The persistent energy transfer of Eu and Mn and the thermoluminescence properties of long-lasting phosphor Sr3MgSi2O8:Eu, Mn, Dy

Eu²⁺, Mn²⁺ and Dy³⁺ co-doped long-lasting phosphors Sr₃MgSi₂O₈ were prepared by a solid-state reaction under a reductive atmosphere. Fluorescence spectra demonstrated that the weak red emission resulting from the forbidden transition of Mn²⁺ could be enhanced by the energy transfer from Eu²⁺ to Mn²⁺. The energy transfer between Eu²⁺ and Mn²⁺ was systematically investigated. The phosphorescence spectra revealed that Eu²⁺ could persistently transfer its energy to Mn²⁺ after removing the excitation source. The duration of Mn²⁺ can prolong to more than 2 h. The thermoluminescence spectra were used to characterize the ability of the trap to trapping the carriers. By the analysis of the ionization potentials, the roles of Mn²⁺ and Dy³⁺ in the afterglow process were discussed. A possible afterglow mechanism was presented and discussed.     

Determination of self attenuation coefficient and relative TL efficiency of CaSO4:Dy, LiF:Mg,Cu,P and LiF:Mg,Ti TLDs - An alternate approach

Self attenuation of TL and relative TL efficiency of polytetra fluoro ethylene (PTFE) embedded CaSO₄:Dy disc, LiF:Mg,Ti (MTS) disc and LiF:Mg,Cu,P (MCP-N) chip were determined in the present study for photons of energy 10-34 keV. The relative TL efficiency was determined using an alternative approach in which ratio of experimental response and corrected theoretical response was used instead of measuring the absolute TL emission in photon counting mode. For CaSO₄:Dy disc, it was found that with increasing the proportion of CaSO₄:Dy phosphor in the disc, the light attenuation coefficient increases. The light attenuation coefficient of MTS disc and MCP-N chip was found to be 23.4 and 45.5 cm⁻¹, respectively. The relative TL efficiency in the photon energy range of 10-34 keV for MTS discs and MCP-N chips, evaluated in the present study matches well with the reported values in the literature.     

Effect of pre-readout annealing treatments on TL mechanism in tellurite glasses at therapeutic radiation doses level

The higher sensitization for thermal annealing on TL mechanism in the region 550–600 °C for 80(TeO₂)–5(TiO₂)–(15 − x) (WO₃)–(x) A_nO_m where A_nO_m = Nb₂O₅, Nd₂O₃, Er₂O₃ and x = 5 mol% has been measured. The behavior of trap centers and luminescence centers has been investigated for tellurite glasses doped with rare earth oxides irradiated at 0.5 up to 2 Gy and annealed at different temperatures in the range 350–700 °C. The behavior of the three types of tellurite glasses is analyzed regarding to their kinetic parameters and luminescence emission which enhance the claim of tellurite glasses for use as TLD material at therapeutic radiation doses.     

Cathodoluminescence and thermoluminescence of ZnB2O4:Eu3+ phosphors prepared via wet-chemical synthesis

In present work, a series of Eu doped zinc borate, ZnB₂O₄, phosphors prepared via wet chemical synthesis and their structural, surface morphology, cathodoluminescence (CL) and thermoluminescence (TL) properties have been studied. Phase purity and crystal structure of as-prepared samples are confirmed by X-ray diffraction measurements (XRD) and they were well consistent with PDF card No. 39-1126, indicating the formation of pure phase. The thermoluminescence (TL) behaviors of Eu activated ZnB₂O₄ host lattice are studied for various beta doses ranging from 0.1 to 10?Gy. The high-temperature peak of Eu activated sample located at 192?°C exhibited a linear dose response in the range of 0.1–10?Gy. Initial rise (IR) and peak shape (PS) methods were used to determine the activation energies of the trapping centres. The effects of the variable heating rate on TL behaviour of Eu activated ZnB₂O₄ were also studied. When excited using an electron beam induced light emission (i.e cathodoluminescence, CL) at room temperature (RT), the as-prepared phosphors generate reddish-orange color due to predominant emission peaks of Eu³⁺ ions located at 576–710?nm assigned to the ⁵D₀→⁷F_J (J=1,2,3, and 4) transitions. The maximum CL intensity for Eu³⁺ ions at 614?nm with transition ⁵D₀→⁷F₂ was reached Eu³⁺ concentration of 5?mol%; quenching occurred at higher concentrations. Strong emission peak for Eu³⁺ ions at 614?nm with transition ⁵D₀→⁷F₂ is observed. The CL experimental data indicate that ZnB₂O₄:Eu³⁺ phosphor as an orange-red emitting phosphor may be promising luminescence materials for the optoelectronic applications.     

Sol-gel synthesis and luminescent properties of nanocrystalline YAP:Mn

The work describes results of synthesis of Mn-doped YAP nanocrystalline samples by the sol-gel method and characterization of the material by X-ray powder diffraction, scanning electron microscopy and luminescence techniques. It was revealed that obtained in such a way YAP samples posses rather poor radiation storage properties that is interpreted by the uniform near-equilibrium synthesis conditions that does not allow formation of Y_Al antisite ions required for electrons trapping. On the other hand, the sol-gel method can be suggested as a suitable technique for obtaining of highly stoichiometric and not defected structure material without parasitic charge capturing and recombination processes that is very essential e.g. for scintillator materials.     

Simulations of thermally transferred OSL signals in quartz: Accuracy and precision of the protocols for equivalent dose evaluation

Thermally-transferred optically stimulated luminescence (TT-OSL) signals in sedimentary quartz have been the subject of several recent studies, due to the potential shown by these signals to increase the range of luminescence dating by an order of magnitude. Based on these signals, a single aliquot protocol termed the ReSAR protocol has been developed and tested experimentally. This paper presents extensive numerical simulations of this ReSAR protocol. The purpose of the simulations is to investigate several aspects of the ReSAR protocol which are believed to cause difficulties during application of the protocol. Furthermore, several modified versions of the ReSAR protocol are simulated, and their relative accuracy and precision are compared. The simulations are carried out using a recently published kinetic model for quartz, consisting of 11 energy levels. One hundred random variants of the natural samples were generated by keeping the transition probabilities between energy levels fixed, while allowing simultaneous random variations of the concentrations of the 11 energy levels. The relative intrinsic accuracy and precision of the protocols are simulated by calculating the equivalent dose (ED) within the model, for a given natural burial dose of the sample. The complete sequence of steps undertaken in several versions of the dating protocols is simulated. The relative intrinsic precision of these techniques is estimated by fitting Gaussian probability functions to the resulting simulated distribution of ED values. New simulations are presented for commonly used OSL sensitivity tests, consisting of successive cycles of sample irradiation with the same dose, followed by measurements of the sensitivity corrected L/T signals. We investigate several experimental factors which may be affecting both the intrinsic precision and intrinsic accuracy of the ReSAR protocol. The results of the simulation show that the four different published versions of the ReSAR protocol can reproduce accurately the natural doses in the range 0-400 Gy with approximately the same intrinsic precision and accuracy of ∼1-5%. However, these protocols underestimate doses above 400 Gy; possible sources of this underestimation are investigated. Two possible explanations are suggested for the modeled underestimations, possible thermal instability of the TT-OSL traps, and the presence of thermally unstable medium OSL components in the model.     

石英前剂量热释光影响因素研究

围绕石英前剂量110℃峰TL信号的测量,进行了石英样品处理、仪器测量参数优化,并研究了石英样品110℃峰TL响应与石英粒度、激活温度和激活时间的关系,建立了石英前剂量TL测量方法。     

氟化锂热释光探测器剂量特性的实验研究

对本实验室的ＢＩＲＭ系列中的ＬｉＦ：Ｍｇ，Ｔｉ，ＬｉＦ：Ｍｇ，Ｔｉ－Ｍ，ＬｉＦ：ｍＧ，Ｃｕ，Ｐ热释光探测器的剂量学特性进行了实验研究，并参加了国产ＬｉＦ片热释光探测器的性能比对。结果表明，所研制的ＬｉＦ系列热释光探测器符合《个人和环境监测用热释光剂量测量系统》国家标准的技术要求，本文还就有关问题作了讨论。     

元代云龙纹象耳瓶的热释光年代测定

介绍了古瓷器赝品的克星——“热释光前剂量激活法”检测3件元代青花云龙纹象耳瓶和1件元代釉里红云龙纹象耳瓶的烧制年代。它们的热释光年代均小于距今100年。其中一件釉里红云龙纹象耳瓶与一件青花云龙纹象耳瓶都为近几年烧制。对于测定年龄小于距今1000年的瓷器,本方法是一个快速、简便、有效的检测手段。为了便于比较,同时测定了一件元代青花瓷片,它的热释光年代为距今620±140a。另外对一些与测定年代有关的复杂因素进行了讨论并提出了解决办法。     

GR-200A LiF(Mg,Cu,P)圆片不退火应用研究

通过改变升温速度,最大读出温度及恒温时间等参数研究了性能改善的ＧＲ－２００Ａ重复使用中的灵敏度,残余信号和发光曲线的变化情况,探讨了不退火重复使用的可能性,结果表明采用最大读出温度２４０℃,恒温时间２０ｓ,升温速率为６℃／ｓ时能达到残余信号减少到小于０．５％,且重复使用中灵敏度稳定,发光曲线不发生变化,删除了辐照前退火炉退火的需要。