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.     

Al2O3:C、LiF:Mg,Ti、LiF:Mg,Cu,P对本底辐射的热释光响应比较

用Al2O3:C、LiF:Mg,Ti、LiF:Mg,Cu,P热释光剂量计(TLD)测量湛江市区本底辐射的热释光响应,以选取适合低辐射场辐射剂量测量的TLD。它们的最低响应剂量依次为Al2O3:C(1–2μGy)、LiF:Mg,Cu,P(约2μGy)和LiF:Mg,Ti(>10μGy)。Al2O3:C的热释光峰温较低,对较长时间段(>30 d)的累积剂量,存在较明显的热释光衰退,剂量响应曲线偏离线性;LiF:Mg,Cu,P和LiF:Mg,Ti的发光峰温较高,数年内都很稳定。综合考虑灵敏度和稳定性,LiF:Mg,Cu,P更宜于低辐射场的累积剂量测量。     

Copper activated LiF nanorods as TLD material for high exposures of gamma-rays

Lithium fluoride (LiF) doped with proper activators is a highly sensitive phosphor commonly used for radiation dosimetry using thermoluminescence (TL) technique. Nanorods of this material activated with Cu, Mg and P as single dopants are synthesized in our laboratory and exposed to gamma-rays for their thermoluminescence (TL) properties. The induced TL glow curves of the Cu, Mg and P doped samples are similar with a single peak at 410 K. Copper doped sample is found to be the most sensitive sample with TL intensity around 65, 7 and 8 times of those of LiF:Mg, LiF:P and LiF:Mg,Cu,P, respectively, indicating that Cu is the luminescence center in the host of LiF nanorods, while Mg and P act as TL quencher particularly when used as codopants. These observations on the nanostructured form of LiF doped with these activators are entirely different from those of the widely studied LiF:Mg,Cu,P and LiF:Mg,Ti single crystals. The nanorods of LiF:Cu might be used for heavy doses measurement as they are sensitive to gamma-rays and have a linear TL response curve in a long span of exposures.     

铜和磷杂质对LiF(Mg,Cu,P)热释光特性的影响研究

ＬｉＦ（Ｍｇ,Ｃｕ,Ｐ）和ＬｉＦ（Ｍｇ,Ｆｉ）热释光磷光体的ＴＬ特性的主要差别在ＴＬ灵敏度,奶量响应和热稳定性三个方面,其产生原因都与铜和磷杂质的掺入有关。ＬｉＦ热释光家族中,镁仍然是一种不可缺少的主要杂质,铜和磷杂质掺入后在磷光体中所形成的电子俘获中心和复合发光中心都与其他ＬｉＦ热释光磷光体有所不同,从而使其具有极高的ＴＬ灵敏性,异常的能量响应和较差的热稳定性。．     

Thermoluminescence and photoluminescence of cerium doped CaSO4 nanosheets

Thermoluminescence (TL) and photoluminescence (PL) characteristics of CaSO₄:Ce nanocrystalline prepared by hydrothermal method has been studied. Its TL glow curve contains three overlapping glow peaks at around 490, 505 and 521 K. Emission spectra band at 303 and 324 nm were observed for the orthorhombic phase of nanosheets. TL response of the prepared nanocrystalline to β and γ radiation was studied and the sensitivity of the nanosheets was found much more than that of analogous microcrystalline and is around 10 times higher than the well known high sensitive TL dosimeter LiF:Mg, Cu, P (GR-200) hot-pressed chips. TL kinetic parameters of this nanocrystalline are also presented.     

LiF（Mg,Cu,P）磷光体的X线衍射分析

对我们实验室制备的LiF(Mg,Cu,P)磷光体的X线衍射分析表明,磷光体制备过程中除生成掺有Mg,Cu和P杂质的LiF晶体外,还产生了焦磷酸锂(Li_4P_2O_7)和另外一种尚不知其组成的晶体。前者(Li_4P_2O_7)对磷光体的灵敏度的稳定性,后者对磷光体的能谱响应有一定影响。     

两种LiF(Mg,Cu,P)片状探测器剂量学特性的比较研究

ＧＲ－２００Ａ与ＭＣＰ－Ｎ均为ＬｉＦ（Ｍｇ,Ｃｕ,Ｐ）片状探测器,现将ＧＲ－２００Ａ和ＭＣＰ－Ｎ在发光曲线,灵敏度,重复使用,抗潮湿性能,本底,探测阈,光敏等性能进行平行对比实验,其中ＧＲ－２００Ａ的灵敏度为ＭＣＰ－Ｎ的１．６倍;６次重复使用的结果ＧＲ－２００Ａ灵敏度无变化 ,ＭＣＰ－Ｎ灵敏度下降了２．６％,抗潮湿性能ＧＲ－２００Ａ更优于ＭＣＰ－Ｎ。     

Measurement of the thermoluminescent response (supralinearity and efficiency) of LiF : Mg,Ti exposed to 0.7 MeV protons

The irradiation of LiF : Mg,Ti (TLD-100) chips by a defocused 0.7 MeV proton beam from an electrostatic accelerator has been achieved using radiochromic dye film to evaluate the beam transversal intensity distribution. The dose-response has been measured at fluences between 2.4 × 10⁸ and 5.7 × 10¹¹ p/cm² and peaks 3–9 show linear-supralinear-sublinear response. The efficiency, relative to ⁶⁰Co γ-rays, measured for the total thermoluminescent (TL) signal and peaks 5 and 7, equals 0.33, 0.22 and 1.4, respectively. The comparison of these and other low-energy data for peak 5 with Track Structure Theory (TST) efficiency calculations indicate that the latter must take into account the stopping of the incident ions in the dosimeter to achieve a reasonable agreement with the observations. In general, neither TST, nor Modified Track Structure Theory (MTST) are able to simultaneously predict the response to 5.3 MeV α-particles and 0.7 MeV protons for all the studied glow curve peaks. Track Interaction Model (TIM) and Unified Track/Defect Interaction Model. (UNIM) calculations of the supralinearity function f(D) of peaks 5 to 8 for 5.3 MeV α-particles and peaks 5 to 9 for 0.7 MeV protons, qualitatively describe the general trends measured in this work; only the UNIM agrees quantitatively with the data in both systems.     

The thermoluminescence properties of natural CaF2 after β-irradiation

In this study, the thermoluminescence (TL) properties of natural CaF₂ were investigated after β-irradiation at room temperature (RT). The additive dose (AD), T_m(E_a)-T_stop, repeated initial rise (RIR), and computerized glow curve deconvolution (CGCD) methods were used to analyze the thermoluminescence (TL) glow peaks in natural CaF₂ after β-irradiation between 0.015 Gy and ≈2 kGy dose level. These methods were used to determine the number of peaks and kinetic parameters (kinetic orders b, activation energy E_a, and attempt-to-escape frequency s) associated with the thermoluminescence (TL) glow peaks of natural CaF₂. The E_a-T_stop and CGCD methods indicate that the glow curve of this material is the superposition of at least six glow peaks, which were dealt with as P1-P6, in the temperature range between room temperature (RT) and 400 °C. Dose variation experiments revealed that TL glow curve of natural CaF₂ has both first and general-order glow peaks. The dose responses and fading process, which are very useful in radiation dosimetry, of individual TL peaks of this material were also examined. In addition, the influence of heating rates on the response of dosimetric glow peaks of natural CaF₂ was studied. It was observed that the total area of glow peak and peak intensities of all glow peaks are continuously decreasing with increasing heating rate.     

Atomic data and spectral line intensities for Mg IX

Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Mg IX. The configurations used are 2s², 2s2p, 2p², 2l3l′, 2l4l′ and 2s5l′, with l = s, p and l′ = s, p, d giving rise to 92 fine-structure levels in intermediate coupling. Collision strengths are calculated at seven incident energies (6, 12, 25, 50, 75, 100, and 125 Ry) for the transitions within the three lowest configurations, and five incident energies (25, 50, 75, 100, and 125 Ry) for transitions between the ground configuration and the n = 3, 4, 5 configurations. Calculations have been carried out using the distorted wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates of the present work, and R-Matrix results for the 2s², 2s2p, 2p² configurations available in the literature, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10⁸-10¹⁴ cm⁻³ at an electron temperature of log T_e (K) = 6.0, corresponding to the maximum abundance of Mg IX. Spectral line intensities are calculated, and their diagnostic relevance is discussed. Observed line ratios indicate electron temperatures of the emitting plasma which agree with log T_e (K) = 6.0. This dataset will be made available in the next version of the CHIANTI database.     

高稳定LiF(Mg,Cu,P)玻璃管探测器的研制及其性能研究

介绍了高稳定ＬｉＦ（Ｍｇ，Ｃｕ，Ｐ）玻璃管探测器的研制及其剂量学性能检验。     

Study on TL and OSL characteristics of indigenously developed CaF2:Mn phosphor

CaF₂:Mn phosphor is known for its high thermoluminescent sensitivity and dose linearity up to few kGy. In the present study CaF₂ phosphor with different concentration of Mn dopant was prepared and was characterized through different techniques. The phosphor was prepared through chemical root using CaCO₃, HF acid and MnCl₂ as raw materials following co-precipitation method. TL sensitivity of the prepared phosphor was compared with other well established phosphors used for radiation dosimetry. It was found that the TL sensitivity is higher by a factor of 10 with respect to LiF:Mg, Ti, TLD-100 and half to that of CaSO₄:Dy (0.05 mol%) phosphor. X-ray diffraction, TL emission spectrum and ESR spectrum taken of the prepared phosphor confirms the crystal structure, Mn²⁺ emission and incorporation Mn in the crystal, respectively. No significant fading of the dosimetric peak was observed of the prepared phosphor for a storage period of 45 days. The dose linearity of the phosphor was found to be in the range of 50 Gy-3 kGy within an uncertainty of about 10%. An attempt was made to determine the kinetic parameters of TL glow curve and the parameters related to optically stimulated luminescence. In view of its long range of dose linearity, it can be used for the dosimetry of commercial irradiator generally used for the irradiation of food and grains in our country.     

Radiation induced defects in BaBPO5:Ce and their role in thermally stimulated luminescence reactions: EPR and TSL investigations

Defect centers induced by gamma irradiation in Ce doped BaBPO₅ were investigated using EPR spectroscopy. From EPR studies, three phosphorous centered radicals were characterized on the basis of observed ³¹P hyperfine splitting and g values as , and radicals. In addition to this, two types of boron oxygen hole centers (BOHC) and O⁻ were also formed at room temperature. An intense broad signal in sample annealed in argon (g_⊥ = 1.9258 and g_‖ = 1.8839) was assigned to Ce³⁺ ions associated with the electron trapped at anion vacancy or nearby lattice defect. TSL studies showed two glow peaks, a relatively weaker one at 425 K and an intense one at 575 K. Spectral studies of the TSL glow peaks have shown that Ce³⁺ ion acts as emission center. From the temperature dependence of the EPR spectra of gamma irradiated samples, the glow peaks at 425 K and 575 K were attributed to thermal destruction of /O⁻ and BOHC, respectively, by trapping of electrons from elsewhere. The energy released in electron hole recombination process is used for the excitation of Ce³⁺ ions resulting in these glow peaks at 425 K and 575 K. The spectral studies of the TSL glow peaks have shown emission at 330 nm indicating Ce³⁺ acts as the luminescent centre. The trap depth and the frequency factor for the 425 K and 575 K peaks were determined using different heating rates method.     

Atomic data and spectral line intensities for Mg VI

Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Mg VI. The configurations used are 2s²2p³, 2s2p⁴, 2p⁵, 2s²2p²3s, 2s²2p²3p, and 2s²2p²3d, giving rise to 72 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies, 12, 24, 36, 48, and 60 Ry. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10⁸-10¹⁴ cm⁻³ at an electron temperature of log T_e (K) = 5.6, corresponding to maximum abundance of Mg VI. Relative and absolute spectral line intensities are calculated and compared with observations of a solar active region.     

Color center creation in LiF crystals irradiated with Xe, Kr and N ions: Dependence on fluence and beam current density

Single LiF crystals were irradiated with Xe (195 MeV), Kr (117 MeV), and N (18 MeV) ions. Using absorption spectroscopy, color center creation was analyzed as a function of the ion energy loss, fluence, and flux. The concentration of single F centers and F₂ centers versus fluence and flux exhibits a nonlinear evolution with saturation at higher fluences. For LiF irradiated with N ions at high fluence, the concentration of F centers is proportional to the cube root of the flux indicating the strong interaction of primary hole centers. Macroscopic hillocks were observed in all irradiated LiF crystals by atomic force microscopy.     

Thermoluminescence properties of irradiated chickpea and corn

A study was carried out to establish a detection method for irradiated chickpea and corn by thermoluminescence (TL) method. The leguminous were packed in polyethylene bags and then the packets were irradiated at room temperature at different doses by ⁶⁰Co gamma source at 1, 4, 8 and 10 kGy. Minerals extracted from the leguminous were deposited onto a clean aluminum disc and TL intensities of the minerals were measured by TL. It was observed that the extracted samples from both leguminous exhibit good TL Intensity and the TL intensity of glow curves of them increased proportionally to irradiation doses. The TL glow curve of both irradiated leguminous presents a single broad peak below 400 °C. The TL trapping parameters glow peaks were estimated by the additive dose (AD), T_m(E_a)-T_stop and computerized glow curve deconvolution (CGCD) methods. The fading characteristics of glow curves were also recorded up to 6 months.     

The thermoluminescent properties of lithium triborate (LiB3O5) activated by aluminium

In this paper, the thermoluminescence (TL) dosimetric characteristics of Al-doped LiB₃O₅ compounds are presented. The powder samples were prepared by the solid-state reaction method and the formation of the compounds were confirmed by an X-ray diffraction study. The TL studies of undoped and Al-doped LiB₃O₅ samples showed similar glow curve structures. They have three TL glow peaks at about 60, 130 and 200 °C after heating at a constant heating rate of 1 °C/s. Their comparative TL studies indicated that 5 wt% Al-doped LiB₃O₅ compound was approximately 240 times more sensitive than undoped compound. The TL emission spectra of Al-doped LiB₃O₅ showed a maximum band at around 520 nm. The main dosimetric characteristics, which are namely the TL dose response, TL sensitivity, fading, minimum detectable dose, reproducibility, precision of dose measurement and annealing procedure, indicated that Al-doped LiB₃O₅ sample, can be used in dosimetric applications. The trap parameters namely order of kinetics (b), activation energy (E) and frequency factor (s) associated with the glow peaks in beta irradiated undoped and Al-doped LiB₃O₅ samples were obtained by glow curve deconvolution (GCD) program.     

Deuterium retention of boron-titanium and reduction of deuterium retention after helium ion irradiations

Deuterium ion irradiations with an ion with energy of 1.7 keV were conducted for boron-titanium (B-Ti) film prepared by electron beam evaporation and hot pressed titanium-boride, TiB₂. The amount of retained deuterium was measured for these materials using a technique of thermal desorption spectroscopy. The amount of deuterium retained in TiB₂ was comparable with that in B-Ti. Desorption peaks of deuterium in B-Ti were 470 K and 620 K, corresponding to a desorption in the low temperature regime observed in boron (B) and a desorption in titanium (Ti), respectively. The desorption peaks in TiB₂ were 620 K and 750 K, which correspond to the desorption in Ti and that in the high temperature regime in B, respectively. The desorption temperature in B-Ti was approximately 100 K lower than that in TiB₂. This difference is discussed based upon chemical bindings and amorphous/crystal structures of B-Ti and TiB₂. Irradiation of helium ion with energy of 5 keV was conducted for B-Ti after the deuterium ion irradiation. The amount of retained deuterium decreased and the desorption temperature shifted to the lower temperature regime, as the helium ion fluence increased. The shift to the low temperature regime is due to the enhancement of amorphous structure of B in B-Ti.     

Robust determination of effective atomic numbers for electron interactions with TLD-100 and TLD-100H thermoluminescent dosimeters

Lithium fluoride thermoluminescent dosimeters (TLD) are the most commonly implemented for clinical dosimetry. The small physical magnitude of TLDs makes them attractive for applications such as small field measurement, in vivo dosimetry and measurement of out-of-field doses to critical structures. The most broadly used TLD is TLD-100 (LiF:Mg,Ti) and, for applications requiring higher sensitivity to low-doses, TLD-100H (LiF:Mg,Cu,P) is frequently employed. The radiological properties of these TLDs are therefore of significant interest. For the first time, in this study effective atomic numbers for radiative, collisional and total electron interaction processes are calculated for TLD-100 and TLD-100H dosimeters over the energy range 1 keV-100 MeV. This is undertaken using a robust, energy-dependent method of calculation rather than typical power-law approximations. The influence of dopant concentrations and unwanted impurities is also investigated. The two TLDs exhibit similar effective atomic numbers, ranging from approximately 5.77-6.51. Differences arising from the different dopants are most pronounced in low-energy radiative effects. The TLDs have atomic numbers approximately 1.48-2.06 times that of water. The effective atomic number of TLD-100H is consistently higher than that of TLD-100 over a broad energy range, due to the greater influence of the higher-Z dopants on the electron interaction cross sections. Typical variation in dopant concentration does not significantly influence the effective atomic number. The influence on TLD-100H is comparatively more pronounced than that on TLD-100. Contrariwise, unwanted hydroxide impurities influence TLD-100 more than TLD-100H. The effective atomic number is a key parameter that influences the radiological properties and energy response of TLDs. Although many properties of these TLDs have been studied rigorously, as yet there has been no investigation of their effective atomic numbers for electron interactions. The discrepancy between the effective atomic numbers of the TLDs and water is significantly higher than would be indicated by comparing effective atomic numbers calculated via the common - but dubious - power-law method. The mean effective numbers over the full energy range are 6.06, 6.09, 3.34 and 3.37 for TLD-100, TLD-100H, soft tissue and water respectively.