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Publications: Articles

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References par page: Mots clefs Voir les resumes


Yang, Z., Krieger, K., Lunt, T., Brochard, F., Briançon, J-L., Neu, R., Dux, R., Janzer, A., Potzel, S., Pütterich, T. and Asdex Upgrade Team, The
Journal of Nuclear Materials, 438:S846-S851

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

Gazeli, K., Noel, C., Clement, F., Daugé, C., Svarnas, P. and Belmonte, T.
Plasma Sources Science and Technology, 22:025020

Resume: 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.

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

Hicks, J., Tejeda, A., Taleb-Ibrahimi, A., Nevius, M. S., Wang, F., Shepperd, K., Palmer, J., Bertran, F., Le Fèvre, P., Kunc, J., de Heer, W. A., Berger, C. and Conrad, E. H.
NATURE PHYSICS, 9(1):49-54
ISSN: 1745-2473

Equipe: Département P2M : Surfaces et Spectroscopies

Dap, S., Hugon, R., Lacroix, D., de Poucques, L., Briançon, J.-L. and Bougdira., J.
Physics of Plasmas, 20:033703

Resume: In this paper, an experimental investigation of dust particle agglomeration in a capacitively coupled RF discharge is reported. Carbonaceous particles are produced in an argon plasma using acetylene. As soon as the particle density becomes sufficient, dust density waves (DDWs) are spontaneously excited within the cathode sheath. Recently, it was proven that DDWs can significantly enhance the agglomeration rate between particles by transferring them a significant kinetic energy. Thus, it helps them to overcome Coulomb repulsion. The influence of this mechanism is studied from acetylene injection to the formation of very large agglomerates forming an organized structure after a few dozens of seconds. For this purpose, three diagnostic tools are used: extinction measurements to probe nanometer-sized particles, fast imaging for large agglomerates and a dust extraction technique developed for ex-situ analysis. (C) 2013 American Institute of Physics.

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

Jardy, Alain, Chapelle, Pierre, Malik, Ashish, Bellot, Jean-Pierre, Combeau, Herve and Dussoubs, Bernard
ISSN: 0915-1559

Resume: The present study aims to understand the melting of the consumable electrode in the VAR process and gain some insight into the influence of an ensemble arc motion on the melting behaviour. In a previous study, a 2D axisymmetric model of the heat transfer in the cathode had been developed. Using the operating parameters as model inputs, it enabled prediction of the melt rate and the evolution of the melting area. Model results were successfully compared to melt rate measurements in an industrial VAR furnace. In recent years, it has been claimed that the electric arc may not be considered as steady and axisymmetric. Our experimental investigation of the luminosity recorded during an actual VAR heat confirms that a transient 3D behaviour may take place. Therefore, a 3D version of the previous model was set up to predict the heat transfer and melting of the electrode, using the unknown ensemble arc motion as an input. The arc is assimilated to a transient distribution of energy flux density. Results evidence that the influence of the arc motion on the shape of the electrode tip can be very important. In industrial practice, the cathode tip usually remains relatively flat during melting. The shapes of the computed electrode tips enable us to propose some arc parameters which remain compatible with both the periodic behaviour of the light emitted and the flatness of the electrode.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

Bieber, T., Glad, X., De Poucques, L, Hugon, R., Vasseur, J.-L. and Bougdira., J.
The Open Plasma Physics Journal, 6:32-43

Resume: This paper deals with pure argon plasma studied in a magnetically enhanced inductively coupled reactor. Laser induced fluorescence technique was performed with an optical parametric oscillator laser on the 3d4F7/2 and 3d2G9/2 Ar+ metastable levels and on the (2P03/2)4s2 neutral metastable state to determine their relative densities. Langmuir probe was used as a complementary diagnostic to measure the electron energy distribution functions. When increasing the confinement magnetic field, the metastable state density collapses for all cited levels, by contrast with ne which is continuously growing. Calculations were carried out for neutral argon to explain this behaviour. The results show that the metastable population is depleted by electron-impact excitation and ionization, these loss processes becoming dominant compared to the metastable state creation term.

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

Cortes, R., Tejeda, A., Lobo-Checa, J., Didiot, C., Kierren, B., Malterre, D., Merino, J., Flores, F., Michel, E. G. and Mascaraque, A.
ISSN: 1098-0121

Equipe: Département P2M : Surfaces et Spectroscopies

Devolder, T., Tahmasebi, T., Eimer, S., Hauet, T. and Andrieu, S.
Applied Physics Letters, 103(24)

Equipe: Département P2M : Nanomagnétisme et Electronique de Spin

Zhang, H.Y., Cleymand, F., Noel, C., Kahn, C.J.F., Linder, M., Dahoun, A., Henrion, G. and Arab-Tehrany, E.
Carbohydrate Polymers, 93(2):401-411

Resume: This work addresses the functionalization of chitosan thin films and its nanoliposomes blend films by a microwave-excited Ar/N2/H2 surface-wave plasma treatment which was found an effective tool to modify surface properties. Changes in the film properties (wettability, chemical composition, morphology) induced by the plasma treatment are studied using water contact angle measurements, X-ray photoelectron spectroscopy and scanning probe microscopy. The results suggest that hydrophilicity of the films is improved by plasma treatment in a plasma condition dependency manner. Water contact angle of chitosan films before and after plasma treatment are, respectively, 101° and 27°. Besides chemical changes on the surface, the nanoliposomes incorporation and plasma treatment also induce morphological modifications. Moreover, a correlation is found between the nanoliposomes composition and size, and the effects of plasma treatment. It is shown that the plasma treatment significantly improves the chitosan film functionalization. The effect of N2 content (88% and 100%) in the plasma gas mixture on the film etching is also pointed out.

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

Martin, J., Melhem, A., Shchedrina, I., Duchanoy, T., Nominé, A., Henrion, G., Czerwiec, T. and Belmonte, T.
Surface and Coatings Technology, 221:70

Resume: The plasma electrolytic oxidation (PEO) of aluminium alloys is investigated for different electrical working conditions using a pulsed bipolar current supply. A particular attention is paid to the effect of the anodic current density (from 10 to 90 A dm-2) and current pulse frequency (from 100 to 900 Hz) on the resulting oxide layer. Micro-discharges are characterized during the process by means of fast video imaging with a time and a space resolution of 8 μs and 0.017 mm2, respectively. Correlations are established between themicro-discharge characteristics (surface density, lifetime and size) and the elaborated oxide layers (morphology, growth rate and surface roughness). The highest coating growth rate measured (2.1 μm min-1) is achieved with the combination of the highest current density (75.7 A dm-2) and the highest current pulse frequency (900 Hz). Within these specific current conditions it is concluded that the detrimental effects of numerous micro-discharges are minimized. The results also show that the surface roughness may be largely affected by the presence of long-lived and large micro-discharges which develop over the processed surface. The strongest micro-discharges (live duration up to 0.3 ms and cross-sectional area up to 1 mm2) are mainly observed with the combination of the highest current density (75.7 A dm-2) and the lowest current pulse frequency (100 Hz).

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

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