HAL Université de Savoie
Not a member yet
59053 research outputs found
Sort by
Génération par autocorrélation de signaux THz et de second harmonique à la surface de cristaux diélectriques
No full textInternational audienceLe redressement optique (Optical Rectification OR) d'impulsions laser femtosecondes à la surface d'un cristal est un moyen de produire des impulsions térahertz (THz) ultracourtes dont la largeur de bande pourrait dépasser des dizaines de THz. En effet, comme il n'y a pas de propagation dans le cristal, les effets dépendant de la longueur d’onde, comme l’absorption ou l’accord de phase, ne sont plus limitant. Cependant, le principal inconvénient vient de la faible efficacité de l'interaction, qui se traduit par une faible puissance THz, inférieure de plusieurs ordres de grandeur à celle qui pourrait être obtenue en transmission. Pour détecter de tels signaux, il est donc nécessaire d'utiliser un système à la fois à large bande et sensible, ce qui représente un défi dans le domaine THz où les détecteurs sont soit large bande mais peu sensibles, comme ceux utilisant l’effet electro-optique,, soit très sensibles mais très lents, comme les bolomètres. La technique d'autocorrélation [1], habituellement utilisée pour caractériser les impulsions laser ultra-courtes, peut apporter une solution intéressante à ce problème. Dans cette configuration, deux impulsions laser femtosecondes successives, séparées par un délai variable , se superposent dans un cristal non linéaire. Le signal, généralement obtenu par génération de seconde harmonique (Second Harmonic Generation SHG), est ensuite enregistré en fonction de . Le détecteur peut ainsi être très lent puisque la résolution temporelle ne dépend que de . Nous avons adapté cette technique à la caractérisation d’impulsions THz large bande générées par redressement optique d'impulsions laser femtosecondes à la surface de différents cristaux non linéaires, tels que ZnTe [2], GaP, LiNbO3 ou encore GaSe. L’interférogramme SHG a été simultanément enregistré comme outil de comparaison. Nous avons ainsi vérifié que l’épaisseur du cristal ou le désaccord de phase entre l’onde optique et l’onde THz n’ont aucun effet sur l’interférogramme obtenu. Nous avons aussi démontré que cette technique permet bien d’enregistrer la réponse spectrale du cristal utilisé comme par exemple des raies d’absorption dues à la présence de phonons
The DUNE Phase II Detectors
No full textInternational audienceThe international collaboration designing and constructing the Deep Underground Neutrino Experiment (DUNE) at the Long-Baseline Neutrino Facility (LBNF) has developed a two-phase strategy for the implementation of this leading-edge, large-scale science project. The 2023 report of the US Particle Physics Project Prioritization Panel (P5) reaffirmed this vision and strongly endorsed DUNE Phase I and Phase II, as did the previous European Strategy for Particle Physics. The construction of DUNE Phase I is well underway. DUNE Phase II consists of a third and fourth far detector module, an upgraded near detector complex, and an enhanced > 2 MW beam. The fourth FD module is conceived as a 'Module of Opportunity', aimed at supporting the core DUNE science program while also expanding the physics opportunities with more advanced technologies. The DUNE collaboration is submitting four main contributions to the 2026 Update of the European Strategy for Particle Physics process. This submission to the 'Detector instrumentation' stream focuses on technologies and R&D for the DUNE Phase II detectors. Additional inputs related to the DUNE science program, DUNE software and computing, and European contributions to Fermilab accelerator upgrades and facilities for the DUNE experiment, are also being submitted to other streams
Kaon Physics: A Cornerstone for Future Discoveries
No full textInternational audienceThe kaon physics programme, long heralded as a cutting-edge frontier by the European Strategy for Particle Physics, continues to stand at the intersection of discovery and innovation in high-energy physics (HEP). With its unparalleled capacity to explore new physics at the multi-TeV scale, kaon research is poised to unveil phenomena that could reshape our understanding of the Universe. This document highlights the compelling physics case, with emphasis on exciting new opportunities for advancing kaon physics not only in Europe but also on a global stage. As an important player in the future of HEP, the kaon programme promises to drive transformative breakthroughs, inviting exploration at the forefront of scientific discovery
Search for the decay
No full textInternational audienceA search for the decay is reported using proton-proton collision data collected with the LHCb detector between 2011 and 2018 at centre-of-mass energies of 7, 8, and 13 , corresponding to an integrated luminosity of . No significant signal is observed. Using the decay as a normalisation channel, an upper limit for the ratio of branching fractions is set at the 90 (95)% confidence level
Branching fraction measurement of the decay
No full textInternational audienceThe branching fraction of the decay , relative to the topologically similar decay , is measured using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of . The ratio is found to be , where the first uncertainty is statistical and the second systematic. Using the world-average branching fraction for , the branching fraction for the decay is found to be , where the first uncertainty is statistical, the second systematic, and the third is due to the branching fraction of the normalization channel
Sur la gamification du risque inondation : le simulateur ReFlood: De données hydrologiques complexes aux récits interactifs d'inondations
No full textInternational audienceEven when populations are aware of their exposure to risks, flood management and information systems remain poorly identified. Various regulatory documents report on risk areas identified through observation and numerical simulation, as well as on prevention, protection, and safeguard measures. However, the risk situation remains challenging to grasp concretely. Moreover, in the face of climate change, uncertainty has become more than ever a challenge in modeling and management. In this context, improving risk representation and awareness mechanisms represents a significant challenge.To integrate these two aspects, we used a video game engine along with field and flow data to design the real-time simulator ReFlood. The goal is to offer a realistic 3D rendering of floods, which can be used in workshops to design and debate flood and urbanization scenarios. While the results of a simulator that prioritizes speed are not as precise as those of numerical simulations, modeling uncertainty can be evaluated and explained, reinforcing trust in ReFlood’s results and its ability to serve as an intermediary object between stakeholders.The I.S. RIVERS 2025 conference has been chosen to present the simulator to an audience of scientists and territorial actors, in order to gather their feedback on the results, the simulator, and its treatment of uncertainty, as well as on potential uses for flood risk representation, mediation, and awareness-raising.Même lorsque les populations connaissent leur exposition aux risques, la gestion des inondations et les systèmes d'information restent encore mal identifiés. Différents documents réglementaires rendent compte des zones à risques identifiées par observation et simulation numérique, ainsi que des mesures de prévention, de protection et de sauvegarde. Mais la situation de risque reste difficile à appréhender concrètement. Par ailleurs, face au dérèglement climatique, l'incertitude constitue plus que jamais un défi en matière de modélisation et de gestion. Dans ce contexte, l'amélioration des dispositifs de représentation et de sensibilisation au risque représente un réel défi.Pour intégrer ces deux aspects, nous avons utilisé un moteur de jeu vidéo avec des données de terrain et de débit pour concevoir le simulateur temps-réel ReFlood. Le but est d'offrir un rendu réaliste en 3D de l'inondation, utilisable en atelier pour concevoir et mettre en débat des scénarios d'inondation et d'urbanisation. Si les résultats d'un simulateur qui privilégie la rapidité ne sont pas aussi précis que ceux d'une simulation numérique, l'incertitude de modélisation peut être évaluée et expliquée, confortant la confiance dans les résultats de ReFlood et sa capacité à servir d'objet intermédiaire aux échanges entre protagonistes. La conférence I.S. RIVERS 2025 est choisie pour présenter le simulateur à une audience de scientifiques et d'acteurs du territoire afin de recueillir leurs réactions sur les résultats, le simulateur et l'incertitude, mais aussi sur les usages potentiels en matière de représentation du risque inondation, de médiation et de sensibilisation.</p
Aseismic creep and strain partitioning accommodating the Nubia-Eurasia oblique convergence in northern Africa from InSAR analysis
No full textInternational audienceThe northern Africa region faces significant seismic and tsunami hazards, driven by the ongoing convergence between the Nubian and Eurasian plates. Using radar interferometry (interferometric synthetic aperture radar, InSAR) analysis, we provide constraints on the interseismic behavior of tectonic structures within the region between ∼2°W and ∼11°E using the first InSAR-derived regional-scale maps of east-west and vertical velocity components. Despite the unresolved N-S−oriented motions due to inherent limitations to the InSAR technique, our millimeter-per-year level velocity maps reveal three distinct domains of strain accommodation along the plate boundary. In Western Tell, both onshore and offshore folds and thrusts accommodate frontal collision, regularly generating large reverse earthquakes, such as the Ms 7.3 El Asnam earthquake of 1981. In the Eastern Tell, deformation is widely distributed from the Saharan Platform to the northern coastlines. In the Central Tell, we identify the predominantly aseismic behavior of the 500-km-long Ghardimaou-North-Constantine fault, marked by a shallow locking depth (<5.1 ± 0.5 km) and standing out as one of the slowest (<2.5 mm/yr) continental strike-slip faults ever detected with geodetic data. Strain partitioning diverts most of the shear component of the oblique convergence into this major inland structure, thereby making the offshore thrusts and folds the principal sources of seismic hazard
Recycling primary batteries through the selective precipitation of zinc thanks to imidazolate linkers
No full textInternational audienc
La mesure de l'intérêt général à travers la loi, Essai d'une approche jurimétrique
No full textInternational audienceThe continuous process of standard rationalization is experiencing a renewed dynamic in the era of artificial 8 D. Loschak, « L'administration dans le discours des présidents de la V</div
Experimental study of thermocline behavior under high propagation velocities in a water based thermal energy storage
No full textInternational audienceThis experimental study investigates the development of the thermocline under varied operating conditions and particularly at high propagation velocities ranging from 0.5 mm.s -1 up to 8 mm.s -1 and temperature differences (ΔT) of 10 • C, 30 • C and 65 • C. For this purpose, a new experimental setup, designed to investigate thermocline formation, propagation, and withdrawal is implemented. The setup meets essential requirements for acquiring controlled validation data for CFD models and enables the collection of novel high-velocity flow data. The storage system features extensive instrumentation, including temperature measurements at curved tank bottoms and radial positions. Dynamic experiments validated literature findings, demonstrating stronger stratification with slower axial propagation velocities and larger temperature differences. High propagation velocities remain feasible with adequate ΔT, i.e. with a Richardson number based on the penetration height of the inlet fluid, Ri 0,hi ≥ 0.25 ensuring a thin thermocline for this test section. Variation of the extraction distribution system revealed the influence of fluid withdrawal on thermocline thickness, underscoring the need to consider outlet dynamics in distributor design. These findings establish the relevance of Ri 0,hi for predictive performance correlations and provide a foundation for optimizing thermal energy storage systems through refined distributor designs. Finally, an original definition of thermocline thickness was introduced, based on the slope of the thermocline, offering an alternative to the classical boundary-temperature approach and limiting the dependence on temperature limits