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/O2
- 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.
Isopropanol saturated TiO2 surface regeneration by non-thermal plasma : Influence of air relative humidity
- Sivachandiran Loganathan
- Thévenet Frédéric
- Gravejat Paul
- Rousseau Antoine
Chemical Engineering Journal, Elsevier, 2013, 214, pp.17-26. Environmental regulation on air quality requires the development of energetic efficient volatile organic compounds (VOCs) abatement techniques. Adsorption, photocatalysis, non-thermal plasma and their combinations have been widely studied for VOC treatment. Even if the plasma material (sorbent or catalyst) association appears as one of the most efficient configuration for VOC removal, it mainly consists in operating continuously the discharge on the material surface as long as the effluent flows across the reactor. This work aims at investigating another approach of plasma material association for VOC removal: in a first step, the material is used as a sorbent until the complete coverage of adsorption sites; in a second step, once VOC saturation is achieved, the discharge is ignited on the material surface. During both steps, the influence of air relative humidity (RH) is investigated in order to evaluate its impact on the process. The objectives of our approach are: (i) the reduction of energy consumption; (ii) the increase of sorbent life-times by efficient regeneration; (iii) the investigation of plasma interaction with VOC saturated materials; (iv) the investigation of air RH influence on such VOC treatment process. A packed bed reactor coated with TiO2 has been designed. IPA is used as a model VOC. First, injected power in the packed-bed reactor is characterized as a function of air RH. Complete coverage of TiO2 surface over 35% RH is suggested as a significant parameter. Then, adsorption of IPA on TiO2 was monitored until IPA breakthrough. The amount of IPA adsorbed per TiO2 surface unit is compared to values reported by other authors. The influence of air RH on reversibly and irreversibly adsorbed IPA fractions is investigated. Over 35% RH irreversible adsorption is favored, adsorption modes are discussed. Plasma regeneration of IPA saturated TiO2 surface leads simultaneously to IPA desorption and mineralization. Increasing air RH favors IPA mineralization and diminishes acetone production. Carbon balance obtained after 1 h plasma treatment reaches 91% in the presence of 50% RH. A thermal treatment is performed after each plasma treatment in order to evidence plasma insensitive adsorbed species and to restore TiO2 initial surface state. 97% of the carbon balance is collected under 50% RH after thermal treatment. During the thermal step, acetone and CO2 are mainly produced, their formation pathways are discussed. (10.1016/j.cej.2012.10.022)
DOI : 10.1016/j.cej.2012.10.022
Influence of the dissipation mechanism on collisionless magnetic reconnection in symmetric and asymmetric current layers
- Aunai Nicolas
- Hesse Michael
- Black Carrie
- Evans Rebekah
- Kuznetsova M. M.
Physics of Plasmas, American Institute of Physics, 2013, 20, pp.2901. Numerical studies implementing different versions of the collisionless Ohm's law have shown a reconnection rate insensitive to the nature of the non-ideal mechanism occurring at the X line, as soon as the Hall effect is operating. Consequently, the dissipation mechanism occurring in the vicinity of the reconnection site in collisionless systems is usually thought not to have a dynamical role beyond the violation of the frozen-in condition. The interpretation of recent studies has, however, led to the opposite conclusion that the electron scale dissipative processes play an important dynamical role in preventing an elongation of the electron layer from throttling the reconnection rate. This work re-visits this topic with a new approach. Instead of focusing on the extensively studied symmetric configuration, we aim to investigate whether the macroscopic properties of collisionless reconnection are affected by the dissipation physics in asymmetric configurations, for which the effect of the Hall physics is substantially modified. Because it includes all the physical scales a priori important for collisionless reconnection (Hall and ion kinetic physics) and also because it allows one to change the nature of the non-ideal electron scale physics, we use a (two dimensional) hybrid model. The effects of numerical, resistive, and hyper-resistive dissipation are studied. In a first part, we perform simulations of symmetric reconnection with different non-ideal electron physics. We show that the model captures the already known properties of collisionless reconnection. In a second part, we focus on an asymmetric configuration where the magnetic field strength and the density are both asymmetric. Our results show that contrary to symmetric reconnection, the asymmetric model evolution strongly depends on the nature of the mechanism which breaks the field line connectivity. The dissipation occurring at the X line plays an important role in preventing the electron current layer from elongating and forming plasmoids. (10.1063/1.4795727)
DOI : 10.1063/1.4795727
On the supply of heavy planetary material to the magnetotail of Mercury
- Delcourt Dominique C.
Annales Geophysicae, European Geosciences Union, 2013, 31 (10), pp.1673-1679. We examine the transport of low-energy heavy ions of planetary origin (O + , Na + , Ca +) in the magneto-sphere of Mercury. We show that, in contrast to Earth, these ions are abruptly energized after ejection into the magneto-sphere due to enhanced curvature-related parallel acceleration. Regardless of their mass-to-charge ratio, the parallel speed of these ions is rapidly raised up to ∼ 2 V E×B (denoting by V E×B the magnitude of the local E × B drift speed), in a like manner to Fermi-type acceleration by a moving magnetic mirror. This parallel energization is such that ions with very low initial energies (a few tenths of eVs) can overcome gravity and, regardless of species or convection rate, are transported over comparable distances into the night-side magnetosphere. The region of space where these ions reach the magnetotail is found to extend over altitudes similar to those where enhanced densities are noticeable in the MESSENGER data, viz., from ∼ 1000 km up to ∼ 6000 km in the pre-midnight sector. The observed density enhancements may thus follow from E × B related focusing of planetary material of dayside origin into the magnetotail. Due to the planetary magnetic field offset, an asymmetry is found between drift paths anchored in the Northern and Southern hemispheres, which puts forward a predominant role of heavy material originating in the Northern Hemisphere in populating the innermost region of Mercury's magnetotail. (10.5194/angeo-31-1673-2013)
DOI : 10.5194/angeo-31-1673-2013
Plasma/surface interaction: example of air plasmas and plasma bullets
- Guaitella Olivier
, 2013.
Cavitation in the vicinity of the high-voltage electrode as a key step of nanosecond breakdown in liquids
- Marinov Ilya
- Guaitella Olivier
- Rousseau Antoine
- Starikovskaia Svetlana
Plasma Sources Science and Technology, IOP Publishing, 2013, 22, pp.042001. Fast shadowgraphy of nanosecond discharge in liquids with different dielectric permittivity, namely in water, ethanol and n-pentane, has been performed. Formation of a gas cavity at a nanosecond time scale was observed as a pre-breakdown phenomenon at amplitudes of the high-voltage pulse close to the breakdown threshold. This phenomenon is considered as a possible key step of high-voltage breakdown in polar liquids. (10.1088/0963-0252/22/4/042001)
DOI : 10.1088/0963-0252/22/4/042001
Negative ion extraction from hydrogen plasma bulk
- Oudini N.
- Taccogna F.
- Minelli P.
- Aanesland Ane
- Raimbault Jean-Luc
Physics of Plasmas, American Institute of Physics, 2013, 20 (10), pp.103506. A two-dimensional particle-in-cell/Monte Carlo collision model has been developed and used to study low electronegative magnetized hydrogen plasma. A configuration characterized by four electrodes is used: the left electrode is biased at Vl = −100 V, the right electrode is grounded, while the upper and lower transversal electrodes are biased at an intermediate voltage Vud between 0 and −100 V. A constant and homogeneous magnetic field is applied parallel to the lateral (left/right) electrodes. It is shown that in the magnetized case, the bulk plasma potential is close to the transversal electrodes bias inducing then a reversed sheath in front of the right electrode. The potential drop within the reversed sheath is controlled by the transversal electrodes bias allowing extraction of negative ions with a significant reduction of co-extracted electron current. Furthermore, introducing plasma electrodes, between the transversal electrodes and the right electrode, biased with a voltage just above the plasma bulk potential, increases the negative ion extracted current and decreases significantly the co-extracted electron current. The physical mechanism on basis of this phenomenon has been discussed. (10.1063/1.4825246)
DOI : 10.1063/1.4825246
Space Research in Africa. Some Achievements from 2007 to 2012
- Amory-Mazaudier Christine
- Fleury Rolland
Sun and Geosphere, BBC SWS Regional Network, 2013, 2 (8), pp.65-70. This article presents the results of a research network Europe Africa established in 1995 after the International Electrojet Equatorial Year (1992-1994). During the last decade, this research network has been involved in two international projects: the International Heliophysical Year (2007-2009) and International Space Weather Initiative (2010-2012).The participation in these international projects increased the number of PhD and multiplied the number of scientific papers. Many scientific results have been obtained. Teaching and working methods have been also developed. We emphasize in this article the last two points.
Direct observation of ozone formation on SiO2 surfaces in O2 discharges
- Marinov Daniil
- Guaitella Olivier
- Booth Jean-Paul
- Rousseau Antoine
Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46, pp.032001. Ozone production is studied in a pulsed O2 discharge at pressures in the range 1.36.7 mbar. Time-resolved absolute concentrations of O3 and O are measured in the post-discharge using UV absorption spectroscopy and two-photon absorption laser-induced fluorescence. In a bare silica discharge tube ozone is formed mainly by three-body gas-phase recombination. When the tube surface is covered by a high specific surface silica catalyst heterogeneous formation becomes the main source of ozone. The efficiency of this surface process increases with O2 pressure and is favoured by the presence of OH groups and adsorbed H2O on the surface. At p = 6.7 mbar ozone production accounts for up to 25% of the atomic oxygen losses on the surface. (10.1088/0022-3727/46/3/032001)
DOI : 10.1088/0022-3727/46/3/032001
Dynamics of tilted eddies in a transversal flow at the edge of tokamak plasmas and the consequences for L-H transition
- Fedorczak N.
- Ghendrih Philippe
- Hennequin Pascale
- Tynan G.R.
- Diamond P.H.
- Manz P.
Plasma Physics and Controlled Fusion, IOP Publishing, 2013, 55 (12), pp.124024. The dynamical interaction between eddies and shear flow is investigated through a simplified model of vorticity conservation with tilted eddies. Energy is transferred either to the flow or to eddies, depending on the eddy tilt with respect to the flow shear. When eddies are tilted in the shear direction, the system is favorable to shear increase: tilt instability (TI) or the negative viscosity phenomenon. When eddies are tilted in the opposite direction, the shear flow is damped via a Kelvin-Helmholtz (KH) process. The TI generally dominates the interaction on the largest radial scale, but a fraction of the energy cascades to smaller radial scales through the alternation of tilting and KH dynamics. Within this eddy description, we show that the symmetry breaking required to generate a net residual stress is set by the intrinsic eddy tilt. We recall that magnetic shear can provide an intrinsic tilt to ballooning modes at the edge of tokamak plasmas, with an orientation which depends on flux surface geometry. In L-mode weak shear regimes, this residual stress can dominate the Reynolds stress. Coupled to momentum sources acting in the scrape-off layer, it can induce a significant difference of the edge radial electric field between lower single null and upper single null geometries. A comparison with experimental profiles measured across the edge of Tore Supra L-mode plasmas is discussed. (10.1088/0741-3335/55/12/124024)
DOI : 10.1088/0741-3335/55/12/124024
Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair
- Décréau Pierrette
- Kougblénou S.
- Lointier G.
- Rauch Jean-Louis
- Trotignon Jean-Gabriel
- Vallières X.
- Canu Patrick
- Rochel Grimald S.
- El-Lemdani Mazouz Farida
- Darrouzet F.
Annales Geophysicae, European Geosciences Union, 2013, 31 (11), pp.2097-2121. The Cluster mission operated a "tilt campaign" during the month of May 2008. Two of the four identical Cluster spacecraft were placed at a close distance (~50 km) from each other and the spin axis of one of the spacecraft pair was tilted by an angle of ~46°. This gave the opportunity, for the first time in space, to measure global characteristics of AC electric field, at the sensitivity available with long boom (88 m) antennas, simultaneously from the specific configuration of the tilted pair of satellites and from the available base of three satellites placed at a large characteristic separation (~1 RE). This paper describes how global characteristics of radio waves, in this case the configuration of the electric field polarization ellipse in 3-D-space, are identified from in situ measurements of spin modulation features by the tilted pair, validating a novel experimental concept. In the event selected for analysis, non-thermal continuum (NTC) waves in the 15-25 kHz frequency range are observed from the Cluster constellation placed above the polar cap. The observed intensity variations with spin angle are those of plane waves, with an electric field polarization close to circular, at an ellipticity ratio e = 0.87. We derive the source position in 3-D by two different methods. The first one uses ray path orientation (measured by the tilted pair) combined with spectral signature of magnetic field magnitude at source. The second one is obtained via triangulation from the three spacecraft baseline, using estimation of directivity angles under assumption of circular polarization. The two results are not compatible, placing sources widely apart. We present a general study of the level of systematic errors due to the assumption of circular polarization, linked to the second approach, and show how this approach can lead to poor triangulation and wrong source positioning. The estimation derived from the first method places the NTC source region in the dawn sector, at a large L value (L ~ 10) and a medium geomagnetic latitude (35° S). We discuss these untypical results within the frame of the geophysical conditions prevailing that day, i.e. a particularly quiet long time interval, followed by a short increase of magnetic activity. (10.5194/angeo-31-2097-2013)
DOI : 10.5194/angeo-31-2097-2013
Radio-frequency capacitively coupled plasmas excited by tailored voltage waveforms: comparison of experiment and particle-in-cell simulations
- Delattre Pierre-Alexandre
- Lafleur Trevor
- Johnson Erik
- Booth Jean-Paul
Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46, pp.235201. Using a range of different diagnostics we have performed a detailed experimental characterization of a capacitively coupled rf plasma discharge excited by tailored voltage waveforms in argon (3?13 Pa). The applied pulse-type tailored waveforms consist of between 1 and 5 harmonics (with a fundamental of 15 MHz), and are used to generate an electrically asymmetric plasma response, manifested by the formation of a strong dc bias in the geometrically symmetric reactor used. Experimental measurements of the dc bias, electron density, ion current density, ion-flux energy distributions at the electrodes and discharge current waveforms, are compared with a one-dimensional particle-in-cell simulation for the same operating conditions. The experimental and simulation results are found to be in good agreement over the range of parameters investigated, and demonstrate a number of unique features present with pulse-type tailored waveforms, including: increased plasma density and ion flux with the number of harmonics, and a broader control range of the ion bombarding energy. (10.1088/0022-3727/46/23/235201)
DOI : 10.1088/0022-3727/46/23/235201
ECH effects on toroidal rotation: KSTAR experiments, intrinsic torque modelling and gyrokinetic stability analyses
- Shi Y. J.
- Ko W. H.
- Kwon J.M.
- Diamond P.H.
- Lee S. G.
- Ko S. H.
- Wang L.
- Yi Sukyoung
- Ida K.
- Terzolo L.
- Yoon S. W.
- Lee K. D.
- Lee J. H.
- Nam U. N.
- Bae Y. S.
- Oh Y. K.
- Kwak J. G.
- Bitter M.
- Hill K.
- Gürcan Özgür D.
- Hahm T.S.
Nuclear Fusion, IOP Publishing, 2013, 53 (11). Toroidal rotation profiles have been investigated in KSTAR H-mode plasma using combined auxiliary heating by co-neutral beam injection (NBI) and electron cyclotron resonance heating (ECH). The ion temperature and toroidal rotation are measured with x-ray imaging crystal spectroscopy and charge exchange recombination spectroscopy. H-mode plasma is achieved using co-current 1.3MW NBI, and a 0.35MW ECH pulse is added to the flat-top of H-mode. The core rotation profiles, which are centrally peaked in the pure NBI heating phase, flatten when ECH is injected, while the edge pedestal is unchanged. Dramatic decreases in the core toroidal rotation values (Delta V-tor/V-tor similar to -30%) are observed when on-axis ECH is added to H-mode. The experimental data show that the decrease of core rotation velocity and its gradient are correlated with the increase of core electron temperature and its gradient, and also with the likely steepening of the density gradient. We thus explore the viability of a hypothesized ITG (ITG ion temperature gradient instability) -> TEM (trapped electron mode instability) transition as the explanation of the observed counter-current flow induced by ECH. However, the results of linear microstability analyses using inferred profiles suggest that the TEM is excited only in the deep core, so the viability of the hypothesized explanation is not yet clear. (10.1088/0029-5515/53/11/113031)
DOI : 10.1088/0029-5515/53/11/113031
Theory of a Strip Loop Antenna Located on the Surface of an Axially Magnetized Plasma Column
- Kudrin A. V.
- Zaitseva Anna S
- Zaboronkova T. M.
- Krafft C.
- Kyriacou George A
Progress In Electromagnetics Research B, EMW Publishing, 2013, 51, pp.221--246. We study the current distribution and input impedance of a circular loop antenna in the form of an infinitesimally thin, perfectly conducting narrow strip coiled into a ring. The antenna is located on the surface of an axially magnetized plasma column surrounded by a homogeneous isotropic medium. The current in the antenna is excited by a time-harmonic voltage creating an electric field with the azimuthal component in a gap of small angular opening on the strip surface. The emphasis is placed on the solution of the integral equations for the azimuthal harmonics of the antenna current in the case where the magnetoplasma inside the column is nonresonant. The properties of the kernels of the integral equations are discussed and the current distribution in the antenna is obtained. It is shown that the presence of a magnetized plasma column can significantly influence the electrodynamic characteristics of the antenna compared with the case where it is located in the surrounding medium or a homogeneous plasma medium the parameters of which coincide with those inside the column. (10.2528/PIERB13032304)
DOI : 10.2528/PIERB13032304
Effects of the surface conductivity and the IMF strength on the dynamics of planetary ions in Mercury's magnetosphere
- Seki Kanako
- Terada Naoki
- Yagi Manabu
- Delcourt Dominique C.
- Leblanc François
- Ogino Tatsuki
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118 (6), pp.3233-3242. To examine the effects of planetary surface conductivity and the southward IMF strength on ion dynamics, systematic trajectory tracings of Na+ ions were performed in the electric and magnetic field configurations obtained from magnetohydrodynamics (MHD) simulations of the solar wind-Mercury interaction. Comparison with a previous study, which used an analytical model that rescaled the Earth's magnetosphere and assumed the existence of the distant neutral line (DNL) in Mercury's magnetotail, shows a drastic change in the Na+ precipitation pattern onto due to the formation of the near-Mercury neutral line (NMNL) in MHD simulations. The Na+ precipitation band at approximately 30 degrees of latitude (LAT), which was obtained in the previous study, disappeared in the equivalent low-conductivity MHD case due to the NMNL formation, while the NMNL formation causes high-energy Na+ precipitation in the equatorial region. The change in strength of the southward IMF (sBz) alters the location of the NMNL and the Na+ precipitation pattern. In the low-conductivity sBz = 5 case, both the equatorial precipitation and the Na+ band at approximately LAT = 30 are formed. In the high-conductivity sBz = 5 case, magnetospheric convection through the polar regions is suppressed, which results in a region of dense Na+ near the planet. These results suggest that the precipitation pattern of planetary ions onto Mercury's surface changes significantly with the activity level of Mercury's magnetosphere. It is also suggested that observations of the magnetospheric convection, the distribution of Na+ ions around the planet, or the precipitation pattern of Na+ ions onto the planetary surface can provide us information about the surface conductivity. (10.1002/jgra.50181)
DOI : 10.1002/jgra.50181

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