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1
Serra, André da Silva. "66Ga como padrão de calibração de raios de altas energias para detectores HPGe." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-10102008-142839/.
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Este trabalho trata do estudo da eficiencia de pico e fun¸cao resposta de detetores semicondutores do tipo HPGe na faixa de energia entre 2 a 5 MeV, um pouco acima da faixa de energia das fontes usualmente dispon´veis em espectroscopia . Ele faz parte de um projeto de calibra¸cao de detetores em altas energias (at´e 20 MeV). Os resultados serao utilizados na obten¸cao das intensidades das radia¸coes de rea¸coes foto-nucleares produzidas por meio do bremstrahlung do feixe de el´etrons de 38 MeV do acelerador Microton em constru¸cao. Trabalhos anteriores utilizaram raios produzidos por rea¸coes ressonantes de captura de pr´otons (p,x ). Entretanto, a cinem´atica da rea¸cao, em particular o efeito Doppler, altera a posi¸cao e forma dos picos observados. De modo a evitar estes efeitos indesej´aveis, este experimento utilizou uma fonte radioativa de raios de altas energias 66Ga (que recentemente tornou-se um dos padroes secund´arios de calibra¸cao). A fonte de 66Ga foi produzida por meio do bombardeamento de uma chapa de 1,0 mm de natZn de alta pureza (> 99,99%) utilizando um feixe de pr´otons de 15 MeV do ciclotron Cyclone 30 do Instituto de Pesquisas Energ´eticas e Nucleares IPEN, atrav´es das rea¸coes nucleares 66Zn(p,n) e 67Zn(p,2n). O espectro resultante foi analisado com o software IDFIX e foi obtida a curva de calibra¸cao de eficiencia de pico de um detetor HPGe de 162 cm3 de volume ativo e eficiencia de pico de 33% relativa a um cristal de 3×3 de Na(Tl) para o gama de 1332 keV do 60Co. Finalmente, foi realizada uma simula ¸cao do processo de transporte de radia¸cao por meio do software MNCP5 e os resultados obtidos encontram-se em acordo com os experimentais.This work involves the study of the peak efficiency and response function of HPGe detectors for gamma rays in the energy range of 2 to 5 MeV, somewhat above the energy range of the available calibration sources for gamma spectroscopy. It is part of a high energy (up to 20MeV) -ray project to obtain intensity of rays from photo nuclear reactions produced with the bremstrahlung from the 38MeV electron beam of the Microtron accelerator. Former works carried out in the Laborat´orio do Acelerador Linear - LAL (IFUSP) used gamma rays produced by well-known (p,x ) resonant reactions. However reaction kinematics disturbs the position and form of the observed gamma peaks mainly due to the Doppler effect. In order to avoid these problems, a radioactive source with high energy gamma-rays, 66Ga (which recently became one of the secondary efficiency calibration standard), was used. The 66Ga source was produced by bombarding a 1.0 mm foil of pure natZn (> 99,99%) with the 15MeV and 0.1A proton beam from the Cyclone 30 cyclotron of the Instituto de Pesquisas Energ´eticas e Nucleares - IPEN with 66Zn(p,n) and 67Zn(p,2n) nuclear reactions. The resultant spectra were analyzed using the IDFIX program and the peak efficiency calibration curve was obtained for the HPGe detector with 162cm3 of active volume and a efficiency of 33% relative to a 3×3Na(Tl) crystal for 1332 keV 60Co ray. Finally, it was undertaken a Monte Carlo radiation transport analysis using a software such as MNCP5. The experiment was simulated and the results are in agreement with the experimental ones.
2
Crespi, F. C. L. "HPGe segmented detectors in γ-ray spectroscopy experiments with exotic beams." Doctoral thesis, Università degli Studi di Milano, 2008. http://hdl.handle.net/2434/59487.
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Most of the present knowledge of the nuclear structure is based on the properties of
nuclei that lie in the valley of stability; it has become clear that it is in general not
possible to extrapolate such knowledge to the region far off stability. Consequently,
in order to obtain an overall comprehension of the nuclear force, it is mandatory to
probe the structure of exotic nuclei. In recent years the availability of Radioactive Ion
Beams (RIB) enabled the experimental study of nuclear systems far off stability and
consequently gave the possibility to attach fundamental open problems in this
research field.
Gamma ray spectroscopy experiments with radioactive beams have to be performed
in critical conditions due to low beam intensity, the presence of large background
radiation and relevant Doppler effects. As a consequence it has become clear the
need for developing a gamma detector array with a sensitivity much higher compared
with the present generation Compton-suppressed detectors: a 4π gamma
spectrometer, composed of highly segmented HPGe detectors and based on the
concept of γ-ray tracking.
In this thesis will first be described a Coulomb excitation measurement with the
exotic 68Ni nucleus that presents all the challenging features of the experiments in
which new generation tracking arrays are planned to operate. Such experiment has
been carried out in April 2005 at RISING [63] set up in GSI laboratory. It consists of
coulomb excitation of 68Ni at 600 MeV/u performed in order to study the low lying
dipole strength by direct measurement of the gamma decay. The question how the
giant dipole resonance strength evolves when going from stable to exotic nuclei is
presently under discussion. It is in general expected by the calculations to find, in
neutron rich medium heavy and heavy nuclei, a stronger fragmentation of the dipole
strength (compared to stable nuclei) with significant components located in an energy
domain well below that of the giant dipole resonance. In the literature such a lowlying
concentration of dipole strength is usually denoted as Pygmy Dipole Resonance (PDR). The impact of that research activity goes even beyond nuclear structure field.
In fact, since the energy dependence of the dipole strength directly affects the (γ,n)
cross section, the presence of an increase in the low lying dipole strength could
relevantly change our understanding and the description of the r-process. The results
of the data analysis show the first evidence of such pygmy states in 68Ni; in addition
it will appear clearly the need for a gamma detector array capable to provide an
improved quality in Doppler correction and background rejection, namely a gamma
ray tracking array.
Recently the concept of γ ray tracking detectors has been developed and it has been
shown that even a factor of 1000 in sensitivity over previous generation arrays could
be gained using an array of detectors that enables the gamma ray path to be
reconstructed. Reconstructing the trace of a γ ray inside the detector will permit a
very precise Doppler correction since the position of the first interaction is obtained
with a resolution of some mm, furthermore it will be possible to deduce the γ ray
incoming direction and therefore distinguish the radiation of interest from the one not
coming from the target, obtaining consequently much cleaner spectra.
A second topic discussed in this thesis is the Pulse Shape Analysis in segmented
HPGe detector for the gamma ray tracking. Pulse Shape Analysis (PSA) for
determination of interactions position is a fundamental step in the functioning scheme
of a gamma ray tracking array: the spatial localization of the interactions (hits) and
their corresponding energetic release is basic information needed to reconstruct the
path of a γ-ray inside an HPGe detector and it constitutes indeed the input of any
tracking algorithm. Such information is encoded in the shape of the current pulse
given by the detector following the interaction of γ radiation; in order to extract the
spatial coordinates and energy of the γ ray interaction points specific PSA methods to
process the detector signals have to be developed. In this thesis is described the Pulse
Shape Analysis (PSA) process in highly segmented HPGe detectors for γ-ray tracking
and a PSA algorithm for the decomposition of net-charge signal (Recursive
Subtraction). The result of its extensive tests on simulated and real events are
presented. The experimental data, on which the algorithm has been tested, were
acquired during the in beam test of the MARS detector, performed at INFN Legnaro
laboratories in July 2001 and during the in beam test of the AGATA symmetric
cluster, performed at IKP Köln in August/September 2005.
Finally in this thesis will be presented three ideas to exploit PSA techniques for
applications that go also beyond the interaction localization (i.e. detector scan,
improvement of timing performances of the detector). The first results are very
encouraging but still there is the need for further development as will be pointed out
in more detail.
3
Lauer, Martin. "Digital signal processing for segmented HPGe detectors preprocessing algorithms and pulse shape analysis /." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972595910.
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Ferreira, Marcio Drumond Costa. "Estudo da eficiência de um detector HPGe por métodos semiempíricos e experimental." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2012. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=268.
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NenhumaA espectrometria gama é uma técnica que proporciona informações diversas em uma única análise, além de ser rápida e não destrutiva. Por meio de um detector de radiação acoplado a um sistema eletrônico de aquisição de dados, a técnica identifica os radionuclídeos emissores gama em uma amostra com radioatividade natural ou induzida, bem como fornece informações para calcular as suas atividades, a partir do registro e análise do espectro gama. A eficiência é um dos principais parâmetros a ser considerado quando se trabalha com detectores de radiação gama. Seu conhecimento possibilita uma melhor exatidão na quantidade de quantuns de radiação que o detector pode registrar dentre o total que emerge da fonte ou da amostra em estudo. A eficiência pode ser determinada experimentalmente, por métodos teóricos e semiempíricos. Usualmente, a determinação por método experimental é a mais exata, porém exige a aquisição de mais dados, o que torna o procedimento mais trabalhoso. Por sua vez, os métodos teóricos e os semiempíricos são muito menos laboriosos, apesar dos riscos de apresentarem maiores incertezas. Neste trabalho, foi realizado um estudo comparativo para verificar se as equações de eficiência determinadas por métodos semiempíricos e experimental teriam desempenhos similares na determinação das concentrações elementares da amostra de referência IAEA/Soil7, em geometria puntual e não puntual, irradiadas no reator de pesquisa TRIGA MARK I IPR-R1. Por métodos semiempíricos, foram aplicados os programas KayZero for Windows, V. 2.42 específico para cálculo de concentração elementar no método k0 de Ativação Neutrônica e o ANGLE V3.0 desenvolvido para cálculo de eficiência de detectores semicondutores para diversas geometrias. Os resultados indicaram, por meio de avaliação estatística, que as eficiências determinadas experimentalmente e por métodos semiempíricos são similares e igualmente eficazes tanto para a amostra puntual quanto para a não puntual. As diferenças observadas nos resultados das concentrações elementares foram relacionadas às correções aplicadas pelo programa e não consideradas quando se usa a planilha eletrônica e não devido às eficiências determinadas. Este estudo mostrou também que o programa KayZero for Windows analisa e considera como puntual amostras com massa cinco vezes maior que a massa das amostras usualmente analisadas, o que expande o campo de aplicação do programa.
Gamma spectrometry is a technique that provides a piece of information on a sample in one measurement, in a fast and non destructive assay. Such technique identifies gamma emitter radionuclides in natural and induced radioactivity, using a radiation detector linked to an electronic system in order to acquire the data and gamma spectra. To determine the full energy peak efficiency of High-Purity Germanium detector is important for gamma-ray spectrometry experiments. The efficiency of a detector is proportionality constant, which relates the activity of the source being counted and the number of counts observed. This efficiency can be determined applying experimental methods, using theoretical and semi empirical methods. Usually, the determination via an experimental procedure is more accurate, however, it is necessary more data acquisition that makes the procedure more tiring. On the other hand, the theoretical and semi empirical methods are less laborious procedures, despite the risks of higher uncertainties. This comparative study was carried out in order to verify whether the full energy peak efficiency curves determined by experimental and semi empirical methods, would present a similar performance on elemental concentration of reference material IAEA/Soil7, prepared in punctual and non-punctual geometries, and irradiated in the TRIGA MARK I IPR-R1 research reactor. It was applied were applied the KayZero for Windows, V. 2.42 a specific software for elemental concentration determination in the k0-stardadization neutron activation analysis - and ANGLE V3.0 specific method to determine semi conductor detectors gamma efficiencies for several sample geometries. Based on statistical tests u-score and Relative Tendency - the results pointed out for two types of sample geometries, the efficiencies determined experimentally and by semi empirical methods are similar, which were fitted well and worked properly. The deviations observed in the results were related to corrections made by the KayZero for Windows software and didnt apply when the values were calculated using the spread sheet and not related to the efficiency curves themselves. Additionally, it was evidenced that KayZero for Windows software is able to analyze a non-punctual sample, with mass 5 times higher that the usual size, as it were punctual. It points out the versatility of the software and expands the application field.
5
Descovich, Martina. "Improving the position resolution of highly segmented HPGe detectors using pulse shape analysis methods." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272634.
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6
Máduar, Marcelo Francis. "Desenvolvimento de um código computacional aberto de análise quantitativa para determinação de radionuclídeos por espectrometria gama com detectores semicondutores." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-12082011-150805/.
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A quantificação da atividade de radionuclídeos emissores de raios gama em amostras medidas por espectrometria gama com detectores HPGe depende da análise dos fotopicos presentes no espectro, especialmente da determinação exata das suas áreas líquidas. Tal análise é geralmente realizada com o auxílio de ferramentas de software proprietário. Este trabalho apresenta uma metodologia, descrição de algoritmos e um aplicativo de código aberto, denominado OpenGamma, para a busca e análise de fotopicos a fim de se obter seus parâmetros relevantes e as atividades dos radionuclídeos na amostra. A implementação computacional é distribuída sob licença aberta para o código principal e com o uso de pacotes de software aberto para o projeto da interface e para bibliotecas matemáticas. O procedimento para a busca de picos é realizado em três etapas. Primeiramente, executa-se uma pesquisa preliminar com o método da segunda diferença, que consiste na geração de um espectro derivado para a busca de picos candidatos. Na segunda etapa, calculam-se as larguras experimentais dos picos, dos quais escolhem-se aqueles bem formados e isolados para a obtenção da função de ajuste da largura vs. canal, por meio do método de Levenberg-Marquardt para ajustes não-lineares. Por fim, regiões do espectro com picos agrupados são delimitadas e novo ajuste não-linear é aplicado a cada região para a obtenção dos termos da linha de base e dos fotopicos. A partir destes termos, são calculadas as áreas líquidas dos picos. Para a determinação da atividade, curvas de calibração de eficiência previamente obtidas, bem como dados de transições gama dos radionuclídeos, são incorporadas ao código e aplicadas. O código foi escrito em linguagem C++ e a interface foi desenvolvida com a ferramenta Qt. Para as funções matemáticas e procedimentos de ajuste, foi usada a biblioteca científica GNU (GSL). A validação de código foi feita por meio da análise de: 1) espectros sintéticos de teste da AIEA, especialmente desenhados para a avaliação de desempenho de software; 2) espectros obtidos com amostras de exercícios de intercomparação e 3) espectros da rotina de trabalho do Laboratório de Radiometria Ambiental (LRA) do IPEN e analisados com o aplicativo comercial InterWinner. Os resultados obtidos são consistentes com os valores de referência e com aqueles obtidos pelo aplicativo citado, sugerindo que o código OpenGamma pode ser utilizado com segurança na espectrometria de raios gama de uso geral.Radioactivity quantification of gamma-ray emitter radionuclides in samples measured by HPGe gamma-ray spectrometry relies on the analysis of the photopeaks present in the spectra, especially on the accurate determination of their net areas. Such a task is usually performed with the aid of proprietary software tools. This work presents a methodology, algorithm descriptions and an open source application, called OpenGamma, for the peak search and analysis in order to obtain the relevant peaks parameters and radionuclides activities. The computational implementation is released entirely in open-source license for the main code and with the use of open software packages for interface design and mathematical libraries. The procedure for the peak search is performed on a three step approach. Firstly a preliminary search is done by using the second-difference method, consisting in the generation of a derived spectrum in order to find candidate peaks. In the second step, the experimental peaks widths are assessed and well formed and isolated ones are chosen to obtain a FWHM vs. channel relationship, by application of the Levenberg-Marquardt minimization method for non-linear fitting. Lastly, regions of the spectrum with grouped peaks are marked and a non-linear fit is again applied to each region to obtain baseline and photopeaks terms; from these terms, peaks net areas are then assessed. For the activity determination, previously obtained efficiency calibration curves, as well as nuclides gamma-ray data, are incorporated in the code and applied. The code was developed in C++ language and the interface was developed with Qt GUI software toolkit. GNU scientific library, GSL, was employed to perform fitting procedures as needed. Validation of code was done by analyzing: 1) synthetic test spectra from IAEA, especially designed for software performance evaluation; 2) spectra obtained from samples of intercomparison exercises and 3) spectra from routine activities of the Environmental Radiometric Laboratory (LRA) at IPEN and analyzed with the commercial software package InterWinner. Results obtained are consistent with the reference values and with those obtained by the aforementioned package. The results suggest that the OpenGamma code could be safely used in general-purpose gamma-ray spectrometry.
7
Damon, Raphael Wesley. "Determination of the photopeak detection efficiency of a HPGe detector, for volume sources, via Monte Carlo simulations." Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
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The Environmental Radioactivity Laboratory (ERL) at iThemba LABS undertakes experimental work using a high purity germanium (HPGe) detector for laboratory measurements. In this study the Monte Carlo transport code, MCNPX, which is a general-purpose Monte Carlo N &minusParticle code that extends the capabilities of the MCNP code, developed at the Los Alamos National Laboratory in New Mexico, was used. The study considers how various parameters such as (1) coincidence summing, (2) volume, (3) atomic number (Z) and (4) density, affects the absolute photopeak efficiency of the ERL&rsquo
s HPGe detector in a close geometry (Marinelli beaker) for soil, sand, KCl and liquid samples. The results from these simulations are presented here, together with an intercomparison exercise of two MC codes (MCNPX and a C++ program developed for this study) that determine the energy deposition of a point source in germanium spheres of radii 1 cm and 5 cm.
A sensitivity analysis on the effect of the detector dimensions (dead layer and core of detector crystal) on the photopeak detection efficiency in a liquid sample and the effect of moisture content on the photopeak detection efficiency in sand and soil samples, was also carried out. This study has shown evidence that the dead layer of the ERL HPGe detector may be larger than stated by the manufacturer, possibly due to warming up of the detector crystal. This would result in a decrease in the photopeak efficiency of up to 8 % if the dead layer of the crystal were doubled from its original size of 0.05 cm. This study shows the need for coincidence summing correction factors for the gamma lines (911.1 keV and 968.1 keV) in the 232Th series for determining accurate activity concentrations in environmental samples. For the liquid source the gamma lines, 121.8 keV, 244.7 keV, 444.1 keV and 1085.5 keV of the 152Eu series, together with the 1173.2 keV and 1332.5 keV gamma lines of the 60Co, are particularly prone to coincidence summing. In the investigation into the effects of density and volume on the photopeak efficiency for the KCl samples, it has been found that the simulated results are in good agreement with experimental data. For the range of sample densities that are dealt with by the ERL it has been found that the drop in photopeak efficiency is less than 5 %. This study shows that the uncertainty of the KCl sample activity measurement due to the effect of different filling volumes in a Marinelli beaker is estimated in the range of 0.6 % per mm and is not expected to vary appreciably with photon energy. In the case of the effect of filling height on the efficiency for the soil sample, it was found that there is a large discrepancy in the trends of the simulated and experimental curves. This discrepancy could be a result of the use of only one sand sample in this study and therefore the homogeneity of the sample has to be investigated. The effect of atomic number has been found to be negligible for the soil and sand compositions for energies above 400 keV, however if the composition of the heavy elements is not properly considered when simulating soil and sand samples, the effect of atomic number on the absolute photopeak efficiency in the low energy (<
400 keV) region can make a 14 % difference.
8
Zocca, F. "New technologies for low-noise wide-dynamic range preamplification of HPGe segmented detector signals." Doctoral thesis, Università degli Studi di Milano, 2008. http://hdl.handle.net/2434/60937.
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SANTOS, ROBERTO M. dos. "Desenvolvimento de um método para obtenção da eficiência de detecção para detectores HPGe em medidas com fontes extensas." reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10104.
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Lewandowski, Lars [Verfasser], Peter [Gutachter] Reiter, and Jan [Gutachter] Jolie. "Pulse-Shape Analysis and Position Resolution in highly segmented HPGe Detectors / Lars Lewandowski ; Gutachter: Peter Reiter, Jan Jolie." Köln : Universitäts- und Stadtbibliothek Köln, 2020. http://d-nb.info/1215293755/34.
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CARDOSO, VANDERLEI. "Metodos de ajuste de curvas de eficiencia obtidas por meio de espectrometros de HPGe." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11015.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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TAKEDA, MAURO N. "Determinacao da correcao para o efeito de soma em cascata para espectrometros de HPGe pelo metodo de Monte Carlo." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10916.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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SALA, ELENA. "Development of low level counting systems for high sensitivity measurements." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2014. http://hdl.handle.net/10281/52031.
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Low level counting techniques are a powerful tools in many different fields including biological and chemical tracer studies, archaeological and geological dating, investigation
of natural and induced radioactivities and the study of fundamental particles physics.
Since they play a crucial role in many applications, developments are continuously pursue to improve the extreme sensitivity typical of these techniques.
The fundamental request of low level counting techniques is the capability to detect feeble signals, characterized by low counting rates, above the background composed of spurious counts; they thus have the capability to measure very low activities of natural
and artificial radionuclides.
During my PhD work I have focused on two main applications using low level counting
systems: the search of rare physics events and the environmental monitoring.
Both the studied systems use γ spectroscopy with High Purity Germanium detectors
(HPGe).
This technique is one of the most sensitive, it exploits the excellent energy
resolution typical of such detectors and their low intrinsic background.
The first system is composed of two n-type HPGe GMX 100-95 in Low Background
configuration, they have been designed with radiopure selected materials to reach an
intrinsic background as low as possible. This work has brought to a unique configuration
associated to an electrical cooling system, different from the one that was available on
market. Since the two GMX detectors have been conceived to work in coincidence I
have optimized the measuring system studying different radionuclide decay schemes to
consider the most probable coincidences between the γ -rays emitted during the decay of
the isotope under study. A dedicated data acquisition has been developed with particular attention to the co-
incidence detection efficiency. Furthermore I have developed the analysis software to For some rare physics events experiments the only way to enhance the sensitivity is
the background reduction; for this purpose all the materials of the experimental facility
should be selected as radiopure as possible.
The development and optimization of the low background system composed of the
two GMX detectors, working in coincidence, can select suitable materials through the
measurement of very low radionuclide concentrations.
The other system I have worked on is a Broad Energy Germanium (BEGe5030) in
low background configuration. This detector can register with excellent energy resolution
and high efficiency a wide energy spectrum, from 3 keV up to 3 MeV, thanks to some of
its peculiar features. The thin dead layers surrounding the active volume and the thin
entrance window on its top are responsible for its capability to detect very low energy
radiations.
I have optimized this system using Monte Carlo simulations to detect low contamina-
tions of radionuclides in several samples.
In particular in the last century, the environmental monitoring has became an impor-
tant aspect of radio-protection; nuclear tests, nuclear accidents, wastes and fall-out in
general can release a large quantity of radionuclides. Since toxicity and radioactivity of
these contaminations are dangerous it is mandatory an environmental monitoring at the
area of interest.
Plutonium isotopes significantly contribute to the contamination due to nuclear fall-
out events in environment; since they are very toxic it is important to quickly monitor a
large number of samples in the area of interest.
Using the BEGe I have developed a quick and sensitive method to detect Plutonium
isotopes concentration in environmental samples through the detection of the X-rays emitted during their decays.
This result is a very important improvement in Plutonium detection for monitoring measurements since the counting methods commonly used are characterized by long measuring and sample treatments time.
14
De, Canditiis Bartolomeo. "3D characterization of multi-segmented HPGe detectors : simulation and validation of the PSCS technique and its application for different energies with a 152 Eu source." Thesis, Strasbourg, 2020. http://www.theses.fr/2020STRAE008.
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Les ensembles de détecteurs de rayon gamma de nouvelle génération, tel AGATA, utilisent des détecteurs multi-segmentés de germanium hyper-pur dans les expériences de physique nucléaire pour lesquelles une grande résolution et efficacité sont demandées. Ces caractéristiques sont obtenues par l’application des techniques d'analyse des formes d'impulsion et de tracking des rayons gamma. Ces dernières demandent une caractérisation volumétrique des détecteurs. À cet effet, l'IPHC a développé une table de scan qui utilise la technique Pulse Shape Comparison Scan (PSCS). Des simulations sont réalisées pour quantifier la précision de la technique PSCS et pour la valider. Elles sont appliquées sur un détecteur planaire pixelisé 3x3 et sur un détecteur symétrique d'AGATA de type S. La méthode est testée avec plusieurs énergies de rayons gamma et diverses statistiques d'entrée. Des scans réels sont aussi entrepris sur les deux détecteurs, qui sont totalement caractérisés. En particulier, un scan réalisé pour la première fois avec une source de rayons gamma de 152Eu, prouve la validité de certaines hypothèses sur lesquelles repose la technique de trackingNew generation gamma-ray detectors arrays, such as AGATA, employ multi-segmented high purity germanium detectors in experiments of nuclear physics that require high resolution and efficiency which are obtained thanks to the application of pulse-shape analysis and gamma-ray tracking. These techniques require full volume characterization of the position sensitive detectors. The IPHC developed a scanning table that uses the Pulse Shape Comparison Scan (PSCS) technique to perform this task. Simulations are performed to quantify the accuracy of the PSCS and to validate it.They are applied on a pixelated 3x3 planar detector and a symmetrical S-type AGATA detector. The method is tested with different gamma-ray energies and input statistics. Several real scans are performed as well on both detectors, which are fully characterized. In particular a scan with agamma-ray source of 152Eu, the first ever done, prove some assumptions on which the tracking technique is based
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Hernández, Suárez Francisco Javier. "Optimisation of environmental gamma spectrometry using Monte Carlo methods." Doctoral thesis, Uppsala University, Department of Physics, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-2672.
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Dissertation in Environmental Physics to be publicly examined in Häggsalen (Ångström Laboratory), Uppsala University, on Friday, November 8, 2002 at 10:00 am for the degree of doctor of philosophy in Physics. The examination will be conducted in English.
Gamma spectrometry is one of the tools commonly used for the measurement of various environmental radionuclides. Simultaneous determination of the absolute activity of gamma emitting radiotracers in a wide range of environmental matrices and fractions necessitates proper and accurate evaluation of the sample-to-detector efficiency. Several radiotracers require, in addition, the use of sub-routines for self-absorption corrections.
Gamma spectrometry is an important and elegant tool for assessing environmental changes. Optimisation of ultra low-level gamma spectrometry for reliable assessment of such changes requires harmonisation of laboratory needs with sampling and site conditions.
Different aspects of the calculation of sample-to-detector efficiencies using empirical and Monte Carlo approaches are discussed here, including the uncertainties related to the simulation of the performance of different HPGe detectors and the effects of the incomplete collection of charges in Ge-crystals. Various simulation codes for the computation of peak efficiencies in planar and well Ge-detectors have been developed from scratch. The results of the simulations have been tested against experimental data and compared to other simulation results obtained with the Monte Carlo N-Particle code (MCNP). The construction of calibration sources with improved absorption and collimation characteristics have been, also, described in this work. These sources have been especially designed for the efficiency calibration of Ge-detectors at energies below 100 keV.
Flexible, fully tested and prototype approaches for the evaluation of self-absorption corrections, based on Monte Carlo simulations, are described. Special consideration is given to the problems related to the sample's variability in size, density and composition. Several examples of the absolute and simultaneous determination of environmental multitracers which benefited from self-absorption corrections and the optimised efficiency calibration algorithms are, also, presented and discussed. These examples include, among other things, a comprehensive analysis of the gamma spectrometry of 234Th in a wide range of matrices and the speciation of several radionuclides in sediments from a hard-water lake.
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Söderström, Pär-Anders. "Collective Structure of Neutron-Rich Rare-Earth Nuclei and Development of Instrumentation for Gamma-Ray Spectroscopy." Doctoral thesis, Uppsala universitet, Kärnfysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-149772.
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Neutron-rich rare-earth nuclei are among the most collective nuclei that can be found in nature. In particular, the doubly mid-shell nucleus 170Dy is expected to be the nucleus where the collective structure is maximized. This has implications for the astrophysical r-process, since it has been suggested that the collectivity maximum plays an important role in the abundances of the rare-earth elements that are created in supernova explosions. In this work, the collective structure of the five nuclei 168,170Dy and 167,168,169Ho are studied and different theoretical models are used to interpret the evolution of collectivity around the mid-shell. In order to produce and study even more neutron-rich nuclei in this mass region, new radioactive ion beam facilities will be a valuable tool. These facilities, however, require advanced instruments to study the weak signals of exotic nuclei in a high background environment. Two of these instruments are the γ-ray tracking spectrometer AGATA and the neutron detector array NEDA. For AGATA to work satisfactorily, the interaction position of the gamma rays must be determined with an accuracy of at least five millimetres. The position resolution is measured in this work using a model independent method based on the Doppler correction capabilities of the detector at two different distances between the detector and the source. For NEDA, one of the critical parameters is its ability to discriminate between neutrons and γ rays. By using digital electronics it is possible to employ advanced and efficient algorithms for pulse-shape discrimination. In this work, digital versions of the common analogue methods are shownto give as good, or better, results compared to the ones obtained using analogue electronics. Another method which effectively distinguishes between neutrons and γ rays is based on artificial neural networks. This method is also investigated in this work and is shown to yield even better results.
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Turk, Gerardus Henricus Bernardus. "The characterisation of the first SmartPET HPGe planar detector." Thesis, University of Liverpool, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428209.
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William, Lindberg. "Characterization of an HPGe detector for experiments on radioactive mushrooms." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355116.
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The purpose of this thesis is to assemble an HPGe detector intended to be used in a mass experiment during the autumn of 2018. After assembly, the detector will be characterized and a shielding, consisting of approximately two tons of lead, will be assembled around the detector. Different modules will be tested to find the optimal energy resolution possible for the planned measurements. To characterize the detector several measurements will be taken at different measurement geometries. Measurements of the background radiations will be performed before and after the assembly of the lead shielding such that a comparison of the shielding's effect on measurements can be made. These measurements will also be analyzed in an attempt to identify the different radionuclides contributing to the background radiation. The result was a reliable set-up with a good energy resolution. However, more tests are required to gain a greater understanding of the inner structure of the detector.
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Yilmaz, Ercan. "Characteristic X-ray, Photoelectron And Compton-scattered Photon Escape From A Hpge Detector." Phd thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/3/1210061/index.pdf.
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Escape of photoelectrons, Compton-scattered photons and Ge X-rays from a HPGe detector was studied as a function of energy in the range 8-52 keV. A variable-energy source producing Cu, Rb, Mo, Ag, Ba, and Tb X-rays was used. All three mechanisms for energy loss were observed in the same experiment for Ba and Tb, while only X-ray and photoelectron escapes were evident in the spectra for Ag, Mo, Rb, and Cu. Spectral features and possible mechanisms for partial energy deposition were investigated. A Monte Carlo program was used to simulate the relevant interactions and to estimate the escape probabilities.
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Santos, Roberto Manuel dos. "Desenvolvimento de um método para obtenção da eficiência de detecção para detectores HPGe em medidas com fontes extensas." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-24082012-162508/.
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Um dos grandes desafios em medidas de espectrometria gama utilizando fontes que não podem ser consideradas pontuais é a determinação da eficiência de detecção do sistema, uma vez que a geometria da fonte impõe complexidades na tarefa como o tratamento do ângulo sólido e da auto-absorção. Alguns métodos para o cálculo dessa eficiência já são bem estabelecidos e podem ser encontrados na literatura. Neste trabalho é proposto um método com características distintas aos já existentes cujas principais vantagens são, não depender de conhecimento prévio da geometria de detecção e da composição química da amostra a ser medida, e permitir o cálculo da eficiência de uma fonte extensa a partir de medidas com fontes padrão em formato pontual. O método proposto foi testado comparando os valores das eficiências obtidas por ele com os valores obtidos usando uma fonte padrão extensa. Para testar o método proposto em diferentes condições foi utilizado solo como matriz para a amostra em duas diferentes espessuras, 1cm e 3cm. Testou-se também o comportamento do método quando a matriz tem número atômico efetivo mais alto (aqui utilizou-se solo misturado à limalha de ferro) e mais baixo (adição de pó de grafite ao solo). Os resultados indicaram que o método é adequado para amostras de solo com espessura mais fina; já para fontes mais espessas, dois dos três resultados indicaram que a eficiência foi subestimada pelo método proposto, sugerindo que uma geometria mais adequada deva ser escolhida para a amostragem das medidasOne of the greatest challenges in gamma spectroscopy measurements using extense sources is the determination of the system\'s detection efficiency, since the source\'s geometry leads to added complexity to the treatment of parameters as geometry and self-absorption. Some well-established methods for the efficiency determination can be found in the literature. In the present work a method with distinct characteristics is proposed with the main advantages that it doesn\'t require previous knowledge of the detection geometry or of the sample composition; moreover, it allows the determination of the detection efficiency for a large sample based only on measurements using a point-like standard source. The proposed method was tested comparing the efficiency values obtained using the method with the values obtained using a real large source with the same composition and geometry. In order to verify the performance of the method under different conditions, soil matrixes of two different thicknesses (1cm and 3cm) were used; also, to asses the method under different sample compositions, 3cm-thick soil matrixes with increased effective atomic number (where iron filings was added) and with reduced effective atomic mass (where graphite powder was added) were used. The results indicate that the proposed method is suitable for thinner soil samples; as for thicker samples, two of the three results showed a subestimation of the detection efficiency value determined, suggesting that a more suitable sampling geometry should be analyzed.
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KANDEL, BENJAMIN. "Etude du plan de detection du spectrometre spi sur integral : analyse experimentale et modelisation des detecteurs hpge." Toulouse 3, 1998. http://www.theses.fr/1998TOU30257.
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Integral, projet de telescope spatial de l'agence spatiale europeenne, est destine a l'observation des emissions x et gamma d'origine astrophysique. Il associe les performances d'un imageur et d'un spectrometre. Le spectrometre spi s'appuie sur la haute resolution fournie par 19 detecteurs en germanium ultra pur de type n. Nous presentons les essais effectues sur 12 detecteurs des series prototype et modele d'etude de spi en vue de la qualification des modeles de vol et de la preparation des calibrations. Nous synthetisons les resultats obtenus en termes de resolution et d'efficacite sur toute la gamme d'energie couverte par spi (20 kev 8 mev), et analysons l'influence de la tension de polarisation et de la temperature de fonctionnement. Des simulations de type monte-carlo, basees sur les modules geant du cern, realisees en parallele avec les essais, sont confrontees systematiquement aux mesures et font l'objet d'une etude detaillee. Un ensemble de tests : vibrations, cycles thermiques, irradiations par des particules energetiques, a permis de qualifier les detecteurs et d'etudier leur comportement dans les conditions de vol. Notamment, 9 detecteurs ont ete irradies au cours de 6 campagnes avec des faisceaux de neutrons d'energies differentes, de 5 a 70 mev. Ces campagnes ont permis d'evaluer la degradation des performances des detecteurs en fonction de la dose recue, de l'energie des neutrons incidents et de la temperature de fonctionnement. Finalement, nous exploitons le code de simulation developpe pour modeliser les detecteurs. Les caracteristiques d'un ensemble de 19 detecteurs associes selon la configuration du plan de detection de spi sont analysees. Nous nous attachons plus particulierement a l'etude des evenements multiples et a leur influence sur la reponse spectrale et spatiale de la camera.
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Zschocke, Andreas [Verfasser]. "Analysis and evaluation of the pulse shape performance of an Inverted Coaxial HPGe detector for 0νββ Experiments / Andreas Zschocke." Tübingen : Universitätsbibliothek Tübingen, 2021. http://d-nb.info/1228858292/34.
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Marzocchi, Olaf <1982>. "Design and Setup of a New HPGe Detector Based Body Counter Capable of Detecting Also Low Energy Photon Emitters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3929/1/Marzocchi_Olaf_tesi.pdf.
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The present work describes the development of a new body-counter system based on HPGe detectors and installed at IVM of KIT. The goal, achieved, was the improvement of the ability to detect internal contaminations in the human body, especially the ones concerning low-energy emitters and multiple nuclides. The development of the system started with the characterisation of detectors purchased for this specific task, with the optimisation of the different desired measurement configurations following and ending with the installation and check of the results. A new software has been developed to handle the new detectors.Il presente lavoro descrive lo sviluppo del nuovo sistema di conteggio basato su rivelatori HPGe installato presso l'IVM situato al KIT. L'obiettivo, raggiunto, era quello di migliorare la capacità di rilevazione di contaminazioni interne del corpo umano, specialmente di quelle inerenti basse energie e quelle contenenti nuclidi multipli. La progettazione del sistema è stata effettuata ex-novo, a partire dalla caratterizzazione dei rivelatori acquistati per l'uopo, proseguendo con l'ottimizzazione delle diverse configurazioni di misura richieste e terminando con l'installazione e la verifica dei risultati. Parallelamente è stato sviluppato un software per gestire i nuovi rivelatori.
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Marzocchi, Olaf <1982>. "Design and Setup of a New HPGe Detector Based Body Counter Capable of Detecting Also Low Energy Photon Emitters." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3929/.
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The present work describes the development of a new body-counter system based on HPGe detectors and installed at IVM of KIT. The goal, achieved, was the improvement of the ability to detect internal contaminations in the human body, especially the ones concerning low-energy emitters and multiple nuclides. The development of the system started with the characterisation of detectors purchased for this specific task, with the optimisation of the different desired measurement configurations following and ending with the installation and check of the results. A new software has been developed to handle the new detectors.Il presente lavoro descrive lo sviluppo del nuovo sistema di conteggio basato su rivelatori HPGe installato presso l'IVM situato al KIT. L'obiettivo, raggiunto, era quello di migliorare la capacità di rilevazione di contaminazioni interne del corpo umano, specialmente di quelle inerenti basse energie e quelle contenenti nuclidi multipli. La progettazione del sistema è stata effettuata ex-novo, a partire dalla caratterizzazione dei rivelatori acquistati per l'uopo, proseguendo con l'ottimizzazione delle diverse configurazioni di misura richieste e terminando con l'installazione e la verifica dei risultati. Parallelamente è stato sviluppato un software per gestire i nuovi rivelatori.
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Pekoz, Rengin. "Components Of Detector Response Function: Experiment And Monte Carlo Simulations." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605228/index.pdf.
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Components of the response function of a high-purity germanium (HPGe) detector due to full or partial energy deposition by gamma- and X-rays were studied. Experimental response functions for 241Am, Ba and Tb were compared with those obtained from the Monte Carlo simulations. The role of physical mechanisms for each component was investigated by considering escape/absorption of photons, photoelectrons, Auger electrons, recoil electrons and X-rays of the detector material. A detailed comparison of the experimental Compton, photoelectron, detector X-ray escape components and full-energy peaks with those obtained from Monte Carlo program are presented.
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Ordóñez, Ródenas José. "Desarrollo de Modelos de Simulación por Monte Carlo como Apoyo a la Medida de Radiactividad Ambiental en Operación Rutinaria y de Emergencias." Doctoral thesis, Universitat Politècnica de València, 2020. http://hdl.handle.net/10251/152188.
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[ES] En el apoyo a la mejora de la calidad de medida en el Laboratorio de Radiactividad Ambiental (LRA) de la Universitat Politècnica de València (UPV), los códigos de Monte Carlo representan una potente herramienta para complementar las tareas relacionadas con la medida de la radiactividad ambiental, tales como la calibración en eficiencia de detectores de semiconductor, determinación de factores de corrección por coincidencia y caracterización de dosímetros de termoluminiscencia, entre otras.
En la presente Tesis se desarrollan modelos de simulación en Monte Carlo a través de códigos y herramientas como MCNP6 y GEANT4. En primer lugar, se han realizado dos modelos de detector de semiconductor para espectrometría gamma, uno tipo HPGe (High Purity Germanium) y el otro BEGe (Broad Energy Germanium), ambos de alta pureza de germanio. Ambos detectores se emplean en las actividades y procedimientos rutinarios que se realizan en el LRA-UPV. Se detalla el procedimiento de caracterización geométrica de los detectores de semiconductor, así como del volumen activo del cristal de germanio hasta obtener un modelo geométrico optimizado.
Por otro lado, se ha obtenido un tercer modelo de simulación, pero en este caso de un dosímetro de termoluminiscencia, en concreto de un TLD-100 LiF:Mg,Ti, modelo que se emplea en el servicio de dosimetría personal de la UPV. En el modelo de simulación se incluye una fuente puntual colimada de Rayos-X y el fantoma recomendado por la ISO 4037-3 (water slab phantom). Se obtiene la función de respuesta del dosímetro relativa a la energía del 137Cs y se estudia su comportamiento para diferentes condiciones de irradiación (calidad del haz de Rayos-X y ángulo de incidencia) así como para diversos materiales termoluminiscentes además del LiF.
Los modelos de simulación para espectrometría gamma se han utilizado principalmente para la obtención de curvas de calibración en eficiencia para diferentes geometrías y matrices de medición, así como para el cálculo de factores de corrección por pico suma tanto para las series naturales del 238U y 232Th como para radioisótopos específicos empleados en la calibración experimental de los equipos.
Por otro lado, se han aplicado los modelos de simulación en el contexto de respuesta en emergencias nucleares o radiológicas. En concreto, el modelo del detector BEGe se ha utilizado para desarrollar una metodología de optimización del proceso de medición de muestras radiactivas en matrices de agua de alta actividad. Esta metodología consiste en un procedimiento logístico que incluye un cribado o screening de emergencias soportado por simulaciones Monte Carlo, enfocado en elegir la configuración óptima de medición para obtener resultados fiables y precisos minimizando la manipulación de la muestra radiactiva. De este modo se reduce el tiempo de respuesta por parte del laboratorio, así como el riesgo de contaminación y exposición a dosis.[EN] In support of the improvement of measurement quality at the Laboratorio de Radiactividad Ambiental (LRA) of the Universitat Politècnica de València (UPV), the Monte Carlo codes represent a powerful tool to complement the tasks related to the measurement of environmental radioactivity, such as the calibration in efficiency of semiconductor detectors, determination of coincidence summing correction factors and characterization of thermoluminescence dosimeters, among others. In the present thesis, Monte Carlo simulation models are developed using the MCNP6 code and the GEANT4 toolkit. Two semiconductor detector models for gamma spectrometry have been made, one type HPGe (High Purity Germanium) and the other one a BEGe (Broad Energy Germanium), both of high purity germanium. Both detectors are used in the routine activities and procedures carried out by the LRA-UPV. The geometric characterization procedure of the semiconductor detectors is detailed, as well as the active volume of the germanium crystal until an optimized geometric model is obtained. On the other hand, a third simulation model has been developed, but in this case from a thermoluminescence dosimeter, specifically from a TLD-100 LiF:Mg,Ti, a model used in the personal dosimetry service for the monitoring and assessment of the professionally exposed workers belonging to the UPV radioactive facility. The simulation model includes a collimated X-ray point source and the phantom recommended by the ISO 4037-3 (water slab phantom). The response function of the dosimeter relative to the energy of 137Cs is obtained and its behaviour is studied for different irradiation conditions (quality of the X-ray beam and angle of incidence) as well as for several thermoluminescent materials in addition to the LiF. The simulation models for gamma spectrometry have been used mainly to obtain efficiency calibration curves for different geometries and measurement matrices and to calculate true summing correction factors for both the 238U and 232Th natural decay series and for specific radioisotopes used in the experimental calibration of the equipment. On the other hand, simulation models have been applied in the context of nuclear or radiological emergency response. Specifically, the BEGe detector model has been used to develop a methodology for optimisation of the process of measuring radioactive samples in water matrices of high activity. This methodology consists of a logistic procedure that includes a screening for emergencies. This procedure is supported by Monte Carlo simulations, focused on determining the optimal measurement configuration to obtain reliable and accurate results, minimizing the manipulation of the radioactive sample. Therefore, the response time by the laboratory is reduced, as well as the risk of contamination and dose exposure.
[CA] En el suport a la millora de la qualitat de mesura en el Laboratori de Radioactivitat Ambiental de la Universitat Politècnica de València, els codis de Monte Carlo representen una potent eina per a complementar les tasques relacionades amb la mesura de la radioactivitat ambiental, com ara el calibratge en eficiència de detectors de semiconductor, determinació de factors de correcció per coincidència i caracterització de dosímetres de termoluminescència, entre altres. En la present tesi es desenvolupen models de simulació en Monte Carlo a través de codis i eines com MCNP6 i GEANT4. En primer lloc s'han realitzat dos models de detector de semiconductor per a espectrometria gamma, un tipus HPGe (High Purity Germanium) i l'altre BEGe (Broad Energy Germanium), tots dos d'alta puresa de germani. Aquests detectors s'empren en les activitats i procediments rutinaris que es realitzen en el Laboratori de Radioactivitat Ambiental (LRA) de la Universitat Politècnica de València (UPV). Es detalla el procediment de caracterització geomètrica dels detectors de semiconductor, així com del volum actiu del cristall de germani fins a obtindre un model geomètric optimitzat. D'altra banda, s'ha obtingut un tercer model de simulació, però en aquest cas d'un dosímetre de termoluminescència, en concret d'un TLD-100 LiF:Mg,Ti, model que s'empra en el servei de dosimetria personal de la UPV. En el model de simulació s'inclou una font puntual col·limada de Raigs-X i el fantoma recomanat per l'ISO 4037-3 (water slab phantom). S'obté la funció de resposta del dosímetre relativa a l'energia del 137Cs i s'estudia el seu comportament per a diferents condicions d'irradiació (qualitat del feix de Raigs-X i angle d'incidència) així com per a diversos materials termoluminescents a més del LiF. Els models de simulació per a espectrometria gamma s'han utilitzat principalment per a l'obtenció de corbes de calibratge en eficiència per a diferents geometries i matrius de mesurament així com per al càlcul de factors de correcció per pic suma tant per a les sèries naturals del 238U i 232*Th com per a radioisòtops específics utilitzats en el calibratge experimental dels equips. D'altra banda, s'han aplicat els models de simulació en el context de resposta en emergències nuclears o radiològiques. En concret, el model del detector BEGe s'ha utilitzat per a desenvolupar una metodologia d'optimització del procés de mesurament de mostres ambientals radioactives en matrius d'aigua d'alta activitat.. Aquesta metodologia consisteix en un procediment logístic que inclou un screening o cribratge d'emergències, suportat per simulacions Monte Carlo, enfocat a triar la configuració òptima de mesurament per a obtindre resultats fiables i precisos minimitzant la manipulació de la mostra radioactiva. D'aquesta manera es redueix el temps de resposta per part del laboratori, així com el risc de contaminació i exposició a dosi.
Finalmente, a la Universitat Politècnica de València por la financiación a través de la beca de Formación de Personal Investigador (FPI)-Subprograma 2 de la convocatoria de 2015 y a la Cátedra CSN-UPV Vicente Serradell
Ordóñez Ródenas, J. (2020). Desarrollo de Modelos de Simulación por Monte Carlo como Apoyo a la Medida de Radiactividad Ambiental en Operación Rutinaria y de Emergencias [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/152188
TESIS
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Mubashir, Hassan. "Installation and optimization of a gamma spectrometry system in anticoincidence." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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The work covered by this thesis was carried out at the Brasimone ENEA Research Centre, the National Agency for New Technologies, Energy and Sustainable Economic Development, with the aim of optimising a gamma spectrometry system in anticoincidence for the detection of noble gases, in particular the radioactive isotopes of xenon 131mXe, 133Xe, 133mXe and 135Xe.
The laboratory of the ENEA Research Center of Brasimone, where the experimental apparatus is found to carry out the measurements of 131mXe, 133Xe, 133mXe and 135Xe, collaborates constantly with the monitoring network and is able to provide, if necessary, data and analysis on noble gases.
The signals produced by the interaction of cosmic rays that manage to pass the screen have been recognized as the main cause of the increase of the detector background because they give rise to the Compton continuum and, as a result, they increase the value of detectable MDA.
For this reason, a system in anticoincidence has been developed through the use of two plastic scintillators, placed over the shielding of the Hpge detector, which sends pulses recording within a gate located in the germanium multichannel analyzer: at the time the signal arrives from the scintillator, the gate blocks data acquisition to avoid recording pulses generated by cosmic radiation.
For both configurations of the system, therefore, both with the anti-coincidence apparatus inactive and in operation, energy, FWHM and efficiency calibrations had to be carried out using a certified multi-peak source.
The solution proposed, in conclusion of the thesis, to eliminate any electronic interference with the efficiency of the detector provides for the replacement of the current electronic apparatus with a new fully digitized, made by the company CAEN, Nuclear Electronic Construction Equipment.
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Bäckström, William. "Dating lake bottom sediment by searching for 210Pb using gamma-ray spectroscopy." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-416601.
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In a collaboration with limnologists at Uppsala University a planar HPGe detector has been used to find 210Pb in lake bottom sediment in hopes of getting an estimation for the sedimentation rate. Using a least squares fit to the data, the sedimentation rate was calculated to 0.08 ± 0.01 cm/year with background subtraction, and with it a timescale for the age of the sediment could be implemented. With this timescale the lake bottom sediment can be dated as far back as a century. Along with this, using 137Cs traces from the Chernobyl disaster of 1986 a consistency check can be made for our timescale. It is estimated that the Chernobyl disaster occurred at 1989 ± 7 years which is consistent with reality since 1986 is included in the interval 1982-1989. This helps us validate the determined sedimentation rates.
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Jovana, Knežević. "Коинцидентне методе за анализу временских карактеристика нуклеарних процеса." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2020. https://www.cris.uns.ac.rs/record.jsf?recordId=114886&source=NDLTD&language=en.
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У докторској дисертацији приказани су резултати развијених и примењених коинцидентних метода за временску анализу нуклеарних процеса. Експериментални коинцидентни системи засновани су на HPGe и пластичним сцинтилационим детекторима. Извршена су три експеримента, која су показала примењивост развијених коинцидентних система. Први део експерименталног дела обухвата анализе временских варијација интензитета космичког зрачења посредством нискоенергијских фотона. Показано је да се праћењем интензитета нискоенергијских фотона у току времена у различитим енергијским регионима остварује бољи увид у анализу фонских догађаја, стварајући предуслове за извођење експеримената који трагају за ретким нуклеарним процесима. Поред праћења временских варијација интензитета, метода се може применити и на детекцију периодичних и апериодичних догађаја повезаних са активношћу Сунца. Други део дисертације обухватао је истраживања везана за детекцију потенцијалних флуктуација константе распада 22 Na. Развијен је коинцидентни систем и у току времена је праћен интензитет анихилационе линије, која је резултат анихилације позитрона емитованог распадом 22Na. За време трајања аквизиције података, нису пронађена значајна одступања испитиване константе распада од стандардног експоненцијалног закона радиоактивног распада. У трећем делу експерименталног рада, приказана је коинцидентна метода за временско раздвајање догађаја индукованих мионима и неутронима у околини детекторског система. Добијена је временска крива у експерименту и извршена је детаљна анализа различитих временских региона. Извршене су Монте Карло симулације, на основу којих је добијена временска крива. Анализом различитих региона симулиране временске криве, показано је да се ови догађаји могу раздвојити у две велике групе–брзе и споре догађаје. Међу спорим догађајима, показано је да се може направити разлика између догађаја индукованих мионима, међу којима доминира анихилација, и догађаја индукованих неутронима, који спадају у закаснеле догађаје у групи спорих догађаја. Добијено је да неутрони највише доприносе нискоенергијском региону, првенствено у региону до ≈50 keV, што их чини нежељеном кариком фонских догађаја у експериментима који трагају за ретким нуклеарним догађајима. На основу резултата симулација, анализирани су електромагнетни и хадронски процеси индуковани мионима и неутронима, као и удели мионске и неутронске компоненте у коинцидентном спектру HPGe детектора и директном спектру пластичног сцинтилационог детектора. Закључено је да нискоенергијском спектру, који је превасходно значајан за ретке нуклеарне процесе, доминантно доприносе неутрони.U doktorskoj disertaciji prikazani su rezultati razvijenih i primenjenih koincidentnih metoda za vremensku analizu nuklearnih procesa. Eksperimentalni koincidentni sistemi zasnovani su na HPGe i plastičnim scintilacionim detektorima. Izvršena su tri eksperimenta, koja su pokazala primenjivost razvijenih koincidentnih sistema. Prvi deo eksperimentalnog dela obuhvata analize vremenskih varijacija intenziteta kosmičkog zračenja posredstvom niskoenergijskih fotona. Pokazano je da se praćenjem intenziteta niskoenergijskih fotona u toku vremena u različitim energijskim regionima ostvaruje bolji uvid u analizu fonskih događaja, stvarajući preduslove za izvođenje eksperimenata koji tragaju za retkim nuklearnim procesima. Pored praćenja vremenskih varijacija intenziteta, metoda se može primeniti i na detekciju periodičnih i aperiodičnih događaja povezanih sa aktivnošću Sunca. Drugi deo disertacije obuhvatao je istraživanja vezana za detekciju potencijalnih fluktuacija konstante raspada 22 Na. Razvijen je koincidentni sistem i u toku vremena je praćen intenzitet anihilacione linije, koja je rezultat anihilacije pozitrona emitovanog raspadom 22Na. Za vreme trajanja akvizicije podataka, nisu pronađena značajna odstupanja ispitivane konstante raspada od standardnog eksponencijalnog zakona radioaktivnog raspada. U trećem delu eksperimentalnog rada, prikazana je koincidentna metoda za vremensko razdvajanje događaja indukovanih mionima i neutronima u okolini detektorskog sistema. Dobijena je vremenska kriva u eksperimentu i izvršena je detaljna analiza različitih vremenskih regiona. Izvršene su Monte Karlo simulacije, na osnovu kojih je dobijena vremenska kriva. Analizom različitih regiona simulirane vremenske krive, pokazano je da se ovi događaji mogu razdvojiti u dve velike grupe–brze i spore događaje. Među sporim događajima, pokazano je da se može napraviti razlika između događaja indukovanih mionima, među kojima dominira anihilacija, i događaja indukovanih neutronima, koji spadaju u zakasnele događaje u grupi sporih događaja. Dobijeno je da neutroni najviše doprinose niskoenergijskom regionu, prvenstveno u regionu do ≈50 keV, što ih čini neželjenom karikom fonskih događaja u eksperimentima koji tragaju za retkim nuklearnim događajima. Na osnovu rezultata simulacija, analizirani su elektromagnetni i hadronski procesi indukovani mionima i neutronima, kao i udeli mionske i neutronske komponente u koincidentnom spektru HPGe detektora i direktnom spektru plastičnog scintilacionog detektora. Zaključeno je da niskoenergijskom spektru, koji je prevashodno značajan za retke nuklearne procese, dominantno doprinose neutroni.
In this doctoral thesis, the results of the developed and applied coincidence methods on the timeanalysis of nuclear processes are presented. Coincidence systems, used in presented experiments, are based on the HPGe and plastic scintillation detectors. Three experiments were performed,showing a wide application of the developed coincidence systems. The first part of the experimental work involves the analysis of the time variations of cosmic rays via low-energy photons. It was shown that by analyzing the intensity of lowenergy photons better insight into the behavior of thebackground events is provided, which is especially important as a precondition for rare nuclear events experiments. Furthermore, it was shown that this method can be applied in order to search for periodic or aperiodic events resulting from the Sun activity. The second part contains the research of the 22Na decay constant fluctuations. The coincidence system was developed and the intensity of the annihilation line, resulting from annihilation of the positrons emitted from 22Na, was followed with time. During he acquisition time, no significant deviations from the standard exponential radioactive decay law were found. In the third part of the experimental work, the coincidence method for time separation of the events, induced by cosmic muons and neutrons in the vicinity of the detectors system, was presented. The time curve was obtained in the experiment and the detailed analysis of the different time regions was performed. The Monte Carlo simulations were conducted and the time curve from the simulation results was obtained. Analyzing the different regions of the simulated time curve, it was noticed that these events can be separated into two groups–prompt and delayed. Between delayed events, it was concluded that events induced by muons, dominantly annihilation line, and events induced by neutrons, which may be classified as more delayed events in the group of the delayed events, can be distinguished. It was concluded the neutrons dominantly contribute to the low-energy region, mostly in the region to ≈50 keV, which makes neutrons an important background in the experiments searching for rare nuclear events. Based on the simulation results, electromagnetic and hadronic processes induced by muons and neutrons, as well as portions of muon’s and neutron’s component in the coincidence spectrum of HPGe detector and direct spectrum of the plastic scintillation detector were analyzed. It was concluded that in the low-energy part of the spectrum, primarily important for the search for rare nuclear events, dominant influence is originated from cosmic neutrons.
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XHIXHA, Gerti. "Advanced gamma-ray spectrometry for environmental radioactivity monitoring." Doctoral thesis, Università degli studi di Ferrara, 2012. http://hdl.handle.net/11392/2388782.
Full textAbstract:
The environmental radioactivity monitoring programs start in the late 1950s of the 20th century following the global fallout from testing of nuclear weapons in the atmosphere, becoming a cause of concern regarding health effects. Later, the necessity of world industrialization for new energy sources led to develop national plans on electricity production from nuclear technology, initializing in this context world wide exploration for fuel minerals: uranium exploration gained a particular attention in late 1940's in USA, Canada and former USSR and in 1951 in Australia with respective national plans. Nowadays there are about 440 nuclear power plants for electricity generation with about 70 more NPP under construction giving rise to the nuclear emergency preparedness of a large number of states (like Radioactivity Environmental Monitoring (REM) data bank and EUropean Radiological Data Exchange Platform (EURDEP). Furthermore, a lot of applications in the field of geosciences are related to the environmental radioactivity measurements going from geological mapping, mineral exploration, geochemical database construction to heat -flow studies.
Gamma-ray spectroscopy technique is widely used when dealing with environmental radioactivity monitoring programs. The purpose of this work is to investigate the potentialities that such a technique offers in monitoring radioactivity concentration through three different interventions in laboratory, in-situ and airborne measurements. An advanced handling of gamma-ray spectrometry method is realized by improving the performances of instruments and realizing and testing dedicated equipments able to deal with practical problems of radioactivity monitoring. For each of these gamma-ray spectrometry methods are faced also the problems of calibration, designing of monitoring plans and data analyzing and processing.
In the first chapter I give a general description for the common radionuclides present in the environment having a particular interest for monitoring programs. Three categories of environmental radionuclides classified according to their origin as cosmogenic, primordial and man-made are discussed. The cosmic rays continuously produce radionulides and also direct radiation, principally high energetic muons. Cosmogenic radionuclides are originated from the interaction of cosmic rays with stable nuclides present in the Earth’s atmosphere. Primordial radionuclides are associated with the phenomenon of nucleosynthesis of the stars and are present in the Earth’s crust. Man-made radionuclides commonly present in natural environments are principally derived from radioactive fallout from atmospheric nuclear weapons testing and peaceful applications of nuclear technology like nuclear power plants for electricity generation and the associated nuclear fuel cycle facilities. A relevant contribution, generally with local implication comes from the so called non-nuclear industries which are responsible for technologically enhancement of natural radioelements producing huge amounts of naturally occurring radioactive materials (NORM/TENORM).
In the second chapter is described a homemade approach to the solution of the problem rising in monitoring situations in which a high number of samples is to be measured through gamma-ray spectrometry with HPGe detectors. Indeed, in such cases the costs sustaining the manpower involved in such programs becomes relevant to the laboratory budget and sometimes becomes a limitation of their capacities. Manufacturers like ORTEC® and CANBERRA produce gamma-ray spectrometers supported by special automatic sample changers which can process some tens of samples without any human attendance. However, more improvements can be done to such systems in shielding design and detection efficiency.
We developed a fully automated gamma-ray spectrometer system using two coupled HPGe detectors, which is a well known method used to increase the detection efficiency. An alternative approach on shielding design and sample changer automation was realized. The utilization of two coupled HPGe detectors permits to achieve good statistical accuracies in shorter time, which contributes in drastically reducing costs and man power involved. A detailed description of the characterization of absolute full-energy peak efficiency of such instrument is reported here. Finally, the gamma-ray spectrometry system, called MCA_Rad, was used to characterize the natural radioactivity concentration of bed-rocks in Tuscany Region, Italy. More than 800 samples are measured and reported here together with the potential radioactivity concentration map of bed rocks in Tuscany Region.
In the third chapter is described the application of portable scintillation gamma -ray spectrometers for in-situ monitoring programs focusing on the problems of calibration and spectrum analysis method. In-situ γ-ray spectrometry with sodium iodide scintillators is a well developed and consolidated method for radioactive survey. Conventionally, a series of self-constructed calibration pads prevalently enriched with one of the radioelements is used to calibrate this portable instrument. This method was further developed by introducing the stripping (or window analysis) described in International Atomic Energy Agency (IAEA) guidelines as a standard methods for natural radioelement exploration and mapping.
We realized a portable instrument using scintillation gamma-ray spectrometers with sodium iodide detector. An alternative calibration method using instead well-characterized natural sites, which show a prevalent concentration of one of the radioelements, is developed. This procedure supported by further development of the full spectrum analysis (FSA) method implemented in the non-negative least square (NNLS) constrain was applied for the first time in the calibration and in the spectrum analysis. This new approach permits to avoid artifacts and non physical results in the FSA analysis related with the χ2 minimization process. It also reduces the statistical uncertainty, by minimizing time and costs, and allows to easily analyze more radioisotopes other than the natural ones. Indeed, as an example of the potentialities of such a method 137Cs isotopes has been implemented in the analysis. Finally, this method has been tested by acquiring gamma Ombrone -ray spectra using a 10.16 cm×10.16 cm sodium iodide detector in 80 different sites in the basin, in Tuscany. The results from the FSA method with NNLS constrain have been compared with the laboratory measurements by using HPGe detectors on soil samples collected.
In the forth chapter is discussed the self-construction of an airborne gamma-ray spectrometer, AGRS_16.0L. Airborne gamma-ray spectrometry (AGRS) method is widely considered as an important tool for mapping environmental radioactivity both for geosciences studies and for purposes of radiological emergency response in potentially contaminated sites. Indeed, they have been used in several countries since the second half of the twentieth century, like USA and Canada, Australia, Russia, Checz Republic, and Switzerland.
We applied the calibration method described in the previous chapter using well -characterized natural sites and implemented for the first time in radiometric data analysis FSA analysis method with NNLS constrain. This method permits to decrease the statistical uncertainty and consequently reduce the minimum acquisition time (which depend also on AGRS system and on the flight parameters), by increasing in this way the spatial resolution. Finally, the AGRS_16.0L was used for radioelement mapping survey over Elba Island. It is well known that the natural radioactivity is strictly connected to the geological structure of the bedrocks and this information has been taken into account for the analysis and maps construction. A multivariate analysis approach was considered in the geostatistical interpolation of radiometric data, by putting them in relation with the geology though the Collocated Cokriging (CCoK) interpolator. Finally, the potential radioelement maps of potassium, uranium and thorium are constructed for Elba Island.
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Boson, Jonas. "Improving accuracy of in situ gamma-ray spectrometry." Doctoral thesis, Umeå : Umeå University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1805.
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SHYTI, Manjola. "Calibration and performances of in-situ gamma ray spectrometer." Doctoral thesis, Università degli studi di Ferrara, 2013. http://hdl.handle.net/11392/2388864.
Full textAbstract:
Since 1896, when Henri Becquerel discovered that penetrating radiation was given off in the radioactive decay of uranium, the studies on radioactivity have been an interest of scientific world. With the spread of nuclear technologies applied to energy, health and industrial production, the theme of environmental radioactivity monitoring increasingly is becoming important to the policies of the health public protection both national and European level. Italy is required to comply with the recommendation of the European Commission of 8 June 2000 on the application of Article 36 of the Euratom Treaty concerning the monitoring of levels of radioactivity in the environment for the purpose of assessing the exposure of the population as a whole. In addition, the World Health Organization has identified the first group of carcinogens gas 222Rn, which is considered the second leading cause, after smoking, of lung tumors. In our environment there are various sources of radioactivity that can be natural or artificial origin. Gamma-ray spectrometry is a widely used and powerful method that can be employed both to identify and quantify radionuclides.
The purpose of this work is calibration and performances of in situ a portable gamma ray spectrometer.
In the first chapter I have given the necessary concepts for understanding the phenomenon of radioactivity. Qualitatively has been described the process of radioactive decay and its three types which can occur in nature. Three categories of environmental radionuclides, cosmogenic, primordial and man-made are discussed. We are exposed to environmental radiation from different sources. The origin of radioactivity in the environment can be divided into two main sources: (a) natural and (b) man-made sources. Mostly the naturally occurring radiation arises from terrestrial radioactive nuclides that are widely distributed in the earth’s crust and extra-terrestrial sources arising from cosmic ray. Also from human activities arise some other sources concerned with the use of radiation and radioactive materials from which releases of radionuclides into the environment may occur.
In the second chapter is described the gamma radiation interacts with matter via three main processes: the photoelectric effect, Compton scattering and pair production The operation of a detector is based on the interaction of photons constituting the incident radiation with the material that constitutes the detector itself.. Thanks to these processes, all or part of the energy possessed by the radiation is transferred to the mass of the detector and then converted into an electrical signal. The basic notions related to the interaction of electromagnetic radiation with matter that we will provide in this chapter will therefore be useful to understand the mechanisms that are at the basis of the generation of a gamma spectrum. In addition, this chapter will briefly describe the two main types of gamma radiation detectors, i.e. the semiconductor detector and the scintillation, in particular the high-pure germanium detector (HPGe) and a sodium iodide detector activated by thallium NaI(Tl).
In the third chapter is described the study area in which are performed the measurements of natural radioactivity. The area under consideration is the Ombrone basin located in southern Tuscany and Commune of Schio located in Region of Veneto. During the campaign were acquired in situ 338 spectra, including 80 with the ZaNaI_1.0L placed on the ground (Ombrone), 80 with the ZaNaI_1.0L placed on a tripod at 1m height (Ombrone), 89 with the ZaNaI_1.0L placed on the ground (Schio) and 89 spectra are acquired with a backpack placed on the shoulders of an operator (Schio). In each of the 80 sites which have been realized the measurements of radioactivity with the ZaNaI_1.0L instrument, also have been taken 5 different soil samples, for a total of 400 samples. The abundances of 40K, 238U and 232Th were obtained from the analysis of 338 spectra taken with the ZaNaI_1.0L and 400 spectra measured on soil samples in the laboratory with a high-pure germanium detector (MCA_Rad). Also it is described the procedures of ZaNaI_1.0L portable scintillation gamma-ray spectrometers for in-situ measurements.
In the fourth chapter is described the procedure for the preparation of soil samples to be analyzed with the MCA_Rad system. The gamma-ray spectrometry system, called MCA_Rad introduces an innovative configuration of a laboratory high-resolution gamma-ray spectrometer featured with a complete automation measurement process, which can conduct measurements on each type of material (solid, liquid or gaseous) in less than 1 hour. The utilization of two coupled HPGe detectors permits to achieve good statistical accuracies in shorter time, which contributes in drastically reducing costs and man power involved. It is made a description of the characterization of absolute full-energy peak efficiency of such instrument reported here.
In the fifth chapter are discussed the correlations between the abundances of 40K, 238U and 232Th measured with the ZaNaI_1.0L and those obtained from laboratory analysis on soil samples. The analysis was focused in particular on the study of four different types of correlation: correlation between in-situ acquisition on ground and laboratory measurements, correlation between in-situ acquisition on tripod and laboratory measurements, correlation between in-situ acquisition on ground and on tripod and correlation between in-situ acquisition on ground and on operator shoulder and the influence of vegetative cover during measurements in-situ.
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Negoita, Cezar Ciprian. "Measurement of neutron flux spectra in a Tungsten Benchmark by neutron foil activation method." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1096547324156-18744.
Full textAbstract:
The nuclear design of fusion devices such as ITER (International Thermonuclear Experimental Reactor), which is an experimental fusion reactor based on the "tokamak" concept, rely on the results of neutron physical calculations. These depend on the knowledge of the neutron and photon flux spectra which is particularly important because it permits to anticipate the possible answers of the whole structure to phenomena such as nuclear heating, tritium breeding, atomic displacements, radiation shielding, power generation and material activation. The flux spectra can be calculated with transport codes, but validating measurements are also required. An important constituent of structural materials and divertor areas of fusion reactors is tungsten. This thesis deals with the measurement of the neutron fluence and neutron energy spectrum in a tungsten assembly by means of multiple foil neutron activation technique. In order to check and qualify the experimental tools and the codes to be used in the tungsten benchmark experiment, test measurements in the D-T and D-D neutron fields of the neutron generator at Technische Universität Dresden were performed. The characteristics of the D-D and D-T reactions, used to produce monoenergetic neutrons, together with the selection of activation reactions suitable for fusion applications and details of the activation measurements are presented. Corrections related to the neutron irradiation process and those to the sample counting process are discussed, too. The neutron fluence and its energy distribution in a tungsten benchmark, irradiated at the Frascati Neutron Generator with 14 MeV neutrons produced by the T(d, n)4He reaction, are then derived from the measurements of the neutron induced &#947;-ray activity in the foils using the STAYNL unfolding code, based on the linear least-square-errors method, together with the IRDF-90.2 (International Reactor Dosimetry File) cross section library. The differences between the neutron flux spectra measured by means of neutron foil activation and the neutron flux spectra obtained in the same assembly, making use of an NE213 liquid-scintillation spectrometer were studied. The comparison of measured neutron spectra with the spectra calculated with the MCNP-4B (Monte Carlo neutron and photon transport) code, which allows a crucial test of the evaluated nuclear data used in fusion reactor design, is discussed, too. In conclusion, this thesis shows the applicability of the neutron foil activation technique for the measurement of neutron flux spectra inside a thick tungsten assembly irradiated with 14 MeV from a D-T generatorDie Konstruktion von Fusionsreaktoren wie ITER (International Thermonuclear Experimental Reactor), der ein experimenteller Fusionsreaktor ist und auf dem "Tokamak"-Konzept beruht, basiert unter neutronenphysikalischen Gesichtspunkten auf den Ergebnissen von umfangreichen Simulationsrechnungen. Diese setzen die Kenntnis der Spektren des Neutronen- und Photonenflusses voraus die besonders wichtig ist, weil sie, die möglichen Antworten der ganzen Struktur auf physikalische Prozesse vorauszuberechnen erlaubt wie z.B.: Heizen durch nukleare Prozesse, Tritium-Brüten, Atomverschiebung, Abschirmung von Strahlung, Leistungserzeugung und Materialaktivierung. Die Flußspektren können mittels Transportcodes berechnet werden, aber es werden auch Messungen zu ihrer Bestätigung benötigt. Ein wichtiger Bestandteil des Strukturmaterials und der Divertor-Flächen der Fusionsreaktoren ist Wolfram. Diese Dissertation behandelt die Messungen der Neutronspektren und ?fluenz in einer Wolfram-Anordnung mittels der Multifolien-Neutronenaktivierungstechnik. Um die anzuwendenden experimentellen Geräte und die Codes, die im Wolfram-Benchmark-Experiment eingesetzt werden, zu überprüfen und zu bestimmen, wurden Testmessungen in den D-T und D-D Neutronenfeldern des Neutronengenerator der Technischen Universität Dresden durchgeführt. Die Eigenschaften der D-T und D-D Reaktionen, die für die Erzeugung von monoenergetischen Neutronen verwendet werden, sowie die Auswahl der Aktivierungsreaktionen, die für Fusionsanwendungen geeignet sind und die Aktivierungsmessung werden detailliert vorgestellt. Korrekturen, die sich auf den Neutronen-Bestrahlungsprozess und auf den Probenzählungsprozess beziehen, werden ebenfalls besprochen. Die Neutronenfluenz und ihre Energieverteilung in einem Wolfram-Benchmark, bestrahlt am Frascati Neutronen Generator mit 14 MeV-Neutronen aus der T(d, n)4He Reaktion, werden aus den Messungen der &#947;-Strahlenaktivität, die von Neutronen in den Folien induziert ist, durch den STAYNL Entfaltungscode, der auf der Methode der kleinsten Fehlerquadrate basiert, zusammen mit der IRDF-90.2 Wirkungsquerschnitt-Bibliothek abgeleitet. Die Unterschiede zwischen den Neutronenflußspektren, die mit Hilfe der Multifolien-Neutronenaktivierung ermittelt wurden, und den Neutronenflußspektren, gemessen im selben Aufbau mit einem NE-213 Flüssigszintillator, wurden untersucht. Die gemessenen Neutronenspektren werden den aus MCNP-4B Rechnungen (Monte Carlo neutron and photon transport) ermittelten Spektren gegenüber gestellt. Der Vergleich stellt einen wichtigen Test der evaluierten Kerndaten für Fusionsreaktorkonzepte dar. Zusammenfassend zeigt diese Arbeit die Anwendbarkeit der Multifolien-Neutronenaktivierungstechnik bei Messungen der Neutronenflussspektren innerhalb eines massiven Wolframblocks bei Bestrahlung mit schnellen Neutronen aus D-T Generatoren
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Schlarb, Michael Christian [Verfasser]. "Simulation and real-time analysis of pulse shapes from segmented HPGe-detectors / Michael Christian Schlarb." 2009. http://d-nb.info/999609335/34.
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Lauer, Martin [Verfasser]. "Digital signal processing for segmented HPGe detectors : preprocessing algorithms and pulse shape analysis / presented by Martin Lauer." 2004. http://d-nb.info/972595910/34.
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ČERNÁ, Kristýna. "Optimalizace měření HPGe detektorem s velmi nízkým pozadím pro dosažení nízkých hodnot MDA." Master's thesis, 2008. http://www.nusl.cz/ntk/nusl-49427.
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Abstract My thesis examines the measurement optimalization when the semiconductor HPGe detectors with a low background and a high relative efficiency are used for achieving low values of MDA (minimum detectable activity). I conducted my research in the Department of Spectrometry of SÚRO (National Radiation Protection Institute) in Prague. In this laboratory the standard geometries of detectors with lower efficiency are used. The aim of this thesis is to offer a proposal of new geometry, sizes and shapes of measurement cells which will better correspond with the demand for higher efficiency of updated detectors. The assignment was to find the best mathematical function to descibe the correlation between efficiency and the direction of the radiation point source towards the detector. This function is derived from experimentally obtained data. To conduct measurements, three kinds of detectors with high relative efficiency used for activity measurements at different geometries were selected. As the source of gamma radiation, the point sources with energies of 46 keV, 661 keV, 1332 keV in different distances and positions were used. The function was applied separatelly to each of the three detectors and to the areas above the detector and sidewards of the detector. The objective of the research was to project new measurement geometries or to optimalize the current ones which could be used also in other detectors with high efficiency. After integrating the function in the cylindrical area above the detector and the annular area sidewards of the detector, areas contributing substantially to the overall efficiency were determined. These areas may be considered to be the optimal sizes for new geometries in given positions. After combining all the optimal areas above the detector, sidewards of the detector and for selected energies and the detector, optimal sizes of a new geometry were found. The function can be used both in the front part and the side part of the detector but its validity is limited. The value of MDA for the particular geometry is in indirect proportion to the efficiency square root and thus this new geometry should lead to minimum values of MDA.
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Chkvorets, Oleg [Verfasser]. "Search for double beta decay with HPGe detectors at the Gran Sasso underground laboratory / presented by Oleg Chkvorets." 2008. http://d-nb.info/989822524/34.
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Horne, Steven Michael. "Multispectral gamma-ray analysis using clover detectors with application to uranium fission product analysis." 2013. http://hdl.handle.net/2152/21557.
Full textAbstract:
A high-efficiency gamma-ray counting system has been built at Los Alamos National Laboratory for use in analyzing nuclear forensics samples. This system consists of two clover high-purity germanium detectors and is surrounded by a thallium-doped sodium iodide annulus. Special precautions have been taken to ensure the system has a low background. The system is connected to XIA Pixie-4 fast digitizers and collects data in list-mode. This work is split into two main parts. The first part describes the proper steps and techniques to initialize the settings of a detector system connected to fast digitizers in order to optimize the system for resolution and throughput. The various counting modes for this particular system are described in detail, including the benefits and drawbacks of each mode. Steps are then shown to characterize the system by obtaining efficiency curves for various counting modes and sample geometries. Because of the close counting geometry involved with this system, true-coincidence summing factors must be calculated, and are done so in part by measuring the peak-to-total ratios of the system in its various counting modes across a wide energy range. The dead-time for the system can be complicated due to the multiple inputs of the system. Techniques for calculating the dead-time of multiple-detector systems are discussed. The second part of this work shows the system's usefulness in analyzing nuclear forensics samples, specifically irradiated enriched uranium. Three fission product parent-daughter pairs of different lifetimes are analyzed over a course of six months. The activities of each nuclide are calculated at each time step. Age dating techniques using the parent-daughter pairs are discussed, as well as the detection limits of each nuclide for a range of sample ages. Finally, avenues for further research are presented, as well as potential sources of error or uncertainty for this work.text
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González, Enrique Ramón. "Desarrollo de un método basado en simulación Monte Carlo para el cálculo y análisis de espectros gamma complejos, sin el uso de fuentes de referencia." Doctoral thesis, 2019. http://hdl.handle.net/11086/18137.
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tesis (doctor en física)--universidad nacional de córdoba. facultad de matemática, astronomía, física y computación, 2019.en esta tesis, se desarrolla un método basado en simulaciones monte carlo que permite el cálculo y el análisis de espectros gamma complejos a partir de los espectros medidos, sin el uso de muestras calibradas. el método, es adecuado para calcular eficiencias de pico y eficiencias totales, detectar la presencia de líneas entremezcladas u ocultas, y determinar el área de picos de líneas situadas sobre el fondo real de otras de mayor energía. el método, es eficaz para determinar y estudiar efectos de coincidencia y también para obtener y estudiar efectos de auto-absorción en muestras de formas y tamaños variados.
in this thesis, a method based on monte carlo simulations is developed that allows the calculation and analysis of complex gamma spectra starting from the measured spectra, without the use of calibrated samples. the method is suitable for calculating peak efficiencies and total efficiencies, detecting the presence of intermixed or hidden lines, and determining the area of peaks of lines located on the real background of others of higher energy. the method is effective for determining and studying coincidence effects and also for obtaining and studying self-absorption effects in samples of varied shapes and sizes.
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fil: gonzalez, enrique. universidad nacional de córdoba. facultad de matemática, astronomía, física y computación; argentina.
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(5929988), Shih-Chieh Liu. "Test of Decay Rate Parameter Variation due to Antineutrino Interactions." Thesis, 2019.
Find full textAbstract:
High precision measurements of a weak interaction decay were conducted to search for possible variation of the decay rate parameter caused by an antineutrino flux. The experiment searched for variation of the 54Mn electron capture decay rate parameter to a level of precision of 1 part in ∼105 by comparing the difference between the decay rate in the presence of an antineutrino flux ∼3×1012 cm-2sec-1 and no flux measurements. The experiment is located 6.5 meters from the reactor core of the High Flux Isotope Reactor (HFIR) in Oak Ridge National Laboratory. A measurement to this level of precision requires a detailed understanding of both systematic and statistical errors. Otherwise, systematic errors in the measurement may mimic fundamental interactions. The gamma spectrum has been collected from the electron capture decay of 54Mn. What differs in this experiment compared to previous experiments are, (1) a strong, uniform, highly controlled, and repeatable source of antineutrino flux, using a reactor, nearly 50 times higher than the solar neutrino flux on the Earth, (2) the variation of the antineutrino flux from HFIR is 600 times higher than the variation in the solar neutrino flux on the Earth, (3) the extensive use of neutron and gamma-ray shielding around the detectors, (4) a controlled environment for the detector including a fixed temperature, a nitrogen atmosphere, and stable power supplies, (5) the use of precision High Purity Germanium (HPGe) detectors and finally, (6) accurate time stamping of all experimental runs. By using accurate detector energy calibrations, electronic dead time corrections, background corrections, and pile-up corrections, the measured variation in the 54Mn decay rate parameter is found to be δλ/λ=(0.034±1.38)×10-5. This measurement in the presence of the HFIR flux is equivalent to a cross-section of σ=(0.097±1.24)×10-25 cm2. These results are consistent with no measurable decay rate parameter variation due to an antineutrino flux, yielding a 68% confidence level upper limit sensitivity in δλ/λ <= 1.43×10-5 or σ<=1.34×10-25 cm2 in cross-section. The cross-section upper limit obtained in this null or no observable effect experiment is ∼104 times more sensitive than past experiments reporting positive results in 54Mn.
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Hour, I.-Min, and 侯一民. "Well-type HPGe detector efficiency calibration and true- coincidence correction." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/28435468598644644961.
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Ma, Wei Yang, and 馬維揚. "HPGe Detector Absolute-peak-efficiency calibration for Large Source by Using ESOLAN Program." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/15237325698742075731.
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Liang, Gee-fong, and 梁治方. "A study of portable HPGe detector on method of calibration for BWR recirculation pipe radiation build-up measurement." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/81517570909946854383.
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碩士國立清華大學
工程與系統科學系
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Using experimental and simulation method we found a general-purpose simulation software MCNP can be used in our special-configuration calibration of efficiency with the same type fitting curve on the measurement of BWR recirculation pipe build-up with the portable HPGe detector during the outage period. The MCNP simulation deviation can be controled under 10% while ISOCS application here isn’t fitted and only the simple type of sources and shielding can reach 5% deviation yet other complicated ones could be as large as around 60% based on our experiment.
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Marques, Luís Miguel Cabeça. "Estudo comparativo de detectores de HPGe, NaI(TI), CdZnTe para aplicações em segurança e para resposta a ameaças nucleares e radiológicas." Master's thesis, 2011. http://hdl.handle.net/10451/7956.
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Tese de mestrado em Engenharia Física, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2011Após ataques terroristas recentes, aumentou a preocupação internacional sobre as ameaças de índole nuclear e radiológica (NR), associadas ao tráfico ilícito não apenas de materiais nucleares e à sua possível aplicação em engenhos nucleares improvisados, mas também de outros materiais radioactivos (utilizados em aplicações na indústria, medicina e investigação) de possível aplicação em dispositivos de dispersão radiológica. Neste contexto, vários instrumentos, tratados e convenções e planos de acção internacionais foram estabelecidos e assinados na última década para reforçar a segurança e controlo de materiais nucleares e de matérias radioactivas. O presente trabalho teve como principais objectivos analisar as características dos detectores de Germânio Hiper-Puro (HPGe), de Telureto de Cádmio e Zinco (CdZnTe) e de Iodeto de Sódio activado com Tálio (NaI(Tl)) para a detecção, identificação e quantificação de radionuclídeos em cenários de ameaças NR e formular, baseado na caracterização dosimétrica da exposição dos membros das equipas de intervenção, recomendações operacionais relevantes para a resposta em situações decorrentes de ameaças ou de emergências NR. Para alcançar estes objectivos foi utilizado o programa de simulação por métodos Monte Carlo MCNP, representativo do estado da arte computacional na simulação do transporte de radiação, para o cálculo das eficiências dos detectores e para a estimativa, utilizando um fantoma de voxel, de débitos de doses de radiações ionizantes a que estão expostos os membros das equipes de intervenção. Os resultados obtidos através das simulações Monte Carlo sugerem que os detectores CdZnTe apresentam um decréscimo acentuado da eficiência de fotopico acima dos 200 keV, o que os tornam adequados à identificação de radionuclídeos em campos de radiação de baixa energia. A excelente resolução em energia dos detectores HPGe torna-os na escolha ideal para a identificação de radionuclídeos em espectros complexos, apesar de exibirem eficiências de detecção inferiores às dos detectores NaI(Tl)).
After recent terrorista attacks, an increased international concern has emerged about the radiological and nuclear (RN) threats associated with the illicit trafficking not only of nuclear materials due to their possible application in improvised nuclear devices, but also of other radioactive materials (used in industry , medicine and research applications) of possible applications in radiological dispersal devices (RDDs). In this context, various instruments, treaties and conventions and international action plans have been established and signed in the last decade with the objective to enhance security and control of nuclear materials and radioactive materials. This work had as main objective the analysis of the characteristics of Hyper-Pure Germanium (HPGe), of Cadmium and Zinc Telluride (CdZnTe) and Sodium Iodide activated with Thallium (NaI(Tl)) detectors for the indentification and quantification of radionuclides in RN threat scenarios and to formulate, based on the dosimetric characterization of the exposure of the intervention teams and of first responders, operational recommendations relevant to management of RN threats and emergencies. To achieve these goals, we used the Monte Carlo simulation code MCNP, representing the state of the art in Monte Carlo simulation of radiation transport, for the calculation of detector’s efficiencies and to assess, using a voxel phantom, the dose rates of ionizing radiation to which the members of the intervention teams are exposed. The results obtained from the Monte Carlo simulations suggest that the CdZnTe detectors have a sharp decrease in the photopeak efficiency above 200 keV, which makes them suitable for the detection and indentification in low-energy radiation fields. Despite their lower detection efficiencies compared to those of NaI(Tl) detectors, the excellent energy resolution of HPGe detectors makes them the ideal choice for the identification of radionuclides in complex spectra.