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Matter and Radiation at Extremes 2023年第2期8卷 33-46页

作者： C.Ruyer P.Loiseau G.Riazuelo R.Riquier A.Debayle P.E.Masson-Laborde O.Morice cea DAMDIFF-91297 ArpajonFrance cea LMCEUniversitéParis-Saclay91680 Bruyères-le-ChâtelFrance

We propose a semi-analytical modeling of smoothed laser beam deviation induced by plasma *** on a Gaussian description of speckles,the model includes spatial,temporal,and polarization smoothing techniques,through fits coming from hydrodynamic simulations with a paraxial description of electromagnetic *** beam bending model is then incorporated into a ray tracing algorithm and carefully *** applied as a post-process to the propagation of the inner cone in a full-scale simulation of a National Ignition Facility(NIF)experiment,the beam bending along the path of the laser affects the refraction conditions inside the hohlraum and the energy deposition,and could explain some anomalous refraction measurements,namely,the so-called glint observed in some NIF experiments.

关键词： polarization beam bending

Approximation Properties of Vectorial Exponential Functions

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Communications on Applied Mathematics and Computation 2024年第3期6卷 1801-1831页

作者： Christophe Buet Bruno Despres Guillaume Morel cea DAMDIF91297 ArpajonFrance Laboratoire en Informatique Haute Performance Pour le Calcul et la Simulation CEAUniversitéParis-Saclay91680 Bruyeres-le-ChatelFrance Laboratoire Jacques-Louis Lions UMR 7598Sorbonne Universite75005 ParisFrance IMT Atlantique 29238 BrestFrance

This contribution is dedicated to the celebration of Rémi Abgrall’s accomplishments in Applied Mathematics and Scientific Computing during the conference“Essentially Hyperbolic Problems:Unconventional Numerics,and Applications”.With respect to classical Finite Elements Methods,Trefftz methods are unconventional methods because of the way the basis functions are *** discontinuous Galerkin(TDG)methods have recently shown potential for numerical approximation of transport equations[6,26]with vectorial exponential *** paper focuses on a proof of the approximation properties of these exponential *** show that vectorial exponential functions can achieve high order *** fundamental part of the proof consists in proving that a certain rectangular matrix has maximal rank.

关键词： Trefftz method Transport equation Vectorial exponential functions

Measurements of Absolute Atomic Nitrogen Density by Two-Photon Absorption Laser-Induced Fluorescence Spectroscopy in Hot Air Plasma Generated by Microwave Resonant Cavity

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Journal of Analytical Sciences, Methods and Instrumentation 2017年第4期7卷 93-115页

作者： Frédéric Marchal Nofel Merbahi Gaétan Wattieaux Alain Piquemal Mohammed Yousfi Université de Toulouse LAPLACE UPS CNRS INPT Toulouse France cea DAM DIF Arpajon France

For the first time, absolute densities of atomic nitrogen in its ground state (N4S) have been measured in hot dry and humid air plasma columns under post-discharge regime. The determination of space-resolved absolute densities leads to obtain the dissociation degrees of molecular nitrogen in the plasma. The hot plasmas are generated inside an upstream gas-conditioning cell at 600 mbar when the air gas flow is directly injected at 10 slm in a microwave resonant cavity (2.45 GHz, 1 kW) placed in the downstream side. Density measurements based on laser induced fluorescence spectroscopy with two-photon excitation (TALIF), are more particularly performed along the radial and axial positions of the plasma column. Calibration of TALIF signals is performed in situ (i.e. in the same gas-conditioning cell but without plasma) using an air gas mixture containing krypton. Optical emission spectroscopy is considered to estimate the rotational gas temperature by adding a small amount of H2 in dry air to better detect OH (A-X) spectra. The rotational temperatures in humid air plasma column (50% of humidity) are larger than those of dry air plasma column by practically 30% near the nozzle of resonant cavity on the axis of the plasma column. This is partly due to attachment heating processes initiated by water vapor. A maximum of the measured absolute nitrogen density is also observed near the nozzle which is also larger for humid air plasma column. The obtained dissociation degrees of molecular nitrogen in both dry and humid air plasma along the air plasma column are lower than the cases where only thermodynamic equilibrium is assumed. This is characteristic of the absence of chemical and energetic equilibria not yet reached in the air plasma column dominated by recombination processes.

关键词： TALIF Atomic Nitrogen Density Measurement Hot Air Plasma Optical Emission Spectroscopy

Experimental measurements of gamma-photon production and estimation of electron/positron production on the PETAL laser facility

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Matter and Radiation at Extremes 2024年第5期9卷 32-47页

作者： F.Brun L.Ribotte G.Boutoux X.Davoine P.E.Masson-Laborde Y.Sentoku N.Iwata N.Blanchot D.Batani I.Lantuéjoul L.Lecherbourg B.Rosse C.Rousseaux B.Vauzour D.Raffestin E.D’Humières X.Ribeyre Centre Lasers Intenses et Applications UMR 5107Universitéde Bordeaux-CNRS-CEA33405 TalenceFrance cea DAMCESTAF-33116 Le BarpFrance cea DAMDIFF-91297 ArpajonFrance cea LMCEUniversitéParis-Saclay91680 Bruyères-le-ChâtelFrance Institute of Laser Engineering Osaka University2-6 YamadaokaSuitaOsaka 565-0871Japan

This article reports the first measurements of high-energy photons produced with the high-intensity PETawatt Aquitaine Laser(PETAL)*** experiments were performed during the commissioning of the *** laser had an energy of about 400 J,an intensity of 8×10^(18)W cm^(−2),and a pulse duration of 660 fs(FWHM).It was shot at a 2 mm-thick solid tungsten *** high-energy photons were produced mainly from the bremsstrahlung process for relativistic electrons accelerated inside a plasma generated on the front side of the *** paper reports measurements of electrons,protons and *** electrons up to35 MeV with a few-MeV temperature were recorded by a spectrometer,called SESAME(SpectreÉlectronS Angulaire MoyenneÉnergie).K-and L-shells were clearly detected by a photon spectrometer called SPECTIX(Spectromètre PetalàCristal en TransmIssion pour le rayonnnement X).High-energy photons were diagnosed by CRACC-X(Cassette de RAdiographie Centre Chambre-rayonnement X),a bremsstrahlung *** cannon analysis is strongly dependent on the hypothesis adopted for the spectral *** shapes can exhibit similar reproductions of the experimental *** eliminate dependence on the shape hypothesis and to facilitate analysis of the data,simulations of the interaction were *** model the mechanisms involved,a simulation chain including hydrodynamic,particle-in-cell,and Monte Carlo simulations was *** simulations model the preplasma generated at the front of the target by the PETAL laser prepulse,the acceleration of electrons inside the plasma,the generation of MeV-range photons from these electrons,and the response of the detector impacted by the energetic photon *** this work enabled reproduction of the experimental *** high-energy photons produced have a large emission angle and an exponential distribution *** addition to the analysis of the photon spectra,positron production was also ***,if high

关键词： process positron hypothesis

Adaptive Bayesian Inference for Discontinuous Inverse Problems,Application to Hyperbolic Conservation Laws

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Communications in Computational Physics 2014年第6期16卷 1-34页

作者： Alexandre Birolleau Gaël Poëtte Didier Lucor cea DAMDIFF-91297 ArpajonFrance. UPMC Univ Paris 06 UMR 7190Institut Jean Le Rond d’AlembertF-75005 ParisFrance. CNRS UMR 7190Institut Jean Le Rond d’AlembertF-75005 ParisFrance.

Various works from the literature aimed at accelerating Bayesian inference in inverse *** spectral methods have been recently proposed as surrogate approximations of the forward uncertainty propagation model over the support of the prior *** representations are efficient because they allow affordable simulation of a large number of samples from the posterior ***,they do not perform well when the forward model exhibits strong nonlinear behavior with respect to its *** this work,we first relate the fast(exponential)L2-convergence of the forward approximation to the fast(exponential)convergence(in terms of Kullback-Leibler divergence)of the approximate *** particular,we prove that in case the prior distribution is uniform,the posterior is at least twice as fast as the convergence rate of the forward model in those *** Bayesian inference strategy is developed in the framework of a stochastic spectral projection *** predicted convergence rates are then demonstrated for simple nonlinear inverse problems of varying *** then propose an efficient numerical approach for the Bayesian solution of inverse problems presenting strongly nonlinear or discontinuous system *** comes with the improvement of the forward model that is adaptively approximated by an iterative generalized Polynomial Chaos-based *** numerical approximations and predicted convergence rates of the former approach are compared to the new iterative numerical method for nonlinear time-dependent test cases of varying dimension and complexity,which are relevant regarding our hydrodynamics motivations and therefore regarding hyperbolic conservation laws and the apparition of discontinuities in finite time.

关键词： Stochastic inverse problems Bayesian inference iterative generalized Polynomial Chaos compressible gas dynamics.

Enhanced ion acceleration using the high-energy petawatt PETAL laser

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Matter and Radiation at Extremes 2021年第5期6卷 62-79页

作者： D.Raffestin L.Lecherbourg I.Lantúejoul B.Vauzour P.E.Masson-Laborde X.Davoine N.Blanchot J.L.Dubois X.Vaisseau E.d’Humières L.Gremillet A.Duval Ch.Reverdin B.Rosse G.Boutoux J.E.Ducret Ch.Rousseaux V.Tikhonchuk D.Batani cea DAMCESTAF-33116 Le BarpFrance Centre Laser Intenses et Applications Universit´e de Bordeaux-CNRS-CEAUMR 510733405 TalenceFrance cea DAMDIFF-91297 ArpajonFrance Universit´e Paris-Saclay CEALMCE91680 Bruy`eres-le-ChˆatelFrance cea DRFIRFUGANILF-14000 CaenFrance ELI-Beamlines Research Centre 25241 DolníBrezanyCzech Republic

The high-energy petawatt PETAL laser system was commissioned at cea’s Laser M´egajoule facility during the 2017–2018 *** paper reports in detail on the first experimental results obtained at PETAL on energetic particle and photon generation from solid foil targets,with special emphasis on proton *** a moderately relativistic(<1019 W/cm^(2))laser intensity,proton energies as high as 51 MeV have been measured significantly above those expected from preliminary numerical simulations using idealized interaction *** hydrodynamic and kinetic simulations,taking into account the actual laser parameters,show the importance of the energetic electron production in the extended low-density preplasma created by the laser *** hot-electron generation occurs through two main pathways:(i)stimulated backscattering of the incoming laser light,triggering stochastic electron heating in the resulting counterpropagating laser beams;(ii)laser filamentation,leading to local intensifications of the laser field and plasma channeling,both of which tend to boost the electron ***,owing to the large(∼100μm)waist and picosecond duration of the PETAL beam,the hot electrons can sustain a high electrostatic field at the target rear side for an extended period,thus enabling efficient target normal sheath acceleration of the rear-side *** particle distributions predicted by our numerical simulations are consistent with the measurements.

关键词： acceleration high energy

Spectral Properties of an Energy-Dependent Hamiltonian

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Communications in Mathematical Research 2021年第2期37卷 141-179页

作者： Pierre Chau Huu-Tai Bernard Ducomet cea DAMDIFF-91297 ArpajonFrance.2 Universite Paris-EstLAMA(UMR 805)UPEMLVUPECCNRS61 Avenue du General de GaulleF-94010 CreteilFrance

We study spectral properties of a quantum Hamiltonian with a complex-valued energy-dependent potential related to a model introduced in physics of nuclear reactions[30]and we prove that the principle of limiting absorption holds at any point of a large subset of the essential *** an additional dissipative or smallness hypothesis is assumed on the potential,we show that the principle of limiting absorption holds at any point of the essential spectrum.

关键词： Non-selfadjoint complex potentia dissipative limiting absorption principle spectral singularity energy dependent potential

Short-pulse laser-driven x-ray radiography

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High Power Laser Science and Engineering 2016年第3期4卷 101-105页

作者： E.Brambrink S.Baton M.Koenig R.Yurchak N.Bidaut B.Albertazzi J.E.Cross G.Gregori A.Rigby E.Falize A.Pelka F.Kroll S.Pikuz Y.Sakawa N.Ozaki C.Kuranz M.Manuel C.Li P.Tzeferacos D.Lamb LULI-CNRS Ecole PolytechniqueCEA Universit Paris-Saclay UPMC Univ Paris 06 Sorbonne Universits Institute for Academic Initiatives Osaka U. Clarendon Laboratory University of Oxford cea-dam-dif HZDR JIHT-RAS Institute of Laser Engineering Osaka U. Graduate School of Engineering Osaka U. Department of Energy Engineering Science Faculty of Engineering SciencesKyushu University Plasma Science and Fusion Center Massachusetts Institute of Technology Flash Center for Computational Science University of Chicago

We have developed a new radiography setup with a short-pulse laser-driven x-ray source. Using a radiography axis perpendicular to both long- and short-pulse lasers allowed optimizing the incident angle of the short-pulse laser on the x-ray source target. The setup has been tested with various x-ray source target materials and different laser *** to noise ratios are presented as well as achieved spatial resolutions. The high quality of our technique is illustrated on a plasma flow radiograph obtained during a laboratory astrophysics experiment on POLARs.

关键词： laboratory astrophysics short-pulse laser x-ray radiography

Target fabrication for the POLAR experiment on the Orion laser facility

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High Power Laser Science and Engineering 2015年第1期3卷 70-75页

作者： C.Spindloe D.Wyatt D.Haddock I.East J.E.Cross C.N.Danson E.Falize J.M.Foster M.Koenig G.Gregori Target Fabrication Group Central Laser Facility Rutherford Appleton Laboratory Harwell Science and Innovation Campus Atomic and Laser Physics Clarendon Laboratory University of Oxford AWE cea-dam-dif Laboratoire pour l’Utilisation Des Laser Intense UMR 7605 CNRS-CEA-Ecole Polytechnique-Université Paris VI

This article describes the fabrication of a suite of laser targets by the Target Fabrication group in the Central Laser Facility(CLF), STFC Rutherford Appleton Laboratory for the first academic-access experiment on the Orion laser facility(Hopps et al., Appl. Opt. 52, 3597–3601(2013)) at Atomic Weapons Establishment(AWE). This experiment, part of the POLAR project(Falize et al., Astrophys. Space Sci. 336, 81–85(2011); Busschaert et al., New J. Phys. 15, 035020(2013)),studied conditions relevant to the radiation-hydrodynamic processes occurring in a remarkable class of astrophysical star systems known as magnetic cataclysmic variables. A large number of complex fabrication technologies and research and development activities were required to field a total of 80 high-specification targets. Target design and fabrication procedures are described and initial alignment and characterization data are discussed.

关键词： astrophysics microtargets

Data-driven magneto-elastic predictions with scalable classical spin-lattice dynamics

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npj Computational Materials 2021年第1期7卷 1414-1425页

作者： Svetoslav Nikolov Mitchell AWood Attila Cangi Jean-Bernard Maillet Mihai-Cosmin Marinica Aidan PThompson Michael P.Desjarlais Julien Tranchida Computational Multiscale Department Sandia National LaboratoriesP.O.Box 5800MS 1322AlbuquerqueNM 87185USA Center for Advanced Systems Understanding(CASUS) D-02826 GörlitzGermany Helmholtz-Zentrum Dresden-Rossendorf D-01328 DresdenGermany cea-dam DIFArpajon Cedex F-91297France UniversitéParis-Saclay CEALMCE91680 Bruyères-le-ChâtelFrance UniversitéParis-Saclay CEAService de Recherches de Métallurgie PhysiqueGif-sur-Yvette 91191France Sandia National Laboratories P.O.Box 5800MS 1322AlbuquerqueNM 87185USA

A data-driven framework is presented for building magneto-elastic machine-learning interatomic potentials(ML-IAPs)for largescale spin-lattice dynamics *** magneto-elastic ML-IAPs are constructed by coupling a collective atomic spin model with an *** they represent a potential energy surface from which the mechanical forces on the atoms and the precession dynamics of the atomic spins are *** the atomic spin model and the ML-IAP are parametrized on data from first-principles *** demonstrate the efficacy of our data-driven framework across magneto-structural phase transitions by generating a magneto-elastic ML-IAP forα-*** combined potential energy surface yields excellent agreement with firstprinciples magneto-elastic calculations and quantitative predictions of diverse materials properties including bulk modulus,magnetization,and specific heat across the ferromagnetic–paramagnetic phase transition.

关键词： transition dynamics magneto