IBERE SOUZA RIBEIRO JUNIOR

IBERE SOUZA RIBEIRO JUNIOR

Página do item completo

Resultados de Busca

Agora exibindo 1 - 10 de 27

Determinação elementar em amostras de soja utilizando a técnica de análise por ativação com nêutrons
2023 - MURARO, JULIA P.; RIBEIRO JUNIOR, IBERE S.
On the use of coincidence INAA for selenium determination
2021 - RIBEIRO JUNIOR, IBERE S.; ZAHN, GUILHERME S.; GENEZINI, FREDERICO A.; DRESCHER, ADAM; LANDSBERGER, SHELDON
Instrumental Neutron Activation Analysis (INAA) is a widely used technique applied on the determination of several elements in different matrices. Selenium is one of the elements that can be studied by INAA and its determination is usually performed using one, or both, 136:01 and 264:66 keV transitions from 75Se radioisotope. Se determination by INAA is a case that requires special attention, mainly in virtue of three issues: (i) spectral interferences may occur due to intense gamma rays from 181Hf (136 keV) and 182Ta (264 keV); (ii) in samples with high levels of K and Na, the increased background levels due to Compton effect lead to enlargement of the detection limit; (iii) high concentration of P or any other intense high-energy beta emitter can severely impact the detection below 200{300 keV due to bremsstrahlung radiation. A possible solution for these issues is the use of gamma-gamma coincidence INAA (CINAA), as the 136 and 264 keV transitions are part of a strong gamma-gamma cascade. In this work coincidence measurements of the decay of 75Se were performed to compare the results for Se obtained by conventional INAA and CINAA in biological and geological Certi ed Reference Materials (CRMs). The results show that the use of coincidence can drastically reduce the net/gross ratio, which implies in a reduction of the detection limit for 75Se; furthermore, the results of Se concentration obtained using both methodologies are in agreement with the certi ed values, and both techniques provided accurate results.
Determinação de Sm por análise por ativação neutrônica em amostras geológicas
2022 - RIBEIRO JUNIOR, IBERE S.; GENEZINI, FREDERICO A.; ZAHN, GUILHERME S.
Nesse trabalho foi desenvolvido um método alternativo para determinação do fator de interferência do 153Sm como uma função do tempo de decaimento em virtude de interferência espectral de raios-X do 239Pu. Para realizar esse estudo foram irradiados dezoito padrões sintéticos de Sm e U no reator IEA-R1. Os fatores de interferência foram determinados experimentalmente para diferentes tempos de decaimento afim de ajustar uma função/curva teórica para os dados experimentais. Ao final será introduzido uma nova possibilidade de determinação do fator de interferência para o 153Sm utilizando medidas em coincidência gama-gama que apresenta a possibilidade de eliminar as interferências dos raios-X do 239Pu.
Aplicação de técnicas de coincidência gama-gama no LFNA-CRPQ
2022 - ZAHN, GUILHERME S.; GENEZINI, FREDERICO A.; RIBEIRO JUNIOR, IBERE S.
As técnicas de coincidência γ−γ consistem no uso de mais de um detector para registrar a radiação proveniente de alguma amostra, registrando-se apenas os eventosem que fótons foram registrados em mais de um detector. Essa técnica foi trazida ao Laboratório de Física Nuclear Aplicada (LFNA-CRPq) em decorrência da experiência em trabalhos anteriores em estrutura nuclear, e permite uma redução significativa no BG dos espectros, bem como nas interferências espectrais encontradas. Neste trabalho será apresentada uma pequena introdução ao uso da técnica, bem como o estado atual de sua implementação no LFNA-CRPq, possíveis aplicações e perspectivas futuras.
Cd impurities in Vanadium oxides
2021 - BURIMOVA, ANASTASIA; LEITE NETO, OSMAR F.; BOSCH-SANTOS, BRIANNA; CORREA, EDUARDO L.; PEREIRA, LUCIANO F.D.; SALES, TATIANE S.N.; RIBEIRO JUNIOR, IBERE S.; COSTA, MESSIAS S.; COSTA, CLEIDILANE; DANG, THANH T.; ZYABKIN, DMITRY; VAN STIPHOUT, KOEN K.F.; GERAMI, ADELEH M.; CORREIA, JOAO M.; SCHELL, JULIANA; CARBONARI, ARTUR W.
The number of metastable phases, the capriciousness at changing external conditions, and lack of accurate description of local behavior already resulted in severe misinterpretation of experimental outcomes for vanadium oxides[1–3]. The scope of already implemented and potential applications of vanadium oxides is, indeed, impressive, particularly as a battery cathode for energy storage[ 4]. Doping is widely exploited as a means of application-oriented tuning of the material properties. The properties of each particular phase may be tuned by doping to satisfy specific requirements and/or improve the functional performance. In the work here reported, electric quadrupole interaction on 111mCd nuclei implanted in vanadium pentaoxide doped with different concentrations of Cd were measured with time-differential perturbed angular correlations (TDPAC). Pure V2O5 as well as doped with 1%, 5%, and 10% of Cd were measured at different temperatures. To correlate the results with the possible formation of different phases and compounds, samples of VO2, CdV2O6, and Cd2V2O7 were also measured. The intention is to provide a comprehensive description, at an atomic level, of the doping effects on the local crystal structure and the electronic structure around the impurity and the consequences on the properties of the host oxides. Preliminary results show that the probability of formation of cadmium vanadates is low but the temperature and atmosphere of measurements have an important effect on the local scale.
Determination of scale factor for Ni-59 and Ag-108m in ion exchange resin from Angra 1
2021 - RIBEIRO JUNIOR, I.S.; GENEZINI, F.A.; SILVA, P.S.C. da; ANGELINI, M.; JUNQUEIRA, L.S.; ZAHN, G.S.
108mAg activity concentration determination in low and medium level radioactive waste from Angra Nuclear Power Plant
2021 - ANGELINI, M.; SILVA, P.S.C.; R.JUNIOR, I.S.
Comparison of two methodologies for spectra analysis in coincidence neutron activation analysis
2021 - RIBEIRO JUNIOR, I.S.; GENEZINI, F.A.; ZAHN, G.S.
The Research Reactor Center (CERPq) of IPEN-CNEN/SP has been developing a facility for Coincidence Neutron Activation Analysis (CNAA), a variation of the Neutron Activation Analysis technique in which gamma-gamma coincidence is used to reduce spectral interferences and improve detection limits of some elements. As the acquisition results in 2D-coincidence spectra, the spectrum analysis has to be dealt with accordingly. There are two distinct ways to perform these analyses, either directly, by fitting bidimensional peaks in the coincidence matrix, or by gating the spectra in one detector around each peak of interest and fitting the resulting 1D-spectrum in the usual way. In this work, the concentrations of As, Co, Cs, Sb and Se were determined in geological and biological reference materials by CNAA using two different methodologies of analysis, using the BIDIM software, which provides 2D-peak-fitting; and a combination of the AnalisaCAEN suite, which gates the 2D-spectra, with Canberra’s Genie2000, which fits the resulting unidimensional spectra. The outcomes allow for a discussion of the advantages and shortcomings of each method, both in terms of usability and of the reliability of the results.
On the use of gamma-gamma coincidence to detect very low activities
2017 - ZAHN, GUILHERME S.; GENEZINI, FREDERICO A.; RIBEIRO JUNIOR, IBERE S.; FAGIONATO, ESNEL A.
The detection of very low gamma ray activities is a delicate task, and very important in environmental radiation studies, for instance. It usually requires the use of low-background shielding, as the long counting times required usually make the background subtraction quite tricky, and often result in rather high experimental uncertainties. In this work a different approach is tested, where a two-detector gamma-gamma coincidence system is used to eliminate essentially all of the background continuum - at the cost of reduced overall efficiency and, more importantly, requiring that the radionuclide to be studied presents useful gamma-gamma coincidences. Two distinct methods of analysis are tested, either using an "open-window" coincidence where an event is registered whenever any event is registered in the other detector, or using a strict coincidence analysis, where a valid coincidence between two gamma-rays from the same decay are required; this allow for a discussion on the advantages and problems of each method, as well as for an experimental assessment of the performance of such a system.
AnalisaCAEN, a simple software suite to reduce and analyze coincidence data collected using CAEN v1724 digitizer
2019 - ZAHN, G.S.; GENEZINI, F.A.; RIBEIRO JUNIOR, I.
In this work a small software suite for the reduction and analysis of coincidence data collected using CAEN’s proprietary software was developed. These software check the output files for coincidences, generate a single list mode file with the coincident events, build histograms for each input, plus a time difference histogram and a 2-detector data matrix, perform time gates and allows for the subtraction of accidental coincidences, and perform energy gating on the final data matrices, generating histograms with the gated spectra. Moreover, the suite has an integrator that guides the user through all the required steps.