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.
• 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.
• Physics of Stimulated L->H Transitions
  
  • Miki K.
  • Diamond P.H.
  • Hahn S. -H.
  • Xiao W. W.
  • Gürcan Özgür D.
  • Tynan G.R.
  Physical Review Letters, American Physical Society, 2013, 110, pp.195002. We report on model studies of stimulated L&#8594;H transitions. These studies use a novel reduced mesoscale model. Studies reveal that L&#8594;H transitions can be triggered by particle injection into a subcritical state (i.e., P<PThresh). Particle injection alters the edge mean flow shear via changes of density and temperature gradients. The change of edge mean flow shear is critical to turbulence collapse and the subsequent stimulated transition. For low ambient heating, strong injection is predicted to trigger a transient turbulence collapse. We predict that repetitive injection can maintain the turbulence collapse and so sustain a driven H-mode-like state. The total number of particles required to induce a transition by either injection or gas puffing is estimated. Results indicate that the total number of injected particles required is much smaller than that required for inducing a transition by gas puffing. Thus, we show that internal injection is more efficient than gas puffing of comparable strength. We also observe that zonal flows do not play a critical role in stimulated transitions. (10.1103/PhysRevLett.110.195002)
  DOI : 10.1103/PhysRevLett.110.195002
• Anisotropy of radiation emitted from planar wire arrays
  
  • Kantsyrev Viktor L.
  • Chuvatin Alexandre S.
  • Esaulov A. A.
  • Safronova Alla S.
  • Rudakov Leonid I.
  • Velikovich A. L.
  • Williamson Kenneth M.
  • Osborne Glenn C.
  • Shrestha I. K.
  • Weller Michael E.
  • Shlyaptseva V. V.
  Physics of Plasmas, American Institute of Physics, 2013, 20 (07), pp.070702. The planar wire array (PWA) is a promising load for new multi-source inertial confinement fusion (ICF) hohlraums [B. Jones et al. Phys. Rev. Lett. 104 125001 (2010)]. The hohlraum radiation symmetry is an important issue for ICF. It was found that extreme ultraviolet and sub-keV photon emission from PWAs may have considerable anisotropy in the load azimuthal plane. This experimental result is obtained on the UNR 11.7 MA Zebra generator. The time-dependent anisotropy effect is detected. This feature is studied in 2D numerical simulations and can be explained by initial anisotropy of implosion of those non-cylindrical loads radiating essentially as surface sources in sub-keV quanta and also by radiation absorption in cold magnetized plasma tails forming in the direction of magnetic compression. (10.1063/1.4817023)
  DOI : 10.1063/1.4817023
• Solar wind turbulence: the fight between the direct turbulent cascade and the (anisotropic) expansion
  
  • Grappin Roland
  , 2013.
• Various Coiled Magnetoimpedance Based on Differential Magnetic Permeability Variation
  
  • Moutoussamy Joël
  • Coillot C.
  • Chanteur Gérard
  • Alves Francisco
  Sensor letters, American Scientific Publishers, 2013, 11 (1), pp.40-43. The present work is focused on high sensitivity (5000 V/T) transverse coiled GMI transducers manufactured with various magnetic materials, magnetically excited at low frequencies (f < 50 kHz) by an insulated coil which is also used for the measurement of the DC and low frequency magnetic field. The impedance and the sensitivity of different types of ferromagnetic material as nanocrystalline ribbons (Finemet) annealed under longitudinal and transverse magnetic fields, as mumetal ribbons and Mn–Zn thin ferrite core are investigated with respect to the static magnetic field. From these results, the differential magnetic permeability is approximated in order to predict sensitivity behavior in relation to the anisotropy magnetic field and the magnitude and the frequency of current excitation. (10.1166/sl.2013.2800)
  DOI : 10.1166/sl.2013.2800
• 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
• On the origin of the quasi-perpendicular ion foreshock: Full-particle simulations
  
  • Savoini Philippe
  • Lembège Bertrand
  • Stienlet J.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118 (3), pp.1132-1145. Many space missions have already evidenced the existence of the ion foreshock region located upstream of the Earth's bow shock and populated by energetic backstreaming ions reflected by the shock front. In order to analyse this region, a curved shock is simulated with a 2-D particle-in-cell (PIC) code. The analysis is presently restricted to the quasi-perpendicular angular range defined by 45° ≤ θBn ≤ 90°. In agreement with experimental data, present results evidence two distinct ion populations back-streaming from the shock front along the interplanetary magnetic field: (i) the Field-Aligned Beam population (hereafter "FAB") and (ii) the gyrophase bunched population (hereafter "GPB") which differ from each other by their gyrotropic or non-gyrotropic behavior, respectively. Excluded by a simulation time which is too short, ion instabilities pitch-angle scattering cannot be the source of "GPB". Two new criteria are proposed to identify more precisely each population: their interaction time Δtint with the shock front and their downstream penetration depth. These criteria show that (i) the "FAB" population moves back and forth between the upstream edge of the shock front and the overshoot, and is characterized by a Δtint covering several upstream gyro-periods. (ii) In contrast, the "GPB" ions suffer a short interaction time (i.e. 1 < τci). We observe that the "FAB" ions may have different originsalthough all "GPB" ions seem to be produced by the electrostatic field built up at the shock and are emitted in a burst-like mode rather than in continuous way. (10.1002/jgra.50158)
  DOI : 10.1002/jgra.50158
• 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.
• A spectroscopic study of ethylene destruction and by-product generation using a three-stage atmospheric packed-bed plasma reactor
  
  • Hubner Antoine
  • Guaitella Olivier
  • Rousseau Antoine
  • Roepcke J.
  Journal of Applied Physics, American Institute of Physics, 2013, 114, pp.033301. Using a three-stage dielectric packed-bed plasma reactor at atmospheric pressure, the destruction of ethylene, a typical volatile organic compound, and the generation of major by-products have been studied by means of Fourier Transform Infrared Spectroscopy. A test gas mixture air at a gas flow of 1 slm containing 0.12% humidity with 0.1% ethylene has been used. In addition to the fragmentation of the precursor gas, the evolution of the concentration of ten stable reaction products, CO, CO2, O3, NO2, N2O, HCN, H2O, HNO3, CH2O, and CH2O2 has been monitored. The concentrations of the by-products range between 5&#8201;ppm, in the case of NO2, and 1200&#8201;ppm, for H2O. By the application of three sequentially working discharge cells at a frequency of f&#8201;=&#8201;4 kHz and voltage values between 9 and 12&#8201;kV, a nearly complete decomposition of C2H4 could be achieved. Furthermore, the influence of the specific energy deposition (SED) on the destruction process has been studied and the maximum value of SED was about 900 J l&#8722;1. The value of the characteristic energy &#946;, characterizing the energy efficiency of the ethylene destruction in the reactor, was found to be 330 J l&#8722;1. It was proven that the application of three reactor stages suppresses essentially the production of harmful by-products as formaldehyde, formic acid, and NO2 compared to the use of only one or two stages. Based on the multi-component detection, the carbon balance of the plasma chemical conversion of ethylene has been analyzed. The dependence of the fragmentation efficiencies of ethylene (RF(C2H4)&#8201;=&#8201;5.5&#8201;×&#8201;1019 molecules J&#8722;1) and conversion efficiencies to the produced molecular species (RC&#8201;=&#8201;(0.13)&#8201;×&#8201;1016 molecules J&#8722;1) on the discharge conditions could be estimated in the multistage plasma reactor. (10.1063/1.4813409)
  DOI : 10.1063/1.4813409
• 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
• Chlorine atom densities in the (3p<SUP>5</SUP>)<SUP>2</SUP> P<SUP>0</SUP><SUB>1/2</SUB> excited spin-orbit state measured by two-photon absorption laser-induced fluorescence in a chlorine inductively coupled plasma
  
  • Sirse Nishant
  • Booth Jean-Paul
  • Chabert Pascal
  • Surzhykov A.
  • Indelicato P.
  Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46 (29), pp.295203. Chlorine atom densities in the spinorbit excited state were measured by two-photon absorption laser-induced fluorescence (TALIF) in an inductively coupled plasma discharge in pure Cl2. The atoms were excited by two photons at 235.702 nm to the state and detected by fluorescence to the (4s) 4P5/2 state at 726 nm. The population of this state relative to that in the ground state, was determined from the relative TALIF signal intensity from the two states, combined with new calculations of the two-photon absorption cross-sections. was found to increase continuously with radio-frequency power (50500 W), whereas with Cl2 pressure (590 mTorr) it passes through a maximum at 10 mTorr, reaching ~30% at 500 W. This maximum corresponds to the maximum of electron density in the discharge. Combining this density ratio measurement with previous measurements of the absolute ground state chlorine atom density [1] allows the absolute spin-orbit excited state density to be estimated. A significant fraction of the total chlorine atom density is in this excited state which should be included in plasma chemistry models. (10.1088/0022-3727/46/29/295203)
  DOI : 10.1088/0022-3727/46/29/295203
• Spatio-temporal evolution of the H -> L back transition
  
  • Miki K.
  • Diamond P.H.
  • Schmitz L.
  • Mcdonald D. C.
  • Estrada T.
  • Gürcan Özgür D.
  • Tynan G.R.
  Physics of Plasmas, American Institute of Physics, 2013, 20 (6), pp.062304. Since ITER will operate close to threshold and with limited control, the H&#8201;&#8594;&#8201;L back transition is a topic important for machine operations as well as physics. Using a reduced mesoscale model [Miki et al., Phys. Plasmas 19, 092306 (2012)], we investigate ELM-free H&#8201;&#8594;&#8201;L back transition dynamics in order to isolate transport physics effects. Model studies indicate that turbulence spreading is the key process which triggers the back transition. The transition involves a feedback loop linking turbulence and profiles. The I-phase appears during the back transition following a slow power ramp down, while fast ramp-downs reveal a single burst of zonal flow during the back transition. The I-phase nucleates at the pedestal shoulder, as this is the site of the residual turbulence in H-mode. Hysteresis in the profile gradient scale length is characterized by the Nusselt number, where Nu = &#967;i,turb/&#967;i,neo. Relative hysteresis of temperature gradient vs density gradient is sensitive to the pedestal Prandtl number, where Prped = Dped/&#967;i,neo. We expect the H-mode to be somewhat more resilient in density than in temperature. (10.1063/1.4812555)
  DOI : 10.1063/1.4812555
• Microsecond ramp compression of a metallic liner driven by a 5 MA current on the SPHINX machine using a dynamic load current multiplier pulse shaping
  
  • d'Almeida Thierry
  • Lassalle Francis
  • Morell Alain
  • Grunenwald Julien
  • Zucchini Frédéric
  • Loyen Arnaud
  • Maysonnave Thomas
  • Chuvatin Alexandre S.
  Physics of Plasmas, American Institute of Physics, 2013, 20 (09), pp.092512. SPHINX is a 6 MA, 1-&#956;s Linear Transformer Driver (LTD) operated by the CEA Gramat (France) and primarily used for imploding Z-pinch loads for radiation effects studies. Among the options that are currently being evaluated to improve the generator performances are an upgrade to a 20&#8201;MA, 1-&#956;s LTD machine and various power amplification schemes, including a compact Dynamic Load Current Multiplier (DLCM). A method for performing magnetic ramp compression experiments, without modifying the generator operation scheme, was developed using the DLCM to shape the initial current pulse in order to obtain the desired load current profile. In this paper, we discuss the overall configuration that was selected for these experiments, including the choice of a coaxial cylindrical geometry for the load and its return current electrode. We present both 3-D Magneto-hydrodynamic and 1D Lagrangian hydrodynamic simulations which helped guide the design of the experimental configuration. Initial results obtained over a set of experiments on an aluminium cylindrical liner, ramp-compressed to a peak pressure of 23&#8201;GPa, are presented and analyzed. Details of the electrical and laser Doppler interferometer setups used to monitor and diagnose the ramp compression experiments are provided. In particular, the configuration used to field both homodyne and heterodyne velocimetry diagnostics in the reduced access available within the liner's interior is described. Current profiles measured at various critical locations across the system, particularly the load current, enabled a comprehensive tracking of the current circulation and demonstrate adequate pulse shaping by the DLCM. The liner inner free surface velocity measurements obtained from the heterodyne velocimeter agree with the hydrocode results obtained using the measured load current as the input. An extensive hydrodynamic analysis is carried out to examine information such as pressure and particle velocity history profiles or magnetic diffusion across the liner. The potential of the technique in terms of applications and achievable ramp pressure levels lies in the prospects for improving the DLCM efficiency through the use of a closing switch (currently under development), reducing the load dimensions and optimizing the diagnostics. (10.1063/1.4823720)
  DOI : 10.1063/1.4823720
• Autocalibration Method for Anisotropic Magnetoresistive Sensors Using Offset Coils
  
  • Mohamadabadi K.
  • Jeandet Alexis
  • Hillion M.
  • Coillot Christophe
  IEEE Sensors Journal, Institute of Electrical and Electronics Engineers, 2013, 13 (2), pp.772-776. In this paper, we present a zero-cost indoor calibration method for anisotropic magnetoresistive (AMR) sensors. The implemented circuit is designed to calibrate AMR sensors using integrated coils. A microcontroller is used to generate an artificial three-dimensional magnetic field by injecting three separate currents into three offset coils. We show the similarity of the results for residual calibration norm by using this method compared with the calibration of the sensor in free Earth's magnetic field. Furthermore, this method does not need any other instruments such as Helmholtz coils or a platform for rotating the sensor. Here the sensor is placed inside a mu-metal box during calibration, and the calibration process is completely autonomous. (10.1109/JSEN.2012.2227595)
  DOI : 10.1109/JSEN.2012.2227595