Thermoluminescence (TL) of europium-doped ZrO2 obtained by sol–gel method

This article reports the preparation and characterization of europium-doped zirconium oxide (ZrO₂:Eu³⁺) formed by homogeneous precipitation from propoxyde of zirconium [Zr(OC₃H₇)₄]. The alkoxide sol gel process is an efficient method to prepare the zirconium oxide matrix by the hydrolysis of alkoxide precursors followed by condensation to yield a polymeric oxo-bridged ZrO₂ network. All compounds were characterized by thermal analysis and the X-ray diffractometry method. The thermoluminescence (TL) emission properties of ZrO₂:Eu³⁺ under beta radiation effects are studied. The europium-doped sintered zirconia powder presents a TL glow curve with two peaks (Tmax) centered at around 204 and around 292 ^°C, respectively. TL response of ZrO₂:Eu³⁺ as a function of beta-absorbed dose was linear from 2 Gy up to 90 Gy. The europium ion (Eu³⁺)-doped ZrO₂ was found to be more sensitive to beta radiation than undoped ZrO₂ obtained by the same method and presented a little fading of the TL signal compared with undoped zirconium oxide.     

基于TL494开关电源的设计

开关电源主回路将输入的15VAC电压整流滤波所得的直流电压通过升压斩波电路,变换为25-30VDC输出。主控制器为PIC16F877A单片机。整个系统由整流滤波电路、DC-DC变换器、控制电路、按键显示等模块组成。主控制器和TL494以闭环形式控制DC-DC变换电路,实现输出电压稳定可调。该电源还具有过流保护、自恢复、软启动和短路报警功能。     

Gamma ray induced sensitization of 110°C TL peak in quartz separated from sand

We have investigated the gamma ray induced sensitization of the 110°C TL peak in quartz, separated from sand, in the dose range 30–750 Gy. A pre-dose of 100 Gy followed by annealing at 500°C for 1 h yielded an optimum sensitization factor of 14.2 for a test gamma dose of 0.5 Gy; this factor decreases slowly up to the studied pre-gamma dose of 750 Gy. From ESR studies carried out in the temperature range 25–550°C, the formation of E′₁-centres and their subsequent decay (at temperatures >400°C) have been observed. The released charge carriers (electrons) may lead to elimination of competitors (as a result of their filling up). Thus, the radiation-induced sensitization of the 110°C TL peak could be due to elimination of the competing deep traps.     

Defect centre responsible for production of 110 ∘ C TL peak in quartz

110 ^°C thermoluminescence (TL) peak in quartz is well known due to its pre-dose effect, which is used in dating technique. The generally accepted mechanism for the production of this peak is based on Ge impurity contained in quartz. Its role is to substitute for Si in SiO₄ tetrahedron and under irradiation gives rise to [GeO₄/e^?]^? electron centre. Heating for TL read out liberates electron that recombines with hole in [AlO₄/h]^° or [H₃O₄/h]^° centres emitting photon. The investigation, carried out on blue quartz, green quartz, black quartz, pink quartz, red quartz, sulphurous quartz, milky quartz, alpha quartz and synthetic quartz, has shown that the 110 ^°C TL peak in all these varieties of quartz has no correlation with the respective Ge content. Electron paramagnetic resonance (EPR) measurements on any of these varieties of quartz revealed a signal with g₁=2.0004, g₂=1.9986 and g₃=1.974 and this signal does not appear to correspond to any known EPR signals in alpha quartz. Furthermore, isothermal decay measurements are carried out on the above mentioned EPR signal and 110 ^°C TL peak in alpha, blue and green quartz. A close correlation has been observed in the decay behavior. A new mechanism is proposed based on an interstitial O^? centre.     

Correlating the TL response of γ-irradiated natural quartz to aluminum and hydroxyl point defects

This paper investigates the relationship between Al- and OH-related point defects with the thermoluminescent (TL) response of natural quartz sensitized with high doses of γ radiation and heat-treatments. For this, specimens from a single crystal were progressively irradiated with doses of ⁶⁰Co from 2 to 50 kGy. After each step of sensitization, the absorption bands related to [AlO₄]⁰, [AlO₄/H]⁰, [H₄O₄]⁰ and Li-dependent OH point defects were measured by optical absorption and infrared (IR) spectroscopy. The sensitization of the 280 °C TL peak increased up to 15 kGy and then its intensity remained constant. The absorption intensity at 470 nm increased with γ doses suggesting a progressive creation of [AlO₄]⁰ acting as recombination centers for the sensitized peak. At the same time, the TL intensity of the 90 °C peak decreased with the accumulated dose. This effect was not related to the saturation in the number of recombination centers because both [H₄O₄]⁰ and [AlO₄]⁰ bands were increasing after 50 kGy. Compared to the as-received condition, it was found that IR bands associated with [AlO₄/H]⁰ and Li-dependent OH decreased with the effect of heat-treatments. The precursor for [AlO₄]⁰ is [AlO₄/Li]⁰ and the Li species dislodged from [AlO₄/Li]⁰ and Li-dependent OH centers play an important role in the sensitization process.     

Quantification of cross-irradiation and cross-illumination using a Risø TL/OSL DA-15 reader

The automated Risø TL/OSL DA-15 reader is widely used for luminescence dating applications. The nature of the device is such that the irradiation and illumination of a sample during the OSL procedures may affect discs in adjacent positions. It is critical to confirm that these factors do not introduce significant systematic errors. The effects of such cross-talk (cross-irradiation and cross-bleaching) are examined and quantified, both for specific and general cases. Depending upon the protocol used, cross-irradiation and cross-bleaching could accumulate to have an effect on the D_e estimate, and for the latter this could be significant (i.e. 10%).     

TL15CAI大面积雪崩光电二极管

现代Photonix公司的新型大面积光电二极管是一种全新的光电探测器,它将固态光电二极管探测的优点与普通光电倍增管的许多特性结合在一起。这种二极管的固有增益可达10~3,其有效工作面积大,固体封装直径达到50mm。据Camrillo公司称,这是第一个能在多种应用中与光电倍增管竞争的商用固体产品。据说,TL15CAI是第一个将高增益、大光电灵敏区、低噪声和可靠性集于一身的雪崩光     

Spectroscopy of the gamma and X ray leakage radiation from the built-in sources of a Risø TL/OSL reader

In this work we evaluate the intensity and the spectral shape of the leakage radiation from the built-in beta and alpha sources of a Risø TL/OSL reader. LiF (TLD-100), fluorite-based pellets and Al₂O₃:C detectors were used in order to determine the dose rate delivered to the dosimeters when the sources are closed. The leakage spectra under both alpha and beta sources were registered with a CdTe semiconductor detector. The spectrum measured under the beta source shows the X-ray beam generated by the interaction of the beta particles with the lead used to shield the source. Besides, the 59.4 keV gamma ray from ²⁴¹Am was registered under the alpha source. Dose rates from 50 to 100 μGy/h were obtained for the dosimeter positions in the turntable under the beta and the alpha sources with the luminescent dosimeters.     

Extraction of some trapping parameters from experimental thermoluminescence (TL) signal of alumina (α-Al2O3) using analytical models

The exploitation of thermoluminescence (TL) signals constitutes the background of important and phenomenological methods used for estimating the kinetic parameters such as the activation energy (E), the frequency factor (s) and the general order of kinetics (b). These parameters are, in general, poorly known and all the used methods often diverge on their determined values. In the present paper, we investigate the suitability of the general phenomenological equations used to extract some trapping parameters from experimental TL signals of alumina (α-Al₂O₃). α-Al₂O₃ TL signal exhibits, under hard uv-irradiation (4.8 eV), two TL-main peaks located at 415 nm and 696 nm corresponding to F and Cr³⁺ centers respectively. To this aim, we numerically computed the analytical expression of TL which results from general order kinetic (b) taking into account the trapped charge concentration and the radiative/retrapping yield R. The computed curves for R = 1 fit perfectly the experimental data, allowing the extraction of some TL data as E, b and s from TL bands of alumina.     

On the pre-dose sensitization of the various components of the LM-OSL signal of annealed quartz; comparison with the case of 110 °C TL peak

Pre-dose sensitization of various components of LM-OSL signal of a Nigerian annealed quartz sample has been investigated along side with that of 110 °C TL peak in this work. Successive cycles of irradiations and TL/OSL readings using different heating rates were employed to attain pre-dose sensitization. The results showed that the pre-dose sensitization factor of 110 °C TL peak depends strongly on the heating rate of thermal activation. The pre-dose sensitization of 110 °C TL and all components of RT LM-OSL yield HR dependence on the sensitization after TA. This dependence was ascribed to the different heating time associated with each HR. Sensitization of LM-OSL measured at 125 °C generally does not show dependence on HR of TA. This was with the exception of components C₁ and C₃. Increasing sensitization pattern with increasing HR suggests a correlation between the TL glow-peak at 110 °C, the component C₄ of RT LM-OSL and the component C₃ of the LM-OSL signal at 125 °C. Extension of the present investigation to diverse quartz kinds from different origins was suggested in order to study the prevalence of the pre-dose sensitization on component C₄ of RT LM-OSL. Finally fast heating is suggested for lower sensitization of fast component while applying OSL dating protocols.     

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.     

Effect of γ-radiation on TL,ESR and evaluation of trapping parameters of K2Ca(SO4)2:X (X = Dy or Eu) phosphors

ABSTRACT

The present phosphor K₂Ca(SO₄)_2, doped by dysprosium and europium, is synthesized by the solid-state diffusion method. The doping concentration varied from 0.1 to 0.5?mol% by weight. A phosphor is studied for X-ray powder diffraction, surface morphology analytical scanning electron microscopy and analyzed by energy-dispersive X-ray spectroscopy. The prepared phosphor K₂Ca(SO₄)_2, doped by Dy and Eu, has been characterized for thermoluminescence (TL) glow curve, showing maximum peak temperatures at 176°C and at 200°C, respectively. TL peak intensity of K₂Ca(SO₄)₂: Dy and Eu was compared with the standard TLD CaSO₄:Dy phosphor. Both phosphors show the dose linearity ranging from 20 to 240?Gy doses of γ-rays of ⁶⁰Co source at room temperature. Negligible fading has been observed when irradiated with γ-rays and stored for 60 days without taking any care from sunlight. The TL materials were used in powder forms. The linearity of ESR response with dose for powder forms of K₂Ca(SO₄)₂: Dy was also studied using the signals at g?=?2:0039 (SO₃^?) and at g?=?2:02282 (SO₄^?). It was observed that the range of linearity of dose response extended between 20 and 240?Gy. Kinetic parameters have been calculated using three different methods: Chen's peak shape method, various heating rate method and initial rise method. To study the heating rate method, the glow curve was recorded for the heating rate as 1°C, 3°C, 5°C, 7°C, 9°C each time. Electron spin resonance (ESR) shows the ionic radical formation during γ-irradiation, which is responsible for TL. The effect of temperature and microwave power on the ESR signal was also studied.     

用MPPEST—2专家系统开发工具开发TL—CAPPES专家系统

本文介绍了用ＭＰＰＥＳＴ－２专家系统开发工具开发实用ＴＬ－ＣＡＰＰＥＳ专家系统的方法，并就使用ＣＡＰＰ专家系统开发工具开发实用ＣＡＰＰ专家系统的一些问题进行了分析和探讨。     

TL16C550在一种新型光纤陀螺中的应用

再入式光纤陀螺使相互干涉的两路光在干涉之前循环进入Sagnac光纤敏感环。介绍了这一新型光纤陀螺的原理,采用专门的异步串行通信芯片TL16C550扩展DSP串口,实现陀螺与导航计算机的通讯。结果表明陀螺的数据输出可以达到1kHz,能实现陀螺与导航计算机之间的快速、稳定、准确的数据传输。研制的陀螺零偏稳定性为4.5°/h。     

Radial distribution of dose within heavy charged particle tracks – Models and experimental verification using LiF:Mg,Cu,P TL detectors

A new method of experimental verification of radial dose distribution models using solid state thermoluminescent (TL) detectors LiF:Mg,Cu,P has been recently proposed. In this work the method was applied to verify the spatial distribution of energy deposition within a single ¹³¹Xe ion track. Detectors were irradiated at the Department of Physics of the University of Jyväskylä, Finland. The obtained results have been compared with theoretical data, calculated according to the Zhang et al., Cucinotta et al. and Geiss et al. radial dose distribution (RDD) models. At the lowest dose range the Zhang et al. RDD model exhibited the best agreement as compared to experimental data. In the intermediate dose range, up to 10⁴ Gy, the best agreement was found for the RDD model of Cucinotta et al. The probability of occurrence of doses higher than 10⁴ Gy within a single ¹³¹Xe ion track was found to be lower than predicted by all the studied RDD models. This may be a result of diffusion of the charge, which is then captured by TL-related trapping sites, at the distances up to dozens of nanometers from the ionization site.     

TL–ESR correlation studies in LiMgPO4:Tb,B phosphor

Defect centers formed in irradiated LiMgPO₄:Tb,B phosphor have been investigated using the electron spin resonance technique. O^?, BO₃^2?, PO₂^?, and F⁺ are some of the centers observed in the gamma-irradiated phosphor. The phosphor exhibits thermoluminescence (TL) peaks at around 110°C, 175°C, and 260°C. An attempt has been made to determine the correlation between the defect centers and the observed TL peaks.