Experimental Studies Of Negative Glow Dc Gas Discharges

Author : Jayr de Amorim Filho
Publisher :
ISBN 13 : 9788178952871
Total Pages : 190 pages
Book Rating : 4.9/5 (528 download)

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Download or read book Gas Discharges written by Jayr de Amorim Filho and published by . This book was released on 2007-01-01 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a collection of review articles in the field of gas discharges and their applications. The contributors are known scientists in the field of low-temperature plasmas working in modeling, diagnostics and applications. Computer modeling and simulation has become an important research tool for physicists and engineers working in the field of low-temperature plasmas. Theoretical analysis and experimental measurements are complementary for investigating this complex medium. With simplified models the primary parameters, such as the electric and magnetic fields, as well as the densities of radicals, may be evaluated aiding the design of plasma systems. In this book, two articles address this theme. The first one discusses the use of simulation techniques, namely the fluid, particle-in-cell, and hybrid models. The aim is to provide beginners in this field with a sense of what can be accomplished by state-of-the-art computational models. An overview of these simulation techniques, with emphasis on their strengths and limitations, is presented. The second contribution is devoted to the analysis of the cathode region of glow discharges. The phenomenon of field reversal of the axial electric field in the negative glow of a direct current discharge has been discussed for some time in scientific literature. By reviewing those published works, this volume discusses the importance of the determination of the position where the field reversal occurs. Optical diagnostics are non-intrusive experimental methods, which help to clarify the role of active species in plasmas. Optical probes are easy to use and inexpensive. The third article presents the use of emission spectroscopy, more precisely actinometry and NO titration to determine active species in their ground state in flowing discharges. Two different applications of the flowing discharges are discussed: a) plasma sterilization through the study of E-coli bacteria inactivation, b) superficial modification of textile materials through the study of wool treatments. Development of non-thermal atmospheric discharges and their applications in medical procedures are a clear upcoming trend. The fourth article surveys several methods for generating cold plasmas under ambient conditions and indicates the most promising medical applications. These include: controlled tissue coagulation by an atmospheric argon jet (Argon Plasma Coagulation), bacterial disinfection using cold micro-plasmas and its relation to tissue-saving treatment of dental caries, and non-inflammatory tissue removal based on sub-lethal plasma stimulation of living cells. Typical diagnostic methods for assaying the influence of cold plasmas on cells and bacteria are described. Abatement processes of many atmospheric pollutants are important issues in the improvement of climate control. Processes are being established to improve elimination of gaseous wastes from the emitted effluents. Such efforts are motivated by the increasingly restrictive regulations concerning air quality. In particular, emissions of nitrogen oxides like NO and NO2 and some Volatile Organic Compounds (VOCs) will be prohibited without treatment. Many techniques of non-thermal equilibrium plasma generation in polluted N2/O2 wet or dry mixtures at atmospheric pressure are investigated. The aim is improvement in the performance of these plasmas for the elimination of either nitrogen oxides in lean-burn and gasoline engine exhaust gases, or VOCs emitted by chemical industry or present in indoor air. In order to understand the decomposition of the VOCs, the fifth paper analyses the kinetics of the OH radical in mixtures of atmospheric gases with hydrocarbons by time resolved Laser Induced Fluorescence in photo-triggered discharges. A further article presents the basic features of the magnetically enhanced capacitively coupled radio-frequency discharges. Properties of these discharges drastically depend on different discharge operating parameters, such as magnetic field, gas flow rate, pressure and composition, frequency, input power, and discharge geometry. The impact of these parameters on magnetically enhanced radio-frequency discharges was studied both in experimental and theoretical investigations. Technological applications of these discharges are presented. The last paper is an overview of the properties of the hollow cathode discharges operated in low and high-pressure. Gas breakdown and voltage-current characteristics are explained, taking into account the hollow cathode effect, which relies on parameters such as the cathode material, discharge power, and working gas. Electron field emission, stepwise processes, and tree-body reactions were observed in these discharges, characteristics that motivate the appearance of new applications in the field of science and industry. This volume is an up-to-date contribution to the applications of gas discharges, which may be useful for fundamentalists as well as those employing these systems in industry.