Thermoluminescence of LiF:Mg,Ti (TLD 100) Subject to 1.25 Mega Electron Volt Gamma Radiotherapy (original) (raw)
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Radiation damage and sensitization effects on thermoluminescence of LiF:Mg,Ti (TLD-700)
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2017
The radiation damage effects and enhancement the thermoluminescence (TL) efficiency of LiF:Mg,Ti (TLD-700)dosimeters via sensitization method were discussed. Attempts to eliminate the effects of damage and sensitization were made using different types of annealing processes. The results showed that after irradiating the dosimeters with dose > 250 Gy of 60 Co gamma source, damage effects were observed. The sensitivity of the total area under the curve was decreased by a factor of 0.5afterirradiationatapre−testdoseof2kGy.However,theeffectsofradiationdamageoneachglow−peakaredifferent.Theglow−peak2wastheonlypeakthatwasnotaffectedbythehigh−doseirradiation.Ithasbeenshownthatthedegreeoftheradiationdamageeffectisrelatedtothemaximumdose−responsefunction,fðDÞmaxoftheglow−peak.Ingeneral,significantradiationdamageeffectswereobservedfortheglow−peaksofhighfðDÞmax.Post−irradiationannealat280°Cfor30mincausesdramaticeffectsontheshapeoftheglowcurveandaswellasonthesensitivityofthedosimeters.Anincreasingbyafactorof0.5 after irradiation at a pre-test dose of 2 kGy. However, the effects of radiation damage on each glow-peak are different. The glow-peak 2 was the only peak that was not affected by the high-dose irradiation. It has been shown that the degree of the radiation damage effect is related to the maximum dose-response function, f ðDÞ max of the glow-peak. In general, significant radiation damage effects were observed for the glow-peaks of high f ðDÞ max. Post-irradiation anneal at 280°C for 30 min causes dramatic effects on the shape of the glowcurve and as well as on the sensitivity of the dosimeters. An increasing by a factor of 0.5afterirradiationatapre−testdoseof2kGy.However,theeffectsofradiationdamageoneachglow−peakaredifferent.Theglow−peak2wastheonlypeakthatwasnotaffectedbythehigh−doseirradiation.Ithasbeenshownthatthedegreeoftheradiationdamageeffectisrelatedtothemaximumdose−responsefunction,fðDÞmaxoftheglow−peak.Ingeneral,significantradiationdamageeffectswereobservedfortheglow−peaksofhighfðDÞmax.Post−irradiationannealat280°Cfor30mincausesdramaticeffectsontheshapeoftheglowcurveandaswellasonthesensitivityofthedosimeters.Anincreasingbyafactorof35 in the sensitivity of the total area under the curve was observed at a pre-test dose of 2 kGy. Improving the sensitivity of peak 7 by a factor of$22 was the dominant factor in increasing the sensitivity of the dosimeters. On the other hand, an increasing by factors of 2.5and2.5 and 2.5and4 was found for peaks 2 and 5 respectively. On the other hand, a decreasing by a factor $0.5 was observed for peaks 3 and 4. At pre-test dose levels >250 Gy, a very strange and high intensity tail was observed in the high-temperature region of the glow-curves. The readout anneal was not enough to remove this tail. While, the furnace anneal could eliminate the sensitization effects but not the radiation damage effects on the sensitivity of the dosimeters.
Radiation Measurements, 2010
The high temperature thermoluminescence (HTTL) in the glow curve of LiF:Mg,Ti (TLD-100) is of continuing interest due to the dependence of the HTTL on ionization density. Following high ionization density irradiation, the intensity of the HTTL relative to peak 5 is much greater than the same ratio following low ionization density irradiation. Special attention has focused on the details of the linearity/supralinearity of the HTTL dose response at levels of dose between 10 and 500 mGy and whether the batch history (previous irradiation and annealing) affects the HTTL dose response? In this paper we demonstrate that batch identity leads to differences of w100% in the degree of the supralinearity of the dose response of peak 7 between two groups of TLD-100 chips. The results suggest that there may be significant non-universalities in the HTTL dose response and that further research is required to provide a sound basis for the use of the HTTL of TLD-100 in dosimetric applications.
1995
The dose response of the TL emission spectra of an LiF: Mg,Ti (TLD-100) sample and three LiF:Mg,Ti samples with different impurity concentrations (0~5 ppm Ti and 80-100 ppm Mg) have been measured. At a dose less than 22 Gy the emission spectrum of the TLD-100 sample comprises one emission band at 420 nm. The sample without Ti shows also one emission band but now at 620 nm. The spectra of the other two samples comprises two emission bands at 420 nm and 620 nm of which the intensity of the 420 nm band increases with increasing Ti concentration. The dose response of the glow peaks is different for peaks at different temperatures and emission bands. From these observations it can be concluded that in LiF: Mg,Ti at least some of the traps and luminescent centers are coupled.
RAP 2019 Conference Proceedings
Thermoluminescence dosimeters have been an important tool for measuring the ionizing radiation dose in the field of personal, clinical, environmental and space applications. In this study, thermoluminescence glow curves of newly synthesized Mg,Cu,P doped LiF (TLD-100H) were recorded using four different filters in order to investigate the effect of different filter packs on TL glow peaks. It was observed that the TLD-100H dosimeter has four TL glow peaks at 100 o C, 150 o C, 200 o C and 260 o C for the heating rate value of 1 °C/s. Additionaly, the minimum detectable dose of the TLD-100H dosimeter for a TL peak of 260 o C has been determined using the thermoluminescence method as a preliminary work.
Some dosimetric characteristics of the high temperature TL in LiF:Mg,Ti (TLD-100)
Radiation Measurements, 2008
Various characteristics of the high temperature TL (HTTL) in the glow curve of LiF:Mg,Ti (TLD-100) are reviewed. Special emphasis is placed on the question of the linearity/supralinearity of the HTTL dose response at low dose levels from 2.5 to 250 mGy. It appears that a mild HTTL supralinearity of approximately 15-50% for each dose decade may be present between 5 and 250 mGy followed by an abrupt and rapid increase in the supralinearity above 250 mGy. However, difficulty in the estimation of background and the great variability in the protocols of measurement does not allow a definitive conclusion.
Radiation Measurements, 2008
Recent development of LiF:Mg,Cu,Si exhibiting high TL sensitivity (55 times that of TLD-100 LiF:Mg,Ti) and insignificant higher temperature peak leading to negligible residual TL signal has provided a TLD for pragmatic replacement of both LiF:Mg,Ti and LiF:Mg,Cu,P in personal dosimetry. LiF:Mg,Cu,Si withstood readout temperature up to 300 • C. For the reader annealing using a maximum readout temperature and clamping at 260 • C, no significant change in the TL sensitivity and glow curve structure was observed for more than 100 reuse cycles of exposures (5.5 mGy) and readout. TL emission spectrum LiF:Mg,Cu,Si was found to have three emission bands peaking at 355, 385 and 440 nm similar to that of LiF:Mg,Cu,P but differing in the relative intensities. Negligible fading, insensitivity to room light and absence of the effect of pre-or post-storage annealing on the response and the glow curve structure makes it a strong contender to be opted for personal dosimetry applications.
Radiation Measurements, 2001
The dose-response of sintered MTS-N (LiF : Mg; Ti) thermoluminescent detectors in which the concentration of Mg was varied between 30 and 920 ppm and the Ti concentration varied between 13 and 260 ppm, has been studied after Cs-137 gamma-ray and fast proton irradiation (average energy 147 MeV) in the dose range between 0.5 and 37:5 Gy. Peak 4 and peak 5 were extracted from the TL glow curve by deconvolution, assuming ÿrst-order kinetics. We have observed a decrease in the supralinear response of LiF : Mg; Ti at increasing Mg concentration. The e ect of varying the concentration of Ti on the dose response was less pronounced. No signiÿcant di erence in the linearity index measured after Cs-137 gamma-ray and fast proton beam irradiation was observed at all the studied Mg and Ti concentration values. The data are discussed with reference to some models of TL supralinearity. The extended range of linearity of the high Mg-doped LiF : Mg; Ti materials may make them better suited for clinical dosimetry.
Physica Status Solidi (a), 1993
Optical absorption (OA) and thermoluminescence (TL) studies are carried out in LiF : Mg,Ti(TLD-100) single crystals as a function of irradiation temperature (Trr) from 77 to 523 K. While the variation in 310 nm OA and peak 5 (2498 K) TL with Trr from 77 to 385 K is within 1 7 % , the portion of 350 nm OA corresponding to peak 7 (z 573 K) and peak 7 TL increases drastically with qrr from 77 to 435 K. The latter result confirms that the OA of peak 7 centres occurs at 250nm and that the radiolysis process is involved in the creation of these defect centres. Due to thermal fading, the peak 7 TL and the above 250 nm OA decrease proportionally beyond Trr = 435 K confirming further the above correlation. A major outcome of this study is that two different defect centres-(i) centres giving rise to peak 7 and (ii) isolated F centres not related to any of the TL peaks above room temperaturegive rise to OA at the same or two positions close to 250 nm.
Behaviour of LiF:Mg,Cu,P and LiF:Mg,Ti thermoluminescent detectors for electron doses up to 1MGy
Radiation Measurements, 2010
The behaviour of LiF:Mg,Cu,P and LiF:Mg,Ti detectors at ultra-high doses up to 1 MGy, has been investigated. The presence of the ultra-high-temperature peak (450 C) of reproducible properties was observed in various batches of LiF:Mg,Cu,P, confirming earlier findings. The results indicate that this peak is not an effect of random impurities nor intrinsic effects of LiF, but it is rather connected with the doping. A parameter called ultra-high temperature ratio (UHTR) was defined in order to quantify the observed changes of LiF:Mg,Cu,P glow-curve shape at very high doses and very high temperatures. The use of this parameter allows to determine an absorbed dose in the range from 1 kGy to 1 MGy. This new method of high-dose dosimetry makes LiF:Mg,Cu,P a unique dosimeter, which is capable to cover at least 12 orders of magnitude of dose range: from a microgray to a megagray.
Radiation Protection Dosimetry, 2008
The dependence of the shape of the glow curve of LiF:Mg,Ti (TLD-100) on ionisation density was investigated using irradiation with 90 Sr/ 90 Y beta rays, 60 and 250 kVp X rays, various heavy-charged particles and 0.2 and 14 MeV neutrons. Special attention is focused on the properties of high-temperature thermoluminescence; specifically, the behaviour of the hightemperature ratio (HTR) of Peaks 7 and 8 as a function of batch and annealing protocol. The correlation of Peaks 7 and 8 with average linear-energy-transfer (LET) is also investigated. The HTR of Peak 7 is found to be independent of LET for values of LET approximately >30 keV mm 21. The behaviour of the HTR of Peak 8 with LET is observed to be erratic, which suggests that applications using the HTR should separate the contributions of Peaks 7 and 8 using computerised glow curve deconvolution. The behaviour of the HTR following neutron irradiation is complex and not fully understood. The shape of composite Peak 5 is observed to be broader following high ionisation alpha particle irradiation, suggesting that the combined use of the HTR and the shape of Peak 5 could lead to improved ionisation density discrimination for particles of high LET.