Publications

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Below, by year, are the publications listed in the HAL open archive.

2013

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
Electrical characteristics of micro-hollow cathode discharges
- Lazzaroni Claudia
- Chabert Pascal
Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46, pp.455203. A cathode sheath model of micro-hollow cathode discharges is proposed to calculate the voltagecurrent characteristics and discuss the physics of the discharge resistance. Three different approaches are compared: (i) a self-consistent model where the electric field is determined self-consistently with the electron flux, (ii) a matrix sheath model where the electric field profile in the sheath is imposed, (iii) a constant electric field model where the electric field in the sheath is assumed to be equal to a constant fraction of the electric field at the cathode. The sheath size is found to decrease with the pressure, the voltage and the secondary emission coefficient. There is a strong effect of the secondary emission coefficient and the pressure on the voltagecurrent characteristics. The discharge resistance is found to be several hundreds of kΩ and decreases with the discharge current, the pressure and the secondary emission coefficient. A comparison between the matrix sheath model and experiments suggests that both the secondary emission coefficient and the surface area on which the current is collected at the cathode increase with the discharge current. This increase is related to a transition between a discharge confined in the hole at low current and a plasma abruptly expanded on the cathode backside at higher current. (10.1088/0022-3727/46/45/455203)
DOI : 10.1088/0022-3727/46/45/455203
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
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
On the reactivity of plasma-treated photo-catalytic TiO2 surfaces for oxidation of C2H2 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−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
Fine-structure-resolved electron collisions from chlorine atoms in the (3p5)2P3/2o and (3p5)2P1/2o 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 (≈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
Controlled deposition of sulphur-containing semiconductor and dielectric nano-structured films on metals in SF6 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 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
A study of helium atmospheric-pressure guided streamers for potential biological applications
- Gazeli Kristacq
- Noel Cédric
- Clement Franck
- Dauge C.
- Svarnas P.
- Belmonte Thierry
Plasma Sources Science and Technology, IOP Publishing, 2013, 22 (2), pp.025020. The origin of differences in the rotational temperatures of various molecules and ions (N-2(+)(B), OH(A) and N-2(C)) is studied in helium atmospheric-pressure guided streamers. The rotational temperature of N-2(+)(B) is room temperature. It is estimated from the emission band of the first negative system at 391.4 nm, and it is governed by the temperature of N-2(X) in the surrounding air. N-2(X) is ionized by direct electron impact in the outer part of the plasma. N-2(+)(B) is deactivated by collisions with N-2 and O-2. The rotational temperature of OH(A), estimated from the OH band at 306.4 nm, is slightly higher than that of N-2(+)(B). OH(A) is excited by electron impact with H2O during the first 100 ns of the applied voltage pulse. Next, OH(A) is produced by electron impact with OH(X) created by the quenching of OH(A) by N-2 and O-2. H2O diffuses deeper than N-2 into the plasma ring and the rotational temperature of OH(A) is slightly higher than that of N-2(+)(B). The rotational temperature of N-2(C), estimated from the emission of the second positive system at 315.9 nm, is governed by its collisions with helium. The gas temperature of helium at the beginning of the pulse is predicted to be several hundred kelvin higher than room temperature. (10.1088/0963-0252/22/2/025020)
DOI : 10.1088/0963-0252/22/2/025020
Solar wind fluctuations and solar wind activity long-term swing 1963-2012
- Zerbo J.-L.
- Amory-Mazaudier Christine
- Ouattara Frédéric Martial
, 2013, 1301161.
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.
A comparison of bow shock models with Cluster observations during low Alfvén Mach number magnetic clouds
- Turc Lucile
- Fontaine Dominique
- Savoini Philippe
- Hietala H.
- Kilpua E. K. J.
Annales Geophysicae, European Geosciences Union, 2013, 31 (6), pp.1011-019. Magnetic clouds (MCs) are very geoeffective solar wind structures. Their properties in the interplanetary medium have been extensively studied, yet little is known about their characteristics in the Earth's magnetosheath. The Cluster spacecraft offer the opportunity to observe MCs in the magnetosheath, but before MCs reach the magnetosphere, their structure is altered when they interact with the terrestrial bow shock (BS). The physics taking place at the BS strongly depends on ΘBn, the angle between the shock normal and the interplanetary magnetic field. However, in situ observations of the BS during an MC's crossing are seldom available. In order to relate magnetosheath observations to solar wind conditions, we need to rely on a model to determine the shock's position and normal direction. Yet during MCs, the models tend to be less accurate, because the Alfvén Mach number (MA) is often significantly lower than in regular solar wind. On the contrary, the models are generally optimised for high MA conditions. In this study, we compare the predictions of four widely used models available in the literature (Wu et al., 2000; Chapman and Cairns, 2003; Jeřáb et al., 2005; Měrka et al., 2005b) to Cluster's dayside BS crossings observed during five MC events. Our analysis shows that the ΘBn angle is well predicted by all four models. On the other hand, the Jeřáb et al. (2005) model yields the best estimates of the BS position during low MA MCs. The other models locate the BS either too far from or too close to Earth. The results of this paper can be directly used to estimate the BS parameters in all studies of MC interaction with Earth's magnetosphere. (10.5194/angeo-31-1011-2013)
DOI : 10.5194/angeo-31-1011-2013
Atmospheric Pressure Townsend Discharges in nitrogen with small admixtures of oxygen: discussion on the origin of the memory effect
- Naudé Nicolas
- Bouzidi Mohamed Cherif
- Dang V.S.
- Dang van Sung Mussard Marguerite
- Puechagut Loïc
- Belinger Antoine
- Ségur Pierre
- Gherardi Nicolas
, 2013.
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.
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).
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 mm diameter extraction electrode is about 80 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
Normal regime of the weak-current mode of an rf capacitive discharge
- Lisovskiy V. A.
- Yegorenkov V. D.
- Artushenko E.
- Booth Jean-Paul
- Martins S.
- Landry K.
- Douai D.
- Cassagne V.
Plasma Sources Science and Technology, IOP Publishing, 2013, 22 (1), pp.015018. This paper studies the normal and abnormal regimes of a weak-current rf discharge in ammonia, nitrogen, hydrogen and N 2 O for the rf electric field frequencies of 13.56 and 27.12 MHz. We reveal that only the abnormal regime of burning is observed at low pressures when the current growth is accompanied by an rf voltage increase while the surface of the electrodes is completely covered with the discharge. The normal regime occurs at higher gas pressures when the current growth is due to the increase in the surface area occupied by the discharge on the electrodes. The discharge burns in the abnormal mode after the surface of the electrodes is completely covered with the discharge. We demonstrate that the normal current density is directly proportional to the gas pressure and it depends approximately on the square of the rf electric field frequency. We present an analytical model for two limiting cases: constant free path length and constant mobility of positive ions furnishing a satisfactory description of the experimental data. (10.1088/0963-0252/22/1/015018)
DOI : 10.1088/0963-0252/22/1/015018
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 ∼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∗ 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∗ 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
Particle-in-cell simulation of an electronegative plasma under direct current bias studied in a large range of electronegativity
- Oudini N.
- Raimbault Jean-Luc
- Chabert Pascal
- Meige A.
- Aanesland Ane
Physics of Plasmas, American Institute of Physics, 2013, 20, pp.043501. A one-dimensional electronegative plasma situated between two symmetrical parallel electrodes under DC bias is studied by Particle-In-Cell simulation with Monte Carlo Collisions. By varying the electronegativity α ≡ n−/ne from the limit of electron-ion plasmas (negative ion free) to ion-ion plasmas (electron free), the sheaths formation, the negative ion flux flowing towards the electrodes, and the particle velocities at the sheath edges are investigated. Depending on α, it is shown that the electronegative plasma behavior can be described by four regimes. In the lowest regime of α, i.e., α < 50, negative ions are confined by two positive sheaths within the plasma, while in the higher regimes of α, a negative sheath is formed and the negative ion flux can be extracted from the bulk plasma. In the two intermediate regimes of α, i.e., 50 < α < 10⁵, both the electron and the negative ion fluxes are involved in the neutralization of the positive ions flux that leaves the plasma. In particular, we show that the velocity of the negative ions entering the negative sheath is affected by the presence of the electrons, and is not given by the modified Bohm velocity generally accepted for electronegative plasmas. For extremely high electronegativity, i.e., α > 10⁵, the presence of electrons in the plasma is marginal and the electronegative plasma can be considered as an ion-ion plasma (electron free). (10.1063/1.4798501)
DOI : 10.1063/1.4798501
Secondary electron induced asymmetry in capacitively coupled plasmas
- Lafleur Trevor
- Chabert Pascal
- Booth Jean-Paul
Journal of Physics D: Applied Physics, IOP Publishing, 2013, 46, pp.135201. Using a simple analytical model, together with a 1D particle-in-cell simulation, we show that it is possible to generate an asymmetric plasma response in a sinusoidally excited, geometrically symmetric, capacitively coupled plasma (CCP). The asymmetric response is produced using rf electrodes of differing materials, and hence different secondary electron emission coefficients. This asymmetry in the emission coefficients can produce a significant, measurable dc bias voltage (Vbias /Vrf ∼ 00.2), together with an asymmetry in the plasma density profiles and ion flux to each electrode. The dc bias formation can be understood from a particle-flux balance applied to each electrode, and results from two main effects: (1) the larger effective ion flux at each electrode due to the emission of secondary electrons and (2) ion-flux multiplication within the sheath due to ionization from these emitted secondary electrons. By making use of an empirical fit to the simulation data, the possibility of non-invasively estimating secondary electron emission coefficients in CCP systems is discussed. (10.1088/0022-3727/46/13/135201)
DOI : 10.1088/0022-3727/46/13/135201
Absolute atomic oxygen and nitrogen densities in radio-frequency driven atmospheric pressure cold plasmas: Synchrotron vacuum ultra-violet high-resolution Fourier-transform absorption measurements
- Niemi K.
- O'Connell D.
- de Oliveira N.
- Joyeux D.
- Nahon L.
- Booth Jean-Paul
- Gans T.
Applied Physics Letters, American Institute of Physics, 2013, 103 (3), pp.034102. Reactive atomic species play a key role in emerging cold atmospheric pressure plasma applications, in particular, in plasma medicine. Absolute densities of atomic oxygen and atomic nitrogen were measured in a radio-frequency driven non-equilibrium plasma operated at atmospheric pressure using vacuum ultra-violet (VUV) absorption spectroscopy. The experiment was conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Measurements were carried out in plasmas operated in helium with air-like N2/O2 (4:1) admixtures. A maximum in the O-atom concentration of (9.1 ± 0.7)×1020 m−3 was found at admixtures of 0.35 vol. %, while the N-atom concentration exhibits a maximum of (5.7 ± 0.4)×1019 m−3 at 0.1 vol. %. (10.1063/1.4813817)
DOI : 10.1063/1.4813817
Structure of nonlocality of plasma turbulence
- Gürcan Özgür D.
- Vermare Laure
- Hennequin Pascale
- Berionni Vincent
- Diamond P.H.
- Dif-Pradalier Guilhem
- Garbet X.
- Ghendrih Philippe
- Grandgirard Virginie
- Mcdevitt C.J.
- Morel Pierre
- Sarazin Y.
- Storelli A.
- Bourdelle C.
- Tore Supra Team
Nuclear Fusion, IOP Publishing, 2013, 53, pp.073029. Various indications on the weakly nonlocal character of turbulent plasma transport both from experimental fluctuation measurements from Tore Supra and observations from the full-f, flux-driven gyrokinetic code GYSELA are reported. A simple Fisher equation model of this weakly nonlocal dynamics can be formulated in terms of an evolution equation for the turbulent entropy density, which contains the basic phenomenon of radial turbulence spreading in addition to avalanche-like dynamics via coupling to profile modulations. A derivation of this model, which contains the so-called beach effect, a diffusive and convective flux components for the flux of turbulence intensity, in addition to linear group propagation is given, starting from the drift-kinetic equation. The proposed model has the form of a transport equation for turbulence intensity, and may be considered as an addition to transport modelling. The kinetic fluxes given, can be computed using model closures, or local gyrokinetics. The model is also used in a particular setup that represents the near edge region as a relatively stable zone between the core and edge region where the energy injection is locally more substantial. It is observed that with constant, physical coefficients, the model gives a convincing qualitative profile of fluctuation intensity when the turbulence is coming from the core region with either a group velocity or a convective flux. (10.1088/0029-5515/53/7/073029)
DOI : 10.1088/0029-5515/53/7/073029
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
Redistribution of high energy alpha particles due to sawteeth with partial reconnection
- Farengo R.
- Ferrari H.E.
- García-Martínez P.L.
- Firpo Marie-Christine
- Ettoumi Wahb
- Lifschitz A.F.
Nuclear Fusion, IOP Publishing, 2013, 53, pp.043012. The redistribution of high energy alpha particles due to internal kink modes is studied in plasmas with ITER-like parameters. The exact particle trajectories in the total fields, equilibrium plus perturbation, are calculated. The equilibrium magnetic field is obtained by analytically solving the GradShafranov equation and the perturbed electric and magnetic fields are reconstructed using ideal MHD and the experimental information about the displacement eigenfunction. The (1, 1), (2, 2) and (2, 1) modes are included and the effect of changing their amplitude and frequency is determined. The results show that if the conditions are similar to those reported in Igochine et al (2007 Nucl. Fusion 47 23), the peak density of counter-passing particles decreases between 25% and 40% (depending on the energy); the peak of the trapped particles density shifts outwards by approximately 10% of the minor radius and the total on axis density decreases by more than 25%. This redistribution occurs inside the q = 1 surface. The addition of a (2, 1) mode, which can produce the stochastization of the magnetic field, significantly increases particle redistribution and allows particles to spread beyond the q = 1 surface. Different groups of particles (co-passing, counter-passing, trapped) respond differently to the perturbations. (10.1088/0029-5515/53/4/043012)
DOI : 10.1088/0029-5515/53/4/043012

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