Dosimetric characterization of a new preparation of BaSO4 activated by Eu ions

The results of a thermoluminescent investigation carried out on a new preparation of BaSO₄ activated by Eu ions at different concentrations (0.1, 0.5 and 1.0 mol%) are reported in this paper. Several batches were prepared by varying Dy, Tm and Sm ions concentrations. The TL sensitivity property of each of the doped barium sulphate samples were compared to the BaSO₄:Eu. The highest sensitivity was found for BaSO₄:Eu (0.5 mol%). The main dosimetric characteristics, i.e. thermoluminescent (TL) response as a function of the dose, reproducibility, lower detection limit, and fading, have been investigated for the BaSO₄:Eu. Furthermore, the kinetic parameters, i.e. activation energy, E, the frequency factor, s, the pre-exponential factor s^* and the kinetic order, b, have been calculated using initial-rise and deconvolution methods. The peak shape methods related to the geometric properties of a TL peak were also used. In order to analyse the TL response at different energies, the effective atomic number (Z_eff = 45–47) for this material was determined.     

A versatile integrated system for thermoluminescence and optically stimulated luminescence measurements

A versatile integrated reader system for TL and OSL measurements of phosphor materials has been described for luminescence research applications. The developed integrated reader system works either in TL or OSL or TL-OSL mode. In the OSL operation, besides the conventional CW-OSL, POSL and LM-OSL modes a novel non-linear OSL (NL-OSL) method has been incorporated in the reader system. The optical stimulation unit consists of four high power LEDs fitted in four channels and optically focused on the sample. Each of the LED is capable of delivering up to 80 mW/cm² light power at the sample position. The LEDs with peak wavelength λ_p ≈ 470 nm and 530 nm and Δλ ≈ 20 nm have been used for optical stimulation of the samples. A PID temperature controller has been used for generating and controlling user defined heating profiles for the TL measurements in the reader system. The reader system covers a wide dynamic dose range of 10 μGy to 10³ Gy for TL/OSL measurements. The OSL grade α-Al₂O₃:C phosphor was used to test the reader system and investigate its impact on low dose assessment for personnel and environmental monitoring. The design concept of the reader system and the results of dose measurements are discussed.     

In-core thermal high-neutron fluence measurement by TLD-activation method

Thermal neutron fluence between 10¹⁴ and 10¹⁸ n/cm² in the Health Physics Research Reactor-Core of Tehran was measured conveniently by a TLD reader using the ⁶Li(n,)³H reaction in TLD-700. The primarily induced thermoluminescence (TL) by irradiation of the crystal in the reactor core was first cleared by annealing. The secondary TL of TLD-700 produced after a storage time by the absorbed energies of decayed tritons in crystal was used as a basis for assessment of prior exposure to neutrons. A thermal treatment stabilized the readings of the high-dose-irradiated dosimeters and reduced the influence of radiation damage in TLD-700. The response reduction as a consequence of high-dose radiation was corrected by Elemental Correction Coefficients (ECC) using gamma responses prior to in-core irradiation. The resulting correlation between neutron fluence and build-up TL of TLD-700 as a consequence of internal activity is presented.     

Photoluminescence,thermoluminescence and reversible photoluminescence modulation of multifunctional optical materials Pr3+ doped KxNa1-xNbO3 ferroelectric ceramics

It is highly significant to develop multifunctional optical materials to meet the huge demand of modern optics. Usually, it is difficult to realize multiple optical properties in one single material. In this study, we choose ferroelectric (K_xNa_1-x)NbO₃:Pr³⁺ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) as hosts, and the rare earth ions Pr³⁺ are doped in them. For the first time, the integration of photoluminescence, photochromism, luminescence modulation and thermoluminescence and has been achieved in the Pr³⁺ doped (K_xNa_1-x)NbO₃:Pr³⁺ ferroelectric ceramics. Upon 337- or 448-nm light irradiation, all samples show strong red emissions centered at 610 nm. The photochromic reaction increases with the increasing K⁺ content in the (K_xNa_1-x)NbO₃:Pr³⁺ ceramics. A strong photochromic reaction has been found in the (K_0.5Na_0.5)NbO₃:Pr³⁺ ceramics. Accordingly, a large and reversible photoluminescence modulation (ΔR_t = 50.71%) is achieved via altering 395-nm-light irradiation and 200 °C thermal stimulus. All the prepared ceramics show a visible thermoluminescence when stimulated at 200 °C. The mechanisms of luminescence modulation and thermoluminescence are discussed. Present study could provide a feasible paradigm to realize multiple optical properties in one single material.     

Radiation Synthesis of Grafted Polymers for Studying Thermoluminescence Characterization and Its Possible Application as a Dosimeter at Low Doses

Radiation-induced graft copolymerization of binary monomer system acrylic acid/acrylamide (AAc/AAm) (50/50) onto low density polyethylene (LDPE) and polypropylene (PP) films were investigated. Sulfonation was carried out for the prepared graft copolymers using concentrated sulfuric acid (97%) at 60°C for 15 min. The sulfonated grafted films found to have a thermal stability and better hydrophilic character than the grafted ones due to the ionic character resulting from this conversion. The thermoluminescence (TL) characteristics of grafted and sulfonated films were studied with regard to their use as off-line dosimeters in radiotherapy. The structural characterizations were performed by using FTIR, DSC and TGA. The sulfur content was determined by elemental analysis (EA). The TL responses were tested with ⁶⁰Co beam in the dose range 0.1–7 Gy. The dosimetric characterization has yielded a very good reproducibility, and independence of the radiation energy. The TL signal is not influenced by the dose rate and exhibits a very low thermal fading. Moreover, the sensitivity of the samples compares favorably than that of standard TLD-100 dosimeters. Finally, at the same dose the TL response for LDPE-g-P (AAm/AAc) films is higher than that of PP-g-P (AAm/AAc) and the sulfonated grafted films are more sensitive to radiation than the grafted ones.     

2012-2018年度重庆市某医院放射诊疗工作人员职业照射个人剂量监测与评价

采用职业性外照射个人剂量常规监测方法,对重庆某医院放射诊疗工作人员职业性外照射个人剂量进行了监测。监测结果显示,该院2012—2018年度放射诊疗工作人员职业性外照射人均年有效剂量为0.3～0.8 mSv,远低于国家标准中职业照射人员的年剂量限值规定;职业类别年有效剂量,介入放射学>放射治疗>核医学>放射诊断。     

Persistent luminescence from Y_3Al_2Ga_3O_(12) doped with Ce~(3+) and Cr~(3+) after X-ray and blue light irradiation

The persistent luminescence(PersL) dependence on the dopants and derived mechanism of trapping and de-trapping processes were investigated in Y_3Al_2Ga_3O_(12)(YAGG) based nanophosphor,doped with Ce~(3+) and/or Cr~(3+).It is found that the presence of Cr~(3+) ions produce electron and hole traps and capture suitable charge after X-ray irradiation.The effect of irradiation on the carriers trapping and their pathways after excitation was studied by means of thermo luminescence technique.On the other hand,for blue light irradiation the mechanism seems to be different.In the latter case,the Ce~(3+) ions,having the position of energy levels in the conduction band,become sensitizers for the electrons and main emission centres for the PersL(de-trapping process goes through Ce~(3+)).     

蒙特卡罗方法用于LiFTLD自屏蔽因子的模拟计算

自屏蔽因子是用LiFTLD探测器高精度测量n-γ混合场的重要参数.本文采用MCNP程序对文献中给定尺寸、密度和6Li含量的LiFTLD的自屏蔽因子进行了计算,并与推导的自屏蔽公式、Horowitz等的计算结果进行了比较.同时,对计算结果还专门设计了实验进行验证,证实MCNP计算自屏蔽因子所采用的模型和方法是可靠的.对于文献中没有给出自屏蔽因子的现有的LiFTLD,通过选取合理的模型,用MCNP计算了它们的自屏蔽因子.该研究结果对于n-γ混合场区分测量以及TLD的LET效应的研究都具有重要意义.     

热释光发光曲线分析

利用计算机对热释发光曲线进行解谱（CGCD），是现代热释光测量技术的重要进展之一，它大大增强了热释光测量的精度和有效性，扩大了其应用范围。本文概述了热释光发光曲线分析所需要考虑的模型和算法，以及对结果的评价。