Publications

2013

• In situ observations of high-Mach number collisionless shocks in space plasmas
  
  • Masters A.
  • Stawarz L.
  • Fujimoto M.
  • Schwartz S. J.
  • Sergis N.
  • Thomsen M. F.
  • Retinò Alessandro
  • Hasegawa H.
  • Zieger B.
  • Lewis G. R.
  • Coates A. J.
  • Canu Patrick
  • Dougherty M. K.
  Plasma Physics and Controlled Fusion, IOP Publishing, 2013, 55 (12), pp.124035. Shock waves are widespread in collisionless space plasmas throughout the Universe. How particles are accelerated at these shocks has been the subject of much research attention. The dominant source of the high-energy particles that pervade our Galaxy (cosmic rays) is thought to be the high-Mach number collisionless shocks that form around young supernova remnants, but it is unclear how much the lower Mach number collisionless shock waves frequently encountered by spacecraft in Solar System space plasmas can tell us about particle acceleration in the higher Mach number regime. Here we review recent studies of the shock wave that stands in the solar wind in front of the planet Saturn (Saturn's bow shock), based on Cassini spacecraft observations. This review represents a new direction of shock physics research, with the potential to bridge the gap between Solar System and astrophysical shocks. These studies have confirmed that Saturn's bow shock is one of the strongest shocks in the Solar System, and a recent discovery indicates that electron acceleration at high-Mach numbers may occur irrespective of the upstream magnetic field geometry. This is important because astrophysical shocks can often only be studied remotely via emissions associated with accelerated electrons. We discuss possible future directions of this emerging sub-field of collisionless space plasma shock physics. (10.1088/0741-3335/55/12/124035)
  DOI : 10.1088/0741-3335/55/12/124035
• Interplanetary Nanodust Detection by the Solar Terrestrial Relations Observatory/WAVES Low Frequency Receiver
  
  • Le Chat G.
  • Zaslavsky A.
  • Meyer-Vernet N.
  • Issautier K.
  • Belheouane S.
  • Pantellini F.
  • Maksimovic M.
  • Zouganelis I.
  • Bale S. D.
  • Kasper J. C.
  Solar Physics, Springer Verlag, 2013, 286 (2), pp.549-559. New measurements using radio and plasma-wave instruments in interplanetary space have shown that nanometer-scale dust, or nanodust, is a significant contributor to the total mass in interplanetary space. Better measurements of nanodust will allow us to determine where it comes from and the extent to which it interacts with the solar wind. When one of these nanodust grains impacts a spacecraft, it creates an expanding plasma cloud, which perturbs the photoelectron currents. This leads to a voltage pulse between the spacecraft body and the antenna. Nanodust has a high charge/mass ratio, and therefore can be accelerated by the interplanetary magnetic field to the speed of the solar wind: significantly faster than the Keplerian orbital speeds of heavier dust. The amplitude of the signal induced by a dust grain grows much more strongly with speed than with mass of the dust particle. As a result, nanodust can produce a strong signal despite its low mass. The WAVES instruments on the twin Solar TErrestrial RElations Observatory spacecraft have observed interplanetary nanodust particles since shortly after their launch in 2006. After describing a new and improved analysis of the last five years of STEREO/WAVES Low Frequency Receiver data, we present a statistical survey of the nanodust characteristics, namely the rise time of the pulse voltage and the flux of nanodust. We show that previous measurements and interplanetary dust models agree with this survey. The temporal variations of the nanodust flux are also discussed. (10.1007/s11207-013-0268-x)
  DOI : 10.1007/s11207-013-0268-x
• In Situ Cassini Spacecraft Observations of Turbulence in Saturn's Magnetosheath
  
  • Hadid L. Z.
  • Sahraoui Fouad
  • Retinò Alessandro
  • Modolo Ronan
  • Canu Patrick
  • Jackman C. M.
  • Masters A.
  • Dougherty M. K.
  • Gurnett D. A.
  , 2013, 8, pp.EPSC2013-1056. Throughout this work we investigate, the properties of turbulence in the Magnetosheath of Saturn. To do so, we computed Power Spectral Densities (PSD) based on Cassini interplanetary magnetic field data between 2004 and 2007. As a preliminary result, we show the absence of the Kolmogorov scale ~ f-5/3 in the inertial range whereas only the f-1 scale is present.
• On the reactivity of plasma-treated photo-catalytic TiO<SUB>2</SUB> surfaces for oxidation of C<SUB>2</SUB>H<SUB>2</SUB> and CO
  
  • Lopatik D.
  • Marinov Daniil
  • Guaitella Olivier
  • Rousseau Antoine
  • Roepcke J.
  Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46, pp.255203. The objective of this study is to understand fundamental aspects of interactions of plasmas with catalytic surfaces. Based on this approach the reactivity of plasma treated and stimulated catalytic surfaces of TiO2 is studied by analysing the oxidation (i) of C2H2 to CO and CO2 and (ii) of CO to CO2. The inner surface of a Pyrex discharge tube is coated with TiO2 films impregnated with TiO2 nanoparticles, which provides a surface area of about 4 m2. In addition to the exposure of the TiO2 surface by low-pressure radio-frequency plasmas using O2, Ar or N2 (f = 13.56 MHz, p = 0.53 mbar, P = 17 W) the surfaces are stimulated by heating and UV radiation treatment. The temporal development of the concentrations of the precursor gases C2H2 or CO and of the reaction products is monitored using quantum cascade laser absorption spectroscopy, which provides multi-component detection in the mid-infrared spectral range. The C2H2 concentration was found to be nearly constant over time after a pre-treatment with Ar or N2 discharges using an initial gas mixture of 1% C2H2 in Ar. However, a strong decay of the concentration of C2H2 is observed for pure O2 plasma pre-treatment. In general, the decay is found to be nearly exponential with time constant in the order of about 10 min. The reactive adsorption of C2H2 molecules on the inner surface of the tube reactor showed a density of about 7.5 × 1012 C2H2 molecules cm&#8722;2. This behaviour demonstrates that the reaction (\rm O_\rm ads \rm C_2 \rm H_2)_\rm TiO_2 produces some adsorbed intermediates, which can be thermally or photo-catalytically oxidized to CO2. In contrast, when 1% CO in Ar is used as an initial gas mixture no adsorption processes on the TiO2 surface could be detected. An effective destruction of CO took part via photo-catalytic oxidation. (10.1088/0022-3727/46/25/255203)
  DOI : 10.1088/0022-3727/46/25/255203
• Controlled deposition of sulphur-containing semiconductor and dielectric nano-structured films on metals in SF<SUB>6</SUB> ion-ion plasma
  
  • Rafalskyi D.V.
  • Bredin Jérôme
  • Aanesland Ane
  Journal of Applied Physics, American Institute of Physics, 2013, 114 (21), pp.213303. In the present paper, the deposition processes and formation of films in SF6 ion-ion plasma, with positive and negative ion flows accelerated to the surface, are investigated. The PEGASES (acronym for Plasma Propulsion with Electronegative GASES) source is used as an ion-ion plasma source capable of generating almost ideal ion-ion plasma with negative ion to electron density ratio more than 2500. It is shown that film deposition in SF6 ion-ion plasma is very sensitive to the polarity of the incoming ions. The effect is observed for Cu, W, and Pt materials. The films formed on Cu electrodes during negative and positive ion assisted deposition were analyzed. Scanning electron microscope analysis has shown that both positive and negative ion fluxes influence the copper surface and leads to film formation, but with different structures of the surface: the low-energy positive ion bombardment causes the formation of a nano-pored film transparent for ions, while the negative ion bombardment leads to a continuous smooth insulating film. The transversal size of the pores in the porous film varies in the range 50500&#8201;nm, and further analysis of the film has shown that the film forms a diode together with the substrate preventing positive charge drain, and positive ions are neutralized by passing through the nano-pores. The film obtained with the negative ion bombardment has an insulating surface, but probably with a multi-layer structure: destroying the top surface layer allows to measure similar diode IV-characteristics as for the nano-pored film case. Basing on results, practical conclusions for the probes and electrodes cleaning in ion-ion SF6 plasmas have been made. Different applications are proposed for the discovered features of the controlled deposition from ion-ion plasmas, from Li-sulphur rechargeable batteries manufacturing and nanofluidics issues to the applications for microelectronics, including low-k materials formation. (10.1063/1.4842915)
  DOI : 10.1063/1.4842915
• Hysteresis effects in the formation of a neutralizing beam plasma at low ion energy
  
  • Rafalskyi D.V.
  • Aanesland Ane
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2013, 104 (3), pp.35004. In this paper, the PEGASES II thruster prototype is used as an ion source generating low-energy positive Ar ion beam, extracted without an external neutralizer. The ions are extracted and accelerated from the source using a two-grid system. The extracted positive ion beam current is measured on a large beam target that can be translated along the acceleration axis. The ion beam current shows a stepwise transition from a low-current to a high-current extraction regime with hysteresis. The hysteresis region depends strongly upon the beam target position. Langmuir probe measurements in the plume show high plasma potentials and low plasma densities in the low-current mode, while the plasma potential drops and the density increases in the high-current mode. The ion energy distribution functions of the beam are measured for different regimes of ion extraction. The ion beam extracted in the high-current mode is indicated by the presence of an additional low-energy peak corresponding to ions from an ion-beam plasma created in the downstream chamber, as well as 1020 times higher intensity of the primary ion beam peak. The hysteresis behavior is explained by the formation of a downstream neutralizing beam plasma, that depends on the target position and pressure in agreement with a Paschen-like breakdown by secondary electrons. The obtained results are of high relevance for further development of the PEGASES thruster, as well as for improving existing neutralizer-free concepts of the broad-beam ion sources. (10.1209/0295-5075/104/35004)
  DOI : 10.1209/0295-5075/104/35004
• Progress on theoretical issues in modelling turbulent transport
  
  • Kosuga Y.
  • Diamond P.H.
  • Wang L.
  • Gürcan Özgür D.
  • Hahm T.S.
  Nuclear Fusion, IOP Publishing, 2013, 53 (4), pp.043008. We discuss theoretical progress in turbulent transport modelling in tokamaks. In particular, we address issues that the conventional quasilinear type calculation cannot confront, such as (i) the nature of turbulence in the edge-core coupling region of tokamaks (i.e. the so-called no mans land'), and the dynamics of incoming structures coupled to zonal flows, (ii) nonlinear dynamics of zonal flows and (iii) transport by drift wave turbulence with strong waveparticle interaction. A unifying theme of these studies is their formulation in terms of the phase space density correlation evolution. (10.1088/0029-5515/53/4/043008)
  DOI : 10.1088/0029-5515/53/4/043008
• How the Propagation of Heat-Flux Modulations Triggers ExB Flow Pattern Formation
  
  • Kosuga Y.
  • Diamond P.H.
  • Gürcan Özgür D.
  Physical Review Letters, American Physical Society, 2013, 110, pp.105002. We propose a novel mechanism to describe E×B flow pattern formation based upon the dynamics of propagation of heat-flux modulations. The E×B flows of interest are staircases, which are quasiregular patterns of strong, localized shear layers and profile corrugations interspersed between regions of avalanching. An analogy of staircase formation to jam formation in traffic flow is used to develop an extended model of heat avalanche dynamics. The extension includes a flux response time, during which the instantaneous heat flux relaxes to the mean heat flux, determined by symmetry constraints. The response time introduced here is the counterpart of the drivers response time in traffic, during which drivers adjust their speed to match the background traffic flow. The finite response time causes the growth of mesoscale temperature perturbations, which evolve to form profile corrugations. The length scale associated with the maximum growth rate scales as &#916;2&#8764;(vthi/&#955;Ti)&#961;i&#8730;&#967;neo&#964;, where &#955;Ti is a typical heat pulse speed, &#967;neo is the neoclassical thermal diffusivity, and &#964; is the response time of the heat flux. The connection between the scale length &#916;2 and the staircase interstep scale is discussed. (10.1103/PhysRevLett.110.105002)
  DOI : 10.1103/PhysRevLett.110.105002
• Transport of radial heat flux and second sound in fusion plasmas
  
  • Gürcan Özgür D.
  • Diamond P.H.
  • Garbet X.
  • Berionni Vincent
  • Dif-Pradalier Guilhem
  • Hennequin Pascale
  • Morel Pierre
  • Kosuga Y.
  • Vermare Laure
  Physics of Plasmas, American Institute of Physics, 2013, 20, pp.022307. Simple flux-gradient relations that involve time delay and radial coupling are discussed. Such a formulation leads to a rather simple description of avalanches and may explain breaking of gyroBohm transport scaling. The generalization of the flux-gradient relation (i.e., constitutive relation), which involve both time delay and spatial coupling, is derived from drift-kinetic equation, leading to kinetic definitions of constitutive elements such as the flux of radial heat flux. This allows numerical simulations to compute these cubic quantities directly. The formulation introduced here can be viewed as an extension of turbulence spreading to include the effect of spreading of cross-phase as well as turbulence intensity, combined in such a way to give the flux. The link between turbulence spreading and entropy production is highlighted. An extension of this formulation to general quasi-linear theory for the distribution function in the phase space of radial position and parallel velocity is also discussed. (10.1063/1.4792161)
  DOI : 10.1063/1.4792161
• Cell death induced on cell cultures and nude mouse skin by non-thermal, nanosecond-pulsed generated plasma
  
  • Duval Arnaud
  • Marinov Ilya
  • Bousquet Guilhem
  • Gapihan Guillaume
  • Starikovskaia Svetlana
  • Rousseau Antoine
  • Janin Anne
  PLoS ONE, Public Library of Science, 2013, 8 (12), pp.e83001. Non-thermal plasmas are gaseous mixtures of molecules, radicals, and excited species with a small proportion of ions and energetic electrons. Non-thermal plasmas can be generated with any high electro-magnetic field. We studied here the pathological effects, and in particular cell death, induced by nanosecond-pulsed high voltage generated plasmas homogeneously applied on cell cultures and nude mouse skin. In vitro, Jurkat cells and HMEC exhibited apoptosis and necrosis, in dose-dependent manner. In vivo, on nude mouse skin, cell death occurred for doses above 113 J/cm(2) for the epidermis, 281 J/cm(2) for the dermis, and 394 J/cm(2) for the hypodermis. Using electron microscopy, we characterized apoptosis for low doses and necrosis for high doses. We demonstrated that these effects were not related to thermal, photonic or pH variations, and were due to the production of free radicals. The ability of cold plasmas to generate apoptosis on cells in suspension and, without any sensitizer, on precise skin areas, opens new fields of application in dermatology for extracorporeal blood cell treatment and the eradication of superficial skin lesions. (10.1371/journal.pone.0083001)
  DOI : 10.1371/journal.pone.0083001
• Fine-structure-resolved electron collisions from chlorine atoms in the (3p<SUP>5</SUP>)<SUP>2</SUP>P<SUB>3/2</SUB><SUP>o</SUP> and (3p<SUP>5</SUP>)<SUP>2</SUP>P<SUB>1/2</SUB><SUP>o</SUP> states
  
  • Wang Yang
  • Zatsarinny Oleg
  • Bartschat Klaus
  • Booth Jean-Paul
  Physical Review A : Atomic, molecular, and optical physics [1990-2015], American Physical Society, 2013, 87, pp.022703. The B-spline R-matrix method is employed to calculate elastic electron scattering from chlorine atoms in the (3p5)2P3/2,1/2o states and electron-induced collisions between these two finestructure levels. The polarizability of the target states is accounted for by including polarized pseudostates in the close-coupling expansion, while relativistic effects are treated at the level of the semirelativistic Breit-Pauli approximation. We find the Ramsauer minimum in the elastic channels at a significantly lower projectile energy (&#8776;0.2 eV) than previous calculations, due to an apparent strong sensitivity of the theoretical predictions on the details of the model, especially the target structure. The present results are relevant to the determination of chlorine atomic densities in Cl2-containing industrial plasma etch reactors. (10.1103/PhysRevA.87.022703)
  DOI : 10.1103/PhysRevA.87.022703
• Solar wind fluctuations and solar wind activity long-term swing 1963-2012
  
  • Zerbo J.-L.
  • Amory-Mazaudier Christine
  • Ouattara Frédéric Martial
  , 2013, 1301161.
• Vibrational relaxation of N2 on catalytic surfaces studied by infrared titration with time resolved Quantum Cascade Laser diagnostics
  
  • Marinov Daniil
  • Guaitella Olivier
  • Lopatik D.
  • Hübner M.
  • Ionikh Y.
  • Roepcke J.
  • Rousseau Antoine
  , 2013.
• Radiation from Ag High Energy Density Z-pinch Plasmas with Applications to Lasing
  
  • Weller M. E.
  • Safronova Alla S.
  • Kantsyrev Viktor L.
  • Esaulov A. A.
  • Shrestha Ishor
  • Apruzese J. P.
  • Giuliani J. L.
  • Chuvatin Alexandre S.
  • Stafford A.
  • Keim S. F.
  • Shlyaptseva V. V.
  • Osborne Glenn C.
  • Petkov E. E.
  , 2013.
• Azimuthal directions of equatorial noise propagation determined using 10 years of data from the Cluster spacecraft
  
  • Nemec F.
  • Santolík O.
  • Pickett J. S.
  • Hrbackova Z.
  • Cornilleau-Wehrlin Nicole
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118, pp.7160-7169. Equatorial noise (EN) emissions are electromagnetic waves at frequencies between the proton cyclotron frequency and the lower hybrid frequency routinely observed within a few degrees of the geomagnetic equator at radial distances from about 2 to 6 R<SUB>E</SUB>. They propagate in the extraordinary (fast magnetosonic) mode nearly perpendicularly to the ambient magnetic field. We conduct a systematic analysis of azimuthal directions of wave propagation, using all available Cluster data from 2001 to 2010. Altogether, combined measurements of the Wide-Band Data and Spectrum Analyzer of the Spatio-Temporal Analysis of Field Fluctuations instruments allowed us to determine azimuthal angle of wave propagation for more than 100 EN events. It is found that the observed propagation pattern is mostly related to the plasmapause location. While principally isotropic azimuthal directions of EN propagation were detected inside the plasmasphere, wave propagation in the plasma trough was predominantly found directed to the West or East, perpendicular to the radial direction. The observed propagation pattern can be explained using a simple propagation analysis, assuming that the emissions are generated close to the plasmapause. (10.1002/2013JA019373)
  DOI : 10.1002/2013JA019373
• A double-plasma source of continuous bipolar ion-ion beam
  
  • Dudin S.V.
  • Rafalskyi D.V.
  Applied Physics Letters, American Institute of Physics, 2013, 102, pp.034102. A double-plasma source capable of the generation of a continuous bipolar ion-ion beam is described. The quasi-neutral ion-ion flow to an extraction electrode is formed in the system containing primary inductively coupled plasma separated from a secondary plasma by an electrostatic grid-type filter. The total current of each ion species to the 250&#8201;mm diameter extraction electrode is about 80&#8201;mA; the electron current does not exceed 30% of the ion current. Method of positive/negative ion current ratio control is proposed, allowing the ion currents ratio variation in wide range. (10.1063/1.4788711)
  DOI : 10.1063/1.4788711
• ROLE OF REACTOR CAPACITANCE ON THE PROPAGATION OF IONISATION WAVES
  
  • Guaitella Olivier
  • Sobota Ana
  • Rousseau Antoine
  , 2013.
• Direction for the future - Successive acceleration of positive and negative ions applied to space propulsion
  
  • Aanesland Ane
  • Bredin Jérôme
  • Popelier Lara
  • Chabert Pascal
  , 2013 (CERN-2013-007).
• Nonturbulent stabilization of ion fluxes by the fan instability
  
  • Krafft C.
  • Volokitin A.
  Physics Letters A, Elsevier, 2013, 377 (16-17), pp.1189-1198. Resonant interactions between energetic ion fluxes and wave packets they excite through fan instability are studied using self-consistent 3D simulations to explain the nonlinear wave-particle mechanisms at work and to estimate the energy lost by the flux and its sharing between wave emission and particle heating. The saturation of waves and the relaxation of particles are studied over long time periods. The ions are not only diffusing in the waves but are also trapped simultaneously by several potential wells of large amplitude overlapping waves. Estimates of the ion heating energy and rate are given and compared with space observations. (10.1016/j.physleta.2013.03.011)
  DOI : 10.1016/j.physleta.2013.03.011
• Dipolarization fronts as a consequence of transient reconnection: In situ evidence
  
  • Fu H.S.
  • Cao J.B.
  • Khotyaintsev Y. V.
  • Sitnov M. I.
  • Runov A.
  • Fu S. Y.
  • Hamrin M.
  • André M.
  • Retinò Alessandro
  • Ma Y. D.
  • Lu H. Y.
  • Wei X.H.
  • Huang S. Y.
  Geophysical Research Letters, American Geophysical Union, 2013, 40 (23), pp.6023-6027. Dipolarization fronts (DFs) are frequently detected in the Earth's magnetotail from XGSM&#8201;=&#8201;&#8722;30 RE to XGSM&#8201;=&#8201;&#8722;7 RE. How these DFs are formed is still poorly understood. Three possible mechanisms have been suggested in previous simulations: (1) jet braking, (2) transient reconnection, and (3) spontaneous formation. Among these three mechanisms, the first has been verified by using spacecraft observation, while the second and third have not. In this study, we show Cluster observation of DFs inside reconnection diffusion region. This observation provides in situ evidence of the second mechanism: Transient reconnection can produce DFs. We suggest that the DFs detected in the near-Earth region (XGSM&#8201;>&#8201;&#8722;10 RE) are primarily attributed to jet braking, while the DFs detected in the mid- or far-tail region (XGSM&#8201;<&#8201;&#8722;15 RE) are primarily attributed to transient reconnection or spontaneous formation. In the jet-braking mechanism, the high-speed flow pushes the preexisting plasmas to produce the DF so that there is causality between high-speed flow and DF. In the transient-reconnection mechanism, there is no causality between high-speed flow and DF, because the frozen-in condition is violated. (10.1002/2013GL058620)
  DOI : 10.1002/2013GL058620
• Comparison between hybrid and fully kinetic models of asymmetric magnetic reconnection: Coplanar and guide field configurations
  
  • Aunai Nicolas
  • Hesse Michael
  • Zenitani Seiji
  • Kuznetsova M. M.
  • Black Carrie
  • Evans Rebekah
  • Smets Roch
  Physics of Plasmas, American Institute of Physics, 2013, 20, pp.022902. Magnetic reconnection occurring in collisionless environments is a multi-scale process involving both ion and electron kinetic processes. Because of their small mass, the electron scales are difficult to resolve in numerical and satellite data, it is therefore critical to know whether the overall evolution of the reconnection process is influenced by the kinetic nature of the electrons, or is unchanged when assuming a simpler, fluid, electron model. This paper investigates this issue in the general context of an asymmetric current sheet, where both the magnetic field amplitude and the density vary through the discontinuity. A comparison is made between fully kinetic and hybrid kinetic simulations of magnetic reconnection in coplanar and guide field systems. The models share the initial condition but differ in their electron modeling. It is found that the overall evolution of the system, including the reconnection rate, is very similar between both models. The best agreement is found in the guide field system, which confines particle better than the coplanar one, where the locality of the moments is violated by the electron bounce motion. It is also shown that, contrary to the common understanding, reconnection is much faster in the guide field system than in the coplanar one. Both models show this tendency, indicating that the phenomenon is driven by ion kinetic effects and not electron ones. (10.1063/1.4792250)
  DOI : 10.1063/1.4792250
• Asymmetric distribution of reconnection jet fronts in the Jovian nightside magnetosphere
  
  • Kasahara S.
  • Kronberg E. A.
  • Kimura T.
  • Tao C.
  • Badman S. V.
  • Masters A.
  • Retinò Alessandro
  • Krupp N.
  • Fujimoto M.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2013, 118, pp.375-384. Magnetic reconnection plays important roles in mass transport and energy conversion in planetary magnetospheres. It is considered that transient reconnection causes localized auroral arcs or spots in the Jovian magnetosphere, by analogy to the case in the Earth's magnetosphere. However, the local structures of transient reconnection events (i.e., magnetospheric plasma parameters) and their spatial distribution have not been extensively investigated for the Jovian magnetosphere. Here we examine plasma velocity and density during strong north-south magnetic field events in the Jovian nightside magnetosphere, which may be associated with tail reconnection. We find prominent reconnection jet fronts predominantly on the dawnside of the nightside magnetosphere, which would be a signature unique to rotation-dominant planetary magnetospheres. The observed plasma structures are consistent with significant field-aligned currents which would generate localized aurora. (10.1029/2012JA018130)
  DOI : 10.1029/2012JA018130
• Ozone kinetics in low-pressure discharges: vibrationally excited ozone and molecule formation on surfaces
  
  • Marinov Daniil
  • Guerra V.
  • Guaitella Olivier
  • Booth Jean-Paul
  • Rousseau Antoine
  Plasma Sources Science and Technology, IOP Publishing, 2013, 22, pp.055018. A combined experimental and modeling investigation of the ozone kinetics in the afterglow of pulsed direct current discharges in oxygen is carried out. The discharge is generated in a cylindrical silica tube of radius 1 cm, with short pulse durations between 0.5 and 2 ms, pressures in the range 15 Torr and discharge currents &#8764;40120 mA. Time-resolved absolute concentrations of ground-state atoms and ozone molecules were measured simultaneously in situ, by two-photon absorption laser-induced fluorescence and ultraviolet absorption, respectively. The experiments were complemented by a self-consistent model developed to interpret the results and, in particular, to evaluate the roles of vibrationally excited ozone and of ozone formation on surfaces. It is found that vibrationally excited ozone, O&#8727; 3, plays an important role in the ozone kinetics, leading to a decrease in the ozone concentration and an increase in its formation time. In turn, the kinetics of O&#8727; 3 is strongly coupled with those of atomic oxygen and O2(a 1g) metastables. Ozone formation at the wall does not contribute significantly to the total ozone production under the present conditions. Upper limits for the effective heterogeneous recombination probability of O atoms into ozone are established. (10.1088/0963-0252/22/5/055018)
  DOI : 10.1088/0963-0252/22/5/055018
• Design and Testing of a Surface Switch for the Dynamic Load Current Multiplier on the SPHINX Microsecond LTD
  
  • Maysonnave Thomas
  • Bayol Frédéric
  • Demol Gauthier
  • d'Almeida Thierry
  • Morell Alain
  • Lassalle Francis
  • Grunenwald Julien
  • Chuvatin Alexandre S.
  • Pecastaing Laurent
  • de Ferron Antoine Silvestre
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2013, 41 (10), pp.2593 - 2599. SPHINX is a microsecond linear transformer driver located at Atomic Energy Comission (CEA) Gramat (France), which can deliver a current pulse of 6 MA within 800 ns in a Z -pinch load. Using the concept of the dynamic load current multiplier (DLCM), which was proposed by Chuvatin, we expect to increase the load current above 6 MA, while decreasing its rise time to ~ 300 ns. The DLCM developed by the CEA Gramat and International Technologies for High Pulsed Power (ITHPP) is a compact system made up of concentric electrodes (autotransformer), a dynamic flux extruder (cylindrical wire array), a vacuum convolute (eight post-hole rods), and a closing switch (compact vacuum surface switch). The latter is a key component of the system, which is used to prevent the current from flowing into the load until the inductance builds up due to the implosion of the wire array. This paper presents the design and testing of the DLCM surface switch, resulting from both electrostatic simulations and experiments on the SPHINX generator. These studies, carried out either with or without load (open circuit), were valuable for a first experimental evaluation of the DLCM scheme in a microsecond regime and provided detailed information on the surface switch behavior. (10.1109/TPS.2013.2245148)
  DOI : 10.1109/TPS.2013.2245148
• Localizing Transport Barriers in Degenerate 3/2 D.O.F. Hamiltonian Systems with Applications to Magnetic Confinement Fusion
  
  • Constantinescu D.
  • Firpo Marie-Christine
  International journal of bifurcation and chaos in applied sciences and engineering, World Scientific Publishing, 2013, 23, pp.1350034. The existence of transport barriers in 3/2 degrees of freedom degenerate Hamiltonian systems is studied using the associated stroboscopic maps. For small enough amplitudes of the perturbations, a transport barrier (formed by infinitely many invariant rotational circles) is proven to exist and to form in the degenerate annulus. These results are applied to Hamiltonian models which describe some magnetic configurations in tokamak plasmas. Read More: http://www.worldscientific.com/doi/abs/10.1142/S021812741350034X (10.1142/S021812741350034X)
  DOI : 10.1142/S021812741350034X