Edge-defined, film-fed growth (EFG) technique for the preparation of alpha-Al2O3 : C crystal with highly sensitive thermoluminescence response

In this work, alpha-Al2O3:C, a highly sensitive thermoluminescence dosimetry crystal, was grown by the EFG method in which a graphite heating unit and shield acted as the carbon source during the growth process. The optical, luminescent properties and dosimetric characteristics of the crystal were investigated. The as-grown crystal shows a single glow peak at 536 K, which is associated with Cr3+ ions. After annealing in H-2 at 1673 K for 80 h, the crystal shows a single glow peak at 460 K and a blue emission band at 415 nm. The thermoluminescent response of the annealed crystal shows linear-sublinear-saturation characteristics in the dose range from 5 x 10(-6) to 100 Gy.

Thermoluminescence measurements of entrance surface skin dose in exams of dog's chest in veterinary radiology

This study aims to determine the entrance surface skin doses in dogs (with suspected pulmonary metastasis) submitted to chest X-rays using the technique of thermoluminescence (TL) dosimetry. Twenty seven radiologic exams of dogs of different breed and sizes were performed. The radiation doses were assessed using thermoluminescent dosimeters of calcium sulphate doped with dysprosium (CaSO(4):Dy) produced at Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN). The entrance surface skin dose range evaluated in this type of procedure was between 0.43 mGy to small size dogs and 4.22 mGy to big size dogs with repeated exams. The obtained results indicate that is extremely important the assessment of radiation doses involved in veterinary diagnostic radiology procedures, to evaluate the delivered doses to the animals, to be used as a parameter in the individual monitoring of pet's owners, who assist the animal positioning, and to protect occupationally exposed workers at the Veterinary Radiology Clinics. (C) 2010 Elsevier Ltd. All rights reserved.

Hammasröntgentutkimusten termoluminesenssidosimetria

Tavanomaisten hammasröntgenlaitteiden säteilyannoksia valvotaan postitettavien testipakettien ja paikan päällä tehtävien tarkastusten avulla. Säteilyannoksen valvontaan käytetään termoluminesenssidosimetrejä (Thermoluminescence Dosimetry, TLD). Dosimetreissä on TL-materiaalista valmistettuja loistekiteitä, joihin absorboitunut säteilyenergia vapautuu valona materiaalia lämmitettäessä. Prosessissa vapautuvan valon intensiteetti on suoraan verrannollinen absorboituneeseen säteilyannokseen. TLD:llä mitataan rekisteröityjen intraoraalilaitteiden tuottamaa säteilyannosta potilaan posken kohdalla. Säteilyturvakeskus (STUK) ylläpitää rekisteriä ilmoitusvelvollisuuden alaisista hammasröntgenlaitteista. Nyt hammaslaiterekisteriä ollaan uudistamassa siten, että TLD-mittaustulosten käsittely ja annoslaskenta siirtyvät rekisteristä WinTLD-laskentaohjelmaan, jossa on kaikki tarvittavat parametrit annoksen laskemiseksi. Tässä työssä TLD-mittausjärjestelmän kalibrointituloksia analysoitiin vuosilta 1996-2011 ja määritettiin uudelleen laskennassa käytetty energiakorjauskerroin, joka on osa tulevaa WinTLD-konfigurointia. Mittauksissa tarvittavat standardisäteilylaadut (ISO H-laadut) pystytettiin osana työtä. Henkilödosimetrien suorituskykytestauksessa käytetään ISO N-säteilylaatuja. Mirion Technologies (RADOS) käyttää TLD-systeemiä henkilödosimetriassa, ja hammas-TLD on tämän järjestelmän sovellus potilasdosimetriaan. ISO H-laadut otettiin käyttöön, jotta dosimetrien vastetta voitiin ISO N-laatujen tapaan tutkia jatkuvana fotonienergian funktiona Cs-137 ja Co-60 gammasäteilylaatuihin asti ja koska niillä voitiin jäljitellä todellista kliinistä suodatusta. Energiakorjauskerroin kalibroinnissa käytettävän Co-gammasäteilyn ja intraoraalikuvauksissa käytettävän röntgensäteilyn välillä määritettiin uudelleen. Sen arvoksi (yksikkö mGy/mGy) saatiin ISO N-60-laadulla 0,671 ja ISO H-60-laadulla 0,677, jotka ovat numeerisesti hyvin lähellä aikaisemmin määritettyä kerrointa 0,679. Energiakorjauskertoimen epävarmuudeksi saatiin 3,5 % (2std) ja annosmittauksen epävarmuudeksi 7,8 %. Energiavasteiden perusteella dosimetreissä käytetty materiaali on kahdesta vaihtoehdosta MTS-N (LiF:Mg,Ti) eikä MCP-N (LiF:Mg,Cu,P). TLD-järjestelmää voidaan kehittää ja konfiguroida uusien tulosten perusteella, jolloin otetaan käyttöön muun muassa uudelleenmääritetty energiakorjauskerroin. ISO H-säteilylaadut otettiin 22.3.2011 virallisesti käyttöön STUKissa ja niitä käytetään dosimetritestauksessa tarvittaessa suuria annosnopeuksia ja annoksia.

Dating archeological ceramics from the Valley of Vitor, Arequipa by the TL method

The age of some ancient pottery from the Valley of Vitor in the region of Arequipa, Peru, is determined by the thermoluminescence (TL) method. For dating, a 325 degrees C TL peak was used and irradiation with -dose from 5 to 50Gy was carried out for the additive method, and from 0.4 to 5Gy for the regeneration method. For these dose values, the TL intensity is observed to grow linearly, obtaining an accumulated dose of 1.62 +/- 0.09Gy and 1.36 +/- 0.03Gy for the additive and regeneration methods, respectively. The age (A) of the sample was calculated by the two methods, being A=867 +/- 195 years after Christ (AC) for the additive method and A=1050 +/- 157 years AC for the regeneration method. Both results are within 800-1200 years AC, which is the period of the Wari culture.

Study of entrance surface skin dose in veterinary radiology

This study aims the evaluation of the radiation dose levels involved in veterinary radiology and to contribute to review the procedures for performing radiographic exams in animals in the Department of Veterinary Radiology of Faculdade de Medicina Veterinária e Zootecnia of Universidade Estadual Paulista (FMVZ-UNESP/Brazil). The obtained results has shown to be extremely important the assessment of doses involved in veterinary diagnostic radiology procedures both to protect the occupationally exposed workers and to optimize the delivered doses to the animals. © 2009 Springer-Verlag.

Avaliação das doses de cães submetidos a exames radiográficos de pulmão

This study aims to determine surface skin doses in dogs (with suspected pulmonary metastasis) submitted to chest X-rays using the technique of thermoluminescence dosimetry. Twenty seven exams from different dogs were performed at the Faculdade de Medicina Veterinária e Zootecnia da Universidade Estadual Paulista (FMVZ-UNESP/Botucatu). The doses were evaluated using thermoluminescent dosimeters of calcium sulphate doped with dysprosium (CaSO4:Dy) produced by the Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN). The pulmonary metastasis exams are carried out in three projections, one dorsal-ventral and two lateral-lateral. During the procedures the projection thicknesses and source-skin surface distances were registered. To simulate the dog phantom the dosimeters were positioned in a cubic simulator (30x30x30 cm) of polymethylmethacrylate (PMMA) filled with water and irradiated according to the parameters of projections with the X-ray energies ranging from 45 to 70 kV. To estimate the surface skin dose the dose-response curves were obtained for X-ray energies of 50 and 70 kV using the diagnostic X-ray beam machine of the Instruments Calibration Laboratory of IPEN for doses of 1.5, 2.0, 2.5, 3.5 and 4.0 mGy. The main difficulty of this work was the dog immobilization that is reflected in poor-quality diagnostic imaging and, consequently, demands the repetition of the exams, which contributes to the increase of the doses received by the animals being studied and the clinical staff. The doses evaluated in this type of procedure are between 0.43 and 4.22 mGy. This research has shown to be extremely important for the assessment of doses involved in veterinary diagnostic radiology procedures, and as a parameter in the individual monitoring of pet’s owners who assist the animal positioning and occupationally exposed workers of the Department of Veterinary Radiology

TL dating of pottery fragments from four archaeological sites in Taquari Valley, Brazil

Sixty-three pottery fragments from four archaeological sites, numbered RST110, RST101, RST114 and RST114, in the Taquari Valley, vicinity of the city of Lajeado, Rio Grande do Sul state, southern Brazil, have been dated by the thermoluminescence method. Some of them from RST110 and RST101 are as old as 1400-1200 years, whereas those from RST114 and RST107 are younger than 800 years. This result indicates that RST101 and RST110 were peopled earlier than RST114 and RST107. The recent dates found are 302, 295 and 146 years and they are possible, since the first German immigrants who arrived in this region encountered Tupi-Guarani Indians still living there. One interesting result refers to the glow curves of quartz grains RST110, RST101 and RST114 that differ from the glow curves of RST107 quartz grains.

Synthesis, characterization, optical absorption, luminescence and defect centres in Er3+ and Yb3+ co-doped MgAl2O4 phosphors

The Er3+-Yb3+ co-doped MgAl2O4 phosphor powders have been prepared by the combustion method. The phosphor powders are well characterized by X-ray diffraction (XRD) and energy dispersive (EDX) techniques. The absorption spectrum of Er3+/Er3+-Yb3+ doped/co-doped phosphor powder has been recorded in the UV-Vis-NIR region of the electro-magnetic spectrum. The evidence for indirect pumping under 980 nm excitation of Er3+ from Yb3+ was observed in the MgAl2O4 matrix material. Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermally stimulated luminescence (TSL) process in MgAl2O4:Er3+ phosphor. Three defect centres were identified in irradiated phosphor by ESR measurements which were carried out at room temperature and these were assigned to an O- ion and F+ centres. O- ion (hole centre) appears to correlate with the low temperature TSL peak at 210 A degrees C and one of the F+ centres (electron centre) is related to the high temperature peak at 460 A degrees C.

Avaliação dos níveis de radiação ambiental no laboratório de tomografia por emissão de pósitrons acoplada a tomografia computadorizada, microPET/CT

O sistema microPET/CT é um importante equipamento utilizado nas pesquisas de imagem diagnóstica em pequenos animais. O radiofármaco mais usado nesta tecnologia é o fluordeoxiglicose marcado com flúor-18. Este estudo tem como objetivo efetuar o controle radiológico no laboratório de pesquisa microPET/CT do Centro de Radiofarmácia do IPEN-CNEN/SP, de forma a satisfazer tanto as normas nacionais como as recomendações internacionais. O laboratório está classificado pela equipe de radioproteção da instalação como área supervisionada, nas quais embora não seja obrigatória a adoção de medidas específicas de proteção e segurança, devem ser submetidas reavaliações regulares das condições do ambiente de trabalho. Visando assegurar a proteção radiológica dos trabalhadores diretamente envolvidos no manuseio do equipamento, realizou-se o monitoramento do local de trabalho e a avaliação do controle de dose individual. Inicialmente foi feito o monitoramento pré-operacional, isto é, o levantamento radiométrico no laboratório. Além disso, mediu-se nível de radiação externa nas instalações do laboratório e suas adjacências, por meio da colocação de nove dosímetros termoluminescentes (TL) de CaSO4:Dy, em locais previamente selecionados. Os indivíduos ocupacionalmente expostos foram avaliados mensalmente por meio do uso de dosímetros TL posicionados no tórax e por medidas de corpo inteiro, tomadas a cada seis meses. O período do estudo foi de dois anos, com início em abril de 2014. Para o controle do microPET/CT realizou-se testes de desempenho de acordo com o protocolo padrão do equipamento e em conformidade com a norma desenvolvida pela força tarefa para estudos com PET em animais Animal PET Standard Task Force. O presente estudo permitiu demonstrar que os níveis de radiação das áreas (estimativas de dose ambiente e dose efetiva), assim como a blindagem do equipamento estão adequados de acordo com os limites da exposição ocupacional. Ressalta-se a importância de se seguir rigorosamente os princípios de radioproteção, já que se trata de pesquisas com fontes radioativas não seladas.

Synthesis, photoluminescence, thermoluminescence and dosimetry properties of novel phosphor KSr4(BO3)(3):Ce

Polycrystalline powder sample of KSr4(BO3)(3) was synthesized by high-temperature solid-state reaction. The influence of different rare earth dopants, i.e. Tb3+, TM3+ and Ce3+, on thermoluminescence (TL) of KSr4(BO3)(3) Phosphor was discussed. The TL, photoluminescence (PL) and some dosimetric properties of Ce3+-activated KSr4(BO3)(3) phosphor were studied. The effect of the concentration of Ce3+ on TL intensity was investigated and the result showed that the optimum Ce3+ concentration was 0.2 mol%. The TL kinetic parameters of KSr4(BO3)(3):0.002 Ce3+ phosphor were calculated by computer glow curve deconvolution (CGCD) method. Characteristic emission peaking at about 407 and 383 nm due to the 4f(0)5d(1) -> F-2((5/2),(7/2)) transitions of Ce3+ ion were observed both in PL and three-dimensional (3D) TL spectra. The dose-response of KSr4(BO3)(3):0.002 Ce3+ to gamma-ray was linear in the range from 1 to 1000 mGy. In addition, the decay of the TL intensity of KSr4(BO3)(3):0.002 Ce3+ was also investigated.

Nd2O3 : Eu3+ nanocrystalline phosphor - a new potential thermoluminescing material for dosimetry

Nanoparticles of trivalent Eu3+-doped Nd2O3 phosphors have been prepared using a low-temperature solution combustion method with metal nitrate as precursor and oxalyldihydrazide as a fuel at a fairly low temperature (<500 degrees C) and in a very short time (<5 min). A powder X-ray diffraction pattern reveals that cubic Nd2O3 : Eu3+ crystallites are directly obtained without the requirement of further calcinations. The crystallite size, evaluated from Scherer's formula, was found to be in the range of 20-30 nm. The microstructure and morphology were studied by scanning electron microscopy, which showed the phosphor to be foamy and fluffy in nature. Thermoluminescence characteristics of the Nd2O3 : Eu3+ have been studied using gamma irradiation. These demonstrate that the phosphor is suitable for use as a dosimeter.

Thermoluminescence and EPR studies of nanocrystalline Nd2O3:Ni2+ phosphor

Nanocrystalline Nd2O3:Ni2+ (2 mol%) phosphor has been prepared by a low temperature (similar to 400 degrees C) solution combustion method, in a very short time (<5 min). Powder X-ray diffraction results confirm the single hexagonal phase of nanopowders. Scanning electron micrographs show that nanophosphor has porous nature and the particles are agglomerated. Transmission electron microscopy confirms the nanosize (20-25 nm) of the crystallites. The electron paramagnetic resonance (EPR) spectrum exhibits a symmetric absorption at g approximate to 2.77 which suggests that the site symmetry around Ni2+ ions is predominantly octahedral. The number of spins participating in resonance (N) and the paramagnetic susceptibility (chi) has been evaluated. Raman study show major peaks, which are assigned to F-g and combination of A(g) + E-g modes. Thermoluminescence (TL) studies reveal well resolved glow peaks at 169 degrees C along with shoulder peak at around 236 degrees C. The activation energy (E in eV), order of kinetics (b) and frequency factor (s) were estimated using glow peak shape method. It is observed that the glow peak intensity at 169 degrees C increases linearly with gamma-dose which suggest that Nd2O3:Ni2+ is suitable for radiation dosimetry applications. (C) 2012 Elsevier B.V. All rights reserved.

CdSiO3:Pr3+ nanophosphor: Synthesis, characterization and thermoluminescence studies

A series of Pr3+ (1-9 mol%) doped CdSiO3 nanophosphors have been prepared for the first time by a low temperature solution combustion method using oxalyldihydrizide (ODH) as a fuel. The final product was characterized by Powder X-ray diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM), and UV-Vis spectroscopy. The average crystallite size was calculated using Debye-Scherrer's formula and Williamson-Hall (W-H) plots and found to be in the range 31-37 nm. The optical energy band gap (E-g) of undoped for Pr3+ doped samples were estimated from Tauc relation which varies from 5.15-5.36 eV. Thermoluminescence (TL) properties of Pr3+ doped CdSiO3 nanophosphor has been investigated using gamma-irradiation in the dose range 1-6 kGy at a heating rate of 5 degrees C s(-1). The phosphor shows a well resolved glow peak at similar to 171 degrees C along with shouldered peak at 223 degrees C in the higher temperature side. It is observed that TL intensity increase with increase of Pr3+ concentration. Further, the TL intensity at 171 degrees C is found to be increase linearly with increase in gamma-dose which is highly useful in radiation dosimetry. The kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics was estimated by Luschiks method and the results are discussed. (c) 2012 Elsevier B.V. All rights reserved.

Synthesis, characterization, EPR, photo and thermoluminescence properties of YAlO3:Ni2+ nanophosphors

YAlO3:Ni2+ (0.1 mol%) doped nanophosphor was synthesised by a low temperature solution combustion method. Powder X-ray diffraction (PXRD) confirms the orthorhombic phase of yttrium aluminate (YAlO3) along with traces of Y3Al5O12. Scanning Electron microscopy (SEM) shows that the powder particles appears to be spherical in shape with large agglomeration. The average crystallite sizes appeared to be in the range 45-90 nm and the same was confirmed by transmission electron microscopy (TEM) and Williamson-Hall (W-H) plots. Electron Paramagnetic Resonance (EPR) and photoluminescence (PL) studies reveal that Ni2+ ions are in octahedral coordination. Thermoluminescence (TL) glow curve consists of two peaks with the main peak at similar to 224 degrees C and a shouldered peak at 285 degrees C was recorded in the range 0.2-15 kGy gamma-irradiated samples. The TL intensity was found to be increasing linearly for 224 degrees C and 285 degrees C peaks up to 1 kGy and thereafter it shows sub-linear (up to 8 kGy) and saturation behavior. The trap parameters namely activation energy (E), order of kinetics (b), frequency factor (s) at different gamma-doses were determined using Chens glow peak shape and Luschiks methods then the results are discussed in detail. Simple glow peak structure, the 224 degrees C peak in YAlO3:Ni2+ nanophosphor can be used in personal dosimetry. (C) 2012 Elsevier B.V. All rights reserved.

Structural, iono and thermoluminescence properties of heavy ion (100 MeV Si7+) bombarded Zn2SiO4:Sm3+ nanophosphor

Structural, iono (IL) and thermoluminescence (TL) studies of Zn2SiO4:Sm3+ (1-5 mol%) nanophosphor bombarded with swift heavy ions in the fluence range 3.91 x 10(12)-21.48 x 10(12) cm(-2) have been carried out. The average crystallite sizes for pristine and ion irradiated for 3.91 x 10(12) ions cm(-2) and 21.48 x 10(12) ions cm(-2) were found to be 34, 26 and 20 nm. With increase of ion fluence, the intensity of XRD peaks decreases and FWHM increases. The peak broadening indicates the stress induced point/clusters defects produced due to heavy ion irradiation. IL studies were carried out for different Sm3+ concentrations in Zn2SiO4 by irradiating with ion fluence of 15.62 x 10(12) ions cm(-2). The characteristic emission peaks at similar to 562, 599, 646 and 701 nm were recorded by exciting Si7+ ions in the fluence range 3.91 x 10(12)-21.48 x 10(12) ions cm(-2). These peaks were attributed to (4)G(5/2)-> H-6(5/2) (562 nm), (4)G(5/2)-> H-6(7/2) (599 nm), (4)G(5/2)-> H-6(9/2) (646 nm), and (4)G(5/2)-> H-6(5/2) (701 nm) transitions of Sm3+. The highest emission was recorded at 3 mol% of Sm3+ doped Zn2SiO4. TL studies were carried out for 3 mol% Sm3+ concentration in the fluence range 3.91 x 10(12)-21.48 x 10(12) ions cm(-2). Two U glow peaks at 152 and 223 degrees C were recorded. The kinetic parameters (E, b, and s), were estimated using Chen's peak shape method. Simple glow curve structure (223 degrees C), highly resistive, increase in TL. intensity up to 19.53 x 10(12) ions cm(-2), simple trap distribution makes Zn2SiO4:Sm3+ (3 mol%) phosphor highly useful in radiation dosimetry.