Bruno Caillier

Characterization of an asymmetric DBD plasma jet source at atmospheric pressure

Non-thermal atmospheric pressure plasma jets or plasma plumes have recently been largely investigated in applications like materials processing, biomedical treatment and analytical chemistry. In this paper He-discharges in an asymmetrical Dielectric Barrier Discharge (DBD) have been experimentally studied with an Intensified Charge Coupled Device (ICCD) camera, Optical Emission Spectroscopy (OES) and Time-Of-Flight Mass Spectrometry (TOF-MS) measurements. The development of the plasma plume, its apparent length and the spatial distribution of the excited and ionized species along the plasma plume have been characterized as a function of the applied voltage and the gas flow rate. A TOF-MS spectrometer has been used to characterize ionized species (positive and negative ions) produced by the plasma alone and the plasma with addition of ethanol, both as a function of the distance between the plasma plume and the vacuum interface of the spectrometer.

Improve the luminous efficacy of dielectric barrier discharge xenon lamp

Xenon excimer dielectric barrier discharge is a good candidate for free mercury lightning. The studied device1 is consisting of two glass plates separated by a constant gas gap. The glass thickness is 4 mm and the gap 2 mm. A transparent conducting material (electrode) has been deposited on both external sides (plane to plane electrodes) and white phosphors2 on both internal sides of the dielectric. The lamp is filled with Neon-xenon gas mixture and operates in a pressure range of 100-400 torr. In a previous work1, for sinusoidal and pulsed excitations, we have shown the influence of the applied voltage (amplitude and frequency) on the consuming power, the light emission and mostly on the homogeneity of the discharge (modeling and experimental works).

Decontamination Efficiency of a DBD Lamp Containing an UV-C Emitting Phosphor.

Among different physical and chemical agents, the UV radiation appears to be an important route for inactivation of resistant microorganisms. The present study introduces a new mercury‐free Dielectric Barrier Discharge (DBD) flat lamp, where the biocide action comes from the UV emission produced by rare‐earth phosphor obtained by spray pyrolysis, following plasma excitation. In this study, the emission intensity of the prototype lamp is tuned by controlling gas pressure and electrical power, 500 mbar and 15 W, corresponding to optimal conditions. In order to characterize the prototype lamp, the energetic output, temperature increase following lamp ignition and ozone production of the source were measured. The bactericidal experiments carried out showed excellent results for several gram‐positive and gram‐negative bacterial strains, thus demonstrating the high decontamination efficiency of the DBD flat lamp. Finally, the study of the external morphology of the microorganisms after the exposure to the UV emission suggested that other mechanisms than the bacterial DNA damage could be involved in the inactivation process.

Decontamination of metallic surfaces inocculated with bacillus atrophaeus spores using an UV-C neon-xenon dielectric barrier discharge lamp

The endospores produced by Bacillus spp. are known to be highly resistant to most disinfection methods. Due to their extreme resilience, spores of several Bacillus strains are widely used as biological indicators for sterility testing. In this work, the sporicidal efficacy of a lamp prototype on B. atrophaeus spores is investigated.

Spatial emission behaviour of dielectric barrier discharge lamp driven by sinusoidal or pulsed voltage excitation

Xenon excimer dielectric barrier discharge is a good candidate for free mercury lamp. The studied device is consisting of two glass plates separated by a constant gas gap. The glass thickness is 4 mm and the gap 2 mm. A transparent conducting material (electrode) has been deposited on both external sides and phosphors (white emitting powders) on both internal sides of the dielectric. The lamp is filled with rare gas mixture and operates in a pressure range of 100-400 torr. A sinusoidal or a pulsed excitation voltage can be used up to 3000 V in a frequency range of 10-50 kHz. In a previous work for sinusoidal excitation, we shown the influence of the applied voltage (amplitude and frequency) on the consuming power, the light emission and mostly on the non-homogeneity of the discharge. Using a 2 dimensional model developed in our laboratory, the effects of the applied voltage (amplitude and frequency) and the pressure will be studied. Particularly on the distance between the streamers when the discharge is not homogeneous. In this work, for pulsed excitation, we will present some results concerning a Ne-Xe 50% mixture for three different pressures and we will discuss the influence of the applied voltage (waveforms, amplitude and frequency) on the consuming power, the light emission (ICCD and luminance) and mostly on the spatial emission of the discharge. We will also compare experimental results between sinusoidal and pulsed excitations.

Target interacting with an atmosheric pressure helium DBD

Summary form only given. In last decades, atmospheric pressure plasma jets (APPJs) have been extensively studied due to their potential in applications for biomedical treatment or analytical chemistry. However, the use of plasma jets for technical applications requires extensive understanding of the processes that take place in realistic conditions of the use1.Numerous parameters such as the geometry of the device, the power supply or the working gas have been identified as having an influence on the plasma characteristics. Recently it has been reported that one of the main factors that affect the behavior of the plasma discharge is the surface placed in front of the jet2. The aim of this study is to investigate on the effect of the target conductivity on the discharge characteristics. The plasma source used in this work has an asymmetric design and is composed of two cylindrical dielectric parts - a cylindrical dielectric chamber ending by a dielectric tube with a smaller diameter. An external conductive electrode surrounds the two parts. The source is operated with helium at a flow of 2.1 l/min and powered by 20 kHz sinus or square voltage of 2 kV. The plasma propagation for this plasma source was described and analyzed without target - i.e. free plasma jet3. In this work, the influence of several targets (copper, alumina, water and polymer) on the spatial distribution of several excited or ionized species from the APPJ (N2, N2+, He, O) was studied. Resolved spatial optical emission distribution measurements were performed with an ocean optics spectrometer HR2000+. Time resolved plasma jet propagation was studied with an ICCD camera. Parametric studies for sinus and square waveforms and several distances between the target and source will be presented.

Reactive species generation and biocidal efficiency of an asymmetric DBD APPJ

Summary form only given. Atmospheric Pressure Plasma Jets (APPJ) are now well established in the community as a versatile source of reactive species at relatively low temperature. The applications range from nanomaterial synthesis and analytical chemistry to soft decontamination of sensible surfaces. For each application, the reactive species created must be identified and quantified, in the gas phase, as well as in the liquid phase. The aim of this study was to investigate the correlation between the plasma-induced inactivation of bacteria in the liquids and production of reactive species inside the bacterial suspensions.The asymmetric DBD APPJ used in this study has been described with great detail in previous work1. It consists of a 38 mm diameter cylindrical grounded electrode (15 mm length) and a 7 mm to 3 mm conical live electrode (36 mm length). The distance between the two electrodes is fixed to 10 mm. The live electrode is powered with a square wave AC voltage at 20 kHz and 2.5 kV. The gas injected in the plasma jet is Helium, with 0 to 0.5% O2, at 2.1 L min-1. E. coli (ATCC 25992) was grown overnight in tryptic soy broth and then washed and resuspended in phosphate buffer or saline. After plasma exposure the bacterial suspension was recovered and the number of surviving bacteria was estimated by CFU counting after incubation of tryptic soy agar for one day. Treated bacterial suspension was also used to assess two other viability parameters - the cell respiration (XTT assay) and cell permeability using fluorescent dyes (LIVE/DEAD BacLight Viability Kit). The gas phase reactive species (e.g. N2, OH, O) were assed using spatially resolved optical emission spectroscopy (Ocean Optics) and filtered ICCD camera imaging (Princeton Instruments). Colorimetric assays were used to determine the concentrations of ozone, hydrogen peroxide and nitrite in the liquid phase. The understanding of the relation between the reactive species production and the biocidal capacities of the DBD plasma jet allows a better insight into the cell response to plasma exposure.

Spatial and temporal evolution of a DBD plasma lamp

In this work, the spatial development of dielectric barrier discharges was investigated to quantify the influence of key parameters, such as applied voltage, frequency, duty cycle and electrode shapes on the plasma behavior.

Characteristics of Krypton dielectric barrier discharge lamp

In this work, the effect of the power supply (frequency, waveform and power), size of the electrodes and filling gas pressure on the optical emission and electrical characteristics from Dielectric Barrier Discharge (DBD) flat lamp was investigated.

Studies on biocidal activity of an UV-C DBD lamp

In this work, the effect of decontamination of an UV-C DBD lamp on different vegetative bacteria strain was investigated.