Pablo Caron

Les environnements radiatifs sont critiques pour l’intégrité des systèmes électroniques embarqués. Peuplés de particules plus ou moins énergétiques, ces environnements peuvent provoquer des dysfonctionnements qui, suivant les dommages occasionnés, peuvent être identifiés. Ce manuscrit porte ssentiellement sur les pannes non destructives, et plus particulièrement sur les SEU (Single Event Upset) dont les conséquences sont les basculements indésirables de certains points mémoires. Ce faisant, l’information initialement stockée peut être perdue. La thématique de la sensibilité des mémoires aux événements singuliers a pris naissance dans les années 70. Les premières erreurs observées ont été provoquées par des particules lourdes, associées à des pouvoirs ionisants élevés. Ces dernières, en traversant les dispositifs, engendrent des cascades électroniques particulièrement intenses. Aujourd’hui, les mémoires proposent des nœuds technologiques de l’ordre de la dizaine de nanomètres. Ainsi, sur les décennies qui nous séparent des premières observations des événements singuliers, les cellules mémoires ont vu leurs dimensions secomprimer drastiquement. D’un point de vue sensibilité, cela aurait pu aller dans le bon sens mais c’était sans compter sur la réduction des tensions d’alimentation qui s’est opérée dans le même temps. Ce manuscrit s’inscrit dans cette évolution et tâche d’analyser les conséquences qui ont alors émergées.Le transport des particules est une thématique commune à tant de sujets. Et la sensibilité des mémoires n’y échappe pas. D’autant que la contrition des composants nous impose maintenant une certaine rigueur : il nous revient de réaliser le transport des particules sur des échelles nanométriques. Ainsi, nous avons travaillé sur le développement et l’implémentation de nouveauxmodèles physiques dans un code de transport, GEANT4. Ces travaux nous permettent de suivre les cascades électroniques jusqu’à des énergies très basses, une condition indispensable pour les autres études que nous avons menées.Des électrons aux protons, nous avons investigué l’ensemble des processus physiques potentiellement impliqués dans les déclenchements d’erreur. Plusieurs résultats inédits ont ainsi été obtenus et démontrés : le rôle des interactions Coulombiennes sur les sensibilités mesurés en environnements électrons, et celui, propre aux diffusions élastiques, dans le cas des environnementsprotons. Le comportement des mémoires sous ces deux types d’environnement, les dynamiques qu’ils imposent sur les courbes de sensibilité, nous ont, par la suite, guidés vers une méthode de calibration des paramètres de simulation. Cette dernière étude offre d’ailleurs un moyen de prédiction de la sensibilité des composants pour des environnements auxquels ils n’ont pas ététestés. Enfin, ce manuscrit se conclura sur une dernière étude, plus proche du composant, où l’on regardera les transitoires générés par des faisceaux d’électrons sur un inverseur ultrascale.

Accurate modeling of radiation belt fluxes is crucial for space weather forecast and spacecraft design, yet the process relies heavily on simulating detectors within degraded satellite geometries. Focusing on the JASON2 satellite and ICARE_NG data this paper has two main objectives: to identify the minimum angular resolution suitable for flux inversion via sensitivity analysis, and to provide guidelines for using thickness-based sector analysis geometry to optimize computation time and protect confidential satellite design information. For protons, errors on the flux remain below 10% across the initial detector sensitivity, regardless of the sector analysis geometry quality. However, an energy shift occurs: sensitivity to low energies in the initial spectrum decreases, while a virtual sensitivity appears at higher energies. Maintaining low-energy sensitivity requires a thickness-based sector analysis with at least 20×40 resolution. Electrons are far more sensitive, also requiring this minimum resolution to limit errors on the reconstructed flux. to keep errors under 20%. Refining key regions, such as the finer parts of the detector, allows reconstructed fluxes to cover the full energy range with errors below 5%, while reducing computational load and preserving the confidentiality of the satellite geometry.

The effects of the space radiation on spacecraft materials and devices are significant design considerations for space missions. In order to meet these challenges, the radiation environment must be understood. Measuring energetic particles in the radiation belts is therefore crucial, and this is why ICARE (Influence sur les Composants Avancés des Radiations de l’Espace) radiation monitors have been developed over several decades. Two ICARE_NG² (for the second version of the New Generation of the instrument) radiation monitors have recently been launched on HotBird 13F and 13G satellites at the end of 2022, reaching the geostationary orbit in 2023 and providing measurements of electrons of the outer belt. The methods used to derive these electron fluxes are detailed and the results compared with NGRM (Next Generation Radiation Monitor) and specification models. The observed electron dynamics are strongly correlated with solar wind data, and a fully analytical model is developed. This model provides an accurate representation of the measurements, using a limited number of parameters.

We use an open-source simulation software to design III-V multi-junction solar cells containing a dilute nitride subcell. We discuss the different modeling techniques in terms of physical models and numerical methods, and provide an educated guess for a GaInP$_{2}$ - GaAs - GaInAsN - Ge lattice-matched 4-junction solar cell performance assessment. We suggest a way to ensure an effective computation of the main output values of an open-source Poisson-Drift-Diffusion solver for multi-junction solar cell analysis. An optimization of a multi-junction cell including a n-i-p subcell is performed, starting from basic theoretical considerations, to the use of a double-layer anti-reflective coating to target the most limiting subcell, and then with an optimization of the n-i-p architecture in the 1eV subcell with respect to the GaInAsN layer properties. We show that the detrimental effects of low diffusion lengths in the GaInAsN layer can be alleviated by taking advantage of field-assisted collection.

The goal of this paper is to develop the necessary numerical models to study the differences of the induced current pulse shapes of protons and electrons in solid-state detectors (SSD), all while validating these models with an experimental test bench. The shape of the captured current pulse created by the passage of the particle in the SSD is indicative of the nature of the particle, which we aim to predict using the information in the pulse shape. The performances and limits of such a system are explored here in the scope of proton/electron discrimination in Earth’s radiation belts. This provides a meaningful asset to the methods used in radiation monitors nowadays which mostly rely on total energy deposited.

Eutelsat 7C (E7C), a telecommunication spacecraft, was launched on 21 ^st of June 2019 and reached geostationary (GEO) orbit four months later after a quasi-equatorial electric orbit raising (EOR) phase. An ICARE-NG (Influence sur les Composant Avancés des Radiations de l’Espace, Nouvelle Génération) radiation monitor was implemented on the spacecraft allowing measurements of electron and proton flux as well as Single Event Upset (SEU) effect affecting various static random access memories (SRAMs) and dynamic random access memories (DRAMs). According to the cruise to GEO profile, two phases could be deduced, a first one where SEU events are dominated by trapped protons and a second one where they are attributed to cosmic rays and solar proton events. In this paper, SEU events attributed to trapped particles as well as proton flux recorded by ICARE-NG are used to benchmark proton specification models, Aerospace Proton version 8 (AP8), Aerospace Proton version 9 (AP9) and Global Radiation Earth ENvironment-proton (GREEN-p). Although, the 3D shielding of the spacecraft and payload is considered to transport accurately the proton environment down to the chip, ground tests to define cross section were not reliable enough to draw clear conclusion on specification model performances along EOR orbits.

Measurements of particle fluxes obtained with the latest version of Influence sur les Composants Avancés des Radiations de l’Espace (ICARE), called ICARE_NG², onboard Hotbird 13F and Hotbird 13G satellites, are presented. Compared to previous versions of ICARE, a wider range of particle energies is measured. Indeed, low-energy protons are now available, down to ~ 5 MeV. The missions consist of Electric Orbit Raising (EOR) phases (launched at the end of 2023), followed by an operational orbit in Geostationary Orbit (GEO). The EOR periods are analyzed through a series of comparisons. Very good agreements are observed with other instruments while significant discrepancies are found with engineering models as AE/P8, AE/P9 and Global Radiation Earth Environnement (GREEN). The average fluxes recorded during the EOR phases are presented and compared with the engineering models. None of the models used can accurately reproduce the observed fluxes. Such results will help to optimize specifications for future space missions.

The aim of this work is to analyze the influence of the guard rings (GRs) in solid state detectors (SSDs). Depending on the applied potential, the collection of charges can be disturbed. A study on SSDs with floating and grounded GRs is conducted. The tools needed to do so are presented (GEANT4, Sentaurus and Garfield++). Experimental measurements have been performed on Micron Semiconductor Ltd SSDs which are composed of multiple guard rings (MGRs). Finally, a first application on the ICARE_NG² (Influence sur les Composants Avancés des Radiations de l’Espace) radiation monitor is proposed with a comparison of the response functions (RFs) according to the potential applied on the GRs. Improved performances are observed when the GRs are grounded. A second application on the ICARE_NG currently embedded on Eutelsat 7C (E7C) is also proposed by using the GRs as active shielding, allowing improvements in the measurement of high energy particles.

The simulation of charge collection in solid state detectors (SSD) can be carried out with TCAD or Shockley-Ramo paradigms. These two paradigms have their limitations when simulating a large variety of cases, spanning from types of radiation, energy ranges, substrate doping concentration and applied bias. The aim of this paper is to explore the limits of these tools for the energy ranges of protons and electrons of the Earth’s radiation belts, as well as establish a benchmark of the different simulation codes that implement these paradigms. Proton, electron and alpha irradiation are carried out using a fast current amplifier and several different diodes. A 1D TCAD code has been developed and is presented here. Comparisons are then made with the other calculation paradigms for different types of irradiation conditions and diodes, showcasing which codes work best for the different configurations.