Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Download Development Of A Low Energy Positron Beam full books in PDF, epub, and Kindle. Read online Development Of A Low Energy Positron Beam ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Author : Sujata Vemuri
Publisher :
ISBN 13 :
Total Pages : 234 pages
Book Rating : 4.:/5 (284 download)
Download or read book Development of a Low Energy Positron Beam written by Sujata Vemuri and published by . This book was released on 1993 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Paul G. Coleman
Publisher : World Scientific
ISBN 13 : 9789810233945
Total Pages : 348 pages
Book Rating : 4.2/5 (339 download)
Download or read book Positron Beams and Their Applications written by Paul G. Coleman and published by World Scientific. This book was released on 2000 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a coherent and comprehensive overview of the generation and application of mono-energetic positron beams. It has been written by acknowledged experts, at a level accessible to graduate students working, or planning to work, with positron beams, and to scientists in other areas who want to know something about the field.The book begins with a brief historical introduction and an overview of how positron beams are generated and transported. A description of the fate of slow positrons in gaseous and condensed matter, with reference to many of the fundamental measurements made possible by the advent of positron beams, is followed by a discussion on applications in the study of solid surfaces, defect profiling in subsurface regions, interfaces and thin films, and the probing of bulk properties in novel ways. The book ends with a look at the future, considering the prospects for intense positron beams and their potential for further research.
Author :
Publisher :
ISBN 13 :
Total Pages : 292 pages
Book Rating : 4.:/5 (94 download)
Download or read book Development of Low Energy Positron Beams and Their Application to the Study of the Surface Region in Metals written by and published by . This book was released on 1988 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : S. J. Gilbert
Publisher :
ISBN 13 :
Total Pages : 11 pages
Book Rating : 4.:/5 (228 download)
Download or read book Low-Energy Positron-Matter Interactions Using Trap-Based Beams written by S. J. Gilbert and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present an overview of nonneutral plasma techniques developed to study the interaction of low-energy positrons with atoms and molecules. Both scattering and positron annihilation experiments are described. The scattering experiments provide the first state-resolved cross sections for both vibrational excitation of molecules and electronic excitation of atoms and molecules by positron impact. The annihilation experiments provide the first energy-resolved measurements of positron annihilation. Extensions of these techniques are briefly discussed, including work to create a new generation of positron beams with multi-electron volt energy resolution and the development of methods to study atomic clusters and dust grains.
Author : Steven Jay Gilbert
Publisher :
ISBN 13 :
Total Pages : 262 pages
Book Rating : 4.:/5 (318 download)
Download or read book A New Ultra-cold Positron Beam and Applications to Low-energy Positron Scattering and Electron-positron Plasmas written by Steven Jay Gilbert and published by . This book was released on 2000 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Paul Walter Hietala
Publisher :
ISBN 13 :
Total Pages : 81 pages
Book Rating : 4.:/5 (222 download)
Download or read book A Low-energy Positron Beam System written by Paul Walter Hietala and published by . This book was released on 1968 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Dan Chen
Publisher : Open Dissertation Press
ISBN 13 : 9781374666658
Total Pages : pages
Book Rating : 4.6/5 (666 download)
Download or read book A Novel Design of a Variable Energy Positron Lifetime Beam written by Dan Chen and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "A Novel Design of a Variable Energy Positron Lifetime Beam" by Dan, Chen, 陳丹, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled A NOVEL DESIGN OF A VARIABLE ENERGY POSITRON LIFETIME BEAM Submitted by Chen Dan for the degree of Master of Philosophy at The University of Hong Kong in December 2007 Positron annihilation lifetime spectroscopy (PALS) is known to be a sensitive method for characterizing vacancy type defects in materials and thus tends to be the most popular of the positron annihilation techniques. Conventional PALS, which is 22 normally based on the emission of positrons from Na, works only on bulk samples since the penetration depth of the positrons from this isotope is large and not controllable. In order to study the defects in thin films or at material surfaces, however, it is highly desirable to employ PALS with a slow positron beam which has the capability of varying the incident positron energy and hence the mean positron implantation depth. Such a depth profiling PALS system is referred to in the present work as Variable Energy Positron Annihilation Lifetime Spectroscopy (VEPALS). The problem of constructing a VEPALS system, however, is the absence of a start signal for a positron entering a sample when using a positron beam. One of the ways of furnishing the necessary start signal is the usage of secondary electrons emitted when the positron strikes the sample. This method, however, suffers from two drawbacks. First the efficiency of the secondary emission varies from sample to sample. Second the timing resolution is usually poor (typically 400 to 800ps) due to the variation of secondary electron energies. The new VEPALS design presented in this thesis offers a novel approach to solving these problems. It is based on the emission of secondary electrons produced when the positron beam passes through a 25nm thick carbon foil located in front of the sample. A needle of 30μm diameter is positioned on-axis right behind the foil, creating a radial electric field that deflects the secondary electrons radially outwards sufficiently so as to miss the sample and to hit a micro channel plate (MCP) detector placed down beam. The MCP signal provides the start-signal for the positron lifetime spectrometer. The design has a cylindrical symmetry that reduces the experimental complexity. Moreover the small variations in secondary electron path length results in good timing resolution (= 500eV) of the positron beam. DOI: 10.5353/th_b3955879 Subjects: Positron beams Positron annihilation Electrons - Emission
Author :
Publisher :
ISBN 13 :
Total Pages : 9 pages
Book Rating : 4.:/5 (684 download)
Download or read book Positron Beam Lifetime Spectroscopy at Lawrence Livermore National Laboratory written by and published by . This book was released on 1996 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Defect analysis is needed for samples ranging in thickness from thin films to large engineering parts. We are meeting that need with two positron beam lifetime spectrometers: on on a 3 MeV electrostatic accelerator and the second on our high current linac beam. The high energy beam spectrometer performs positron lifetime analysis on thick samples which can be encapsulated for containment or for in situ measurements in controlled environments. At our high current beam, we are developing a low energy, microscopically focused, pulsed positron beam to enable positron annihilation lifetime spectroscopy for defect specific, 3-D maps with sub-micron location resolution. The data from these instruments with the aid of first principles calculations of defect specific positron lifetimes.
Author : Michael Ryan Natisin
Publisher :
ISBN 13 :
Total Pages : 235 pages
Book Rating : 4.:/5 (945 download)
Download or read book Trap-Based Beam Formation Mechanisms and the Development of an Ultra-High-Energy-Resolution Cryogenic Positron Beam written by Michael Ryan Natisin and published by . This book was released on 2016 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this dissertation is the development of a positron beam with significantly improved energy resolution over any beam resolution previously available. While positron interactions with matter are important in a variety of contexts, the range of experimental data available regarding fundamental positron-matter interactions is severely limited as compared to analogous electron-matter processes. This difference is due largely to the difficulties encountered in creating positron beams with narrow energy spreads. Described here is a detailed investigation into the physical processes operative during positron cooling and beam formation in state-of-the-art, trap-based beam systems. These beams rely on buffer gas traps (BGTs), in which positrons are trapped and cooled to the ambient temperature (300~K) through interactions with a molecular gas, and subsequently ejected as a high resolution pulsed beam. Experimental measurements, analytic models, and simulation results are used to understand the creation and characterization of these beams, with a focus on the mechanisms responsible for setting beam energy resolution. The information gained from these experimental and theoretical studies was then used to design, construct, and operate a next-generation high-energy-resolution beam system. In this new system, the pulsed beam from the BGT is magnetically guided into a new apparatus which re-traps the positrons, cools them to 50~K, and re-emits them as a pulsed beam with superior beam characteristics. Using these techniques, positron beams with total energy spreads as low as 6.9~meV FWHM are produced. This represents a factor of $\sim 5$ improvement over the previous state-of-the-art, making it the largest increase in positron beam energy resolution since the development of advanced moderator techniques in the early 1980's. These beams also have temporal spreads of $0.9~\mu$s FWHM and radial spreads of 1~mm FWHM. This represents improvements by factors of $\sim 2$ and $10$, respectively, over those of the previous beam resolutions. Future experimental applications of this new technology are also discussed.
Author :
Publisher :
ISBN 13 :
Total Pages : 27 pages
Book Rating : 4.:/5 (685 download)
Download or read book Intense Low Energy Positron Beams written by and published by . This book was released on 1993 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intense positron beams are under development or being considered at several laboratories. Already today a few accelerator based high intensity, low brightness e beams exist producing of the order of 108 - 109 e/sec. Several laboratories are aiming at high intensity, high brightness e+ beams with intensities greater than 109 e+/sec and current densities of the order of 1013 - 1014 e+ sec− 1cm−2. Intense e+ beams can be realized in two ways (or in a combination thereof) either through a development of more efficient B+ moderators or by increasing the available activity of B+ particles. In this review we shall mainly concentrate on the latter approach. In atomic physics the main trust for these developments is to be able to measure differential and high energy cross-sections in e+ collisions with atoms and molecules. Within solid state physics high intensity, high brightness e+ beams are in demand in areas such as the re-emission e+ microscope, two dimensional angular correlation of annihilation radiation, low energy e+ diffraction and other fields. Intense e+ beams are also important for the development of positronium beams, as well as exotic experiments such as Bose condensation and Ps liquid studies.
Author : Chor-Keung Cheung
Publisher :
ISBN 13 : 9781374666689
Total Pages : pages
Book Rating : 4.6/5 (666 download)
Download or read book The Construction of a Focused Low Energy Positron Beam Facility and Its Application in the Study of Various Optoelectronic Materials written by Chor-Keung Cheung and published by . This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Stephen M. Jiménez
Publisher :
ISBN 13 :
Total Pages : 230 pages
Book Rating : 4.:/5 (83 download)
Download or read book Design and Characterization of a Three-dimensional Positron Annihilation Spectroscopy System Using a Low-energy Positron Beam written by Stephen M. Jiménez and published by . This book was released on 2012 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 415 pages
Book Rating : 4.:/5 (683 download)
Download or read book Applications and Advances of Positron Beam Spectroscopy written by and published by . This book was released on 1997 with total page 415 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over 50 scientists from DOE-DP, DOE-ER, the national laboratories, academia and industry attended a workshop held on November 5-7, 1997 at Lawrence Livermore National Laboratory. Workshop participants were charged to address two questions: Is there a need for a national center for materials analysis using positron techniques and can the capabilities at Lawrence Livermore National Laboratory serve this need. To demonstrate the need for a national center, the workshop participants discussed the technical advantages enabled by high positron currents and advanced measurement techniques, the role that these techniques would play in materials analysis and the demand for the data. Livermore now leads the world in materials analysis capabilities by positrons due to developments in response to demands of stockpile stewardship. The Livermore facilities now include the world's highest current beam of keV positrons, a scanning pulsed positron microprobe under development capable of three dimensional maps of defect size and concentration, an MeV positron beam for defect analysis of large samples, and electron momentum spectroscopy by positrons. It was concluded that the positron microprobe under development at LLNL and other new instruments that would be relocated at LLNL at the high current keV source are an exciting step forward in providing results for the positron technique. These new data will impact a wide variety of applications.
Download or read book Low-energy-positron Production at the Livermore Linac written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Beams of monoenergetic positrons with energies of a few eV to many keV have been used in experiments in atomic physics, solid state physics and materials science. The results of some of these experiments are given and the production of positron beams from a new source, an electron linac, is described. Intense, pulsed beams of low-energy positrons have been produced by a high-energy beam from an electron linac. The production efficiency for low-energy positrons has been determined for electrons with energies from 60 to 120 MeV. Low-energy positron beams produced with a high energy electron a linac can be of much higher intensity than those beams currently derived from radioactive sources. These higher intensity beams will make possible positron experiments previously infeasible.
Author : Christoph Hugenschmidt
Publisher :
ISBN 13 :
Total Pages : 194 pages
Book Rating : 4.:/5 (725 download)
Download or read book Novel Applications Using the High Intensity Low-energy Positron Beam at NEPOMUC written by Christoph Hugenschmidt and published by . This book was released on 2010 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Description of the Intense, Low Energy, Monoenergetic Positron Beam at Brookhaven written by and published by . This book was released on 1985 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An intense (4 x 107 s−1), low energy (approx. =1.0 eV), monoenergetic (.delta. E approx. = 75 MeV) beam of positrons has been built at the Brookhaven National Laboratory. This flux is more than 10 times greater than any existing beam from radioactive sources. Plans are underway to increase further the flux by more than an order of magnitude. The intense low energy positron beam is made by utilizing the High Flux Beam Reactor at Brookhaven to produce the isotope 64Cu with an activity of 40 curies of positrons. Source moderation techniques are utilized to produce the low energy positron beam from the high energy positrons emitted from 64Cu. 31 refs., 7 figs.
Author :
Publisher :
ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (683 download)
Download or read book Studies of Slow-positron Production Using Low-energy Primary Electron Beams written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Slow-positron beams produced from negative-work-function solid-state moderators have found numerous applications in condensed matter physics. There are potential advantages in using low-energy primary electron beams for positron production, including reduced radiation damage to single-crystal moderators and reduced activation of nearby components. We present numerical calculations of positron yields and other beam parameters for various target-moderator configurations using the Argonne Wakefield Accelerator (AWA) [1] and Advanced Photon Source (APS) [2] electron linacs [3] as examples of sources for the primary electron beams. The status of experiments at these facilities is reviewed.
