogenic temperatures is investigated as an external background mitigation solution for bolometers used in rare-event search experiments. A simple experimental setup with very partial coverage, running a 52-g $\mathrm{Li_2WO_4}$ bolometer sandwiched in-between two 2-cm thick High Purity Germanium cylindrical detectors in a dry cryostat, shows promising rejection to environmental gammas and atmospheric muons backgrounds. The acquired data are used together with a Monte Carlo simulation of the setup to extract the main contributions to the external backgrounds expected in an above ground experiment, such as e.g.~current and future experimental efforts targeting the detection of coherent elastic neutrino-nucleus scattering at reactor facilities. Based on all these results, a $\mathrm{4\pi}$ coverage similar veto system achieving a $\mathcal{O}$(10 keV) energy threshold is expected to achieve a $\mathrm{\gtrsim}$ 70 % and a $\mathrm{\gtrsim}$ 97 % rejection power for gamma-like and muon-like events, respectively

Optimization and experimental measurements of high impedance niobium-silicon (NbSi) transition edge sensors (TES) for high spectral and spatial resolution x-ray space-borne telescopes

International audiencepace-borne x-ray observations of supernova remnants, galactic clusters, x-ray binaries, and black holes are key elements in determining the structure of the universe. Astronomers require wide field of view with high spatial resolution but also very high spectral resolution to determine the physical conditions (temperatures, element abundances) with great accuracy. Today’s technologies (mostly TESs) obtain very high spectral resolutions to the detriment of power consumption, mostly due to their cold stage SQUID readout electronics. Their high power consumption limits the instrument’s field of view (FoV) by constraining the total number of pixels affordable at the 50 mK focal plane of a satellite cryostat. We use a new alloy technology: the high resistivity NbSi, enabling us to design TES sensors promising high spectral resolution and ultra low power consumption (below 10 pW). Their high impedance allows the use of a transistor readout at a hotter stage of the cryostat. This, in conjunction with the inherent ultra-low power dissipation of the sensors, raises drastically the number of pixels of the detector.In this article, we explore pixel optimization ways based on our electro-thermal model to reach spectral resolution of the order of 1.8 eV. We then use this model to manufacture a new batch of pixels on which we conduct experimental measurements. We measure the transient response, energy linearity and noise spectrum of our pixels with an Iron 55 source as well as an innovative on-chip pulse injection system. A low noise cryogenic amplifier as well as a cryogenic experimental setup have been designed to perform these measurements.© COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

High impedance TES with classical readout electronics: a new scheme toward large x-ray matrices

International audienceHigh impedance transition edge sensors (TES) are good candidates to constitute the sensitive part of new X-ray spectroimagers for the spatial X-ray observation, with even greater number of pixels. We test this solution in this context, developing an original scheme of readout that consist in implementing an active electro-thermal feedback, performed by a low noise cryogenic electronics, in order to solve the problematic effects of the electron-phonon decoupling, to ensure the stability of the system, and to increase the dynamic range of the detector. This paper presents the status of our developments, including the characterisation of the sensor, the experimental test of the active electro-thermal feedback, and our very first results of photon detection.© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only