CARLOS HENRIQUE DE MESQUITA

CARLOS HENRIQUE DE MESQUITA

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Development and Characterization of the CsI:Tl scintillator grown by the Bridgman technique for use as a radiation detector
2023 - SUZART, KAROLINE F.; PEREIRA, MARIA da C.; MESQUITA, CARLOS H. de; POTIENS, MARIA da P.A.
Zonal refining and Bridgman technique for CsI:Tl scintillation crystal growth
2022 - SUZART, K.F.; PEREIRA, M.C.C.; HAMADA, M.M.; MESQUITA, C.H.
This work describes the development of the crystal cesium iodide doped with thallium (CsI:Tl) for use as a radiation detector. For CsI salt purification the zonal refining methodology using a horizontal oven at a constant temperature of 700 °C was used. The high temperature region corresponds to approximately 10% of the salt bed containing (260 mm). This region moves at a speed of 50 mm/h. The crystal growth was carried out by Bridgman technique, using a vertical oven at speed of 1 mm/h.
Biokinetics and radiation dosimetry for [4-(14)C]-cholesterol in humans
2011 - MARCATO, L.A.; HAMADA, M.M.; MESQUITA, C.H.
Medical and clinical researches utilize radiolabelled cholesterol to obtain information about the physiology of cholesterol and of its several substrates (biliary acids, hormones and vitamins) in the body. The radiotracers constitute a simple and accurate tool for metabolic studies; however, the scientific community has shown certain reservations concerning the use of radioisotopes. Probably, the apprehension is result of the question about the deleterious radiation effects. Although the studies that utilize radioisotopes are approved by strict ethic committees, most of them do not mention the radiometric doses at which the human subjects are exposed during these studies. The International Commission on Radiological Protection (ICRP) provides a generic carbon model (GCM) to calculate the effective dose of compounds labeled with 14C, first described on ICRP publication 30. The effective dose coefficients for most compounds appear to be greatly overestimated by the GCM in comparison with those generated by more realistic models [1]. The GCM cannot be applied to the interpretation of bioassay data with any degree of confidence [1]. The purpose of the present study is to improve the generic biokinetic model [2] for use in the assessment of the internal dose received by human subjects who were administered labelled cholesterol either orally or intravenously. This model was used with the ANACOMP software to estimate the radiometric doses with the MIRD techniques. To validate the model, the simulated profile curves were compared with the profile curves described on the literature (Kruskal-Wallis test, P=0.4232). The model reproduced the intestinal absorption of cholesterol and the excretion of cholesterol in feces and urine. The estimated effective dose coefficient calculated for the reference man described on ICRP publication 23 was 1.35x10-11 SvBq-1. The organs that received the highest equivalent dose were the lower large intestine (1.03x10-10 GyBq-1), upper large intestine (3.74x10-11 GyBq-1) and small intestine (1.58x10-11GyBq-1). The effective dose coefficient calculated by the proposed dosimetric model was approximately forty-three times lower than that which is calculated by the ICRP generic model (5.8x10-10 SvBq-1) for ingested 14C that assumes complete absorption to blood.
A comparative study on the performance of radiation detectors from the HgI2 crystals grown by different techniques
2011 - MARTINS, J.F.T.; COSTA, F.E.; SANTOS, R.A.; MESQUITA, C.H.; HAMADA, M.M.
There have been attempts to develop room-temperature X- and gamma ray semiconductor detectors for various applications. The main physical semiconductor properties required for fabrication of room temperature semiconductor detectors are: (1) high atomic number; (2) high density; (3) high absorption coefficient; (4) a band gap large enough to keep leakage currents low, at room temperature and (5) large electron and hole mobility-lifetime products, for an efficient charge collection [1, 2]. Among these types of detectors, HgI2 has emerged as a particularly interesting material in view of its wide band gap (2.13 eV) and its large density (7.5 g/cm3 ). HgI2 crystals are composed of high atomic number elements (ZHg=80 and Zi=53) and with high resistivity (>1014 ficm). These are important factors in applications where compact and small thickness detectors are necessary for X- and gamma rays measurements. However, the applications of Hgi2 are limited by the difficulty in obtaining high-quality single crystals and the long-term reliability problems in devices made from crystals [1]. in this work, the Hgi2 crystals were grown using four different techniques: (a) physical vapor transport, (b) solution from dimethyl sulfoxide complexes, (c) vapor growth of HgI2 precipitated from acetone and (d) Bridgman method. The obtained crystals for four methods were characterized considering the following physical chemistry properties: crystal stoichiometry, crystal structure, plan of the crystal orientation, surface morphology of the crystal and crystal impurity. The influence of these physical chemistry properties on the crystals developed by four techniques was studied, evaluating their performance as a radiation detector. The best result of radiation response was found for the crystal grown by physical vapor transport. Also, the dependence of the radiation response on the HgI2 crystal purity was also studied. For this, the HgI2 raw material was purified by the many pass zone refining technique. A significant improvement in the characteristics of the detector-crystal was achieved, when the starting materials became purer.
Development of the mechanical system on a third-generation industrial computed tomography scanner in Brazil
2011 - CALVO, WILSON A.P.; MESQUITA, CARLOS H. de; SPRENGER, FRANCISCO E.; COSTA, FABIO E. da; SALVADOR, PABLO A.V.; CARVALHO, DIEGO V. de S.; HAMADA, MARGARIDA M.
The development of measurement geometry for medical X-ray computed tomography (CT) scanners carried out from the first to the fourth-generation. This concept has also been applied for imaging of industrial processes such as pipe flows or for improving design, operation, optimization and troubleshooting. Nowadays, gamma CT permits to visualize failure equipment points in three-dimensional analysis and in sections of chemical and petrochemical industries. The aim of this work is the development of the mechanical system on a third-generation industrial CT scanner to analyze laboratory gas absorption column which perform highly efficient separation, turning the 60Co, 137Cs or 192Ir sealed gamma-ray source and the NaI(Tl) multidetector array. It has also a translation movement along the column axis to obtain as many slices of the process flow as needed. The mechanical assembly for this third-generation industrial CT scanner is comprised by strength and rigidity structural frame in stainless and carbon steels, rotating table, source shield and collimator with pneumatic exposure system, spur gear system, translator, rotary stage, drives, and stepper motors. The use of suitable spur gears has given a good repeatability and high accuracy in the degree of veracity. The data acquisition boards, mechanical control interfaces, software for movement control and image reconstruction were specially development. This third-generation industrial CT scanner has obtained good spatial resolution and images. The filtered back projection (FBP) tomographic reconstruction algorithm used has shown a faster convergence. The mechanical system presented a good performance in terms of strength, rigidity, accuracy and repeatability with great potential to be used for education or program dedicated to training chemical and petrochemical industry professionals and for industrial process optimization in Brazil.
Development of a gamma ray computed tomography technique for random packed columns analysis
2008 - MESQUITA, CARLOS H. de; VASQUEZ, PABLO A.S; PEREIRA, JOAO C.S. de M.; MARTINS, JOAO F.T.; CALVO, WILSON A.P.; HAMADA, MARGARIDA M.
Zonal refining and Bridgman technique for CsI:Tl scintillation crystal growth
2021 - SUZART, K.F.; PEREIRA, M.C.C.; HAMADA, M.M.; MESQUITA, C.H.
Characterization of the CsI(Tl) crystalline scintillating detector produced at IPEN
2021 - SUZART, K.F.; VELO, A.F.; HAMADA, M.M.; PEREIRA, M.C.C.; MESQUITA, C.H.
Cesium iodide crystal activated with thallium (CsI(Tl)) is used as radiation sensor because of its favorable characteristics as scintillator, when excited by gamma radiation. This crystal has good mechanical strength and it is relatively little hygroscopic. In the present work, the CsI(Tl) crystal was grown in the Nuclear Energy Research Institute (IPEN/CNEN/SP) by Brigdman technique, in two different formats: (a) cylindric (∅ 20.1 mm x ↑ 11.9 mm) and (b) parallelepiped (12.3 mm x ↑ 19.5 mm). The scintillator spectrometry was studied through five gamma radiation sources: 99mTc (140 keV), 133Ba (355 keV) 22Na (511 keV) and 137Cs (662 keV). The crystals were coupled to a photomultiplier tube using 0.5 McStokes viscosity silicone grease as the optical interface. All electronics for signal measurements were developed at IPEN. Luminescence property of the CsI(Tl) crystal was excited by the radiation from a 137Cs source. The energy resolution of the crystalline detector was determined by the FWHM parameter, corresponding to the photopeak width at half of its height.
Characterization of the petrology of the tar sandstone rock of the Paraná basin
2021 - AMADEU, R.A.; BERNARDES, T.L.S.; SANTOS, R.S.; GARCIA, R.H.L.; VELO, A.F.; CAVALLARO, F.A.; MESQUITA, C.H.; HAMADA, M.M.
In the state of São Paulo (Brazil), occurrences of tar sandstone are known in Botucatu, Angatuba, Pirambóia, Anhembi and Bofete municipalities. In the present work a sample of white tar sandstone was taken from Anhembi municipality, located at Km 168 of the Castelo Branco Highway. In the petroleum area, sandstones act as excellent hydrocarbon reservoirs, since they have specific characteristics, such as: high porosity and permeability. Porosity is a property of rocks, and it may be understood as the voids contained in the matrix (where fluids remain stored), while permeability is the ability of the rock to transmit these stored fluids. Due to these characteristics of sandstones, researchers have shown a growing interest in the study and characterization of this type of rock, which is a fundamental element of an oil system. In the present work, four characterization techniques were used in the Anhembi tar sandstone sample, namely: X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscope (SEM) and the third generation Industrial Computerized Tomography. Through these techniques, the chemical composition, grain morphology, crystalline structure phases and an image of a slice of the internal structure of the white tar sandstone sample were obtained.
Performance of the X-ray powder diffraction (XRD), X-ray fluorescence (XRF) and the industrial computed tomography used for characterization of the vesicular volcanic rock
2021 - SANTOS, R.S.; CAVALLARO, F.A.; BERNARDES, T.L.S.; AMADEU, R.A.; GARCIA, R.H.L.; VELO, A.F.; MESQUITA, C.H.; HAMADA, M.M.
Volcanic rock is a designation in geology given to extrusive igneous rocks. One type of igneous rock of interest, in economic terms, is vesicular, since, besides the knowledge of the morphology (positioning, size, direction, and interconnectivity of the vesicles) of these structures within the spill, there is also an economic interest regarding the possibility of this rock as a reservoir of fluids (water and hydrocarbons). In this work, samples of vesicular volcanic rock from the Paraná Basin were studied for their characterization, aiming to contribute to the knowledge of this rock proprieties as a reservoir of fluids. The elements present inside the rocks were identified and quantified by X ray fluorescence and X ray diffraction. The dimensions of the vesicles and the interconnection between them could be clearly observed in the reconstructed images of the rocks measured by the third generation Gamma ray industrial tomography technique