Simulation of the discharge propagation in a capillary tube in air at atmospheric pressure

International audienceThis paper presents simulations of an air plasma discharge at atmospheric pressure initiated by a needle anode set inside a dielectric capillary tube. We have studied the influence of the tube inner radius and its relative permittivity ε r on the discharge structure and dynamics. As a reference, we have used a relative permittivity ε r = 1 to study only the influence of the cylindrical constraint of the tube on the discharge. For a tube radius of 100 µm and ε r = 1, we have shown that the discharge fills the tube during its propagation and is rather homogeneous behind the discharge front. When the radius of the tube is in the range 300 to 600 µm, the discharge structure is tubular with peak values of electric field and electron density close to the dielectric surface. When the radius of the tube is larger than 700 µm, the tube has no influence on the discharge which propagates axially. For a tube radius of 100 µm, when ε r increases from 1 to 10, the discharge structure becomes tubular. We have noted that the velocity of propagation of the discharge in the tube increases when the front is more homogeneous and then, the discharge velocity increases with the decrease of the tube radius and ε r. Then, we have compared the relative influence of the value of tube radius and ε r on the discharge characteristics. Our simulations indicate that the geometrical constraint of the cylindrical tube has more influence than the value of ε r on the discharge structure and dynamics. Finally, we have studied the influence of photoemission processes on the discharge structure by varying the photoemission coefficient. As expected, we have shown that photoemission, as it increases the number of secondary electrons close to the dielectric surface, promotes the tubular structure of the discharge

La pollution oxydante sur la facade mediterraneenne. Ses effets sur les vegetaux, leur utilisation possible pour la detection des zones soumises a cette pollution

* INRA, Centre de Recherches d'Avignon, Unite Regionale de Documentation, Montfavet Diffusion du document : INRA, Centre de Recherches d'Avignon, Unite Regionale de Documentation, MontfavetNational audienc

Etude d'un conjoncteur-disjoncteur à vide pour impulsion de courant intense

L'article est relatif à l'étude des capacités de conduction et de réisolement d'un conjoncteur-disjoncteur à vide. Le temps de conduction est de 27 μs et le temps de réisolement imposé est inférieur à 100 μs. Nous avons mis en évidence l'influence des paramètres physiques et géométriques afin d'obtenir le régime d'arc diffus donnant accès aux meilleures performances de disjonction. Ainsi le pouvoir de coupure du prototype testé, a dépassé 109 V.A (36 kA, 44 kV)

Etude d'un conjoncteur-disjoncteur à vide pour impulsion de courant intense

The article is relative to the recovery phenomena and conduction capacities of a fast triggered vacuum switch. 27 μs current pulses are used. Fixed recovery times are less than 100 μs. We study the influence of physical and geometrical parameters in order to obtain the arc diffuse mode which allows best switching performances. Thus a breaking capacity more than 109 V. A is obtained with a 36 kA current pulse and 44 kV recovery voltage.L'article est relatif à l'étude des capacités de conduction et de réisolement d'un conjoncteur-disjoncteur à vide. Le temps de conduction est de 27 μs et le temps de réisolement imposé est inférieur à 100 μs. Nous avons mis en évidence l'influence des paramètres physiques et géométriques afin d'obtenir le régime d'arc diffus donnant accès aux meilleures performances de disjonction. Ainsi le pouvoir de coupure du prototype testé, a dépassé 109 V.A (36 kA, 44 kV)

Atmospheric pressure generation of O(a) by microplasmas

International audienceThe generation of singlet delta oxygen states (O(a)) by microplasmas has been studied experimentally. In the present paper, it is shown that micro-cathode sustained discharges (MCSD's) can be used to produce high fluxes of O(a) at atmospheric pressure. In He/O/NO mixtures, O(a) number densities higher than 10 cm can be generated by this 3-electrode configuration and transported over distances of some tens of cm. In fact, at total flow rates up to 30 ln/min, O(a) fluxes above 10 mmol/h were measured in the MCSD afterglow, at 26 cm downstream. As a result, MCSD's appear to be very efficient and suitable tools for the continuous production of large amounts of O(a) at atmospheric pressure, which could give rise to a wide range of new applications, namely biological. The effect of different parameters such as gas flows and mixtures, and discharge current are discussed in the paper

Mapping the nature of mantle domains in Western and Central Europe based on clinopyroxene and spinel chemistry: Evidence for mantle modification during an extensional cycle

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Study of the treatment's homogeneity in plasma assisted chemical vapour deposition by atmospheric pressure dielectric barrier discharge

Proceedings of the 35th International Conference on Metallurgical Coatings and Thin Films - 35th International Conference on Metallurgical Coatings and Thin FilmsInternational audienceDielectric Barrier Discharge (DBD) appears to be a promising technology to perform surface treatments at atmospheric pressure, particularly for the treatments of large-dimension flat objects for on-line industrial applications. Besides the fact of allowing short treatment times, the advantage of atmospheric pressure is the suppression of constraints correlated to the implementation of vacuum devices necessary for low pressure treatments. But at the present time, if this technology showed its ability for the surface cleaning, it is not still the case for thin film deposition over large surfaces, due to an insufficient homogeneity of the deposited layers. This lack of homogeneity is the main present problem limiting the use of DBD in PACVD. The study of the layer's uniformity leads us to search links between the internal physical phenomena inside the reactor and the layer's properties. This paper is focused to the study of the spatial homogeneity of SiOx thin films deposited over large surfaces by using an atmospheric pressure DBD with N2/O2/HMDSO gas mixture. The results presented in this paper show that it is possible to understand the homogeneity variations of deposited layers by simultaneously making the link between the deposited power in plasma (taking into account both the energy per pulse and the pulse repetition frequency) and the gas hydrodynamics in the flow boundary laye