OSL Intensity Research Articles

Optical, scintillation, and dosimetric properties of undoped and Mn-doped MgGa2O4 single crystals

Optical, scintillation, and thermally and optically stimulated luminescence (TSL and OSL) properties of the undoped and Mn-doped MgGa2O4 single crystals were investigated. All the crystals showed a luminescence peak at 500 nm caused by the 3d–3d transitions of Mn2+. The 0.03 %-Mn-doped crystal exhibited the highest OSL intensity, whereas the 0.3 %-Mn-doped crystal exhibited the highest photoluminescence quantum yield and scintillation intensity. There was an inverse relationship between the scintillation and OSL intensity in the 0.03–0.3 % Mn-doped crystals. The results indicated that the 0.03 % Mn-doped crystal exhibits the highest efficiency during carrier trapping. In the OSL dose response functions, the lower detection limit of the 0.03 % Mn-doped crystal was 0.01 mGy, which was comparable with that of a commercial product.

Study of non-exponential OSL decay curve within critical physical conditions of synthetic quartz material and their resolution by selection of suitable protocol

Researchers had reported that synthetic quartz which was annealed either at 400 °C irradiated by 75.6 Gy beta doses or at 600 °C irradiated by 25.2 Gy beta doses showed better rise in OSL intensity at room temperature depicting the change from non-exponential to exponential shape of the decay curve. Under these conditions, the non-exponential shape of decay curve with weaker OSL intensity was observed. It was due to re-trapping of optically released electrons by shallow traps corresponding to 110 °C TL glow peak and it was later verified by ESR spectra.In order to eliminate the non-exponential behaviour of decay curve, the researchers suggested OSL measurement at elevated temperature so as to further remove the contribution of shallow traps. However, in the present work, the OSL decay curves are recorded at 160 °C for 400 °C and 600 °C annealed samples irradiated by 2.52 Gy, 5.04 Gy, 25.2 Gy and 75.6 Gy beta doses. Both the samples show non-exponential shape of OSL decay curve up to 25.2 Gy beta doses. However, it gradually changes to exponential shape with better OSL intensity at higher beta doses. Additionally, few attempts were made to examine the non-exponential pattern of OSL decay at room temperature as well as elevated temperature within respective critical conditions by using fitting equations. It reports that various mode of non-exponential patterns of curve and their changes were influenced by strength of physical conditions. Further, a new protocol of cyclic sequence of doses, pre-heat up to 200 °C, test dose and stimulation at 125 °C for 40 s stimulation time was implemented to identical treated samples. It shows disappearance of non-exponential shape of OSL decay by growth in OSL intensity. These changes in OSL pattern were further justified by the contribution of annealing, irradiation, thermal transfer and thermal assistance process and TL measurements before and after OSL.

Evaluation of scintillation and dosimetric properties of undoped and Tb-doped Ba3Y(PO4)3 single crystals

Undoped and Tb-doped Ba3Y(PO4)3 single crystals were synthesized by the floating zone method. Photoluminescence (PL), scintillation, and dosimetric properties of the obtained single crystals were measured. The highest PL quantum yield value was obtained from the 15% Tb-doped crystal. In X-ray-induced scintillation spectra, the undoped crystal showed an emission peak due to self-trapped exciton at 400 nm. Tb-doped crystals showed emission peaks in the range of 375–620 nm, originated from 4f-4f transitions of Tb3+. In addition, the undoped and Tb-doped crystals showed luminescence peaks in similar locations to the scintillation spectra in thermally and optically stimulated luminescence (TSL and OSL). In TSL dose response functions, the 1% Tb-doped sample exhibited the highest TSL intensity, and the TSL signal was detectable from 0.01 mGy. In OSL dose response functions, the 5% Tb-doped sample exhibited the highest OSL intensity, and the OSL signal was observed from 0.1 mGy.

OSL and TA-OSL properties of Li2B4O7:Al for radiation dosimetry

Lithium tetraborate is one of the tissue equivalent material that has been modified with numerous dopant/codopant to improve its Thermoluminescence and Optical stimulated Luminescence properties. Lithium tetraborate doped with Aluminum is being investigated for Optical stimulated Luminescence dosimetry in this paper. Polycrystalline nano-phosphor samples were synthesized using two step solid state reaction method with optimized concentration of Aluminum equals to 2% (by wt.). Formation of the same and its morphology was confirmed using X-ray Diffractometry and Transmission Electron Microscopy. The various dosimetric properties of the obtained phosphor along with related Optical stimulated Luminescence kinetic parameters have been studied. The phosphor exhibits good linearity for gamma radiation in the range of 0.1–500 Gy with other properties such as low fading, satisfactory reusability & reproducibility and minimum detectable dose of 0.05 Gy. In this paper we have also explored the Temperature-Assisted Optical stimulated Luminescence properties of the obtained phosphor in the range of 25 ֯C to 200 ֯C and the optimized temperature corresponding to the maximum Optical stimulated Luminescence intensity was found to be 125 ֯C with activation energy equals to 0.108 ± 0.02 eV. The studied nanophosphor has also shown linear response with dose gamma (1–200 Gy) and beta (0.05–3 Gy) at 125 ֯C. • Tissue equivalent Li 2 B 4 O 7 :Al nanophosphor is developed using solid state reaction with two stage heating process. • The optimized level of Al doping in Li 2 B 4 O 7 shows non-toxic, robust response for reusable dosimetry. • CW-OSL/TA-OSL studies of gamma and beta irradiated Li 2 B 4 O 7 :Al are reported for the first time. • Linear CW-OSL/TA-OSL response in the observed dose range has been observed. • Optimized elevated temperature corresponding to the maximum OSL intensity is found to be 125 ֯C. • Activation energy equals 0.108±0.02 eV is calculated using Arrhenius equation.

Particle size effect on TL/OSL response of NaMgF3:Tb phosphor

NaMgF3 is a nearly tissue equivalent material with low Zeff = 10.4 and a well-known phosphor for its high sensitivity concerning luminescence. The type of preparation route followed greatly affects the luminescence efficiency of a material. Grinding of NaMgF3:Tb phosphor for a long time induces several lattice defects in the phosphor. In this work, effect of particle size on TL/OSL response of NaMgF3:Tb irradiated by 60Co source of gamma radiations with a dose of 15 Gy has been investigated. NaMgF3:Tb samples has been synthesized by solid state reaction method using different grinding times i.e. 1 h and 5 h. XRD technique confirms its formation and crystallite size is calculated. TL studies show that sample synthesized by 5 h grinding is almost 2 times more intense than the sample obtained by 1 h grinding. Also, a clear enhancement is seen in the shoulder peak of sample grinded for 5 h. This could be due to increase in occupancy of trapped charge carriers in the trap levels. However, the position of main TL glow peak remains same in both the samples. Associated TL kinetic parameters such as order of kinetics, activation energy, frequency factor and trap density have been calculated by deconvoluting the TL glow peaks to understand the TL phenomenon. Continuous-wave optically stimulated luminescence (CW-OSL) decay curves have been obtained under blue LED stimulation for 40 s. Analyzing the CW-OSL decay curves reveal that grinding time significantly affects the OSL intensity of the phosphor as well. The decay constant and photoionization cross-section is determined for the faster and slower components of the total OSL intensity. It could be concluded that the time of grinding taken during preparation of the material has a major role in affecting the concentration of trap levels formed inside the forbidden gap of the phosphor.

Luminescence characteristics of silver and rare earth co-doped KCl single crystals grown from melt using Czochralski technique

Single crystals of KCl:Ag, KCl:Ag,Eu and KCl:Ag,Ce were grown from melt using Czochralski technique and investigated for thermally (TSL) and optically stimulated luminescence characteristics (OSL) with main focus on dosimetric applications. The XRD of crystals showed good crystalline nature with a face centered cubic KCl structure. SEM and EDAX analysis confirmed the distribution of dopants in the host lattice. Thermo luminescence (TL) emission of KCl:Ag after irradiating with 60Co gamma rays showed two TL glow peaks around 100 °C and 150 °C. An enhanced TL intensity of 3.5 times and OSL intensity of 1.5 times were observed by co-doping KCl:Ag with Ce. The result is further confirmed by taking photoluminescence and TL emission spectra of the samples. This increased TL and OSL response for KCl:Ag,Ce crystal is attributed to the formation of Vk centers formed due to the doping of Ag in KCl and the F center formed by Ce2+ on irradiation. Dose response of KCl:Ag,Ce showed linearity up to 6 Gy indicating its use in the personal dosimetry applications.

Fabrication and characterization of a composite dosimeter based on natural alexandrite

This work aims at demonstrating the fabrication of a new composite material based on the micron-sized powder of the alexandrite mineral (BeAl2O4:Cr3+) dispersed in a fluorinated polymer for OSL dosimetric applications. Composites with 50 wt% alexandrite powders were obtained and characterized in their chemical composition, mechanical, and luminescent properties. Energy dispersive X-ray spectroscopy mapping measurements of the pellets revealed a homogeneous distribution of alexandrite particles throughout the organic matrix. PL measurements showed the signal related to Cr3+ ions in alexandrite remained active besides all fabrication steps, and tensile tests showed the pellets to have good ductility and tensile strength. The OSL results showed the integrated intensity signal varied linearly with the beta irradiation dose and that the pellets were stable at room temperature over time of 28 days. Nevertheless, improvements in the fabrication process are necessary toward obtaining the same OSL intensity from different pellets.

Growth, Metabolites, Protein Profile and Esterase Enzyme of Wheat Grown under Osmotic Stress with Exogenous Application of <i>Allium sativum</i>

The present work was conducted to lower and alleviate the saline injury by using natural products in garlic extract application on growth, metabolites, protein pattern and esterase enzyme of wheat plants. This study was conducted that wheat plant cv. Gimiza 11 response to osmotic stress effects and in general showed a variable response between different organs. The aerial parts of plants not only alleviated salinity injury but activated the fresh and dry matter productions. In root these parameters decreased as increasing salinity stress. Length of the shoots, roots and spikes run parallel with the previous results. Photosynthetic pigment enhanced markedly the increasing osmotic stress levels. The effect of garlic was reflected on the accumulation of soluble sugar and soluble protein in both roots and spikes, and a reduction of Na+ and an increase in K+ under garlic treatments were recorded. In the present study, staining intensity of protein bands of wheat plant was decreased as osmotic stress increased but the number of bands was increased up to -0.9 MPa, after that level a slight decrease was recorded (for control induction, 12 bands, -0.3 MPa, 16 bands, -0.6 MPa 14 bands, -0.9 14 bands, -1.2 MPa 11 bands and final 11 bands for -1.5 MPa). Induction protein bands for control plus garlic were 12 bands, for -0.3 MPa OSL plus garlic were 13 bands, for -0.6 MPa OSL plus garlic were 12 bands, for -0.9 MPa OSL plus garlic were 12 bands, for -1.2 MPa OSL were 8 bands and finally for -1.5 MPa OSL plus garlic were 9 bands. Electrophoresis studies of esterase showed wide variations in their intensities and densities among all treatments. There were 6 isozymes forms of esterase under OSL and with garlic but intensity was different. It seems that garlic extract was able to enhance the tolerance of the wheat plant to osmotic stress.

Investigation of the role of the production process on the luminescence of sea salt products

Abstract Luminescence dosimetry assumes samples of a given material with diverse provenances behave in a predictable manner, allowing a standardised testing protocol, such as SAR for quartz, to be employed. This article demonstrates that distinct salt products derived from a single manufacturer’s feedstock retain comparable luminescence behaviour. This is the basis of a standardised test protocol: uniting testing procedures which have been shown to be individually applicable. Generalization across samples from different manufacturers and processes is currently under investigation. Luminescent evaluation of five samples produced by Cheetham & Co. gave useful intensities for all emission bands (590 nm, 420 nm and 360 nm TL and blue stimulated OSL), with the spectral and intensity balance of emissions generally similar for each sample. 590 nm emission sensitization was noted after preheating samples to 135°C and 300°C for five minutes. But, the 360 nm TL emission from feedstock salt was a factor of five greater than the same signal from the other processed samples despite the OSL intensity being similar to the other samples. Spectrum variation between aliquots as measured by the 3D TL spectrometer was also investigated and found to be minimal for both the first and second TL glow cycles.

Optically stimulated luminescence of borate glasses containing magnesia, quicklime, lithium and potassium carbonates

The OSL characteristics of three different borate glass matrices containing magnesia (LMB), quicklime (LCB) or potassium carbonate (LKB) were examined. Five different formulations for each composition were produced using a melt-quenching method and analyzed in terms of both dose-response curves and OSL shape decay. The samples were irradiated using a 90Sr/90Y beta source with doses up to 30Gy. Dose-response curves were plotted using the initial OSL intensity as the chosen parameter. The OSL analysis showed that LKB glasses are the most sensitive to beta irradiation. For the most sensitive LKB composition, the irradiation process was also done using a 60Co gamma source in a dose range from 200 to 800Gy. In all cases, no saturation was observed. A fitting process using a three-term exponential function was performed for the most sensitive formulations of each composition, which suggested a similar behavior in the OSL decay.

Optically and Thermally Stimulated Luminescence in X-Ray Irradiated Sno-Doped Sro-B2O3 and ZnO-P2O3 Glasses for Passive-Type Dosimeter

Optically and thermally stimulated luminescence (OSL and TSL) phenomenon is based on the presence of electron and/or hole traps and luminescence centers in storage phosphor materials. During exposure to ionizing radiation such as x-ray, γ-ray and β-ray, the traps are occupied with charged carriers such as electrons and holes that are created by irradiation with ionizing radiation. De-trapping of these carriers requires energy. The energy is provided by stimulating of the phosphor materials with visible or infrared light (OSL) or by heating of the phosphor (TSL). During a de-trapping transition, free carriers created by the absorption of photons from the stimulating radiation field, recombine with the luminescence centers, whereby visible photons are emitted. Since the OSL or TSL intensity is in the most cases proportional to absorbed dose of ionizing radiation, the phosphor materials which exhibit the OSL and TSL phenomena adapt to two-dimensional imaging sensor for ionizing radiation. Although imaging plate (IP) using photostimulable phosphor materials such as BaFBr:Eu [1,2] and CsBr:Eu [3] can be now used as two-dimensional sensor for ionizing radiation, these phosphor materials with deliquescent property exhibit poor fading characteristics which is one problem on two dimensional radiation dose estimation using the IP. As a result of surveying many possible phosphor materials, we found that SnO-doped SrO-B2O3 and ZnO-P2O3 glass without deliquescent properties exhibit an efficient OSL and TSL, and good fading characteristics. Typical OSL stimulation and emission spectra of x-ray irradiated SnO-doped SrO-B2O3 glass are shown in Fig.1. In this work, the OSL and TSL characteristics in x-ray irradiated SrO-B2O3 and ZnO-P2O3glasses are in the first time reported and OSL and TSL characteristics are discussed for the passive type dosimeter. Ref. [1] K.Takahashi et al., J. Electrochemcal Soc., 32(1985) 1492.[2] M.Takebe and K.Abe, Nuclear Instruments and Methods, A345(1994) 606.[3]H.Nanto et al., Nuclear Instruments and Methods, A580 (2007)278. Figure 1

Ooptically and Thermally Stimulated Luminescence in x-Ray Irradiated Sn-Doped Sro-B2O3 and ZnO-P2O3 Glasses for Passive-Type Dosimeter

Optically and thermally stimulated luminescence (OSL and TSL) phenomenon is based on the presence of electron and/or hole traps and luminescence centers in storage phosphor materials. During exposure to ionizing radiation such as x-ray, γ-ray and β-ray, the traps are occupied with charged carriers such as electrons and holes that are created by irradiation with ionizing radiation. De-trapping of these carriers requires energy. The energy is provided by stimulating of the phosphor materials with visible or infrared light (OSL) or by heating of the phosphor (TSL). During a de-trapping transition, free carriers created by the absorption of photons from the stimulating radiation field, recombine with the luminescence centers, whereby visible photons are emitted. Since the OSL or TSL intensity is in the most cases proportional to absorbed dose of ionizing radiation, the phosphor materials which exhibit the OSL and TSL phenomena adapt to two-dimensional imaging sensor for ionizing radiation. Although imaging plate (IP) using photostimulable phosphor materials such as BaFBr:Eu [1,2] and CsBr:Eu [3] can be now used as two-dimensional sensor for ionizing radiation, these phosphor materials with deliquescent property exhibit poor fading characteristics which is one problem on two dimensional radiation dose estimation using the IP. As a result of surveying many possible phosphor materials, we found that SnO-doped SrO-B2O3 and ZnO-P2O3 glass without deliquescent properties exhibit an efficient OSL and TSL, and good fading characteristics. In this work, the OSL and TSL characteristics in x-ray irradiated SrO-B2O3 and ZnO-P2O3 glasses are in the first time reported. Ref. [1] K.Takahashi et al., J. Electrochemcal Soc., 32 (1985) 1492. [2] M.Takebe and K.Abe, Nuclear Instruments and Methods, A345 (1994) 606. [3]H.Nanto et al., Nuclear Instruments and Methods, A580 (2007)278.

OSL強度より推定された天竜川～遠州灘海岸における砂粒子の運搬－堆積過程

OSL強度より推定された天竜川～遠州灘海岸における砂粒子の運搬－堆積過程

Optically stimulated luminescence and thermoluminescence in some Cu+ doped alkali fluoro-silicates

OSL and TL in some Cu doped alkali fluoro-silicates were studied. These investigations show that the materials possess good OSL properties and the sensitivity is comparable to that of the commercial α-Al2O3:C phosphor. Of the several fluoro-silicate phosphors studied Cu doped Na2SiF6 is found to be highly sensitive. The initial OSL intensity averaged over first second using blue and green light stimulation, were found to be 1.2 and 13.3 times respectively of Al2O3:C. The simple preparation procedure, high OSL sensitivity, fast decay, and high photoionization cross-section will make these phosphors suitable for on-line radiation dosimetry, particularly in medical dosimetry applications.

Blue and infra-red stimulated luminescence in Cu+ doped fused quartz for application in radiation dosimetry

Cu+ was doped in fused quartz using simple technique and the BSL/IRSL and TL studies were carried out. The Cu+ doped quartz shows enhanced TL as well as OSL sensitivity compared to the undoped material. The OSL sensitivity with blue stimulation, in particular, is relatively high, about 13% of the commercially used OSL phosphor (Al2O3:C-Landauer Inc.) on the basis of initial OSL intensity measurements (i.e. luminescence averaged over first 3s). Earlier works show that OSL/TL signals in natural quartz is stable and thus can be used in archeological dating and other dosimetric applications. The aim of the present study is to investigate TL/OSL characteristics of Cu+ doped fused quartz.

Improving the reliability of single-aliquot regenerative dose dating using a new method of data analysis

The study of quartz grains (diameter 90–125 μm) from a modern dune sand from Australia shows a lack of perfect proportionality between the regenerated OSL (L) signal and the subsequent test dose OSL (T) signal when using a single-aliquot regenerative dose (SAR) procedure with a fixed 15 Gy dose repeated five times. This lack of perfect proportionality results in both a broad De distribution and systematic offset for the doses measured both with and without a preheat step at the end of each cycle of the SAR procedure. The problems caused by the lack of proportionality are overcome by a new method of handling the data generated by use of the SAR protocol; the OSL intensity is sensitivity-corrected using the slope of a plot of L versus T obtained from a number of aliquots, rather than the ratio of L/T obtained for individual aliquots. This approach is validated using laboratory irradiated quartz with given doses ranging from 5 Gy to 60 Gy; for the larger doses, correct values can be recovered using the new data analysis procedure is applied, but not when using the ratio of L/T obtained using conventional SAR analysis.

Neutron detection efficiency of Al2O3:C coated with various thicknesses of Li using OSL

Abstract Over recent years, significant developments in OSL have been made regarding radiation dosimetry, age determination, and medical applications. In these applications, Al 2 O 3 :C has attracted great interest as the most promising material because of its excellent OSL properties. Although Al 2 O 3 :C has a high sensitivity to alpha, beta, and gamma radiation, the material has the disadvantage of insufficiency of sensitivity to neutrons. In this study, we have investigated neutron detection efficiency of Al 2 O 3 :C crystal coated with various thicknesses of Li using OSL. As a result, the OSL intensity increases as the thickness of Li becomes thicker, up to 7.6 μm thickness of Li investigated in this study. In addition, we found neutron detection sensitivity was not linearly proportional to the thickness of Li.

Optically stimulated luminescence in LiF:Mg,Ti: Application to solid-state radiation dosimetry

The effects of various experimental parameters have been investigated in order to optimize potential dosimetric applications of optically stimulated luminescence from LiF:Mg,Ti. These included: (i) the most appropriate filter in the emission channel for optimization of signal to noise ratio, (ii) the effect of sample thickness and self-absorption, (iii) the effects of high dose pre-irradiation for sensitization/radiation damage on the emission spectra and (iv) the effects of the preirradiation annealing/cooling procedures. Two methods have been used to measure the time-stability of the F3+ and F2 emission bands: (i) via the measurement of the OSL intensity (520 or 640nm band) as a function of the laser illumination time and (ii) via the measurement of the emission spectra in the range 500–700nm after 30min illumination by 300mW laser light (457nm). In addition the OSL dependence on the stimulation light intensity has also been investigated.

Analysis of OSL intensity increase with temperature and its consequences for dating applications

OSL dependence on temperature in the range from RT to 230 °C has been investigated in quartz separated from sediments in order to determinate the main OSL component responsible for the OSL intensity increase with temperature. The optical cross section spectra have been found and four OSL components have been recognized. The significant changes of the relative contributions of individual components in the total signal with temperature have been observed. The share of fast and medium components decreases with temperature. The characteristic behaviour of the intensities of these components, found also in the computer simulations of equivalent OSL process, indicates that both components can be related to one trap. The share of the slow component increases clearly above 150 °C. Because of the increase of the unstable super fast component above 80 °C, the temperature range below this temperature has been indicated as the most safe for OSL measurement in OSL dating.

Optimising the separation of quartz and feldspar optically stimulated luminescence using pulsed excitation

Abstract In luminescence dating, the two most commonly used natural minerals, quartz and feldspar, are exposed to different dose rates in the natural environment, and so record different doses. The luminescence signals also have different stabilities. For accurate dosimetry, the signals from these two minerals must be separated, either by physical separation of the mineral grains, or by instrumental separation of the luminescence signals. The luminescence signals from quartz and feldspar have different luminescence lifetimes under pulsed optical stimulation. This difference in lifetime can be used to discriminate between the two signals from a mixed quartz-feldspar sample. The purpose of this study is to identify optimum measurement conditions for the best separation of quartz OSL from that of feldspar in a mixed sample using pulsed stimulation and time-resolved OSL. We integrate the signal from 5 μs after the LEDs are switched off until just before the LEDs are switched on again, with the pulse on -time equal to the pulse off -time of 50 μs. By using only the initial interval of the pulsed OSL decay curve (equivalent to 0.2 s of CW-OSL using blue light at 50 mW cm −2 ) we find that the quartz to feldspar pulsed OSL intensity ratio is at a maximum. By using these parameters with an additional infrared (IR) stimulation at 175 °C before measurement (to further reduce the feldspar signal intensity), we obtain a factor of 25 enhancement in signal separation compared to that from a conventional prior-IR CW measurement. This ratio can be further improved if the counting window in the pulse off -time is restricted to detect between 20 and 50 μs instead of the entire off -period.