LUCAS FAUSTINO TOMAZ
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Artigo IPEN-doc 26195 Growth and optics characteristics of the CsI:Li scintillator crystal for use as radiation detector2019 - TOMAZ, LUCAS F.; MADI FILHO, TUFIC; BERRETTA, JOSE R.; PEREIRA, MARIA da C.C.Materials capable of converting ionizing radiation into light photons are called scintillators, some have specific efficiencies for certain applications and types of radiation, e.g. gamma, X-ray, alpha, beta and neutrons. CsI:Tl and NaI:Tl crystals are commonly found in the market because they have several applications, but few studies have been done on lithium doped cesium iodide crystal (CsI:Li). The lithium element, in this crystal used as a dopant, is also exploited as a converter for neutron detection, as it has a shock section of 940 barns for thermal neutrons. The study of the CsI:Li crystal is convenient considering the natural abundance of the lithium element with 7.5%, besides the interest in having a low cost national scintillator material with an opportunity to search the response of a detector for different types of radiation. The CsI:Li crystal was grown with molar concentration 10-4 to 10-1, using the vertical Bridgman technique. The parameters involved in the growth process were investigated. The transmittance was evaluated in the spectral region from 190 nm to 1100 nm. Luminescence emission spectra for the CsI:Li crystal were evaluated by photometric analysis of the crystal stimulated with a 137Cs (662 keV) source in front of the coupled sample at the monochromator input. The crystals showed of maximum luminescence intensity at the wavelength of 420 nm. The response of the scintillators when excited with gamma radiation of 241Am, 133Ba, 22Na,137Cs, 60Co and neutron radiation from the AmBe source, with energy range of 1 MeV to 12 Mev was evaluated.Artigo IPEN-doc 24134 Characteristics of Pb2+ doped CsI matriz under gamma and neutron excitations2017 - PEREIRA, MARIA da C.C.; MADI FILHO, TUFIC; BERRETTA, JOSE R.; TOMAZ, LUCAS F.; PINTO, MARLENE C.In recent years, there has been an increasing interest in finding new fast scintillating material or improve the characteristics of known scintillators for the demand of high energy physics, industrial and nuclear medical applications. Ions divalent lead Pb2+ built in some crystal structures are efficient emission centers and their applications in scintillators was and still is the reason of an intensive study of emission properties of different compounds containing these ions. The aggregation of impurities in CsI is poorly studied. The problem of impurity aggregation in CsI is of interest from point of view of the luminescent properties modification of this scintillation material. In this context, the crystals of Pb2+ doped CsI matrix were grown by the vertical Bridgman technique and subjected to annealing in vacuum of 10-6 mbar and continuous temperatura of 350°C, for 24 hours, and then they were employed. To evaluate the response of the CsI:Pb scintillator crystal to gamma radiation, radioactive sources of 137Cs (662 keV), 60Co (1173 keV and 1333 keV), 22Na (511 keV and 1275 keV) and 133Ba (355 keV) was used. The operating voltage of the photomultiplier was 2700 V for the detection of gamma rays and the accumulation time in the counting process was 600 s. The crystals used in gamma spectroscopy were cut with dimensions of 20 mm in diameter and 20 mm in height. The scintillator response to neutron radiation from a radioactive source of Am/Be with energy range of 1 MeV to 12 MeV was available. The activity of the AmBe source was 1Ci Am. The fluency was 2.6 x 106 neutrons / second. The operating voltage of the photomultiplier tube was 1300 V. The accumulation time in the counting process was 600 s. The scintillator crystals were cut with dimensions of 20 mm diameter and 10 mm height. With the results obtained, it may be observed that the crystals are sensitive to these radiations.