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International audience; The alternative fuels developed recently for environmental or future economical reasons must comply with international specifications designed historically for kerosene blends. Although some specifications are not technically proven, they must be respected by the new fuel. This means that presently they must be mixed with Jet A-1 to be used. ONERA has started an inhouse program to understand the influence of the fuel composition on the fuel behaviour and thus to widen the possible spectrum of alternative fuels. The present work describes experimental results describing ignition performances of six compositions of fuels, according to aromatics concentration, under altitude conditions, i.e. low air pressure and temperature.

International audience; The paper presents numerical models and simulations performed at ONERA to investigate aerodynamic effects on the trajectory of an open rotor blade fragment released or lost during an engine burst event. The models are based on finite elements for the structural part and on finite volumes for the fluid part, and are implemented in the EUROPLEXUS explicit code. Fluid–structure interaction is taken into account by an embedded (or immersed) technique and precision is enhanced by refining the fluid grid locally using automatic mesh adaptivity. A new methodology has also been implemented to limit the air volume to be discretized in the numerical model, thus reducing the size of the fluid mesh and allowing fine-mesh (adaptive) computer simulations in a reasonable CPU time.; Dans le cadre de l'étude de futurs moteurs contraroratifs (CROR), les industriels doivent pouvoir connaitre les éventuelles conséquences consécutivess à la perte de pales. Pour minimiser la taille de la zone de protection sur le fuselage d'avion (blindage), la zone d'impact possible doit être précisément évaluée. La simulation précise de la trajectoire d'un fragment d'aube resuière la prise en compte des forces aérodynamiques sur le fragment. L'objet principal de l'article réside dans le développement et la validation d'une méthodologie de simulation permettant de prendre en compte les effets aérodynamiques sur la trajectoire de tels débris.Pour cela, un modèle mixte Eléments Finis (du fragment) / Volumes Finis (du fluide) est mis en place avec prise en compte des interactions fluide/structure rendant compte des efforts aérodynamiques. Dans le cadre du projet EU Clean Sky SFWA, l'ONERA a développé ces méthodes d'interaction F/S dans le code EUROPLEXUS, pour améliorer la qualité de prédiction des forces aérodynamiques, ainsi qu'une nouvelle méthode visant à réduire la taille de volume fluide à représenter topoogiqueemnt autour de la structure afin de réduire les temps de calcul CPU.Le travail présenté met également l'accent sur une technique d'adaptativité (raffinement automatique du maillage) développée et couplée à la méthode de résolution de l'interaction Fluide/Structure. Des simulations aérodynamiques CFD (code ONERA elsA) sont utilisées comme références pour valider le traietement des interactions F/S dans EUROPLEXUS.

International audience; The Worst-Case Execution Time (WCET) is a critical parameter describing the largest value for the execution time of programs. Even though such a parameter is very hard to attain, it is essential as part of guaranteeing a real-time system meets its timing requirements. The complexity of modern hardware has increased the challenges of statically analysing the WCET and reduced the reliability of purely measured the WCET. This has led to the emergence of probabilistic WCETs (pWCETs) analysis as a viable technique. The low probability of appearance of large execution times of a program has motivated the utilization of rare events theory like Extreme Value Theory (EVT). As pWCET estimation based on EVT has matured as a discipline, a number of open challenges have become apparent when applying the existing approaches. Our paper enumerates key challenges while establishing a state of the art of EVT-based pWCET estimation methods.

International audience; The paper presents numerical models and simulations performed at ONERA to investigate aerodynamic effects on the trajectory of an open rotor blade fragment released or lost during an engine burst event. The models are based on finite elements for the structural part and on finite volumes for the fluid part, and are implemented in the EUROPLEXUS explicit code. Fluid–structure interaction is taken into account by an embedded (or immersed) technique and precision is enhanced by refining the fluid grid locally using automatic mesh adaptivity. A new methodology has also been implemented to limit the air volume to be discretized in the numerical model, thus reducing the size of the fluid mesh and allowing fine-mesh (adaptive) computer simulations in a reasonable CPU time.; Dans le cadre de l'étude de futurs moteurs contraroratifs (CROR), les industriels doivent pouvoir connaitre les éventuelles conséquences consécutivess à la perte de pales. Pour minimiser la taille de la zone de protection sur le fuselage d'avion (blindage), la zone d'impact possible doit être précisément évaluée. La simulation précise de la trajectoire d'un fragment d'aube resuière la prise en compte des forces aérodynamiques sur le fragment. L'objet principal de l'article réside dans le développement et la validation d'une méthodologie de simulation permettant de prendre en compte les effets aérodynamiques sur la trajectoire de tels débris.Pour cela, un modèle mixte Eléments Finis (du fragment) / Volumes Finis (du fluide) est mis en place avec prise en compte des interactions fluide/structure rendant compte des efforts aérodynamiques. Dans le cadre du projet EU Clean Sky SFWA, l'ONERA a développé ces méthodes d'interaction F/S dans le code EUROPLEXUS, pour améliorer la qualité de prédiction des forces aérodynamiques, ainsi qu'une nouvelle méthode visant à réduire la taille de volume fluide à représenter topoogiqueemnt autour de la structure afin de réduire les temps de calcul CPU.Le travail présenté met également l'accent sur une technique d'adaptativité (raffinement automatique du maillage) développée et couplée à la méthode de résolution de l'interaction Fluide/Structure. Des simulations aérodynamiques CFD (code ONERA elsA) sont utilisées comme références pour valider le traietement des interactions F/S dans EUROPLEXUS.

International audience; Large solid rocket motors are subjected to pressure oscillations for which the origin lies in the coupling between hydrodynamic instabilities and the first longitudinal acoustic modes of the combustion chamber. Static firing tests using two propellant grains in the combustion chamber have been performed. The pressure oscillation amplitude can be strongly modified by varying the burn velocity ratio between the two solid fuel grains. The pressure oscillations are significantly reduced when increasing the burn velocity of the upstream grain and are higher in the opposite case.

International audience; This paper describes the first application of 3D density reconstruction from a limited number of background oriented schlieren (BOS) images in a large research-type low speed wind tunnel. The tested flow is an ad hoc co-flowing hot jet generated at the wingtip of a simplified airfoil. Ray deviation maps captured by 12 synchronized cameras are combined to reconstruct the three dimensional density field of the jet, in the line of the direct 3D BOS technique described in Nicolas et al (2016 Exp. Fluids 57 1 – 21). A comparison with thermocouple sampling shows consistent results and highlights the efficiency of this new method for thermal measurement of a low speed convective flow. Finally, we underline the new possibilities for fluid dynamic characterization offered by combining stereo particle image velocimetry and 3D BOS measurements.

International audience; The Worst-Case Execution Time (WCET) is a critical parameter describing the largest value for the execution time of programs. Even though such a parameter is very hard to attain, it is essential as part of guaranteeing a real-time system meets its timing requirements. The complexity of modern hardware has increased the challenges of statically analysing the WCET and reduced the reliability of purely measured the WCET. This has led to the emergence of probabilistic WCETs (pWCETs) analysis as a viable technique. The low probability of appearance of large execution times of a program has motivated the utilization of rare events theory like Extreme Value Theory (EVT). As pWCET estimation based on EVT has matured as a discipline, a number of open challenges have become apparent when applying the existing approaches. Our paper enumerates key challenges while establishing a state of the art of EVT-based pWCET estimation methods.

International audience; Two-photon excitation laser-induced fluorescence of carbon monoxide (CO-LIF) is investigated experimentally in order to determine the applicability of this technique for imaging CO concentration in aeronautical combustors. Experiments are carried out in a high temperature, high-pressure test cell, and in a laminar premixed CH4/air flame. Influence of temperature and pressure on CO-LIF spectra intensity and shape is reported. The experimental results show that as pressure increases, the CO-LIF excitation spectrum becomes asymmetric. Additionally, the spectrum strongly shifts to the red with a quadratic dependence of the collisional shift upon pressure, which is different from the classical behavior where the collisional shift is proportional to pressure. Moreover, pressure line broadening cannot be reproduced by a Lorenztian profile in the temperature range investigated here (300–1750 K) and, therefore, an alternative line shape is suggested.; Une étude expérimentale de spectroscopie LIF à deux photons de la molécule CO (CO-LIF) est menée afin d'évaluer sa faisabilité en mode imagerie dans des moteurs aéronautiques. Les expériences sont réalisées d'une part dans une cellule à hautes température et pression et dans une flamme de prémélange CH4/air. Nous présentons l'influence de la température et de la pression sur l'intensité et la forme des spectres LIF de CO. Le spectre d'excitation devient asymétrique quand la pression augmente. Il est fortement décalé vers le rouge avec une dépendance quadratique du décalage collisionnel avec la pression, ce qui diffère de la classique dépendance linéaire. L'élargissement par pression du spectre n'est pas reproduit avec la fonction Lorentzienne et un profil collisionnel de Lindholm est utilisé pour simuler les spectres dans une certaine gamme de pression et températures.

Planar Particle Image Velocimetry (PIV) is a measurement technique that yields the instantaneous spatial structure in a planar cut of a flow. It exists in several forms (two-component, three-component or Stereo, and time-resolved), all of which are now considered to be mature, and as production tools for flow investigation in experimental facilities. This contribution is aimed at showing, through various examples of research activities, how it is currently being used at ONERA, with the idea of extending knowledge on complex flows, and therefore on the performance of complex systems. After a short reminder of the operating principle of planar PIV, applications are presented in the contexts of jet mixing physics, helicopter fuselage drag reduction, reacting flows, industrial wind-tunnels, and acoustics., AerospaceLab Journal, Issue 12, December 2016; ISSN: 2107-6596

International audience; This paper presents the experimental results of a hybrid rocket engine fired both at ambient pressure and under low-pressure conditions. The hybrid engine includes a catalyst bed and a vortex injector, and it is fitted with ultrasound sensors to measure the instantaneous fuel regression rate. These tests have enabled demonstration of the experimentally achievable specific impulse of the hybrid rocket technology under low-pressure conditions and validated the extrapolation of experimental results at ambient pressure to vacuum pressure conditions. The demonstrated combustion efficiency is above 98%, and the specific impulse is experimentally proven to be above 270 s for a conical nozzle with an expansion ratio of 50.

International audience; A new experimental setup has been built to study spray combustion. The design corresponds to a squared-duct channel with a bluff-body spanning over the entire width of the channel. Turbulent flow circulates around the obstacle and liquid fuel is injected at the rear of the body through a flat- fan nozzle. The two-dimensional configuration has been chosen to facilitate the optical measurements. Operating conditions reproduce partially those met inside a turboreactor. Non-reacting and reacting flows have been experimentally characterized but the paper lays emphasis on the later case. Spatial distribution of the droplets has been investigated with respect to the inter-droplet distance to the nearest neighbour and to the spatial distribution law at six locations upstream of the bluff body. Inter-droplet distance is obtained through the processing of Mie scaterring data. For the distribution law, comparisons between the experimental distribution, the theoretical exponential distribution and numerical results from an in-house Monte-Carlo solver demonstrate that the droplet distribution is equivalent to the exponential distribution. Besides, the numerical approach has been used to estimate the errors associated with the inter-droplet distance.

International audience; Time-constrained networks have demanded so far for deterministic modeling and analysis in order to guarantee their worst-case behavior. With this work we intend to apply both probabilistic modeling and probabilistic analyses to investigate such networks. The probabilistic framework we propose aims at guaranteeing confidence levels, in the form of probabilities, to the network timing constraints; the deterministic case remain a particular case, the worst-case, within the probabilistic framework. We focus on probabilistic bounds for defining probabilistic interfaces to network components and we study the way that probabilities propagate within networks by accounting for the dependences and the interactions between network components. Finally, we define and apply probabilistic performance metrics for evaluating network behavior with different degree of confidence due to the probabilities.; Les réseaux à contraintes de temps ont exigé jusqu'ici des modelés deterministes pour déterministes et garantir leur comportement le plus défavorable. Avec ce travail, nous avons l'intention d'appliquer le modélisation probabiliste et les analyses probabilistes pour étudier de tels réseaux. Le cadre probabiliste que nous proposons vise à garantir des niveaux de confiance, sous forme de probabilités, aux contraintes de synchronisation du réseau; le cas déterministe reste un cas particulier, le pire des cas, au sein du cadre probabiliste. Nous nous concentrons sur les limites probabilistes pour définir des interfaces probabilistes avec les composants du réseau et nous étudions la façon dont les probabilités se propager dans réseaux en tenant compte des dépendances et des interactions entre les composants du réseau. Enfin, nous définissons et appliquons des paramètres probabilistes de performance pour évaluer le réseau comportement avec différents degrés de confiance en raison de la probabilités.

International audience; This paper is devoted to a review of some recent studies conducted at ONERA within the framework of solid rocket propulsion for missiles, as well as space launchers. The viewpoint adopted is to present the physical phenomena studied using modeling, simulations and experimentations. Three major scientific topics will be investigated in this article: combustion of solid propellants; motor interiorballistics with a focus on two-phase flows, turbulence and radiative effects; rocket exhaust plumes, including phenomena in the vicinity of the aft body.; Cet article est consacré à un examen de certaines études récentes menées à l'ONERA dans le cadre de la propulsion solide pour les missiles ainsi que pour les lanceurs spatiaux. Le point de vue adopté est de présenter les phénomènes physiques étudiés en utilisant la modélisation, les simulations numériques et les expérimentations. Trois grands thèmes scientifiques seront étudiés dans cet article : la combustion des propergols solides, la balistique intérieure des moteurs avec un accent sur les écoulements diphasiques, la turbulence, les effets radiatifs et les jets de moteurs en y incluant les phénomènes au voisinage du corps arrière.

International audience; Combustion instability results from a coupling between acoustic and heat release fluctuations. From the analysis of published works by various research teams including ONERA, this paper describes the coupling lines involved, the model used to describe it and the methods developed to predict the thermo-acoustic risks. The application is focused on the liquid-fueled aero engine specificities. Recent results obtained at ONERA on the influence of the liquid flow behavior on these couplings are described and compared with LES results.; Les instabilités de combustion résultent d’un couplage entre des fluctuations de pression ou de vitesse acoustique et des fluctuations de dégagement de chaleur. A partir de l’analyse de travaux publiés par différentes équipes de recherche y compris l’ONERA, ce papier décrit les mécanismes de couplage, les modèles utilisés pour les décrire et les méthodes développées pour prévoir leur apparition. Cette analyse se focalise sur les spécificités liées aux chambres de combustion aéronautique fonctionnant avec un carburant liquide. Des résultats récents obtenus à l’ONERA sur l’influence du comportement de la phase liquide dans ce couplage sont décrits et comparés avec des résultats de simulation numérique utilisant une approche de type « LES ».

International audience; Hybrid propulsion generally combines a liquid oxidizer with a solid fuel. Compared to solid or bi- liquid engines, this type of propulsion offers advantages in terms of cost and flexibility. For several years, ONERA has been providing expertise in this area, both in experimental and numerical simulations. Various hybrid rocket motors have been designed and tested on ground, including under low ambient pressure conditions and in flight. The Propulsion Laboratory unit of the DMAE uses fully instrumented engine breadboards in order to optimize the oxidizer/fuel pair, as well as the injection system and the combustion efficiency. In addition, 0D and 1D codes for engine design areactively being developed. More recently, studies have been undertaken as part of the LEOP future satellite platforms, with the development of an innovative new combustion chamber.; La propulsion hybride combine généralement un oxydant liquide et un combustible solide. Comparé aux moteurs solides et bi-liquides, ce type de propulsion présente des avantages en termes de coût et de flexibilité. Depuis plusieurs années, l’ONERA offre une expertise dans ce domaine, par la réalisation à la fois d’études expérimentales et de simulations numériques. Différents moteurs hybrides y ont été conçus et testés au sol, y compris dans des conditions de haute altitude, et en vol. L’unité Laboratoire de Propulsion du DMAE utilise des moyens d’essais instrumentés pour optimiser le couple oxydant/combustible mais aussi le système d’injection et le rendement de combustion. En outre des codes 0D et 1D permettant la conception de ces moteurs y sont également développés. Plus récemment, des études ont été entreprises dans le cadre des futures plateformes de satellite de télécommunication avec le développement d’une architecture de chambre de combustion innovante.

The aim of this paper is to provide an overview of the ONERA test facilities devoted to the study of combustion in gas turbine engines. The objectives of the experimental studies performed with these test rigs are very ambitious and extend from building databases for the validation of codes and models used in numerical simulation to applied research for evaluating the performance of advanced aero injection systems in mono-sector, multi-sector or full annular combustion chambers. For more than ten years, aside from standard measurements (i.e., pressure, temperature, mass flow rates, gas analysis sampling), optical diagnostics have been widely associated with the test campaigns carried out in these rigs. Many optical methods are now very commonly used to measure for instance flow velocity fields, size and velocity of droplets, and the location of combustion zones. Other methods that are more difficult to implement, or still under development, are being increasingly used or proposed for measuring physical or chemical parameters, such as temperature, size of soot particles or concentration of combustion products. Examples of the results obtained with the ONERA test facilities and optical diagnostics are given, in order to illustrate the studies presented in this paper., AerospaceLab Journal, Issue 11, June 2016; ISSN: 2107-6596

International audience; Oxidizer injection plays a major role in the behaviour of hybrid rocket engines, especially regarding combustion efficiency and stability. This study aims to compare two firing tests with associated numerical simulations based on gaseous oxidizer axial or swirl injection through a catalyzer. The oxidizer and fuel couple used was H2O2 (87.5 %)/HDPE. Numerical 3D MILES (Monotone Integrated Large Eddy Simulation) simulations of both configurations were performed and analyzed regarding on one side the combustion efficiency influenced by propellants mixing, and on the other side the pressure oscillations provoked by the formation of large scale vortices in the aft-combustion chamber.

International audience; Hybrid propulsion technology suffers from low propulsive performances generally due to low combustion efficiency in regards to the other chemical propulsion systems. When hydrogen peroxide is used as oxidizer, one of the most promising ways to increase this efficiency combines a catalyst and a swirl injector in order to have an oxidizing gaseous stream and an improved mixing between the two propellants. A complementary solution to directly increase the propulsive performance consists of using hydrogen peroxide at higher concentration than the spatial grade (87.5%) which improves the theoretical specific impulse up to 12s for 98% H2 O2. This paper presents the development of a catalyst compatible with very high concentrated hydrogen peroxide (98%) and the firing tests performed with this catalyst coupled to a hybrid engine in order to highlight the increase in combustion efficiency.

International audience; Cet article présente les résultats d'une étude expérimentale d'un jet supersonique avec flamme de post-combustion, menée sur le banc MASCOTTE de l'ONERA. La distance d'apparition de la flamme de post-combustion (par auto-allumage) depuis le plan de sortie de la tuyère, et l'épaississement de la couche de mélange réactive ont été mises en évidence par imagerie de fluorescence induite par laser sur le radical OH (PLIF-OH). L'aérodynamique de la couche de mélange a été caractérisée par vélocimétrie par image de particules (PIV). L'ensemble des données de PLIF-OH et PIV ont été obtenues sur deux campagnes d'essais successives. L'emploi de ces deux techniques laser à haute cadence (~4 kHz) dans un jet supersonique avec post-combustion constitue, à la connaissance des auteurs, une première mondiale. Sur l'ensemble des essais menés en conditions réactives, des visualisations de l'émission de OH excité ont été synchronisées avec chacune de ces deux techniques laser, afin de tracer la zone de réaction et de disposer d'une référence de comparaison sur l'ensemble des essais. Si elle permet de mettre en évidence l'intermittence de la flamme, l'observation de séquences d'images instantanées successives obtenues par PLIF-OH montre qu'une cadence d'acquisition de 4 kHz reste insuffisante pour le suivi temporel des fines structures turbulentes dans un tel jet supersonique réactif. En revanche, à une cadence d'acquisition proche, le suivi temporel est possible sur des structures déduites des champs de vitesse obtenus par PIV dans la couche de mélange lorsque l'échelle spatiale de ces structures est suffisamment grande. Les mesures obtenues par PLIF-OH sont en accord avec les visualisations en champ large de l'émission de OH excité réalisées de manière synchrone avec l'imagerie LIF, lors de chaque essai.Les résultats obtenus dans cette étude ont permis de constituer une base de données de mesures de référence sur une flamme de post-combustion de propulseur. Cette base permettra de valider la simulation LES réactive mise en oeuvre pour simuler cette flamme. Les premiers résultats de simulation LES présentés dans cet article utilisent des modèles volontairement simples dans un premier temps, notamment en ce qui concerne la combustion turbulente. Les comparaisons entre ces simulations et les résultats expérimentaux montrent une amélioration par rapport aux simulations RANS, à la fois sur les niveaux de vitesse et sur la longueur de la flamme. Des perfectionnements des méthodes utilisées pour le calcul LES sont envisagés, comme le raffinement du maillage et la mise en place d'un modèle de combustion plus complexe.

International audience; Dans les foyers aéronautiques, l'allumage est actuellement réalisé à l'aide de bougies à arc, une méthode robuste mais qui possède de nombreux inconvénients. Une alternative serait de remplacer la bougie par un système d'allumage par laser. Afin de mieux comprendre les mécanismes intervenant dans le claquage laser et l'allumage du carburant, nous avons mis en place un montage multi-diagnostic pour l'étude du claquage dans l'air et dans un mélange kérosène/air. Les différents paramètres étudiés sont l'évolution spatio-temporelle du plasma et de l'onde de choc qu'il initie, le taux d'absorption de l'énergie incidente, ainsi que la spectroscopie d'émission. Une configuration en double-impulsion a également été étudiée.

International audience; Recent needs in the understanding and the quantification of wind tunnel flow characteristics led to the development on an innovative use of an existing PIV system for clinometric measurements at the ONERA F1 low speed pressurized wind tunnel in le Fauga-Mauzac center. The large industrial F1 wind tunnel is part of a full set of wind tunnels monitored by ONERA and ranging from low speed to high speed and high enthalpy flows. The motivation of this development originated from the need to better quantifiy flow up and side wash in the empty test section of the wind tunnel.In usual use of 3C-PIV systems, the 3 components of the velocity vector are evaluated from particle displacements of the order of 10 pixels in the image plane. Considering a typical uncertainty of 0.1 pixel, which is often a realistic estimate, the relative uncertainty on the velocity components cannot be better than about +/- 0.1 pixel/10 pixels = +/- 1 % of the flow velocity.This translates into uncertainty of the order of +/- 0.6° on flow angles, which is insufficient to qualify upwash and sidewash in an empty test section.To overcome this issue, benefit was taken from the fact that the flow in the empty wind tunnel section is nearly aligned with the wind tunnel axis and has a very low level of turbulence. As a consequence, iti is possible to keep patterns of particles within the laser sheet for very long times, and therefore to lengthen their displacement in the image plane. It was found that displacements of 100 to 200 pixels could be obtained, while keeping a high correlation factor between images, of the order of 50 % using the ONERA FOLKI-SPIV image processing software(1). PIV displacement estimation now limits the relative accuracy only to +/- 0.1 pixel/200 pixels = +/- 0/05 %, which translates into flow angles of +/- 0.03°. This high accuracy was also used to assess empty tunnel velocity, therefore complementing and even replacing tunnel calibration using static pressure measurements. Since 200 pixels corresponds to a displacement of a few centimetres, this comes at the cost that the laser sheet cannot be placed transversal to the flow, as done usually to investigate transversal distribution of flow angles.Results obtained with this technique were compared to measurements of the average flow upwash carried out at the test section centre thanks to the standard aircraft model inversion approach. Also, cross-comparison of PIV measurements from different test campaigns and different optical setups (both 2C- and 3C-PIV) were carried out. These consistent comparisons, together with uncertainty assessments, allow estimating that uncertainty on upwash and sidewash measurements is better than +/- 0.05°, strongly linked to image processing, occurrence of peaklocking and positioning of the calibration body in test section.This PIV technique allows investigations of flow angularity in areas where model inversion is not possible. For example, measurements near the test section floor have been achieved in order to determine upwash corrections to be applied on a model tested in ground effect. Compared with traditional 5-holes probing, this PIV-based technique has two important advantages: non-intrusiveness and high spatial density of measurements, enabling a better understanding of upwash and sidewash distribution in the test section and the capability to act towards its improvement.These measurements follow continuous progress in the capability to perform productive PIV measurements in the stringent environment of the F1 wind tunnel (optical access, pressurized conditions, remote-controlled optical system). Measurements have been performed fo Mach numbers between 0.15 ad 0.23, in majority at the maximum tunnel stagnation pressure of 3.85 bars.

International audience; The feasibility of digital holographic interferometry using a CW laser @ 532 nm and a Photron APX camera is demonstrated in the F4-ONERA hypersonic wind tunnel. This optical technique is used to point out the possible combustion of a small hydrogen jet in the shock layer developed on the model. The optical technique generates in the field under analysis, interference micro-fringes which are used as carrier spatial frequency. The field of optical thickness is obtained with a FFT2D post processing. Then, if the flow is assumed to be two-dimensional, the map of the refractive index can be estimated. The adjustment of the optical bench is easy to implement and the results obtained with this technique can be used for several interesting comparisons. From the phase difference maps, the holographic images and schlieren images in the x and y directions can be recalculated, which is not possible with a conventional schlieren optical setup. In addition, if the characteristics of the ionized gas are well known, the value of the gas density upstream and in the shock layer can be estimated.

The Electron Beam Fluorescence (EBF) technique is well-suited to providing local measurements in low-density high-speed flows for atmospheric reentry studies. High fluorescence yields are obtained from the excitation of the molecules or atoms of a gas flow with high energy electrons, which makes this technique advantageous for studying very low density gases. The most common measurement is flow field visualization with a sweeping electron beam (or sheet of electrons) from which shock structures of the flow can be observed and in certain cases a density map of the flow field can be obtained. Spectroscopic analysis of fluorescence leads to species detection as well as rotational or vibrational temperature measurements. This is particularly useful for characterizing the shock layer chemistry at non–equilibrium which usually occurs with high speed flows or in studying boundary gas-surface interactions. Velocity measurements are also possible using the Doppler shift principle or with a time of flight method with a pulsed electron beam., Journal Aerospace Lab, Issue 1, December 2009; ISSN: 2107-6596

International audience; The ATLAS simulation tool from SILVACO is used for 3D simulations. This software solves the transient semiconductor device equations in three dimensions, including the Poisson equation and the current continuity equations. The technology modeled in this work is a CMOS Bulk 0.18 urn process manufactured by ATMEL and transistors are designed for 1.8 V operation bias. The 3D inverter is modeled on a p-type silicon substrate. The doping profiles have been obtained by process simulation with ATHENA in order to obtain a realistic inverter device. The 3D structure is in agreement with the layout dimensions of this technology as shown on Fig. 1. The size of the NMOS and PMOS transistor,W/L, is respectively 1.4 and 2. For all simulations, the following models were used: Fermi-Dirac statistics, bandgap narrowing effect (BGN), Shockley-Read-Hall (SRH) and Auger recombination, impact ionization, and the Lombardi mobility [11] which takes into account the mobility variation with the normal and parallel electric field, doping concentration and temperature. In ATLAS, the magnitude decreases. Thus, one can presume that the wide temperature range of a spatial environment (from 218 to 418 K) can modify the shape of the SETs. In this paper, device simulations are performed at 218,300 and 418 K on a CMOS Bulk 0.18 urn inverter from ATMEL. We investigate the variations of the heavy-ions induced SETs for various impact locations at the three considered temperatures. This paper focuses on the voltage pulse width because its value is often used as a critical parameter in designing SET-mitigation circuits [2]. In the part II of the paper, the 3D modeled device and the simulation conditions are described. The part III shows the influence of the temperature on the SET pulse for a track crossing the off-NMOS drain (i.e. the sensitive region) and for a track striking the device far from this sensitive region. In the part IV, we complete the investigation with Spice simulations in order to define the implication of the temperature on the SETs propagation through a 10-inverters logic chain. Index Terms-Single event transient (SET), heavy-ion, temperature dependence, CMOS, LET, technology computer-aided design (TCAD) simulation. Abstract-In this paper, a study by device simulation of the heavy-ion induced Single-Event Transients (SET) is realized in the 218-418 K range in order to determine the temperature effect on a CMOS bulk 0.18 11m inverter. An investigation of the SET propagation though a 10-inverters logic chain is performed, and the threshold LET (LETth) required for unattenuated propagation through the inverters chain is determined. The LETth is calculated for two different location of the heavy ion impact and for three tern peratures. An increase of the sensitivity is found when the temperature raise from 218 to 418 K.

International audience