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A New Beamline For Positron Annihilation Lifetime Spectroscopy
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Book Synopsis A New Beamline for Positron Annihilation Lifetime Spectroscopy by : Ryan Winslow Weed
Download or read book A New Beamline for Positron Annihilation Lifetime Spectroscopy written by Ryan Winslow Weed and published by . This book was released on 2011 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: The major aspect of this research is the development of a variable-energy PALS beamline based on a Surko-type buffer gas positron trap, the first of its kind in the world. A significant amount of work has gone into optimization of the timing and intensity characteristics of positron pulse. Successful implantation of 'Mills ideal function' bunching method has led to positron pulses of 800ps, allowing depth selective studies across a range of defect sizes, from point defects with lifetimes as low as 200ps, to large voids (~10 nm) resulting in lifetimes >50 ns. In addition to experimental development aspects, the materials investigations presented here focus on defects in semiconductor materials produced by ion implantation and focused laser pulses.
Book Synopsis Positron Annihilation Lifetime Studies of Inorganic Materials Using a New Positron Beamline by : Jason Roberts
Download or read book Positron Annihilation Lifetime Studies of Inorganic Materials Using a New Positron Beamline written by Jason Roberts and published by . This book was released on 2012 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, effects caused by the nanoscale structure of a material have become increasingly important for technological progress. With improvements in fabrication techniques, nanoscale structures can now be produced with growing control. As a result, techniques to characterise these properties have been developed and are also becoming increasingly important. One such collection of non-destructive techniques, which can provide unique information about a target sample, is Positron Annihilation Spectroscopy (PAS). The initial aim of the research presented here was the development and characterisation of a positron beamline for materials studies. This beamline, now operational, has been developed to measure the positron lifetime in a target material. This technique, referred to as Positron Annihilation Lifetime Spectroscopy (PALS), allows the size of open volume type defects (or voids) up to 10 nm to be determined. In addition, as the technique is implemented using a variable energy positron beam, thin film samples can be characterised and measurements can be performed in a depth sensitive manner. The beamline uses a Surko trap to isolate and cool positrons from a moderated radioactive source. Positrons are released from the trap using a timed potential ramp, though hardware restrictions limit the effectiveness of this technique. This arrangement results in a pulsed positron beam of up to two thousand pulses per second with a temporal Full Width at Half Maximum (FWHM) of 800 ps. Typical spectra, which contain 1 000 000 counts, can be recorded in two hours; although to resolve shorter lifetime components (
Book Synopsis The Focusing of the HKU Positron Beam, and an Extended Design for Incorporating Secondary Electron-positron Annihilation Lifetime Spectroscopy by :
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 and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Focusing of the Hong Kong University Positron Beam, and an Extended Design for Incorporating Secondary Electron-positron Annihilation Lifetime Spectroscopy by : Pui-ying Kwan (Rebecca)
Download or read book Focusing of the Hong Kong University Positron Beam, and an Extended Design for Incorporating Secondary Electron-positron Annihilation Lifetime Spectroscopy written by Pui-ying Kwan (Rebecca) and published by . This book was released on 2006 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positron Beam Lifetime Spectroscopy at Lawrence Livermore National Laboratory by :
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.
Book Synopsis Book of Abstracts from the International Workshop on Positron Studies of Defects 2024 (PSD-24) by : Rafael Ferragut
Download or read book Book of Abstracts from the International Workshop on Positron Studies of Defects 2024 (PSD-24) written by Rafael Ferragut and published by Trans Tech Publications Ltd. This book was released on 2024-08-23 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: Following the long tradition that started in 1987, the International Workshop on Positron Studies of Defects 2024 (PSD-24) will be held in Como, Italy, in the period from September the 1st to 6th, 2024. The aim of the workshop is to provide an opportunity for exchange of the latest results and scientific information concerning the positron interactions with solids and surfaces, the generation of slow positron beams and their applications.
Book Synopsis Construction and Testing of a Positron Annihilation Lifetime Spectrometer by : Brian M. Wieland
Download or read book Construction and Testing of a Positron Annihilation Lifetime Spectrometer written by Brian M. Wieland and published by . This book was released on 2012 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Positron Annihilation Lifetime Spectroscopy (PALS) is a nuclear technique that was developed in the 1970s as a method to assess defects in materials. This technique has tremendous potential as a powerful tool for non-destructive quantification of the types and densities of defects within solids. Following the injection of positrons into a solid material, the positrons pair-annihilate at a rate dependent upon the density of electrons near the injection site. If there are lattice vacancies or dislocation defects near the injection site, the positrons are attracted to these areas, which have lower electron densities and thus give rise to longer positron lifetimes. Typical positron lifetimes in defect-free conductor-type metals are -'-'1OO ps, while lifetimes within defect regions are 2OO ps. In order to discern between these minute lifetime differences, a spectrometer with very good timing resolution has been constructed and optimized. The capabilities of the spectrometer have been tested using a 22Na positron emitter by performing source-based measurements of positron lifetimes in high-purity samples of aluminum, nickel, copper, and lead. Test results are in excellent agreement with currently accepted literature values, thus validating the apparatus and data analysis technique. This study is an important first step towards the development of a modern positron annihilation lifetime spectrometer for use in accelerator-based, gamma-induced positron annihilation spectroscopy (AG-PAS).
Book Synopsis A Novel Design of a Variable Energy Positron Lifetime Beam by : Dan Chen
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
Book Synopsis Positron Annihilation Lifetime Spectroscopy Methodology and Application to Perovskite Oxide Metals by : Gurmeet S. Kanda
Download or read book Positron Annihilation Lifetime Spectroscopy Methodology and Application to Perovskite Oxide Metals written by Gurmeet S. Kanda and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positron Annihilation Lifetime Spectroscopy Methodology and Application to Perovskite Oxide Materials by : Gurmeet Kanda
Download or read book Positron Annihilation Lifetime Spectroscopy Methodology and Application to Perovskite Oxide Materials written by Gurmeet Kanda and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positron Annihilation Lifetime Spectroscopy Study of Kapton Thin Foils by :
Download or read book Positron Annihilation Lifetime Spectroscopy Study of Kapton Thin Foils written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positron Annihilation Lifetime Spectroscopy by : Yang Yu
Download or read book Positron Annihilation Lifetime Spectroscopy written by Yang Yu and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Positron annihilation lifetime spectroscopy (PALS); Free volume; Polymers; Amorphous; Crystalline; Semicrystalline; Ionic liquids
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 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 New Directions in Antimatter Chemistry and Physics by : Clifford M. Surko
Download or read book New Directions in Antimatter Chemistry and Physics written by Clifford M. Surko and published by Springer Science & Business Media. This book was released on 2007-05-08 with total page 509 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is the outgrowth of a workshop held in October, 2000 at the Institute for Theoretical Atomic and Molecular Physics at the Harvard- Smithsonian Center for Astrophysics in Cambridge, MA. The aim of this book (similar in theme to the workshop) is to present an overview of new directions in antimatter physics and chemistry research. The emphasis is on positron and positronium interactions both with themselves and with ordinary matter. The timeliness of this subject comes from several considerations. New concepts for intense positron sources and the development of positron accumulators and trap-based positron beams provide qualitatively new experimental capabilities. On the theoretical side, the ability to model complex systems and complex processes has increased dramatically in recent years, due in part to progress in computational physics. There are presently an intriguing variety of phenomena that await theoretical explanation. It is virtually assured that the new experimental capabilities in this area will lead to a rapid expansion of this list. This book is organized into four sections: The first section discusses potential new experimental capabilities and the uses and the progress that might be made with them. The second section discusses topics involving antihydrogen and many-body phenomena, including Bose condensation of positronium atoms and positron interactions with materials. The final two sections treat a range of topics involving positron and positronium interactions with atoms and molecules.
Book Synopsis Positron Annihilation Lifetime Spectroscopy of Mechanically Milled Protein Fibre Powders and Their Free Volume Aspects by :
Download or read book Positron Annihilation Lifetime Spectroscopy of Mechanically Milled Protein Fibre Powders and Their Free Volume Aspects written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positron Annihilation ICPA-11 by : Y. C. Jean
Download or read book Positron Annihilation ICPA-11 written by Y. C. Jean and published by . This book was released on 1997 with total page 876 pages. Available in PDF, EPUB and Kindle. Book excerpt: For one and a half decades, the application of positron annihilation to condensed-matter physics concentrated on the study of the Fermi surfaces of metals and alloys. As other, often more powerful, techniques for performing this type of study were developed, it appeared that condensed-matter positron physics was going to be relegated to being a niche interest. However, the situation changed dramatically when it was found that measurements of positron annihilation in metals were sensitive to the structures of well-known defects. This discovery, and subsequent research made it a major tool in materials science.
Book Synopsis NEW DEVELOPMENTS IN POSITRON ANNIHILATION SPECTROSCOPY TECHNIQUES by : Petr Stepanov
Download or read book NEW DEVELOPMENTS IN POSITRON ANNIHILATION SPECTROSCOPY TECHNIQUES written by Petr Stepanov and published by . This book was released on 2020 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
