Thermoluminescent Materials Research Articles

The optically stimulated luminescence (OSL) properties of LiF:Mg,TI, Li2B4O7:CU, CaSO4:Tm, and CaF2:MN thermoluminescent (TL) materials

This paper reports on an investigation into the optically stimulated luminescence (OSL) properties of several known thermoluminescent materials, namely LiF:Mg,Ti, Li2B4O7:Cu, CaSO4:Tm, and CaF2:Mn. Samples were irradiated to air doses of 15mGy, 150mGy and 1.5Gy and analyzed using a commercially available OSL reader system to determine their luminescence response to continuous blue and infrared light (IR) excitation, centered at 470nm and 830nm wavelengths, respectively. CaF2:Mn did not show an OSL response with either IR or blue light stimulation. Li2B4O7:Cu and LiF:Mg,Ti demonstrated relatively weak OSL signals only under blue light excitation. CaSO4:Tm exhibited OSL under both IR and blue light stimulation at sensitivities roughly one order of magnitude less than the OSL response of α-Al2O3:C under the same conditions.

XPS and PIXE Analysis of Doped Silica Fibre for Radiation Dosimetry

The material characteristics of doped SiO2 fibre are studied, the electron traps in the product medium creating a situation attractive for their application in thermoluminescence (TL) radiation dosimetry. To date, rather limited research has been conducted towards gaining an essential understanding of the magnitude of TL signal and material characteristics of doped fibres. Characterization is being sought to ensure that the mechanism of TL yield in optical fibres is well understood, allowing a favourable well controlled production situation to be established. The intended end point is to specify dosimeters, not only for clinical dosimetry but also for their application in industrial/energy–industry settings. Investigation of the surface oxidation state of the Ge-doped SiO2 optical preform has been carried out using the X-ray photoelectron spectroscopy technique. In a further development using the fibre forming technology, particle-induced X-ray emission/Rutherford back scattering measurements have been employed to ascertain dopant concentrations of Ge-doped-cladding photonic crystal fibres (PCFs) with a view to improving TL yield. Present results concern uncollapsed and collapsed-hole-PCFs.

Effect of γ-radiation on thermoluminescence in rare earths doped NaMgSO4Cl material

The thermoluminescence (TL) characteristics, effect of γ-radiation on NaMgSO4Cl: X (X = Tb; Ce, Tb; Dy; Dy, Eu) and trapping parameters in TL material prepared by wet chemical synthesis (WCS) method are studied. The intensity of these phosphors is compared with TLD CaSO4: Dy phosphor. The phosphor has a simple TL glow curve structure. The phosphors NaMgSO4Cl: Tb (between the range of 257–284°C); NaMgSO4Cl: Dy (173°C) and NaMgSO4Cl: Dy, Eu (156°C) have a single prominent peak, whereas NaMgSO4Cl: Ce, Tb has two peaks located at 154°C and 233°C indicating single and double trapping sites, respectively. It is found that intensity tends to be increase with increased concentrations of the activators. The TL glow curves of the phosphors have been recorded and irradiated at a rate of 0.99 kGyh−1 for 5 Gy γ-rays dose. The paper also discusses the kinetic parameters evaluated by Chen's half width method such as activation energy E (eV) and frequency factor S (s−1).

Temperature Effect on the Thermoluminescent Signal Induced by Gamma Radiation in NaCl

ABSTRACTThe effects of thermal treatments on the thermoluminescent (TL) signal of NaCl (ACS reagent) induced by gamma radiation were investigated. Samples of NaCl were thermally treated at 500, 800 and 1000 °C and characterized by X-Ray diffraction and scanning electron microscopy. After their exposure 0.1 to 150 Gy of gamma radiation from a gamma-ray source of60Co, a TL curve for each temperature of treatment was obtained. We observed a different TL behavior on the irradiated samples as a function of the temperature applied during the thermal treatments. For the sample treated at 500 °C, three peaks centered at 102, 133 and 228 °C were observed. Samples treated at 800 and 1000 °C showed two main peaks at 128 and 220 °C and 136 and 219 °C, respectively; however, the highest TL intensity signal was observed for the sample at 800 °C. All samples showed a linear dependency of the integrated TL intensity from the signal emitted as function of the irradiation time. This is an important advantage because NaCl could be applied as a very low cost thermoluminescent dosimetric material. A comparison between the TL signal induced by gamma radiation in pure and Eu doped NaCl is also reported.

The deconvolution of thermoluminescence glow-curves using general expressions derived from the one trap-one recombination (OTOR) level model

The new developed thermoluminescence (TL) glow-peak expressions derived from the one trap-one recombination (OTOR) level model were used to analyze the TL glow-curves recorded with linear and exponential heating function profiles under various experimental conditions. The results showed that these expressions can, accurately, analyze the TL glow-curves even with the overlapped glow-peaks. Low values of R=An/Am were reported for glow-peaks in different TL materials. A glow-peak with the possibility of An>Am was also pointed out.

Thermoluminescence characteristics of Ge-doped optical fibers with different dimensions for radiation dosimetry

Important thermoluminescence (TL) properties of five (5) different core sizes Ge-doped optical fibers have been studied to develop new TL material with better response. These are drawn from same preform applying different speed and tension during drawing phase to produce Ge-doped optical fibers with five (5) different core sizes. The results of the investigations are also compared with most commonly used standard TLD-100 chips (LiF:Mg,Ti) and commercial multimode Ge-doped optical fiber (Yangtze Optical Fiber, China). Scanning Electron Microscope (SEM) and EDX analysis of the fibers are also performed to map Ge distribution across the deposited region. Standard Gamma radiation source in Secondary Standard Dosimetry Lab (SSDL) was used for irradiation covering dose range from 1Gy to 10Gy. The essential dosimetric parameters that have been studied are TL linearity, reproducibility and fading. Prior to irradiation all samples ∼0.5cm length are annealed at temperature of 400°C for 1h period to standardize their sensitivities and background. Standard TLD-100 chips are also annealed for 1h at 400°C and subsequently 2h at 100°C to yield the highest sensitivity. TL responses of these fibers show linearity over a wide gamma radiation dose that is an important property for radiation dosimetry. Among all fibers used in this study, 100μm core diameter fiber provides highest response that is 2.6 times than that of smallest core (20μm core) optical fiber. These fiber-samples demonstrate better response than commercial multi-mode optical fiber and also provide low degree of fading about 20% over a period of fifteen days for gamma radiation. Effective atomic number (Zeff) is found in the range (13.25–13.69) which is higher than soft tissue (7.5) however within the range of human-bone (11.6–13.8). All the fibers can also be re-used several times as a detector after annealing. TL properties of the Ge-doped optical fibers indicate promising applications in ionizing radiation dosimetry.

Assessment of Ge-doped optical fibres subjected to x-ray irradiation

We have reported the thermoluminescence (TL) response of five different diameters ~120, 241, 362, 483, and 604 μm of 6 mol percent Ge-doped optical fibres. The perfomance of the Ge-doped optical fibre are compared with commercially available TLD-100 chips (LiF:Mg,Ti) in terms of their sensitivity and minimum detectable dose (MDD). The irradiation was performed using X-ray machine (Model ISO 'Narrow Spectrum Series') provided by the Malaysian Nuclear Agency (MNA) at 60 kV X-ray irradiation in low doses ranging from 1-10 mGy. The results show the linear TL dose response from the fibres up to 10 mGy. The smallest diameter of 120 pm optical fibre shows the highest TL dose response compared to above mentioned fibres. The minimum detectable dose (MDD) is 0.82, 0.20, 0.14, 0.08, and 0.13 mGy for Ge-doped with diameters of 120, 241, 362, 483 and 604 μm. All TL materials show the MDD value within the delivered dose 0.01-1.00 mGy subjected to x-ray irradiation. The Ge-doped fibre with diameter of 483 pm was matched the MDD value of TLD-100 chips that equivalent to 0.08 mGy at the same irradiation. We have observed that among the five different diameters of optical fibre, 120 μm shows the best results and its better response than TLD-100 chips (by a factor of 5). The linear response at low dose levels makes this optical fibre most suitable for medical application.

Characterisation of the thermoluminescence (TL) properties of tailor-made Ge-doped silica glass fibre for applications in medical radiation therapy dosimetry

We have investigated the characterisation of new fabricated material Ge doped silica glass thermoluminescence TL dosimeter (Photonic Research Centre, University of Malaya) for medical radiation dosimetry at therapy energy. Previously, the dosimeter has been studied to provide ideal dosimetry system, suitable to ensure an accurate delivery of radiation doses to tumour tissue while minimising the amount of radiation administrated to healthy tissue. Both energies of photon and electron were used in this experiment for a dose range of 1 to 5 Gy. The various sizes of core diameter Ge doped silica glass (120, 241, 362, 483 and 604 μm) were exposed by using linear accelerator at Pantai Medical Centre. For both energies, the optical fibres were found to produce a flat response to a fixed photon and electron doses to within 4% (S.D) of the mean of the TL distribution. In terms of dose response, the fibres provide linear response over the range investigated, from a fraction of 1-5 Gy. The finding shows 120 μm fibres have 1.82 greater dose response than 604 pm fibres irradiated at 6 MV photon with a fixed dose of 3 Gy. While for electron energy 12 MeV, the response shows 120 μm fibres have 1.58 greater dose response compared to 604 μm fibres. The good responses are suitable to make these tailor-made doped silica fibres a promising TL material for use as a dosimetric system in medical radiation therapy.

Influence of Sintering Temperature on the Thermoluminescence Spectra of MgSO<sub>4</sub> Doped with RE(Tm,Dy) and Mn

In this paper, MgSO4:Dy,MgSO4:Tm and MgSO4:Mn phosphors are prepare by high temperature solid state reaction. The MgSO4:Dy or MgSO4:Tm powder are mixed and sintered with MgSO4:Mn respectively to obtain the co-doped MgSO4:Dy,Mn and MgSO4:Tm,Mn phosphors. The 3-dimensional thermoluminescence spectra of these two phosphors under different sintering temperature are measured.Results show that when the sintering temperature is below 800°C, Dy, Tm and Mn ions emissions are independent. However, when the sintering temperature was over 800°C, the emission peak of Mn becomes weaker, and so do the low temperature peaks of Dy and Tm, while the high temperature peaks of Dy and Tm become stronger. This indicated that the defect complex structure in the formation of the thermoluminescence material depends on the sintering temperature. As the sintering temperature rises, more and more Mn ions combine with the rare earth ions. Therefore, the luminescence process of the energy transfer of Mn ions to the rare earth ions can be observed and the suppression to low temperature peaks of Tm and Dy, and also shown in spectra.

TLD Instrumentation: A Case Study of PC Controlled TL Reader

Thermoluminescence reader is an important tool and a requisite for a researcher to study and characterize Thermoluminescence (TL) materials in different forms. Requirement for a versatile PC Controlled TL Reader has been felt for quite some time globally. Nucleonix Systems, Hyderabad, India, have developed a PC Controlled TL Reader by integrating complete electronics hardware circuits (comprising of Power Electronics, Low/High voltage Supplies, Temperature Controller, Micro Controller based data acquisition circuits having serial counter, ADC, DAC, EEPROM, PMT, PMT housing, sample heating system, drawer assembly, etc.) in a single enclosure. The system also integrated with software to calculate the activation energy (E), frequency factor (S) and order of kinetics ‘1’ for the prominent glow peaks using different equations.This Integral TL Reader unit gets connected to the Personal Computer System through serial port RS232C/USB port. The user interface to the system is through front–end VB software defined Graphics User Interface (GUI). The system also contains some of the software features like glow curve acquisition, analysis, filing, printing, plotting, overlapping, maker data reporting, etc. Additionally, system facilitates single/two/three plateau heating with variable heating rates.The primary objective of this development is to bring out versatile TL instrumentation system and also to make it affordable to many of the researchers in the Universities and other areas, including Radio-therapist, Medical Physicists in Cancer Hospitals. This system has been evaluated for its performance with CaSO4: Dy discs, powder, as well as with LiF: Mg, Ti chips. Linearity and reproducibility have been found to be quite satisfactory also within +2%. This system is quite useful to study the TL of phosphor, minerals and characterization of various solid semiconducting materials, and also can be used in personal dosimetry measurements and research studies in medical dosimetry, environmental radiation monitoring, and host of other applications in R&D Labs., etc.

Further studies on the role of dopants in LiF:Mg,Cu,Si thermoluminescent material.

The 3-D thermoluminescence spectra and glow curves of LiF:Mg,Cu,Si, LiF:Mg,Cu, LiF:Mg,Si and LiF:Cu,Si with low concentrations of Mg and Cu were measured and were compared with those with high concentrations to investigate further the role of dopants in LiF:Mg,Cu,Si material. The shape of glow curves of the four samples is similar; however, LiF:Cu,Si sample had no Mg dopant. It is concluded that the TL emission to be from self-trapped excitons in LiF, and this emission could be enhanced and altered by Mg, Cu and Si dopants in LiF:Mg,Cu,Si; all three dopants are necessary to obtain the bright TL emission and may be involved in the luminescence process; Mg seems to be the most essential dopant and Cu is involved in the trapping although the role of Mg dominates; both Cu and Si play a role in the main emission process and Cu also plays a role in reducing the emission around 610 nm.

Synthesis and thermoluminescence characterization of Na6Mg(SO4)4:RE (RE = Ce, Tb) phosphors

Thermoluminescence (TL) properties of sulfate-based phosphors activated by different rare earths have received tremendous attention to the field of radiation dosimetry. Those TL materials based on CaSO4 have been widely applied for medical and environmental dosimetry. Taking this fact into account we have synthesized Na6Mg(SO4)4 doped with Ce and Tb by wet chemical method. The prepared phosphor was characterized by XRD, FTIR, photoluminescence (PL) and thermoluminescence. For TL study, the phosphor is irradiated with γ-rays from 60Co source. For studying luminescence properties, the prepared phosphor was annealed at different temperatures and effects of these annealing temperatures on Na6Mg(SO4)4 samples are investigated and quantified. The changes in the glow curve and PL emission spectrum are also investigated as a function of annealing temperature and the annealing temperature was optimized. For calculation of trapping parameters various methods such as peak shape (PS) method, initial rise (IR) method, various heating rate (VHR) method, and computerized glow curve deconvolution (CGCD) are employed.

Intercomparison of Gafchromic™ films, TL detectors and TL foils for the measurements of skin dose in interventional radiology

Several passive solid state dosemeters, such as Gafchromic™ films and thermoluminescence (TL) detectors, are used to estimate and monitor patient skin doses in interventional radiology. To determine the suitability of XR-TypeR Gafchromic™ films and of detectors based on TL materials: pellets, chips and foils to measure skin dose, an intercomparison exercise has been organized within European Dosimetry Radiation Group – Working Group 12 “European Medical ALARA Network” (EURADOS WG12). To test response detectors were exposed to X-ray beams of energies and qualities applied clinically. A blind test was also performed to investigate the accuracy of the dose estimate by detectors exposed to unknown doses. We found the response of films to be strongly dependent on beam quality and filtration (increasing by up to 80% with respect to reference beam quality). The response of TL detectors was found to be less dependent on beam quality (less than 25% variation), with TL foils showing less than 10% variation with respect to reference beam quality. To accurately estimate patient skin doses in interventional radiology it is important to choose the quality of the calibration beam to be as close as possible to the quality of beams actually applied in clinical work.

Evaluation of trapping parameters of γ-rays irradiated Dy3+ -doped LaPO4 phosphors.

Thermoluminescence (TL) materials are widely used in radiation measurements. The best-known applications of TL materials are in the dosimetry of ionizing radiation, and in CTV screen phosphors, scintillators, X-ray laser materials, etc. The TL glow curve and its kinetic parameters for annealed LaPO4 at different constant temperatures and for Dy(3+) -doped LaPO4 phosphors irradiated by gamma-rays are reported here. The samples were irradiated using a (60) Co gamma-ray source at a dose of 10 Gy and the heating rate used for TL measurements was 5 ºC/s. The samples were characterized using X-ray diffraction (XRD), Fourier transform infrared, transmission electron microscopy and TL techniques. The XRD pattern shows that the prepared phosphor has a good crystalline structure with an average crystallite size of ~ 18 nm. The samples show good TL peaks for 0.05, 0.1 and 0.2 mole % doping concentrations of Dy(3+) ions and anneal above 400 ºC. The TL glow curve characteristics of annealed LaPO4 and Dy(3+) -doped LaPO4 were analyzed and trapping parameters calculated using various methods. All TL glow curves obey the second-order kinetics with a single glow peak, which reveals that only one set of trapping parameter is set for a particular temperature. The TL sensitivity was found to depend upon the annealing temperature and Dy(3+) doping concentration. The prepared sample may be a new nano phosphor and be useful in TL dosimetry.

Thermoluminescence properties of Yb–Tb-doped SiO2 optical fiber subject to 6 and 10 MV photon irradiation

This paper reports thermoluminescence characteristics of thermoluminescence dosimetry 100 chips and Yb–Tb-doped optical fibers irradiated with 6 and 10 MV photons. Thermoluminescence response of both dosimeters increases over a wide photon dose range from 0.5 to 4 Gy. Yb–Tb-doped optical fibers demonstrate useful thermoluminescence properties and represent a good candidate for thermoluminescence dosimetry application with ionizing radiation. The results of this fiber have been compared with those of commercially available standard thermoluminescence dosimetry-100 media. Commercially available Yb–Tb-doped optical fibers and said standard media are found to yield a linear relationship between dose- and thermoluminescence signal, although Yb–Tb-doped optical fibers provide only 10 % of the sensitivity of thermoluminescence dosimetry-100. With better thermoluminescence characteristics such as small size (125 μm diameter), high flexibility, easy of handling and low cost, as compared to other thermoluminescence materials, indicate that commercial Yb–Tb-doped optical fiber is a promising thermoluminescence material for variety of applications.

Photon attenuation coefficients of thermoluminescent dosimetric materials by Geant4 toolkit, XCOM program and experimental data: A comparison study

The mass attenuation coefficients, μ/ρ of some thermoluminescent dosimetric materials with potential applications as personnel dosimeters, have been investigated using Geant4 simulation toolkit. Appreciable variations are noted for the μ/ρ values by changing the photon energy and chemical compositions. The Geant4 toolkit simulation results of μ/ρ are compared with experimental data wherever possible. Comparisons are also made with predictions from the XCOM program in the energy region from 1keV to 100GeV. Good agreement among Geant4 toolkit simulation, XCOM program and experimental data indicate that the Geant4 toolkit may be employed to make calculations on the μ/ρ values of various dosimetric materials. The results indicate that this process can be followed to determine the interaction of photon with the several energies in different materials.

The Thermoluminescence Response of Dy Doped Calcium Borate Glass Subjected to 6MV Photon Irradiation

This paper presents the thermoluminescence (TL) response and sensitivity of various dopant concentration of Dy into borate glass. Borates glass present absorption coefficient that closely to human bone and teeth. This fact makes borate as an ideal material for TL material either for medical or environmental dosimeter. Therefore, a series of glasses based on xCaO-(100-x)B2O3system (0 x 100) % weight has been prepared by using melt quenching method. In this research, Dy doped (0.01-0.4) mol% to 30CaO-70B2O3glass sample were studied to investigate the TL properties in terms of dose-response relationship and sensitivity. Samples were irradiated to various doses range 0.5-4.0 Gy subjected to 6 MV photon irradiation by using LINAC Primus MLC 3339. The TL intensity of various dopant concentration were studied and it was founds that the 0.3 mol% Dy has the highest TL response and has linear dose response relationship. The highest sensitivity was calculated as 58 nC.mg-1.Gy-1for 0.3 mol% Dy concentration.

Thermoluminescence of Y2O3:Tb3+ thin films deposited by electron beam evaporation

Most thermoluminescent materials are created using crystal growth techniques; however, it would be of great utility to identify those few thermoluminescent materials that can be deposited using simpler methods, for example to be compatible with the early portions of a silicon integrated circuit or microelectromechanical fabrication process. In this work, thin films of yttrium oxide with a terbium impurity (Y2O3:Tb) were deposited on silicon wafers by electron beam evaporation. The source for the Y2O3:Tb was made by combining Y2O3 and Tb4O7 powders. The approximate thicknesses of the deposited films were 350nm. After deposition, the films were annealed at 1100°C for 30s to improve crystallinity. There is a strong correlation between the x-ray diffraction (XRD) peak intensity and the thermoluminescent glow curve intensity. The glow curve displays at least two peaks at 140°C and 230°C. The emission spectra was measured using successive runs with a monochromator set to a different wavelength for each run. There are two main emission peaks at 490nm and 540nm. The terbium impurity concentration of approximately 1mol% was measured using Rutherford backscattering spectrometry (RBS). The Y2O3:Tb is sensitive to UV, x-ray, and gamma radiation. The luminescent intensity per unit mass of UV irradiated Y2O3:Tb was about 2 times that of x-ray irradiated TLD-100.

Passive temperature sensing using thermoluminescence: Laboratory tests using Li2B4O7:Cu,Ag, MgB4O7:Dy,Li and CaSO4:Ce,Tb

The objective of this work is to test three thermoluminescent (TL) materials, Li2B4O7:Cu,Ag (LBO), MgB4O7:Dy,Li (MBO) and CaSO4:Ce,Tb (CSO), as passive temperature sensors. Particles of these materials were subjected to two heating profiles: (a) a slow heating profile (2h inside a muffle furnace) or (b) a fast heating profile (dropping them through a temperature chamber for ~1s). The TL curves from these heated particles were recorded and compared to the TL from control samples, which were not exposed to the temperature profile. A simple TL model (first order TL peaks with a distribution of activation energies and single frequency factor) was applied to determine the temperature experienced by the particles based on their TL curves. The temperatures indicated by the TL particles were comparable to the temperatures measured using thermocouples, with some exceptions. These exceptions include situations in which the material was not suitable for a specific temperature range (e.g., CSO heated below 200°C for 2h duration) or in which particle aggregation prevented the aliquots from being uniformly heated (e.g. LBO heated in the temperature chamber).

Thermoluminescent properties of lithium borate, magnesium borate and calcium sulfate developed for temperature sensing

The objective of this work is to characterize three thermoluminescent (TL) materials synthesized in our laboratory and identified as having properties suitable for temperature sensing, including bright TL emission, low fading at room temperature and low light-induced fading (bleaching) of the TL signal. They are lithium borate doped with copper and silver, Li2B4O7:Cu,Ag (LBO), magnesium borate doped with dysprosium and lithium, MgB4O7:Dy,Li (MBO), and calcium sulfate doped with cerium and terbium, CaSO4:Ce,Tb (CSO). We present their synthesis, powder X-ray diffractograms, TL emission spectra, dose response, and sensitivity to ionizing radiation (compared to commercial LiF:Mg,Ti TL material). Important characteristics for temperature sensing applications, such as fading and bleaching, are presented and discussed. LBO and MBO presented in this work have TL emissions in separate regions of the spectrum, meaning that they can be used simultaneously for temperature measurements, their TL signal being separated in the laboratory using appropriate optical filters. The data presented in this paper provides the supporting basic information required to use these materials in temperature sensing experiments.