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Quantitative Determination of Density of Ground State Atomic Oxygen from Both TALIF and Emission Spectroscopy in Hot Air Plasma Generated by Microwave Resonant Cavity

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Plasma Science and Technology 2016年第3期18卷 259-265页

作者： F.MARCHAL M.YOUSFI N.MERBAHI G.WATTIEAUX A.PIQUEMAL University of Toulouse UPSLAPLACE CNRS UMR 5213 cea DAMDIF

Two experimental techniques have been used to quantify the atomic oxygen density in the case of hot air plasma generated by a microwave （MW） resonant cavity. The latter operates at a frequency of 2.45 GHz inside a cell of gas conditioning at a pressure of 600 mbar, an injected air flow of 12 L/min and an input MW power of 1 kW. The first technique is based on the standard two photon absorption laser induced fluorescence （TALIF） using xenon for calibration but applied for the first time in the present post discharge hot air plasma column having a temperature of about 4500 K near the axis of the nozzle. The second diagnostic technique is an actinometry method based on optical emission spectroscopy （OES）. In this case, we compared the spectra intensities of a specific atomic oxygen line （844 nm） and the closest wavelength xenon line （823 nm）. The two lines need to be collected under absolutely the same spectroscopic parameters. The xenon emission is due to the addition of a small proportion of xenon （1% Xe） of this chemically inert gas inside the air while a further small quantity of H2 （2~） is also added in the mixture in order to collect OH（A- X） and NH（A-X） spectra without noise. The latter molecular spectra are required to estimate gas and excitation temperatures. Optical emission spectroscopy measurements, at for instance the position z=12 mm on the axis plasma column that leads to a gas measured temperature equal to 3500 K, an excitation temperature of about 9500 K and an atomic oxygen density 2.09× 1017＋ 0.2×1017 cm-3. This is in very good agreement with the TALIF measurement, which is equal to 2.0×101T cm-3.

关键词： TALIF microwave air plasma atomic oxygen concentration actinometry,optical emission spectroscopy

Stable and accurate schemes for smoothed dissipative particle dynamics

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Applied Mathematics and Mechanics(English Edition) 2018年第1期39卷 83-102页

作者： G. FAURE G. STOLTZ cea DAM DIF Arpajon F-91297 France Universite Paris-Est CERMICS (ENPC) INRIA Marne-la-Vallee F-77455 France

Smoothed dissipative particle dynamics （SDPD） is a mesoscopic particle method that allows to select the level of resolution at which a fluid is simulated. The numerical integration of its equations of motion still suffers from the lack of numerical schemes satisfying all the desired properties such as energy conservation and stability. Similarities between SDPD and dissipative particle dynamics with energy （DPDE） con- servation, which is another coarse-grained model, enable adaptation of recent numerical schemes developed for DPDE to the SDPD setting. In this article, a Metropolis step in the integration of the fluctuation/dissipation part of SDPD is introduced to improve its stability.

关键词： smoothed dissipative particle dynamics (SDPD) numerical integration Metropolis algorithm

Petrography of alluvial sands as a past and present environmental indicator:Case of the Loire River(France)

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International Journal of Sediment Research 2013年第3期28卷 285-303页

作者： Jean-Jacques MACAIRE Isabelle GAY-OVEJERO Michel BACCHI Constantin COCIRTA Luc PATRYL Stéphane RODRIGUES University Franqois-Rabelais of Tours University Francois-Rabelais of Tours SARL RIVE 4. Commissariat a l'Energie Atomique-cea DAMDIF

Four sample sets of the Upper and Middle Loire river sands were analyzed in order to study the impact of natural and anthropogenic factors on their petrographic composition in space(on an 800 km stretch) and *** was determined by modal analysis of three sand-size fractions using a polarizing optical microscope and calculated for each sample("standard sand" = Sst).The watershed is composed mainly of endogenic(Massif Central) and sedimentary(southern Parisian Basin) rocks.B-set sands collected in channels for different water flows in 1996 show that Sst compositions vary by only 5%.Present-day sands in the Upper Loire and Middle Loire have very high petrographic immaturity comparing to others worldwide fluvial sands,although bio-climatic conditions favor sand maturation by source-rock weathering in the *** shows the strong impact of the Massif Central on sediment yield due to relief rejuvenation as a consequence of the formation of the Alps during the *** sands stored during the Weichselian and the Holocene in the Middle Loire floodplain,although partly weathered since their deposition,show higher inputs from the endogenic rocks of the Massif Central than present-day *** can be explained by Weichselian periglacial conditions and the development of crop farming since the Neolithic,which favored mechanical erosion,particularly in the Massif Central which is characterized by a cold,humid climate and steep *** upstream-downstream change in the composition of presently deposited sand is low in the diked *** shows however that basalt and some heavy mineral grains are vulnerable to abrasion during transport and indicates a marked sediment yield from ancient sediment stored in the *** is in line with the high incision of the river bed over the last 150 years partly due to dam construction and aggregate mining.

关键词： Fluvial sand Sand petrography Sediment source Tectonics impact Human impact Loire river

Monotonic Diamond and DDFV Type Finite-Volume Schemes for 2D Elliptic Problems

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Communications in Computational Physics 2023年第7期34卷 456-502页

作者： Xavier Blanc Francois Hermeline Emmanuel Labourasse Julie Patela UniversitéParis Cité Sorbonne UniversitéCNRSLaboratoire Jacques-Louis LionsF-75013 ParisFrance cea DAMDIFF-91297 ArpajonFrance UniversitéParis-Saclay CEA DAM DIFLaboratoire en Informatique Haute Performance pour le Calcul et la Simulation91297 ArpajonFrance

The DDFV(Discrete Duality Finite Volume)method is a finite volume scheme mainly dedicated to diffusion problems,with some outstanding *** scheme has been found to be one of the most accurate finite volume methods for diffusion *** the present paper,we propose a new monotonic extension of DDFV,which can handle discontinuous tensorial diffusion ***,we compare its performance to a diamond type method with an original interpolation method relying on polynomial *** is achieved by adapting the method of Gao et al[A finite volume element scheme with a monotonicity correction for anisotropic diffusion problems on general quadrilateral meshes]to our *** a technique does not require the positiveness of the secondary *** show that the two new methods are second-order accurate and are indeed monotonic on some challenging benchmarks as a Fokker-Planck problem.

关键词： Finite volume method anisotropic diffusion monotonic method DDFV scheme

A Node-Centered Artificial Viscosity Method for Two-Dimensional Lagrangian Hydrodynamics Calculations on a Staggered Grid

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Communications in Computational Physics 2010年第9期8卷 877-900页

作者： A.Burbeau-Augoula cea DIFF-91297 ArpajonFrance

This work deals with the simulation of two-dimensional Lagrangian hydrodynamics *** objective is the development of an artificial viscosity that is to be used in conjunction with a staggered placement of variables:thermodynamics variables are centered within cells and position and fluid velocity at ***[***.,228(2009),2391-2425],Maire develops a high-order cell-centered scheme for solving the gas dynamics *** numerical results show the accuracy and the robustness of the method,and the fact that very few Hourglass-type deformations are *** objective is to establish the link between the scheme of Maire and the introduction of artificial viscosity in a Lagrangian code based on a staggered *** idea is to add an extra degree of freedom to the numerical scheme,which is an approximation of the fluid velocity within *** that,we can locally come down to a cell-centered approximation and define the Riemann problem associated to discrete variable discontinuities in a very natural *** results in a node-centered artificial viscosity *** experiments show the robustness and the accuracy of the method,which is very easy to implement.

关键词： Hydrodynamics staggered discretization artificial viscosity Lagrangian simulation shock waves finite volume scheme

Influence of a Magnetic Guide Field on Self-Injection in Wakefield Acceleration

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Journal of Modern Physics 2012年第12期3卷 1983-1990页

作者： Alain Bourdier Guillaume Girard Sébastien Rassou Xavier Davoine Mathieu Drouin cea DAM DIF Arpajon France

The influence of an external static field applied in the direction of propagation of a high intensity driving laser pulse on the electron trapping in laser wakefield acceleration is explored. It is shown that, in the ... 详细信息

关键词： Laser Wakefield Acceleration Magnetic Guide Field Electron Injection Self-Trapping

Influence of a Static Magnetic Field on Beam Emittance in Laser Wakefield Acceleration

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Journal of Modern Physics 2012年第12期3卷 1991-1997页

作者： Mathieu Drouin Alain Bourdier Quentin Harry Sébastien Rassou cea DAM DIF Arpajon France

The enhancement of trapping and the optimization of beam quality are two key issues of Laser Wakefield Acceleration (LWFA). The effect of a homogenous constant magnetic field B0, parallel to the direction of propagation of the pump pulse, is studied in the blowout regime via 2Dx3Dv Particle-In-Cell simulations. Electrons are injected into the wake using a counter-propagating low amplitude laser. Transverse currents are generated at the rim of the bubble, which results in the amplification of the B0 field at the rear of the bubble. Therefore the dynamics of the beam is modified, the main effect is the reduction of the transverse emittance when B0 is raised. Depending on beam loading effects the low energy tail, observed in the non-magnetized case, can be suppressed when B0 is applied, which provides a mono-energetic beam.

关键词： Laser Wakefield Acceleration Magnetic Field Beam Emittance Beam Loading

Discrete Duality Finite Volume Discretization of the Thermal-P_(N) Radiative Transfer Equations on General Meshes

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Communications in Computational Physics 2022年第2期31卷 398-448页

作者： Francois Hermeline Universite Paris-Saclay Laboratoire en Informatique Haute Performance pour le Calcul et la simulationCEADAMDIF91297 ArpajonFrance

The discrete duality finite volume method has proven to be a practical tool for discretizing partial differential equations coming from a wide variety of areas of physics on nearly arbitrary *** main ingredients of the method are:(1)use of three meshes,(2)use of the Gauss-Green theorem for the approximation of derivatives,(3)discrete integration by *** this article we propose to extend this method to the coupled grey thermal-P_(N) radiative transfer equations in Cartesian and cylindrical coordinates in order to be able to deal with two-dimensional Lagrangian approximations of the interaction of matter with *** stability under a Courant-Friedrichs-Lewy condition and the preservation of the diffusion asymptotic limit are proved while the experimental second-order accuracy is observed with manufactured *** numerical experiments are reported which show the good behavior of the method.

关键词： Hybrid multiscale models radiative transfer equation grey P_(N)approximation discrete duality finite volume method

Influence of a Magnetic Guide Field on Injection in Wakefield Acceleration

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Journal of Modern Physics 2012年第9期3卷 1018-1020页

作者： Alain Bourdier Sébastien Rassou Guillaume Girard Mathieu Drouin cea DAM DIF Arpajon France

The influence of an external static field applied in the direction parallel to the direction of propagation of a high intensity driving laser pulse on the electron trapping in laser wakefield acceleration is explored.

关键词： Laser Wakefield Acceleration Magnetic Field Electron Injection Self-Trapping