Cea Leti

Phase change memories (PCMs) are at the heart of modern memory technology, offering multi‐level storage, fast read/write operations, and non‐volatility, bridging the gap between volatile DRAM and non‐volatile Flash. The reversible transition between amorphous and crystalline states of phase‐change materials such as GeTe or Ge2Sb2Te5 is at the basis of PCM devices. Despite their importance, PCM devices face challenges including high power consumption during the RESET operation. Current research efforts focus on improving device architecture and exploring alternative phase‐change materials such as GeTe/Sb2Te3 super‐lattices (SLs), for which a reduced programming power consumption is observed compared with standard PCMs. Herein, by combining X‐ray diffraction and scanning transmission electron microscopy imaging of SL thin films with the study of the same SL in PCM devices, it is shown that it is possible to significantly decrease RESET energy of the device, without modifying the SL composition, by reducing the amount of structural defects through annealing treatment. The best device properties are obtained after transforming the SL into a defect‐free, highly out‐of‐plane oriented rhombohedral phase. These results offer a promising avenue for further improving the performance of SL‐based PCM devices through structural optimization.

Our research aims to enhance smart orthopedic knee implants used in Total Knee Arthroplasty (TKA). With the projected quadrupling of TKA demand by 2030 due to factors like aging populations, rising obesity rates, and broader indications for younger patients, our focus is on instrumented medical implants to measure knee parameters. In this paper, we report the optimization of a wireless power transmission system for powering smart knee implants, employing an established HF Near-field Resonant Inductive Coupling (NRIC) technique at $13.56 \,\mathrm{M}\mathrm{Hz}$ inside the stem of a tibial knee implant. We propose a pragmatic optimization approach in this study, guided by the integration constraints of a knee implant and validated by orthopedic surgeons through cadaveric specimen testing. Finite Element simulations guided the selection of a frontal 3-turn solenoid (called “paperclip” coil) at the Rx side, located at the tip of the stem, which demonstrated balanced performance metrics and reasonable volume occupancy (1.6 cm ³ ). Power transfer measurements were conducted through conductive solutions mimicking skin, muscle, and bones. At $13.56 \,\mathrm{M}\mathrm{Hz}$ , a power transfer efficiency $\eta$ of 30% and 7.5% ( $300 \,\mathrm{m}\mathrm{W}$ and $75 \,\mathrm{m}\mathrm{W}$ at $1 \,\mathrm{W}$ input power) was achieved at Tx-Rx distances of $25 \,\mathrm{m}\mathrm{m}$ and $40 \,\mathrm{m}\mathrm{m}$ respectively. The proposed solution was implanted in a cadaveric specimen : $250 \,\mathrm{m}\mathrm{W}$ was obtained at an estimated $30 \,\mathrm{m}\mathrm{m}$ distance for an input power of $1 \,\mathrm{W}$ at the Tx side. For the same distance, we also performed a successful DC power provision up to $64 \,\mathrm{m}\mathrm{W}$ at $3 \,\mathrm{V}$ DC and data transfer functions at $26\, \mathrm{kbit\,s}^{-1}$ in the cadaver. The proposed system, with its integration strategy, holds promise in powering advanced sensor functions, contributing to the identification and monitoring of postoperative complications and potentially reducing the need for long-term revisions.

This document presents a novel architecture of a microelectromechanical system (MEMS) gyroscope for in-plane angular rate sensing (i.e. pitch or roll axis), with a detailed characterization of the performance, including effects of etching nonuniformities and quadrature, which are relevant when dealing with these specific sensing axes. The adopted technology features 20- $\mu$ m-thick frames and springs, and 250-nm-thick and -wide resistive gauges, which are subject to stress under Coriolis-force-induced tilt of a torsional lever. The new design increases by a factor larger than 3 the efficiency of the transduction between tilting of the Coriolis frame inside the gyroscope and corresponding stress on the resistive gauges, in turn improving scale-factor, and bringing noise and stability down to record levels for pitch or roll planar silicon micromachined gyroscopes. At the same time, with respect to a former architecture, a comparative analysis of the impact of the new design choices on the dispersion of the mode-split value is carried out. Results demonstrate that the dispersion increases by a negligible amount, from 36 Hz (old design) to 44 Hz (new design). Most of tested gyroscopes have quadrature value within 5000 dps: however, within a 6-V supply operated board, only part of these sensors could be properly operated under automatic quadrature compensation, reaching under these conditions noise in the range of 0.02 $^{\circ}$ / $\surd$ hr and the minimum of the Allan deviation at 0.12 $^{\circ}$ /hr. 2024-0124

On 12 August 2021 a large Mw 8.1 earthquake, detected by global seismic networks, occurred on the South Sandwich subduction zone in the southern Atlantic Ocean. Approximately 1.5 hr later, a tsunami was clearly recorded on King Edward Point coastal tide gauge (South Georgia Island), approximately 800 km north‐west of the earthquake location. Subsequently it was recorded on other coastal stations both in the Atlantic Ocean, and also in the Indian and Pacific Oceans. A careful and systematic analysis of coastal and deepwater sea‐level records highlights three points: (a) the tsunami propagated across four oceans following major submarine features; (b) despite its very low amplitude, it reached as far as the Canary Islands in the Atlantic Ocean, Hawaii and the US West coast as far as Alaska and the Aleutian Islands in the Pacific Ocean; (c) it was recorded twice on New Zealand DART system NZC, with one record of the tsunami from the East and one from the West. This event is an opportunity to highlight the lack of knowledge about the South Sandwich subduction region in terms of its tsunamigenic potential and the associated tsunami hazard in the Pacific ocean. It should lead to an improvement of national tsunami warning procedures, by including this region as a tsunami source zone, for neighboring regions but also for distant countries like New Zealand or French Polynesia.

While presenting similar properties, the Hi‐Nicalon Type S (HNS) and Tyranno SA3 (TSA3) SiC fibers exhibit different mechanical behaviors when used as reinforcement in SiC/SiC composites. Indeed, the HNS‐reinforced composites exhibit a pseudoductile mechanical behavior whereas the TSA3‐based composites show low ductility. Even though the differences in their grain size and surface roughness could explain a part of this phenomenon, the chemical composition and microstructure of the fibers outermost surface play a key role. The recent availability of the new Tyranno SA4 (TSA4) SiC fiber allowed the processing of composites showing the expected pseudoductile mechanical behavior in ceramic matrix composites, even without an interphase. Therefore, this result shows that the TSA4 surface should be different from its predecessors. In order to characterize the surface, X‐ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), and transmission electron microscopy (TEM) were performed on the HNS, TSA3, and TSA4 fibers. The presence of an organized boron nitride layer of dozens of nanometers in thickness on the TSA4 fiber surface was evidenced. This layer already acts as an interphase material, guaranteeing cracks deflection, and is responsible for the pseudoductile behavior of composites made of this new fiber, reducing the interfacial shear stress at the fiber/matrix interface.

Self-shielding effects of micrometric particles randomly distributed in nuclear materials were the subject of extensive studies. These effects are known as a double-heterogeneity problem due to “microscopic” heterogeneities, involving the decrease of the neutron flux inside the particles, and “macroscopic” heterogeneities, affecting the neutron flux distribution over the entire volume containing those particles. The present study aims to take advantage of the capabilities of the GELINA facility (JRC-Geel, Belgium) in terms of non-destructive analysis of materials to validate experimentally any models developed to solve the double heterogeneity problem. In order to complement past experiments carried out at the GELINA facility, new transmission experiments were carried out on long cylindrical samples containing microspheres of Gd2O3 with diameters of 195 and 380 μm dispersed in UO2 pellets. The analysis of the experimental transmission spectra with the resonance shape analysis code REFIT and Monte-Carlo neutron transport code TRIPOLI-4® demonstrates that the particle self-shielding model proposed by Doub can reproduce the huge attenuation of the neutron absorption in the Gd resonances by reducing significantly the computational cost of Monte-Carlo simulations.

We present multiple derivations of the Total Radiation Belt Electron Content (TRBEC), an indicator of the global number of electrons that instantaneously occupy the radiation belts. Derived from electron flux measurements, the TRBEC reduces the spatial information into a scalar quantity that concisely describes global aspects of the system. This index provides a simple, global, and long‐term assessment of the radiation belts that enables systematic analysis. In this work, we examine the TRBEC using the adiabatic invariants of μ,K,L∗ $\left(\mu ,K,{L}^{\ast }\right)$ which has been used in previous articles as this coordinate system removes reversible adiabatic effects. We then introduce a new expression to compute the TRBEC using the non‐adiabatic coordinates of E,αeq,L∗ $\left(E,{\alpha }_{eq},{L}^{\ast }\right)$, relevant in the contexts of energetic electron precipitation, chorus, and hiss scattering where adiabatic invariant quantities are no longer conserved. From both expressions of the TRBEC we demonstrate that an erroneous factor of (2π)3 ${(2\pi )}^{3}$ that appeared in previous works using the adiabatic derivation led to an overestimate of the reported electron populations. In addition, we quantify electron loss in the outer radiation belt 3.5<L∗<5 $\left(3.5< {L}^{\ast }< 5\right)$ via a case study using the Van Allen Probes data over a 20‐day period from March 2013 specifying particle populations both in terms of the aforementioned adiabatic and non‐adiabatic variables. The total number of electrons in the outer radiation belt reached upwards of 1028 $1{0}^{28}$ electrons at the peak of the storm, a rest mass of roughly 10 g.

Giant Resonances are, with nuclear rotations, the most evident expression of collectivity in finite nuclei. These two categories of excitations, however, are traditionally described within different formal schemes, such that vibrational and rotational degrees of freedom are separately treated and coupling effects between those are often neglected. The present work puts forward an approach aiming at a consistent treatment of vibrations and rotations. Specifically, this paper is the last in a series of four dedicated to the investigation of the giant monopole resonance in doubly open-shell nuclei via the ab initio Projected Generator Coordinate Method (PGCM). The present focus is on the treatment and impact of angular momentum restoration within such calculations. The PGCM being based on the use of deformed mean-field states, the angular-momentum restoration is performed when solving the secular equation to extract vibrational excitations. In this context, it is shown that performing the angular momentum restoration only after solving the secular equation contaminates the monopole response with an unphysical coupling to the rotational motion, as was also shown recently for (quasi-particle) random phase approximation calculations based on a deformed reference state. Eventually, the present work based on the PGCM confirms that an a priori angular momentum restoration is necessary to handle consistently both collective motions at the same time. This further pleads in favor of implementing the full-fledged projected (quasi-particle) random phase approximation in the future.

The formation constants of Ca n UO 2 (CO 3 ) 3 (4–2n)– complexes have been determined directly using capillary electrophoresis coupled with inductively coupled plasma mass spectrometry (CE-ICP-MS) in 0.1 M NaCl and at room temperature. Instead...

Neutron activation dosimetry is the primary method for the determination of the neutron flux or fluence, and in general, it is sensitive to the thermal and resonance energy ranges (radiative capture reactions–$(n,\gamma )$ reactions) and the fast energy range (threshold reactions). However, there are very few nuclear reactions which are sensitive specifically to neutrons in the intermediate–epithermal–energy region. This energy region, along with the fast energy range, will become particularly important in the development and deployment of new reactor technologies (Generation IV reactors and Small Modular Reactors–SMRs), which are currently being championed as technologies enabling a meaningful contribution to decarbonization and the fight against climate change, as well as nuclear fusion. The epithermal neutron energy range is also of particular importance for Boron Neutron Capture Therapy (BNCT), a neutron-based cancer therapy, particularly effective for the treatment of head and neck cancer, malignant meningioma, melanoma and hepatocellular carcinoma. This work investigates and demonstrates the applicability of a particular set of $(n,\gamma )$ reactions in conjunction with boron-based neutron filters to achieve sensitivity in the epithermal energy region, and discusses avenues for future research in this context.

Using GPU-accelerated state-vector emulation, we propose to embed a quantum computing ansatz into density-functional theory via density-based basis-set corrections to obtain quantitative quantum-chemistry results on molecules that would otherwise require brute-force quantum calculations using hundreds of logical qubits. Indeed, accessing a quantitative description of chemical systems while minimizing quantum resources is an essential challenge given the limited qubit capabilities of current quantum processors. We provide a shortcut towards chemically accurate quantum computations by approaching the complete-basis-set limit through coupling the density-based basis-set corrections approach, applied to any given variational ansatz, to an on-the-fly crafting of basis sets specifically adapted to a given system and user-defined qubit budget. The resulting approach self-consistently accelerates the basis-set convergence, improving electronic densities, ground-state energies, and first-order properties (e.g. dipole moments), but can also serve as a classical, a posteriori, energy correction to quantum hardware calculations with expected applications in drug design and materials science.

This paper describes PyGyro, a parallel 4D drift-kinetic code which implements backward semi-Lagrangian methods combined with field-aligned interpolation and time-splitting. The purpose of PyGyro is twofold: to develop an advanced parallelisation scheme based on fast data transpositions, and to demonstrate the efficacy of a development workflow with code written in Python. Bottlenecks are accelerated with the Pyccel transpiler to achieve Fortran-like execution times. The resulting simulations are shown to correctly reproduce the expected physics and demonstrate good strong scaling, well beyond what was achieved by an existing Fortran code.

In this work we focus on an adaptation of the method described in [1] in order to deal with source term in the 2D Euler equations. This method extends classical 1D solvers (such as VFFC, Roe, Rusanov) to the two-dimensional case on unstructured meshes. The resulting schemes are said to be composite as they can be written as a convex combination of a purely node-based scheme and a purely edge-based scheme. We combine this extension with the ideas developed by Alouges, Ghidaglia and Tajchman in an unpublished work [2] – focused mainly on the 1D case – and we propose two attempts at discretizing the source term of the Euler equations in order to better preserve stationary solutions. We compare these discretizations with the “usual” centered discretization on several numerical examples.

Underground nuclear explosions (UNEs) can generate significant air flow that carry, in addition to the radionuclides produced by the explosion, naturally occurring tracers initially present in the surrounding rock or the overlying soil layer. Here we show that these tracers, observed not only at the monitoring sites but also at the test site, could be used to improve the monitoring of the radionuclides used to detect UNEs, which can be hampered by several factors. We first developed a model for non-isothermal single-phase flow, heat and mass transfer, and tracer transport through fractured porous media. Using the conditions relevant for the Punggye-ri site in North Korea as an example, we provide estimates for the emission of water vapor and $\hbox {CO}_2$ at the test site, and for the emission of radon and radioxenon at the test site and at the Takasaki monitoring site in Japan. The influence of geological conditions is investigated. For a given monitoring station, it is possible to improve the detection of radioxenon from an underground nuclear explosion by detecting, shortly in advance, the emission of water vapor at the nuclear test site using satellite imagery. If $\hbox {CO}_2$ is contributed only from the soil layer and is then scavenged by the gas seeping from a UNE, it cannot be detected by satellite imagery. Radon cannot be detected at the monitoring site, although this gas species is contributed from everywhere by the rock medium, including the rock vaporized to form the cavity.

Translocator protein (TSPO) is a mitochondrial protein expressed by microglia, ligands for which are used as a marker of neuroinflammation in PET studies of Alzheimer’s disease (AD). We previously showed increasing TSPO load in the cerebral cortex with AD progression, consistent with TSPO PET scan findings. Here, we aim to characterise the microglial phenotype associated with TSPO expression to aid interpretation of the signal generated by TSPO ligands in patients. Human post-mortem sections of temporal lobe (TL) and cerebellum (Cb) from cases classified by Braak group (0–II, III–IV, V–VI; each n = 10) were fluorescently double labelled for TSPO and microglial markers: Iba1, HLA-DR, CD68, MSR-A and CD64. Quantification was performed on scanned images using QuPath software to assess the microglial phenotype of TSPO. Qualitative analysis was also performed for TSPO with GFAP (astrocytes), CD31 (endothelial cells) and CD163 (perivascular macrophages) to characterise the cellular profile of TSPO. The percentage of CD68⁺TSPO⁺ double-labelled cells was significantly higher than for other microglial markers in both brain regions and in all Braak stages, followed by MSR-A⁺TSPO⁺ microglia. Iba1⁺TSPO⁺ cells were more numerous in the cerebellum than the temporal lobe, while CD64⁺TSPO⁺ cells were more numerous in the temporal lobe. No differences were observed for the other microglial markers. TSPO expression was also detected in endothelial cells, but not detected in astrocytes nor in perivascular macrophages. Our data suggest that TSPO is mainly related to a phagocytic profile of microglia (CD68⁺) in human AD, potentially highlighting the ongoing neurodegeneration.

The study of fission yields has a major impact on the characterization and understanding of the fission process and its applications. Mass yield evaluation represents a key element in order to perform the best estimation of independent and cumulative fission product yields. Today, the lack of analysis-based correlation matrix between the different fission observables induces many inconsistencies in the evaluations. In particular, the mass yield uncertainties are drastically overestimated in comparison to chain yields while these two quantities only differ from the emission of delayed neutrons. In this work, a new consistent process of mass yield evaluation is proposed taking into account the description of the covariance matrix. For $^{235}\text {U(n}_{\text {th}}\text {,f)}$ 235 U(n th ,f) mass yields, existing data cover a large range of produced masses which makes it possible to propose an evaluation of mass yields independently of any model with a precision closed to $1.5\%$ 1.5 % for the high yields. This new precision brings the possibility to discuss the origin of the structures in the post-neutron mass yields, in particular the consistency with the pre-neutron mass yields and the prompt neutron multiplicity per mass. The work is the first part of the $^{235}\text {U(n}_{\text {th}}\text {,f)}$ 235 U(n th ,f) thermal neutron induced fission yield evaluation which will be included in the new JEFF-4 library.

CEA/Cadarache operates the MADERE facility dedicated to measuring the activity of radionuclides generated during the irradiation of specific dosimeters made of hyper-pure materials. This facility is equipped with seven spectrometers, two of which are dedicated to the detection of radionuclides that emit X-rays. The laboratory that operates the MADERE facility processes solid-state rhodium and niobium dosimeters, which emit X-rays of 20 keV and 16 keV respectively. In recent years, there have been significant improvements in nuclear decay data, leading to better measurement of these two X-ray emitters. A joint LDCI and LNHB thesis, defended in 2018, produced major advances (for example self-attenuation corrections for 93mNb and 103mRh). The most significant achievements and outlooks are presented in this paper for the both niobium and rhodium dosimeters.

The epithermal to fast neutron domain lacks reactions to enhance the knowledge of spectrum in this energy range (1 keV to 1 MeV). Previous studies on this topic focused on ⁹⁴Zr(n, γ) capture and ¹¹⁷Sn(n, n′) inelastic reactions. In the framework of a research collaboration between the French Atomic and Alternative Energies Commission (CEA) and the Jožef Stefan Institute (JSI), a new project consists in finding new inelastic reactions suitable for dosimetry. This paper describes the selection process of new reactions to be tested in an experimental campaign at JSI.

Since 1981, the French Alternative Energies and Atomic Energy Commission has been measuring the dosimeters of the surveillance capsules of the French pressurized water reactors and assessing their neutron fluence. This represents more than 250 surveillance PWR capsules, i.e. 4 thousands dosimeters. Started in Grenoble, this work continued in Cadarache with the creation of the “Measurement Applied to DosimEtry in Reactors” (MADERE) platform within the Dosimetry, Sensors and Instrumentation Laboratory (LDCI). Since 1998, all surveillance dosimeters measurements (i.e. Al-Co, ²³⁸U, ²³⁷Np, Ni, Cu, Fe and Nb) have been performed at MADERE under the “Cofrac Essais” accreditation according to the ISO/IEC 17025 international standard. The evolution over time of the 1σ measurement uncertainty of the activity of each is presented in this paper. Since 2015, they are [±1.3% ; ±2.9%] for ²³⁸U with Ni encapsulation, [±0.8% ; ±2.1%] for ²³⁸U with Ti encapsulation, [±1.2% ; ±4.9%] for ²³⁸U with stainless steel encapsulation, ±1.3% for ²³⁷Np dosimeters, ±1.2% for Al-Co, [±1.2% ; ±1.4%] for nickel, copper and iron, [±3.3%; ±3.9%] for niobium if unbroken after irradiation.

Recently, the control of dynamic chirality has emerged as a powerful strategy to design chiral functional materials. In this context, we describe herein a molecular design in which a tethered configurationally stable binaphthyl chiral unit efficiently controls the dynamic chirality of donor‐acceptor fluorophores, involving diverse indolocarbazoles as electron donors and terephthalonitrile as an electron acceptor. The high conformational discrimination in such a molecular system suggested by density functional theory calculations is experimentally probed using electronic and vibrational circular dichroism and confirmed by the crystallization of these chiral molecules in gel and their single crystal X‐ray diffraction analysis. This work also highlights the positive effect of the configurationally stable chiral unit on the magnitude of the dissymmetry factors of the active dynamically chiral fluorophores, both in ground and excited states, through chiral perturbation.