Publications

2010

Simulations 2D PIC d'un choc courbe supercritique: dynamique du précurseur électromagnétique
- Stienlet J.
- Savoini Philippe
- Lembège Bertrand
, 2010, pp.5 p..
Météorologie de l'Espace en Afrique : les programmes Année 2010 Egypte France et ISWI
- Damé Luc
- Marhous Ayman
- Amory-Mazaudier Christine
- Petitdidier Monique
- Hady Ahmed
, 2010, pp.8 p..
Modelling of chlorine inductive discharges
- Chabert Pascal
- Despiau-Pujo Emilie
, 2010.
Effect of low-frequency power on electron density and ion flux in dual-frequency capacitive radiofrequency discharges
- Booth Jean-Paul
- Curley G.
- Chabert Pascal
, 2010.
Nonstationarity of two / three - dimensional supercritical perpendicular shocks: nonlinear whistler emission versus shock front self-reformation
- Lembège Bertrand
- Savoini Philippe
- Hellinger P.
- Travnicek P. M.
, 2010.
Measurements and Modeling of Turbulent Transport in the Tore Supra Tokamak
- Garbet X.
- Abiteboul J.
- Benkadda S.
- Bourdelle C.
- Casati A.
- Clairet F.
- Dubuit N.
- Falchetto G.
- Fenzi C.
- Futatani S.
- Grandgirard V.
- Guirlet R.
- Gürcan Özgür D.
- Hennequin Pascale
- Heuraux S.
- Hoang G.T.
- Honoré Cyrille
- Sabot R.
- Sarazin Y.
- Ségui J.-L.
- Smolyakov A.
- Trier Elisée
- Vermare Laure
- Villegas D.
, 2010, 1308, pp.75-84. This paper presents an overview of recent advances in modeling and measurements of turbulence in Tore Supra plasmas. Spatio‐temporal properties of turbulence are discussed in relation with transport models. An explanation is proposed for the k−3 decay of wave number spectra, which are observed by using both coherent laser scattering and Doppler reflectometry. Also the interplay between turbulence and flows has been investigated. It is shown that toroidal rotation results from a competition between neoclassical and turbulence flow generation. Finally a new method has been proposed to determine the transport coefficients of impurities. These coefficients are usually well above the neoclassical prediction. (10.1063/1.3526165)
DOI : 10.1063/1.3526165
Surface discharges: possible applications for plasma-assisted ignition and electric field measurements (AIAA 2010-1587)
- Starikovskaia Svetlana
- Allegraud Katia
- Guaitella Olivier
- Kosarev I.N.
- Mintoussov E.I.
- Pendleton S.J.
- Popov N.A.
- Sagulenko P.N.
- Rousseau Antoine
, 2010.
Plasma assisted ignition and combustion
- Starikovskaia Svetlana
- Starikovskii A.Yu.
, 2010, pp.71-93.
Plasmas froids
- Booth Jean-Paul
- Chabert Pascal
Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.3-5. ISSN : 1775-0385
Quantum Cascade Laser Absorption Spectroscopy - a New Method to Study Molecular Plasma Components
- Röpcke J.
- Glitsch S.
- Davies P.B.
- Hempel F.
- Lang N.
- Rousseau Antoine
- Wege S.
- Welzel S.
Journal of Physics: Conference Series, IOP Science, 2010, 227, pp.012005. The recent development of quantum cascade lasers (QCLs) offers an attractive new option for the monitoring and control of industrial plasma processes and for trace-gas analysis as well as for highly time-resolved studies on the kinetics of plasma processes. The contribution reviews selected examples of the application of QCLs for infrared absorption studies in basic research and for plasma monitoring and control in industry. (10.1088/1742-6596/227/1/012005)
DOI : 10.1088/1742-6596/227/1/012005
Modelling of an afterglow plasma in air produced by a pulsed discharge
- Pintassilgo C.D.
- Guerra V.
- Guaitella Olivier
- Rousseau Antoine
Plasma Sources Science and Technology, IOP Publishing, 2010, 19, pp.055001. A kinetic model is developed to study the afterglow plasma of a pulsed discharge in air. This model includes a detailed analysis of the temporal evolution of heavy species during the pulse, followed by their relaxation in the afterglow. The predicted results are compared with two experimental sets performed in the time afterglow of a pulsed discharge in N220%O2 at a pressure p = 133 Pa involving the measurements of (i) N2(B) and N2(C) fluorescences for a discharge current I = 40 mA and a pulse duration τ = 200 µs and 10 ms, together with (ii) the absolute concentration of NO(X) for I = 40 and 80 mA with τ varying from 1 to 4 ms. The results of the model agree reasonably well with the measurements of N2(B) and N2(C) decays. It is shown that under these experimental conditions, N2(B) is always populated mainly via the process N2(A) N2(X, 5 ≤ v ≤ 14) → N2(B) N2(X, v = 0), while the relaxation of N2(C) is dominated by the pooling reaction N2(A) N2(A) → N2(C) N2(X, v = 0). An almost constant concentration of NO(X) is experimentally observed until the remote afterglow, but the present model is only capable of predicting the same order of magnitude for afterglow times t 0.05 s. Several hypotheses are discussed and advanced in order to explain this discrepancy. (10.1088/0963-0252/19/5/055001)
DOI : 10.1088/0963-0252/19/5/055001
Plasmas Naturels : Le Programme National Soleil - Terre
- Fontaine Dominique
Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.27-31. ISSN : 1775-0385
Bepi-Colombo : Mercury Exploration
- Chanteur Gérard
Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.32-33. ISSN : 1775-0385
Planar Wire-Array Z-Pinch Implosion Dynamics and X-Ray Scaling at Multiple-MA Drive Currents for a Compact Multisource Hohlraum Configuration
- Jones B.
- Ampleford D. J.
- Vesey R. A.
- Cuneo Michael E.
- Coverdale C. A.
- Waisman E. M.
- Jones M. C.
- Fowler W. E.
- Stygar W. A.
- Serrano J. D.
- Vigil M. P.
- Esaulov A. A.
- Kantsyrev Viktor L.
- Safronova Alla S.
- Williamson Kenneth M.
- Chuvatin Alexandre S.
- Rudakov Leonid I.
Physical Review Letters, American Physical Society, 2010, 104 (12), pp.125001. An indirect drive configuration is proposed wherein multiple compact Z-pinch x-ray sources surround a secondary hohlraum. Planar compact wire arrays allow reduced primary hohlraum surface area compared to cylindrical loads. Implosions of planar arrays are studied at up to 15 TW x-ray power on Saturn with radiated yields exceeding the calculated kinetic energy, suggesting other heating paths. X-ray power and yield scaling studied from 16 MA motivates viewfactor modeling of four 6-MA planar arrays producing 90 eV radiation temperature in a secondary hohlraum. (10.1103/PhysRevLett.104.125001)
DOI : 10.1103/PhysRevLett.104.125001
Nonlinear fan instability of electromagnetic waves
- Krafft C.
- Volokitin A.
Physics of Plasmas, American Institute of Physics, 2010, 17, pp.102303. This paper studies the linear and nonlinear stages of the fan instability, considering electromagnetic waves of the whistler frequency range interacting resonantly with energetic electron fluxes in magnetized plasmas. The main attention is paid to determine the wave-particle interaction processes that can lead to the excitation of intense electromagnetic waves by nonequilibrium particle distributions involving suprathermal tails, and to explain under what conditions and through what mechanisms they can occur, develop, and saturate. This paper presents and discusses two main processes: (i) the linear fan instability and (ii) the nonlinear process of dynamical resonance merging, which can significantly amplify the energy carried by linearly destabilized waves after they saturate due to particle trapping. This study consists of (i) determining analytically and numerically, for parameters typical of space and laboratory plasmas, the linear growth rates of whistlers excited by suprathermal particle fluxes through the fan instability, as well as the corresponding thresholds and the physical conditions at which the instability can appear, (ii) building a theoretical self-consistent 3D model and a related numerical code for describing the nonlinear evolution of the wave-particle system, and (iii) performing numerical simulations to reveal and characterize the nonlinear amplification process at work, its conditions of development, and its consequences, notably in terms of electromagnetic wave radiation. The simulations show that when the waves have reached sufficient energy levels owing to the linear fan instability, they saturate by trapping particles and due to the complex dynamics of these particles in the electromagnetic fields, the resonant velocities' domains of the waves overlap and merge, meanwhile a strong increase of the wave energy occurs. (10.1063/1.3479829)
DOI : 10.1063/1.3479829
Bilan et Perspective 2006 - 2009, Programme National Soleil Terre
- Fontaine Dominique
- Vilmer N.
, 2010.
Particle transport in low core turbulence Tore-Supra plasmas
- Guirlet R.
- Sirinelli A.
- Parisot T.
- Sabot R.
- Artaud J.F.
- Bourdelle C.
- Garbet X.
- Hennequin Pascale
- Hoang G.T.
- Imbeaux Frédéric
- Segui J.-L.
- Mazon D.
- Villegas D.
Nuclear Fusion, IOP Publishing, 2010, 50, pp.095009. Electron and impurity transport has been studied in sawtoothing plasmas in the Tore-Supra tokamak. High time and space resolution measurements of the electron density reveal the existence of a flat profile region encompassing the q = 1 surface, on which is superimposed a density peak building up between sawtooth relaxations. For the first time in this regime, we have determined the underlying transport of both nickel and electrons independently of the effect of sawteeth in the central part of the plasma. Electron transport is consistent with the neoclassical expectations only in the close vicinity of the magnetic axis. Further out, it exceeds the neoclassical values as calculated with the NCLASS code, although the turbulence level is very low in the whole central region region. In contrast, nickel transport is in good agreement with the neoclassical calculations in the same region. The neoclassical effect on trapped particles of a persisting mode due to incomplete reconnection of the magnetic surfaces is consistent with these observations. (10.1088/0029-5515/50/9/095009)
DOI : 10.1088/0029-5515/50/9/095009
Three-dimensional structure of electron density fluctuations in the Hall thruster plasma: ExB mode
- Tsikata Sedina
- Honoré Cyrille
- Lemoine N.
- Grésillon D.
Physics of Plasmas, American Institute of Physics, 2010, 17, pp.112110. Collective scattering measurements have been conducted on the plasma of a Hall thruster, in which the electron density fluctuations are fully characterized by the dynamic form factor. The dynamic form factor amplitude distribution has been measured depending on the k-vector spatial and frequency components at different locations. Fluctuations are seen as propagating waves. The largest amplitude mode propagates nearly along the cross-field direction but at a phase velocity that is much smaller than the E×B drift velocity. Refined directional analysis of this largest amplitude mode shows a thin angular emission diagram with a mean direction that is not strictly along the E×B direction but at small angles near it. The deviation is oriented toward the anode in the (E,E×B) plane and toward the exterior of the thruster channel in the (B,E×B) plane. The density fluctuation rate is on the order of 1%. These experimentally determined directional fluctuation characteristics are discussed with regard to the linear kinetic theory model and particle-in-cell simulation results. (10.1063/1.3499350)
DOI : 10.1063/1.3499350
Design criteria and validation of a vacuum load current multiplier on a mega-ampere microsecond inductive storage generator
- Chuvatin Alexandre S.
- Kim A. A.
- Kokshenev V. A.
- Kovalchuk Boris M.
- Lassalle Francis
- Calamy Hervé
- Krishnan M.
Laser and Particle Beams, Cambridge University Press (CUP), 2010, 28 (3), pp.361-369. The load current multiplier concept (LCM) was suggested for improving the energy transfer efficiency from pulse power generators to loads. The concept was initially demonstrated at atmospheric pressure and dielectric insulation on a compact, 100 kA, microsecond capacitor bank. This paper reports on the LCM design criteria for mega-ampere vacuum pulse power when the LCM comprises a large-inductance magnetic flux extruder cavity without a magnetic core. The analytical and numerical design approach presented was experimentally validated on GIT12 mega-ampere inductive energy storage generator with a constant-inductance load. The LCM technique increased the peak load current from typically 4.6 MA at 1.87 µs on this generator, to 6.43 MA at 2.0 µs. The electromagnetic power into a ~10 nH load increased from 100 GW to 230 GW. This result is in good agreement with the presented numerical simulations and it corresponds to a 95% increase of the achievable magnetic pressure at 8 cm radius in the load. The compact, LCM hardware allows the GIT12 generator to operate more efficiently without modifying the stored energy or architecture. The demonstrated load power and energy increase using the LCM concept is of importance for further studies on power amplification in vacuum and high energy density physics. (10.1017/S0263034610000224)
DOI : 10.1017/S0263034610000224
Théorie des Plasmas
- Firpo Marie-Christine
Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.26-27. ISSN : 1775-0385
Simultaneous FAST and Double Star TC1 observations of broadband electrons during a storm time substorm
- Nakajima A.
- Shiokawa K.
- Seki K.
- Nakamura R.
- Keika K.
- Baumjohann W.
- Takada T.
- Mcfadden J. P.
- Carlson C. W.
- Fazakerley A.
- Rème H.
- Dandouras I.
- Strangeway R. J.
- Le Contel Olivier
- Cornilleau-Wehrlin Nicole
- Yearby K. H.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2010, 115, pp.7217. Broadband electrons (BBEs) exhibit remarkable electron flux enhancements over a broad energy range (0.03-30 keV) near the equatorward edge of the auroral oval during geomagnetic storms. Here, we report a BBE event observed by the Fast Auroral Snapshot (FAST) satellite at 1355-1359 UT, 61°-66° invariant latitudes, 0600 magnetic local time (MLT), and 3800 km altitude during a storm on 25 July 2004. The Double Star (DS) TC1 satellite was located near the magnetic equator at L = 5.7, close to the same local time as FAST. We investigate the acceleration process of BBEs from the inner magnetosphere to near the ionosphere by comparing electron data obtained by FAST and DS TC1. We also investigate both plasma and field variations in the inner magnetosphere associated with substorm onset using DS TC1 data to examine the relationship between the BBEs and the storm time substorm. Ground geomagnetic field data show a positive H-bay at 1349 UT at 0600 MLT, indicating that a storm time substorm started just before the appearance of the BBEs. At 1350 UT, a tailward ion flow was observed by DS TC1. Then, DS TC1 observed a local dipolarization and a drastic ion density enhancement at 1351 UT, indicating that particle heating associated with the substorm was occurring in the inner magnetosphere. From 1352 UT, electron fluxes were isotropically enhanced at energies above 0.5 keV as observed by DS TC1. On the other hand, the pitch angle distribution of BBEs at the FAST altitude showed field-aligned lower-energy electrons below 0.5 keV and isotropic higher-energy electrons above 0.5 keV. From these data, it was inferred that the BBEs might consist of two energy components due to the acceleration or heating of electrons at different altitudes in association with the storm time substorm. (10.1029/2009JA014907)
DOI : 10.1029/2009JA014907
Ion dynamics during compression of Mercury's magnetosphere
- Delcourt Dominique C.
- Moore T. E.
- Fok M.-C. H.
Annales Geophysicae, European Geosciences Union, 2010, 28, pp.1467-1474. Because of the small planetary magnetic field as well as proximity to the Sun that leads to enhanced solar wind pressure as compared to Earth, the magnetosphere of Mercury is very dynamical and at times subjected to prominent compression. We investigate the dynamics of magnetospheric ions during such compression events. Using three-dimensional single-particle simulations, we show that the electric field induced by the time varying magnetic field can lead to significant ion energization, up to several hundreds of eVs or a few keVs. This energization occurs in a nonadiabatic manner, being characterized by large enhancements of the ion magnetic moment and bunching in gyration phase. It is obtained when the ion cyclotron period is comparable to the field variation time scale. This condition for nonadiabatic heating is realized in distinct regions of space for ions with different mass-to-charge ratios. During compression of Mercury's magnetosphere, heavy ions originating from the planetary exosphere may be subjected to such an abrupt energization, leading to loading of the magnetospheric lobes with energetic material. (10.5194/angeo-28-1467-2010)
DOI : 10.5194/angeo-28-1467-2010
Design of magnetic concentrators for high sensitivity anisotropic magnetoresistor devices
- Mansour Malik
- Coillot Christophe
- Chanteur Gérard
- Roux A.
- Nguyen van Dau Frédéric
Journal of Applied Physics, American Institute of Physics, 2010, 107, pp.09E707. In this work, a very promising shape of magnetic concentrators taking advantage of the symmetrical flux leakage of Mn-Zn ferrite magnetic cores is presented. This configuration consists of two ferromagnetic rods separated by two air gaps allowing to place anisotropic magnetoresistance sensors in the core axis. Results from three-dimensional finite elements modeling are presented. We show that an appropriate shape optimization of core extremities enables to improve significantly the amplification factor without any increase in length. (10.1063/1.3337747)
DOI : 10.1063/1.3337747
MD simulations of GaN sputtering by Ar<SUP>+</SUP> ions : Ion-induced damage and near-surface modification under continuous bombardment
- Despiau-Pujo Emilie
- Chabert Pascal
Journal of Vacuum Science & Technology A, American Vacuum Society, 2010, 28 (5), pp.1105. Results from molecular dynamics simulations of continuous 50200 eV Ar bombardment on wurtzite and zinc blende GaN surfaces are reported. A new analytical bond-order potential, originally developed for growth process studies, is used to investigate the low-energy physical sputtering of GaN compounds. Preferential sputtering of N atoms is initially observed up to 3.5×1015 ions/cm2 fluence, after which the layers reach steady state sputtering. The crystalline structure of the GaN sample does not have a major influence on the sputtering yield due to the rapid amorphization of the top surface after a few hundred impacts. Concentration depth profiles indicate a surface enrichment in gallium with a N/Ga concentration ratio equal to 0.59±0.1 for 100 eV bombardment, in agreement with published experimental studies. For the same conditions, Ga, N, and GaN species represent 25, 60, and 7% of the sputtered products. A significant fraction of those products leave the surface with kinetic energies sufficiently high to damage the passivation layers on sidewalls during etching processes dominated by physical bombardment. (10.1116/1.3460904)
DOI : 10.1116/1.3460904
Surface loss rates of H and Cl atoms in an inductively coupled plasma etcher using time-resolved electron density and optical emission measurements
- Curley G. A.
- Gatilova L.
- Guilet S.
- Bouchoule S.
- Gogna G. S.
- Sirse Nishant
- Karkari S.
- Booth Jean-Paul
Journal of Vacuum Science & Technology A, American Vacuum Society, 2010, 28 (2), pp.360-372. A study is undertaken of the loss kinetics of H and Cl atoms in an inductively coupled plasma (ICP) reactor used for the etching of III-V semiconductor materials. A time-resolved optical emission spectroscopy technique, also referred to as pulsed induced fluorescence (PIF), has been combined with time-resolved microwave hairpin probe measurements of the electron density in a pulsed Cl2/H2-based discharge for this purpose. The surface loss rate of H, kwH, was measured in H2 plasma and was found to lie in the 125500 s−1 range (γH surface recombination coefficient of ∼ 0.0060.023), depending on the reactor walls conditioning. The PIF technique was then evaluated for the derivation of kwCl, and γCl in Cl2-based plasmas. In contrast to H2 plasma, significant variations in the electron density may occur over the millisecond time scale corresponding to Cl2 dissociation at the rising edge of the plasma pulse. By comparing the temporal evolution of the electron density and the Ar-line intensity curves with 10% of Ar added in the discharge, the authors show that a time-resolved actinometry procedure using Ar as an actinometer is valid at low to moderate ICP powers to estimate the Cl loss rate. They measured a Cl loss rate of ∼ 125200 s−1 (0.03 ≤ γCl ≤ 0.06) at 150 W ICP power for a reactor state close to etching conditions. The Cl surface loss rate was also estimated for high ICP power (800 W) following the same procedure, giving a value of ∼ 130150 s−1 (γCl ∼ 0.04), which is close to that measured at 150 W ICP power. (10.1116/1.3330766)
DOI : 10.1116/1.3330766

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