LUCAS SATIRO DO CARMO
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Resumo IPEN-doc 30310 Brazilian aeolian sediments dating using tl, osl and esr2023 - CARMO, LUCAS S. do; WATANABE, SHIGUEO; DEWITT, REGINAIn 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.Resumo IPEN-doc 30309 Thermoluminescence (TL) properties of yellow beryl pellets2023 - 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.Artigo IPEN-doc 27157 Calculated and experimental response of calcium silicate polycrystalline to high and very-high neutron doses2020 - 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.