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The Construction Of A Focused Low Energy Positron Beam Facility And Its Application In The Study Of Various Optoelectronic Materials
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Book Synopsis The Construction of a Focused Low Energy Positron Beam Facility and Its Application in the Study of Various Optoelectronic Materials by : Chor-Keung Cheung
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:
Book Synopsis The Construction of a Focused Low Energy Positron Beam Facility and Its Application in the Study of Various Optoelectronic Materials by : Chor-keung Cheung
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 2006 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positron Beams And Their Applications by : Paul G Coleman
Download or read book Positron Beams And Their Applications written by Paul G Coleman and published by World Scientific. This book was released on 2000-01-22 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.
Book Synopsis The Focusing of the Hku Positron Beam, and an Extended Design for Incorporating Secondary Electron-Positron Annihilation Lifetime Spectroscopy by : Pui-Ying Rebecca Kwan
Download or read book The Focusing of the Hku Positron Beam, and an Extended Design for Incorporating Secondary Electron-Positron Annihilation Lifetime Spectroscopy written by Pui-Ying Rebecca Kwan 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, "The Focusing of the HKU Positron Beam, and an Extended Design for Incorporating Secondary Electron-positron Annihilation Lifetime Spectroscopy" by Pui-ying, Rebecca, Kwan, 關珮瑩, 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 THE FOCUSING OF THE HKU POSITRON BEAM, AND AN EXTENDED DESIGN FOR INCORPORATING SECONDARY ELECTRON-POSITRON ANNIHILATION LIFETIME SPECTROSCOPY submitted by Kwan Pui Ying, Rebecca for the degree of Doctor of Philosophy at The University of Hong Kong in February 2006 Variable Energy Positron Annihilation Lifetime Spectroscopy (VE-PALS) is a powerful diagnostic tool for studying defects in thin films and at interface. By varying the energy of the monoenergetic positron beam, positrons can be implanted to varying depths so that a depth profile of void size and concentration can be obtained. It has been proposed to add a VE-PALS system to the present positron (e ) beam facility at The University of Hong Kong so as to increase its usefulness. The present work describes in detail design work on a possible VE-PALS apparatus that can achieve excellent time resolutions 250 psec using secondary electron emission from a thin carbon foil. The difficulty in constructing a VE-PALS system lies in the fact that a "start" signal is required to signal the entry of the positron into the target. Two methods have been used in the past to overcome this problem, the first being a bunching technique which employs RF cavities and choppers, the second being the use of secondary electrons emitted from the target. The latter technique is in terms of experimental complexity much simpler, but has in the past suffered from poor time resolution (typically 500 psec). The present study demonstrates an important finding, namely that successful secondary electron based VE-PALS requires the use of a positron beam with small diameter ( 1 mm). Simulations of the HKU positron beam have been carried out using the SIMION software. These simulations led to the discovery of a hybrid lens system that has made it possible to achieve 1 mm beam sizes using conventional magnetic guidance. The hybrid lens design allows positrons to begin their trajectories from a 8 mm primary moderator in a magnetic field-free region after which they are focused into a solenoidal magnetic field that transports the positrons to the target. The results of the successful focusing operation of the positron beam based on the simulated design are given. The present work includes a series of detailed computer simulations of different possible VE-PALS designs. Designs used at Brookhaven National Laboratory and Oak-Ridge National Laboratory that have met with partial success in the past have been studied. Modified designs based on these systems have been suggested and studied using the SIMION software. A design based on a localized non-adiabatic lateral magnetic field that allows high detection efficiency coupled with good timing capability has been studied, but has been ruled out on the basis of operational complexity. An alternative design based on a modification of the Oak-Ridge National Laboratory design, although having slightly inferior timing capability has been chosen as a more optimal design. Design details are presented. DOI: 10.5353/th_b3683719 Subjects: Electron spectroscopy Positron annihilation Positron beams
Book Synopsis A Variable Energy Positron Beam Facility with Applications in Materials Science by : Hendrik Schut
Download or read book A Variable Energy Positron Beam Facility with Applications in Materials Science written by Hendrik Schut and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Slow Positron Beam Techniques for Solids and Surfaces by : Eric Ottewitte
Download or read book Slow Positron Beam Techniques for Solids and Surfaces written by Eric Ottewitte and published by American Institute of Physics. This book was released on 1994 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text examines the application of positron beams to studies of solids and surfaces with profiles for an increasing array of materials. It presents the progress made in areas of defect profiling, including improvements in theoretical modelling.
Book Synopsis A New Ultra-cold Positron Beam and Applications to Low-energy Positron Scattering and Electron-positron Plasmas by : Steven Jay Gilbert
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:
Book Synopsis Intense Positron Beams and Possible Experiments by :
Download or read book Intense Positron Beams and Possible Experiments written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, we survey some of the ideas that have been proposed regarding the production of intense beams of low energy positrons. Various facilities to produce beams of this type are already under design or construction and other methods beyond those in use have been previously discussed. Moreover, a variety of potential experiments utilizing intense positron beams have been suggested. It is to be hoped that this paper can serve as a useful summary of some of the current ideas, as well as a stimulation for new ideas to be forthcoming at the workshop. 31 references.
Book Synopsis Development of Low Energy Positron Beams and Their Application to the Study of the Surface Region in Metals by :
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:
Book Synopsis Low-energy-positron Production at the Livermore Linac by :
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.
Book Synopsis Studies of Slow-positron Production Using Low-energy Primary Electron Beams by :
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.
Book Synopsis Electrostatic Positron Beam for Materials Characterisation by : Elena Abadjieva
Download or read book Electrostatic Positron Beam for Materials Characterisation written by Elena Abadjieva and published by Delft University Press. This book was released on 2003-01-01 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This dissertation describes the design and performance of an electrostatic variable energy positron beam. It is developed to perform Doppler-broadening measurements in the low mm range, positron lifetime measurements and transmission re-moderation experiments. The instrument has been built at Positron Centre Delft. Contents include: Principles of positron annihilation techniques, Positron beam optics, A facility for positron re-moderation experiments, Re-moderation experiments, Design options for a positron beam lifetime spectrometer, A facility for Doppler-broadening measurements in the low-mm range, Doppler-broadening measurements."
Book Synopsis Positron Beam Study of Carbon Foil and Titanium Dioxide Nanotubes, and Proposing a Design of a Lifetime Positron Beam Based on Secondary Electrons Emission from Carbon Foil by : Bin Yang
Download or read book Positron Beam Study of Carbon Foil and Titanium Dioxide Nanotubes, and Proposing a Design of a Lifetime Positron Beam Based on Secondary Electrons Emission from Carbon Foil written by Bin Yang and published by . This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Positron Beam Study of Carbon Foil and Titanium Dioxide Nanotubes, and Proposing a Design of a Lifetime Positron Beam Based on Secondary Electrons Emission From Carbon Foil" by Bin, Yang, 杨彬, 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: Secondary electron (SE) emission from thin carbon foils induced by 1-20 keV positrons has been investigated over a range of nominal foil thicknesses from 1.0 to 5.0 μg/cm2. The measurement of SEs was carried out in forward geometry using a microchannel plate as a detector. The SE yield γ has been measured as a function of beam energy and compared with some Monte Carlo simulation results. We also present in this thesis the material parameter Λ=? / (dE / dx) and the emitted SE energy spectra. Forincident positron energy of 5 keV or higher, the distribution is found to be characterizedby the Sickafus form, AEm and m is close to 1. For low energy incident positrons however, another form, Bexp(E / t), is proposed for describing the SE distribution. The maximum scattering angle for SEs emitted from 5.0 μg/cm2 is found to be around 60. Measurements of energy loss and energy loss straggling for 1-10 keV positrons passing through thin carbon foils of different thicknesses ranging from 1.0 to 5.0 μg/cm2 are present in this thesis. The stopping power dE / dx and positron transmission coefficient have also been investigated as a function of incident positron energy and foil thickness. Particularly, our experimental results are compared with those from Monte Carlo simulation and theory with a view to providing a way to determine the real thickness of carbon foil. The ratio of the energy loss straggling to the foil thickness seems to have a linear relation with the beam energy. The transmitted positrons after passing through 5.0 μg/cm2 C-foil have a small scattering angle which is less than 10. Titanium dioxide nanotube arrays fabricated by anodization of titanium foil and annealed at different temperatures were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and positron annihilation spectroscopy (PAS). The crystallization process and morphological change of the nanotubes have been discussed. It is found that anatase (101) only appeared on the walls of the nanotube. The atomic concentration of fluoride and the ratio of Ti/O decreased when the annealing temperature increased. Vacancy type defects were found to diffuse toward the surface when the samples were annealed at 200C and 400C and healing of vacancies occurred at 600C. In addition, the fluoride may form some complexes with vacancies on the surface hence lowering the value of the S parameter. A new design of the lifetime positron beam based on the SE emission is proposed. The observed experimental results and simulation results make it possible to construct a new type of high resolution (DOI: 10.5353/th_b4716028 Subjects: Nanotubes Positron beams Secondary electron emission
Book Synopsis Description of the Intense, Low Energy, Monoenergetic Positron Beam at Brookhaven by :
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.
Book Synopsis 1987 Workshop on Intense Positron Beams by : E. H. Ottewitte
Download or read book 1987 Workshop on Intense Positron Beams written by E. H. Ottewitte and published by World Scientific Publishing Company. This book was released on 1988 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Briefs written by and published by . This book was released on 1991 with total page 1120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
