Physical characteristics of plasma antennas Rayner, J.P.; Whichello, A.P.; Cheetham, A.D.
IEEE transactions on plasma science,
02/2004, Letnik:
32, Številka:
1
Journal Article
Recenzirano
This experimental and theoretical study examines the excitation of a plasma antenna using an argon surface wave discharge operating at 500 MHz with RF power levels up to 120 W and gas pressures ...between 0.03 and 0.5 mb. The results show that the length of the plasma column increases as the square root of the applied power and that the plasma density decreases linearly from the wave launcher to the end of the plasma column. These results are consistent with a simple global model of the antenna. Since noise is critical to communication systems, the noise generated by the plasma was measured from 10 to 250 MHz. Between 50 and 250 MHz the excess noise temperature was found to be 17.2/spl plusmn/1.0 dB above 290 K. This corresponds to an ohmic thermal noise source at 1.4/spl plusmn/0.3 eV, compared with an electron temperature of 1.65 eV predicted by the global model. Estimates of the electrical conductivity of the plasma column based on measured electron number densities lead to an antenna efficiency of about 65% at a transmission frequency of 100 MHz and an increase in total antenna noise of 1 dB due to the plasma. Theoretical modeling and experimental observations of the radiation pattern of the antenna show that the linear variation of conductivity and finite resistance of the column lead to a reduction in the depth of the nulls in the radiation pattern and a consequent increase in the width of the main lobe.
Plasma technology has arisen as a novel approach in the processing and manufacturing of novel materials in recent years. Due to its benefits, such as its superior sterilizing performance, low cost, ...and environmental friendliness, atmospheric pressure plasma has drawn the attention of researchers. As a result, atmospheric pressure plasma manufacturing in different configurations (plan parallel and jet plasma) is becoming more popular. The necessity to characterize these types of plasmas has greatly expanded as a result of its wide range of applications. Due to these factors, “Recent Advances in Atmospheric-Pressure Plasma Technology” Issue in the journal Applied Physics that brings together experts in all areas of experimental, computational, and theoretical research on atmospheric pressure plasmas. This Special Issue brings together cutting-edge new research on the fundamental characteristics of these plasmas as well as their applications in the fields of medicine, the food industry, agriculture, 3D printing, materials processing science, and even the automotive and aerospace industries. Despite the fact that we were only able to touch on a small percentage of the potential applications for plasma discharge, we nevertheless hope that readers will find this reprint to be interesting and that they will discover new angles for their own future research on plasma.
This review describes the history and development of plasma-assisted catalysis focussing mainly on the use of atmospheric pressure, non-thermal plasma. It identifies the various interactions between ...the plasma and the catalyst that can modify and activate the catalytic surface and also describes how the catalyst affects the properties of the discharge. Techniques for in situ diagnostics of species adsorbed onto the surface and present in the gas-phase over a range of timescales are described. The effect of temperature on plasma-catalysis can assist in determining differences between thermal catalysis and plasma-activated catalysis and focuses on the meaning of temperature in a system involving non-equilibrium plasma. It can also help to develop an understanding of the gas-phase and surface mechanism of the plasma-catalysis at a molecular level. Our current state of knowledge and ignorance is highlighted and future directions suggested.
This rigorous explanation of plasmas is relevant to diverse plasma applications such as controlled fusion, astrophysical plasmas, solar physics, magnetospheric plasmas, and plasma thrusters. More ...thorough than previous texts, it exploits new powerful mathematical techniques to develop deeper insights into plasma behavior. After developing the basic plasma equations from first principles, the book explores single particle motion with particular attention to adiabatic invariance. The author then examines types of plasma waves and the issue of Landau damping. Magnetohydrodynamic equilibrium and stability are tackled with emphasis on the topological concepts of magnetic helicity and self-organization. Advanced topics follow, including magnetic reconnection, nonlinear waves, and the Fokker–Planck treatment of collisions. The book concludes by discussing unconventional plasmas such as non-neutral and dusty plasmas. Written for beginning graduate students and advanced undergraduates, this text emphasizes the fundamental principles that apply across many different contexts.
Reactive oxygen and nitrogen species (RONS) are among the key factors in plasma medicine. They are generated by atmospheric plasmas in biological fluids, living tissues and in a variety of liquids. ...This ability of plasmas to create a delicate mix of RONS in liquids has been used to design remote or indirect treatments for oncological therapy by treating biological fluids by plasmas and putting them in contact with the tumour. Documented effects include selective cancer cell toxicity, even though the exact mechanisms involved are still under investigation. However, the “right” dose for suitable therapeutical activity is crucial and still under debate. The wide variety of plasma sources hampers comparisons. This review focuses on atmospheric pressure plasma jets as the most studied plasma devices in plasma medicine and compiles the conditions employed to generate RONS in relevant liquids and the concentration ranges obtained. The concentrations of H
2
O
2
, NO
2
−
, NO
3
−
and short-lived oxygen species are compared critically to provide a useful overview for the reader.
Laser induced breakdown spectroscopy (LIBS) is basically an emission spectroscopy technique where atoms and ions are primarily formed in their excited states as a result of interaction between a ...tightly focused laser beam and the material sample. The interaction between matter and high-density photons generates a plasma plume, which evolves with time and may eventually acquire thermodynamic equilibrium. One of the important features of this technique is that it does not require any sample preparation, unlike conventional spectroscopic analytical techniques. Samples in the form of solids, liquids, gels, gases, plasmas and biological materials (like teeth, leaf or blood) can be studied with almost equal ease. LIBS has rapidly developed into a major analytical technology with the capability of detecting all chemical elements in a sample, of real- time response, and of close- contact or stand-off analysis of targets. The present book has been written by active specialists in this field, it includes the basic principles, the latest developments in instrumentation and the applications of LIBS. It will be useful to analytical chemists and spectroscopists as an important source of information and also to graduate students and researchers engaged in the fields of combustion, environmental science, and planetary and space exploration.* Recent research work * Possible future applications * LIBS Principles
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