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Cr and Cr neutron capture cross sections measurement at the n_TOF facility at CERN
No full textInternational audienceCr are very relevant in criticality safety benchmarks related to nuclear reactors. The discrepancies between the neutron capture cross section evaluations have an important effect on the and in criticality benchmarks particularly sensitive to chromium. The Cr(n,) cross sections is to be determined between 1 and 100 keV with an 8-10% accuracy following the requirements of the NEA High Priority Request List (HPRL) to solve the current discrepancies. We have measured the neutron capture cross sections by the time-of-flight technique at the EAR1 experimental area of the n_TOF facility, using an array of four CD detectors with very low neutron sensitivity. The highly-enriched samples used are significantly thinner than in previous measurements, thus minimizing the multiple-scattering effects. We have produced, and analyzed with the R-matrix analysis code SAMMY, capture yields featuring 33 resonances of Cr and 51 of Cr with an accuracy between 5% and 9%, hence fulfilling the requirements made by the NEA. The differential and integral cross sections have been compared to previous data and evaluations. The new Cr(n,) cross sections measured at the CERN n\TOF facility provide a valuable input for upcoming evaluations, which are deemed necessary given that the results presented herein do not support the increase in both cross sections proposed in the recent INDEN evaluation
Microstructure optimization by combinatorial approach applied to Duplex Medium Manganese steels
No full textInternational audienceThis study introduces a novel combinatorial approach for optimizing the microstructure of duplex medium-manganese (Mn) steels by coupling a controlled thermal gradient with in situ high-energy X-ray diffraction (HEXRD) during intercritical annealing. A temperature gradient (680–720 °C) across a single sample enables real-time monitoring of phase transformations over a broad thermal range in one experiment. Compared to isothermal trials, this method offers high-resolution insight into austenite formation kinetics and phase stability, enabling accurate identification of the optimal temperature window for maximizing retained austenite. The results reveal a narrow optimal range (∼700–710 °C) where retained austenite fractions exceed 30 %, surpassing values from traditional methods. Post-mortem Electron Backscatter Diffraction (EBSD) analysis showed the spatial distribution of stabilized austenite, highlighting the complementary roles of in situ and ex situ characterization. This work demonstrates the potential of gradient-based combinatorial metallurgy to accelerate process optimization and support the design of high-performance third-generation advanced high-strength steels
Shape evolution in neutron-rich odd-even Nb isotopes
No full textInternational audienceNeutron-rich nuclei around exhibit multiple shape transitions. This region shows one of the sharpest transitions in the nuclear chart, from a spherical vibrator at to a strongly deformed prolate shape at , with largest deformations seen for Sr and Zr. Below , a spherical-to-oblate transition is predicted, while above and , the shape evolves from axial to triaxial. Even- nuclei have been well studied, but odd- isotopes such as Nb offer additional insights into these mechanisms. The Nb isotopes lie at the boundary between axially deformed Zr and triaxially deformed Mo nuclei. This work explores the structure of neutron-rich Nb nuclei up to , aiming to understand shape evolution with isospin and the onset of triaxiality. Two complementary fission experiments were used: (i) U+Be at GANIL in inverse kinematics with AGATA, EXOGAM, and VAMOS++, allowing prompt and delayed -ray spectroscopy with isotopic identification; (ii) spontaneous fission of Cf with the Gammasphere array providing high-fold -coincidence data. The level scheme of Nb was significantly extended with two new negative-parity bands. A revised scheme is proposed for Nb, differing from previous results, and new structures are reported in Nb. The signature splitting analysis indicates triaxial deformation for positive-parity bands, while negative-parity bands show axial symmetry, similar to Zr. This reveals a shape coexistence in neutron-rich Nb nuclei
Euclid: Improving redshift distribution reconstruction using a deep-to-wide transfer function
No full textInternational audienceThe Euclid mission seeks to understand the Universe expansion history and the nature of dark energy, which requires a very accurate estimate of redshift distribution. Achieving this accuracy relies on reference samples with spectroscopic redshifts, together with a procedure to match them to survey sources for which only photometric redshifts are available. One important source of systematic uncertainty is the mismatch in photometric properties between galaxies in the Euclid survey and the reference objects. We develop a method to degrade the photometry of objects with deep photometry to match the properties of any shallower survey in the multi-band photometric space, preserving all the correlations between the fluxes and their uncertainties. We compare our transfer method with more demanding image-based methods, such as Balrog from the Dark Energy Survey Collaboration. According to metrics, our method outperforms Balrog. We implement it in the redshift distribution reconstruction, based on the self-organising map approach of arXiv:1509.03318, and test it using a realistic sample from the Euclid Flagship Simulation. We find that the key ingredient is to ensure that the reference objects are distributed in the colour space the same way as the wide-survey objects, which can be efficiently achieved with our transfer method. In our best implementation, the mean redshift biases are consistently reduced across the tomographic bins, bringing a significant fraction of them within the Euclid accuracy requirements in all tomographic bins. Equally importantly, the tests allow us to pinpoint which step in the calibration pipeline has the strongest impact on achieving the required accuracy. Our approach also reproduces the overall redshift distributions, which are crucial for applications such as angular clustering
2D or not 2D? Exploring 3D relativistic magnetic reconnection dynamics with highly accurate numerical simulations
No full textInternational audienceFast reconnection in magnetically dominated plasmas is widely invoked in models of dissipation in pulsar winds, gamma-ray flares in the Crab nebula, and to explain the radio nanoshots of pulsars. When current sheets evolve reaching a critical inverse aspect ratio, scaling as with the plasma Lundquist number, the so-called \textit{ideal} tearing instability sets in, with modes growing, independently of , extremely rapidly on timescales of only a few light-crossing times of the sheet length. We present the first set of fully 3D simulations of current-sheet disruption triggered by the ideal tearing instability within the resistive relativistic MHD approximation, as appropriate in situations where the Alfvén velocity approaches the speed of light. We compare 3D setups with different initial conditions with their 2D counterparts, and we assess the impact of dimensionality and of the magnetic field topology on the onset, evolution, and efficiency of reconnection. In force-free configurations, 3D runs develop ideal tearing, secondary instabilities, and a thick, turbulent current layer, sustaining dissipation of magnetic energy longer than in 2D. In pressure-balanced current sheets with a null guide field, 2D reference runs show the familiar reconnection dynamics, whereas in 3D tearing dynamics is quenched after the linear phase, as pressure-driven modes growing on forming plasmoids outcompete plasmoid coalescence and suppress fast dissipation of magnetic energy. Taken together, these results suggest that the evolution and efficiency of reconnection depend sensitively on the local plasma conditions and current-sheet configuration, and can be properly captured only in fully 3D simulations
Exploring the structural evolution of the NdFeB magnets with various carbon contamination in the PIM process
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Measurement of differential -channel single top (anti)quark production cross-sections at 13 TeV with the ATLAS detector
No full textInternational audienceThe production of single top quarks and top antiquarks via the -channel exchange of a virtual boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider. The full Run 2 data sample recorded with the ATLAS detector in the years 2015-2018 is used, corresponding to an integrated luminosity of 140 fb. The absolute and normalised production cross-sections are measured differentially as a function of the transverse momentum and absolute rapidity of the top quark and top antiquark. In addition, the ratio of top quark to top antiquark production cross-sections is measured. The measured distributions are compared with next-to-leading-order quantum chromodynamics predictions obtained with different combinations of matrix-element generators, parton-shower programs and proton parton distribution functions, as well as to next-to-next-to-leading-order calculations. Overall, good agreement is observed between the measurements and the theoretical predictions. For most measured distributions, the sensitivity to differences between the predictions is limited by the systematic uncertainties in the measurement. The measured differential distributions are also interpreted in an effective field theory approach to constrain the Wilson-Coefficient associated with a four-quark operator. The interpretation accounts for the effect of the selection efficiency, which is altered significantly by non-zero contributions from
Production Scientifique de la collaboration EEDIN: Étude Expérimentale de la Diffusion Inélastique du Neutron
No full textThis page lists the scientific production of the EEDIN collaboration.The EEDIN ("Étude Expérimentale de la Diffusion Inélastique du Neutron", Experimental Study of Inelastic Neutron Scattering) collaboration brings together teams from CNRS/IPHC, CEA/DAM, and CEA/DES to study inelastic neutron scattering reactions, which are essential for innovative nuclear fuel cycles (Th/U, U/Pu). Its activities focus on experimental measurements, theoretical modeling, and nuclear data evaluation.EEDIN plays a key role in improving nuclear data for Generation IV reactors and innovative cycles by combining experimental, theoretical, and applied expertise.The collaboration work was funded in part by the CNRS multipartner NEEDS program, by the European Union under grant agreement 101164596 - APRENDE Project.La collaboration EEDIN (Étude Expérimentale de la Diffusion Inélastique du Neutron) rassemble des équipes du CNRS/IPHC, du CEA/DAM et du CEA/DES, autour de l’étude des réactions de diffusion inélastique des neutrons, essentielles pour les cycles de combustibles nucléaires innovants (Th/U, U/Pu). Ses activités s’articulent autour de mesures expérimentales, de modélisation théorique et d’évaluation de données nucléaires.EEDIN joue un rôle clé dans l’amélioration des données nucléaires pour les réacteurs de 4ᵉ génération et les cycles innovants, en combinant expertise expérimentale, théorique et appliquée.Ce travail collaboratif a été financé en partie par le programme multipartenarial NEEDS du CNRS, ainsi que par l'Union européenne dans le cadre de la convention de subvention 101164596 - Projet APRENDE
GATE 10 Monte Carlo particle transport simulation: I. Development and new features
No full textInternational audienceWe present GATE version 10, a major evolution of the open-source Monte Carlo simulation application for medical physics, built on Geant4. This release marks a transformative evolution, featuring a modern Python-based user interface, enhanced multithreading and multiprocessing capabilities, the ability to be embedded as a library within other software, and a streamlined framework for collaborative development. In this Part 1 paper, we outline GATE’s position among other Monte Carlo codes, the core principles driving this evolution, and the robust development cycle employed. We also detail the new features and improvements. Part 2 will focus on the architectural innovations and technical challenges. By combining an open, collaborative framework with cutting-edge features, such a Monte Carlo platform supports a wide range of academic and industrial research, solidifying its role as a critical tool for innovation in medical physics
Iron Metallurgy in Ancient Cambodia: Production Dynamics, Traditions and Chronologies in a Southeast Asian Context (9th–14th centuries CE)
No full textInternational audienceCollaborative studies in iron archaeometallurgy in Cambodia over the past decade, particularly through the IRANGKOR project, have advanced our understanding of iron production dynamics during the Angkorian period (9th–15th centuries CE). This research examines metallurgical remains and artifacts within a systemic framework, linking them to production sites, geological contexts, and usage settings, such as iron clamps in monumental constructions. Studied diachronically and across multiple spatial scales, these remains provide insights into production practices and “recipes,” production dynamics, and the circulation and supply of iron, particularly within the central production territory of Phnom Dek, historically recognized for its metallurgical tradition.The study explores the relationships between resources, production processes, metallurgical practices, and iron circulation. Central to the research is the use of provenance analyses, direct dating of the metal itself, and the examination of comparative patterns, providing precise chronological and spatial benchmarks. Combining historical and archaeological sources with material analysis of artifacts and smelting debris establishes a framework for interpreting these dynamics across the Angkorian territory.The resulting datasets reveal changes in metallurgical “recipes” as well as in supply strategies and demands over more than 1,400 years. This presentation synthesizes recent results, highlighting the contribution of compositional and chronological data to frameworks for understanding continuities and changes in ancient metallurgical practices. Situating these findings within a broader Asian context highlights similarities in practices and recipes and their implications for regional technical dynamics