Publications

Sont listées ci-dessous, par année, les publications figurant dans l'archive ouverte HAL.

2010

Météorologie de l'Espace en Afrique (II) le programme ISWI - International Space Weather Initiative
- Amory-Mazaudier Christine
- Kobea A.
- Ouattara F.
- Dinga B.
- Doumbia V.
- Hady A.
- Hounginou E.
- Kahindo B.
- Madougou S.
- Mahrous A.
- Ndekatou T.
- Uwamahoro J.
- Zaourar N.
- Bock Olivier
- Cohen Y.
- Damé Luc
- Fleury Rolland
- Lassudrie-Duchesne Patrick
- Petitdidier Monique
, 2010, pp.12 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.
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
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
The WHISPER Relaxation Sounder and the CLUSTER Active Archive
- Trotignon Jean-Gabriel
- Décréau Pierrette
- Rauch Jean-Louis
- Vallières Xavier
- Rochel A.
- Kougblénou S.
- Lointier G.
- Facskó G.
- Canu Patrick
- Darrouzet F.
- Masson A.
- Taylor M.
- Escoubet C. Philippe
, 2010, pp.185-208. The Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation (WHISPER) instrument is part of the Wave Experiment Consortium (WEC) of the CLUSTER mission. With the help of the long double sphere antennae of the Electric Field and Wave (EFW) instrument and the Digital Wave Processor (DWP), it delivers active (sounding) and natural (transmitter off) electric field spectra, respectively from 4 to 82 kHz, and from 2 to 80 kHz. These frequency ranges have been chosen to include the electron plasma frequency, which is closely related to the total electron density, in most of the regions encountered by the CLUSTER spacecraft. Presented here is an overview of the WHISPER data products available in the CLUSTER Active Archive (CAA). The instrument and its performance are first recalled. The way the WHISPER products are obtained is then described, with particular attention being paid to the density determination. Both sounding and natural measurements are commonly used in this process, which depends on the ambient plasma regime. This is illustrated using drawings similar to the Bryant plots commonly used in the CLUSTER master science plan. These give a clear overview of typical density values and the parts of the orbits where they are obtained. More information on the applied software or on the quality/reliability of the density determination can also be highlighted. (10.1007/978-90-481-3499-1_12)
DOI : 10.1007/978-90-481-3499-1_12
Three dimensional anisotropic k-spectra of turbulence at sub-proton scales in the solar wind
- Sahraoui Fouad
- Goldstein M.L.
- Belmont Gérard
- Canu Patrick
- Rezeau Laurence
Physical Review Letters, American Physical Society, 2010 (105), pp.131101. We show the first three dimensional (3D) dispersion relations and k spectra of magnetic turbulence in the solar wind at subproton scales. We used the Cluster data with short separations and applied the k-filtering technique to the frequency range where the transition to subproton scales occurs. We show that the cascade is carried by highly oblique kinetic Alfve´n waves with !plas 0:1!ci down to k?i 2. Each k spectrum in the direction perpendicular to B0 shows two scaling ranges separated by a breakpoint (in the interval ½0:4; 1k?i): a Kolmogorov scaling k1:7 ? followed by a steeper scaling k4:5 ? . We conjecture that the turbulence undergoes a transition range, where part of the energy is dissipated into proton heating via Landau damping and the remaining energy cascades down to electron scales where electron Landau damping may predominate. (10.1103/PhysRevLett.105.131101)
DOI : 10.1103/PhysRevLett.105.131101
The Plasma Wave Investigation (PWI) onboard the BepiColombo/MMO: First measurement of electric fields, electromagnetic waves, and radio waves around Mercury
- Kasaba Y.
- Bougeret J.-L.
- Blomberg L. G.
- Kojima H.
- Yagitani S.
- Moncuquet M.
- Trotignon Jean-Gabriel
- Chanteur Gérard
- Kumamoto A.
- Kasahara Y.
- Lichtenberger J.
- Omura Y.
- Ishisaka K.
- Matsumoto H.
Planetary and Space Science, Elsevier, 2010, 58 (1-2), pp.238-278. The BepiColombo Mercury Magnetospheric Orbiter (MMO) spacecraft includes the plasma and radio wave observation system called Plasma Wave Investigation (PWI). Since the receivers for electric field, plasma waves, and radio waves are not installed in any of the preceding spacecraft to Mercury, the PWI will provide the first opportunity for conducting in-situ and remote-sensing observations of electric fields, plasma waves, and radio waves in the Hermean magnetosphere and exosphere. These observations are valuable in studying structure, dynamics, and energy exchange processes in the unique magnetosphere of Mercury. They are characterized by the key words of the non-MHD environment and the peculiar interaction between the relatively large planet without ionosphere and the solar wind with high dynamic pressure. The PWI consists of three sets of receivers (EWO, SORBET, and AM2P), connected to two sets of electric field sensors (MEFISTO and WPT) and two kinds of magnetic field sensors (LF-SC and DB-SC). The PWI will observe both waveforms and frequency spectra in the frequency range from DC to 10 MHz for the electric field and from 0.3 Hz to 640 kHz for the magnetic field. From 2008, we will start the development of the engineering model, which is conceptually consistent with the flight model design. The present paper discusses the significance and objectives of plasma/radio wave observations in the Hermean magnetosphere, and describes the PWI sensors, receivers and their performance as well as the onboard data processing. (10.1016/j.pss.2008.07.017)
DOI : 10.1016/j.pss.2008.07.017
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
Whistler waves guided by density depletion ducts in a magnetoplasma
- Bakharev P. V.
- Zaboronkova T. M.
- Kudrin A. V.
- Krafft C.
Fizika Plazmy / Plasma Physics Reports, MAIK Nauka/Interperiodica, 2010, 36 (11), pp.919-930. The guided propagation of whistler waves along cylindrical density depletion ducts in a magneto-plasma is studied. It is shown that, under certain conditions, such ducts can support volume and surface eigenmodes. The dispersion properties and field structure of whistler modes guided by density depletion ducts are analyzed. The effect of collisional losses in the plasma on the properties of modes is discussed. (10.1134/S1063780X10110012)
DOI : 10.1134/S1063780X10110012
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
MD simulations of GaN sputtering by Ar+ 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
Global response to local ionospheric mass ejection
- Moore T. E.
- Fok M.-C. H.
- Delcourt Dominique C.
- Slinker Steve P.
- Fedder Joel A.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2010, 115 (A12). We revisit a reported "Ionospheric Mass Ejection" using prior event observations to guide a global simulation of local ionospheric outflows, global magnetospheric circulation, and plasma sheet pressurization, and comparing our results with the observed global response. Our simulation framework is based on test particle motions in the Lyon-Fedder-Mobarry (LFM) global circulation model electromagnetic fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere, and includes an embedded plasmaspheric simulation. Global circulation is stimulated using the observed solar wind conditions for the period 24-25 September 1998. This period begins with the arrival of a Coronal Mass Ejection, initially with northward, but later with southward interplanetary magnetic field. Test particles are launched from the ionosphere with fluxes specified by local empirical relationships of outflow to electrodynamic and particle precipitation imposed by the MHD simulation. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the full equations of motion. Results are compared with the observed ring current and a simulation of polar and auroral wind outflows driven globally by solar wind dynamic pressure. We find good quantitative agreement with the observed ring current, and reasonable qualitative agreement with earlier simulation results, suggesting that the solar wind driven global simulation generates realistic energy dissipation in the ionosphere and that the Strangeway relations provide a realistic local outflow description. (10.1029/2010JA015640)
DOI : 10.1029/2010JA015640
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
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
ECRH for JET: A feasibility study
- Lennholm M.
- Giruzzi G.
- Parkin A.
- Bouquey F.
- Braune H.
- Bruschi A.
- Luna Elena de La
- Denisov G.
- Edlington T.
- Farina D.
- Farthing J.
- Figini Lorenzo
- Garavaglia S.
- Garcia J.
- Gerbaud Thomas
- Granucci G.
- Henderson M.
- Horton L.
- Kasparek W.
- Khilar P.
- Jennison M.
- Kirneva N.
- Kislov D.
- Kuyanov A.
- Litaudon X.
- Litvak A.
- Moro A.
- Nowak S.
- Parail V.
- Plaum B.
- Rimini F.
- Saibene G.
- Sips A. C. C.
- Sozzi C.
- Spaeh P.
- Trukhina E.
- Vaccaro A.
- Vdovin V.
Fusion Engineering and Design, Elsevier, 2010, 6-8, pp.805 - 809. For JET to fulfil its mission in preparing ITER operation, the installation of an electron cyclotron resonance heating system on JET would be desirable. The study described in this paper has investigated the feasibility of installing such a system on JET. The principal goals of such a system are: current drive over a range of radii for NTM stabilization, sawtooth control and current profile tailoring and central electron heating to equilibrate electron and ion temperatures in high performance discharges. The study concluded that a 12 gyrotron, 10 MW, system at the ITER frequency (170 GHz) adapted for fields of 2.7-3.3 T would be appropriate for the operation planned in JET. An antenna allowing toroidal and poloidal steering over a wide range is being designed, using the ITER upper launcher steering mechanism. The use of ITER diamond windows and transmission line technology is suggested while power supply solutions partially reusing existing JET power supplies are proposed. Detailed planning shows that such a system can be operational in about 5 years from the time that the decision to proceed is taken. The cost and required manpower associated with implementing such a system on JET has also been estimated. (C) 2011 EURATOM. Published by Elsevier B.V. All rights reserved.Commiss European Communities, B-1049 Brussels, Belgium.IRFM, CEA, F-13108 St Paul Les Durance, France.Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England.EURATOM, Max Planck IPP, D-17491 Greifswald, Germany.EURATOM, CNR, Ist Fis Plasma, I-20125 Milan, Italy.Asociac EURATOM CIEMAT, Lab Nacl Fus, Madrid 28040, Spain.Inst Appl Phys, Nizhnii Novgorod 603155, Russia.Ecole Polytech, LPTP, F-91128 Palaiseau, France.ITER Org, F-13108 St Paul Les Durance, France.Univ Stuttgart, IPF, Stuttgart, Germany.RRC Kurchatov Inst, Moscow, Russia.Fus Energy, Barcelona 08019, Spain.Karlsruhe Inst Technol, Karlsruhe, Germany. (10.1016/j.fusengdes.2011.01.136)
DOI : 10.1016/j.fusengdes.2011.01.136
Residual parallel Reynolds stress due to turbulence intensity gradient in tokamak plasmas
- Gürcan Özgür D.
- Diamond P.H.
- Hennequin Pascale
- Mcdevitt C.J.
- Garbet X.
- Bourdelle C.
Physics of Plasmas, American Institute of Physics, 2010, 17, pp.112309. A novel mechanism for driving residual stress in tokamak plasmas based on k∥ symmetry breaking by the turbulence intensity gradient is proposed. The physics of this mechanism is explained and its connection to the wave kinetic equation and the wave-momentum flux is described. Applications to the H-mode pedestal in particular to internal transport barriers, are discussed. Also, the effect of heat transport on the momentum flux is discussed. (10.1063/1.3503624)
DOI : 10.1063/1.3503624
Evidence of atomic adsorption on TiO2 under plasma exposure and related C2H2 surface reactivity
- Guaitella Olivier
- Lazzaroni Claudia
- Marinov Daniil
- Rousseau Antoine
Applied Physics Letters, American Institute of Physics, 2010, 97, pp.011502. Adsorption/reaction kinetics of C2H2 on the surface of plasma-treated SiO2 and TiO2 catalysts is studied. The catalysts are pretreated with a dc discharge in Ar, O2, N2, or air. Then 950 ppm of C2H2 in air is introduced in the closed-volume reactor. It is found that TiO2 pretreated with O2 or air plasma catalyzes C2H2 removal from the gas phase without any UV activation. During 10 min after introduction the loss of C2H2 in the whole reactor is about 5×1015 molecules. Comparison between different pretreatment procedures shows that weakly bonded oxygen atoms may remain on TiO2 long after plasma exposure (10.1063/1.3462295)
DOI : 10.1063/1.3462295
On the Boltzmann relation in a cold magnetized plasma
- Nasi L.
- Raimbault Jean-Luc
Physics of Plasmas, American Institute of Physics, 2010, 17, pp.113513. A systematic and exact comparison between the forces acting on magnetized electrons in a current-free plasma is considered within a fluid model. We show that the Boltzmann relation is fulfilled in the drift-diffusion approximation when (hi/he)(1 he2)/(1 hi2)⪡1 where he (or hi) is the ratio of the electron (or ion) cyclotron to the collision frequency. When the nonlinear inertia terms are taken into account, the previous criterion is too rough and must be modified. In particular it is proved that the Boltzmann relation is not uniformly valid in the plasma. The case of bounded plasmas where the electron temperature must be determined self-consistently is discussed in detail. (10.1063/1.3517174)
DOI : 10.1063/1.3517174

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