Publications

2010

• Cluster observations of outflowing electron distributions and broadband electrostatic emissions above the polar cap
  
  • Teste A.
  • Fontaine Dominique
  • Canu Patrick
  • Belmont Gérard
  Geophysical Research Letters, American Geophysical Union, 2010, 37, pp.3103. We investigate the excellent correlation between ionospheric upgoing electron beams and broadband electrostatic emissions (0-6 kHz) observed by Cluster, at 5 to 9 Earth's radii above the polar cap. In the absence of detailed, high time resolution waveform data in that region, we precisely analyzed several electron beams to obtain information concerning wave-particle interactions. Our results indicate that these beams are extremely variable and occasionally show multiple components. The processes involved might then occur on very short time scales, of the order of or shorter than sampling rates, typically 100 ms. We suggest that non linearities are at the origin of the spread of the frequency range of the waves simultaneously observed, as well as of the beam variability. We conclude that these electron beams are likely to destabilize Langmuir waves and, by the non-linear evolution of the electron bump-on-tail instability, could be responsible for the appearance of electrostatic solitary waves above the polar cap. (10.1029/2009GL041593)
  DOI : 10.1029/2009GL041593
• 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
• 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
• Poloidal rotation and its relation to the potential vorticity flux
  
  • Mcdevitt C.J.
  • Diamond P.H.
  • Gürcan Özgür D.
  • Hahm T.S.
  Physics of Plasmas, American Institute of Physics, 2010, 17, pp.112509. A kinetic generalization of a Taylor identity appropriate to a strongly magnetized plasma is derived. This relation provides an explicit link between the radial mixing of a fourdimensional (4D) gyrocenter fluid and the poloidal Reynolds stress. This kinetic analog of a Taylor identity is subsequently utilized to link the turbulent transport of poloidal momentum to the mixing of potential vorticity. A quasilinear calculation of the flux of potential vorticity is carried out, yielding diffusive, turbulent equipartition, and thermoelectric convective components. Self-consistency is enforced via the quasineutrality relation, revealing that for the case of a stationary small amplitude wave population, deviations from neoclassical predictions of poloidal rotation can be closely linked to the growth/damping profiles of the underlying drift wave microturbulence. (10.1063/1.3490253)
  DOI : 10.1063/1.3490253
• Solar wind turbulent spectrum from MHD to electron scales
  
  • Alexandrova O.
  • Saur J.
  • Lacombe C.
  • Mangeney A.
  • Schwartz S. J.
  • Mitchell J.
  • Grappin Roland
  • Robert Patrick
  , 2010, 1216, pp.144-147. Turbulent spectra of magnetic fluctuations in the free solar wind are studied from MHD to electron scales using Cluster observations. We discuss the problem of the instrumental noise and its influence on the measurements at the electron scales. We confirm the presence of a curvature of the spectrum ~expkrho<SUB>e</SUB> over the broad frequency range ~ [10,100] Hz, indicating the presence of a dissipation. Analysis of seven spectra under different plasma conditions show clearly the presence of a quasi-universal power-law spectrum at MHD and ion scales. However, the transition from the inertial range ~k<SUP>-1.7</SUP> to the spectrum at ion scales ~k<SUP>-2.7</SUP> is not universal. Finally, we discuss the role of different kinetic plasma scales on the spectral shape, considering normalized dimensionless spectra. (10.1063/1.3395821)
  DOI : 10.1063/1.3395821
• Determination of the averaged charge-to-mass ratio of the heavy charged constituents of a magnetoplasma using whistler wave measurements
  
  • Krafft C.
  • Lundin B. V.
  Annales Geophysicae, European Geosciences Union, 2010, 28, pp.2237-2247. In a cold magnetized plasma with two light ions of comparable gyrofrequencies and any species of heavy ions and/or charged dust particulates, a technique is developed to recover the relative charge density of the heavy plasma population and to estimate its effective averaged charge-to-mass ratio. Such results can be obtained without using mass spectrometer data but only the measurements of the ion plasma frequency, the electron gyro- and plasma frequencies as well as the two highest ion cutoff frequencies. (10.5194/angeo-28-2237-2010)
  DOI : 10.5194/angeo-28-2237-2010
• Evidence of atomic adsorption on TiO<SUB>2</SUB> under plasma exposure and related C<SUB>2</SUB>H<SUB>2</SUB> 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)&#10913;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
• A model for the self-pulsing regime of microhollow cathode discharges
  
  • Chabert Pascal
  • Lazzaroni Claudia
  • Rousseau Antoine
  Journal of Applied Physics, American Institute of Physics, 2010, 108, pp.113307. Microhollow cathode discharges may operate in different regimes depending of the discharge current. They are subject to relaxation oscillations in the so-called self-pulsing regime in which the discharge oscillates between two quasiequilibria: at low current it remains confined in the microhole whereas it expands on the cathode backside during short high-current pulses. A model based on a nonlinear discharge resistance is proposed to describe the phenomenon. The analysis of the dynamics reveals that the current pulse rises in an extremely short time while the characteristic (longer) decay time is imposed by the resistance when the discharge is expanded outside the hole. It is shown how the nonlinear discharge resistance may be inferred from the experimental current-voltage signals. (10.1063/1.3518533)
  DOI : 10.1063/1.3518533
• Evidence for surface oxidation on Pyrex of NO into NO<SUB>2</SUB> by adsorbed O atoms
  
  • Guaitella Olivier
  • Hübner M.
  • Welzel S.
  • Marinov Daniil
  • Röpcke J.
  • Rousseau Antoine
  Plasma Sources Science and Technology, IOP Publishing, 2010, 19, pp.045026. The surface of a Pyrex discharge tube was treated by a capacitively coupled RF plasma at low pressure. In cases where the plasma contained oxygen, O atoms deposition on the tube surface could be confirmed via the time-dependent conversion of NO to NO2 in a post-plasma experiment. Inside the discharge tube, the evolution of the concentrations of NO and of NO2 was measured using quantum cascade laser absorption spectroscopy in the mid-infrared spectral range. The surface density of atomic oxygen was estimated to be about 2 × 1014&#8201;cm&#8722;2 based on NO oxidation in the closed reactor. The production rate of NO2 is in the range of 2 × 1011&#8201;molecules&#8201;cm&#8722;3&#8201;s&#8722;1. (10.1088/0963-0252/19/4/045026)
  DOI : 10.1088/0963-0252/19/4/045026
• Une recherche ITER...ative
  
  • Hennequin Pascale
  Pour la science, Pour la Science, 2010 (392).
• Plasmas froids radiofréquence
  
  • Chabert Pascal
  • Raimbault Jean-Luc
  Images de la physique 2009, 2010, pp.p27. L'interaction d'un plasma froid faiblement ionisé et d'une surface semiconductrice est à l'origine des technologies de nanostructuration de la matière en microélectronique. Ces plasmas sont générés et entretenus par des champs électromagnétiques radiofréquence. La compréhension des mécanismes fondamentaux du couplage de l'énergie électromagnétique au plasma et de son transport vers les surfaces du réacteur est un enjeu majeur pour la maîtrise des procédés industriels utilisant les plasmas froids radiofréquence.
• Bilan et Perspective 2006 - 2009, Programme National Soleil Terre
  
  • Fontaine Dominique
  • Vilmer N.
  , 2010.
• 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
• 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
• 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
• Plasma assisted ignition and combustion
  
  • Starikovskaia Svetlana
  • Starikovskii A.Yu.
  , 2010, pp.71-93.
• 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&#8201;Pa involving the measurements of (i) N2(B) and N2(C) fluorescences for a discharge current I = 40&#8201;mA and a pulse duration &#964; = 200&#8201;µs and 10&#8201;ms, together with (ii) the absolute concentration of NO(X) for I = 40 and 80&#8201;mA with &#964; varying from 1 to 4&#8201;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 &#8804; v &#8804; 14) &#8594; N2(B) N2(X, v = 0), while the relaxation of N2(C) is dominated by the pooling reaction N2(A) N2(A) &#8594; 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&#8201;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
• 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
• 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
• Observation and theoretical modeling of electron scale solar wind turbulence
  
  • Sahraoui Fouad
  • Belmont Gérard
  • Goldstein M. L.
  • Kiyani K. H.
  • Robert Patrick
  • Canu Patrick
  , 2010.
• Wave-particle interactions in the equatorial source region of whistler-mode emissions
  
  • Santolík Ondrej
  • Gurnett D. A.
  • Pickett J. S.
  • Grimald S.
  • Décréau Pierrette
  • Parrot Michel
  • Cornilleau-Wehrlin Nicole
  • El-Lemdani Mazouz Farida
  • Schriver D.
  • Meredith N. P.
  • Fazakerley A.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2010, 115 (A8). Wave-particle interactions can play a key role in the process of transfer of energy between different electron populations in the outer Van Allen radiation belt. We present a case study of wave-particle interactions in the equatorial source region of whistler-mode emissions. We select measurements of the Cluster spacecraft when these emissions are observed in the form of random hiss with only occasional discrete chorus wave packets, and where the wave propagation properties are very similar to previously analyzed cases of whistler-mode chorus. We observe a positive divergence of the Poynting flux at minima of the magnetic field modulus along the magnetic field lines, indicating the central position of the source. In this region we perform a linear stability analysis based on the locally measured electron phase space densities. We find two unstable electron populations. The first of them consists of energy-dispersed and highly anisotropic injected electrons at energies of a few hundreds eV to a few keV, with the perpendicular temperature more than 10 times higher than the parallel temperature with respect to the magnetic field line. Another unstable population is formed by trapped electrons at energies above 10 keV. We show that the injected electrons at lower energies can be responsible for a part of the waves that propagate obliquely at frequencies above one half of the electron cyclotron frequency. Our model of the trapped electrons at higher energies gives insufficient growth of the waves below one half of the electron cyclotron frequency and a nonlinear generation mechanism might be necessary to explain their presence even in this simple case. (10.1029/2009JA015218)
  DOI : 10.1029/2009JA015218
• Plasmas de Fusion Magnétique
  
  • Hennequin Pascale
  Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.25-26. ISSN : 1775-0385
• Observations multi-satellitaires de l'interaction Vent Solaire - Magnétosphère
  
  • Sahraoui Fouad
  • Cornilleau-Wehrlin Nicole
  Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.33-34. ISSN : 1775-0385