LUCAS SATIRO DO CARMO

LUCAS SATIRO DO CARMO

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Brazilian aeolian sediments dating using tl, osl and esr
2023 - CARMO, LUCAS S. do; WATANABE, SHIGUEO; DEWITT, REGINA
In this work, a dunefield known as Dama Branca (Brazil) has been dated using the following techniques: Optically Stimulated Luminescence (OSL), Thermoluminescence (TL) and Electronic Spin Resonance (ESR). They are part of what is called “trapped charge dating technique”. Sediments have been collected from several points to study age distribution throughout Dama Branca. These ages are related to events of sediment transportation and stabilization. For Dama Branca specifically, variables related to weather such as rainfall and wind power are suspected to be responsible for its formation. OSL results were obtained applying the SAR protocol. TL and ESR results were obtained using the Multiple Aliquot Additive Dose protocol (MAAD). With respect to ESR measurements, the Ti-Li center was chosen for dating since it can be completely bleached by sun light exposure , which makes it suitable for aeolian sediment dating. The Ti-Li center is strongly dependent upon preheat, its stability has been assessed and a preheat temperature of 180 °C was selected. OSL ages are within 0.05 kyears and 2.05 x kyears. TL ages agree with OSL ages for samples collected from the dune base, however there are discrepancies between OSL and TL ages for the DBM2BASE sample, suggesting that it underwent a quicker burial process. ESR results are satisfactory for two samples, 2DB10 and 2DB11 (they follow OSL and TL results). The ages were compared to a simplified morphological study. In recent works about the weather in the Cabo Frio region it has been seen that the studied areas were formed under influence of arid conditions and cold water, variables that control sediment transportation in the region. Keywords (max. 5): TL, ESR, OSL, quartz, sediments dating.
Thermoluminescence (TL) properties of yellow beryl pellets
2023 - CARMO, LUCAS S. do; CARRERA, BETZABEL N.S.; WATANABE, SHIGUEO; CHUBACI, JOSE F.D.
Beryl is a silicate with chemical formula Be3Al2(SiO3)6 commonly found in Brazil. It has a few colored variations used as jewelry, like Aquamarine (blueish), Emerald (green) and Heliodor (yellow). In this work, Heliodor pellets of 5 mm diameter and 1 mm thickness have been produced and investigated using thermoluminescence (TL) to evaluate its potential for use as gamma ray’s dosimeter. The results show that the pellets exhibited a prominent TL peak at 205 °C that grows linearly with dose when irradiated from 1 Gy to 1000 Gy. Deconvolution of the TL peaks was carried out using CGCD (Computerized Glow Curve Deconvolution) method. The peak positions were determined using the Tm/Tstop method described in McKeever (1985). Samples were stored in dark room at room temperature for 21 days to evaluate the fading of the TL signal, the main TL peak at 205 °C did not show any decrease in intensity.
Importância das radiações nucleares nas datações arqueológicas e geológicas
2020 - CARMO, LUCAS S. do
Neste trabalho, o campo de dunas conhecido como Dama Branca foi datado utilizando as técnicas de Luminescência Opticamente Estimulada (LOE), Termoluminescência (TL) e Ressonância Paramagnética Eletrônica (RPE). Os sedimentos foram coletados de diversos pontos para estudar a distribuição das idades em certas partes do campo dunas, essas idades revelam dados sobre o transporte e estabilização de sedimentos. Para o caso de Dama Branca, os fatores relacionados ao clima (vento e umidade) são tidos como os principais agentes responsáveis pela sua formação. Os resultados das datações por LOE foram obtidos empregando o protocolo SAR (Single Aliquot Regenerative), enquanto para TL e RPE, o protocolo MAAD (Multiple Aliquot Additive Dose) foi utilizado. Com relação ao RPE, o centro utilizado no estudo foi o de Ti-Li no quartzo. Este centro pode ser zerado pela luz solar, o que possibilita a datação de sedimentos por esta técnica. O centro de Ti-Li é fortemente influenciado por uma componente sensível à temperatura, exigindo um tratamento térmico antes da leitura do sinal. A estabilidade térmica do centro é estudada e a temperatura de 180 °C foi definida como a temperatura de pré-aquecimento. As idades obtidas por LOE vão de 0,05 x 103 a 2,05 x 103 anos. As idades TL, para as amostras das bases, estão de acordo com os resultados obtidos para LOE, entretanto sugere que uma das amostras, DBM2BASE, tenha passado por um processo mais rápido de soterramento. Os resultados de RPE são satisfatórios para duas amostras, 2DB10 e 2DB11 (acompanham os resultados de LOE e TL). As idades, com base em um estudo morfológico de Dama Branca e em trabalhos sobre o clima da região, mostram que as áreas datadas do campo de dunas estudado foram formadas sob influência de clima seco e água fria, fatores que favorecem o transporte de sedimentos na região.
Calculated and experimental response of calcium silicate polycrystalline to high and very-high neutron doses
2020 - GONZALES-LORENZO, CARLOS D.; WATANABE, SHIGUEO; CAVALIERI, TASSIO A.; CANO, NILO F.; RAO, T.K.G.; CHUBACI, JOSE F.D.; CARMO, LUCAS S.; BUENO, CARMEN C.
In the scope to the discovery of new detectors for high and very-high gamma and neutron radiation dose (mGy- MGy), synthetic polycrystals of CaSiO3 have been produced by the devitrification method in our laboratory. CaSiO3 polycrystals were irradiated with thermal, epithermal and a small fraction of fast neutrons. In the position of irradiation, the thermal neutron flux is about 83% of the total neutron flux and the thermal neutron fluences range from 5.82 × 1013 to 2.97 × 1016 n/cm2. This thermal neutron reacts with Ca, Si and O through (n,γ) process, all or part of the gamma emitted in this reaction is absorbed by the sample and is responsible for the induction of thermoluminescence (TL). The total energy emitted by the (n,γ) reaction was calculated analytically. Furthermore, Monte Carlo simulations using MCNP5 radiation transport code was carried out to calculate the deposited dose on CaSiO3 by the neutron interaction finding doses ranging from 42 Gy to 21 kGy. CaSiO3 TL glow curves, after radiation exposure from the reactor, display the main prominent TL peak around 234–259 °C and when exposed to gamma radiation (Co-60) it shows the main TL peak around same 234–272 °C.
OSL-SAR dating of sediments from Brazilian aeolian system
2019 - CARMO, L.S. do; WATANABE, S.; DEWITT, R.
It has been reported that the formation and stabilization of coastal dune fields in Brazil have a dependence on the climatic changes, Relative Sea Level (RSL) variations, etc. In this work, a dune field known as “Dama Branca”, located in the city of Cabo Frio, Rio de Janeiro, has been studied to understand its mobility. Dating by trapped charge dating techniques as Optically Stimulated Luminescence (OSL) using the Single Aliquot Regenerative protocol (SAR), helps us to understand the formation and dynamics of aeolian systems in Brazil. Samples from two positions; DB and 2DB, were collected from different heights and points for dating. The results obtained by OSL-SAR showed that ages decrease as the height from the dune base increases and older samples are found in deeper horizontal positions. The ages from the base of the studied dunes indicated that its stabilization occurred during the recess of the sea level and that erosion caused by the wind action is revealing an old generation of this dune filed.
Dating aeolian sediments from Cabo Frio, Rio de Janeiro, using Ti-Li center electron spin resonance, thermoluminescence and optically stimulated luminescence
2019 - CARMO, LUCAS S. do; WATANABE, SHIGUEO; DEWITT, REGINA; SILVA, RAFAELA J.; FELIPE, LUIZ; CHUBACI, JOSÉ F.D.
In this work, optically stimulated luminescence (OSL), thermoluminescence (TL) and electron spin resonance (ESR) were used to date coastal aeolian sediments from a dunefield known as Dama Branca (White Lady) in Rio de Janeiro, Brazil. Sediments have been collected from seven different points to study sand transportation and stabilization. Results obtained by those different techniques were compared. The equivalent dose (De) measured by OSL, was obtained using the Single Aliquot Regenerative protocol (SAR), TL results have been corrected measuring residual TL and ESR measurements were carried out using Ti-Li center. The thermal stability of Ti-Li center was evaluated, samples were preheated to exclude the Ti-Li center thermally sensitive component. The gamma-ray spectroscopy was used to measure Uranium, Thorium and Potassium concentrations in the soil, the values were analyzed with the Dose Rate and Age Calculator (DRAC) to generate the Annual Dose Rate (Dr). A morphological analysis showed that the dunefield has been moving influenced by semi-arid conditions and upwelling close to the coast. Ages from 0.05 to 2.22 thousand of years were found.
Dating sediments from a terrace found in Iguape - Icapara in southeast coast in the state of São Paulo, Brazil
2018 - CORTEZ, BRUNA; CHUBACI, JOSE F.D.; GOMES, MONISE B.; OLIVEIRA, LETICIA M.; SATIRO, LUCAS C.; ROCCA, RENE R.; ARIZACA, EDY E.C.; WATANABE, SHIGUEO
Dating of shells from Pântano da Malhada, Rio de Janeiro
2018 - GOMES, MONISE B.; CORTEZ, BRUNA; OLIVEIRA, LETICIA M. de; CARMO, LUCAS S. do; CHUBACI, JOSE F.D.; ROCCA, RENE R.; WATANABE, SHIGUEO
Dating aeolian sediments using ESR Ti-Li center in quartz, TL and OSL-SAR
2018 - CARMO, L.S. do; WATANABE, S.; SILVA, R.J.; CHUBACI, J.F.D.
OSL-SAR dating of sediments from brazilian aeolian system: Dama Branca, Rio De Janeiro, morphodynamic study
2017 - CARMO, LUCAS S. do; WATANABE, SHIGUEO; DEWITT, REGINA
It has been reported that the formation and stabilization of coastal dune fields in Brazil have a dependence on the climate changes and Relative Sea Level (RSL) variations. A few topics regarding the morphodynamics of coastal aeolian systems in Brazil can be the RSL variations in the Holocene and weather conditions. In this work, a dune field known as “Dama Branca”, located in the town of Cabo Frio, Rio de Janeiro, has been studied to understand its formation and stabilization. Dating by trapped charge dating techniques as Optically Stimulated Luminescence (OSL) using the Single Aliquot Regenerative protocol (SAR), help us to understand the formation and dynamics of aeolian systems in Brazil. Samples from a dune were collected from different heights and points for dating. The results obtained by OSL-SAR showed that ages decrease as the height from the dune base increase and older samples are found in deeper horizontal positions. The ages for the base of the studied dunes indicated that its stabilization occurred during the recess of the sea level.