Publications

2013

• Cascade and dissipation from MHD to electron scale turbulence in the solar wind
  
  • Sahraoui Fouad
  , 2013.
• On the nature, scaling and anisotropy of kinetic turbulence in the solar wind
  
  • Sahraoui Fouad
  • Huang S. Y.
  • Belmont Gérard
  • Goldstein M. L.
  • Kiyani K. H.
  • Retinò Alessandro
  , 2013.
• Nanosecond discharges at liquid interfaces; applications to biological treatment
  
  • Rousseau Antoine
  , 2013.
• Turbulence dans les Tokamaks
  
  • Morel Pierre
  , 2013.
• A model for the radiofrequency sheath with arbitrary waveforms
  
  • Chabert Pascal
  • Turner Miles
  , 2013.
• Tailored Voltage Waveform Capacitively-Coupled Plasmas for IEDF and electron density control: Application to Microcrystalline Si Deposition
  
  • Booth Jean-Paul
  • Johnson Erik
  • Lafleur Trevor
  • Delattre Pierre-Alexandre
  , 2013. Oral
• Modelling of atmospheric pressure capacitive microdischarges in He/O<SUB>2</SUB>
  
  • Chabert Pascal
  • Lazzaroni Claudia
  • Lieberman M.A.
  • Lichtenberg A.J.
  , 2013.
• Space Weather and Ground Space Based technologies
  
  • Amory-Mazaudier Christine
  , 2013.
• OZONE KINETICS IN LOW-PRESSURE DISCHARGES
  
  • Guerra V.
  • Marinov Daniil
  • Booth Jean-Paul
  • Guaitella Olivier
  • Rousseau Antoine
  , 2013.
• Study of fast gas heating in a capillary nanosecond discharge in air. TALIF O atoms measurements and kinetic modeling (AIAA 2013-0574)
  
  • Klochko A.V.
  • Lemainque J.
  • Popov N.A.
  • Booth Jean-Paul
  • Starikovskaia Svetlana
  , 2013.
• Time-resolved electric field measurements in nanosecond surface dielectric discharge. Comparison of different polarities. Ignition of combustible mixtures by surface discharge in rapid compression machine (AIAA 2013-1053)
  
  • Stepanyan S.A.
  • Boumehdi M.A.
  • Vanhove G.
  • Starikovskaia Svetlana
  , 2013. Surface nanosecond dielectric barrier discharge has been studied in air and at pressures ranging from 1 to 5 bar, with a coaxial geometry of the electrodes for positive and negative polarities of the high-voltage pulses. Pulses of a 24-55 kV amplitude on the electrode, positive or negative polarity, 20 ns duration, 0.5 ns rise time and 10 Hz repetitive frequency were used to initiate the discharge. ICCD images of the discharge development have been taken with a 2 ns gate. In the case of discharges in nitrogen, the emissions of molecular bands of the first negative and second positive systems of molecular nitrogen have been measured, and the dependence of their ratio versus pressure and distance from the high-voltage electrode has been analyzed. A comparison of the discharge development has been made in the case of negative and positive polarities at the high-voltage electrode. Ignition delay times under the action of a high-voltage nanosecond discharge have been studied and compared with autoignition delays in a rapid compression machine (RCM). The nanosecond Surface Dielectric Barrier Discharge (SDBD) was initiated in a quasi-uniform radial geometry in the proximity of the end plate of the combustion chamber of the RCM. Experiments were performed for methane and n-butane containing mixtures diluted by Ar or N2 for temperatures and pressures at the end of compression respectively ranging from 650 to 1000 K and 6 to 16 bar. A significant decrease of the ignition delay time is observed, when compared to autoignition experiments. The possibility to ignite lean mixtures is demonstrated. Preliminary experiments in the region of negative temperature coefficient for stoichiometric n-butane:oxygen mixture diluted with argon, are performed. The threshold voltage for plasma ignition, over which the ignition delay is decreased, is studied for different mixtures.
• Commutation rapide déclenchée par filamentation laser femtoseconde
  
  • Larour Jean
  • Arantchouk Léonid
  • Houard Aurélien
  Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2013, 15, pp.55-57. La revue scientifique de l'Ecole polytechnique (parution annuelle) ISSN : 1775-0385 Le phénomène de filamentation laser dans lair a été décrit dans un précédent numéro (Flash X n° 12) par A. Houard et A. Mysyrowicz, chercheurs du LOA (Laboratoire dOptique appliquée). Rappelons ici quil apparaît spontanément le long dun faisceau laser de durée femtoseconde (fs) quand sa puissance dépasse un seuil critique de quelques GW. un équilibre dynamique entre la diffraction naturelle du faisceau, leffet Kerr, et la défocalisation par lair ionisé, maintient lintensité dans le coeur du faisceau sur une distance qui peut dépasser un mètre, entraînant la formation dun canal de plasma dans le sillage de limpulsion. Le point de démarrage, la longueur des canaux de plasma et leur distribution transverse sont contrôlables en jouant sur les paramètres de limpulsion laser initiale (énergie, durée, diamètre du faisceau).
• Study of reconnection physics using laser-generated B fields
  
  • Smets Roch
  • Belmont Gérard
  • Aunai N.
  • Fuchs J. C.
  • Boniface C.
  • Aulanier G.
  , 2013.
• Structures of dayside whistler-mode waves deduced from conjugate diffuse aurora
  
  • Nishimura Y.
  • Bortnik J.
  • Li W.
  • Thome R.M.
  • Ni B.
  • Lyons L.R.
  • Angelopoulos V.
  • Ebihara Y.
  • Bonnell J. W.
  • Le Contel Olivier
  • Auster U.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118 (2), pp.664-673. [1] We present simultaneous measurements of dayside diffuse aurora and whistler-mode waves made by the South Pole all-sky imager and two of the THEMIS spacecraft. We found a high correlation between the diffuse aurora intensity at 557.7&#8201;nm near the footprint latitudes of THEMIS and whistler-mode wave intensity measured on board. The power in other wave modes was negligibly small in most cases, indicating that the dayside diffuse aurora is driven by precipitating energetic electrons resonating with whistler-mode waves. The high correlation over a wide L* range (6&#8201;<&#8201;L*&#8201;<&#8201;11) further allowed us to magnetically link the wave and magnetospheric plasma distributions with the auroral patterns. Two distinct regions of whistler-mode waves and ambient plasma density were found outside the plasmasphere near the equator: (1) intense waves in a smooth, low density and (2) moderate waves with enhanced and fluctuating density. The whistler-mode wave intensity in the fluctuating plasma density region is positively correlated with the ambient density variations. The corresponding auroral images show an azimuthally elongated diffuse auroral band on the field lines connected to the low density region, as opposed to a structured diffuse aurora on the fluctuating density field lines. Each structured diffuse auroral patch was stable for a few tens of minutes and slowly drifted azimuthally. The high correlation of waves and auroras indicates that the structured diffuse auroral pattern reflects the spatial distribution of whistler-mode waves and ambient plasma density in space. The enhanced density measured by the spacecraft is quasi-spatial and contributes to enhanced growth of whistler-mode waves. (10.1029/2012JA018242)
  DOI : 10.1029/2012JA018242
• Statistical properties of planetary heavy-ion precipitations toward the Martian ionosphere obtained from Mars Express
  
  • Hara T.
  • Seki K.
  • Futaana Y.
  • Yamauchi M.
  • Barabash S.
  • Fedorov A. O.
  • Yagi M.
  • Delcourt Dominique C.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118 (8), pp.5348-5357. The interplanetary magnetic field (IMF) embedded in the solar wind interacts with the Martian crustal magnetic field and atmosphere. The IMF orientation is one of the important parameters to control the acceleration and precipitation of planetary heavy ions (PHIs). We statistically investigate the effects of the IMF orientation on PHI precipitations toward the ionosphere based on observations by Mars Express (MEX). We identified 59 PHI precipitation events between July 2007 and September 2009. To estimate the IMF orientation without magnetometer that MEX does not carry, we used the velocity distribution of exospheric-origin pickup protons. We estimated the IMF orientation without its polarity for 10 events. The results show that the precipitations of PHIs tend to be observed around pole regions in the MSE (Mars-centered, solar electrical) coordinates determined from the solar wind electric field (Esw), in which the pole axis directs to the parallel or antiparallel to Esw due to the ambiguity in the IMF polarity determination. The observed precipitating PHIs are accelerated only up to a few keV. This feature may reflect the short distance from the picked-up region. For one of these 10 events, we estimated the IMF polarity by comparing the velocity distribution of exospheric-origin pickup protons observed by MEX with those obtained from statistical trajectory tracing simulations under two cases of possible IMF polarity conditions. The estimated polarity indicates that the PHI precipitation in this event is observed in the downward electric field hemisphere in MSE, where Esw points to Mars in the pole region. (10.1002/jgra.50494)
  DOI : 10.1002/jgra.50494
• Capacitively coupled radio-frequency plasmas excited by tailored voltage waveforms
  
  • Lafleur Trevor
  • Delattre Pierre-Alexandre
  • Johnson E.V.
  • Booth Jean-Paul
  Plasma Physics and Controlled Fusion, IOP Publishing, 2013, 55 (12), pp.124002. By applying certain types of ?tailored? voltage waveforms (TVWs) to capacitively coupled plasmas, a dc self-bias and an asymmetric plasma response can be produced, even in geometrically symmetric reactors. Furthermore, these arbitrary applied waveforms can produce a number of interesting phenomena that are not present in typical single-frequency sinusoidal discharges. This electrical asymmetry effect presents emerging possibilities for the improved control of the ion energy and ion flux in these systems; parameters of vital importance to both etching and deposition applications for materials processing. With a combined research approach utilizing both experimental measurements, and particle-in-cell simulations, we review and extend recent investigations that study a particular class of TVW. The waveforms used have a pulse-type shape and are composed of a varying number of harmonic frequencies. This allows a strong self-bias to be produced, and causes most of the applied voltage to be dropped across a single sheath. Additionally, decreasing the pulse width (by increasing the number of harmonics), allows the plasma density and ion flux to be increased. Simulation and experimental results both demonstrate that this type of waveform can be used to separately control the ion flux and ion energy, while still producing a uniform plasma over large area (50 cm diameter) rf electrodes. (10.1088/0741-3335/55/12/124002)
  DOI : 10.1088/0741-3335/55/12/124002
• Theory for the self-bias formation in capacitively coupled plasmas excited by arbitrary waveforms
  
  • Lafleur Trevor
  • Chabert Pascal
  • Turner M.M.
  • Booth Jean-Paul
  Plasma Sources Science and Technology, IOP Publishing, 2013, 22 (6), pp.065013. We develop a semi-analytical theory for the self-bias formation in capacitively coupled plasmas excited by arbitrary radio-frequency (rf) waveforms. The requirement of rf current continuity and voltage balance across the discharge results in the need for a self-bias voltage to develop with non-sinusoidal excitations, even in geometrically symmetric systems. The theory is compared extensively with a wide range of experimental and particle-in-cell (PIC) simulation data within the literature, and is found to be in excellent agreement. Furthermore, it is shown that the present theory is formally equivalent to the original model proposed by Heil et al (2008 J. Phys. D: Appl. Phys. 41 165202), but goes further by explicitly allowing the time-varying sheath voltages and symmetry parameter to be evaluated without input from PIC simulations. (10.1088/0963-0252/22/6/065013)
  DOI : 10.1088/0963-0252/22/6/065013
• Simulation benchmarks for low-pressure plasmas: Capacitive discharges
  
  • Turner M.M.
  • Derzsi A.
  • Donkó Z.
  • Eremin D.
  • Kelly S.J.
  • Lafleur Trevor
  • Mussenbrock T.
  Physics of Plasmas, American Institute of Physics, 2013, 20, pp.013507. Benchmarking is generally accepted as an important element in demonstrating the correctness of computer simulations. In the modern sense, a benchmark is a computer simulation result that has evidence of correctness, is accompanied by estimates of relevant errors, and which can thus be used as a basis for judging the accuracy and efficiency of other codes. In this paper, we present four benchmark cases related to capacitively coupled discharges. These benchmarks prescribe all relevant physical and numerical parameters. We have simulated the benchmark conditions using five independently developed particle-in-cell codes. We show that the results of these simulations are statistically indistinguishable, within bounds of uncertainty that we define. We, therefore, claim that the results of these simulations represent strong benchmarks, which can be used as a basis for evaluating the accuracy of other codes. These other codes could include other approaches than particle-in-cell simulations, where benchmarking could examine not just implementation accuracy and efficiency, but also the fidelity of different physical models, such as moment or hybrid models. We discuss an example of this kind in the Appendix. Of course, the methodology that we have developed can also be readily extended to a suite of benchmarks with coverage of a wider range of physical and chemical phenomena. (10.1063/1.4775084)
  DOI : 10.1063/1.4775084
• Anomalous collisionality in low-pressure plasmas
  
  • Lafleur Trevor
  • Chabert Pascal
  • Turner M.M.
  • Booth Jean-Paul
  Physics of Plasmas, American Institute of Physics, 2013, 20 (12), pp.124503. Based on a theoretical argument from fundamental kinetic theory, by way of simple worked examples, and through the use of particle-in-cell simulations of capacitively coupled plasmas, we demonstrate that conventional methods for calculating the momentum transfer collision frequency in low-pressure plasmas can be seriously erroneous. This potentially plays an important and previously unconsidered role in many low-pressure discharges, and at least in part provides a possible explanation for anomalous behaviour often encountered in these plasmas. (10.1063/1.4859155)
  DOI : 10.1063/1.4859155
• Action diffusion and lifetimes of quasistationary states in the Hamiltonian Mean Field model
  
  • Ettoumi Wahb
  • Firpo Marie-Christine
  Physical Review E, American Physical Society (APS), 2013, 87, pp.030102(R). Out-of-equilibrium quasistationary states (QSSs) are one of the signatures of a broken ergodicity in long-range interacting systems. For the widely studied Hamiltonian Mean-Field model, the lifetime of some QSSs has been shown to diverge with the number N of degrees of freedom with a puzzling N¹.7 scaling law, contradicting the otherwise widespread N scaling law. It is shown here that this peculiar scaling arises from the locality properties of the dynamics captured through the computation of the diffusion coefficient in terms of the action variable. The use of a mean first passage time approach proves to be successful in explaining the non-trivial scaling at stake here, and sheds some light on another case, where lifetimes diverging as e^N above some critical energy have been reported. (10.1103/PhysRevE.87.030102)
  DOI : 10.1103/PhysRevE.87.030102
• Interaction of plasma transport and turbulence on particle fuelling
  
  • Tamain Patrick
  • Bonhomme Gérard
  • Brochard Frédéric
  • Clairet Frédéric
  • Gil C.
  • Gunn J.
  • Hennequin P.
  • Hornung G.
  • Segui J. L.
  • Vermare L.
  • Ghendrih Philippe
  • Team Tore Supra
  Journal of Nuclear Materials, Elsevier, 2013, 438 (S), pp.S148-S154. We report the results of an experimental investigation of the impact of Supersonic Molecular Beam Injection in the Tore Supra tokamak. Several diagnostics were synchronised with the injection to extract a global picture of the physics at play from the time scale of turbulence (similar to 10 mu s) to the full-recovery time (similar to 1 s). As previously reported, a strong impact of the injection on density and temperature profiles is observed. Both fields exhibit a complex dynamic response involving different phases and time scales. In particular, we show that the effective particle fuelling efficiency is determined by a period of degraded confinement that follows the injection, during which the edge density collapses, in some cases, lower than the initial one. This phase is characterised by a dramatic change in the turbulent transport, with a drop of the frequency spectrum and the observation of large coherent structures as opposed to small intermittent fluctuations before the injection. (10.1016/j.jnucmat.2013.01.023)
  DOI : 10.1016/j.jnucmat.2013.01.023
• Nonlinear saturation of wave packets excited by low-energy electron horseshoe distributions
  
  • Krafft C.
  • Volokitin A.
  Physical Review E, American Physical Society (APS), 2013, 87, pp.053107. Horseshoe distributions are shell-like particle distributions that can arise in space and laboratory plasmas when particle beams propagate into increasing magnetic fields. The present paper studies the stability and the dynamics of wave packets interacting resonantly with electrons presenting low-energy horseshoe or shell-type velocity distributions in a magnetized plasma. The linear instability growth rates are determined as a function of the ratio of the plasma to the cyclotron frequencies, of the velocity and the opening angle of the horseshoe, and of the relative thickness of the shell. The nonlinear stage of the instability is investigated numerically using a symplectic code based on a three-dimensional Hamiltonian model. Simulation results show that the dynamics of the system is mainly governed by wave-particle interactions at Landau and normal cyclotron resonances and that the high-order normal cyclotron resonances play an essential role. Specific features of the dynamics of particles interacting simultaneously with two or more waves at resonances of different natures and orders are discussed, showing that such complex processes determine the main characteristics of the wave spectrum's evolution. Simulations with wave packets presenting quasicontinuous spectra provide a full picture of the relaxation of the horseshoe distribution, revealing two main phases of the evolution: an initial stage of wave energy growth, characterized by a fast filling of the shell, and a second phase of slow damping of the wave energy, accompanied by final adjustments of the electron distribution. The influence of the density inhomogeneity along the horseshoe on the wave-particle dynamics is also discussed. (10.1103/PhysRevE.87.053107)
  DOI : 10.1103/PhysRevE.87.053107
• CLUSTER observation of polar electron precipitation above the polar caps during periods of Northward IMF
  
  • Fontaine Dominique
  • Maggiolo R.
  AGU Fall Meeting Abstracts, AGU, 2013, 21, pp.07. The CLUSTER spacecraft revealed the presence of successive current sheets of opposite polarity above the polar caps during periods of northward or weak IMF. We first present the general electrodynamical context. At CLUSTER altitude (5-7 RE), the upward part of this current system consists of ion beams accelerated by quasi-static electric fields, associated with precipitating electrons. They are surrounded by low energy upflowing electron beams carrying a downward current. We then focus on the precipitating electrons above the polar cap which form acceleration structures at about 100 - 300 eV. This acceleration is interpreted as the effect of an electrostatic potential along magnetic field lines located above CLUSTER altitude, i.e. typically above 5-7 RE. We present statistics on the characteristics of these precipitating electron structures and we discuss the source regions and the mechanisms possibly at their origin.
• Building small scales in MHD turbulence
  
  • Verdini Andrea
  • Grappin Roland
  • Pinto Rui
  • Velli Marco
  , 2013, 1539, pp.74-77. Magneto-hydrodynamic turbulence (MHD) with a mean large-scale field is known to produce an anisotropic cascade, with energy mostly in perpendicular scales. We use a shell-model version of the Reduced MHD equations to simulate turbulence in homogeneous periodic conditions, in coronal loops, and in the solar wind. We compare the perpendicular and parallel spectra and show that different regimes of weak turbulence develop in loops and in the solar wind. We briefly comment on the way their characteristic large-scale features influence the weak turbulence spectra and their transition to strong turbulence. (10.1063/1.4810993)
  DOI : 10.1063/1.4810993
• Goniopolarimetry with Coupled Electric and Magnetic Measurements
  
  • Cecconi B.
  • Gautier A.-L.
  • Bergman J.E.S
  • Chust Thomas
  • Marchaudon A.
  • Cavoit C.
  • Santolík O.
  , 2013.