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 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 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 Radio Frequency Power in Plasmas written by Philip M. Ryan and published by American Institute of Physics. This book was released on 2007-10-03 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clearwater, Florida, 7-9 May 2007
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 902 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Dynatron written by Donald Menzies Bennett and published by . This book was released on 1921 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book RCA Review written by and published by . This book was released on 1963 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
