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As vidas-médias dos três primeiros níveis da banda-yrast I=2 construída sobre o estado h11/2- do núcleo de 135Pr, foram medidas, pela primeira vez, através da reação 121,123Sb(16O, 4n)133,135Pr, a 76 MeV, usando-se espectroscopia gama em conjunto com a técnica de medida da distância de recuo (RDM), no Laboratório PELLETRON, São Paulo, e TANDAR/CNEA, Buenos Aires, Argentina. Foram calculadas as probabilidades reduzidas de transição B(E2), com o objetivo de extrair informações sobre os parâmetros de deformação, os quais foram comparados às estimativas feitas pelos modelos teóricos para a região de massa A~130, como o modelo de um rotor triaxial mais quasi-partícula, o modelo geométrico e o TRS (\"Total Routhian Surface\"). Os valores experimentais das vidas-médias, dos B(E2) e dos parâmetros de deformação (B2, y) de 135Pr, foram comparados ao caroço de 134Ce, medido em [Hu77]. Os valores experimentais de Q0 obtidos para os três primeiros níveis da banda h11/2- de 135Pr, antes do backbending, são bastante parecidos aos do 134Ce. Cálculos teóricos para os dois núcleos, usando o programa TRS, forneceram resultados que estão em contraste com os experimentais. / Lifetimes of low-Iying states in I=2 bands built on the h11/2- state in the Z-odd nucleus 135Pr were measured by means of the 121,123Sb(16O,4n)133,135Pr reaction at a bombarding energy of 76 MeV, using in-beam gamma-ray spectroscopy together with the Doppler-Shift Recoil-Distance Technique at the PELLETRON, São Paulo and the TANDAR/CNEA Laboratory, Buenos Aires, Argentina. Reduced transition probabilities B(E2) were extracted in order to calculate the deformation parameters. These values were compared to theoretical models available for the mass region A~130, such as the Triaxial Rotor plus Quasi-Particle, the Cranked-Shell Model, the Geometrical Model and the Total Routhian Surface. The experimental values of 135Pr lifetimes, B(E2) and deformation parameters (B2, y) were compared to those for the 134Ce core, measured in [Hu77]. It was found that Q0 values for the h11/2- excited levels before backbending in 135Pr nucleus are very similar to those of the 134Ce core. TRS calculations were performed for both nuclei giving theoretical results which are in contrast to the experimental values.

Este trabalho apresenta um método experimental para determinação de energia de transições gama utilizando-se detectores de HPGe em experimentos em coincidência com precisões similares às que se obtém em medidas simples. O método foi aplicado na medida das energias das transições gama dos decaimentos das séries do 233U e 232U. Matrizes de covariância de dados experimentais são tão significativas quando suas variâncias para a avaliação de incertezas experimentais e indispensáveis para a atualização e combinação de resultados. O procedimento desenvolvido neste trabalho utiliza-se de toda a matriz de covariância das energias das transições gama bem como das matrizes de covariâncias de todos os parâmetros em todas as etapas da análise. O arranjo experimental utilizou o módulo multidetector, padrão Camac, desenvolvido no Laboratório do Acelerador Linear. Os dados foram analisados usando o programa Bidim, desenvolvido durante este trabalho. O procedimento de ajuste, baseado no método dos mínimos quadrados, é aplicado diretamente sobre o espectro bidimensional. A precisão final das energias das transições gama foram iguais ou superiores a cerca de 5eV. Testes de qui-quadrado dos ajustes, sempre melhores que 15%, não indicaram a presença de inconsistências. / This work presents an experimental method for determining gamma-ray energies employing HPGe detectors in coincidence experiments with precision similar to that obtained in single measurements. The method was applied in the measurement of gamma-ray energies from the decay chain of 233U and 232U. Covariance matrices between experimental data are as significant as variances in the evaluation of experimental uncertainties and indispensable for updating and combining experimental results. In this work the complete covariance matrices for the gamma-ray energies and for all parameters used in the developed procedure were determined in every stage of the work. The experimental apparatus used the Camac multidetector adapter developed in the Laboratório do Acelerador Linear. The data were analyzed using the software Bidim, developed during this work. The fitting procedure, based on the least squares method, was applied directly to the two-dimensional spectra. The best final precision of the gamma-ray energies was about 5eV. Chi-squared tests of the fit, always better than 15%, do not indicate the presence of inconsistencies.

Foram estudados os decaimentos BETA-, BETA+ e por captura de elétrons do 132 Cs. Foram medidas misturas multipolares E2/M1 de transições pelo método de correlação angular direcional gama-gama. Foi aplicado o modelo de Bohr na formulação K. Kumar e M. Baranger ao 132 Xe e os resultados são discutidos. / The 132 Cs BETA-, BETA+ and electron capture decays have been studied. New gamma transitions and electron capture feedings were determined. Some E2/M1 multipole mixings of gamma transitions in 132 Xe and 132Ba were measured with the gamma-gamma angular directional correlation method. The Bohr\'s collective model with K. Kumar and M. Baranger\'s solution was applied to 132 Xe and the results were discussed.

Foram realizadas medidas de espectroscopia gama simples, de espectroscopia. gama-gama em coincidência e de correlação angular para o estudo de \'ANTPOT 194 PT\', a partir do decaimento por \'beta POT. +\' e por captura eletrônica de \'ANTPOT 194 AU\'. Foram determinadas, utilizando um cálculo covariante, as energias e as intensidades de 167 transições gama, das quais 31 pela primeira vez: 212 keV, 243 keV, 304 keV, 338 keV, 363 keV, 366 keV, 373 keV, 398 keV, 421 keV, 436 keV, 500 keV, 602 keV, 627 keV, 699 keV, 807 keV, 814 keV, 857 keV, 901 keV, 1121 keV, 1262 keV, 1346 keV, 1388 keV, 1474 keV, 1488 keV, 1535 keV, 1541 keV, 1565 keV, 1665 keV, 1675 keV, 1775 keV e 1780 keV. O esquema de níveis obtido contém 45 estados; destes estados, 4 foram determinados pela primeira vez: 1373 keV, 1737 keV, 2003 keV e 2140 keV. Foram determinados os valores para as razões de mistura multipolar \'delta\'(E2/M1) das transições mais intensas utilizando o método de correlação angular direcional gama-gama. Utilizando elipses de correlação, foi possível determinar ou restringir os valores do spin e/ou paridade de 7 níveis: 1373 keV, 1737 keV, 1778 keV, 1930 keV, 2052 keV, 2134 keV e 2157 keV. Cálculos usando o formalismo de Kumar e Baranger para a resolução do Hamiltoniano de Bohr foram realizados para o núcleo \'ANTPOT 194 PT\'. Foram então determinados níveis e propriedades eletromagnéticas e os resultados, discutidos. / Single gamma ray spectroscopy, gamma-gamma spectroscopy and gamma-gamma directional angular correlation have been performed to study the \'ANTPOT 194 PT\', following the \'beta POT. + \' decay and electron capture of \'ANTPOT 194 AU\'. We have determined, using covariant calculations, energies and intensities of 167 gamma transitions, 31 of them for the first time: 212 keV, 243 keV, 304 keV, 338 keV, 363 keV, 366 keV, 373 keV, 398 keV, 421 keV, 436 keV, 500 keV, 602 keV, 627 keV, 699 keV, 807 keV, 814 keV, 857 keV, 901 keV, 1121 keV, 1262 keV, 1346 keV, 1388 keV, 1474 keV, 1488 keV, 1535 keV, 1541 keV, 1565 keV, 1665 keV, 1675 keV, 1775 keV and 1780 keV. The decay scheme contains 45 levels; 4 of these states have been determined for the first time: 1373 keV, 1737 keV, 2003 keV and 2140 keV. We have also determined values for the multipole rnixing ratios \'delta\'(E2/M1) in the case of the strongest transitions, using directional gamma-gamma angular correlation. With the angular correlation ellipses, it was possible to determine or to restrict the spin and/or parity values of 7 levels: 1373 keV, 1737 keV, 1778 keV, 1930 keV, 2052 keV, 2134 keV and 2157 keV.

>Magister Scientiae - MSc / 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.

Metal foils were implemented in a measurement of neutron-induced fission at the IGISOL facility in 2016. These foils were activated by a neutron flux during the experiment and measured after the beam was turned off. The radioactive products from the neutron activation were identified in an analysis of γ-ray spectroscopy data. The results were then used to benchmark the neutron flux simulated by MCNPX, which is used for a simulation model of an ion guide that was implemented in the experiment in 2016. The predicted number of neutron activation products were calculated using the simulated neutron flux and compared to results from the experiment. This comparison benchmarked the neutron flux and showed a consistency with the results from a previous study. This is a step in the process to validate the predictive power of the simulation model which is developed for the study of neutron-induced fission.

Historically, two nuclear power plant incidents have led to major releases of radioactive isotopes into the environment. In the unfortunate event that such an incident would occur in Sweden, the national emergency preparedness has set-up carborne detector systems which can be used to map radionuclides in fallout affected areas. However, analysing the carborne measurments is not trivial. To investigate how these detector systems behave, a full scale model of a Swedish suburban neighborhood was constructed in the particle transport code SERPENT2. Within this model, detector and car geometries where defined to obtain an estimate of the measurement one would obtain efter different cleanup scenarios with an initial 100 kBq/m^2 ground deposition of the fission product Cs-137.

No description available.