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Construction And Testing Of A Positron Annihilation Lifetime Spectrometer
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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 Construction of a Positron-Lifetime Spectrometer and Its Application to Studying Electron Irradiation Induced Defects in 6h Silicon Carbide by : Tat-Wang Lam
Download or read book Construction of a Positron-Lifetime Spectrometer and Its Application to Studying Electron Irradiation Induced Defects in 6h Silicon Carbide written by Tat-Wang Lam 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, "Construction of a Positron-lifetime Spectrometer and Its Application to Studying Electron Irradiation Induced Defects in 6H Silicon Carbide" by Tat-wang, Lam, 林達宏, 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 CONSTRUCTION OF A POSITRON-LIFETIME SPECTROMETER AND ITS APPLICATION TO STUDYING ELECTRON IRRADIATION INDUCED DEFECTS IN 6H SILICON CARBIDE Submitted by LAM TAT WANG for the Degree of Master of Philosophy at The University of Hong Kong in August 2003 A positron-lifetime spectrometer was constructed to study defects in 6H silicon carbide (SiC) materials. Optimized resolution was obtained by calibrating the photomultiplier tube, the constant fraction discriminators and the multichannel analyzer. A single Gaussian function with 222.5ps FWHM was obtained for the resolution of the positron-lifetime system. Positron-lifetime measurements were then performed on the as-grown and the electron-irradiated n-type 6H SiC samples. Annealing studies were carried out to investigate the evolution of defects at annealing temperatures of 100, 200, 300, 400, o 500, 600, 700, 900, 1000 and 1080 C for the electron-irradiated sample and were extended to 1700 C for the non-irradiated sample. For the electron-irradiated sample, the lifetime value of the long-lifetime component was constant at about 228 ps throughout the whole annealing process. This defect is attributed to the V V C Si divacancy, since this lifetime value is very close to 232 ps, the characteristic lifetime of V V divacancy. The concentration of V V divacancy in the electron-irradiated C Si C Si sample was observed to be enhanced by the electron-irradiation process. This V V C Si divacany was also found in the non-irradiated sample. After annealing at 1700 C, the 9 -1 trapping rate and the concentration of the V V divacancy dropped from 110 s C Si 16 -3 8 -1 16 -3 and 8.310 cm to 1.87110 s and 1.5510 cm respectively. The significant drop in trapping rate indicates the disappearance of the V V divacancies after the C Si 1700 C annealing. DOI: 10.5353/th_b3154991 Subjects: Silicon carbide - Spectra Semiconductors - Defects Positron annihilation Spectrometer
Book Synopsis Design and Performance Analysis of an Ultra-fast Digital Positron Annihilation Lifetime Spectrometer at The Ohio State University by : James Patrick Ralston
Download or read book Design and Performance Analysis of an Ultra-fast Digital Positron Annihilation Lifetime Spectrometer at The Ohio State University written by James Patrick Ralston and published by . This book was released on 2013 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Positron Annihilation Lifetime Spectroscopy (PALS) is a highly effective technique to quantify the lattice deformation in solid materials. The technique is based on amount of time it takes a free neutron to annihilate in the sample material. Since the timescales of positron lifetime are on the order of a nanosecond, high precision timing measurements are required to obtain useful measurements. Recent innovations in digital data acquisition technology has allowed digital systems to approach and surpass the timing capabilities of their analog counterparts. Digital acquisition systems also have the advantage of a generally simpler setup that offers equal capabilities at a lower cost. The digital system can potentially offer double the counting rates, as each detector in the system can measure both starting and stopping events. The spectrometer designed allows for high performance timing measurements, equal and better than analog and more expensive digital systems. Custom software, developed in C++/C, has been written for the data analysis and data acquisition and allows for very high counting rates. The system hardware was assembled with an ORTEC 905-21 fast plastic scintillation detector and a CAEN N6751 2 GS/s digitizer, the timing performance of the specific hardware combination used has been previously undetermined. The timing performance analysis was conducted with using a Co-60 button sized radiation source to measure coincident gamma rays. Since the gamma rays are emitted from the source at almost the exact same moment, the measured time difference between detected events can be used to measure the uncertainty in the timing of the spectrometer. The timing resolution of the spectrometer is characterized by the Full Width at Half Maximum (FWHM) of the measured Co-60 spectra. The measured value of the FWHM of the spectrometer was 208.5 ± 1.1 ps.
Book Synopsis Construction of a Positron-lifetime Spectrometer and Its Application to Studying Electron Irradiation Induced Defects in 6H Silicon Carbide by : Tat-wang Lam
Download or read book Construction of a Positron-lifetime Spectrometer and Its Application to Studying Electron Irradiation Induced Defects in 6H Silicon Carbide written by Tat-wang Lam and published by . This book was released on 2003 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Design and Implementation of a Digital Positron Annihilation Lifetime Spectrometer for Measurements in Graphite by :
Download or read book Design and Implementation of a Digital Positron Annihilation Lifetime Spectrometer for Measurements in Graphite written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A digital Positron Annihilation Lifetime Spectrometer was designed and used to perform measurements on three graphite materials, reactor grade graphite, pyrolytic graphite, and a foam graphite developed by Oak Ridge National Laboratory. Positrons are a useful probe of the microstructural features of matter since they are attracted to open-volume pores and defects where the electron density is lower than in other parts of the material. Various types of graphite were studied because of their importance in nuclear technology, including as a moderator in nuclear reactor cores. A lifetime spectrometer consists of a scintillation detector, photomultiplier tube, and equipment to perform timing analysis on the detected radiation. This equipment can either consist of analog pulse shaping and timing electronics or a system that digitizes and processes the radiation pulses. A new type of scintillation material, Lanthanum Bromide [LaBr3(Ce)], was tested and compared to the scintillator usually used for lifetime experiments, Barium Fluoride. The Lanthanum Bromide was expected to perform somewhat better than BaF2 based on its scintillation properties, and this was confirmed. The digital system was tested and its performance optimized. The digital lifetime spectrometer shared some similar equipment with a standard analog spectrometer and as such, both could be used simultaneously to take measurements. The digital spectrometer showed improvement in its timing resolution over the analog system. The measurements on graphite were more conclusive for the digital system than for the analog system, as results from the former matched published data well and were more consistent in general. This was due to the greater flexibility in timing methods and opportunity for optimization afforded by the digital system. Measurements on the graphites supported other work in the literature showing a lifetime of approximately 200 ps in the reactor grade and pyrolytic graphites with a second lifetime o.
Book Synopsis Design and Implementation of a Digital Positron Annihilation Lifetime Spectrometer for Measurements in Graphite by : Ethan Wesley Bodnaruk
Download or read book Design and Implementation of a Digital Positron Annihilation Lifetime Spectrometer for Measurements in Graphite written by Ethan Wesley Bodnaruk and published by . This book was released on 2008 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: positron annihilation, coincidence timing, digital spectrometer.
Book Synopsis Construction of a Positron-lifetime Spectrometer and Its Application to Studying Electron Irradiation Induced Defects in 6H Siliconcarbide by :
Download or read book Construction of a Positron-lifetime Spectrometer and Its Application to Studying Electron Irradiation Induced Defects in 6H Siliconcarbide written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: (Uncorrected OCR) Abstract of thesis entitled CONSTRUCTION OF A POSITRON-LIFETIME SPECTROMETER AND ITS APPLICATION TO STUDYING ELECTRON IRRADIATION INDUCED DEFECTS IN 6H SILICON CARBIDE Submitted by LAM TAT WANG for the Degree of Master of Philosophy at The University of Hong Kong in August 2003 A positron-lifetime spectrometer was constructed to study defects in 6H silicon carbide (SiC) materials. Optimized resolution was obtained by calibrating the photomultiplier tube, the constant fraction discriminators and the multichannel analyzer. A single Gaussian function with 222.5ps FWHM was obtained for the resolution of the positron-lifetime system. Positron-lifetime measurements were then performed on the as-grown and the electron-irradiated n-type 6H SiC samples. Annealing studies were carried out to investigate the evolution of defects at annealing temperatures of 100, 200, 300, 400, 500, 600, 700, 900, 1000 and 1080 oC for the electron-irradiated sample and were extended to 1700 oC for the non-irradiated sample. For the electron-irradiated sample, the lifetime value of the long-lifetime component was constant at about 228 ps throughout the whole annealing process. This defect is attributed to the VCVSi divacancy, since this lifetime value is very close to 232 ps, the characteristic lifetime of VCVSi divacancy. The concentration of VCVSi divacancy in the electron-irradiated sample was observed to be enhanced by the electron-irradiation process. This VCVSi divacany was also found in the non-irradiated sample. After annealing at 1700 oC, the trapping rate and the concentration of the VCVSi divacancy dropped from 1|09 s-1 and 8.3|016 cm-3 to 1.871|08 s-1 and 1.55|016 cm-3 respectively. The significant drop in trapping rate indicates the disappearance of the VCVSi divacancies after the 1700 oC annealing.
Book Synopsis Positron Annihilation Studies of Solids and Surfaces by : Paul Richard Guagliardo
Download or read book Positron Annihilation Studies of Solids and Surfaces written by Paul Richard Guagliardo and published by . This book was released on 2011 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: [Truncated abstract] This thesis describes the first positron annihilation studies undertaken in the Atomic, Molecular and Surface Physics group in the School of Physics at the University of Western Australia (UWA). We have studied a range of systems with differing positron annihilation characteristics with the aim of characterising their defect properties, and in the process have gained insight into the interactions of positrons and positronium with materials. The project started with establishing a positron annihilation laboratory. This entailed developing procedures to produce and safely handle sealed 22Na sources, and testing positron annihilation instrumentation and experimental methods. The project evolved through collaboration with physicists, engineers, chemists, materials scientists, metallurgists and medical scientists and through a number of interesting experimental explorations of the physical phenomena affecting positron annihilation. An overview of these investigations and a thesis synopsis is given below. Chapter 1 is an introduction to positron annihilation techniques, concentrating on the interactions of positrons (and positronium) with materials, and on the spectroscopies that exploit the annihilation processes for the purpose of studying condensed matter systems. Chapter 2 describes the testing and optimisation of the positron annihilation lifetime spectrometer and Doppler broadening spectrometer. In Chapter 3, positron annihilation has been applied to study cation vacancies in oxides that exhibit ionic bonding. Such vacancies have a relative negative charge and so attract positrons, and the relatively low electron density at these sites causes enhanced positron lifetimes. Oxides considered in this work are (a) rutile, (Ti,Nb)O2, sintered in air and Ar; (b) tin oxide, (Sn,Nb)O2 sintered in air; (c) monoclinic zirconia, (Zr,Nb)O2; (d) pollucite, Cs(1-x)Al(1-x)Si(2+x)O6 and (e) Ta- and Ti-doped Zn2TiO4. All systems except (c) showed enhanced lifetimes when doping or off-stoichiometry was increased. In Chapter 4, positron annihilation has been used to study the nanoporosity of cementitious materials. The mechanical properties of these materials are heavily influenced by porosity, with the volume and size distribution of pores controlling both the strength and durability of the material...
Book Synopsis Development and Optimization of a Positron Annihilation Lifetime Spectrometer to Measure Nanoscale Defects in Solids and Borane Cage Molecules in Aqueous Nitrate Solutions by : Matthew A. Ross
Download or read book Development and Optimization of a Positron Annihilation Lifetime Spectrometer to Measure Nanoscale Defects in Solids and Borane Cage Molecules in Aqueous Nitrate Solutions written by Matthew A. Ross and published by . This book was released on 2008 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Positron Profilometry by : Jerzy Dryzek
Download or read book Positron Profilometry written by Jerzy Dryzek and published by Springer Nature. This book was released on 2023-09-08 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of positron profilometry, specifically focusing on the analysis of defect depth distribution in materials. Positron profilometry plays a crucial role in understanding and characterizing defects in a wide range of materials, including metals, semiconductors, polymers, and ceramics. By analyzing the depth distribution of defects, researchers can gain insights into various material properties, such as crystal structure, defect density, and diffusion behavior. The author's extensive research spanning a period of two decades has primarily centered on subsurface zones. These regions, located beneath the surface and subjected to various surface processes, play a crucial role in generating defect distributions. Three experimental techniques and their data analysis are described in detail: a variable-energy positron beam (VEP) called sometimes a slow positron beam, a technique called implantation profile depth scanning (DSIP), and a sequential etching (SET) technique. The usability of these techniques is illustrated by many examples of measurements by the author and others.
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 Spectroscopy with Magnetically Analyzed Beams by :
Download or read book Positron Annihilation Spectroscopy with Magnetically Analyzed Beams written by and published by . This book was released on 1982 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Physics with Many Positrons by : Alfredo Dupasquier
Download or read book Physics with Many Positrons written by Alfredo Dupasquier and published by IOS Press. This book was released on 2010 with total page 627 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the exception of positron emission tomography (PET), the field of low energy positron science produces relatively few academic articles each year compared to more accessible fields. Though much has been achieved since the publication of two related volumes earlier in this series: Positron Solid State Physics (1981) and Positron Spectroscopy of Solids (1993), only the first steps have been made towards 'physics with many positrons': physical situations where the interactions of positrons with positrons can be observed. This 2009 "Enrico Fermi School" aims to stimulate the field o.
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
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781723417894 Total Pages :24 pages Book Rating :4.4/5 (178 download)
Book Synopsis Positron Annihilation Spectroscopy with Magnetically Analyzed Beams by : National Aeronautics and Space Administration (NASA)
Download or read book Positron Annihilation Spectroscopy with Magnetically Analyzed Beams written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-20 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lifetime measurements with magnetically analyzed positron beams were made in condensed media with uniform and non-uniform properties. As expected, the lifetime values with magnetically analyzed positron beams in uniform targets are similar to those obtained with conventional positron sources. The lifetime values with magnetically analyzed beams in targets which have non-uniform properties vary with positron energy and are different from the conventional positron source derived lifetime values in these targets. Singh, J. J. and Holt, W. H. and Mock, W., Jr. Langley Research Center NASA-TM-84535, NAS 1.15:84535 RTOP 505-33-23-05
Book Synopsis On Resolution and Intensity in Positron Lifetime Spectroscopy by : Matti Karras
Download or read book On Resolution and Intensity in Positron Lifetime Spectroscopy written by Matti Karras and published by . This book was released on 1978 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
