Plasmas radiofréquence pour l'analyse des matériaux (étude expérimentale, analytique et numérique)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

An atmospheric plasma source for seed treatment and biological decontamination

Pohoata Valentin, Topala Ionut, Agheorghiesei Catalin, CPPA 2019 - XVIIIth International Conference on Plasma Physics and Application 20th - Book of Abstracts : International audienceAtmospheric plasma treatment can affect growth and physiology of plants. Some recent works on seeds shown modifications of the surface properties and stimulation of seed germination. A plasma exposure can also have biocidal or fungicidal effects on seeds.In this preliminary work, an atmospheric multiple points plasma source has been developed. The source is composed by thousands of points arranged in concentric circles. The diameter is approximately 90 mm. The power supply is a DC one generating 35 kV and 1 mA (max values). The voltage is applied to the multiple points. The ground is connected to the substrate (conductive grid). The plasma is generated in ambient air between the multiple points and the conductive grid. The experimental set-up is presented on Figure 1. For plasma treatment, the samples could be placed on the grid (direct treatment) or under the grid (indirect treatment using the ionic wind generated by the discharge. First, the current characterization as a function of voltage was performed to characterize the plasma source. Next spatial optical emission distribution measurements were performed with an optical spectrometer (HR2000+, Ocean Optics) from the emission spectra for the main observed species. In a preliminary work, this source was used to evaluate the plasma effect on different seed properties and seed germination. The seeds were directly in contact with the plasma or exposed to the ionic wind generated by the multiple discharges

Plasmas radiofréquence pour l'analyse des matériaux (étude expérimentale, analytique et numérique)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Parametric Studies of a Mercury-Free DBD Lamp

Mercury discharge lamps are often used because of their high efficiency; however, the usage of mercury lamps will be restricted or forbidden for safety and environmental purposes. Finding alternative solutions to suppress mercury is of major interest. The aim of this work is to increase the luminous efficacy of a commercial-free mercury flat dielectric barrier discharge lamp (Planilum, St Gobain) in order to reach the necessary conditions for the lamp to be used as a daily lighting source. The lamp is made of two glass plates separated by a gap of 2 mm. The gap is filled by a neon xenon mixture. The external electrodes made of transparent ITO (indium tin oxide) are deposited on the lamp glass plates. The electrical signal applied to the electrodes generates a UV-emitting plasma inside the gap. Phosphors deposited on the glass allow the production of visible light. The original electrode geometry is plane-to-plane; this induces filamentary discharges. We show that changing the plane-to-plane geometry to a coplanar geometry allows the plasma to spread all over the electrode surface, and we can reach twice the efficacy of the lamp (32 lm/W) as compared to the original value. Using this new electrode geometrical configuration and changing the electrical signal from sinusoidal to a pulsed signal greatly improves the visual uniformity of the emitted light all over the lamp. Electrical and optical parametric measurements were performed to study the lamp characteristics. We show that it is possible to develop a free mercury lamp with an efficacy compatible with lighting purposes

Pulsed glow discharges for analytical applications

Non equilibrium plasmas such as glow discharges have become a commonly used tool in direct surface and interface analysis of solid materials. The application of pulsed glow discharges to material analysis has been studied by several research groups over the last 20 years. Two European projects, EMDPA and GLADNET currently work on the analytical applications of glow discharges, giving a particular attention to pulsed discharges. This review demonstrates the advantages of pulsed discharge operation by showing how the specific excitation and ionisation processes observed during the plasma ignition phase and the afterglow can be used for analytical applications. In the first part of the review the dominant physical processes occurring during the plasma ignition and the afterglow of a pulsed plasma are reviewed. For both phases, the evolution of the population of electrons and sputtered atoms is discussed and related to the excitation and ionisation processes. In view of the complexity of the processes occurring and the variety of experimental conditions presented in the published papers, we have made some effort to point-out and compare the relevant features of the various experimental set-ups used. In the second part of this review, analytical applications of pulsed discharges for both mass spectrometry and optical emission techniques are presented and discussed. In particular the importance of time resolved signal acquisition is pointed out. The question of why pulsed discharges have not yet been introduced in routine analysis despite their obvious advantages over the continuous mode is discussed. Finally the first exciting results of the application of a pulsed glow discharge to surface and interface analysis of polymer multi-layers are shown

Evaluation of a corona plasma source efficacy as Alfaalfa (medicago sativa) seed bacteriological decontamination process

International audienc

An atmospheric plasma source for seed treatment and biological decontamination

International audienc

A low pressure air plasma improving bell pepper seed germination and vigor

International audienc

Lampe plane à décharge

The present invention relates to a flat discharge lamp (1000) transmitting in the visible and/or in the UV, comprising first and second dielectric walls (2, 3) facing each other, kept parallel and sealed around the periphery (8), thus defining an internal space (10) filled with a plasma gas, and comprising a UV and/or visible light source (6), first and second electrodes (4, 5) in separate planes parallel to the first and second walls, the first electrode (4) being at a potential VO higher than the potential V1 of the second electrode, and the first electrode being placed in the internal space and closer to the first dielectric wall than the second electrode. Furthermore, the first electrode is spaced away from the first dielectric wall by the gas, the first and second electrodes being separated by a flat electrical insulator (7) with at least one main face (71, 72), called a holed face, provided with emergent holes (73), at least one of the first and second electrodes being in contact with the holed main face and having discontinuities at least in the extension of said holes.La présente invention porte sur une lampe plane à décharge (1000) transmettant dans le visible et/ou l'UV comportant transmettant dans le visible et/ou l'UV comportant des première et deuxième parois diélectriques (2, 3) en regard, maintenues parallèles et scellées en périphérie (8), délimitant ainsi un espace interne (10) rempli de gaz plasmagène et comprenant une source de lumière UV et/ou visible (6), des première et deuxième électrodes (4, 5) dans des plans distincts parallèles aux première et deuxième parois, la première électrode (4) étant à un potentiel VO plus élevé que le potentiel Vl de la deuxième électrode, et la première électrode étant agencée dans l'espace interne et plus proche de la première paroi diélectrique que la deuxième électrode. Et la première électrode est espacée de la première paroi diélectrique, par le gaz, les première et deuxième électrodes sont séparées par un isolant électrique plan (7) avec au moins une face principale (71, 72), dite trouée, dotée des trous débouchants (73), l'une au moins des première et deuxième électrodes est en contact avec la face principale trouée et présente des discontinuités au moins dans le prolongement desdits trous