Made available in DSpace on 2014-10-09T12:41:04Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:03Z (GMT). No. of bitstreams: 1 04674.pdf: 2960498 bytes, checksum: 31da12ce5904c3db2729e9982663d7fe (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:51:47Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:10:00Z (GMT). No. of bitstreams: 0 / As cirurgias radioguiadas, utilizando sondas com detectores de radiação, têm sido destaque na área médica na última década. Esta técnica consiste na marcação de lesões com uma substância radioativa, que injetada no paciente, concentra-se no tumor e auxilia a sua localização durante o ato cirúrgico. Entre as cirurgias radioguiadas, a identificação e exame do linfonodo sentinela, tem revolucionado a conduta de neoplasias em estádio inicial, quando estas estão sendo disseminadas pela via linfática. As condições impostas por uma cirurgia e a proximidade entre alguns linfonodos, exige das sondas, reduzidos diâmetros e capacidade de identificação individual destes linfonodos marcados com um radiofármaco. O mercado internacional fornece sondas adequadas com cristais cintiladores e com semicondutores de telureto de cádmio, CdTe, mas que algumas vezes carecem de uma pronta assistência técnica no mercado brasileiro devido a todo o conjunto ser importado. Este trabalho desenvolveu sondas com tecnologia nacional, utilizando cristais cintiladores de iodeto de césio dopado com tálio, CsI(Tl) e, em substituição aos cristais semicondutores de CdTe, o cristal de brometo de tálio, TlBr que é um meio semicondutor detector em desenvolvimento mundialmente, com vantagens em relação ao CdTe. Ambos os cristais utilizados foram crescidos no IPEN. Toda a eletrônica necessária, e em especial, o pré-amplificador, que constituía também um fator limitante para desenvolvimento destes tipos de sonda no país, foram desenvolvidos com componentes encontrados no mercado nacional. Medidas sistemáticas de resolução espacial, seletividade espacial, sensibilidade máxima e qualidade da blindagem foram realizadas para as sondas desenvolvidas. Os resultados mostraram que dois modelos de sonda, uma com o cristal de CsI(Tl) e outra com o semicondutor de TlBr atenderam as qualidades sugeridas pela literatura internacional para sondas cirúrgicas radioguiadas. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-22T16:42:56Z No. of bitstreams: 0 / Made available in DSpace on 2016-12-22T16:42:56Z (GMT). No. of bitstreams: 0 / Neste trabalho foi desenvolvido um Espectrômetro de Correlação Angular Gama- Gama Perturbada Diferencial em Tempo (CAP) constituído por seis detectores cintiladores de BaF2, para realização de medidas de interações hiperfinas (campo hiperfino magnético e gradiente de campo elétrico) em diversos materiais e propiciar estudos na área da física da matéria condensada. O espectrômetro desenvolvido possui um sistema de aquisição não convencional em comparação aos demais equipamentos destinados a medidas de CAP. Ao invés do tradicional Analisador Multicanal (MCA), este espectrômetro utiliza um sistema de aquisição de dados constituído, basicamente, por um Conversor Analógico Digital (ADC) rápido, uma placa digital (I/O) convencional e um roteador construído no laboratório de Interações Hiperfinas (LIH) do IPEN. Este versátil e eficiente sistema, controlado por um software também criado no LIH em LabVIEW, permite a geração simultânea de 30 espectros de coincidências γ - γ atrasadas, número superior em comparação aos 12 espectros do antigo espectrômetro de quatro detectores. Além de medidas de linearidade, resolução em tempo e tempo morto, o funcionamento e o desempenho do espectrômetro foram comprovados através de medidas de CAP utilizando os núcleos de prova 111In -> 111Cd e 181Hf -> 181Ta, cujos resultados são bem conhecidos da literatura. Foram feitas medidas de interação quadrupolar do 181Ta em háfnio metálico e do 111Cd em cádmio metálico, e de campo hiperfino magnético do 111Cd e do 181Ta em níquel. Os resultados destas medidas se mostraram em concordância com a literatura. Adicionalmente foram realizadas medidas inéditas de interações hiperfinas magnéticas no composto intermetálico LaMnSi2 utilizando os núcleos de prova 111Cd e 140Ce. As medidas foram realizadas na faixa de temperatura de 10 K a 400K. No caso das medidas utilizando a sonda 111In -> 111Cd, os resultados mostram uma variação do campo magnético com a temperatura que segue a função de Brillouin. Já no caso das medidas com o núcleo de prova 140La -> 140Ce, o resultado apresentou um comportamento anômalo do campo hiperfino em função de temperatura. Os resultados evidenciam uma forte hibridização da banda 4f do Ce com a banda 3d do Mn, fato verificado e estudado em trabalhos anteriores com compostos semelhantes. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-23T11:10:00Z No. of bitstreams: 0 / Made available in DSpace on 2017-11-23T11:10:00Z (GMT). No. of bitstreams: 0 / O processamento por radiação gama para beneficiamento de produtos tem se tornado uma tecnologia aceita mundialmente. Tem como aplicações a esterilização de produtos médicos, a irradiação de alimentos e produtos agrícolas, a modificação de materiais poliméricos e biomateriais, a preservação de objetos de patrimônio cultural, a esterilização de tecidos humanos para transplante, a mudança de cor em gemas, dentre outros. Desde 2004, o Irradiador Multipropósito de Cobalto-60 do Centro de Tecnologia das Radiações do IPEN tem sido utilizado no estudo e aperfeiçoamento dessas aplicações com objetivos de pesquisa e no estabelecimento de aplicações rotineiras. Este, embora concebido para trabalhar no modo contínuo de irradiação, é utilizado no modo estacionário mais indicado para irradiações de materiais delicados ou de pesquisa. Neste trabalho foram validadas e verificadas experimentalmente as adequações dos métodos à irradiação estacionária; bem como as interrupções para medição de doses em dosímetros de polimetilmetacrilato em processos fracionados, onde seu uso se mostrou adequado para taxas de dose maiores que 2kGy·h-1. A descrição do processo de carga das fontes mostra a importância do seu planejamento e seu impacto na distribuição de taxas de dose. Os mapeamentos das doses e taxas de dose permitiram localizar regiões de valores homogêneos e máximos. Foi estabelecido um procedimento de irradiação de tecidos para aloenxertia utilizando monitoração dosimétrica externa. Foram levantados os custos e despesas de irradiação, aplicáveis a instalações governamentais. O balanço energético da piscina de armazenamento das fontes permitiu calcular o fluxo de calor do sistema e definir as condições máximas de operação sem trocador de calor. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

[pt] A confiabilidade metrológica da medição de elevadas temperaturas em processos industriais é importante para a segurança, qualidade e as características de produtos de diversas indústrias do Brasil. Devido ao fato de que a rastreabilidade dos resultados de uma calibração de termômetro de radiação infravermelha, utilizado para a medição de processos industriais, é assegurada pelo Inmetro (Instituto Nacional de Metrologia, Normalização e Qualidade Industrial) até 1500 graus Celsius, e levando-se em consideração que as condições de calibração em laboratórios são normalmente diferentes das de medição na indústria, um procedimento foi desenvolvido e validado nesta dissertação para analisar a confiabilidade da mesma em temperaturas mais elevadas (1750 graus Celsius), estimando-se os valores de erros sistemáticos e de incerteza de medição da temperatura em um forno industrial. / [en] The accuracy of high temperature measurement in industrial processes is important for safety reasons and product quality and specification in different industries. Due to the fact that the traceability of temperature measurement by infrared thermometers, as used in industrial processes, is only assured by Inmetro (National Institute for Metrology, Standards and Industrial Quality) up to 1500 Celsius Degree, and considering that the calibration conditions in laboratory are normally different from measurement conditions in industry, a procedure in the dissertation was developed and validated to analyze the accuracy of higher temperature measurement (1750 Celsius Degree), estimating systematic errors and uncertainty of measurement of temperature in a industrial furnace.

Title: Photo-Hall effect spectroscopy and laser-induced transient currents in CdTe-based semiconductor radiation detectors Author: Artem Musiienko Department / Institute: Institute of Physics, Faculty of Mathematics and Physics, Charles University Supervisor of the doctoral thesis: Prof. RNDr. Roman Grill, CSc, Institute of Physics, Faculty of Mathematics and Physics, Charles University Abstract: Cadmium Telluride, Cadmium Zinc Telluride, and Cadmium Manganese Telluride are important semiconductors with applications in radiation detection, solar cells, and electro-optic modulators. Their electrical and optical properties are principally controlled by defects forming energy levels within the bandgap. Such defects create recombination and trapping centers capturing photo- created carriers and depreciating the performance of the detector. Simultaneously, the changed occupancy of levels leads to the charging of detector's bulk, which results in the screening of applied bias and the loss of detector's sensitivity. Detailed knowledge of crystal defect structure is thus necessary for the predictable detector work and also for the possibility to reduce the structural defects concentration. This thesis reports on the investigation of deep energy levels in CdTe-based high resistivity and detector-grade materials by...

With rapidly increasing datasets and more dynamic workloads, adaptive partial indexing becomes an important way to keep indexing efficiently. During times of changing workloads, the query performance suffers from inefficient tables scans while the index tuning mechanism adapts the partial index. In this paper we present the Adaptive Index Buffer. The Adaptive Index Buffer reduces the cost of table scans by quickly indexing tuples in memory until the partial index has adapted to the workload again. We explain the basic operating mode of an Index Buffer and discuss how it adapts to changing workload situations. Further, we present three experiments that show the Index Buffer at work.

Radiations can be classified as either ionizing or non-ionizing according to whether it ionizes or does not ionize the medium through which they propagate. X-rays photons and gamma rays are the typical examples of ionizing radiations whereas radiowave, heat or visible light are examples of non ionizing radiations. UV photons have some features of both ionizing and non-ionizing radiation. Both ionizing and non-ionizing radiation can be harmful to living organisms and to the natural environment. Hence the detection and measurement of radiation is very important for the well being of living organisms as well as the natural environment. Not only for safety reasons, have radiation detectors found their applications in various fields including medical physics, nuclear and particle physics, astronomy and homeland security. Industrial sectors that use radiation detection include medical imaging, security and baggage scanning, the nuclear power industry and defense. Gas electron multiplier (GEM) is one of the most successful representatives of gaseous detectors used for UV photon and X-ray photon detection. Recently there is a growing demand for large area photon detectors with sensitivity reaching to the level of single photon. They are used in spectroscopy and imaging in astronomy high energy physics experiments etc. Thick GEM (THGEM) is a mechanical expansion of standard GEM. It has all the necessary requirements needed for large area detector and offers a multiplication factor that permits efficient detection of light. Hence, the development and performance study of THGEM based radiation detector is chosen as the topic of study in the present thesis. The initial part of the thesis contains simulation studies carried out for the understanding the working of the detector and the effect of various design parameters of THGEM for the above said applications. Different steps for the fabrication of THGEM and the technical challenges faced during the process are discussed. In the view of application of the fabricated THGEM for UV photon detection, cesium iodide photocathode is prepared using thin film technology and characterized. The performance of the photocathode under various operating conditions is studied in terms of its photoemission property. The effect of vacuum treatment on the photoemission property of the photocathode exposed to moist air is studied in detail. A major portion of this thesis focuses on maximizing the detection efficiency of the UV photon detector realized using the fabricated THGEM coupled with the cesium iodide photocathode. Simulations are used at different stages to interpret the experimental observations. The electron spectrum obtained from the detector under study was analyzed. The dependence of secondary effect like photon feedback on the operating parameters is also discussed. The last portion of the thesis deals with the application of THGEM as an X-ray detector. The performance is evaluated in terms of the gain and energy resolution achieved. The thesis is organized as follows: Chapter 1 is divided into two sections. Section A gives a general introduction to different types of radiation detectors found in the present day and their working principles. This is followed by discussion about gas ionization based detector and its working principle in detail. A brief literature survey of the different types of micropattern gas detectors is also given in this section. In Section B of this chapter GEM and THGEM are introduced with discussion about their working principle and areas of application. Chapter 2 deals with the simulation study of THGEM undertaken to have a clear understanding of the detector’s working. Section A of this chapter gives an overview of the simulation tools used for the present thesis in particular ANSYS and GARFIELD. Section B presents the results of the simulation study highlighting the effects of different geometrical and operating parameters on the electric field distribution in and around the THGEM aperture. The relevance of the study to the detectors performance is discussed vividly for all the cases. In Chapter 3, the details of the different steps involved in THGEM fabrication are given. Design aspects involved, fabrication of the THGEM using standard PCB technology coupled with photolithography technique are discussed in this chapter. This is followed by an elaborate description of the test setup used for all the performance study. Preface In the view of application of THGEM as a UV photon detector, cesium iodide photocathode was prepared and characterized. Chapter 4 discusses about the CsI photocathode preparation and its characterization for the above said application. Photoemission property of the photocathode was analyzed under various operating parameters. The effect of vacuum treatment on the photocathode performance is a new aspect of this thesis. Its correlation with the microstructure of the film is reported for the first time. Chapter 5 deals with the application of THGEM as a UV photon detector. The study mainly focuses on the improvement of the detection efficiency of the detector. The effect of drift parameters on the electron transfer efficiency and hence on the detection efficiency of the detector is a major contribution of this thesis. There are no literature available which discusses this aspect of a UV photon detector. The experimental study has been supported with simulation results. In addition to the study on detection efficiency, electron spectrum has also been acquired from the UV photon detector. The spectrum has been analyzed under various operating conditions. Discussions about secondary effects like photon feedback prevailing in the detector output are also present in this chapter. Chapter 6 presents the results of THGEM as an X-ray detector. The performance of the detector has been evaluated in terms of the effective gain and energy resolution achieved under different operating conditions. The gain instability with time and its uniformity across the THGEM area are also studied. The effect of drift field on the energy resolution and its correlation with ETE is a new aspect of this work. Chapter 7 summarizes the salient features of the work presented in this thesis. Also the scope of future work based on this thesis is discussed at the end of the chapter.

Failed fuel refers to the breach in the fuel-clad of an irradiated fuel assembly in a nuclear reactor. Neutron detection or gamma detection is commonly used in Failed Fuel Detection and Locating (FFDL) system to monitor the activity of the coolant. Though these methods offer specific advantages under different conditions of the coolant, providing both types of detectors in FFDL system is impractical. This limitation is the motivation for the detector system developed in the present work. In the present work, effort has been made for realising a detector system for simultaneous measurement of neutron and gamma activity of the coolant, thus offering a two-parameter basis for failed fuel detection. NE213 liquid scintillator was chosen for this work as it has good detection capability for both neutrons and gammas. Additionally, the neutrons and gammas interacting with NE213 detector can be separated based on pulse shape discrimination. The work reported in this thesis includes fabrication details and different steps followed in assembling the NE213 detector. Details of experimental set-up developed for pulse height analysis and pulse shape analysis are covered. Results of experiments carried out to study the response of the NE213 detector to gamma and neutron sources using pulse height analyser are presented. The absolute gamma efficiency and relative gamma efficiency of NE213 detector are calculated. Neutron–gamma separation capability of NE213 detector based pulse shape analysis system is reported. Application of the developed detector system to analyse the coolant activity in FFDL system in a reactor is described. Response of the detector is compared with the existing FFDL system at different power levels of the reactor. Since failed fuel is a rare event, it was simulated using neutron and gamma sources. Pulse shape analysis spectra obtained under simulated failed fuel condition are presented.

Made available in DSpace on 2014-10-09T12:51:21Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:28Z (GMT). No. of bitstreams: 1 11295.pdf: 3731608 bytes, checksum: 642672d3ddbbe81953275dd174a58822 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:01/09049-5