Mechanoluminescence and lyoluminescence characterization of Li2BaP2O7:Eu phosphor

In this work mechanoluminescence and lyoluminescence properties of Li₂BaP₂O₇: Eu phosphor are reported. Phosphor was synthesized through high temperature solid state diffusion method. Analysis of phosphor was made through various characterization techniques such as mechanoluminescence (ML), lyoluminescence (LL), x-ray powder diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL). It was observed that ML intensity showed good enhancement with variation in time, concentration of dopant Eu, mass of piston and impact velocity. Lyoluminescence intensity was also found to increase with change in time and mass of the sample. Variation in gamma doses imparted to Li₂BaP₂O₇: Eu phosphor was observed to affect both the ML and LL intensities' respectively. Both the ML and LL intensity attain a maximum value I_m at a particular time t_m but afterwards, it decreases and finally disappears. Morphology of Li₂BaP₂O₇: Eu luminescent material was also studied using scanning electron microscope technique. The average particle size in Eu doped lithium barium diphosphate phosphor was around 2 μm.     

Nanostructured layers of anion-defective gamma–alumina – New perspective TL and OSL materials for skin dosimetry. Preliminary results

Thin- layer material based on nanostructured Al₂O₃ of the surface density 5 mg/cm² was obtained. The material is characterized by high OSL and TL yields comparable with those for TLD-500 which is one of the leaders among the TL and OSL detectors. The dose response, fading and dependence of TL yield on heating rate was studied. It is established that high luminescence yield of the samples under study correlates with the content of anion vacancies and γ-phase of Al₂O₃. The data for time-resolved luminescent spectroscopy are presented, which evidence for possible correlation between high TL and OSL activity and the F-type centers. It is noted that the material needs to be modified for successful use in dosimetry. In addition further studies to decrease the contribution of unstable (at 300 К) components to OSL and TL yields are required.     

Environmental dosimetry with the BeOSL personal dosimeter – State of the Art

In the course of this work, the possibility of the measurement of ambient dose equivalent H*(10) with the BeOSL dosimetry system was evaluated. Calculations for the energy response of the 2-element BeOSL dosimeter for irradiation with H*(10) were performed. The response doesn't fulfil the requirements of IEC 62387-1. Especially the response for photon energies of 60–100 keV is to low. It is possible to correct this under response using a modified BeOSL 2-element dosimeter and a linear algorithm. So the national requirements for a H*(10) dosimeter in Germany can be fulfilled. An incidence angle independent measurement is not possible because for several angles of incidences (>60°) the filters of the 2-element dosimeter doesn't shield the correct element. Another material which is more suitable for the H*(10) measurement was tested. So the doping of BeO with Lanthanum leads to an enhanced energy response for measurement of H*(10). Furthermore a higher OSL sensitivity was found for this material. Further tests on the influence of Lanthanum concentration on the dosimetric properties are necessary.     

Evaluation of internal occupational exposure by 123I in a radiopharmaceutical production facility

¹²³I is a photon emitter radionuclide (159 keV) used for diagnostic procedures of endocrinal diseases in nuclear medicine. Since 1998 it is produced at the industrial radiopharmaceutical plant operated by the Institute for Nuclear Energy (IEN-CNEN) and supplied to clinics located in the State of Rio de Janeiro, in Brazil. The production of this radionuclide represents a risk of internal occupational exposure. According to international recommendations, workers involved in this activity should be routinely monitored in order to comply with dose limits and keep individual exposures as low and reasonably achievable. The Radiation Protection Plan implemented at the IEN includes annual in vivo measurements of ¹²³I in the thyroid performed at the In Vivo Monitoring Laboratory of the Institute for Radiation Protection and Dosimetry (IRD-CNEN). This work describes a series of improvements on the measurement techniques used for the monitoring of the workers from the facility, including (i) optimization of in vivo measurement of the thyroid using an array of high-purity germanium detectors, (ii) development of a new in vitro bioassay method for the determination of ¹²³I in urine samples using a HPGe germanium detector and (iii) the establishment of a methodology for internal dose assessment, based on bioassay data. The sensitivity of the methods allow detection of ¹²³I activities below derived registry level of 1 mSv for the incorporation scenarios of exposure assumed in this work. Thus, it can be concluded that the methods are suitable for application in routine monitoring of workers occupationally exposed to ¹²³I in this facility.     

Treatment verification and in vivo dosimetry for total body irradiation using thermoluminescent and semiconductor detectors

The objective of this work is the characterization of thermoluminescent and semiconductor detectors and their applications in treatment verification and in vivo dosimetry for total body irradiation (TBI) technique. Dose measurements of TBI treatment simulation performed with thermoluminescent detectors inserted in the holes of a “Rando anthropomorphic phantom” showed agreement with the prescribed dose. For regions of the upper and lower chest where thermoluminescent detectors received higher doses it was recommended the use of compensating dose in clinic. The results of in vivo entrance dose measurements for three patients are presented. The maximum percentual deviation between the measurements and the prescribed dose was 3.6%, which is consistent with the action level recommended by the International Commission on Radiation Units and Measurements (ICRU), i.e., ±5%. The present work to test the applicability of a thermoluminescent dosimetric system and of a semiconductor dosimetric system for performing treatment verification and in vivo dose measurements in TBI techniques demonstrated the value of these methods and the applicability as a part of a quality assurance program in TBI treatments.     

Determination of the radiation dose scattered outside the target volume treated with IMRT technique

Intensity Modulated Radiation Therapy (IMRT) is an advanced mode of high precision radiation therapy that uses computer controlled linear accelerators to deliver precise radiation doses to a malignant tumor or specific areas within the tumor. This is achieved using a more precise adjustment of the beam to the three dimensional shape of the tumor by modulating or controlling the intensity of the radiation beam in multiple small volumes. IMRT also allows higher radiation doses to be focused to regions within the tumor while minimizing the dose to surrounding normal critical structures. This work aims at determining the radiation dose in two target volumes (tumors) treated at same time and the scattered dose distribution in organs at risk using thermoluminescent dosimeters of LiF:Mg,Ti for IMRT treatment technique and a polymethylmethacrylate (PMMA) phantom. The shortest distance between the cavities 1 and 2 that simulate tumors is 1.5 cm and the shortest distances from the cavity 1 to the cavities 3, 4 and 5 are, respectively, 1.9 cm, 2.2 cm and 2.65 cm. The shortest distance from the cavity 2 to cavities 3, 4 and 5 are, respectively, 5.4 cm; 5.7 cm and 1.5 cm. The relative difference for the doses measured by TLD-100 and provided by the TPS were +3.7% and −1.38%. The out-of-target doses received by cavities 3, 4 and 5 corresponded on average to 19.36, 17.84% and 6.72% of the highest dose received by the cavity 1 and the doses received by cavities 3, 4 and 5 corresponded on average to 29.51%, 27.20% and 10.24% of the dose received by cavity 2.     

Luminescent and dosimetric properties of ultrafine magnesium oxide ceramics after high dose irradiation

The luminescent and dosimetric properties of ultrafine MgO ≿eramics synthesized in strongly reducing conditions at Т = 1100–1400 °С are investigated. The growth of photo- and cathodoluminescence output at 2.0–3.5 eV (400–600 nm) is found. It is due to an increase in concentration of single oxygen vacancies and their aggregates. It was established that thermal treatment leads to TL intensity growth after high dose irradiation of the samples by a pulsed electron beam (130 keV). The tunneling mechanism of charge carriers' recombination occurs after this treatment as well. The presence of tunneling recombination is proved by the analysis of the shape and temperature dependence of TL isothermal decay curves. The possibility of using synthesized ceramics for high dose TL dosimetry of ionizing radiations is shown.     

空间辐射环境及人体剂量蒙特卡罗模拟

针对空间辐射环境进行了理论分析,并使用蒙特卡罗方法,对银河宇宙射线及典型太阳质子事件进行了模拟。通过分析常规屏蔽对空间辐射场及人体剂量的影响、屏蔽下的次级粒子产额等,验证了蒙特卡罗工具包Geant4应用于空间辐射防护研究的准确性。模拟发现：在常规屏蔽厚度的情况下,对于太阳质子事件,由于其能量主要分布在低能量段(100 MeV以下),屏蔽效果随屏蔽厚度的增加明显增大,1 g/cm2 Al等效厚度屏蔽皮肤剂量可降低至其初始剂量值的8%左右,10 g/cm2 Al等效厚度的屏蔽可降低至初始剂量值的048%左右;而对于银河宇宙射线,由于其平均能量较高,屏蔽层的屏蔽作用并不明显,在浅层组织剂量甚至有所增加。     

Highly Tuneable Photochromic Sodalites for Dosimetry,Security Marking and Imaging

Photochromic sodalites are considered for a plethora of possible applications, such as UV indexing and X-ray imaging, but for many of these the materials are yet to be optimized. UV indexing can be improved through incremental adjustment of the activation energy of coloration from 300 to 410 nm through replacement of sulfur with selenium. By combining this and other methods of tuning presented in the literature, the excitation threshold and photochromism color can be tuned independently of one another. The range of possible absorption maxima is expanded to 420–680 nm, or almost the entire visible spectrum. Mixing low-cost and easy-to-synthesize sodalites further broadens the possible range of colors and facilitates development of a unique sodalite mix capable of quantifying the doses of two types of UV radiation simultaneously. Finally, the response to X-rays of these highly tuned sodalites is investigated, and it is found that they can be sensitized to produce clear, high-contrast X-ray images at significantly lower doses of radiation than those required by classic photochromic sodalite, Na₈(AlSiO₄)₆(Cl,S)₂.     

Modeling of Free‐radical Crosslinking Copolymerization of Acrylamide and N,N′‐Methylenebis(acrylamide) for Radiation Dosimetry

Over the past decade there has been much interest in the development of three‐dimensional gel dosimeters to aid in the determination of the distribution and magnitude of absorbed dose in clinical radiation therapy. A widely used dosimeter for verification of spatial dose distribution is the polyacrylamide system, sometimes termed polyacrylamide gel (PAG). In this paper, we develop a model to describe the kinetic mechanisms in this gel dosimeter, based on the radiation‐induced copolymerization of acrylamide and bisacrylamide monomers in water and gelatin. Using the proposed model, the conversion of both monomers and total vinyl groups, the concentrations of pendant double bonds (PDB), cyclized groups and crosslinks along the polymer chains as well as temperature changes were simulated. The model predictions and experimental findings in PAG dosimeters agree for a variety of recipes and spatially uniform radiation conditions. Further experiments are required to obtain accurate kinetic parameter estimates and to verify model predictions.

Comparison between the temperatures changes predicted by the model (dotted lines) and experimental data (solid lines) for PAGs irradiated to different doses.