Download or read book Feedback Control Of An Azimuthal Oscillation In The ExB Discharge of Hall Thrusters written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Feedback control of a low-frequency azimuthal wave known as a "rotating spoke" in the ExB discharge of a cylindrical Hall thruster was demonstrated. The rotating spoke is an m=1 azimuthal variation in density, electron temperature, and potential that rotates at about 10% of the local E x B electron rotation speed. It causes increased electron transport across the magnetic field and is suspected to be an ionization wave. Feedback control of this wave required special consideration because, although it causes a rotating azimuthal variation in the current density to the anode, it does not show up as a signal in the total thruster discharge current. Therefore, an extra source of information was needed to track the oscillation, which was addressed by using a special anode that was split azimuthally into four segments. The current to each segment oscillates as the rotating spoke passes over it, and feedback is accomplished by resistors connected in series with each anode segment which cause the voltage on a segment to decrease in proportion to the current through that segment. The feedback resulted in the disappearance of a coherent azimuthal wave and a decrease in the time-averaged total discharge current by up to 13.2%.
Download or read book Plasma Science and Technology written by Aamir Shahzad and published by BoD – Books on Demand. This book was released on 2022-02-23 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma science and technology (PST) is a discipline investigating fundamental transport behaviors, interaction physics, and reaction chemistry of plasma and its applications in different technologies and fields. Plasma has uses in refrigeration, biotechnology, health care, microelectronics and semiconductors, nanotechnology, space and environmental sciences, and so on. This book provides a comprehensive overview of PST, including information on different types of plasma, basic interactions of plasma with organic materials, plasma-based energy devices, low-temperature plasma for complex systems, and much more.
Download or read book Application of an Electric Field to Low Frequency Oscillation Control in Hall Thrusters written by Liqiu Wei and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to satisfy the national demands for developing a long-life satellite platform, lunar exploration, and deep-space exploitation, Hall thrusters are now considered the preferred candidate for spacecraft propulsion. A Hall thruster is a type of electric propulsion with an annular structure, in which a propellant, usually xenon, is ionized and then accelerated by electrostatic force to create a propulsive thrust. Low-frequency discharge current oscillations, also called breathing mode oscillations in some references, are among the major research topics of Hall thrusters. Low-frequency oscillations in the range of 10-100 kHz might affect the reliability of power processing unit and reduce the efficiency and specific impulse of Hall thrusters. The control of low-frequency oscillations is an essential challenge in the space application of Hall thrusters. It is proved that the electric field is a highly important influence factor for low-frequency oscillations; therefore, application of a dynamic electric field is a practical way to control low-frequency oscillation.
Download or read book Field Structure and Electron Transport in the Near field of Coaxial Hall Thrusters written by Andrew Wayne Smith and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Hall thruster is an electric propulsion device developed in the former USSR during the Cold War, capable of efficiently providing sustained, low-levels of thrust. Coaxial Hall thrusters are comprised of an annular channel (at the base of which the anode is generally found), and a series of electromagnets that produce a predominantly radial magnetic field near the channel exit. A cathode, located outside the annular channel, injects electrons that serve a dual purpose: they neutralize the ion beam, and they sustain the core discharge. They plasma ions can achieve considerable exhaust velocities, lending the Hall thruster a high specific impulse; however, the propellant flow rate is generally on the order of a few mg/s, keeping the overall thrust low. Despite their desirable high efficiency, the detailed physics of Hall thruster operation is not clearly understood. In particular, the mechanism by which electrons are able to diffuse across the magnetic field lines at a rate in excess of classical predictions is the subject of dispute and ongoing research. Rectifying this deficiency within the near-field region (defined to lie between the exit plane of the annular channel and the external cathode) is the primary motivation for this work. A clear understanding of the mechanisms of electron transport in the near-field can aid the development of more efficient thrusters and provide direction for future experiments. The present study approaches the problem on two fronts. First, an extensive, 3-D map of the plasma potential (in addition to the floating potential and electron temperature) is obtained via a series of time-resolved experiments. These transient measurements are referenced to the periodic oscillation in the discharge current of Hall thrusters (known as the breathing-mode) and provide an unprecedented visualization of the low-frequency field dynamics. Second, the electron transport physics in the near-field is investigated in 3-D, electron-kinetic simulations. These simulations implement the experimentally-observed plasma potential (and, in some cases, fluctuations in the plasma potential). These simulations demonstrate that the 3-D nature of the fields is an important driver of near-field transport; however, collisions with the front-face of the thruster are critical to the anomalous diffusion of electrons across the magnetic field lines in this region. In simulations that considered static fields, up to 35 % of the electrons reached the channel during simulated lifetimes exceeding 1 microsecond, but often yielded very inhomogeneous density distributions. Imposing the measured helical plasma potential fluctuations in the simulations resulted in a dramatic azimuthal homogenization of the electron density distribution, and reduced the fraction of electrons reaching the channel to about 10 %, on par with experimental observations. In every case tested, plasma potential fluctuations (both axial and helical at a variety of frequencies) reduced the electron current reaching the channel. The results further suggest that the location and orientation of the cathode (as well as the properties of the emitted electron beam) have a strong effect on the transport. Gas-phase collisions, even when allowed to occur at a greatly exaggerated rate, are found to have negligible effect on either the channel/beam current ratio or the density distribution in the near-field. These results also suggest that random turbulence in the plasma properties (at least for frequencies less than or equal to 10 MHz) is unlikely to significantly impact the net electron transport (i.e., the channel/beam current ratio or density distribution). Importantly, axisymmetric simulations are found to yield dramatically disparate results (often yielding zero electron-current transport to the channel) compared to the simulations that considered 3-D fields (which introduce azimuthal components in the electric and magnetic fields); a result which questions the validity of pervasive 2-D Hall thruster simulations.
Download or read book Investigating Newly Discovered Oscillation Modes in Magnetically Shielded Hall Effect Thrusters Utilizing High Speed Diagnostics written by Matthew Joseph Baird and published by . This book was released on 2020 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetically shielded Hall effect thrusters (MSHETs) are a variant of Hall effect thrusters (HET) that provide the favorable thrust-to-power ratio and high specific impulse of traditional stationary plasma type (STP) HETs but with an extremely long lifetime. MSHETs exhibit unique discharge plasma oscillations compared to traditional unshielded HETs. In this study, measurements of plasma oscillations in the state-of-the-art 12.5 kW Hall Effect Rocket with Magnetic Shielding (HERMeS) were obtained at various discharge voltages while holding other operation parameters constant. Data were collected using high-speed imaging, voltage, current, and plasma probes. The thruster exhibits two dominant oscillation modes within the discharge channel. The first mode is characterized as broadband turbulent oscillation in discharge current, and the second mode is a sinusoidal-like oscillation in discharge current. The oscillations in the discharge channel for both modes are predominantly global throughout the entire discharge and plume. The centrally mounted cathode exhibits a combination of global and localized "spoke" oscillation modes in the ExB direction. Discrete Fourier Transform (DFT) analysis of the high-speed data show the frequency and spoke number dependent dynamic coupling behaviors between the discharge channel and cathode. Moreover, the shape of the cathode mode was quantified at each operating condition using a phase surface analysis technique of the high-speed imaging data. Data from high-speed plasma probes show that oscillations in the cathode permeate into the discharge channel and could be, in part, responsible for driving oscillations in the discharge channel. A novel technique for reconstructing temporally resolved ion energy distribution functions (IEDF(t)) was developed and tested on several plasma sources. This method, called the high-speed retarding potential analyzer (HSRPA), combines a retarding potential analyzer and a high-speed transimpedance amplifier with an empirical transfer function technique previously employed in the spatiotemporal reconstruction of high-speed Langmuir probe data. The analysis technique was successful in reconstructing the IEDF(t) of a modulated gridded ion source and of a 200-W laboratory Hall thruster. The HSRPA was less effective when used to collect IEDF(t) data in the high polar angle regions of the HERMeS thruster plume, but it was able to provide ion energy dependent spectral content. The HSRPA developed was a preliminary proof-of-concept that worked successfully and with subtle improvements would provide a powerful diagnostic tool for enlightening further studies of plasma oscillations in MSHETs.
Download or read book Fundamentals of Electric Propulsion written by Dan M. Goebel and published by John Wiley & Sons. This book was released on 2008-12-22 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: Throughout most of the twentieth century, electric propulsion was considered the technology of the future. Now, the future has arrived. This important new book explains the fundamentals of electric propulsion for spacecraft and describes in detail the physics and characteristics of the two major electric thrusters in use today, ion and Hall thrusters. The authors provide an introduction to plasma physics in order to allow readers to understand the models and derivations used in determining electric thruster performance. They then go on to present detailed explanations of: Thruster principles Ion thruster plasma generators and accelerator grids Hollow cathodes Hall thrusters Ion and Hall thruster plumes Flight ion and Hall thrusters Based largely on research and development performed at the Jet Propulsion Laboratory (JPL) and complemented with scores of tables, figures, homework problems, and references, Fundamentals of Electric Propulsion: Ion and Hall Thrusters is an indispensable textbook for advanced undergraduate and graduate students who are preparing to enter the aerospace industry. It also serves as an equally valuable resource for professional engineers already at work in the field.
Download or read book Low perturbation Interrogation of the Internal and Near field Plasma Structure of a Hall Thruster Using a High speed Probe Positioning System written by James Matthew Haas and published by . This book was released on 2001 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Plasma Physics written by Alexander Piel and published by Springer. This book was released on 2017-09-07 with total page 473 pages. Available in PDF, EPUB and Kindle. Book excerpt: The enlarged new edition of this textbook provides a comprehensive introduction to the basic processes in plasmas and demonstrates that the same fundamental concepts describe cold gas-discharge plasmas, space plasmas, and hot fusion plasmas. Starting from particle drifts in magnetic fields, the principles of magnetic confinement fusion are explained and compared with laser fusion. Collective processes are discussed in terms of plasma waves and instabilities. The concepts of plasma description by magnetohydrodynamics, kinetic theory, and particle simulation are stepwise introduced. Space charge effects in sheath regions, double layers and plasma diodes are given the necessary attention. The novel fundamental mechanisms of dusty plasmas are explored and integrated into the framework of conventional plasmas. The book concludes with a concise description of modern plasma discharges. Written by an internationally renowned researcher in experimental plasma physics, the text keeps the mathematical apparatus simple and emphasizes the underlying concepts. The guidelines of plasma physics are illustrated by a host of practical examples, preferentially from plasma diagnostics. There, Langmuir probe methods, laser interferometry, ionospheric sounding, Faraday rotation, and diagnostics of dusty plasmas are discussed. Though primarily addressing students in plasma physics, the book is easily accessible for researchers in neighboring disciplines, such as space science, astrophysics, material science, applied physics, and electrical engineering. This second edition has been thoroughly revised and contains substantially enlarged chapters on plasma diagnostics, dusty plasmas and plasma discharges. Probe techniques have been rearranged into basic theory and a host of practical examples for probe techniques in dc, rf, and space plasmas. New topics in dusty plasmas, such as plasma crystals, Yukawa balls, phase transitions and attractive forces have been adopted. The chapter on plasma discharges now contains a new section on conventional and high-power impulse magnetron sputtering. The recently discovered electrical asymmetry effect in capacitive rf-discharges is described. The text is based on an introductory course to plasma physics and advanced courses in plasma diagnostics, dusty plasmas, and plasma waves, which the author has taught at Kiel University for three decades. The pedagogical approach combines detailed explanations, a large number of illustrative figures, short summaries of the basics at the end of each chapter, and a selection of problems with detailed solutions.
Download or read book Introduction to Plasma Physics and Controlled Fusion written by Francis F. Chen and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: TO THE SECOND EDITION In the nine years since this book was first written, rapid progress has been made scientifically in nuclear fusion, space physics, and nonlinear plasma theory. At the same time, the energy shortage on the one hand and the exploration of Jupiter and Saturn on the other have increased the national awareness of the important applications of plasma physics to energy production and to the understanding of our space environment. In magnetic confinement fusion, this period has seen the attainment 13 of a Lawson number nTE of 2 x 10 cm -3 sec in the Alcator tokamaks at MIT; neutral-beam heating of the PL T tokamak at Princeton to KTi = 6. 5 keV; increase of average ß to 3%-5% in tokamaks at Oak Ridge and General Atomic; and the stabilization of mirror-confined plasmas at Livermore, together with injection of ion current to near field-reversal conditions in the 2XIIß device. Invention of the tandem mirror has given magnetic confinement a new and exciting dimension. New ideas have emerged, such as the compact torus, surface-field devices, and the EßT mirror-torus hybrid, and some old ideas, such as the stellarator and the reversed-field pinch, have been revived. Radiofrequency heat ing has become a new star with its promise of dc current drive. Perhaps most importantly, great progress has been made in the understanding of the MHD behavior of toroidal plasmas: tearing modes, magnetic Vll Vlll islands, and disruptions.
Download or read book Plasma Engineering written by Michael Keidar and published by Academic Press. This book was released on 2018-08-06 with total page 587 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma Engineering, Second Edition, applies the unique properties of plasmas (ionized gases) to improve processes and performance over many fields, such as materials processing, spacecraft propulsion and nanofabrication. The book considers this rapidly expanding discipline from a unified standpoint, addressing fundamentals of physics and modeling, as well as new and real-word applications in aerospace, nanotechnology and bioengineering. This updated edition covers the fundamentals of plasma physics at a level suitable for students using application examples and contains the widest variety of applications of any text on the market, spanning the areas of aerospace engineering, nanotechnology and nanobioengineering. This is highly useful for courses on plasma engineering or plasma physics in departments of Aerospace Engineering, Electrical Engineering and Physics. It is also useful as an introduction to plasma engineering and its applications for early career researchers and practicing engineers. Features new material relevant to application, including emerging areas of plasma nanotechnology and medicine Contains a new chapter on plasma-based control, as well as a description of RF and microwave-based plasma applications, plasma lighting, reforming and other most recent application areas Provides a technical treatment of the fundamental and engineering principles used in plasma applications
Download or read book Performance Evaluation of the SPT 140 written by and published by . This book was released on 1997 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Instabilities of a Homogeneous Plasma written by A. B. Mikhailovskii and published by Springer. This book was released on 1974-02 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Micropropulsion for Small Spacecraft written by Michael Matthew Micci and published by AIAA. This book was released on 2000 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cathodic Arcs written by André Anders and published by Springer Science & Business Media. This book was released on 2009-07-30 with total page 555 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cathodic arcs are among the longest studied yet least understood objects in science. Plasma-generating, tiny spots appear on the cathode; they are highly dynamic and hard to control. With an approach emphasizing the fractal character of cathode spots, strongly fluctuating plasma properties are described such as the presence of multiply charged ions that move with supersonic velocity. Richly illustrated, the book also deals with practical issues, such as arc source construction, macroparticle removal, and the synthesis of dense, well adherent coatings. The book spans a bridge from plasma physics to coatings technology based on energetic condensation, appealing to scientists, practitioners and graduate students alike.
Download or read book The ROV Manual written by Robert D Christ and published by Elsevier. This book was released on 2011-04-01 with total page 327 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ROV Manual: A User Guide for Observation-Class Remotely Operated Vehicles is the first manual to provide a basic ""How To"" for using small observation-class ROVs for surveying, inspection and research procedures. It serves as a user guide that offers complete training and information about ROV operations for technicians, underwater activities enthusiasts, and engineers working offshore. The book focuses on the observation-class ROV and underwater uses for industrial, recreational, commercial, and scientific studies. It provides information about marine robotics and navigation tools used to obtain mission results and data faster and more efficiently. This manual also covers two common denominators: the technology and its application. It introduces the basic technologies needed and their relationship to specific requirements; and it helps identify the equipment essential for a cost-effective and efficient operation. This user guide can be invaluable in marine research and surveying, crime investigations, harbor security, military and coast guarding, commercial boating, diving and fishing, nuclear energy and hydroelectric inspection, and ROV courses in marine and petroleum engineering. * The first book to focus on observation class ROV (Remotely Operated Vehicle) underwater deployment in real conditions for industrial, commercial, scientific and recreational tasks * A complete user guide to ROV operation with basic information on underwater robotics and navigation equipment to obtain mission results quickly and efficiently * Ideal for anyone involved with ROVs complete with self-learning questions and answers
Download or read book Electric Propulsion Development written by Ernst Stuhlinger and published by Elsevier. This book was released on 1963-01-01 with total page 763 pages. Available in PDF, EPUB and Kindle. Book excerpt: Progress in Astronautics and Aeronautics, Volume 9: Electric Propulsion Development covers the proceedings of the Second Electric Propulsion Conference of the American Rocker Society, held in Berkeley, California on March 14-16, 1962. The conference focuses on the existing problems in electric propulsion and their possible solutions. This book is organized into four sections encompassing 35 chapters. The first section deals with the thermodynamics of arcs; the problems of heat and momentum transfer; the chemical processes within arcs; the arc system materials; and the arc jet design problems. The second section considers the problems of ion systems, the various ion sources, and the neutralization of ion beams. This section also looks into the basic ionization processes, the production and charging of heavy particles, the corrosive properties of cesium, and the ion-optical designs. The third section describes various plasma systems, including helical transmission lines, pulsed pinch accelerators, coaxial systems, and j x B accelerators. The theoretical analyses of these systems are briefly examined. The fourth section includes papers on flight testing of electric propulsion models, on vertical rocket probes, and on satellites, This section also discusses some advanced concepts in electric propulsion, such as air scooping during ascent through the atmosphere, systems design and optimization, and planetary and interplanetary missions. This book is of great value to physicists, space engineers and designers, as well as researchers in the fields of astronautics and aeronautics.
Download or read book Nondestructive Materials Characterization written by Norbert G. H. Meyendorf and published by Springer Science & Business Media. This book was released on 2013-11-21 with total page 435 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an emphasis on aircraft materials, this book describes techniques for the material characterization to detect and quantify degradation processes such as corrosion and fatigue. It introduces readers to these techniques based on x-ray, ultrasonic, optical and thermal principles and demonstrates the potential of the techniques for a wide variety of applications concerning aircraft materials, especially aluminum and titanium alloys. The advantages and disadvantages of various techniques are evaluated.
