In this work, we present an experimental and theoretical study of a low frequency, atmospheric plasma-jet discharge in air. Voltage-current characteristics and spectroscopic data were experimentally obtained, and a theoretical model developed to gain information of different aspects of the discharge. The discharge is modeled as a cathode layer with different mechanisms of electron emission and a main discharge channel that includes the most important kinetic reactions and species. From the electric measurements, it is determined that high electric field magnitudes are attained in the main channel, depending on the gas flow rate. Using the voltage-current characteristics as an input, the model allows to determine the plasma state in the discharge, including electron, gas, and molecular nitrogen vibrational temperatures. The model also allows to infer the mechanisms of secondary electron emission that sustain the discharge.
The current and potential applications of atmospheric pressure plasmas in medicine generate an increasing need to develop safe and reliable plasma devices for patient treatment. This paper shows how the estimation of safety risks, the stability of the generated plasma, and the effectiveness in the aimed application can orientate the design process of a specific atmospheric pressure plasma device intended for clinical use. A promising plasma jet device operated with air is optimized, leading to a configuration with a more advanced design that reduces the temperature of the effluent, prevents the material degradation and improves the isolation of the high voltage components. The effects of the plasma jet treatment are investigated by chemical analysis of demineralized water and inactivation tests on E. coli cultures.
Low-temperature, high-pressure plasma jets have an extensive use in medical and biological applications. Much work has been devoted to study these applications while comparatively fewer studies appear to be directed to the discharge itself. In this work, in order to better understand the kind of electrical discharge and the plasma states existing in those devices, a study of the electrical characteristics of a typical plasma jet, operated at atmospheric pressure, using either air or argon, is reported. It is found that the experimentally determined electrical characteristics are consistent with the model of a thermal arc discharge, with a highly collisional cathode sheet. The only exception is the case of argon at the smallest electrode separation studied, around 1 mm in which case the discharge is better modeled as either a non-thermal arc or a high-pressure glow. Also, variations of the electrical behavior at different gas flow rates are interpreted, consistently with the arc model, in terms of the development of fluid turbulence in the external jet. V C 2013 AIP Publishing LLC.
are well known for bacterial decontamination.-Pseudomonas aeruginosa-10 log 10 respectively, although viability assays showed that some cells were alive. Moistened-air plas-Pseudomonas bioassessed.
In this work, we present an experimental and theoretical study of a low frequency, atmospheric plasma-jet discharge in argon. The discharge has the characteristics of a contracted glow with a current channel of submillimeter diameter and a relatively high voltage cathode layer. In order to interpret the measurements, we consider the separate modeling of each region of the discharge: main channel and cathode layer, which must then be properly matched together. The main current channel was modeled, extending a previous work, as similar to an arc in which joule heating is balanced by lateral heat conduction, without thermal equilibrium between electrons and heavy species. The cathode layer model, on the other hand, includes the emission of secondary electrons by ion impact and by additional mechanisms, of which we considered emission due to collision of atoms excited at metastable levels, and field-enhanced thermionic emission (Schottky effect). The comparison of model and experiment indicates that the discharge can be effectively sustained in its contracted form by the secondary electrons emitted by collision of excited argon atoms, whereas thermionic emission is by far insufficient to provide the necessary electrons. V
R e c i b i d o : 2 7 / 0 2 / 2 0 1 5 ; a c e p t a d o : 2 2 / 0 7 / 2 0 1 5 Los plasmas no térmicos generados a presión atmosférica presentan interés en aplicaciones biomédicas vinculadas a la esterilización y descontaminación microbiana. Este tipo de plasmas produce especies activas como O, N2 * y radicales OH, asociadas a procesos de inactivación de microorganismos y a la remoción de materiales orgánicos.En este trabajo se estudia una descarga eléctrica tipo plasma jet capaz de generar una pluma de plasma con temperaturas próximas a la temperatura ambiente. La descarga se produce entre dos discos conductores separados por un disco aislante, con un orificio central de 1 mm a través del cual fluye el gas de operación. Se realizaron mediciones de las curvas características de tensión-corriente empleando aire y argón y variando el espesor del aislante entre 1 y 10 mm. Además, se midió el espectro de emisión de la descarga. Palabras clave: descargas eléctricas, jet de plasma, aplicaciones médicas de plasma.Non-thermal plasmas generated at atmospheric pressure are of great interest for biomedical applications related to sterilization and microbial decontamination. These plasmas produce reactive species such as O, N2 * and OH radical and atomic O, associated with processes of inactivation of microorganisms and removal of organic materials.In this work we study an electrical discharge capable of generating a plasma plume close to ambient temperature. The discharge is produced between two conducting disks separated by an insulating disk, with a 1 mm central hole through which the operating gas flows. Characteristic voltage-current curves were measured using either air or argon and variable insulator thicknesses between 1 and 10 mm. Also, the discharge emission spectrum was measured.
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