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Synthesis of bicyclo[4.2.0]octane ring of kingianin via [2+2] ketene cycloaddition
No full textInternational audienc
Advanced Laser–Plasma Diagnostics for a Modular High-Repetition-Rate Plasma Electron Accelerator
No full textInternational audienceWe present a laser–plasma electron accelerator module designed to be driven by high-repetition-rate lasers for industrial applications of laser-driven electron beams. It consists of a single vacuum chamber containing all the necessary components for producing, optimizing, and monitoring electron beams generated via laser wakefield acceleration in a gas jet when driven by a suitable laser. The core methods in this paper involve a comprehensive metrological assessment of the driving laser by rigorous temporal laser pulse characterization and contrast measurements, supplemented by detailed spatiotemporal distribution analyses of the laser focus. Results demonstrate the good stability and reproducibility of the laser system, confirming its suitability for advanced scientific and industrial applications. We further demonstrate the functionality of the laser–plasma accelerator module diagnostics, perform target density characterizations, and time-resolved laser–plasma shadowgraphy. Current limitations of the set-up preventing first electron acceleration are analyzed and an outlook for future experiments is given. Our work is a first step towards the wide dissemination of fully integrated laser–plasma accelerator technology
ARCH-COMP24 Category Report: Continuous and Hybrid Systems with Nonlinear Dynamics
No full textInternational audienceWe present the results of a friendly competition for formal verification of continuous and hybrid systems with nonlinear continuous dynamics. The friendly competition took place as part of the workshop Applied Verification for Continuous and Hybrid Systems (ARCH) in 2024. This year, 5 tools participated: Ariadne, CORA, DynIbex, JuliaReach and KeYmaera X (in alphabetic order). These tools are applied to solve reachability analysis problems on six benchmark problems, two of them featuring hybrid dynamics. We do not rank the tools based on the results, but show the current status and discover the potential advantages of different tools
Guaranteed Satisfaction of a Temporal Logic Formula with a Confidence Parameter
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T-coercivité et problèmes mixtes
No full textInternational audienceClassically, the well-posedness of variational formulations of mixed linear problems is achieved through the inf-sup condition on the constraint. In this note, we propose an alternative framework to study such problems by using the T-coercivity approach to derive a global inf-sup condition. Generally speaking, this is a constructive approach that, in addition, drives the design of suitable approximations. As a matter of fact, the derivation of the uniform discrete inf-sup condition for the approximate problems follows easily from the study of the original problem. To support our view, we solve a series of classical mixed problems with the T-coercivity approach. Among others, the celebrated Fortin Lemma appears naturally in the numerical analysis of the approximate problems.Classiquement, le caractère bien posé des formulations variationnelles de problèmes linéaires mixtes est obtenu à l'aide de la condition inf-sup. Dans cette note, nous proposons un cadre alternatif pour étudier de tels problèmes en utilisant la notion de T-coercivité. Il s'agit d'une approche constructive qui permet en outre de concevoir simplement des approximations numériques adaptées car la dérivation de la condition inf-sup discrète uniforme découle en général directement de l'étude du problème continu. Pour appuyer notre propos, nous résolvons une série de problèmes mixtes classiques grâce à la notion de T-coercivité. Entre autres, le lemme de Fortin apparaît naturellement dans l'analyse numérique des problèmes discrets
Secularizing the Unsecularizable
No full textThis video for the Space Commons conference explores the notion that the moon, and even the space commons in general, has been disenchanted to the benefit of the Earth. The overall argument is not that this is a good thing-- which is to say that we now love the Earth but we hate space-- but rather that the Moon, in becoming disenchanted, has become a pure resource, exploitable without compunctions. It is against this absolute exploitability that this video attempts to take up a position, exploring ways in which the Lunar Heritage might once again be grasped as being sacred, out of the reach of astrocapitalism and extraterrestrial extractivism
A finite volume method to solve the Poisson equation with jump conditions and surface charges: Application to electroporation
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MAP-IO: an atmospheric and marine observatory program on board Marion Dufresne over the Southern Ocean
No full textInternational audienceThis article is devoted to the presentation of the MAP-IO observation program. This program, launched in early 2021, has enabled the observation of nearly 700 d of measurements over the Indian and Southern Ocean with the equipment of 17 meteorological and oceanographic scientific instruments on board the ship Marion Dufresne. Several observational techniques have been developed to respond to the difficulties of observations on board the ship, in particular for passive remote sensing data, as well as for quasi-autonomous data acquisition and transfer. The first measurements made it possible to draw up unprecedented climatological data of the Southern Ocean regarding the size distribution and optical thickness of aerosols, the concentration of trace gases and greenhouse gases, UV, and integrated water vapor
Miroirs plasmas relativistes contrôlés par des ondes lumineuses
No full textInternational audienceWe report on attosecond-scale control of high-harmonic and fast electron emission from plasma mirrors driven by relativistic-intensity near-single-cycle light waves at a kHz repetition rate. By controlling the waveform of the intense light transient, we reproducibly form a sub-cycle temporal intensity gate at the plasma mirror surface, leading to the observation of extreme ultraviolet spectral continua, characteristic of isolated attosecond pulse (IAP) generation. We also observe the correlated emission of a waveform-dependent relativistic electron beam, paving the way toward fully lightwave-controlled dynamics of relativistic plasma mirrors.Nous décrivons le contrôle à l'échelle de l'attoseconde de l'émission d'harmoniques élevées et d'électrons rapides à partir de miroirs de plasma pilotés par des ondes lumineuses d'intensité relativiste à cycle unique à une cadence de 1 kHz. En contrôlant la forme d'onde du transitoire de lumière intense, nous formons de manière reproductible une porte temporelle d'intensité sous-cycle à la surface du miroir de plasma, ce qui permet d'observer des continuums spectraux dans l'ultraviolet extrême, caractéristiques de la génération d'impulsions attosecondes isolées. Nous observons également l'émission corrélée d'un faisceau d'électrons relativistes dépendant de la forme d'onde, ce qui ouvre la voie à une dynamique des miroirs de plasma relativistes entièrement contrôlée par les ondes lumineuses
Fluorescence and lasing of neutral nitrogen molecules inside femtosecond laser filaments in air: mechanism and applications
No full textInternational audienceHigh power femtosecond laser pulses launched in air undergo nonlinear filamentary propagation, featuring a bright and thin plasma channel in air with its length much longer than the Rayleigh length of the laser beam. During this nonlinear propagation process, the laser pulses experience rich and complex spatial and temporal transformations. With its applications ranging from supercontinuum generation, laser pulse compression, remote sensing to triggering of lightning, the underlying physical mechanism of filamentation has been intensively studies. In this review, we will focus on the fluorescence and cavity-free lasing effect of the plasma filaments in air. The different mechanisms underlying the fluorescence of the excited neutral nitrogen molecules will be throughtly examined and it is concluded that the electron collision excitation is the dominant channel for the formation of the excited nitrogen molecules. The recently discovered “air lasing” effect, a cavity-free bidirectional lasing emission emitted by the filaments, will be introduced and its main properties will be emphasized. The applications of the fluorescence and lasing effect of the neutral nitrogen molecules will be introduced, with two examples on spectroscopy and detection of electric field. Finally, we discuss the quenching effect of the lasing effect in atmosphere and the mechanisms responsible will be analyzed. An outlook for the achievement of backward lasing in air will be briefly presented