Download or read book MULTIPACTOR DISCHARGE EXPERIMENTS written by Edward F. Vance and published by . This book was released on 1967 with total page 61 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental investigation of the multipactor discharge mechanism was conducted to determine the effect of dc bias, electrode materials, and electrode geometry on the RF voltage required for initiation of the discharge. The experiments showed that most of the commonly used aerospace materials support multipactor discharges, and that the discharge can occur over a wide range of bias voltages. The experiments were conducted with a parallel-plate geometry, a coaxial geometry and with the cone-plane configuration of a discone antenna. All of the coaxial electrode geometries support multipactor discharges, and the discone configurations with cone half-angles greater than 60 degrees supported the discharges. Attempts to measure the RF power dissipated by the discharge indicated that this power was relatively small, so the main detrimental effect of the multipactor discharge on RF systems in space will be in detuning high-Q circuits and in the possibility of more serious failure mechanisms being induced by the multipactor discharge. (Author).
Download or read book The Coaxial Multipactor Experiment CMX written by Graves Timothy P. (Timothy Paul) and published by . This book was released on 2005 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A multipactor discharge is a resonant condition for electrons in an alternating electric field. This discharge can be disruptive to radio frequency (RF) circuits, cavities, and resonators. The Coaxial Multipactor Experiment (CMX) investigates these discharges in parallel plate and coaxial transmission line geometries at frequencies from 40 to 150 MHz with goals of measuring the electron energy distributions. CMX has a unique experimental setup which allows the transmission line to pass continuously through a short vacuum region. Retarding potential analyzers with secondary electron suppression measure the electron current as a function of bias voltage. Both parallel plate and coaxial multipactor experiments provide the first detailed measurements of the electron energy distributions under a variety of RF frequencies and electrode materials.
Download or read book Experimental Investigation of Electron Multipactor Discharges at Very High Frequency written by Timothy Paul Graves and published by . This book was released on 2006 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multipactor discharges are a resonant condition in which electrons impact a surface in phase with an alternating electric field. The discharge is sustained by electron multiplication from secondary emission. As motivation, multipactor discharges can adversely affect many different rf systems in vacuum, and this work provides an improved general understanding of multipactor and gives promising results for improved performance and reliability of these systems. The Coaxial Multipactor Experiment (CMX) creates and investigates multipactor discharges in both parallel plate and coaxial geometries at very high frequency (VHF). CMX provides the first detailed investigation of multipactor energy distribution functions for both coaxial and parallel plate geometries with the use of retarding potential analyzers (RPA). A 1-D particle tracking simulation supports these experimental distributions and yields the underlying physics behind the distribution shape. Experimental and simulation energy distributions have a low energy population of defocused electrons due to space charge effects and RPA emission, and a high energy population responsible for sustaining the discharge. Results show a higher energy distribution for the coaxial geometry as compared to the parallel plate geometry with the same electrode spacing, implying that coaxial geometries are more susceptible to multipactor. These results are supported by CMX susceptibility data, which are provided for both coaxial and parallel plate electrodes. Lastly, similar multipactor experiments were performed on Alcator C-Mod rf systems, allowing the discovery of multipactor-induced glow discharge in these systems. Results suggest the onset of this glow discharge causes the observed C-Mod neutral pressure limits. These results are further supported by CMX experiments, and a new, 50 [micro]m sandblasted copper surface treatment has been shown to sufficiently lower [delta]
Download or read book The Study of Multipactor Breakdown in Space Electronic Systems Final Report written by and published by . This book was released on 1966 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multipactor Experiment on a Dielectric Surface written by Rex Beach Anderson (III.) and published by . This book was released on 2001 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Multipactor Discharge written by and published by . This book was released on 2005 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several comprehensive studies of radio frequency (rf) breakdown and rf heating are reported. They are of general interest to magnetic confinement fusion, rf linac, and high power microwave source development. The major results include: (1) a ground-breaking theory of multipactor discharge on dielectric, including a successful proof-of-principle experiment that verified the newly developed scaling laws, (2) an in depth investigation of the failure mechanisms of diamond windows and ceramic windows, and of the roles of graphitization, thin films of coating and contaminants, and (3) a most comprehensive theory, to date, on the heating of particulates by an electromagnetic pulse, and on the roles of rf magnetic field heating and of rf electric field heating, including the construction of new scaling laws that govern them. The above form a valuable knowledge base for the general problem of heating phenomenology.
Download or read book The Study of Multipactor Breakdown in Space Electronic Systems written by and published by . This book was released on 1966 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book One sided Multipactor Discharge Modes written by Edward F. Vance and published by . This book was released on 1963 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies of Dielectric Multipactor Discharges and Gas Breakdown Initiated by High Power Millimeter Waves written by Samuel Clay Schaub and published by . This book was released on 2019 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis reports the theoretical and experimental investigation of discharge phenomena induced at dielectric surfaces and in gases by a 1.5 MW, 110 GHz gyrotron operating in 3 [mu]s pulses. The experimental study of multipactor discharges on dielectric surfaces in vacuum was performed at 110 GHz, a frequency that is an order of magnitude higher than in previous experimental studies. Two separate test assemblies were constructed: one with the 110 GHz electric field tangential to the dielectric surface and the second with a perpendicular field. Threshold electric fields for multipactor onset were measured in both field orientations for samples of sapphire, alumina, fused quartz, crystal quartz and silicon. The present results at 110 GHz, when combined with previously published data at lower frequencies, show that the threshold electric field for initiation of a dielectric multipactor discharge scales linearly with frequency. This linear scaling, which is favorable for operation at high frequency, is in good agreement with theoretical predictions. The absorbed RF power due to multipactor was also measured as a function of RF intensity. At low intensities, absorbed RF power was found to agree quantitatively with theoretical predictions, though experimental results diverged from theory at higher RF intensities. Calculations of dielectric multipactor were carried out to help analyze the experimental results. A new equation for predicting threshold RF electric fields was derived that agrees with a wide variety of existing experimental data, spanning orders of magnitude in frequency and a variety of geometries and materials. The theory work also suggests strategies for mitigation of multipactor, dependent upon experimental geometry. Gas breakdowns were experimentally characterized at both 110 and 124.5 GHz by focusing the gyrotron beam in air at pressures from 25 to 760 Torr. Prior studies of this system had revealed that the plasma spontaneously forms a reproducible twodimensional array of filaments. Optical emission spectroscopy was used to measure peak electron density in this plasma, through Stark broadening of the H[subscript alpha] line. Heating dynamics of the background neutral gas were spatially and temporally resolved using two-dimensional laser interferometry. These results hell) test the theory of gas breakdown at 110 GHz.
Download or read book Studies of Coaxial Multipactor in the Presence of a Magnetic Field written by Becerra Toledo Becerra and published by . This book was released on 2007 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multipactor discharges consists of electron multiplication between two surfaces by secondary electron emission in resonance with an alternating electric field. They are detrimental to the performance of radio frequency (RF) systems, such as the ICRF (ion cyclotron range of frequencies) antennas for heating of plasmas in the Alcator C-Mod tokamak and other nuclear fusion devices. This work investigates multipactor discharges in the coaxial geometry in the presence of a constant and uniform magnetic field transverse to the direction of electromagnetic wave propagation. Studies on the Coaxial Multipactor Experiment (CMX) show that the magnetic field decreases the degree to which the discharge detunes the RF circuit. However, it enhances the susceptibility of the system to multipactor-induced gas breakdown at low pressures, which appears to cause the observed neutral pressure limits on antenna performance in Alcator C-Mod. Different surface treatment methods involving roughening and in-situ cleaning failed to suppress the multipactor discharges in a consistent and reliable way in experiments on CMX, despite the success of similar techniques in the parallel-plate geometry. Electron trajectories are significantly more complicated in the presence of magnetic fields of different strengths, as shown by a three-dimensional particle-tracking simulation using Monte Carlo sampling techniques. The trends in electron path length, time of flight, impact energy, secondary emission yield and population growth do not account for the experimental observations between the low and high field limits. These appear to be better explained by collective effects not included in the simulations, such as the effect of the magnetic field on charged particle diffusion.
Download or read book Simulation Method of Multipactor and Its Application in Satellite Microwave Components written by Wanzhao Cui and published by CRC Press. This book was released on 2021-09-12 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book combines the experience and achievements in engineering practice of the China Academy of Space Technology, Xi’an, with a focus on the field of high-power multipactor over recent decades. It introduces the main concepts, theories, methods and latest technologies of multipactor simulation, at both the theoretical level and as a process of engineering, while providing a comprehensive introduction to the outstanding progress made in the research technology of multipactor numerical simulation in China. At the same time, a three-dimensional numerical simulation method of multipactor for typical high-power microwave components of spacecraft is introduced. This book is an essential volume for engineers in the field of high-power microwave technology. It can also be used as a reference for researchers in related fields, or as a teaching reference book for graduate students majoring in Astronautics at colleges and universities.
Download or read book Multipactor in Accelerating Cavities written by Valery D. Shemelin and published by Springer Nature. This book was released on 2020-08-10 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is written by two world-recognized experts in radio frequency (RF) systems for particle accelerators and is based on many years of experience in dealing with the multipactor phenomenon. The authors introduce and review multipactor in RF cavities for scientists and engineers working in the field of accelerator physics and technology. The multipactor phenomenon of unintended electron avalanches occurs in the RF cavities commonly and quite often is a performance-limiting factor. The book starts with an Introductory Overview which contains historical observations and brief description of most common aspects of the phenomenon. Part I deals with the multipactor in a flat gap. It starts with description of the dynamics of electrons, derivation of the stability condition and analyzing influence of several factors on the multipactor. Then, the initial considerations are extended to derive a generalized phase stability and finally a particular case, called ping-pong multipacting, is considered. The part one is concluded with a brief review of computer codes used in multipactor simulations. Part II is dedicated to the multipactor in crossed RF fields, the typical situation in accelerating cavities. Two cases of MP are considered: a two-point multipactor near the cavity equator in elliptical cavities and a one-point multipactor. Part III describes optimization of the cavity shapes geared toward designing multipactor-free structures. The book will serve as an importance reference on multipactor for those involved in developing and operating radio frequency cavities for particle accelerators.
Download or read book Multipactor Discharge written by Maria Buyanova and published by . This book was released on 2006 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Interaction of Multipactor Discharge and Rf Structures written by Rami Alfred Kishek and published by . This book was released on 1997 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the Third Symposium on the Plasma Sheath Plasma Electromagnetics of Hypersonic Flight Electrical properties of shock ionized flow fields written by and published by . This book was released on 1967 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is a collection of the unclassified papers presented at the Third Symposium on the Plasma Sheath-Plasma Electromagnetics of Hypersonic Flight. This symposium consisted of the review of progress in reentry communication studies during the three year period since the prior meeting. The program of this symposium on plasma electromagnetics of hypersonic flight involves a wide range of scientific disciplines, including electromagnetics, aerodynamics, aero-thermochemistry, plasma dynamics, electronics, and high- temperature phenomena. The papers were selected to explore as many of these facets of research, including the results of laboratory, flight, and system tests, as time permitted.
Download or read book Multipactor Discharge written by Ágúst Valfells and published by . This book was released on 2000 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Instruments and Experimental Techniques written by and published by . This book was released on 1968 with total page 840 pages. Available in PDF, EPUB and Kindle. Book excerpt:
