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1
Carpenter, Matthew Hollis. "Superconducting X-ray Spectrometers for High-Resolution Synchrotron XAS." Thesis, University of California, Davis, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3706565.
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X-ray absorption spectroscopy (XAS) is a powerful technique to determine the structure and function of molecules. It provides element-specific information on geometry, chemical bonding, oxidation state, and spin state, and its applications range from biology to material science. For dilute samples, XAS is measured by partial fluorescence yield (PFY), where the intensity of a weak fluorescence line is recorded as a measure of absorption as the energy of the incident x-ray beam is scanned across an absorption edge of the element of interest. PFY increases the sensitivity for XAS if an x-ray detector is used that can efficiently separate the small fluorescence signal of interest from the x-ray background due to other elements in the sample.
This dissertation describes the development of a high-resolution x-ray detector based on arrays of superconducting tunnel junctions (STJs). It is cooled to its operating temperature below 0.3 K with a liquid-cryogen-free adiabatic demagnetization refrigerator cryostat, and offers more than an order of magnitude improvement in energy resolution over conventional Ge- or Si-based solid state detectors. For operation in XAS experiments at a synchrotron, the STJ detector array is held at the end of a cold finger that can be inserted into an ultra-high vacuum endstation. This dissertation describes the design and performance of the STJ x-ray spectrometer, and demonstrates its use in PFY-XAS experiments in metallo-organic compounds at the Advanced Light Source synchrotron.
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Varney, Andrew John. "Development of x-ray spectrometers and x-ray spectroscopy for the Oxford electron beam ion trap." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282196.
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Song, Jungki. "Metrology and mechanics for manufacturing space-based x-ray grating spectrometers." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130846.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, February, 2021Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 223-231).
Small errors in critical dimensions (CDs) or deformation of optical components can lead to severe performance degradation in high-resolution imaging and spectroscopy tools. Consistent innovations towards more precise optical elements and assembly procedures have led to high-resolution optical systems in many fields - including telescope, microscopy, lithography, and display technologies. A space x-ray telescope needs more stringent requirements as it observes distant space objects using a limited number of x-ray photons in a harsh space environment. The optical instruments for x-ray telescopes need to be high-resolution, efficient in collecting x-ray photons, and lightweight. Optical elements in x-ray telescopes have large-apertures (typically around 1-2 m²) which are realized by populating them with > 1000 high-quality optical sub-elements (i.e., mirrors or gratings).
In this thesis, we limit our attention to an xray grating spectrometer, one of the essential elements in x-ray telescopes. It is placed downstream of the focusing optics and prior to the x-ray detector to disperse nonmonochromatic x rays from distant sources for space-based x-ray spectroscopy. A critical-angle transmission (CAT) grating, a lightweight, freestanding, high-aspect ratio x-ray grating with 200-nm period and 4 [mu]m depth, is a building block for grating spectrometers. More than 1000 high-quality CAT gratings need to be manufactured and precisely aligned within tolerance to build future CAT grating spectrometers. This thesis attacks this manufacturing challenge through 1) inventing metrologies for characterizing CDs, 2) developing alignment processes, and 3) performing design and analysis of CAT grating structural supports. First, a metrology to characterize period variation of CAT gratings was developed.
Metrology repeatability of 0.004 nm rms was achieved, successfully characterizing period variations of 0.018 nm rms (1 sigma) over large-area CAT gratings patterned with traditional interference lithography. The demonstrated metrology uncertainty and period variations fulfill the requirements for future x-ray telescope missions. Second, alignment metrology and protocols were developed, demonstrating an ability to align multiple CAT gratings to satisfy alignment requirements ( <6 arcmin or 0.1 deg). The developed alignment protocol is reliable and scalable for flight-level alignment, for which a large volume (>1000) of CAT gratings need to be aligned in a fast and accurate manner. Third, a metrology to characterize grating bar tilt variations was developed using small-angle x-ray scattering and a laser setup. The developed metrology demonstrated repeatability of <0.01 deg (1 [sigma]) and accuracy of ~0.08 deg (4.8 arcmin).
It successfully characterized bar tilt angle variations from CAT gratings and results agree well with synchrotron measurements. It enabled us to close the loop in process optimization for CAT grating fabrication, and contributed towards suppressing bar tilt (or blaze) error within tolerance ( <6 arcmin or 0.1 deg). Fourth, analytical and finite element studies were performed to design CAT grating structural supports that minimize x-ray blockage at a given stiffness. In-plane and out-of-plane stiffness of several 2D-lattice topologies were examined. A triangular lattice shows 23-580% on stiffness improvement ( depending on mode of stiffness) over the current hexagonal lattice design for the same open area fraction. Adopting the new 2D lattice design is expected to increase open area fraction by ~5% without compromising stiffness.
by Jungki Song.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
4
Hall, David. "Exploring the impact of detection physics in X-ray CCD imagers and spectrometers." Thesis, Open University, 2010. http://oro.open.ac.uk/55088/.
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This thesis is concerned with exploring the way in which the physics of the detection process affects the quality of a CCD-based X-ray detector system. The physical processes which lead to the final images and spectra achieved with a CCD-based camera system are investigated through a combination of simulations and experimental techniques with the aim of improving the detector performance and allowing future detectors to be designed with optimal characteristics. Techniques developed throughout the study and the results of the simulations have wide-ranging impacts on the areas concerned. The study is split into two main sections, the first regarding a high-resolution, high-energy, photon-counting X/γ-ray camera. In medical imaging, X-rays and gamma-rays are often used for the purposes of diagnostic imaging. In many synchrotron based research programmes, such as protein crystallography and X-ray diffraction imaging, X-rays are used, once again, for imaging purposes. In both cases, a high-resolution detector with a high frame-rate is required such that images can be taken with a spatial resolution of the order of micrometers to tens of micrometers. If one is able to distinguish the energy of the incident X-rays and gamma-rays (with energies of 20-200 keV) then these spectral capabilities add to the functionality of the detector, allowing, for example, the removal of fluorescence X-rays. Chapter 2 reviews the relevant detector physics and theory before providing a critical review of current gammacameras. Chapter 3 outlines the feasibility study for the scintillator-coupled EM-CCD detailing the development of a new energy discrimination methodology. Also described is the development of a full system simulation which can be used to troubleshoot problems found when calibrating and optimising the device. Chapter 4 details the characterisation and optimisation of the detector making use of the aforementioned simulations where appropriate. Chapter 5 presents the results of the study, showing how the resolution can be dramatically improved and how energy discrimination can be implemented. The second section of the thesis regards instrument background. The use of CCDs for space borne X-ray detection in scientific satellites is wide-spread. Whilst in-orbit the CCDs are subjected to an incident flux of high energy particles. These particles may be detected, both as the primaries themselves and by means of secondaries produced in the detector shielding, and will produce a background level formed by components indistinguishable from the X-rays for which the mission was designed to detect. Chapter 6 presents an introduction to the theory behind the instrument background experienced by CCD-based detector systems in orbit. A simulation has been developed which is in very good agreement with data received from the spacecrafts, described in Chapter 7. Finally, Chapter 8 summarises the outcomes of these studies and provides insight into future work which will further aid the improvement of gamma-cameras for medical imaging and synchrotron-based research and will allow future CCD-based camera systems to be designed for increased sensitivity in-orbit.
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Tarbutt, Michael Roy. "Spectroscopy of few-electron highly charged ions." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365339.
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RABELO, NETO JOSE da S. "Hidroxiapatita sintetica nanoestruturada e esmalte dental aquecidos e irradiados por laser de Er, Cr:YSGG. Caracterizacao por FTIR e por DRX." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9402.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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FERREIRA, JUNIOR OSCAR L. "Processos de separação de materiais metálicos e não metálicos na reciclagem de resíduos de placas de circuito impresso de microcomputadores." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10543.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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TEIXEIRA, BRUNA S. "Características de amidos processados pela radiação ionizante." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26795.
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O amido é um polissacarídeo produzido pelos vegetais para reserva de energia e está disponível em abundância na natureza. Os amidos são preparados a partir de diferentes matérias primas, tais como trigo, cevada, milho, arroz, batata, batata doce ou mandioca. Na dieta humana o amido é utilizado como fonte de energia biológica. Na indústria de alimentos, o amido é utilizado para alterar ou controlar diversas características, como textura, aparência, umidade, consistência e estabilidade. Entretanto, há uma contínua procura por novas tecnologias para o desenvolvimento de novas propriedades funcionais para melhor adequação às necessidades do mercado. A radiação ionizante pode ser aplicada na modificação de macromoléculas como a do amido. O presente trabalho teve como objetivo estudar as características de amidos de batata, milho e mandioca (polvilho azedo) tratados com radiação ionizante e os correspondentes filmes comestíveis preparados com eles. Os amidos em pó foram submetidos à radiação em fonte de 60Co Gammacell 220 com doses de 0, 1, 5, 10 e 15 kGy, taxa de dose em torno de 1 kGy h-1. Para o estudo dos amidos foram empregadas técnicas de microscopia, análises térmicas, espectroscopia no infravermelho, difração de raios-X e viscosimetria. Para os filmes foram avaliadas propriedades mecânicas, análise instrumental da cor, capacidade de absorção e índice de solubilidade. Constatou-se que a radiação não influenciou a morfologia dos grânulos, a termogravimetria e o padrão de difração de raios-X. A viscosidade dos hidrogéis dos amidos diminuiu com o aumento da dose de radiação e estes apresentaram características de fluidos não-Newtonianos e pseudoplásticos. Na avaliação instrumental da cor dos filmes houve um ligeiro aumento no parâmetro b*(cor amarela). A força de ruptura dos filmes decresceu conforme aumento da dose de radiação aplicada dependendo do tipo de amido empregado na sua fabricação. A capacidade de absorção em água diminuiu e a solubilidade aumentou com a radiação.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
9
PEREIRA, VIVIANE S. "Preparação de suportes de carbono dopados com Nitrogênio (N), Enxofre (S) e Fósforo (P) para aplicação na oxidação eletroquímica do metanol." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26828.
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Neste trabalho o carbono comercial Vulcan XC72 foi modificado com heteroátomos de N, S e P por meio do tratamento térmico a 800 °C com ureia, ácido sulfúrico e ácido fosfórico, respectivamente. Os carbonos modificados foram utilizados na preparação de eletrocatalisadores Pt/C e PtRu/C e aplicados na oxidação eletroquímica do metanol. Os materiais obtidos foram caracterizados por espectroscopia dispersiva de raios X, difração de raios X, espectroscopia Raman, microscopia eletrônica de transmissão e voltametria cíclica. A oxidação eletroquímica do metanol foi estudada por voltametria cíclica e cronoamperometria. Os espectros Raman mostraram que as razões de intensidades das bandas D e G dos suportes de carbono modificados com heteroátomos foram maiores que a observada para o carbono Vulcan XC72 sugerindo a incorporação na estrutura do carbono. As análises por difração de raios X mostraram para todos os eletrocatalisadores Pt/C a estrutura cúbica de face centrada (cfc) e as micrografias eletrônicas de transmissão que todos materiais apresentaram tamanhos de partícula na faixa 4-5 nm. Para os eletrocatalisadores PtRu/C preparados com os suportes de carbono modificados com N e S, os difratogramas de raios-X apresentaram apenas a fase Pt (cfc) não havendo deslocamento dos picos desta fase. Nestes materiais os picos referentes a fases de Ru não foram identificados sugerindo que o Ru apresenta-se como uma fase amorfa. Por outro lado, para o material modificado com P, observou-se um deslocamento dos picos da fase Pt(cfc) para ângulos maiores, sugerindo a formação de liga Pt-Ru e também foi observado a presença da fase Ru hexagonal compacta. Os eletrocatalisadores Pt/C e PtRu/C preparados com os suportes contendo heteroátomos apresentaram uma melhora significativa na atividade eletrocatalítica quando comparados aos materiais preparados com o suporte não modificado. A melhora na atividade pode estar relacionada a modificações na interação metal-suporte, bem como, as diferentes espécies Pt e Ru presentes no caso do eletrocatalisador PtRu/C preparado utilizando o suporte modificado com P.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
10
SANTORO, THAIS A. de B. "Preparacao e caracterizacao de eletrocatalisadores Pt-terras raras/C para celulas a combustivel do tipo PEMFC." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9411.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
11
FERREIRA, MAIARA S. "Imobilização da quitosana da carapaça de siri Charybdis hellerii em filmes poliméricos a partir de sua obtenção com o uso da radiação ionizante." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27125.
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A quitosana é um polisacarídeo obtido pela desacetilação das moléculas de quitina, principal constituinte de alguns fungos e do exoesqueleto de crustáceos e insetos. Os grupos amino presentes na quitosana conferem-lhe importantes propriedades biológicas, como a biodegradação, biocompatibilidade, atividade/efeitos imunológicos e atividade antibacteriana. A desacetilação da quitina é um processo cuja conversão é agressiva, já que exige o ataque da quitina em solução de álcalis em alta concentração e à quente, com duração de 6 a 8 horas. Neste trabalho, carapaças de siri da espécie Charybdis hellerii foi fragmentada e pré-tratada para a obtenção da quitosana e cada etapa, desde o pré-tratamento do material in natura à sua conversão em quitosana, foi investigada detalhadamente. Observou-se que dose e taxa de dose não influenciaram no pré-tratamento ou na etapa de desacetilação da quitina; na dose de 20 kGy (gama ou feixe de elétrons), o processo de conversão teve duração de 60 minutos. A quitosana obtida teve baixa massa molar e grau de desacetilação comparável á quitosana padrão (SA), dependendo das condições de irradiação. Além disso, apresentou inibição da atividade bacteriana tanto livre como imobilizada em substratos poliméricos de polipropileno e de polietileno processados também por radiação ionizante.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
12
ROMANO, REBECA da S. G. "Estudo da irradiação do polipropileno para possibilitar o controle de sua degradação ambiental." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28012.
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O PP é descartado em grande quantidade no meio ambiente, tendo em vista seu consumo muito elevado derivado de suas excelentes propriedades químicas e físicas, boa processabilidade e baixo custo. As radiações ionizantes, não ionizantes (UV e infravermelho), bem como o oxigênio e os poluentes podem causar a degradação do polipropileno (PP). A exposição à radiação ionizante pode causar na molécula de PP cisão de cadeia principal, reticulação e peroxidação (na presença de ar) entre outras. Este estudo tem como objetivo, o desenvolvimento de um PP oxidegradável por meio do controle da degradação induzida por radiação ionizante. As amostras foram processadas por injeção e expostas ao envelhecimento natural durante 180 dias e ao envelhecimento acelerado em estufa á 100°C por 192 dias e depois caracterizadas por avaliação visual, ensaios mecânicos, FTIR, SEM, DSC, TGA e DRX. As amostras de PP Grão 20 kGy, após o envelhecimento natural, apresentaram maior oxidação com presença de fissuras superficiais mais intensamente do que o PP d2w®. A resistência a tração do PP irradiado foi superior ao PP d2w® e os resultados do alongamento na ruptura mostraram uma diminuição intensa se compararmos o PP irradiado e o PP d2w® com o PP. Após a exposição natural espécies os índices de vinila e carbonila aumentaram ligeiramente devido as reações Norrish. O grupo carbonila promove uma oxidação contínua, junto à superfície fazendo com que o polímero diminua sua massa molar. O efeito da degradação natural foi evidente na ordem PP Grão 20 kGy > PP Grão 12,5 kGy = PP d2w® > PP. Por conseguinte, este conceito pode ser utilizado para produzir um PP com propriedades oxi-degradáveis de uma forma controlável.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
13
An, Siwen. "X-ray Fluorescence Spectrometry for Environmental Applications." Licentiate thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-39979.
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Heavy metal contamination in environmental applications is particularly important because of its potential impact on associated ecosystems and human health. At present, monitoring of heavy metals is usually done by taking and preparing samples for off-line laboratory measurements. X-ray fluorescence (XRF) analysis is a powerful and widely used tool for determining the elemental composition and concentration of chemical species in materials. This project is a feasibility study for the possibility of on-line XRF systems for continuousand direct analysis of industrial processes and environmental emissions. The feasibility of such measurements depends on the accuracy with which the concentration can be measured within a given response time. Therefore, this project is focused on investigating possible background suppression of the XRF spectrum. First, an XRF setup has been built, and its capability has been compared to a commercial scanning electron microscope with energy dispersive spectroscopy (SEM-EDS). The qualitative analysis and semi-quantitative analysis of heavy metal contamination in fly ash was performed and compared. Due to minimal sample preparation, the developed XRF system is suitable for in-situ measurements. A series of experiments was performed to optimize the signal-to-noise ratio of the spectra achieved from chromium contaminated liquid samples. The most significant factor turned out to be the primary X-ray source filter. Numerical simulation models have been developed in the Monte Carlo N-particle radiation transport code (MCNP), to calculate the X-ray fluorescence intensities and the detection limit for chromium in liquid samples. The experimental results agree with the results predicted by the simulation model, hence the model is used for optimization of the XRF system. Further, XRF mapping of chemical element distributions on a microscopic level has been obtained by using both X-ray scanning microscopy and full-field projection microscopy. The resultingdata from these microscopy measurements can guide further comprehensive environmental and industrial monitoring missions by providing additional spatial distribution information. In conclusion, the first research contribution presented in this thesis is the demonstration of the possibility to perform in-situ XRF measurements of chromium contamination in leachate with a limit of detection below the legal environmental limits. The second is the demonstration of XRF mapping on amicroscopy level, where a polycapillary X-ray optics setup achieves a similar intensity as a geometrically corresponding pinhole optics setup.Vid tidpunkten för framläggningen av avhandlingen var följande delarbeten opublicerade: delarbete 2 (inskickat), delarbete 3 (accepterat), delarbete 4 (accepterat).
At the time of the defence the following papers were unpublished: paper 2 (submitted), paper 3 (accepted), paper 4 (accepted).
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CAMPOS, REJANE D. de. "Influência da mercerização e irradiação por feixe de elétrons na aderência da fibra do ouriço da castanha do Brasil em matriz de polietileno de alta densidade." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/25303.
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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
15
BOLORTUYA, Damdinsuren. "Portable X-Ray Fluorescence Spectrometer with High Sensitivity." Kyoto University, 2019. http://hdl.handle.net/2433/242503.
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Talboys, Dean Lee. "The Beagle 2 X-ray spectrometer for Mars." Thesis, University of Leicester, 2006. http://hdl.handle.net/2381/30588.
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This thesis is concerned with the Beagle 2 X-ray spectrometer (XRS) for Mars. The scientific goals of the XRS were to perform (i) geochemical analyses of Martian rocks and soils and (ii) in situ 40K >40Ar dating of rocks. The major aims of this study were the development of the XRS to achieve its scientific goals and to inform the design of future versions of the instrument. The XRS is described and compared with the previous X-ray Spectrometers that have been successfully deployed on Mars. A characterisation of the XRS investigated the fundamental behaviour of the instrument in terms of its spectral features (gain, resolution and artefacts), gain variation with temperature of its components, deadtime and quantum efficiency. The XRS was calibrated to convert elemental intensities from its analyses into concentrations. The concentrations of several major and trace elements of interest in reference materials were linearly correlated with the certified concentration. The analytical performance of the XRS was evaluated in comparison with a terrestrial portable X-ray spectrometer (PXRF) and a wavelength dispersive X-ray spectrometer (WD XRF). The performance was characterised in terms of accuracy, detection limit and fitting precision. This study showed the importance of energy resolution to the analytical performance of the XRS. The operational performance of the XRS was evaluated. The geochemical composition of several basalts analysed by the XRS agreed with complementary analyses by the PXRF and WD XRF. The 40K >40Ar radiometric ages for two basalts were determined using the K content in the basalts in conjunction with their 40Ar isotope content (analysed by a laboratory version of the Beagle 2 Gas Analysis Package). The 40K 40Ar ages were found to differ to the Ar-Ar ages because of various effects associated with inhomogeneity of the K content in the rock and radiogenic40Ar loss.
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PIASENTIN, RICARDO M. "Estudo da eletro-oxidação do etanol utilizando eletrocatalisadores PtPd/C+ATO e PtPdSn/C+ATO preparados via redução por borohidreto de sódio." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10546.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
18
SANTOS, LUCAS R. dos. "Desenvolvimento de um protocolo de calibração utilizando espectrometria e simulação matemática, em feixes padrões de raios x." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28026.
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A calibração, por definição, é o processo pelo qual se estabelece uma relação entre valores de medição de um padrão, com as suas respectivas incertezas, e as indicações com as incertezas associadas do instrumento de medição a ser calibrado. Um protocolo de calibração descreve a metodologia a ser aplicada em um processo de calibração. O método escolhido para a obtenção deste protocolo foi o da espectrometria de feixe de raios X associada à simulação pelo método de Monte Carlo, fundamentado no fato de que ambos são considerados métodos absolutos na determinação de parâmetros de feixes de radiação. Neste trabalho foi utilizado o método de Monte Carlo utilizado para obter a função resposta do detector utilizada para a correção dos espectros obtidos do feixe primário de radiação X; deste modo foram calculadas as taxas de kerma destes feixes e comparadas aos valores obtidos com as câmaras de ionização padrão secundário do Laboratório de Calibração de Instrumentos do IPEN (LCI/IPEN). Foram obtidos os coeficientes de calibração para o sistema padrão com diferenças em relação ao fornecido pelo laboratório primário entre 1,3% e 15,3%. Os resultados obtidos indicaram a viabilidade do estabelecimento deste protocolo de calibração utilizando a espectrometria como padrão de referência, com incertezas relativas de 0,62% para k=1. As incertezas associadas ao método proposto foram satisfatórias, para um laboratório padrão secundário e comparáveis a um laboratório primário.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
19
Liu, Ying. "Low Power Total Reflection X-Ray Fluorescence Spectrometry." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/192191.
Full text
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Megyery, Suzanna. "Sizing the X-ray spectral resolution limits of the REgolith X-ray Imaging Spectrometer (REXIS) instrument at Asteroid 1999RQ36." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/114130.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 64-68).
The REgolith X-ray Imaging Spectrometer (REXIS), a Charge-Coupled Device (CCD)-based coded aperture soft X-ray (0.3-7.5 keV) telescope for remote geochemical X-ray Fluorescence (XRF) spectrometry, will be flying on board the Origins Spectral Interpretations Resource Identification Security Regolith Explorer (OSIRIS-REx) asteroid sample return mission that will be visiting the asteroid 1999 RQ36 and sending a sample back to Earth. REXIS will detect elemental XRF lines and produce a histogram of results as the spacecraft orbits the asteroid as well as produce a global map of elemental abundance ratios. The accuracy requirement for measuring the global ratios of elements and the spectral resolution requirement for discriminating unique XRF lines from each other have been set in place. The correct interpretation of X-ray measurements from the surface of 1999 RQ36 is limited by properties that are intrinsic to the CCD detector, CCID-41, that has been chosen for REXIS. This thesis study outlines student experimentation and results that were conducted on the CCID-41 detector to gauge the intrinsic detector noise as a function of detector temperature. Further, the widening of spectral lines on the resultant histogram was also equated as a function of detector temperature. Members of the REXIS Team built a spectral resolution model to investigate both the widening of spectral lines as a function of detector temperature and the accuracy of the measurement of elemental abundance line ratios as a function of detector temperature. Data from the student laboratory experimentation suggested that the detector temperature remain at or below -75°C to minimize intrinsic noise properties. Data from the computational analyses of the spectral resolution model suggest consistent results that the detector temperature remains at or below -55°C to remain within the established REXIS requirements. The combination of these three results leads to the author's recommendation that a detector temperature requirement be set that the temperature of the CCD detector onboard REXIS shall not exceed -55°C and that a detector temperature goal be set that the temperature of the CCD detector shall not exceed -75°C.
by Suzanna Megyery.
S.B.
21
Demers, Hendrix. "Two facets of the x-ray microanalysis at low voltage: the secondary fluorescence x-rays emission and the microcalorimeter energy-dispersive spectrometer." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21993.
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The best spatial resolution, for a microanalysis with a scanning electron microscope (SEM), is achieved by using a low voltage electron beam. But the x-ray microanalysis was developed for high electron beam energy (greater than 10 keV). Also, the specimen will often contain light and medium elements and the analyst will have to use a mixture of K, L, and sometime M x-ray peaks for the x-ray microanalysis. With a mixture of family lines, it will be common to have secondary fluorescence x-rays emission by K-L and L-K interactions. The accuracy of the fluorescence correction models presently used by the analyst are not well known for these interactions. This work shows that the modified secondary fluorescence x-rays emission correction models can improve the accuracy of the microanalysis for K-L and L-K interactions. The general equation derived in this work allows the identification of three factors which influence the secondary fluorescence x-rays emission. The fluorescence production factor can be used to predict the importance of the secondary fluorescence x-rays emission. A large value of the fluorescence production factor indicates that a fluorescence correction is needed. Another disadvantage of using a low voltage is that there are more frequent occurrences of x-ray peaks overlap. A new microanalysis instruments that combines the high-spatial resolution and high-energy resolution for x-ray detection is needed. The microcalorimeter energy-dispersive spectrometer (uEDS) should improve the low voltage microanalysis, but the maturity of this technology has to be evaluated first. One of the first commercial uEDS for x-ray microanalysis in a SEM is studied and analyzed in this work. This commercial uEDS has an excellent energy resolution (15 eV) and can detect x-rays of low energy. This x-ray detector can be used as a high-spatial resolution and high-energy resolution microanalysis instrument. There are still hurdles that this technology must overcome before iPour la microanalyse par rayons X avec un microscope électronique à balayage (MEB), la meilleure résolution spatiale est obtenue à bas voltage. Cependant, la microanalyse par rayons X a été développée pour des grandes énergies du faisceau d'électrons (plus grandes que 10 keV). De plus, les échantillons analysés contiennent souvent des éléments légers et moyens. L'analyste va devoir utiliser un mélange de pics de rayons X K, L et parfois M pour la microanalyse par rayons X. Avec un aussi grand nombre de pics, l'émission de fluorescence secondaire de rayons X par des interactions K-L et L-K est inévitable. La précision des modèles de correction de la fluorescence utilisés présentement n'est pas bien quantifiée pour ces types d'interactions. Les modifications apportées, dans le cadre de ce travail, aux modèles de correction de la fluorescence améliorent la précision des résultats de la microanalyse pour les interactions K-L et L-K. L'équation générale dérivée dans ce travail permet l'identification de trois facteurs qui influencent l'émission de fluorescence secondaire de rayons X. Le facteur de production de fluorescence est utilisé pour prédire l'importance de l'émission de fluorescence de rayons X. Une grande valeur de ce facteur indique que la correction de fluorescence est nécessaire. Un autre désavantage d'utiliser une basse tension est le chevauchement des pics de rayons X qui se produit plus fréquemment. Un nouvel instrument de microanalyse qui combine une grande résolution spatiale et une grande résolution en énergie pour la détection des rayons X est nécessaire. Un spectromètre microcalorimétrique à dispersion d'énergie des rayons X (uEDS) devrait améliorer la microanalyse à basse tension, mais la maturité de cette technologie doit être évaluée. L'un des premiers spectromètre uEDS commercial pour la microanalyse par rayons X dans un MEB est étudié et analysé dans ce travail. Cet uEDS commercial$
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FONSECA, ANA C. M. "Processos de obtenção e caracterização físico-química de quitinas e quitosanas extraídas dos rejeitos da indústria pesqueira da região de Cananéia – SP." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26794.
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A quitina é o principal produto obtido do processamento das cascas de crustáceos. Esse biopolímero e o seu derivado, quitosana, têm despertado grande interesse comercial em virtude das possibilidades de aplicações que possuem. O gerenciamento desses resíduos e dos subprodutos gerados nas etapas no processo de obtenção pode ser considerado um modelo de biorrefinaria. A implementação de plantas para extração de quitina e quitosana é um desafio, uma vez que a demanda produtiva deve ser atendida sem causar danos ao meio ambiente. Uma grande variedade de quitosanas com diferentes propriedades físicoquímicas podem ser obtidas variando-se as condições de reação. Essas propriedades dependem da origem da matéria-prima, do seu grau médio de desacetilação, distribuição média dos grupos acetil ao longo da cadeia principal e da sua massa molecular média. Os fornecedores de quitosana comercial geralmente não mencionam a procedência da matéria-prima e pouca ou nenhuma informação é fornecida acerca do seu processamento. Sendo assim, as características e a reatividade do produto final podem variar gerando resultados não reprodutíveis. No presente estudo, foi utilizada a biomassa oriunda de rejeitos da indústria pesqueira de camarão da região de Cananéia SP. As amostras de - quitina foram obtidas por dois procedimentos diferentes: no primeiro, P1, as cascas de camarão após passar pelo pré-tratamento (lavagem, secagem e moagem) foram desproteinizadas para retirada das proteínas em hidróxido de sódio (NaOH) diluído nas concentrações 2%, 5% e 10% e desmineralizadas em ácido clorídrico (HCl) a 20% (v/v) para retirada dos carbonatos; no segundo procedimento, P2, essas etapas foram invertidas. A biomassa resultante foi desacetilada com hidróxido de sódio concentrado a 30%, 40% e 50% em tempos que variaram de 2 a 6 horas. As principais propriedades físico-químicas das amostras de quitosanas obtidas foram determinadas utilizando a espectroscopia na região do infravermelho com transformada de Fourier (FT-IR) para a determinação do grau médio de acetilação, GA, e a técnica de titulação ácido-base mensurada por condutimetria foi utilizada para comparar os resultados; a viscosimetria capilar para a determinação da massa molar média viscosimétrica, Mv , e a difração de raios X (DRX) para avaliar o grau médio de cristalinidade, X. Além disso, foram empregadas as técnicas de microscopia eletrônica de varredura (MEV) para análises morfológicas dos materiais obtidos e a espectrometria de fluorescência de raios X por dispersão de comprimento de onda (WDXRF) para análise química das quitosanas. O GA e o X das amostras diminuíram à medida em que o tratamento se tornou mais vigoroso, enquanto a Mv aumentou. O procedimento 2 foi o mais viável por eliminar a etapa de despigmentação, pois originou amostras com tonalidade mais clara e fáceis de pulverizar.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
23
Podpaly, Yuri Anatoly. "Upgrade of the neon soft X-ray spectrometer for Alcator C-Mod." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41680.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007."June 2007."
Includes bibliographical references (p. 40-41).
In order to study plasma rotation, temperature, and impurity density, a Neon Soft X-ray Spectrometer (NeSoXs) was installed on the Alcator C-Mod tokamak. This spectrometer used a spherically bent mica crystal as the reflective element in order to separate the spectral and spatial information on the receiving CCD. The original NeSoXs was found to have several problems including vacuum quality, camera readout rate, crystal positioning, chamber size, and chamber positioning. In order to remedy these problems, a new system was designed and has been constructed. This system has achieved much better vacuum pumping times (-100 times faster) and is in the process of being installed on the Alcator C-Mod vessel.
by Yuri Anatoly Podpaly.
S.B.
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Jenkins, Stephen Neil. "The development and application of a Transmission X-ray Photoelectron Spectrometer (TXPS)." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/843902/.
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There is a growing demand to obtain XPS analyses from increasingly smaller sample areas. The development of a Transmission X-Ray Photoelectron Spectrometer (TXPS) will allow spectrum acquisition and imaging with a lateral resolution approaching 1 mum2. The principle is based on back-foil excitation where thin samples are placed on an aluminium foil or have an evaporated source backing. Electron irradiation of the foil produces characteristic X-rays locally and this, in turn, gives rise to a small source of photoelectrons from the opposite side of the sample. Rastering the electron beam scans the X-ray interaction volume which allows imaging. Photoelectron lateral resolution is dependent on the sample and foil thicknesses and is determined by the width of the X-ray excitation envelope and on the electron beam diameter. In this work a VG Scientific MA500 is modified to give the ideal 180° geometry for TXPS. A hemispherical analyser with an extended high magnification transfer lens ensures a large solid angle of photoelectron collection, and the hemispherical analyser gives the (previously unobtainable) energy resolution necessary to obtain chemical state information. Aspects unique to TXPS spectral and image interpretation are described. The analysis conditions where sample damage is likely are investigated. Photon induced damage is manageable, but is shown to be far more of a technique drawback than Joule heating. Specimen charging presents no particular problems, although it can be both positive and negative in TXPS. It is believed that TXPS is the ideal way of examining ultramicrotomed sections through interfaces and soft composite materials. Harder materials, such as ceramics and metals, require ion beam thinning in a similar way to TEM specimens. Specimen production needs are addressed as well as the problem of making the TXPS technique far more routine to the analyst. A magnesium/aluminium alloy is ion beam thinned to demonstrate TXPS from a harder material. The interlayer between a chlorine containing latex and mild steel is also analysed by TXPS, following the removal of the bulk substrate and ultramicrotomy. Data are examined and an iron valence state change across the interface allows conclusions to be drawn about the continued growth of the protective interphase under environmental exposure.
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Wilemon, Billy B. Jr. "Portable X-Ray Fluorescence Spectrometer Analysis of the Pylos Linear B Tablets." Thesis, Mississippi State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10642684.
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This thesis investigates similarities in the chemistry of the Linear B clay tablets and sealings found at the Palace of Nestor in Pylos, located in the western Peloponnese. These similarities, or lack thereof, provide clues to the flow of material goods in and out of the palace and therefore to the degree of centralization of the government. Over a thousand 3000 year-old clay tablets and sealings currently housed at the National Archaeological Museum in Athens were analyzed using a pXRF over the course of the summers of 2015 and 2016. The chemical compositions were analyzed statistically. Results of the study and the conclusions are presented here.
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Kasemodel, Carlos A. "Quantitative energy dispersive x-ray spectrometry using an Emispec Vision system." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA374498.
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Thesis (M.S. in Applied Physics) Naval Postgraduate School, December 1999."December 1999". Thesis advisor(s): Alan G. Fox, James Luscombe. Includes bibliographical references (p. 69-70). Also available online.
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SILVA, SIRLANE G. da. "Estudo da oxidação eletroquímica do etanol em meio alcalino utilizando eletrocatalisadores PtAuIr/C e PdAuIr/C preparados via redução por borohidreto de sódio." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28037.
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Eletrocatalisadores Pt/C, Pd/C, PtAu/C, PtIr/C, PdAu/C, PdIr/C, PtAuIr/C e PdAuIr/C foram preparados via redução por borohidreto de sódio em diferentes proporções atômicas, com 20% em massa de metal e suportados em carbono Vulcan XC72 de alta área superficial. Os materiais foram caracterizados pelas técnicas de espectroscopia de energia dispersiva de raios-X (EDX), análise de difração de raios-X (DRX) e microscopia eletrônica de transmissão (MET). A oxidação eletroquímica do etanol foi estudada por voltametria cíclica (VC) e cronoamperometria, utilizando a técnica do eletrodo de camada fina porosa e o estudo da oxidação eletroquímica de etanol \"in situ\" utilizando espectroscopia de infravermelho com transformada de Fourier (FTIR). Posteriormente os materiais foram testados em células à combustível alcalinas alimentadas diretamente com etanol. Os resultados demonstraram que houve formação de ligas, com tamanho médio de nanopartículas entre 4,0 - 10 nm. De acordo com os experimentos eletroquímicos os eletrocatalisadores ternários apresentaram maior atividade eletrocatalítica e os estudos em FTIR indicaram que o produto principal da oxidação eletroquímica de etanol em meio alcalino para todos eletrocatalisadores sintetizados foi o acetato, sugerindo que a oxidação ocorre de forma incompleta pelo mecanismo indireto. Os testes em célula mostraram os melhores resultados para PdAuIr/C (50:40:10) com o qual obteve-se potencial de circuito aberto de aproximadamente 0,78 V e densidade de potência máxima de aproximadamente 15 mW cm-2, cerca de 333% superior a Pd/C.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
28
Bortoleto, Gisele Gonçalves. "Desenvolvimento de metodos analiticos usando espectrometria de raios X e quimiometria." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248809.
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Orientador: Maria Izabel Maretti Silveira BuenoTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Esta tese de doutorado apresenta uma inovação na química analítica abordando novas aplicações da técnica de fluorescência de raios-X, na qual o espalhamento da radiação X e a quimiometria exercem papel fundamental. Os sinais de espalhamento dos raios X provenientes da interação de diferentes fontes de excitação com amostras essencialmente orgânicas foram avaliados a partir de estudos realizados com um espectrômetro de bancada com tubo de Rh, como também com luz síncrotron, da linha de fluorescência de raios-X do Laboratório Nacional de Luz Síncrotron (LNLS), Campinas, SP, Brasil. Os resultados mostraram diferentes perfis de espalhamento da radiação para as diferentes fontes de excitação empregadas. Uma banda contínua em toda região espectral foi obtida como sinal, no caso do uso da luz síncrotron, e intensos picos em determinadas regiões espectrais caracterizaram os espalhamentos Compton e Rayleigh, quando o tubo de Rh foi utilizado. A alta intensidade da luz síncrotron resolveu os problemas de precisão intermediária observados nas medidas das amostras de álcoois realizadas com tubo de Rh. Em outro estudo, no qual os espectros de XRF de amostras de adoçantes dietéticos e óleos vegetais foram analisados por PCA, os resultados revelaram agrupamentos entre compostos com composições químicas ligeiramente distintas. Nesse caso, o uso do tubo de Rh foi adequado para atingir os objetivos propostos. Nas análises de óleos, a formação dos diversos grupos foi baseada nas variedades de óleos de soja, canola, girassol e milho. Nos testes realizados com adoçantes, os resultados mostraram uma tendência de diferenciação entre as amostras compostas por diferentes edulcorantes, principalmente entre aqueles que contêm ou que não contêm o átomo de enxofre em suas moléculas. O estudo realizado com amostra de urina conclui este trabalho, ressaltando mais uma vantagem do uso da XRF aliada a quimiometria: a possibilidade de realizar quantificações diretas e simultâneas de elementos inorgânicos e compostos orgânicos em amostras líquidas complexas. Nesse caso, um método para determinação de Ca, P, Na, K, Mg, Cl, uréia, glicose e creatinina em amostra de urina é apresentado, no qual os coeficientes de regressão da ordem de 0,99, obtidos para os modelos de calibração dos diferentes analitos, mostram a potencialidade da técnica para ser implementada em laboratórios de rotina.
Abstract: This work presents an innovation in analytical chemistry dealing with new applications of X-ray fluorescence technique in which the X-ray scattering effects and the chemometric tools play essential roles. X-ray scattering spectra resulting from interaction of simple organic samples were obtained with two sources, a common bench top spectrometer equipped with a Rh tube and also with synchrotron radiation (from the XRF beam line of the Laboratório Nacional de Luz Síncrotron (LNLS), Campinas, SP, Brazil). Distinct scattering profiles are observed for both excitation sources: a continuum for synchrotron light and intense peaks related to Compton and Rayleigh effects when a Rh tube is used. After processing the spectra from both sources, it was observed that the high intensity of synchrotron radiation solved the intermediate precision problems found in measuring samples via Rh tube. In another study, the spectra of sweetners and vegetable oils were analysed by XRF with PCA and the results showed distinct groupings for distinct samples. In this case, the Rh source was adequate to reach the objectives. In oil analyses, different groupings are based on the varieties of soybean, corn, canola and sunflower oils. In the case of sweetners, the results show a tendence to diferentiate samples of dissimilar artificial sweetners, especially when the presence of sulfur is of major importance. A study performed with urine samples is the final part of this work, poiting out one more advantage of using X-ray fluorescence with chemometrics, that is, the possibility of simultaneous and direct quantifications of inorganic elements and organic compounds in complex liquid samples. In this case a method for determining Ca, P, Na, K, Mg, Cl, urea, glucose and creatinine is presented with good regression coefficients being obtained for the different analytes. This can be taken as a good indication of the potential of the technique for implementation in routine laboratories.
Doutorado
Quimica Analitica
Doutor em Ciências
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Carte, David Brad. "The REgolith X-ray Imaging Spectrometer flight model : structural design, analysis, and testing." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98805.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 177-181).
Engineers of space flight programs face unique technical challenges created by the space environment in which these systems operate. High costs and increasing complexity of space programs create a greater demand for mission reliability. This demand further drives up development costs and project time lines. The result is that few missions are flown and few organization are able to participate in space program development. Project budget and schedule overruns are in part a result of a risk-averse culture and the desire the create fail-proof systems. Resource constrained programs will have difficulty developing successful space systems if they attempt to fully address every risk. Rather, by taking a risk-tolerant posture, resource-constrained programs can more efficiently allocate resources to the most important areas of a system's development. By focusing effort and resources on high-risk areas, successful space programs can still be developed with lower budgets and smaller schedules than has traditionally been done. Recent attempts to lower the time and budgets necessary to develop space systems have focused on developing smaller, less complex, and more numerous space system to replace traditionally larger, more expensive systems. The benefits of small space systems range from distributing risk across multiple systems and thereby lowering the cost of failure, to providing smaller organizations and universities the capabilities to develop their own space systems. Though these programs are cheaper, many organizations of small space systems are faced with limited resources that must be intelligently allocated to develop successful space programs. This thesis presents the structural design, analysis, and testing of the REgolith Xray Imaging Spectrometer (REXIS), a student-led instrument on board the National Aeronautics and Space Administration (NASA) Origins Spectral Interpretation Resource Identification and Security-Regolith Explorer (OSIRIS-REx) asteroid sample return mission. As part a student experiment, the REXIS team must develop its system under tight resource constraints. The limited funding, personnel, equipment, and facilities available to the REXIS team all have important implications on how design, analysis, and testing decisions are made on REXIS. This thesis provides a discussion of key areas of the REXIS structural development and lessons learned from a structural engineering point of view. Chapter 1 opens the discussion by talking about the motivation behind this thesis. It provides background information to the REXIS instrument and the context for the rest of the instrument discussion. The REXIS flight structural design and how this design facilitates the accomplishment of REXIS goals is presented in Chapter 2. Next, the analysis and testing of the Radiation Cover, one of REXIS's most critical elements, is described in Chapter 3. The key efforts taken on the REXIS structural development is discussed in Chapter 4. This particular section, through the discussion of the chronological development of the REXIS flight structural design, will highlight important areas of where efforts was focused on REXIS within the project constraints. Lastly, Chapter 5 provides lessons learned from a structural engineering point of view from the experiences on REXIS. Although the discussion focuses on the REXIS structural development, the examples and discussions described are relevant to other programs. This thesis is meant to provide insight into the REXIS development from which engineers of future small space programs can learn.
by David Brad Carte.
S.M.
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Saraci, Mirela P. "Errors in analysis of sulphide rich samples by x-ray fluorescence spectrometry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63060.pdf.
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Wurster, Bethany M. "A Geochemical Analysis of Tosawihi Quarries Chert Using X-Ray Fluorescence Spectrometry." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7526.
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Lithic source analysis, or “sourcing,” is a geochemical compositional analysis of lithic materials for both major and trace elements. Sourcing analysis assigns lithic sources to geochemical groups according to distinct geochemical compositions, where unique elemental signatures represent separate lithic sources. In archaeological research, sourcing informs upon mobility strategies, trade and exchange networks, and lithic conveyance studies. While obsidian sourcing is a relatively reliable and popular technique, chert sourcing is more difficult and historically less successful largely due to variability in chert formation processes. X-ray fluorescence spectrometry (XRF) offers a possible sourcing technique, and is non-destructive, as well as time and cost-effective. In this thesis, I test the reliability of XRF in determining the geochemical characterization of Tosawihi Quarries chert, a unique chert source located in the Humboldt River Basin of north-central Nevada.
The Tosawihi Quarries archaeological district (26EK6624) is a significant lithic resource that has hosted human occupation and activity for millennia. The Tosawihi Quarries offers a high quality toolstone that was intensely used, as indicated by numerous quarry locales and biface tool caches. Additionally, the Tosawihi Quarries is a social identity marker for the Tosawihi band of Western Shoshone, also serving as a source of spirituality and medicine. Tosawihi chert is a distinct, white lithic material type that also has a characteristic fluorescence pattern when exposed to ultraviolet light. While these are defining attributes, they are not unique to Tosawihi chert, as they occur in other Great Basin white chert sources. Identifying Tosawihi chert has been problematic, and misidentifications may have led to erroneous interpretations of the archaeological and ethnographic records. If successful, a geochemical characterization by XRF would provide an elemental signature specific to Tosawihi chert, thus eliminating discrepancies in visual and ultraviolet fluorescence readings and permitting archaeologists to accurately asses the distribution and use of this sacred material.
In this thesis research, I first conducted an XRF analysis of a source standard collection of Tosawihi Quarries chert, which yielded a preliminary methodology for identifying Tosawihi chert. This protocol was tested against two comparative collections of other Great Basin white cherts: Mono Lake Spillway located in western Nevada and Pahute Mesa (26NY1408) located in southern Nevada. The methodology, now refined, was then run against the archaeological collection, where five collections of white chert artifacts were tested for the presence of Tosawihi chert. Incorporating both the qualitative and quantitative data from XRF analysis, the results show that this proposed methodology can successfully discriminate between Tosawihi chert and other Great Basin white cherts based on its XRF signature.
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Charles, M. W. "An investigation of multilayer soap crystals for ultra soft X-ray spectrometry." Thesis, University of Leicester, 1989. http://hdl.handle.net/2381/35853.
Full textAbstract:
The extension of conventional monochromating techniques into the ultra soft x-ray region has been discussed. The use of large spacing pseudo crystals has been considered with particular reference to multilayer soap crystals. In an attempt to produce these crystals with the best possible x-ray reflection characteristics a detailed analysis of the building process and the associated parameters has been carried out. A specially constructed plane crystal spectrometer was used to obtain new extensive absolute reflectivity data for these optimised crystals. The results show that the crystals have an unusual structure exhibiting considerable imperfection. New reflectivity data for potassium acid phthalate (K.A.P.) crystals has also been obtained. Proportional counter detection was used throughout this work and in this connection proportional counter resolution has been studied in some detail. The importance of anode wire uniformity has been investigated in more detail than previously reported. By using a very smooth anode wire better resolution measurements have been obtained, in the 0.2-10 k.e.v. photon energy region, than reported in any previously published data.
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Zamalloa, Jara Marco Antonio. "Exploratory analysis for the identification of false banknotes using portable X-ray fluorescence spectrometer." Master's thesis, Pontificia Universidad Católica del Perú, 2018. http://tesis.pucp.edu.pe/repositorio/handle/123456789/13011.
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El objetivo de este estudio fue verificar si un espectrómetro portátil de fluorescencia de rayos
X (pXRF) puede reconocer las marcas de seguridad de los billetes originales que pueden
ser reproducidas por los falsificadores. Se estudiaron billetes peruanos: 4 genuinos y 3
falsos, en 11 puntos de análisis cada uno, correspondiendo a 77 conjuntos de datos. El
análisis de correlación de espectros entre los billetes originales fue 1.0, y no hubo
correlación con los billetes falsos. El pXRF demuestra que dos marcas de seguridad fueron
reproducidas por los falsificadores.The aim of this study was to verify if a portable X-ray fluorescence (pXRF) spectrometer can recognize the security features in banknotes that are reproducible by counterfeiters. Peruvian Nuevo Sol banknotes were studied: 4 genuine and 3 fake ones, in 11 points of analysis for each one, at all 77 data set. The correlation analysis of spectra among original notes was 1.0, and there was no correlation with fake banknotes. pXRF prove that two security features were reproducible for counterfeiters.
Tesis
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Röllig, Marco [Verfasser], and G. [Akademischer Betreuer] Drexlin. "Tritium analytics by beta induced X-ray spectrometry / Marco Röllig. Betreuer: G. Drexlin." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1099432324/34.
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Glinsman, Lisha. "The application of X-ray fluorescence spectrometry to the study of museum objects." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/88403.
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Sproch, Norman K. "PDI-PIXE-MS: Particle Desorption Ionization Particle-Induced X-Ray Emission Mass Spectrometry." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194827.
Full textAbstract:
Incident ions, from a Van de Graaff accelerator, in the MeV energy range, deposit their energy into the near surface of a sample. This, in turn, causes atomic, molecular, cluster and fragment ion species to be desorbed and ionized, while simultaneously emitting characteristic elemental X-rays. The multielemental X-rays provide qualitative elemental information, which may be deconvoluted and fit to a theoretical X-ray spectrum, generated by a quantitative analysis program, GUPIX, while the atomic, molecular, cluster, and fragment ion species are identified using a quadrupole mass spectrometer. This methodology directly links elemental determinations with chemical speciation.The development of this particle desorption ionization particle induced X-ray emission mass spectrometer, the PDI-PIXE-MS (or PIXE-MS) instrument, which has the ability to collect both qualitative multielemental X-rays and mass spectral data is described. This multiplexed instrument has been designed to use millimeter-sized MeV particle beams as a desorption ionization (PDI) and X-ray emission (PIXE) source. Two general methods have been employed, one simultaneous and the other sequential. Both methods make use of a novel X-ray/ion source developed for use with the quadrupole mass spectrometer used in these experiments. The first method uses a MeV heavy ion particle beam, typically oxygen, to desorb and ionize the sample, while simultaneously producing characteristic multielemental X-rays. The resulting molecular, cluster, and fragment ions are collected by the mass spectrometer, and the X-rays are collected using a Si-PIN photodiode detector in conjunction with a multichannel analyzer (MCA). Heavy ions of N+, O+, O+2, Ar+, and Kr+ have been investigated, although heavy ion X-ray and mass spectra have focused on the use of oxygen particle beams. The second method is performed by first collecting the X-ray data with a MeV ion beam of He+ ions, then desorbing and ionizing the sample species with a MeV particle beam of heavy ions, producing good ion yields, for mass spectral data collection. The potential development of a scanning microprobe instrument, that would provide micron-scale, imaged, multielemental, and molecular and fragment ion chemical information is being investigated through the development of this prototype PIXE-MS instrument.
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Tutt, James Henry. "Development of CCD and EM-CCD technology for high resolution X-ray spectrometry." Thesis, Open University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580126.
Full textAbstract:
This thesis discusses the development of Charge-Couple Device (CCD) and Electron Multiplying CCD (EM-CCD) technology for high resolution X-ray spectroscopy. Of particular interest is the spectral resolution performance of the devices alongside the optimisation of the quantum efficiency through the use of back-illuminated CCDs, thin filter technology and improved passivation techniques. The early chapters (1 through 5) focus on the background and theory that is required to understand the purpose of the work in this thesis and how semiconductors can be used as the detector of high resolution X-ray spectrometers. Chapter 6 focuses on the soft X-ray performance of three different types of conventional CCD using the PTB beamline at BESSY 11. The results show that there is degradation in spectral resolution in all three devices below 500 eV due to incomplete charge collection and X-ray peak asymmetry. The Hamamatsu device is shown to degrade faster than the CCD30-11 variants and this is attributed to the thickness of the active silicon (>50 urn] in the device and also its thicker dead-layer (~75 nm) which is found by evaluating the device's soft X-ray QE). The charge loss at the back-surface generation/recombination centres is also investigated and is found to be higher in the Hamamatsu device, again due to its thicker dead-layer. Chapter 7 is an investigation of the Modified Fano Factor which aims to describe the spectral resolution degradation that is expected when an EM-CCD is used to directly detect soft X-rays. The factor is predicted analytically, modelled and then verified experimentally allowing EM-CCD performance over the soft X-ray range to be predicted with high levels of confidence. Chapter 8 is a detailed look into work completed for the phase 0 study of the off plane X-ray grating spectrometer on the International X-ray Observatory. The work includes a detailed contamination study, effective area analysis, the pointing knowledge requirement and the use of filters to minimise optical background.
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SOUZA, LETICIA L. de. "Oxidação direta do etileno glicol sobre catalisadores eletroquímicos binários à base de Pt, Pd, e Sn suportados em carbono para aplicação em células alcalinas." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26934.
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Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-21T17:42:04Z
No. of bitstreams: 0Made available in DSpace on 2016-12-21T17:42:04Z (GMT). No. of bitstreams: 0
Os catalisadores eletroquímicos binários de PtSn/C, PdSn/C e PtPd/C foram sintetizados em diferentes proporções pelo método da redução via borohidreto, posteriormente estes foram caracterizados por microscopia eletrônica de transmissão, difração de raios X, espectroscopia no infravermelho por transformada de Fourier (PtSn/C e PdSn/C) e energia dispersiva de raios X. As atividades eletroquímicas dos diferentes materiais preparados foram avaliadas por intermédio de voltametria cíclica, cronoamperometria e curvas de polarização em célula a combustível alimentada diretamente por etileno glicol em eletrólito alcalino. As curvas de densidade de potência indicaram que os catalisadores eletroquímicos contendo Sn e Pd são mais ativos para a reação de oxidação do etileno glicol, especialmente a composição 70%:30% - relação molar entre os metais suportados em carbono - dos catalisadores PtSn/C, PdSn/C e PtPd/C todos superando as medidas de potência do Pt/C. Este resultado indica que a adição de Sn e Pd favorece a oxidação do etileno glicol em meio alcalino. O melhor desempenho observado para os catalisadores eletroquímicos PtSn/C, PdSn/C e PtPd/C (70%:30%) poderia estar associado à sua maior seletividade quanto a formação de oxalato, ou seja , a formação deste produto resulta em um maior número de elétrons, por consequência em maiores valores de corrente.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Valaparla, Sunil K. "Experimental study of the response of semiconductor detectors for EDXRF analysis." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Chodas, Mark A. "Improving the design process of the REgolith X-ray Imaging Spectrometer with model-based systems engineering." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93796.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 85-87).
Traditional systems engineering processes have supported the development of many complex and successful space systems. However, some systems experience significant cost and schedule overruns. Systems engineering capabilities need to be improved to manage the expected increase in complexity of future systems. Model-based systems engineering (MBSE) is a new systems engineering paradigm where system models instead of documents are used to track requirements, describe design, support trade studies and analyses, and track verification and validation activities. The system models can be studied to expose relationships and details that are impossible to find when information is scattered across many documents and analytical models. This thesis quantifies the advantages of MBSE over traditional systems engineering by comparing the historical development of the REgolith Imaging X-ray Spectrometer (REXIS), a student-built instrument on the OSIRIS-REx asteroid sample return mission, against a hypothetical development timeline that incorporates information from system models. The system models, constructed in SysML, capture the topological information about the system including the interfaces between all parts of the system, the uncertainty associated with each interface, and the path along which the consequences of selected design choices or requirements flow. The latter two types of information are captured with custom extensions to SysML. The models also provide useful statistics about the development process. The REXIS part count increased 104% between SRR and SDR and 163% between SDR and PDR while the interface count increased 93% between SRR and SDR and 174% between SDR and PDR. Evidence from REXIS shows that incorporating information from system models reduces design iteration and makes the design process more efficient.
by Mark A. Chodas.
S.M.
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Batista, Rafaela Tavares. "Caracterização de um sistema de fluorescência de raios X por dispersão em energia para análise quantitativa de ligas metálicas." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=4449.
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Neste trabalho são apresentados os procedimentos de caracterização de um sistema comercial portátil de Fluorescência de Raios X por dispersão em energia, o ARTAX 200, bem com seu processo de calibração. O sistema é composto por um tubo de Raios X, com anodo
de Molibdênio e um detector XFlash (Silicon Drift Detector) refrigerado por Efeito Peltier. O procedimento de caracterização do sistema foi realizado utilizando-se uma amostra de referência contendo Ferro e Cromo. Foram também usadas amostras certificadas (National Bureau of Standards) D840, D845, D846, D847 e D849 para a realização do processo de calibração do sistema para análise quantitativa. O processo de calibração foi realizado por três metodologias diferentes a fim de avaliar qual deles apresentaria melhores resultados. A caracterização do sistema ARTAX 200 foi realizada executando testes de estabilidade do tubo de Raios X, repetibilidade, reprodutibilidade, resolução em energia do sistema, levantamento da curva de limite de detecção e verificação do centro geométrico do feixe (CG). Os resultados obtidos nos testes de estabilidade apresentaram um coeficiente de variação médio menor do que 2%, o teste de repetibilidade apresentou valores médios menores que 0,5 %. A reprodutibilidade apresentou um coeficiente de variação médio menor que 1,5%. A verificação do centro geométrica mostrou que o CG encontra-se alinhada com o centro ótimo do feixe em duas das três direções do plano cartesiano. A resolução em energia do sistema para a energia de 5,9 keV foi de 150 eV. O limite de detecção apresentou valores menores que 1 % do Si ao Cu. Na avaliação das metodologias para calibração verificou-se que uma das metodologias aplicadas apresentou melhor resultado. Comparando os resultados com outros sistemas portáteis de XRF observa-se que o ARTAX 200 apresenta eficiência superior em relação aos parâmetros analisados.This paper presents procedures for characterization of a commercial system for portable X-Ray Fluorescence energy dispersive, the ARTAX 200, along with its calibration process. The system consists of an X-ray tube with molybdenum anode and a Silicon Drift Detector XFlash cooled by Peltier effect. The procedure for the characterization of the system was conducted using a reference sample containing Iron Chromium. We also used the certified samples (National Bureau of Standards) D840, D845, D846, D847 and D849 to perform the calibration of the system. The calibration process was conducted by three different methods: Methodology 1, Methodology 2 and Methodology 3, to evaluate them which present better results. The characterization system ARTAX 200 was performed by running stability tests of the X-ray tube, repeatability, reproducibility, resolution in energy of the system, limit of detection and verification of the geometric center of the beam. The results of the stability tests showed an average coefficient of variation of less than 2% repeatability test showed average values lower than 0.5%. The reproducibility showed a coefficient of variation of less than 1.5% which. The verification of the geometric center is aligned with the center of the great beam in two of the three directions of the Cartesian plane. The energy resolution of the system presented to the energy of 5.9 keV a resolution of 150 eV. The detection limit values were less than 1% of the Cu Si. In evaluating methodology for calibrating the best result was obtained with the methodology 3. Comparing the results with other portable XRF systems shows that the ARTAX 200 presents superior efficiency with respect to the parameters analyzed.
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Menendez-Alonso, Elena. "Trace metal and speciation analysis using ion-exchange and energy dispersive X-ray fluorescence spectrometry." Thesis, University of Plymouth, 2000. http://hdl.handle.net/10026.1/896.
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Studies have been carried out on specific ion-exchange (Dowex 50W-X8 and Dowex 1-X8) and chelation (Chelex-100) resins, in order to determine their physical and chemical characteristics, to understand and explain their limits of function and to optimise their use as substrates in trace metal and speciation measurement by EDXRF. Structural information was obtained by scanning electron microscopy and x-ray microanalysis showing a homogeneous distribution of functional groups and retained ions on both sectioned and whole resins. Particle size experiments performed on Dowex 50W-X8 (38 - 840 µm) showed that this parameter has no effect on the relationship between intensity of fluorescence and concentration or mass of resin. Inter-element effects were not observed in the analysis of multielemental specimens prepared on ion-exchange / chelation media by EDXRF. This indicates that the proposed method has a significant advantage when compared with other methodologies. A theoretical ‘model’, based on the formation of thin films on the surface of the resin beads, has been proposed in order to link and explain the effects observed in these experiments. The use of a batch retention system has shown distinct advantages over using columns in terms of linearity, accuracy, precision, rapidity and simplicity. Parameters such as pH and ionic strength of the solution, concentration of competing ions and volume of the sample have been proven to be critical. The maximum retention capacity has been determined as 3.2, 1.1 and 0.67 mEq/g for Dowex 50W-X8, Dowex 1-X8 and Chelex-100 respectively. The optimum mass of resin for XRF analysis was found to be 0.5 g, for all resins tested. The linear range covered 4 to 5 orders of magnitude. These findings show the potential of the investigated media to overcome instrumental and sample limitations. Based on the physico-chemical information found, methodologies for three different applications of the resins to EDXRF determinations have been developed and their analytical possibilities explored. The multi-elemental determination of metals in sewage sludge digests was achieved by retaining the metals on Dowex 50W-X8 at pH 2 and Chelex-100 at pH 4. Chelex-100 allows quantitative recoveries for Cu and Zn. A wider range of elements was determined on Dowex 50W-X8, although with poorer recoveries (60 - 90%). The limits of detection were 10 - 21 µg when Dowex 50W-X8 was used and 8 - 49 µg for Chelex-100. The method was validated by the analysis of a certified material. The determination of Kβ/Kα intensity ratios for Cr and Mn species and its potential as a tool for direct elemental speciation has also been studied. A difference in Kβ/Kα between the oxidation states of the analytes was only observed during the analysis of solutions of the metal species by EDXRF at the 98% level of confidence. Finally, the speciation and preconcentration of Cr(III) and Cr(VI) in waters has been performed by retention on Dowex 50W-X8 and Dowex 1-X8 followed by EDXRF determination. Efficient recoveries and preconcentration factors of up to 500 were achieved, leading to limits of detection of 30 µg/L for Cr(VI) and 40 µg/L for Cr(III). This method is simple, fast and inexpensive, allowing quantitative recoveries in the speciation of chromium in waste waters.
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PEÑAFIEL, MARLIN JEANNETTE PEDROZO. "DETERMINATION OF SILICON AND ALUMINUM IN CRUDE OIL USING ENERGY DISPERSIVE X-RAY FLUORESCENCE SPECTROMETRY." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33880@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA determinação de diferentes níveis de silício e alumínio em petróleo é importante porque pequenas quantidades destes elementos podem produzir efeitos adversos nas refinarias devido à corrosão de equipamento ou afetar a qualidade dos produtos refinados. A espectrometria de fluorescência de raios-X por dispersão de energia (EDXRF) foi utilizada para desenvolver um método para a determinação de Si e Al em petróleo, onde estes elementos se encontram principalmente sob a forma de partículas sólidas de aluminossilicatos dispersas na amostra. Uma vez que os analitos não puderam ser determinados sem interferência diretamente no óleo, a fusão das amostras de petróleo foi realizada utilizando tetraborato de lítio. Em seguida, as amostras fundidas foram colocadas no centro de papéis de filtro de 10 mm de diâmetro, que foi colocado entre duas folhas de filme de polipropileno, para então ser fixado à cubeta para as medições no instrumento. A quantificação foi feita por meio de curvas analíticas no intervalo de concentração de 0 a 40 mg kg(-1) (para ambos os elementos) no material fundido final. O método desenvolvido, não sofreu interferência matriz uma vez que as amostras foram completamente decompostas e, posteriormente secas no substrato. Os resultados para os elementos foram estatisticamente comparáveis com os obtidos por espectrometria de absorção atômica com chama (FAAS). Além disso, os resultados concordaram com os obtidos nas amostras de programas de proficiência da ASTM. Amostras reais de petróleo, fornecidas pela Petrobras, também foram analisadas. As recuperações alcançadas se encontram entre 71 e 100 por cento para as diferentes amostras, o qual pode ser considerado satisfatório devido à dificuldade em se determinar esses elementos. Os limites de quantificação (10 vezes o desvio-padrão, n=10) encontrados para o Si e Al no petróleo foram de 0,7 e 1,1 mg kg(-1), respectivamente, mostrando o potencial do método proposto para a determinação de amostras com valores mais elevados destes elementos.
It is important to determine silicon and aluminum at different levels in crude oils because of trace amounts of these elements may produce adverse effects in oil refining either by causing corrosion or by contaminating and affecting the quality of the refined products. Energy dispersive X-ray fluorescence spectrometry (EDXRF) was used to enable a reliable method for determination of Si and Al in crude oil, where these elements are found mainly in the form of solid aluminosilicate particles dispersed in the sample. Since the analytes could not be determined directly in the oil without interference, the fusing the crude oil samples was made using lithium tetraborate. Then, the fused samples were placed in the center of 10 mm diameter filter paper that were sandwiched between two polypropylene film foils and attached to the instrument cell for measurements. Quantification was made by using analytical curves in the concentration range from 0 to 40 mg kg (-1) (for both elements) in the final fused material. The method developed did not suffer from matrix effect once the sample matrix was completely decomposed and the sample solution dried in the substrate before measurements. The results for the elements were statistically comparable to the ones obtained by flame atomic absorption spectrometry (FAAS). In addition, for proficiency test samples, the results were in accordance to the ones reported by ASTM proficiency programs. Real samples of oil provided by Petrobras Company also were analyzed. Recoveries were achieved between 71 and 100 percent for different samples, which can be considerable satisfactory because of the difficulty in determine those elements. The limits of quantification (10 times the standard deviation. N = 10) found for silicon and aluminum in the oil were of 0.7 and 1.1 mg kg (-1), respectively, showing the potential of the proposed method to screen for samples with higher amounts of these elements.
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Sabbatucci, Lorenzo <1986>. "Fundamental and Applied Aspects of X-Ray Spectrometry: Detector Influence and Photoelectric Effect Cross-Sections." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7473/.
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The first part of this work reports the elementary theory of the atomic photoeffect presented in a form that is suited for practical numerical calculation. A detailed derivation of subshell cross sections for both excitation and ionization, comprising the angular distributions of emitted photoelectrons, is presented taking into account the effect of the polarization of the photons. The theoretical formulas have been implemented in a computer program PHOTACS that calculates tables of excitation and ionization cross sections for any element and subshell. Numerical calculations are practicable for excitations to final states with the principal quantum number up to about 20 and for ionization by photons with energy up to about 2 MeV. The effect of the finite width of atomic energy levels is accounted for by convolving the calculated subshell cross section with a Lorentzian profile. The second part of this work reports unfolding strategies for correcting a radiation measurement from the effects of the detector-pulse handling circuitry system. These strategies comprise the correction from the effects of pulse pile-up (PPU) and the detector response function (DRF). A first principles balance equation for second order PPU is derived and solved for the particular case of rectangular pulse shape. A Monte Carlo (MC) strategy is then implemented in the code MCPPU (Multi-shape pulse pile-up correction) allowing handling more general cases. Regarding the DRF, computed with deterministic or MC codes, it is presented the new tool RESOLUTION which introduces in the computed DRF the effects of energy resolution and incomplete charge collection. In the end the computer program UMESTRAT (Unfolding Maximum Entropy STRATegy) is presented in an updated version which include a new constrain to the total number of photons of the spectrum, which can be easily determined by inverting the diagonal efficiency matrix.
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Biswas, Pronoy K. (Pronoy Kumar). "Radiation management, avionics development, and integrated testing of a Class-D space-based asteroid X-ray spectrometer." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107050.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 161-165).
The Regolith X-ray Imaging Spectrometer (REXIS) is a student designed and built payload instrument aboard NASA's OSIRIS-REx asteroid sample return mission. The interplanetary target for this mission is a primitive asteroid known as Bennu that is believed to be relatively unchanged since the formation of the Solar System over 4.5 billion years ago. The primary goal of REXIS is to provide data to determine the elemental abundance composition of Bennu's surface through the measurement of X-ray fluorescence from Bennu's regolith. Achieving this goal requires the REXIS instrument to have an avionics system designed to operate the x-ray detectors, perform some preliminary processing of the x-ray events detected, and transfer this information to the main spacecraft computer for transmission to Earth. REXIS avionics accomplish these tasks using a mixture of commercial and spaceflight-grade hardware, reconfigurable Xilinx and Actel FPGAs, and a softcore MicroBlaze processor. Although the REXIS instrument is classified as a high-risk Class-D project by NASA, it must safely interface (in the manner of "do no harm") with the low-risk Class-B OSIRIS-REx spacecraft. Furthermore, REXIS must operate in the interplanetary space radiation environment of the OSIRIS-REx mission. This thesis details the REXIS avionics system and its novel features for collecting scientific x- ray data, interfacing safely with the OSIRIS-REx main spacecraft in spite of differing Class B/D risk postures, and robust operation in the interplanetary space radiation environment. Emphasis is placed on how the REXIS avionics design and radiation hazard mitigation features were implemented with significant budget and time constraints.
by Pronoy K. Biswas.
S.M.
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Pivovaroff, Michael James 1971. "X-ray astronomy with CCDs : calibration of the advanced CCD imaging spectrometer and observations of rotation-powered pulsars." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9026.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 2000.Includes bibliographical references.
This dissertation concerns the use of charge coupled devices (CCDs) for X-ray astronomy. Part I of this thesis focuses on the calibration of the Advanced CCD Imaging Spectrometer (ACIS), one of the two primary focal plane instruments on the Chandra X-ray Observatory. I begin by presenting a series of measurements made using undispersed synchrotron radiation. I analyzed the results of these experiments to extract parameters necessary to model the absolute detection efficiency of CCDs used as reference standards for ACIS characterization. I also discuss a novel "mesh" technique I pioneered to non-destructively measure the sub-pixel structure of CCDs, including the channel stops and gates. This work also provided a valuable tool for understanding the way charge is collected inside certain regions of the ACIS detectors. Guided by the results of the mesh experiments, I performed additional measurements to constrain recombination effects in the channel stops. Part II of this thesis concerns the X-ray properties of rotation-powered (radio) pulsars. High energy observations serve as a powerful diagnostic of the energetics and emission mechanisms of neutron stars. Associations between pulsars and the remnants of their supernovae provide independent measures of the distance and age of neutron stars, as well as constraints on their initial velocities, magnetic fields, and spin periods. I analyze ASCA and ROSAT observations of three young pulsars which are particularly well-suited for addressing these issues. I also present observations of the rotation-powered pulsar with the highest known magnetic field, and describe how the results relate to anomalous X-ray pulsars, another type of neutron star. Finally, I analyze Chandra observations of the supernova remnant Cas A. These data fully demonstrate the capabilities of ACIS and reveal a previously unknown point source at the center of the remnant.
by Michael James Pivovaroff.
Ph.D.
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Malezan, Alex. "Reconstrução espectral de tubos de radiação odontológicos usando a transformada inversa de Laplace da curva de atenuação." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-02092013-233953/.
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No estudo de imagens radiográcas, os parâmetros relacionados ao contraste objeto, SC, razão sinal ruído, SNR, e dose, estão vinculados à forma do espectro de raios X utilizado e seu conhecimento permite predizer e otimizar a qualidade da imagem. Neste trabalho foi desenvolvida uma metodologia que permite obter o espectro de tubos de raios X odontológicos de uso clínico de forma indireta. Esta metodologia é baseada na aplicação de um modelo matemático que utiliza a transformada inversa de Laplace da curva de transmissão do feixe para gerar dados sobre a distribuição espectral do mesmo. Com o auxílio de uma câmara de ionização e ltros alumínio de alta pureza, foram levantadas as curvas de transmissão de 8 tubos de raios X disponíveis comercialmente. Para a validação do método foi realizada a espectrometria direta com detector de telureto de cádmio (CdTe), cuja resposta foi determinada por simulação Monte Carlo (MC). A partir reconstrução espectral obtida, foram realizados estudos sobre os parâmetros de qualidade de imagem SNR, contraste objeto, SC, KERMA na entrada da pele. O desempenho dos tubos foi avaliado com base na relação entre SNR e KERMA na entrada da pele. Os resultados mostram que é possível determinar a distribuição espectral de tubos de raios X odontológicos com base no método proposto. A relação proposta entre SNR e KERMA na entrada da pele sugere que tubos com fótons de baixa energia possuem baixo rendimento.In the study of radiographic images, the parameters related to the subject contrast, SC, signal to noise ratio, SNR, and dose, are linked to the shape of the X-ray spectrum used and their knowledge allows to predict and optimize the image quality. In this work we developed a methodology to obtain the spectrum of dental X-ray tubes of clinical usage in an indirety way. This methodology is based on application of a mathematical model that uses the inverse Laplace transform of the attenuation curve to generate data on the spectral distribution of the beam. With the aid of an ionization chamber and high purity aluminum lters, were raised the transmission curves of 8 X-ray tubes that are available commercially. The method validation was performed with direct spectrometry detector cadmium telluride (CdTe), whose response was determined by Monte Carlo simulation (MC). From reconstruction obtained spectral studies were carried out on the parameters of SNR image quality, contrast object, SC, KERMA entrance skin. The performance of the tubes was evaluated based on the relationship between SNR and KERMA entrance skin. The results show that it is possible to determine the spectral distribution of dental X-ray tubes based on the proposed method. The proposed relationship between SNR and KERMA entrance skin suggests that tubes with low energy photons have a low performance.
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Sievers, Peter [Verfasser], and Anton [Akademischer Betreuer] Gisela. "Time-resolved and position-resolved X-ray spectrometry with a pixelated detector / Peter Sievers. Betreuer: Anton Gisela." Erlangen : Universitätsbibliothek der Universität Erlangen-Nürnberg, 2012. http://d-nb.info/1028958668/34.
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Van, Loggerenberg Daniël Elhardus. "Important trace element concentrations in ovine liver as determined by energy dispersive handheld X-ray fluorescence spectrometry." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/65518.
Full textAbstract:
Trace elements are involved in a variety of biochemical processes essential to life and are required in minute amounts. There are no data available on the use of handheld X-ray fluorescence (XRF) spectrometry to determine concentrations of important trace elements in ovine livers. The aim of this study was to ascertain if the handheld X-ray fluorescence spectrometer will provide reliable concentrations of certain essential trace elements in the livers of sheep. Sheep livers (n=30) were obtained from abattoirs. Wet liver samples taken from 30 liver specimens were blended until homogeneity was achieved. An aliquot of the homogenised liver samples were oven dried at 50°C until a constant mass and were then pulverised using a mortar and pestle to obtain a fine powder. In addition, homogenised liver samples (n = 30) were also submitted for dry ashing. All the prepared liver samples (i.e. wet blended, oven dried and dry ashed) were then analysed using a handheld X-ray fluorescence spectrometer to determine concentrations of copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), selenium (Se) and zinc (Zn). A reference laboratory analysed the same liver samples using ICP-MS to determine the concentrations of the above mentioned trace elements (control). The means (mg/kg) of the ICP-MS results on a dry matter basis were: Cu (505), Fe (351), Mn (12.3), Mo (3.8), Se (1.8) and Zn (168). The means (mg/kg) of the XRF oven-dried results were: Cu (502), Fe (289), Mn (11.7), Mo (1.6) and Zn (141.9). Selenium could not be detected in oven-dried samples when using the XRF. The intra-sample coefficients of variation were similar between ICP-MS and XRF for oven dried samples for Cu, Fe and Zn and are within the same order of magnitude for all elements in dry ashed samples when comparing ICP-MS to XRF. However, the intra-sample coefficients of variation for Mn and Mo were approximately an order of magnitude larger using XRF. Although the precision for Se appears to be good when using XRF on dry ashed samples, Se was only detected in a few samples, so this value is not representative of the overall precision of XRF using the dry ashed preparation procedure for Se determination. Selenium was not detectable using XRF on wet blended and oven dried samples. The intra-sample coefficient of variation for Se was relatively high using ICP-MS, suggesting that even the current ‘gold standard’ in detecting trace-elements may be imprecise in measuring Se. Overall, this suggests that the precision of sampling using XRF is relatively good for only Cu, Fe and Zn and relatively poor for Mn and Mo. Furthermore, XRF cannot be reliably used for measuring Se. Bayesian correlation were used to determine the best correlation between XRF and ICP-MS data. Bayesian correlation results are summarised by the median sample Pearson product-moment correlation coefficient (r), the 95% lower (LHPDI) and upper (UHPDI) highest posterior density intervals, the square of the sample correlation coefficient (r2), and the probability that the correlation coefficient is positive. Overall, the oven-dried preparation procedure for XRF appeared to provide the best correlation with the ICP-MS data. For Cu and Zn these correlations were strong and the XRF method may represent a suitable substitute for ICP-MS. For Mn and Fe the correlations were moderately strong and the XRF method may be suitable depending upon the intended application. For Mo the correlation was moderate and XRF cannot be recommended. For Se no XRF method was suitable. The advantage of handheld X-ray spectrometry is that the turnaround time of samples is reduced a great deal. Instead of submitting samples to a laboratory and waiting for results, samples can be analysed more rapidly with the use of a handheld X-ray fluorescence spectrometer.Dissertation (MSc)--University of Pretoria, 2016.
Paraclinical Sciences
MSc
Unrestricted
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Emprin, Benoit. "Développement d'optiques multicouches pour la spectrométrie X large bande du rayonnement émis par les plasmas." Thesis, Palaiseau, Institut d'optique théorique et appliquée, 2014. http://www.theses.fr/2014IOTA0014/document.
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Dans le cadre de ses recherches menées sur la fusion par confinement inertiel, le Commissariat à l’énergie atomique et aux énergies alternatives met en œuvre un spectromètre X large bande étalonné en absolu et résolu en temps, appelé Diagnostic de Mesure du rayonnement X. Ce diagnostic, composé de 20 voies de mesure, permet de mesurer l’émissivité spectrale d’un plasma créé par laser entre 50 eV et 20 keV. Nous avons développé des voies de mesure complémentaires aux voies existantes, afin d’obtenir une redondance et une amélioration de la précision de la mesure. Le principe de ces nouvelles voies de mesure repose sur un concept original permettant d’obtenir des fonctions de transfert spectrales bornées et constantes. Deux voies ont été développées pour les gammes spectrales 2 – 4 keV et 4 – 6 keV, utilisant des miroirs multicouches apériodiques réalisés au Laboratoire Charles Fabry en Cr/Sc et Ni/W/SiC/W, respectivement. Ces miroirs ont ensuite été caractérisés sur synchrotrons puis intégrés dans le spectromètre. Les nouvelles voies ont été utilisées durant des campagnes d’expériences laser-Plasma sur l’installation laser OMEGA à Rochester (États-Unis). Elles ont permis de déterminer la puissance rayonnée directement avec une seule voie de mesure par bande spectrale et avec une meilleure précision qu’avec celles utilisées habituellement. Les résultats, en bon accord avec les voies de mesure classiques, permettent de valider l’utilisation des miroirs multicouches apériodiques pour la spectrométrie X large bandeWithin the framework of the research on inertial confinement fusion, the “Commissariat à l’énergie atomique et aux énergies alternatives” has studied and implemented an absolute calibrated time-Resolved broadband soft x-Ray spectrometer, called “Diagnostic de Mesure du rayonnement X”. This diagnostic, composed of 20 measurement channels, measures the emitted radiant power from a laser created plasma in the range from 50 eV to 20 keV. We have developed additional measurement channels to obtain redundancy and an improvement in measurement accuracy. The principle of these new channels is based on an original concept to obtain spectral bounded flat-Responses. Two channels have been developed for the 2 – 4 keV and 4 – 6 keV spectral ranges, using aperiodic multilayer mirrors made at the “Laboratoire Charles Fabry” with Cr/Sc and Ni/W/SiC/W layers respectively. These mirrors were characterized at synchrotron radiation facilities and integrated into the spectrometer. The two new channels were used during laser-Plasma experimental campaigns at the OMEGA laser facility in Rochester (USA). This allowed us to determine directly the radiant power with only one measurement within a certain spectral band, and with a better precision when compared with using standard channels. The results, in good agreement with the standard measurement channels, allowed us to validate the use of aperiodic multilayer mirrors for X-Ray broadband spectrometry