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Author: Marlene Idy Patino Publisher: ISBN: Category : Languages : en Pages : 219
Book Description
An improved understanding of plasma inter-particle and particle-wall interactions is critical to the advancement of plasma devices used for space electric propulsion, fusion, high-power communications, and next-generation energy systems. Two interactions of particular importance are (1) ion-atom collisions in the plasma bulk and (2) secondary electron emission from plasma-facing materials. For ion-atom collisions, interactions between fast ions and slow atoms are commonly dominated by charge-exchange and momentum-exchange collisions that are important to understanding the performance and behavior of many plasma devices. To investigate this behavior, this work developed a simple, well-characterized experiment that accurately measures the effects of high energy xenon ions incident on a background of xenon neutral atoms. By comparing these results to both analytical and computational models of ion-atom interactions, we discovered the importance of (1) accurately treating the differential cross-sections for momentum-exchange and charge-exchange collisions over all neutral background pressures, and (2) commonly overlooked interactions, including ion-induced electron emission and neutral-neutral ionization collisions, at high pressures. Data provide vital information on the angular scattering distributions of charge-exchange and momentum-exchange ions at 1.5 keV relevant for ion thrusters, and serve as canonical data for validation of plasma models. This work also investigates electron-induced secondary electron emission behavior relevant to materials commonly considered for plasma thrusters, fusion systems, and many other plasma devices. For such applications, secondary electron emission can alter the sheath potential, which can significantly affect device performance and life. Secondary electron emission properties were measured for materials that are critical to the efficient operation of many plasma devices, including: graphite (for tokamaks, ion thrusters, and traveling wave tubes), lithium (for tokamak walls), tungsten (the most promising material for future tokamaks such as ITER), and nickel (for plasma-enhanced chemistry). Measurements were made for incident electron energies up to 1.5 keV and angles between 0 and 78i . The most significant results from these measurements are as follows: (1) first-ever measurements of naturally-forming tungsten fuzz show a more than 40% reduction in secondary electron emission and an independence on incidence angle; (2) original measurements of lithium oxide show a 2x and 6x increase in secondary electron emission for 17% and 100% oxidation; and (3) unique measurements of Ni(110) single crystal show extrema in secondary electron emission when incidence angle is varied and an up to 36% increase at 0i over polycrystalline nickel. Each of these results are important discoveries for improving plasma devices. For example, from (1), the growth of tungsten fuzz in tokamaks is desirable for minimizing adverse secondary electron emission effects. From (2), the opposite is true for tokamaks with lithium coatings which are oxidized by typical residual gases. From (3), secondary electron emission from Ni(110) catalysts in plasma-enhanced chemistry may facilitate further reactions.
Author: Marlene Idy Patino Publisher: ISBN: Category : Languages : en Pages : 219
Book Description
An improved understanding of plasma inter-particle and particle-wall interactions is critical to the advancement of plasma devices used for space electric propulsion, fusion, high-power communications, and next-generation energy systems. Two interactions of particular importance are (1) ion-atom collisions in the plasma bulk and (2) secondary electron emission from plasma-facing materials. For ion-atom collisions, interactions between fast ions and slow atoms are commonly dominated by charge-exchange and momentum-exchange collisions that are important to understanding the performance and behavior of many plasma devices. To investigate this behavior, this work developed a simple, well-characterized experiment that accurately measures the effects of high energy xenon ions incident on a background of xenon neutral atoms. By comparing these results to both analytical and computational models of ion-atom interactions, we discovered the importance of (1) accurately treating the differential cross-sections for momentum-exchange and charge-exchange collisions over all neutral background pressures, and (2) commonly overlooked interactions, including ion-induced electron emission and neutral-neutral ionization collisions, at high pressures. Data provide vital information on the angular scattering distributions of charge-exchange and momentum-exchange ions at 1.5 keV relevant for ion thrusters, and serve as canonical data for validation of plasma models. This work also investigates electron-induced secondary electron emission behavior relevant to materials commonly considered for plasma thrusters, fusion systems, and many other plasma devices. For such applications, secondary electron emission can alter the sheath potential, which can significantly affect device performance and life. Secondary electron emission properties were measured for materials that are critical to the efficient operation of many plasma devices, including: graphite (for tokamaks, ion thrusters, and traveling wave tubes), lithium (for tokamak walls), tungsten (the most promising material for future tokamaks such as ITER), and nickel (for plasma-enhanced chemistry). Measurements were made for incident electron energies up to 1.5 keV and angles between 0 and 78i . The most significant results from these measurements are as follows: (1) first-ever measurements of naturally-forming tungsten fuzz show a more than 40% reduction in secondary electron emission and an independence on incidence angle; (2) original measurements of lithium oxide show a 2x and 6x increase in secondary electron emission for 17% and 100% oxidation; and (3) unique measurements of Ni(110) single crystal show extrema in secondary electron emission when incidence angle is varied and an up to 36% increase at 0i over polycrystalline nickel. Each of these results are important discoveries for improving plasma devices. For example, from (1), the growth of tungsten fuzz in tokamaks is desirable for minimizing adverse secondary electron emission effects. From (2), the opposite is true for tokamaks with lithium coatings which are oxidized by typical residual gases. From (3), secondary electron emission from Ni(110) catalysts in plasma-enhanced chemistry may facilitate further reactions.
Author: D. E. Post Publisher: Springer ISBN: Category : Science Languages : en Pages : 1208
Book Description
Controlled thermonuclear fusion is one of the possible candidates for long term energy sources which will be indispensable for our highly technological society. However, the physics and technology of controlled fusion are extremely complex and still require a great deal of research and development before fusion can be a practical energy source. For producing energy via controlled fusion a deuterium-tritium gas has to be heated to temperatures of a few 100 Million °c corres ponding to about 10 keV. For net energy gain, this hot plasma has to be confined at a certain density for a certain time One pro mising scheme to confine such a plasma is the use of i~tense mag netic fields. However, the plasma diffuses out of the confining magnetic surfaces and impinges on the surrounding vessel walls which isolate the plasma from the surrounding air. Because of this plasma wall interaction, particles from the plasma are lost to the walls by implantation and are partially reemitted into the plasma. In addition, wall atoms are released and can enter the plasma. These wall atoms or impurities can deteriorate the plasma performance due to enhanced energy losses through radiation and an increase of the required magnetic pressure or a dilution of the fuel in the plasma. Finally, the impact of the plasma and energy on the wall can modify and deteriorate the thermal and mechanical pro perties of the vessel walls.
Author: Oliver James Pike Publisher: Springer ISBN: 331963447X Category : Science Languages : en Pages : 154
Book Description
This thesis makes two important contributions to plasma physics. The first is the extension of the seminal theoretical works of Spitzer and Braginskii, which describe the basics of particle interactions in plasma, to relativistic systems. Relativistic plasmas have long been studied in high-energy astrophysics and are becoming increasingly attainable in the laboratory. The second is the design of a new class of photon–photon collider, which is the first capable of detecting the Breit–Wheeler process. Though it offers the simplest way for light to be converted into matter, the process has never been detected in the 80 years since its theoretical prediction. The experimental scheme proposed here exploits the radiation used in inertial confinement fusion experiments and could in principle be implemented in one of several current-generation facilities.
Author: I.T. Iakubov Publisher: Springer Science & Business Media ISBN: 1489910662 Category : Science Languages : en Pages : 326
Book Description
The book is devoted to the physical properties of nonideal plasma, in which the effects of interparticle interactions are substantial. Such a plasma is usually compressed so strongly that it is called dense plasma. Interest in plasma studies has increased over the last 10 or 15 years, owing to the development of modern technology and sophisticated facilities whose oper ation is based on a high energy density. As a result of a recent sharp increase in the number of experimental and theoretical investigations, much interesting and reliable data on the properties of dense plasma have been obtained. The data are distributed in a rapidly growing number of original publications and reviews. This volume is a systematic treatment of the thermodynamics (ionization equilibrium, particle composition), charge transport properties (especially electric con ductivity), optical properties (peculiarities of continuous and discrete spectra), and collective modes (features and manifestations) of nonideal plasma. Theoretical models are considered along with the experimental data. The book is intended for the wide range of readers, including specialists in plasma physics and various researchers who need knowledge in this field.
Author: Urszula Ledzewicz Publisher: Springer Science & Business Media ISBN: 1461441773 Category : Mathematics Languages : en Pages : 426
Book Description
Mathematical biomedicine is a rapidly developing interdisciplinary field of research that connects the natural and exact sciences in an attempt to respond to the modeling and simulation challenges raised by biology and medicine. There exist a large number of mathematical methods and procedures that can be brought in to meet these challenges and this book presents a palette of such tools ranging from discrete cellular automata to cell population based models described by ordinary differential equations to nonlinear partial differential equations representing complex time- and space-dependent continuous processes. Both stochastic and deterministic methods are employed to analyze biological phenomena in various temporal and spatial settings. This book illustrates the breadth and depth of research opportunities that exist in the general field of mathematical biomedicine by highlighting some of the fascinating interactions that continue to develop between the mathematical and biomedical sciences. It consists of five parts that can be read independently, but are arranged to give the reader a broader picture of specific research topics and the mathematical tools that are being applied in its modeling and analysis. The main areas covered include immune system modeling, blood vessel dynamics, cancer modeling and treatment, and epidemiology. The chapters address topics that are at the forefront of current biomedical research such as cancer stem cells, immunodominance and viral epitopes, aggressive forms of brain cancer, or gene therapy. The presentations highlight how mathematical modeling can enhance biomedical understanding and will be of interest to both the mathematical and the biomedical communities including researchers already working in the field as well as those who might consider entering it. Much of the material is presented in a way that gives graduate students and young researchers a starting point for their own work.
Author: Marlene Idy Patino
Author: Marlene Idy Patino
Author: D. E. Post
Author: D. E. Post
Author: Sören Möller
Author: Oliver James Pike
Author: I.T. Iakubov
Author: Sam Stuart
Author: 
Author: Urszula Ledzewicz
Author: