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1
Easton, Jayson Lee. "New bands in ¹⁹²Tl using gamma spectroscopy techniques." University of the Western Cape, 2011. http://hdl.handle.net/11394/5419.
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>Magister Scientiae - MSc<br>High spin excited stats in¹⁹²Tl were studied using gamma-ray spectroscopy. The study included taking an active part in performing the experiment, understanding the experimental procedure, electronics and data acquisition in this experiment. The high spin states in ¹⁹²Tl were produced using a ³⁷Cl beam and ¹⁶⁰Gd target. The nine clovers of the AFRODITE array were placed at 90° and 135°. The target was thin, allowing the residual thallium nuclei to recoil in vacuum. Two weeks of data was acquired and analysed in this work. In addition more data was acquired in order to perform DSAM lifetime measurements, but this is beyond the scope of this work. The preliminary data analysis of the thin target data involved energy
and time-gain matching calibrations as well as Doppler shift and gain drift corrections. Then the data were sorted into matrices and spectra for the actual analysis. The known level scheme of ¹⁹²Tl was extended by more than 50 new transitions placed in three new bands. A chiral partner to the yrast band in ¹⁹²92Tl was searched for but not found. But there is still a possibility such a band to be discovered, when the additional three weekends of data (including the DSAM lifetime measurements) undergo such an analysis.
2
Oates, Sean Benjamin. "Structure of the nucleus ¹¹⁴Sn using gamma-ray coincidence data." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1019870.
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Paradis, Hugues. "Développement de la mesure par spectrométrie gamma en coïncidence." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS215/document.
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Dans le cadre de la mission de surveillance radiologique de l’environnement de l’Institut de Radioprotection et de Sûreté Nucléaire (IRSN), le Laboratoire de Mesure de la Radioactivité dans l’Environnement (LMRE) réalise la mesure de la concentration en activité dans différentes matrices environnementales. Il s’agit de matrices biologiques (mousses aquatiques, algues, lait, légumes …), de sols, d’eaux ou encore de filtres de prélèvement d’aérosols.Les radionucléides artificiels recherchés sont en très faible proportion par rapport à certains radionucléides naturels : le potassium 40 dans les matrices biologiques ou encore les descendants particulaires du radon dans les filtres d’aérosols. L’important fond Compton induit par ces radionucléides naturels dans le spectre gamma complique la détermination des radionucléides présents au niveau trace.Un moyen de s’affranchir de ce fond Compton est de faire une mesure par spectrométrie $gamma$ en coïncidence en utilisant au moins deux détecteurs. La méthode a été développée sur un système existant, le système anti-Compton constitué d’un détecteur germanium entouré d’un scintillateur NaI(Tl), avec le développement d’un algorithme d’analyse et de l’étalonnage par simulation Monte Carlo si nécessaire. De plus, un nouveau système de mesure en coïncidence a été conçu par simulation Monte Carlo puis mis en service pour pallier les limites du système anti-Compton. Ce nouveau système de mesure, nommé Léda, est composé de deux détecteurs germanium face à face, entourés d’un scintillateur NaI(Tl) ; il possède plusieurs voies de mesure, chacune présentant une amélioration en termes de limite de détection pour tous les radionucléides mesurés<br>The French Institute of Radiation Protection and Nuclear Safety (IRSN) is in charge of the radiological surveillance of the environment. In this framework the Laboratory of Environment Radioactivity Measurement (LMRE) measures the radioactivity concentrations in various environmental samples: biological matrices (aquatic moss, seaweed, milk, vegetables …), soils, waters or aerosol filters.Artificial radionuclides searched are in low proportion compared to natural radionuclides: potassium 40 in biological matrices or radon particular daughters in aerosol filters. The significant Compton continuum induced in the gamma spectrum makes difficult the identification and the quantification of radionuclides present at trace level.The use of two detectors enables to make coincident spectrometry in order to decrease this Compton background. This technique was developed with an existing system of the laboratory, the anti-Compton system, composed of a germanium detector surrounded by a NaI(Tl) scintillator. A data analysis algorithm was developed and also a Monte Carlo calibration if radionuclides measured are not available in standard source. Moreover a new coincident measurement system was designed by Monte Carlo simulation, called Leda consisting of two germanium detectors face to face surrounded by a NaI(Tl) scintillator. This new system overcomes the limits of the anti-Compton system. Different measurement channels improve the detection limits for all radionuclides measured in our laboratory
4
FONSECA, KATIA A. "Medida absoluta da atividade e determinacao da taxa de emissao gama por decaimento do sup 126I." reponame:Repositório Institucional do IPEN, 1997. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10495.
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Brasse, David. "Detection en coincidence des photons de 511 kev provenant de l'annihilation des positons sur gamma-camera conventionnelle : optimisation et analyse des potentialites." Paris 5, 1999. http://www.theses.fr/1999PA05N148.
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Löher, Bastian [Verfasser]. "Probing the decay characteristics of the Pygmy Dipole Resonance in the semi-magic nucleus 140 Ce with gamma-gamma coincidence measurements / Bastian Löher." Mainz : Universitätsbibliothek Mainz, 2014. http://d-nb.info/1054937206/34.
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Camborde, Marie-Laure A. "Use of beta-gamma coincidence to improve the quality of transmission scans for PET." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33723.
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The availability of accurately aligned, whole body, functional PET images has a significant impact on the diagnosis of malignant disease and on identifying and localizing metastasis. Gamma ray attenuation correction is essential in all quantitative PET studies.<br>The object of this study was to explore the possibility of using beta-gamma coincidence as an attenuation correction technique in order to improve transmission scan image quality.<br>This study consisted of testing and implementing a beta-gamma attenuation correction technique on an animal PET scanner. In its final form the system uses 68Ge sources enclosed in plastic scintillator cylinders coupled to PMTs. The detection of positrons is activated by the energy loss in the scintillator medium. This system is used in coincidence with one of the animal PET scanner's BGO crystal detectors in order to acquire transmission scans.
8
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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Ooi, Stanley Seong Ling. "A study of the γ-rays from the self-conjugate nuclei ⁶⁴Ge and ⁴⁸Cr using n-γ coincidence techniques". Thesis, University of Oxford, 1986. http://ora.ox.ac.uk/objects/uuid:99d3c76a-dcb9-44d9-8a9c-b69f58d7cbef.
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A neutron multiplicity detector system has been developed to study weak pure neutron evaporation channels from heavy-ion reactions. Such a system allows us to study nuclei far away from the line of β-stability - in particular, self-conjugate nuclei where the shell-effects for protons and neutrons are in phase and their combined effects may drive the nucleus towards superdeformation. The system consists of a neutron wall - 4 large volume Ge(Li) γ-ray detectors positioned as close as possible to the target. Neutron-gamma coincidences were recorded and neutron multiplicity events could be extracted from the data. Rejection of gamma-ray events in the neutron detectors was achieved by time-of-flight and pulse shape discrimination methods. A surface barrier detector at 0⁰ allowed a further rejection of charged particle events - especially events which feature neutrons as well.
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Daniel, Terver. "Nuclear structure studies of low-lying states in 194Os using fast-timing coincidence gamma-ray spectroscopy." Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/813294/.
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The properties of excited states in the neutron-rich nucleus 194Os have been investigated using the 192Os(18O,16O)194Os 2 neutron transfer reaction using a 80 MeV 18O heavy-ion beam provided by the tandem van de Graaff accelerator at the IFIN-HH laboratory Bucharest. Discrete γ-ray decays from excited states have been measured using the hybrid HPGe-LaBr3(Ce) γ-ray spectroscopic array RoSPHERE. The timing and energy response of the RoSPHERE system have been evaluated using a number of point radioactive sources and through other nuclear reaction products formed from reactions on minor target contaminants as well as via unsafe Coulomb excitation on the 192Os target. The work identifies a number of previously unreported low lying non-yrast states in 194Os as well as the first B(E2;2+ → 0+) measurement for this nucleus. The experimental results are compared with HFB/IBM calculations and are consistent with a reduction in a quadrupole collectivity in Os isotopes with increasing N.
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MOREIRA, DENISE S. "Medida absoluta da taxa de desintegracao e da probabilidade de emissao gama do sup[42]K." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10810.
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DOMIENIKAN, CLAUDIO. "interface eletronica para aquisicao de 12 espectros de coincidencias gama-gama atrasadas." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10889.
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MEDEIROS, ILCA M. M. A. "Espectroscopia gama no nucleo sup(149) Nd." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10961.
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Lacerda, Flavio William. "Padronização de Ga-68 em sistema de coincidências 4πβ-&gamma." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-04072013-134929/.
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O presente trabalho tem como objetivo a padronização de 68Ga, um emissor de pósitrons de meia-vida curta, usado em PET (Tomografia por Emissão de Pósitrons). A padronização do 68Ga foi realizada em um sistema de coincidência 4πβ-γ, que consiste de um detector proporcional em geometria 4π a gás fluente acoplado a um detector de cristal semicondutor HPGe, para a detecção de raios gama. A aquisição de dados foi realizada por meio de um Sistema de Coincidência por Software (SCS), desenvolvido no Laboratório de Metrologia Nuclear (Laboratório de Metrologia Nuclear - LMN) no IPEN-CNEN / SP. Os resultados finais foram obtidos a partir de um ajuste de curva multiparamétrica aplicando-se uma metodologia que leva em consideração a matriz de covariância combinando os resultados experimentais com aqueles determinados pela simulação Monte Carlo.<br>The present work aims the standardization of 68Ga, a positron emitter of short half-life used in PET (Positron Emission Tomography). The 68Ga standardization was performed in a 4πβ-γ coincidence system that consists of a gas-flow proportional counter (PC) in 4π geometry coupled to a HPGe crystal, for gamma-ray detection. The data acquisition was carried out by means of a Software Coincidence System (SCS) developed at the Nuclear Metrology Laboratory (Laboratório de Metrologia Nuclear LMN) at the IPEN-CNEN/SP. The final results were obtained from a multiple curve fitting applying a covariance matrix methodology combining experimental results with those determined by the Monte Carlo simulation.
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MOREIRA, DENISE S. "Padronização dos radionuclídeos multi-emissores gama sup(166m)Ho e sup(72)Ga e determinação de suas intensidades gama por decaimento." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11295.
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PIRES, CARLOS A. "Padronização dos radionuclídeos sup(201)Ti e sup(55)Fe em sistema de consciências 4`pi`(PC)-Nal(Ti)." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11651.
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CAMARGO, SONIA P. de. "Correlacao angular direcional gama-gama no nucleo de sup76Se." reponame:Repositório Institucional do IPEN, 1998. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10725.
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Minutilli, Loreta. "Fermi blazars as candidate neutrino emitters: a study of temporal coincidence with IceCube events." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22554/.
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Multimessenger astronomy provides a unique tool for exploring the universe at the highest energies: the association between neutrinos and their astrophysical sources would constitute a powerful probe of the high-energy sky.
In 2017, the neutrino event IceCube-170922A was found to be coincident in arrival time and direction with an enhanced γ-ray activity from the blazar TXS 0506+056 at redshift z ∼ 0.34, and it was associated to this source at the 3σ confidence level. This discovery motivates further research in the field of the blazar-neutrino connection.
In this work, the temporal coincidence between the arrival times of IceCube
neutrinos and the γ-ray (0.1 − 300 GeV) emission from a sample of Fermi-detected blazars is investigated. The spatial coincidence for the same sample had been investigated in a previous reference work.
Different criteria for the definition of the flaring state of a source were adopted depending on the blazar class (HBL/IBL or LBL) and a subsample of 4 flare-neutrino coincident blazars was selected.
A statistical test was performed on each class separately in order to assess the nature of the observed coincidences. An interesting excess was found for the class of HBLs/IBLs while no excess was observed for the LBLs.
I discussed the implications of these results for the blazar neutrino connection and the future perspectives for this work.
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Zagatto, Vinicius Antonio Bocaline. "Estudo de mecanismos de reação nuclear no sistema 7Li+120Sn utilizando coincidências -partícula." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-06052015-053049/.
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Medidas em coincidência gamma-partícula da reação 7Li+120Sn foram realizadas na faixa de energia de 2.6 a 3.9 MeV por nucleon. Além do canal inelástico, foram observados os canais de pick-up de próton e stripping de um e dois nêutrons, sendo que, para o último caso, cálculos teóricos de DWBA e CRC comparados com o canal elástico demonstram que esta transferência ocorre de maneira sequencial (two-step) e não direta. Este trabalho consolida a existência de canais já anteriormente observados (pick-up de próton e stripping de um nêutron) além de observar pela primeira vez a existência do canal de strippinp de dois nêutrons, no entanto, ele tem um caráter pioneiro pois é o primeiro a medir distribuições angulares de todos esses canais. Tanto o pick-up de próton quanto o stripping de dois nêutrons tiveram de levar em conta na análise cálculos de Monte Carlo que simulassem o efeito da quebra dos projéteis 8Be e 5Li, respectivamente. Fatores espectroscópicos para alguns estados desses canais foram obtidos e são condizentes com os valores esperados considerando o modelo de single particle e a indistinguibilidade de partículas nos casos dos núcleos 119In e 122Sn. Por outro lado, são muito pequenos (ordem de 10e-2) para estados do 121Sn, fato esse gerado pela provável falta de acoplamento de mais canais de reação que reduzem o fluxo da transferência de nêutron. Foram observados também núcleos gerados a partir da transferência seguida de emissão de partículas.<br>$\\gamma$-particle coincidence measurements of the $^7$Li$+^{120}$Sn reaction were made in the $2.6$ to $3.9$ MeV/nucleon energy range. Besides the inelastic channel, the proton {\\it pick-up} and one/two neutron {\\it stripping} were observed, whereas, for the last case, DWBA and CRC calculations were compared to experimental elastic scattering data and demonstrated that this transfer occurs in a sequential ({\\it two-step}) rather than a direct way. This work consolidates the existence of some channels that have already been observed (proton {\\it pick-up} and neutron {\\it stripping}) and also observes for the first time the existence of the two neutron {\\it stripping} channel, however, it still retains its pioneering as it is the first one to measure the angular distributions for all these channels. The proton {\\it pick-up} and the two neutron {\\it stripping} channels had to take into account in their analysis Monte Carlo calculations to simulate the projectile breaking effect ($^8$Be and $^5$Li, respectively). Spectroscopic factors for some states of these channels were found and are consistent with the expected values considering the {\\it single particle} model and the particle indistinguishability for the $^{119}$In and $^{122}$Sn cases, however, these factors are too small (magnitude order of $10^{-2}$) for the $^{121}$Sn case. This was generated most likely by the lack of coupling of some of the reaction channels that would reduce the one neutron transfer flux. Nuclei generated by the transfer followed by particle emission were also observed.
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BACCARELLI, AIDA M. "Sistema primario por coincidencias 4 pi beta-gama para a padronizacao de radionuclideos empregando cintiladores plasticos." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11125.
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SILVA, FABRICIO F. V. da. "Medida absoluta da atividade e determinacao da probabilidade de missao gama por decaimento do sup(177)Lu." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9947.
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ZAHN, GUILHERME S. "Estudo do decaimento beta do sup(193)Os." reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11440.
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Takeda, Mauro Noriaki. "APLICAÇÃO DO MÉTODO DE MONTE CARLO NO ESTUDO DA PADRONIZAÇÃO DE RADIONUCLÍDEOS COM ESQUEMA DE DESINTEGRAÇÃO COMPLEXOS EM SISTEMA DE COINCIDÊNCIAS 4πβ-γ." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-31052007-145307/.
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O presente trabalho descreve uma nova metodologia desenvolvida para modelar o comportamento da atividade em sistema de coincidência 4π(PC)β-γ. As eficiências para elétrons no detector proporcional (PC) e para radiação gama no detector de NaI(Tl) foram calculadas utilizando o programa de Monte Carlo MCNP4C. Outro código de Monte Carlo foi desenvolvido para seguir o caminho no esquema de desintegração desde o estado inicial do radionuclídeo precursor, até o estado fundamental do núcleo filho. Cada etapa do esquema de desintegração é selecionada por meio de números aleatórios levando em conta as probabilidades de cada ramo β- ou captura eletrônica, as probabilidades de transição e os coeficientes de conversão interna. Uma vez que o estado final tenha sido atingido é verificado se houve detecção de eventos beta, captura eletrônica ou transições gama, e os eventos para os três espectros, beta, gama e coincidência são contabilizados. A variação da eficiência beta pode ser feita através da simulação de corte na energia detectada ou pela utilização de absorvedores (Collodion). Foram escolhidos para a simulação os radionuclídeos 134Cs, 72Ga que se desintegram por transição β-, 133Ba que se desintegra por captura eletrônica e 35S que é um emissor beta puro. Para este último foi simulando o Método do Traçador. As curvas de extrapolação obtidas por Monte Carlo foram ajustadas pelo Método dos Mínimos Quadrados com os pontos experimentais e comparados com os resultados obtidos pelo Método da Extrapolação Linear.<br>The present work describe a new methodology for modelling the behaviour of the activity in a 4π(PC)β-γ coincidence system. The detection efficiency for electrons in the proportional counter and gamma radiation in the NaI(Tl) detector was calculated using the Monte Carlo program MCNP4C. Another Monte Carlo code was developed which follows the path in the disintegration scheme from the initial state of the precursor radionuclide, until the ground state of the daughter nucleus. Every step of the disintegration scheme is sorted by random numbers taking into account the probabilities of all β- branches, electronic capture branches, transitions probabilities and internal conversion coefficients. Once the final state was reached beta, electronic capture events and gamma transitions are accounted for the three spectra: beta, gamma and coincidence variation in the beta efficiency was performed simulating energy cut off or use of absorbers (Collodion). The selected radionuclides for simulation were: 134Cs, 72Ga which disintegrate by β- transition, 133Ba which disintegrates by electronic capture and 35S which is a beta pure emitter. For the latter, the Efficiency Tracing technique was simulated. The extrapolation curves obtained by Monte Carlo were filled by the Least Square Method with the experimental points and the results were compared to the Linear Extrapolation method.
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Sowazi, Khanyisa. "Investigating the Gamma-ray Strength Function in 74Ge using the Ratio Method." University of the Western Cape, 2018. http://hdl.handle.net/11394/6513.
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>Magister Scientiae - MSc<br>An increasing number of measurements reveal the presence of a low-energy enhancement
in the gamma-ray strength function (GSF). The GSF, which is the
ability of nuclei to absorb or emit
rays, provides insight into the statistical properties
of atomic nuclei. For this project the GSF was studied for 74Ge which was
populated in the reaction 74Ge(p,p')74Ge* at a beam energy of 18 MeV. The data
were collected with the STARS-LIBERACE array at Lawrence Berkeley National
Laboratory. Silicon detector telescopes were used for particle identi cation and
rays in coincidence were detected with 5 clover-type high-purity germanium detectors.
Through the analysis particle-
-
coincidence events were constructed.
These events, together with well-known energy levels, were used to identify primary
rays from the quasicontinuum. Primary
rays from a broad excitation
energy region, which decay to six 2+ states could be identi ed. These states and
the associated primary
rays are used to measure the GSF for 74Ge with the
Ratio Method [1], which entails taking ratios of e ciency-corrected primary
-ray
intensities from the quasicontinuum. Results from the analysis of the data and
focus on the existence of the low-energy enhancement in 74Ge will be discussed.
The results are further discussed in the context of other work done on 74Ge using
the (
,
') [2], (3He,3He') [3] and ( , ') [4] reactions.
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Brancaccio, Franco. "Metodologia de aquisição de dados e análise por software, para sistemas de coincidências 4πβ-γ e sua aplicação na padronização de radionuclídeos, com ênfase em transições metaestáveis." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-03102013-104013/.
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O Laboratório de Metrologia Nuclear (LMN) do Instituto de Pesquisas Energéticas e Nucleares (IPEN) desenvolveu recentemente o Sistema de Coincidência por Software (SCS), para a digitalização e registro dos sinais de seus sistemas de coincidências 4πβ-γ utilizados na padronização de radionuclídeos. O sistema SCS possui quatro entradas analógicas independentes que possibilitam o registro simultâneo dos sinais de até quatro detectores (vias β e γ). A análise dos dados é realizada a posteriori, por software, incluindo discriminação de amplitudes, simulação do tempo-morto da medida e definição do tempo de resolução de coincidências. O software então instalado junto ao SCS estabeleceu a metodologia básica de análise, aplicável a radionuclídeos com decaimento simples, como o 60Co. O presente trabalho amplia a metodologia de análise de dados obtidos com o SCS, de modo a possibilitar o uso de detectores com alta resolução em energia (HPGe), para padronização de radionuclídeos com decaimentos mais complexos, com diferentes ramos de decaimento ou com transições metaestáveis. A expansão metodológica tem suporte na elaboração do programa de análise denominado Coincidence Analyzing Task (CAT). A seção de aplicação inclui as padronizações do 152Eu (diferentes ramos de decaimento) e do 67Ga (nível metaestável). A padronização do 152Eu utilizou uma amostra de uma comparação internacional promovida pelo BIPM (Bureau International des Poids et Mesures), podendo-se comparar a atividade obtida com o valores de laboratórios mundialmente reconhecidos, de modo a avaliar e validar a metodologia desenvolvida. Para o 67Ga, foram obtidas: a meia-vida do nível metaestável de 93 keV, por três diferentes técnicas de análise do conjunto de dados (βpronto-γatrasado-HPGe, βpronto-γatrasado-NaI e βpronto- βatrasado); as atividades de cinco amostras, normalizadas por Monte Carlo e as probabilidades de emissão gama por decaimento, para nove transições.<br>The Nuclear Metrology Laboratory (LMN) at the Nuclear and Energy Research Institute (IPEN São Paulo, Brazil) has recently developed the Software Coincidence System (SCS), for the digitalization and recording of signals from its 4πβγ detection systems. SCS features up four independent analog inputs, enabling the simultaneous recording of up four detectors (β and γ). The analysis task is performed a posteriori, by means of specialized software, including the setting up of energy discrimination levels, dead-time and coincidence resolution time. The software initially installed was able to perform a basic analysis, for the standardization of simple decay radionuclides, such as 60Co. The present work improves the SCS analysis methodology, in order to enable the use of high resolution detectors (HPGe), for standardization of complex decay radionuclides, including metastable transitions or different decay branches. A program called Coincidence Analyzing Task (CAT) was implemented for the data processing. The work also includes an application section, where the standardization results of 152Eu (different decay branches) and 67Ga (with a metastable level) are presented. The 152Eu standardization was considered for the methodology validation, since it was accomplished by the measurement of a sample previously standardized in an international comparison sponsored by the BIPM (Bureau International des Poids et Mesures). The activity value obtained in this work, as well as its accuracy, could be compared to those obtained by important laboratories in the world. The 67Ga standardization includes the measurement of five samples, with activity values normalized by Monte Carlo simulation. The 93 keV metastable level half-life and the gamma emission probabilities per decay for nine transition of 67Ga are also presented. The metastable half-life was obtained by three different methods: βprompt-γdelayed-HPGe, βprompt-γdelayed-NaI and βprompt-βdelayed.
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Correa, Gustavo Polillo. "Aplicação do Método de Monte Carlo no estudo da atividade obtida em sistema de coincidências 4π(β,EC)-γ pelo Método da Discriminação com Reposição." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-24032016-093628/.
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O objetivo do presente trabalho foi o de estabelecer uma nova característica ao programa de Monte Carlo ESQUEMA, destinado a simular todo o processo de detecção em um sistema de coincidência 4π(β,EC)-γ e possibilitou o conhecimento antecipado do comportamento da atividade aparente da fonte radioativa como função da eficiência do detector 4π. Esta metodologia foi aplicada anteriormente para os casos onde a eficiência é variada pela colocação de absorvedores sobre a fonte radioativa ou variando-se o nível de discriminação eletrônica, com a exclusão completa das contagens abaixo deste nível. No presente trabalho, esta metodologia foi modificada com a inclusão dos eventos não coincidentes abaixo do nível de discriminação eletrônica, adotado para a via beta. Desta forma, a curva de extrapolação passa a ter um comportamento rigorosamente linear e o valor extrapolado corresponde a atividade da fonte radioativa, esperando-se obter uma melhor acurácia no seu valor. Esta alteração é inovadora e particularmente apropriada para ser aplicada ao caso de medidas com o Sistema de Coincidências por Software (SCS), desenvolvido recentemente pelo LMN. O trabalho consiste na modificação de um programa desenvolvido no LMN, denominado ESQUEMA, que leva em conta as características gerais de um esquema de desintegração complexo, incluindo-se os diversos tipos de transição, além das características experimentais do sistema de medidas por coincidência 4π(β,EC)-γ. Estas modificações permitem a obtenção das curvas de extrapolação, aplicando-se o método proposto de Discriminação com Reposição. O software MCNP5 é usado para simular o transporte de radiação. A simulação de Monte Carlo é comparada com valores experimentais para o radionuclídeo padronizados no LMN, o 111In .<br>The aim of the present work is to establish a new feature to the Monte Carlo code ESQUEMA developed by the Nuclear Metrology Laboratory (LMN), in order to simulate the whole detection process in a 4π(β,EC)-γ system and predict the behavior of radioactive source activity as a function of 4π detector. The methodology was applied previously, when the efficiency is modified by adding absorbers over or under the radioactive source or modifying the electronic discrimination level by excluding all events below this level. In the present work, this methodology applying beta pulse height discrimination has been modified adding to the beta spectrum noncoincident events occurring below the lower level, which are cutted off by the conventional discrimination procedure. In this way, the extrapolation curve is modified obtaining straight line shape and the extrapolated value, corresponding to the radioactive source activity, is expected to achieve better accuracy. This feature is particularly suitable for measurements with the Software Coincidence System (SCS), recently developed at the LMN. The main goal of present work is to modify the software developed by the LMN team, called ESQUEMA where all the characteristics of a complex disintegration scheme are considered, including different kind of transitions and experimental features of 4π(β,EC)-γ detection process. These changes allow to obtain the extrapolated value by the proposed method of Discrimination with Reposition. The software MCNP5 is used to simulate the radiation transport. The Monte Carlo simulation is compared to experimental results obtained for 111In, recently standardized by the LMN using the SCS and conventional extrapolation techniques.
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Toledo, Fabio de. "Desenvolvimento de um sistema eletrônico com registro simultâneo de amplitude e instante de ocorrência dos pulsos aplicado ao método de coincidências 4πβ-&gamma." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-22092011-091715/.
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Em Metrologia Nuclear, há muitos anos, o método absoluto de medida de atividade radioativa por coincidência 4πβ-γ tem sido considerado um padrão primário, em razão de seu alto grau de exatidão e por depender de grandezas observáveis para a obtenção de resultados. O Laboratório de Metrologia Nuclear (LMN), do Instituto de Pesquisas Energéticas e Nucleares (IPEN), dentre suas técnicas de medida, utiliza a metodologia de coincidência 4πβ-γ. Uma nova técnica, conhecida como medida de coincidência por software tem sido empregada na padronização de radionuclídeos, com muitas vantagens sobre a metodologia convencional. Com o objetivo de atualizar sua metodologia de padronização de radionuclídeos, o LMN desenvolveu um novo sistema de medida de coincidências por software, descrito neste trabalho. O sistema eletrônico emprega os mesmos arranjos de detecção beta e gama utilizados em seus sistemas. O novo sistema é constituído por uma placa de aquisição de dados da National Instruments (NI), conectada a um microcomputador e, através de um painel de conexão, aos arranjos de detecção. O gerenciamento é obtido através de software desenvolvido em LabVIEW, proprietária da NI. Este sistema registra as amplitudes e os instantes de ocorrência dos pulsos de detecção beta e gama, em arquivos de disco. Os arquivos são posteriormente analisados por um programa apropriado, o software de análise de coincidências, de forma a obter as contagens beta, gama e de coincidências, e executando o processamento necessário para a determinação da atividade da amostra radioativa de interesse. O trabalho também apresenta e discute os resultados obtidos, utilizando a primeira versão de software desenvolvida especialmente para este trabalho, bem como perspectivas para futuros trabalhos.<br>The 4πβ-γ coincidence method for absolute radionuclide activity measurement has been considered for many years as a primary standard in Nuclear Metrology, because of dependence on few observable quantities and high accuracy. The Laboratório de Metrologia Nuclear (LMN) Nuclear Metrology Laboratory , at Instituto de Pesquisas Energéticas e Nucleares (IPEN) Nuclear and Energy Research Institute , among its measurement techniques, uses the 4πβ-γ coincidence method. Recently a new technique known as software coincidence has been used, with many advantages over the conventional coincidence methodology. In order to update the methodologies for radionuclide standardizations, the LMN developed a new system based on the software coincidence technique, described in the present work. This system uses the same nuclear set up for beta and gamma detection. The new software coincidence electronics uses a National Instruments (NI) acquisition card connected to a microcomputer and, through a connection panel, to the nuclear detection set up. The card configuration and controlling is accomplished by software using the LabVIEW, a NI proprietary product. This system records into disk files all the amplitudes and occurrence times for beta and gamma detected pulses. A suitable software was developed (the coincidence analysis program) to process the recorded data in order to obtain beta, gamma and coincidence counts and perform calculation of the radioactive source activity. The work also presents and discusses the results obtained with the first version of the coincidence analysis program, as well as perspectives for future works.
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Degrelle, Deborah. "Caractérisation numérique de la technique de spectrométrie gamma par simulation Monte-Carlo. Application à la datation d'échantillons envrionnementaux." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD004/document.
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Caractérisation numérique de la technique de spectrométrie gamma par simulation Monte-Carlo : Application à la datation d'échantillons environnementaux.Résumé :Afin d'optimiser la détermination de l'activité d'échantillons environnementaux, l'étalonnage en efficacité de la chaîne spectrométrique se doit d'être de bonne qualité. Le travail de cette thèse consiste à rassembler les problématiques principales : les phénomènes d'auto-absorption et de coïncidence. Ces effets sont traités par métrologie et simulation Monte-Carlo (MCNP6), impliquant la bonne modélisation préalable de nos détecteurs. Le problème d'auto-absorption est dominant lorsque le standard utilisé pour l'étalonnage en efficacité a des caractéristiques physico-chimiques différentes des échantillons. Un étalonnage numérique semble plus approprié et nous l'appliquons à une archive sédimentaire du lac de Longemer (France). Nous proposons une méthode nouvelle se basant sur une mesure expérimentale ajustée numériquement afin de déterminer le coefficient d'atténuation massique des échantillons. Il est alors possible de remonter à une composition chimique fictive qui permettra d'utiliser la simulation Monte-Carlo pour réaliser l'étalonnage. Ainsi, à 59,54 keV la correction de l'auto-absorption peut atteindre 24 %. Les phénomènes de coïncidence peuvent également être corrigés par simulation. Le logiciel ETNA permet cette correction mais ne permet pas la modélisation d'un détecteur puits. Dans le but de corriger l'efficacité de notre détecteur puits, possédant une géométrie propice aux coïncidences, nous utilisons le transfert de rendement qui lui est adaptable pour n'importe quelle géométrie. Les résultats par cette méthode sont validés par MCNP6 et Génie 2000 sur les énergies principales du 214Bi<br>In order to improve the determination of environmental samples activity, the detector efficiency calibration must be reliable. These studies deal with the main issues in gamma-ray spectrometry: the self-absorption and the true coincidence summing effects (TCS). These phenomena are studied by metrology and Monte-Carlo simulation (MCNP6) that imply the faithful of our detector models in relation to the experimental device. The self-absorption problem is the main one when the used standard for efficiency calibration has not the same physical and chemical characteristics than samples. A numerical calibration seems to be more suitable and we apply it for Longemer lake archives (France). A new method is proposed where an experimental measurement is processed through numerical simulations to determine the mass attenuation coefficient of the samples. It makes it possible to define a virtual chemical composition to use Monte-Carlo simulation. Then the numerical calibration at 59.54 keV gives a 24% self-absorption correction. The TCS problems can also be corrected by simulation. The ETNA software can determine this correction but it doesn’t make the well type detector model possible, with a geometry conducive to TCS effects. With the aim of correcting the efficiency of our well detector, the efficiency transfer, which can be adjusted to any device, is used. The results with this method are validated by MCNP6 and Genie 2000 software on the main lines of 214Bi
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CORREA, GUSTAVO P. "Aplicação do Método de Monte Carlo no estudo da atividade obtida em sistema de coincidências 4π(β,EC)-γ pelo Método da Discriminação com reposição". reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26384.
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Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T12:55:19Z
No. of bitstreams: 0<br>Made available in DSpace on 2016-06-22T12:55:19Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado em Tecnologia Nuclear)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Júnior, Felisberto Alves Ferreira. "Medidas das seções de choque térmicas e integrais de ressonância das reações 34S(n,)35S e 42K(n,)43K - Aperfeiçoamento por simulação de Monte Carlo." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-13032013-103136/.
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Amostras de nitrato de potássio e enxofre natural foram irradiadas no núcleo do reator de pesquisas IEA-R1 do Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, operando entre 3,5 e 5 MW de potência, para determinar as secções de choque térmicas e integrais de ressonância das reações 34S(n,)35S e 42K(n,)43K. O fluxo de nêutrons foi monitorado com ligas ouro-alumínio. As atividades induzidas nos alvos de ouro-alumínio e nitrato de potássio foram medidas com um detector semicondutor de germânio hiper puro; as atividades dos alvos de enxofre foram determinadas com um sistema de coincidências 4\\pi\\beta - \\gamma. Os efeitos de depressão de fluxo, autoblindagem e autoabsorção nos alvos foram corrigidos com base em simulações com o método de Monte Carlo por meio do programa MCNP. O programa PENELOPE, também baseado no método de Monte Carlo, foi modificado para simular o comportamento do sistema de coincidências 4\\pi\\beta - \\gamma. O formalismo de Westcott e o método da razão de cádmio foram usados para determinar os fluxos de nêutrons térmicos e epitérmicos, assim como as secções de choque térmicas e integrais de ressonância de ambos nuclídeos. Foi efetuado um tratamento estatístico das incertezas envolvidas e determinadas as covariâncias entre os resultados, incluindo aquelas decorrentes das incertezas do padrão de referência (ouro). As reações 34S(n,)35S e 42K(n,)43K apresentaram, respectivamente, seções de choque térmicas de 228(14) mb e 44,8(9) b, e integrais de ressonância de 144(6) mb e 1635(75) b. Estes resultados são incompatíveis com aqueles obtidos com cálculos teóricos. A seção de choque térmica da reação 34S(n,)35S concorda com valores obtidos por outros autores, dentro das incertezas experimentais.<br>Samples of potassium nitrate and natural sulphur were irradiated in the IPEN/CNEN-SP IEA-R1 research reactor core, operating between 3.5 and 5 MW, to determine the thermal neutron cross sections and resonance integrals of 34S(n,)35S and 42K(n,)43K reactions. The neutron flux was monitored with gold-aluminium alloy. The activities induced in targets of gold-aluminium and potassium nitrate were measured with a high purity germanium detector. Sulphur targets activities were determined with a 4\\pi\\beta-\\gamma coincidences system by the tracer method. Flux depression, self-shielding and self-absorption in the targets was evaluated by simulations using the MCNP software. The PENELOPE software, also based on Monte Carlo method, was modified to simulate the behavior of the 4\\pi\\beta-\\gamma coincidence system. The Westcott formalism and the cadmium ratio method were used to determine epithermal and thermal neutrons flux as well as the thermal cross sections and resonance integrals of both nuclides. A statistical analysis of the uncertainties was performed and the covariance between the results was determined, including those arising from the uncertainties of the gold reference standard. The results were compared with experimental values and theoretical predictions obtained by other authors. The 34S(n,)35S and 42K(n,)43K reactions had, respectively, thermal cross sections of 228(14) mb and 44.8(9) b, and integral resonances of 144(6) mb and 1635(75) b. These results are incompatible with the obtained with theoretical calculations. The 34S(n,)35S reaction thermal cross section agrees with values obtained by other authors, within the experimental uncertainties.
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Tomas, Nemeš. "Апсолутно одређивање активности гама емитера помоћу једног детектора". Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=94841&source=NDLTD&language=en.
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Испитана је тачност методе мерењаапсолутне активности гама емитера помоћу једноггама спектрометра на већим брзинама бројања. Уоквиру истраживања нађен је једноставанпоступак за корекцију спектралних података наслучајне коинциденције. Принцип коинцидентне технике и корекцијесумарног врха и врхова пуне енергије помоћуврхова у спектру насталим само услед случајнихкоинциденција примењен је на радиоизотопе саједноставном и веома сложеном шемом. Изведенесу једноставне формуле за мерења активности са ибез корекције на ефективне угаоне корелације укојима фигуришу подаци само из једног гамаспектра чиме је постигнута знатна једноставност утехници мерења. Резултати овог истраживања показали су дасе активност двофотонских гама емитера можеизмерити помоћу HPGe детектора и дигиталнеспектроскопске јединице са тачношћу испод 1% наразним брзинама бројања само помоћу једногспектра. Резултати за изотопе са сложеном шемомдобијени једноставном техником указују да сетехника може применити на рутинска мерења гдегрешка не превазилази 10%<br>Ispitana je tačnost metode merenjaapsolutne aktivnosti gama emitera pomoću jednoggama spektrometra na većim brzinama brojanja. Uokviru istraživanja nađen je jednostavanpostupak za korekciju spektralnih podataka naslučajne koincidencije. Princip koincidentne tehnike i korekcijesumarnog vrha i vrhova pune energije pomoćuvrhova u spektru nastalim samo usled slučajnihkoincidencija primenjen je na radioizotope sajednostavnom i veoma složenom šemom. Izvedenesu jednostavne formule za merenja aktivnosti sa ibez korekcije na efektivne ugaone korelacije ukojima figurišu podaci samo iz jednog gamaspektra čime je postignuta znatna jednostavnost utehnici merenja. Rezultati ovog istraživanja pokazali su dase aktivnost dvofotonskih gama emitera možeizmeriti pomoću HPGe detektora i digitalnespektroskopske jedinice sa tačnošću ispod 1% naraznim brzinama brojanja samo pomoću jednogspektra. Rezultati za izotope sa složenom šemomdobijeni jednostavnom tehnikom ukazuju da setehnika može primeniti na rutinska merenja gdegreška ne prevazilazi 10%<br>It has been investigated the accuracy of absoluteactivity measurement of gamma emitters with a singlegamma spectrometer at higher count rates. In thisresearch it has been found relatively simple procedurefor random summing correction of spectral data.Principle of coincidence technique and randomsumming correction of sum peaks and full energypeaks using pile up peaks is applied to measureabsolute activity of simple and complicated decayscheme radioisotopes. Simple equations were deducedfor absolute activity measurements with and withoutcorrection for effective angular correlations. Variablesin these equations are spectral data only. Greatsimplicity is achieved in coincidence technique ofabsolute activity measurement.It was shown that absolute activity ofradioisotopes emitting simultaneously two gammaphotons can be measured with accuracy below 1% athigh count rates using HPGe detector and DSPspectroscopy unit. Measurements of complicateddecay scheme radioisotopes shown that simpletechnique is able to bring satisfactory results withaccuracies below 10%
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Escudeiro, Rafael. "Vida-média do estado isomérico 7(-) do núcleo ímpar-ímpar 68Ga." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-23052018-154050/.
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Estados Nucleares isoméricos são estados que decaem com vidas-médias longas ( T1/2 > 10 ns) e revelam, em geral, uma grande mudança no momento angular no seu decaimento, um pequeno elemento de matriz ou uma baixa energia de transição. Através da medida da vida-média de estados nucleares é possível obter informações sobre a função de onda desse estado, representando um teste rigoroso para modelos nucleares. Neste trabalho foi utilizado um sistema desenvolvido no Laboratório Aberto de Física Nuclear (LAFN) da Universidade de São Paulo chamado SIStema para Medida de Estados Isoméricos (SISMEI), que utiliza coincidência atrasada entre partículas evaporadas numa reação nuclear e raios gama emitidos pelo estado isomérico. O SISMEI consiste de cintiladores plásticos para detecção das partículas, detectores de germânio hiperpuro (HPGe) e iodeto de sódio (NaI(Tl)) para raios gama, associados a uma eletrônica de coincidência, instalado no acelerador Pelletron (8UD) do LAFN. Neste trabalho, realizou-se um experimento para medir o estado isomérico 7(-) (E = 1229,87(4) keV) do 68Ga. A tomada de dados durou cerca de 80 horas com uma taxa de eventos de aproximadamente 80000 contagens por hora. O resultado obtido foi T 1/2 = 60, 8(11) ns, que é compatível com os resultados experimentais de outros trabalhos, porém, mais preciso. A estrutura desse núcleo foi calculada através do Modelo de Camadas em Larga Escala considerando-se duas interações residuais diferentes FPG e JUN45; os resultados foram comparados entre si, juntamente com os valores obtidos em outros trabalhos. Os cálculos realizados com o Modelo de Camadas reproduziram relativamente bem a energia e a ordem dos estados excitados do 68Ga, a interação FPG conseguiu descrever melhor a probabilidade de transição quadrupolar elétrica B(E2) diretamente ligada à vida-média do estado.<br>Isomeric nuclear states are nuclear states which decay with long lifetimes (T1/2 > 10 ns); their study generally reveals, a large change in angular momentum in its decay, a small matrix element or a small transition energy. By measuring lifetimes of isomeric states it is possible to obtain information about this states wave function, being a robust test for nuclear models. In this work, a system developed at the Laboratório Aberto de Fsica Nuclear (LAFN) of University of São Paulo called System for the Measurement of Isomeric States (SISMEI) was utilized. Delayed coincidence between evaporated particles in a nuclear reaction and the delayed gamma-rays emitted from the isomeric state was used to measure lifetimes. SISMEI is composed of plastic scintillators for particle detection, hiperpure germanium detectors (HPGe) and sodium iodide (NaI(Tl)) for gamma-ray detection, coupled to a coincidence system, located on 30A beam line of the Pelletron (8UD) accelerator - LAFN. In the present work, an experiment to measure the 7 (-) (E = 1229.87(4) keV) isomeric state of 68Ga was performed. The experiment took about 80 hours with an event rate of about 80000 counts per second. The measured value was T 1/2 = 60.8(11) ns, which is compatible, but more accurate, with experimental results of other authors. The nuclear structure of this nucleus was calculated with the Large Scale Shell Model by using two different residual interactions FPG and JUN45; the results were compared with the known values. The structure calculated with LSSM described the energy states and the order of excited states relatively well; the FPG interaction was capable to describe better the quadrupolar electrical transition probability B(E2), which is direct related to predicting the state lifetime.
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BRANCACCIO, FRANCO. "Metodologia de aquisição de dados e análise por software, para sistemas de coincidências 4pß-? e sua aplicação na padronização de radionuclídeos, com ênfase em transições metaestáveis." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10559.
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Made available in DSpace on 2014-10-09T12:41:56Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:04:33Z (GMT). No. of bitstreams: 0<br>Tese (Doutoramento)<br>IPEN/T<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Ross, Timothy J. "A study of gadolinium isotopes around N = 90 utilizing particle-gamma coincidences." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582858.
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Particle-γ coincidence data can be used as a strong tool for studying low energy nuclear structure. The STARS-LIBERACE array at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory was used to study gadolinium isotopes straddling the N = 90 shape change region. A 25 Me V proton beam was impinged upon 154Gd and 158Gd targets. The gadolinium isotopes 152,153,154,156,157,158Gd were studied following the (p,p'), (p,d) and (p,t) neutron transfer reactions. The primary focus of this work is to study the structure of and identify single- neutron quasi-particle states in the odd N Gd nuclei following the (p, d) reactions. Nu- merous new levels are observed in both 153Gd and 157 Gd and multiple new, rays have been observed and associated with these and other previously known levels. A large excitation energy gap between approximately 500 keV and 1500 keV is observed in the level schemes of both nuclei where very few states are populated. This gap appears to demonstrate the persisting influence of the N = 64 spherical sub-shell closure to inter- mediate deformations. It is striking that such an effect is apparent when probed from so far above (i.e. ~ 30 neutrons away). The secondary focus of this work is upon the angular momentum transferred to the statistical continuum region of these nuclei via different light ion transfer reactions, i.e. between approximately 2 Me V and the neutron separation energy. The angular momen- tum transferred via (p,d) and (p,t) reactions populating 157 Gd and 156Gd respectively was measured using two independent techniques. The first technique involves studying the ,-ray decay path within the residual nucleus, the second technique involves measur- ing the angular distribution of the light ions following the reaction. The two techniques are in good agreement and appear to verify each other. The measured angular momen- tum transferred via the (p,t) reaction is measured to be a distribution centered around ΔL = 4 - 5 h. The angular momentum transferred via the (p,d) reaction is slightly lower and is closer to ΔL = 4 h.
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Hawcroft, Deborah. "A search for superdeformed and hyperdeformed states in '2'2'2Th and '2'3'2U." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367227.
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KUZNETSOVA, MARIA. "Medida absoluta da atividade de 14C pelos métodos CIEMAT/NIST, TDCR e em sistema de coincidência 4πβ-γ". reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27138.
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Submitted by Maria Eneide de Souza Araujo (mearaujo@ipen.br) on 2017-03-10T16:38:03Z
No. of bitstreams: 0<br>Made available in DSpace on 2017-03-10T16:38:03Z (GMT). No. of bitstreams: 0<br>Neste trabalho foi padronizada uma solução de 14C emissor beta puro com energia máxima de 156 keV, por meio de três diferentes métodos: CIEMAT/NIST e TDCR (triple-to-double coincidence ratio) em sistemas de cintilação líquida e pelo método do traçador, em sistema de coincidências 4πβ-γ. O sistema de cintilação líquida TRICARB, equipado com dois tubos fotomultiplicadores, foi usado para aplicação do método CIEMAT/NIST, usando um padrão de 3H emissor beta puro com energia máxima de 18,7 keV como traçador de eficiência. O sistema de cintilação líquida HIDEX 300SL, equipado com três tubos fotomultiplicadores, foi utilizado para as medidas pelo método TDCR. As amostras de 14C e 3H, medidas nos sistemas de cintilação foram preparadas usando-se três coquetéis cintiladores comerciais Ultima Gold, Optiphase Hisafe3 e InstaGel-Plus a fim de comparar seu desempenho nas medidas.Todas as amostras foram preparadas com 15 mL de coquetel cintilador, em frascos de vidro com baixa concentração de potássio. Alíquotas conhecidas de solução radioativa foram depositadas nos coquetéis cintiladores. Para a variação do parâmetro indicador de quenching, foram utilizados: um carregador de nitro metano e 1 mL de água destilada. Para a padronização pelo método do traçador no sistema de coincidências 4πβ-γ, foi utilizado 60Co como emissor beta gama. As medidas foram feitas no sistema de coincidências por software SCS, usando discriminação eletrônica para alterar a eficiência beta. O comportamento da curva de extrapolação foi predito por meio do código Esquema, que utiliza a técnica de Monte Carlo. Os resultados da atividade da solução de 14C obtida pelos três métodos utilizados mostraram uma boa concordância dentro da incerteza experimental.<br>Dissertação (Mestrado em Tecnologia Nuclear)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Hallberg, Ludvig. "Analysis of triple gamma coincidences for studies of the level structure of nuclei in the 100-Sn region." Thesis, Uppsala universitet, Kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325862.
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In this master thesis a thorough analysis of data collected in an experiment performed at the JYFL accelerator laboratory in Finland using a reaction with a 47-Ti beam on a 58-Ni target is presented. The prompt emitted gamma rays from the fusion-evaporation products were detected in the gamma-ray spectrometer JUROGAM II, while the recoils were detected in the GREAT spectrometer. The main aim of this work was to use triple gamma-ray coincidences to find out if it is possible to discover new levels and transitions in proton-rich nuclides such as 103-Sn and 101-In. A recoil triggered gamma-cube of coincident gamma rays was constructed and analyzed with the program levit8r from the Radware software package. From an intensity estimation of the data it was concluded that 102-Ag was the strongest reaction channel and emission of 3-7 particles in the fusion-evaporation reaction was favoured. By analyzing peaks in double-gated spectra of the gamma-cube, three new levels and seven new gamma-ray transitions up to an excitation energy of 8644 keV and an angular momentum of 22 h were proposed as a continuation of rotational band B3 published in a recent article on 102-Ag. From plots of the alignment of the newly proposed transitions no band crossing was observed, just a smooth continuation of the band. The efficiency of the charged particle detector, UoYTube, was deduced to be about 66% for proton detection, while the probability to detect one random proton was about 10%.
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Kristina, Bikit. "Promene nuklearnih spektara pod dejstvom kosmičkog zračenja." Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2015. https://www.cris.uns.ac.rs/record.jsf?recordId=94514&source=NDLTD&language=en.
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U ovoj disertaciji su prikazani rezultati kompleksnih istraživanja uticajakosmičkog zračenja na nuklearne spektre na nivou mora.Utvrđivanje specifičnih vremenskih intervala u vremenskom spektru,kojima odgovaraju tačno određene grupe događaja indukovanekosmičkim mionima, omogućava adekvatno odbacivanje ometajućihdogađaja u željenim energetskim oblastima detektovanih spektara, priantikoincidentnom režimu rada ultraniskofonskih sistema. U prvomeksperimentu prikazanom u ovoj disertaciji, istraživana je mogućnostvremenskog razlaganja detektovanih događaja, pomoću koincidentnogsistema u čijem sklopu se nalazi HPGe detektor i plastični scintilator, upovršinskoj laboratoriji. Ustanovljeno je da se promptni i zakasnelikoincidentni događaji između plastičnog “veto” detektora igermanijumskog detektora mogu jasno razdvojiti u dve grupe, za oko100 ns. Dodatno, zakočno zračenje i anihilacioni događaji mogu serazdvojiti u vremenu od (n,n’) događaja, iako svi ovi događaji pripadajugrupi zakasnelih događaja. Takođe, registrovani su i značajno zakasnelianihilacioni događaji, koji nastaju usled raspada zaustavljenih pozitivnihmiona.Drugi eksperiment prikazan u ovoj disertaciji baziran je na ultra-niskofonskom HPGe spektrometru relativne efikasnosti 100%.Dodatkom dva plastična scintilatora i brzo-sporog koincidentnog kola,istraživani su koincidentni događaji između plastičnih scintilatora iHPGe spektrometra. Ovaj spektrometarski sistem MIREDO <em>(MuonInduced Rare Event Dynamic Observatory</em>) prvenstveno je namenjenproučavanju procesa indukovanih kosmičkim mionima u različitimmaterijalima. Analiza ovakvih interakcija može biti od značaja za ultra-niskofonske eksperimente. Rezultati dobijeni za tri ispitivana materijala,pakovana u<em> Marinelli</em> sud, prezentovani su i diskutovani.U trećem eksperimentu prikazanom u ovoj disertaciji ispitan jepotencijalni uticaj solarnih neutrina na izmerenu brzinu radioaktivnograspada, merenjem varijacija u brzini brojanja<sup>3</sup>H metodom tečnog scintilacionog brojanja. Korišćenjem sofisticiranog tečnog scintilacionog spektrometra <em> Quantulus</em> ustanovljeno je da na merenjevisokoenergetskog dela <sup>3</sup>H spektra može značajno uticati nestabilnostinstrumenta. Oscilatorni karakter izmerenog visokoenergetskog dela<sup>3</sup>H spektra je registrovan, ali sa veoma malom amplitudom (manjom od0.5%), koja se ne može jednostavno objasniti samo nestabilnošćuinstrumenta. Kada je meren ukupan <sup>3</sup>H spektar, nisu nađene značajnevarijacije u brzini brojanja.Već duže vreme je poznato da je niskoenergetsko gama zračenjekontinualne distribucije prisutno na otvorenom prostoru, u vazduhu napovršini Zemlje. U prethodnim istraživanjima pretpostavljano je da ovozračenje potiče skoro isključivo od gama fotona koji su emitovani usledprirodne radioaktivnosti i potom rasejani u nazad od strane vazduhaiznad zemlje. U četvrtom eksperimentu prikazanom u ovoj disertacijipokazano je da je ovo zračenje (u energetskom regionu 30 keV-300keV), sa maksimumom na oko 90 keV, u značajnoj meri proizvedenokosmičkim zračenjem, sa fluksom fotona od oko 3000 m<sup>-2</sup>s<sup>-1</sup>. Takođe,ustanovljeno je da dozama opšte populacije doprinosi ovo sveprisutnoniskoenergetsko gama zračenja kosmičkog porekla, zajedno saodgovarajućim fluksom niskoenergetskih elektrona i da ove komponenteukupnih doza indukovanih kosmičkim zračenjem na nivou mora nisuzanemarljive.<br>In this dissertation results of complex research on cosmic-ray impact on nuclear spectra at sea level are shown. The appropriate selection of coincidence time interval in low-background experiments that are based on the rejection of anticoincidence background events is very important for reducing the influence of cosmic-ray muons on acquired spectral data. In the first experiment presented in this dissertation, performed by the coincidence system of an HPGe detector and a plastic detect or in a surface laboratory, the time resolution of the detected events is explored. It is found that the prompt and delayed coincidence events between a plastic veto detector and a Ge detector can be sharply divided for approximately 100 ns in two groups. In addition, the bremsstrahlung and annihilation events can be time-resolved from the (n,n’) events, although all of these events belong to the group of delayed events. Also, substantially delayed annihilation events, which are caused by the decays of stopped positive muons, were detected.The second experiment shown in this dissertation is based on the 100% relative efficiency ultra-low-background HPGe spectrometer. With the addition of two plastic scintillators and a fast-slow coincidence circuit, the coincidence events between the plastic detectors and the HPGe spectrometer have been investigated. This MIREDO (Muon Induced Rare Event Dynamic Observatory) spectrometer system is primarily developed for the study of cosmic muon induced processes in different materials. Exploration of such interactions can be important for ultra-low background experiments. Results derived for three samples, placed in a Marinelli beaker, are presented and discussed.In third experiment shown in this dissertation, the potential influence of solar neutrinos on measured decay rate is investigated by the liquid scintillation measurement of the count rate variations of <sup>3</sup>H. Making use of the sophisticated Quantulus liquid scintillation spectrometer, it is found that the measurement of the high-energy tail of <sup>3</sup>H spectrum may be significantly influenced by instrumental instability. The oscillatory behavior of measured high-energy tail of <sup>3</sup>H spectrum is registered, but with very small amplitude (less than 0.5%), which cannot be easily explained only by instrumental instability. When the total <sup>3</sup>H spectrum was measured, no significant variations in the count rate were found. For a long time, it has been known that low-energy continuous gamma radiation is present in open air at the Earth’s surface. In previous investigations it was assumed that this radiation is produced almost exclusively by gamma photons emitted due to the natural radioactivity, which are backscattered by air above ground. In the fourth experiment presented in this dissertation, it is shown that significant amount of this radiation (related to energy region 30 keV-300 keV) that peaks at about 90 keV, is produced by cosmic-rays, with the photon flux of about 3000 m<sup>-2</sup>s<sup>-1</sup>. Also, it is found that the contribution of this omnipresent low energy gamma radiation of cosmic-ray origin, including the corresponding low-energy electron flux, to the doses of general population are non-negligible components of overall doses induced by cosmic rays near sea level.
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Aliaga, Varea Ramón José. "Development of a data acquisition architecture with distributed synchronization for a Positron Emission Tomography system with integrated front-end." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/63271.
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[EN] Positron Emission Tomography (PET) is a non-invasive nuclear medical imaging modality that makes it possible to observe the distribution of metabolic substances within a patient's body after marking them with radioactive isotopes and arranging an annular scanner around him in order to detect their decays. The main applications of this technique are the detection and tracing of tumors in cancer patients and metabolic studies with small animals.
The Electronic Design for Nuclear Applications (EDNA) research group within the Instituto de Instrumentación para Imagen Molecular (I3M) has been involved in the study of high performance PET systems and maintains a small experimental setup with two detector modules. This thesis is framed within the necessity of developing a new data acquisition system (DAQ) for the aforementioned setup that corrects the drawbacks of the existing one. The main objective is to define a DAQ architecture that is completely scalable, modular, and guarantees the mobility and the possibility of reusing its components, so that it admits any extension of modification of the setup and it is possible to export it directly to the configurations used by other groups or experiments. At the same time, this architecture should be compatible with the best possible resolutions attainable at the present instead of imposing artificial limits on system performance. In particular, the new DAQ system should outperform the previous one.
As a first step, a general study of DAQ arquitectures is carried out in the context of experimental setups for PET and other high energy physics applications. On one hand, the conclusion is reached that the desired specifications require early digitization of detector signals, exclusively digital communication between modules, and the absence of a centralized trigger. On the other hand, the necessity of a very precise distributed synchronization scheme between modules becomes apparent, with errors in the order of 100 ps, and operating directly over the data links. A study of the existing methods reveals their severe limitations in terms of achievable precision. A theoretical analysis of the situation is carried out with the goal of overcoming them, and a new synchronization algorithm is proposed that is able to reach the desired resolution while getting rid of the restrictions on clock alignment that are imposed by virtually all usual schemes. Since the measurement of clock phase difference plays a crucial role in the proposed algorithm, extensions to the existing methods are defined and analyzed that improve them significantly. The proposed scheme for synchronism is validated using commercial evaluation boards.
Taking the proposed synchronization method as a starting point, a DAQ architecture for PET is defined that is composed of two types of module (acquisition and concentration) whose replication makes it possible to arrange a hierarchic system of arbitrary size, and circuit boards are designed and commissioned that implement a realization of the architecture for the particular case of two detectors. This DAQ is finally installed at the experimental setup, where their synchronization properties and resolution as a PET system are characterized and its performance is verified to have improved with respect to the previous system.<br>[ES] La Tomografía por Emisión de Positrones (PET) es una modalidad de imagen médica nuclear no invasiva que permite observar la distribución de sustancias metabólicas en el interior del cuerpo de un paciente tras marcarlas con isótopos radioactivos y disponer después un escáner anular a su alrededor para detectar su desintegración. Las principales aplicaciones de esta técnica son la detección y seguimiento de tumores en pacientes con cáncer y los estudios metabólicos en animales pequeños.
El grupo de investigación Electronic Design for Nuclear Applications (EDNA) del Instituto de Instrumentación para Imagen Molecular (I3M) ha estado involucrado en el estudio de sistemas PET de alto rendimiento y mantiene un pequeño setup experimental con dos módulos detectores. La presente tesis se enmarca dentro de la necesidad de desarrollar un nuevo sistema de adquisición de datos (DAQ) para dicho setup que corrija los inconvenientes del ya existente. En particular, el objetivo es definir una arquitectura de DAQ que sea totalmente escalable, modular, y que asegure la movilidad y la posibilidad de reutilización de sus componentes, de manera que admita cualquier ampliación o alteración del setup y pueda exportarse directamente a los de otros grupos o experimentos. Al mismo tiempo, se desea que dicha arquitectura no limite artificialmente el rendimiento del sistema sino que sea compatible con las mejores resoluciones disponibles en la actualidad, y en particular que sus prestaciones superen a las del DAQ instalado previamente.
En primer lugar, se lleva a cabo un estudio general de las arquitecturas de DAQ para setups experimentales para PET y otras aplicaciones de física de altas energías. Por un lado, se determina que las características deseadas implican la digitalización temprana de las señales del detector, la comunicación exclusivamente digital entre módulos, y la ausencia de trigger centralizado. Por otro lado, se hace patente la necesidad de un esquema de sincronización distribuida muy preciso entre módulos, con errores del orden de 100 ps, que opere directamente sobre los enlaces de datos. Un estudio de los métodos ya existentes revela sus graves limitaciones a la hora de alcanzar esas precisiones. Con el fin de paliarlos, se lleva a cabo un análisis teórico de la situación y se propone un nuevo algoritmo de sincronización que es capaz de alcanzar la resolución deseada y elimina las restricciones de alineamiento de reloj impuestas por casi todos los esquemas usuales. Dado que la medida de desfase entre relojes juega un papel crucial en el algoritmo propuesto, se definen y analizan extensiones a los métodos ya existentes que suponen una mejora sustancial. El esquema de sincronismo propuesto se valida utilizando placas de evaluación comerciales.
Partiendo del método de sincronismo propuesto, se define una arquitectura de DAQ para PET compuesta de dos tipos de módulos (adquisición y concentración) cuya replicación permite construir un sistema jerárquico de tamaño arbitrario, y se diseñan e implementan placas de circuito basadas en dicha arquitectura para el caso particular de dos detectores. El DAQ así construído se instala finalmente en el setup experimental, donde se caracterizan tanto sus propiedades de sincronización como su resolución como sistema PET y se comprueba que sus prestaciones son superiores a las del sistema previo.<br>[CAT] La Tomografia per Emissió de Positrons (PET) és una modalitat d'imatge mèdica nuclear no invasiva que permet observar la distribució de substàncies metabòliques a l'interior del cos d'un pacient després d'haver-les marcat amb isòtops radioactius disposant un escàner anular al seu voltant per a detectar la seua desintegració. Aquesta tècnica troba les seues principals aplicacions a la detecció i seguiment de tumors a pacients amb càncer i als estudis metabòlics en animals petits.
El grup d'investigació Electronic Design for Nuclear Applications (EDNA) de l'Instituto de Instrumentación para Imagen Molecular (I3M) ha estat involucrat en l'estudi de sistemes PET d'alt rendiment i manté un petit setup experimental amb dos mòduls detectors. Aquesta tesi neix de la necessitat de desenvolupar un nou sistema d'adquisició de dades (DAQ) per al setup esmentat que corregisca els inconvenients de l'anterior. En particular, l'objectiu és definir una arquitectura de DAQ que sigui totalment escalable, modular, i que asseguri la mobilitat i la possibilitat de reutilització dels seus components, de tal manera que admeta qualsevol ampliació o alteració del setup i pugui exportar-se directament a aquells d'altres grups o experiments. Al mateix temps, es desitja que aquesta arquitectura no introduisca límits artificials al rendiment del sistema sinó que sigui compatible amb les millors resolucions disponibles a l'actualitat, i en particular que les seues prestacions siguin superiors a les del DAQ instal.lat amb anterioritat.
En primer lloc, es porta a terme un estudi general de les arquitectures de DAQ per a setups experimentals per a PET i altres aplicacions de física d'altes energies. Per una banda, s'arriba a la conclusió que les característiques desitjades impliquen la digitalització dels senyals del detector el més aviat possible, la comunicació exclusivament digital entre mòduls, i l'absència de trigger centralitzat. D'altra banda, es fa palesa la necessitat d'un mecanisme de sincronització distribuïda molt precís entre mòduls, amb errors de l'ordre de 100 ps, que treballi directament sobre els enllaços de dades. Un estudi dels mètodes ja existents revela les seues greus limitacions a l'hora d'assolir aquest nivell de precisió. Amb l'objectiu de pal.liar-les, es duu a terme una anàlisi teòrica de la situació i es proposa un nou algoritme de sincronització que és capaç d'obtindre la resolució desitjada i es desfà de les restriccions d'alineament de rellotges imposades per gairebé tots els esquemes usuals. Atès que la mesura del desfasament entre rellotges juga un paper cabdal a l'algoritme proposat, es defineixen i analitzen extensions als mètodes ja existents que suposen una millora substancial. L'esquema de sincronisme proposat es valida mitjançant plaques d'avaluació comercials.
Prenent el mètode proposat com a punt de partida, es defineix una arquitectura de DAQ per a PET composta de dos tipus de mòduls (d'adquisició i de concentració) tals que la replicació d'aquests elements permet construir un sistema jeràrquic de mida arbitrària, i es dissenyen i implementen plaques de circuit basades en aquesta arquitectura per al cas particular de dos detectors. L'electrònica desenvolupada s'instal.la finalment al setup experimental, on es caracteritzen tant les seues propietats de sincronització com la seua resolució com a sistema PET i es comprova que les seues prestacions són superiors a les del sistema previ.<br>Aliaga Varea, RJ. (2016). Development of a data acquisition architecture with distributed synchronization for a Positron Emission Tomography system with integrated front-end [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63271<br>TESIS<br>Premiado
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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.<br>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.<br>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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Stefano, Roberto de. "Détection et caractérisation de matières nucléaires par interrogation et activation neutronique." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALY028.
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Ce travail concerne la détection de matières nucléaires par interrogation neutronique pulsée pour l’inspection des conteneurs maritimes ou la caractérisation des déchets. Pour la 1ère partie, elle fait suite à des travaux sur l’interrogation neutronique continue avec des neutrons rapides de 14 MeV produits par la réaction deutérium-tritium (DT), avec la technique dite de la particule associée, qui présentait des limitations pour les marchandises riches en hydrogène, notamment organiques. Pour pallier cette faiblesse, cette thèse étudie une interrogation avec des neutrons thermiques entre les impulsions d’un générateur DT pulsé. C’est la première fois qu’une telle mesure est effectuée avec des scintillateurs en plastique PVT sans capacité de discrimination neutron - gamma ni dopage avec un absorbant neutronique. Des mesures de coïncidences entre neutrons et rayonnements gamma prompts de fission induites permettent d’isoler le signal utile dans un important bruit de fond, dû notamment aux captures radiatives. Par ailleurs, la détection des rayonnements gamma retardés de fissions induites, aussi bien entre les impulsions du générateur qu’en post-irradiation, offre une possibilité de confirmer la présence de matière nucléaire et renforce ainsi les performances de la méthode. Pour la 2ème partie sur la caractérisation des déchets, les rayonnements gamma retardés des fissions induites par un générateur DT pulsé sont détectés avec un détecteur germanium hyper pur de haute résolution énergétique. Cette étude s’attache d’abord à valider le schéma de calcul avec la carte ACT (activation control card) du code de calcul Monte Carlo MCNP 6.1, par une comparaison avec des résultats expérimentaux. Ensuite, la faisabilité de la caractérisation de colis de déchets bétonnés de 870 litres est étudiée. La statistique de comptage du signal utile obtenue pour ce type de colis, très pénalisants en termes d’atténuation et par nature hétérogènes (déchets technologiques), n’est pas suffisante pour envisager une application industrielle mais cette étude a permis de dégager des perspectives intéressantes pour la caractérisation d’autres colis moins denses et volumineux<br>In the framework of homeland security and nuclear waste drum characterization, this work focused on the detection and characterization of nuclear materials by means of pulsed neutron interrogation. In the field of homeland security, pulsed neutron interrogation coupled do PVT plastic scintillators has been studied as a complementary method to the Associated Particle Technique (APT) studied in a former work to inspect cargo containers with fast tagged neutrons. The APT shows good performances to detect nuclear materials in metallic and ceramic cargo cover loads, but is poorly efficient when confronted to organic matrixes. In order to overcome this limit, this work investigates pulsed neutron interrogation to take advantage of neutrons thermalisation in the organic matrix between neutron generator pulses and to allow detecting prompt fission particles such as neutron and gamma rays in coincidences as a signature of nuclear materials presence. In addition, pulsed neutron interrogation offers the possibility to detect induced fission delayed gamma rays far from the neutron generator bursts, or in post-irradiation acquisitions, and strengthens the method. In the field of radioactive waste drums characterization, neutron activation analysis coupled to delayed gamma rays measurement applied to the characterization of a particular type of highly hydrogenated radioactive waste drum currently stored at CEA Cadarache is studied. A new numerical option called ACT (activation control card) validates the transport of induced fission delayed gamma rays in MCNP 6.1 transport code in order to apply delayed gamma rays measurement to the concerned radioactive waste drum. Although this technique shows poor performances to identify nuclear materials in the drum, some perspectives envisage studying other type of radioactive waste drums of smaller size
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Léguillon, Romain. "Triaxialité et isomèrisme à hauts spins dans les noyaux proches de la fermeture de couche N = 82." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00932123.
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L'existence de noyaux triaxiaux a fait l'objet d'un débat de longue date. La possibilité de la triaxialité mole et rigide a été proposée très tôt, et de nombreuses études théoriques et expérimentales ont été consacrées à ce phénomène intrigant. Plus récemment, deux marqueurs uniques de la triaxialité dans les noyaux ont été intensivement étudiés : le mouvement d'oscillation de l'axe de rotation (wobbling) et la chiralité dynamique. Ces types exotiques de mouvement ont été observées dans des régions spécifiques du tableau nucléaire : le mouvement d'oscillation dans les noyaux de Lu impair-pair avec A ~ 160, la chiralité principalement dans les noyaux impair-impair et pair-impair avec A ~ 130. Nous avons récemment étudié les noyaux de Nd à très hauts spins et identifié plusieurs bandes, qui ont été interprétées comme la manifestation de divers types de mouvement collectif : rotation suivant un axe incliné, rotation suivant les axes longs et courts, mouvement de wobbling et bandes chirales. Un autre phénomène révélé par nos résultats récents sur les noyaux de Nd avec seulement quelques trous neutroniques par rapport à la fermeture de couche N = 82, est la coexistence de forme. En effet, ces noyaux sont prévus pour avoir des isomères de hauts spins construis sur une forme sphérique, coexistant avec des bandes triaxiales, ou des formes très voire super-déformées . Ma thèse se compose de deux expériences. Tout d'abord, j'ai préparé, exécuté et analysé une expérience réalisée au " Research Center of Nuclear Physics " (RCNP) de l' Université d'Osaka . Cette expérience visait à étudier les isomères de hauts spins et à développer les schémas de niveaux des noyaux de 135La, 136La et 136Ba. Nous avons utilisé un faisceau radioactif de 17N de 80 MeV créé par la réaction directe de 18O sur une cible 9Be et sélectionné à l'aide d'un spectromètre achromatique. Le faisceau radioactif de 17N bombardait une cible de 124Sn de 20 mg/cm2 d'épaisseur pour produire les noyaux d'intérêt par une réaction de fusion-évaporation. Cette thèse présente les résultats obtenus pour le 135La, qui comprennent la construction et la discussion du schéma de niveau et la mesure de la durée de vie de deux isomères connus. La deuxième partie de la thèse consiste en l'analyse de deux expériences différentes réalisée en utilisant la même combinaison de faisceau-cible 48Ca + 96Zr à une énergie légèrement différentes et deux dispositifs expérimentaux différents, EUROBALL et JUROGAM II + RITU + GREAT, pour étudier les isotopes du néodyme de 138Nd à 141Nd. Mon travail a été axé sur les noyaux pair-pair de 138Nd et 140Nd, avec un accent particulier sur le 140Nd. La multitude de bandes de spin élevé observées dans ce noyau sont discutées dans le cadre du modèle " Cranked Nilsson - Strutinsky " (CNS) et du modèle " Tilted Axis Cranking " (TAC). Les bandes de hauts spins observées dans les noyaux de 138-141Nd sont toutes interprétées comme basées sur un minimum d'énergie associé à une déformation triaxiale. Elles représentent donc un fort soutien à l'existence de la forme nucléaire triaxiale stable à hauts spins. L'isomère de haut spin 27- a également été identifié dans le 140Nd qui, combinée avec l'isomère 20+ précédemment connu dans le même noyau va permettre d'extraire pour la première fois une valeur expérimentale de la différence d'énergie entre les orbitales πh11/2 et π(d5/2g7/2) à hauts spins.
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Horne, Steven Michael. "Advances in gamma-ray spectroscopy : compton suppression and gamma-gamma coincidence." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3287.
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This project aims to improve research in gamma-ray spectroscopy by using advanced detector systems. These systems are designed to reduce interference inherent in gamma-ray spectroscopy by rejecting Compton scattering events from high-energy gamma-rays, as well as look at cascading decays of gamma-rays through gamma-gamma coincidence counting. By combining these methods, one is able to lower detection limits for many elements than would otherwise be possible. This work also takes advantage of neutron activation analysis, which allows stable elements to be analyzed by activating them with neutrons, causing them to become unstable and decay with radioactive signatures. By analyzing these signatures, one is able to detect trace levels of elements with relatively small samples sizes (< 1g) and in a nondestructive manner.<br>text
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Ju, Y. D., and 朱亦丹. "The Coincidence Imaging on a Simulated Dual-Head Gamma Camera." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/37800516373695464281.
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碩士<br>國立陽明大學<br>放射醫學科學研究所<br>88<br>The gamma camera with dual-head coincidence imaging (DHCI) is widespread during last few years. This instrument has the characteristics of two imaging systems of conventional nuclear medicine: Anger camera and dedicated PET (positron emission tomography) scanner. DHCI system is a multipurpose system with low cost. So far we have limited knowledge on this innovative instrument. DHCI cannot be characterized in the same way on SPECT or PET . In this thesis, I try to use computer simulation to explore DHCI performance, and to evaluate feasibility of using computer simulation for instrument design and addressing some clinical issues.
In this study, we use computer program by Monte Carlo technique to simulate the gamma photons interaction with matter in imaging formation process, and to convert the detected photons to projection data format. Then we use 2-D image reconstruction to produce tomographic images of activity distribution. In this work, we setup some simple conditions to do simulation tests. The simulation is setup based on real imaging experiment, so that simulation results are meaningful.
We obtain simulation results on variable physical parameters such as spatial resolution, linearity, and various phantom images. From these results, we can understand the difference between simulation and real phantom studies. We also find the defects of the simulation tool, which has room for farther improvements.
Even through the simulation results now are not identical to phantom studies, they have the potential for simulating actual clinical imaging situations. If we can further improve the shortcomings, then we can make the simulated results match the real experimental results. We can enhance simulation performance by raising computing efficiency, do that computer simulation can be applied in instrument design and clinical study.
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Metwally, Walid A. "Investigation of coincidence techniques in prompt gamma neutron activation analysis." 2003. http://www.lib.ncsu.edu/theses/available/etd-05052003-231320/unrestricted/etd.pdf.
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Schreiber, Samuel Stuart. "Identification of the radionuclides in spent nuclear fuel that may be detected by Compton suppression and gamma-gamma coincidence methods." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-2701.
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The nuclides present in spent nuclear fuel are categorized according to their capacity for detection by Compton suppression or gamma-gamma coincidence methods. The fifty nuclides with the highest activities in spent fuel are identified, their decay schemes analyzed, and the best detection scheme for each is recommended.<br>text
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Han, Xiaogang. "Development of Monte Carlo code for coincidence prompt gamma-ray neutron activation analysis." 2005. http://www.lib.ncsu.edu/theses/available/etd-07072005-021728/unrestricted/etd.pdf.
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Ward, Rebecca Morgan. "Comparison of the phoswich and ARSA-type detectors for radioxenon detection." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-05-1016.
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The Comprehensive Nuclear Test Ban Treaty verification regime mandates atmospheric monitoring for the four radioxenon isotopes that are produced in high abundance in a nuclear explosion: [superscript 131m]Xe, [superscript 133m]Xe, [superscript 133g]Xe, and [superscript 135g]Xe. This mandate has driven the development of improved xenon detectors, including a phoswich detector, which has potential to replace the ARSA detector in the International Monitoring System. In this experiment, the four relevant radioxenon isotopes were produced through neutron activation and the phoswich detector was used to attain spectra from the gas. Spectral characteristics and resolution of the phoswich spectra were compared to an ARSA-type [beta]-[gamma] coincidence detector to perform an overall evaluation of the phoswich detector. The results indicated that spectral characteristics and resolutions for the phoswich were comparable to the ARSA-type detector, with slightly improved beta detection. As an additional test of the new detector's capabilities, a tailored spectrum designed to mimic a nuclear explosion signature was produced and analyzed with the detector.<br>text
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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.
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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.<br>text
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Haas, Derek Anderson 1981. "Production of [beta-gamma] coincidence spectra of individual radioxenon isotopes for improved analysis of nuclear explosion monitoring data." 2008. http://hdl.handle.net/2152/18097.
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Radioactive xenon gas is a fission product released in the detonation of nuclear devices that can be detected in atmospheric samples far from the detonation site. In order to improve the capabilities of radioxenon detection systems, this work produces [beta-gamma] coincidence spectra of individual isotopes of radioxenon. Previous methods of radioxenon production consisted of the removal of mixed isotope samples of radioxenon gas released from fission of contained fissile materials such as ²³⁵U. In order to produce individual samples of the gas, isotopically enriched stable xenon gas is irradiated with neutrons. The detection of the individual isotopes is also modeled using Monte Carlo simulations to produce spectra. The experiment shows that samples of [superscript 131m]Xe, ¹³³Xe, and ¹³⁵Xe with a purity greater than 99% can be produced, and that a sample of [superscript 133m]Xe can be produced with a relatively low amount of ¹³³Xe background. These spectra are compared to models and used as essential library data for the Spectral Deconvolution Analysis Tool (SDAT) to analyze atmospheric samples of radioxenon for evidence of nuclear events.<br>text