Browsing by Author "Lam, S.E."

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Carbon Rich Media for Luminescence-Based Surface Dosimetry and Study of Associated Surface Defects
(Elsevier, 2023-09-15) Lam, S.E.; Bradley, D.A.; Nawi, S.N. Mat; Khandaker, M.U.; Sani, S.F. Abdul
The present study continues research into the utilisation of carbonaceous media for medical radiation dosimetry, focusing on the effects of surface area-to-volume ratio and carbon content on structural interaction alterations and dosimetric properties in sheet- and bead-type graphitic materials (with the respective carbon content of ∼98 wt% and ∼90 wt%). Using 60Co gamma-rays and doses from 0.5 Gy to 20 Gy, the study has been made of the response of commercially available graphite in the form of 0.1 mm, 0.2 mm, 0.3 mm and 0.5 mm thick sheets, also of activated carbon beads. Confocal Raman and photoluminescence spectroscopy have been employed, examining radiation-induced structural interaction alterations. Dose-dependent variation in the Raman intensity ratio ID/IG relates to the varying dominance of defect generation and dose-driven defect annealing. Of the various thickness graphite sheets, the 0.1 mm thick medium possesses the greatest surface area-to-volume ratio. Perhaps unsurprisingly, it also exhibits the greatest thermoluminescence (TL) yield compared to that of the other carbonaceous sheet foils used herein. Moreover, the second greatest mass-normalised TL yield has been observed to be that of the porous beads, reflected in the greater defect density (ID/IG > 2) when compared to the other media, due in part to their inherent feature of large internal surface area. Considering the challenge posed in matching skin thickness with skin dose, the near tissue equivalent graphite sheets show particular promise as a skin dosimeter, sensitive as a function of depth.
Corrigendum to “investigation of Structural and Tl Kinetic Parameters of Smartphone Screen Protector Glasses for Applications in Retrospective Dosimetry”
(Elsevier, 2024-09-02) Muslima, Umme; Khandaker, Mayeen Uddin; Nawi, S.N. Mat; Lam, S.E.; Sani, S.F. Abdul; Bradley, D.A.; Saidur, R.; Tan, Y.S.; Osman, Hamid; Hanfi, Mohamed Y.; Issa, Shams A.M.
Exploring the thermoluminescence characteristics of smartphone screen safety glasses for retrospective dosimetry applications
(2024-10-24) Muslima, Umme; Khandaker, Mayeen Uddin; Lam, S.E.; Nawi, S.N. Mat; Abdul Sani, S.F.; Ung, N.M.; Osman, Hamid; Y. Hanfi, Mohamed; Sayyed, M.I.; Alzimami, Khalid; Alqahtani, Amal; Bradley, D.A.
In clinical settings, standard dosimeters might miss radiation mishaps. Retrospective dosimeters could help to track personnel (such as patients and other staff who don't wear dosimeters) exceeding safe limits and assess long-term exposure trends. This study has investigated key thermoluminescence (TL) dosimetric characteristics, including the glow curve structure, dose-response, energy dependence, sensitivity and fading of various safety glasses that are used as screen protectors of smartphones subjected to photon irradiation. Among the studied glasses, the HD Anti-Peep safety glass for iPhone has been found to exhibit a linear dose-response with a regression coefficient of 99% within the dose range of 2–10 Gy. Moreover, all the safety glasses showed independence with respect to photon energy of 6 MV and 10 MV. The TL glow curves of the samples showed a broad glow peak between 125 °C and 325 °C at 10 Gy. The TL kinetic parameters of the safety glasses were also studied by analyzing the glow curves using the peak shape and initial rise method. The geometric factor (μg) is found to be within the range of 0.43–0.53, which indicates the suitability of applying Chen's general-order formula to calculate the kinetic parameters such as activation energy, frequency factor and trap lifetime. The activation energy (E) and frequency factor (s) are found in the range of 0.31–0.54 eV and 4.55 × 103 to 2.12 × 106 s−1 respectively obtained via the peak shape method. The relatively long trap lifetime and observed thermoluminescence features indicate that the HD Anti-Peep safety glass offers a better option to estimate dose retrospectively to ensure the safety of human health.
Exploring the Thermoluminescence Characteristics of Smartphone Screen Safety Glasses for Retrospective Dosimetry Applications
(Elsevier, 2024-10-15) Muslima, Umme; Khandaker, Mayeen Uddin; Lam, S.E.; Mat Nawi, S.N.; Sani, S.F. Abdul; Ung, N.M.; Osman, Hamid; Hanfi, Mohamed Y.; Sayyed, M.I.; Alzimami, Khalid; Alqahtani, Amal; Bradley, D.A.
In clinical settings, standard dosimeters might miss radiation mishaps. Retrospective dosimeters could help to track personnel (such as patients and other staff who don't wear dosimeters) exceeding safe limits and assess long-term exposure trends. This study has investigated key thermoluminescence (TL) dosimetric characteristics, including the glow curve structure, dose-response, energy dependence, sensitivity and fading of various safety glasses that are used as screen protectors of smartphones subjected to photon irradiation. Among the studied glasses, the HD Anti-Peep safety glass for iPhone has been found to exhibit a linear dose-response with a regression coefficient of 99% within the dose range of 2–10 Gy. Moreover, all the safety glasses showed independence with respect to photon energy of 6 MV and 10 MV. The TL glow curves of the samples showed a broad glow peak between 125 °C and 325 °C at 10 Gy. The TL kinetic parameters of the safety glasses were also studied by analyzing the glow curves using the peak shape and initial rise method. The geometric factor (μg) is found to be within the range of 0.43–0.53, which indicates the suitability of applying Chen's general-order formula to calculate the kinetic parameters such as activation energy, frequency factor and trap lifetime. The activation energy (E) and frequency factor (s) are found in the range of 0.31–0.54 eV and 4.55 × 103 to 2.12 × 106 s−1 respectively obtained via the peak shape method. The relatively long trap lifetime and observed thermoluminescence features indicate that the HD Anti-Peep safety glass offers a better option to estimate dose retrospectively to ensure the safety of human health.
Exploring the Viability of Desiccant Silica Gel Beads as a Novel Material for Radiation Dosimetry: A Preliminary Investigation
(Elsevier, 2024-12-15) Nawi, S.N. Mat; Khandaker, Mayeen Uddin; Sani, S.F. Abdul; Lam, S.E.; Mahmoud, Mustafa; Ung, N.M.; Bradley, D.A.
Silica gel bead material, with its porous structure, high surface area, uniform particle size, stability, and excellent adsorption capacity, is a key material for advancing dosimeter technologies. These qualities make it ideal for accurately measuring and monitoring ionizing radiation in various environments. The research aims to characterize the response of different ionizing radiation sources on desiccant silica gel beads, laying the groundwork for potential applications in medical dosimetry. In this study, silica gel bead samples were subjected to various radiation sources, including gamma rays with an average energy of 1.25 MeV, photons (6 MV), and electrons (6 MeV). The radiation was administered at doses within the range of 2 Gy–20 Gy, which is commonly used in radiotherapy to evaluate the dosimetric behaviour of the desiccant silica gel bead samples using the conventional thermoluminescence (TL) technique. The silica gel bead samples have been found to provide a highly linear dose response within the dose range of interest, with the coefficient of determination (R2) ranging between 0.91 and 0.96. Additionally, the samples show high sensitivity at lower doses and maintain excellent reproducibility, with a standard deviation of less than 4%. In regard to fading evaluation, desiccant silica gel beads exhibit minimal signal loss within 35 days post-irradiation, averaging between 20% and 38%. The findings of this study are promising for developing a new dosimeter, which will enhance radiation monitoring and measurement practices in various environments. These improvements cover dosimetric applications in medical and industrial fields including food safety and agricultural development.
Exploring the viability of desiccant silica gel beads as A novel material for radiation dosimetry: A preliminary investigation.
(2024-12-24) Nawi, S.N. Mat; Khandaker, Mayeen Uddin; Abdul Sani, S.F.; Lam, S.E.; Mahmoud, Mustafa; Ung, N.M.; Bradley, D.A.
Silica gel bead material, with its porous structure, high surface area, uniform particle size, stability, and excellent adsorption capacity, is a key material for advancing dosimeter technologies. These qualities make it ideal for accurately measuring and monitoring ionizing radiation in various environments. The research aims to characterize the response of different ionizing radiation sources on desiccant silica gel beads, laying the groundwork for potential applications in medical dosimetry. In this study, silica gel bead samples were subjected to various radiation sources, including gamma rays with an average energy of 1.25 MeV, photons (6 MV), and electrons (6 MeV). The radiation was administered at doses within the range of 2 Gy–20 Gy, which is commonly used in radiotherapy to evaluate the dosimetric behaviour of the desiccant silica gel bead samples using the conventional thermoluminescence (TL) technique. The silica gel bead samples have been found to provide a highly linear dose response within the dose range of interest, with the coefficient of determination (R2) ranging between 0.91 and 0.96. Additionally, the samples show high sensitivity at lower doses and maintain excellent reproducibility, with a standard deviation of less than 4%. In regard to fading evaluation, desiccant silica gel beads exhibit minimal signal loss within 35 days post-irradiation, averaging between 20% and 38%. The findings of this study are promising for developing a new dosimeter, which will enhance radiation monitoring and measurement practices in various environments. These improvements cover dosimetric applications in medical and industrial fields including food safety and agricultural development.
h-BN layered material: A new frontier in radiation dosimetry
(2024-10-24) Khandaker, Mayeen Uddin; Mat Nawi, S.N.; Mohd Lazim, M.A.F.; Abdul Sani, S.F.; Ung d, N.M.; Lam, S.E.; Ahmad, Pervaiz; Mahmoud, Mustafa; Bradley, D.A.
This study explores the potential of hexagonal boron nitride (h-BN) nanostructures for dosimetry of diverse ionizing radiation. We focus on the crucial thermoluminescence (TL) properties of h-BN, including glow curve, dose-response, reproducibility, sensitivity, and fading, within the conventional framework of TL dosimetry. The h-BN powder samples were exposed to different ionizing radiations, including 60Co gamma-rays with a mean energy of 1.25 MeV, electrons (6 MeV), and photons (6 MV), at levels of dose familiar in radiotherapy ranging from 2 Gy to 15 Gy. The h-BN's effective atomic number of 6.25, similar to human tissue, opens up exciting possibilities for applications in medical imaging and dosimetry. Notably, h-BN demonstrates a linear response within the dose range of interest, showcasing excellent sensitivity, particularly at low doses and low photon energies. Additionally, h-BN samples exhibit remarkable reproducibility, with a standard deviation of less than 2.4%, albeit accompanied by significant fading. Regarding the trapping parameters underpinning the manifestation of the glow curves of the irradiated samples, use was made of the peak shape method with different models to estimate the order of kinetics (b), activation energy (E), and frequency factor (s) or escape probability and trap lifetime (τ). The data suggest that the TL glow peaks of the h-BN obey general-order kinetics. These findings underscore the transformative potential of h-BN layered material in advancing radiation dosimetry, particularly in medical physics fields. The inherent characteristics of h-BN, coupled with its effective atomic number, excellent linearity over a wide range of radiation doses especially for electron irradiation and better reproducibility, positioned it as a suitable tool for precise and reliable dose measurement in medical imaging and therapy, heralding a new frontier in radiation dosimetry.
H-BN Layered Material: A New Frontier in Radiation Dosimetry
(Elsevier, 2024-10-20) Khandaker, Mayeen Uddin; Nawi, S.N. Mat; Lazim, M.A.F. Mohd; Sani, S.F. Abdul; Ung, N.M.; Lam, S.E.; Ahmad, Pervaiz; Mahmoud, Mustafa; Bradley, D.A.
This study explores the potential of hexagonal boron nitride (h-BN) nanostructures for dosimetry of diverse ionizing radiation. We focus on the crucial thermoluminescence (TL) properties of h-BN, including glow curve, dose-response, reproducibility, sensitivity, and fading, within the conventional framework of TL dosimetry. The h-BN powder samples were exposed to different ionizing radiations, including 60Co gamma-rays with a mean energy of 1.25 MeV, electrons (6 MeV), and photons (6 MV), at levels of dose familiar in radiotherapy ranging from 2 Gy to 15 Gy. The h-BN's effective atomic number of 6.25, similar to human tissue, opens up exciting possibilities for applications in medical imaging and dosimetry. Notably, h-BN demonstrates a linear response within the dose range of interest, showcasing excellent sensitivity, particularly at low doses and low photon energies. Additionally, h-BN samples exhibit remarkable reproducibility, with a standard deviation of less than 2.4%, albeit accompanied by significant fading. Regarding the trapping parameters underpinning the manifestation of the glow curves of the irradiated samples, use was made of the peak shape method with different models to estimate the order of kinetics (b), activation energy (E), and frequency factor (s) or escape probability and trap lifetime (τ). The data suggest that the TL glow peaks of the h-BN obey general-order kinetics. These findings underscore the transformative potential of h-BN layered material in advancing radiation dosimetry, particularly in medical physics fields. The inherent characteristics of h-BN, coupled with its effective atomic number, excellent linearity over a wide range of radiation doses especially for electron irradiation and better reproducibility, positioned it as a suitable tool for precise and reliable dose measurement in medical imaging and therapy, heralding a new frontier in radiation dosimetry.
Investigation of structural and TL kinetic parameters of smartphone screen protector glasses for applications in retrospective dosimetry
(2024-11-15) Muslima, Umme; Khandaker, Mayeen Uddin; Mat Nawi, S.N.; Lam, S.E.; Abdul Sani, S.F.; Bradley, D.A.; Saidur, R.; Tan, Y.S.; Osman, Hamid; Y. Hanfi, Mohamed; A.M. Issa, Shams
The study evaluated the structural and thermoluminescence (TL) kinetic parameters of smartphone screen protector glasses in order to use them for post-accident dose reconstruction from unplanned nuclear events. The fact that most individuals use mobile phones in working environments including nuclear power plant sites, served as the impetus for the study. The TL glow curves indicate the physical properties of the defects involved in the luminescence process; therefore, they have been analyzed to study the TL kinetic parameters by employing peak shape, initial rise and glow curve deconvolution method within the dose ranges from 2 to 50 Gy. The geometric factor (μg) ranges between 0.46 and 0.56, suggesting that Chen's general-order method can be used to compute the kinetic parameters, including activation energy (E), frequency factor (s) and trap lifetime (τ). The examined trapping parameters (E = 0.33–0.57 eV, s = 5.22E+03–8.65E+06 s−1 for peak shape and E = 0.36–0.96 eV, s = 2.90E+04–1.88E+11 s−1 for initial rise methods) suggest promise for TL dosimetry applications. Additionally, the observed lifetime (τ = 4.88E+5 s) implies the feasibility of dose reconstruction even several days after an accident, making it suitable for retrospective dosimetry. Micro-Raman spectroscopy revealed a clear correlation between increasing gamma radiation dose and microstructural damage. The analysis of intensity ratio (ID/ISi) for other components to silica, along with the area of deconvoluted micro-Raman spectra in high-frequency regions, indicated dose-dependent structural modifications and internal defect annealing. Further confirmation of structural alterations within the studied dose range was obtained through the analysis of crystallite size (Lc), dislocation density (δ), lattice strain (ɛ) and FWHM (Full Width at Half Maximum) from XRD (X-ray diffraction) patterns. These findings collectively suggest the potential of smartphone screen protector glass as a viable material for emergency dosimetry applications.
Investigation of the Radiographer's Adherence and Compliance With Radiation Protection and Infection Control Practices During COVID-19 Mobile Radiography
(Elsevier, 2023-05-11) Khandaker, Mayeen Uddin; Abuzaid, Mohamed M.; Mohamed, Ikhlas A.; Jastaniah, Saddig; Alshammari, Qurain T.; Alghamdi, Salem Saeed; Osman, Hamid; Ahmed, Amna Mohamed; Musa, Alamin; Medani, Afaf Mohamed Ahmed; Lam, S.E.; Bradley, D.A.
Radiological staff, especially radiographers, work as front liners against the COVID-19 outbreak. This study aims to assess compliance with radiation protection and infection control practices during COVID-19 mobile radiography procedures. This cross-sectional study included 234 radiographers (females, 56%, n = 131; males, 44%, n = 103) who were asked to complete an online questionnaire consisting of demographic data, radiation protection and infection control practices during COVID-19 portable cases, and knowledge and awareness. After informed consent was completed, SPSS statistical software was used for the data analysis. The most common age group of participants ranged from 18 to 25 years old (30.3%, n = 71). Bachelor's degree holders were 74.4% (n = 174). Most radiographers (39.7%, n = 93) had a working experience of 1–5 years, followed by 27.8% (n = 65) with more than 16 years of experience. Most respondents (62.4%, n = 146) handled approximately 1–5 cases daily, the majority of them (56%, n = 131) stated affirmatively they had obtained special training to handle COVID-19, and when inquired if they had received any special allowances for handling COVID-19 suspected/confirmed cases most of them stated negative (73.9%, n = 173). Most participants stated that they always wear a TLD during portable cases (67.1%, n = 157) and a lead apron (51.7%, n = 121). Around 73% (n = 171) knew the latest information on COVID-19 and attended the COVID-19 awareness course. A significant association was found between the work experience of the radiographers and their responses to following the best practices (p = 0.018, α = 0.05). Radiographers who had COVID-19 training (μ = 48.78) tend to adhere more to best practices than those who have not (p = 0.04, α = 0.05). Further, respondents who handled more than 16/more COVID-19 suspected/confirmed cases followed the best practices more (μ = 50.38) than those who handled less (p = 0.04, α = 0.05). This study revealed detailed information on radiation protection and infection control practices during COVID-19 mobile radiography. It has been observed that the participants/radiographers have good knowledge and awareness of radiation protection and infection-control practices. The present results may be used to plan future requirements regarding resources and training to ensure patient safety.
Molecular disruptions in PTFE as the basis of a therapy-level skin dosimeter
(2024-10-24) Bradley, D.A.; Lam, S.E.; Taheri, A.; Mat Nawi, S.N.; Khandaker, M.U.; Abdul Sani, S.F.; Ung, N.M.; Alkhorayef, Mohammed
75 μm thick PTFE tape attracts interest, forming the basis of a potential skin dosimeter capable of utilization in radiotherapeutic external beam applications. The medium is readily available, for instance in the form of ordinary plumber's tape as used herein, typically of 12 mm width mounted on a spool. A60Co (mean energy 1.25 MeV) irradiator has been used to deliver doses in the range 0.1- to 10 Gy, with disrupted molecular bonds inspected via Raman spectrometry. The peak of greatest magnitude, at a wavenumber of ∼734 cm−1, corresponds to the difluoromethylene (CF2) symmetric stretching mode. Reduction in the peak intensity is seen to occur over the range 0.1- to 5 Gy, covering the values of skin dose typically arising in a single fractionated radiotherapeutic treatment. Results from these preliminary investigations point to a technique offering viability for radiotherapy skin dosimetry, utilizing a soft, low atomic number medium of particularly low-cost, also available in hypoallergenic form.
Tempered glass as a thermoluminescent medium for retrospective dosimetry
(Scopus, 2024-04) Muslima, Umme; Khandaker, Mayeen Uddin; Lam, S.E.; Nawi, S.N. Mat; Sani, S.F. Abdul; Osman, Hamid; Hanfi, Mohamed Y.; Sayyed, M.I.; Bradley, D.A.
Globally, the use of nuclear facilities and the potential risks associated with the dispersal of ionizing radiation due to natural disasters or technical failures are on the rise. These risks can have severe consequences for the environment and all living organisms, particularly humans. There is currently no practical method available to accurately estimate the radiation doses received by the surrounding areas and individuals in such situations. To address this issue, retrospective dosimetry can be employed to estimate the actual radiation dose, followed by the implementation of remediation techniques. Considering this need, tempered glass, which is commonly used as a screen protector for smartphones by the general public, has been identified as a promising medium for retrospective dosimetry. The present study aimed to investigate the thermoluminescence (TL) properties of six different types of tempered glass subjected to 60Co gamma rays, specifically examining the TL dose response, linearity, repeatability, and fading. Among the various glass samples tested, HD anti-peep tempered glass demonstrates a highly linear dose-response and the greatest dose sensitivity within the examined dose range of 2–50 Gy. Additionally, the HD anti-peep tempered glass exhibits minimal loss of TL yield (∼23%) at 28 days post-irradiation, making it particularly suitable for use as a retrospective dosimeter.
Tempered Glass as a Thermoluminescent Medium for Retrospective Dosimetry
(Elsevier, 2024-04-20) Muslima, Umme; Khandaker, Mayeen Uddin; Lam, S.E.; Nawi, S.N. Mat; Sani, S.F. Abdul; Osman, Hamid; Hanfi, Mohamed Y.; Sayyed, M.I.; Bradley, D.A.
Globally, the use of nuclear facilities and the potential risks associated with the dispersal of ionizing radiation due to natural disasters or technical failures are on the rise. These risks can have severe consequences for the environment and all living organisms, particularly humans. There is currently no practical method available to accurately estimate the radiation doses received by the surrounding areas and individuals in such situations. To address this issue, retrospective dosimetry can be employed to estimate the actual radiation dose, followed by the implementation of remediation techniques. Considering this need, tempered glass, which is commonly used as a screen protector for smartphones by the general public, has been identified as a promising medium for retrospective dosimetry. The present study aimed to investigate the thermoluminescence (TL) properties of six different types of tempered glass subjected to 60Co gamma rays, specifically examining the TL dose response, linearity, repeatability, and fading. Among the various glass samples tested, HD anti-peep tempered glass demonstrates a highly linear dose-response and the greatest dose sensitivity within the examined dose range of 2–50 Gy. Additionally, the HD anti-peep tempered glass exhibits minimal loss of TL yield (∼23%) at 28 days post-irradiation, making it particularly suitable for use as a retrospective dosimeter.
Thermoluminescence characterization of flooring tiles from Malaysia for potential use in retrospective dosimetry
(Scopus, 2024-08) Nawi, S.N. Mat; Khandaker, M.U.; Sani, S.F. Abdul; Lam, S.E.; N.A.I., H. Osman; Ishak, Md; Saidur, R.; Bradley, D.A.
In the event of natural disasters or technical malfunctions at nuclear sites, the surrounding media, including individuals, may be subject to unforeseen radiation exposure. Thus, it is not possible to determine the precise level of radiation exposure that each person has received in this scenario. To handle such a problem, the use of retrospective dosimetry can offer an accurate evaluation of the radiation dose acquired as a result of such incidents. This information enables the development of suitable remedial actions. Normally, in the region that has been impacted, several artifacts can serve as natural dosimeters. The study involved the utilization of locally available seven different brands of flooring tiles in Malaysia for the possibility of being used in retrospective dosimetry through exposures to 60Co gamma-rays within a range of 10–200 Gy. To understand the luminescence features of this material, a convenient thermoluminescence (TL) technique has been employed. The dosimetric features of the samples were investigated, including their effective atomic numbers (Zeff), reproducibility, glow curve, dose response, sensitivity, linearity index, energy dependency and fading, which is representative of the usual TL method. Additionally, by analyzing the glow curves of the irradiated samples together with the peak shape method and the initial rise methods, several kinetic parameters, including the kinetic orders (b), activation energy (E) or trap depth, frequency factor (s) or escape probability, and trap lifetime (τ) were calculated. Different kinds of tiles exhibit distinct scenarios in terms of kinetic characteristics. T1 sample exhibits the highest degree of sensitivity and a highly linear dose response among the tile samples that were evaluated. Also, T1, T3, and T5 samples show minimal loss of TL intensity (∼38–39%) one year after irradiation, making them ideal for use as a retrospective dosimeter.
Thermoluminescence Characterization of Flooring Tiles From Malaysia for Potential Use in Retrospective Dosimetry
(Elsevier, 2024-08-15) Nawi, S.N. Mat; Khandaker, M.U.; Sani, S.F. Abdul; Lam, S.E.; Osman, H.; Ishak, N.A.I. Md; Saidur, R.; Bradley, D.A.
In the event of natural disasters or technical malfunctions at nuclear sites, the surrounding media, including individuals, may be subject to unforeseen radiation exposure. Thus, it is not possible to determine the precise level of radiation exposure that each person has received in this scenario. To handle such a problem, the use of retrospective dosimetry can offer an accurate evaluation of the radiation dose acquired as a result of such incidents. This information enables the development of suitable remedial actions. Normally, in the region that has been impacted, several artifacts can serve as natural dosimeters. The study involved the utilization of locally available seven different brands of flooring tiles in Malaysia for the possibility of being used in retrospective dosimetry through exposures to 60Co gamma-rays within a range of 10–200 Gy. To understand the luminescence features of this material, a convenient thermoluminescence (TL) technique has been employed. The dosimetric features of the samples were investigated, including their effective atomic numbers (Zeff), reproducibility, glow curve, dose response, sensitivity, linearity index, energy dependency and fading, which is representative of the usual TL method. Additionally, by analyzing the glow curves of the irradiated samples together with the peak shape method and the initial rise methods, several kinetic parameters, including the kinetic orders (b), activation energy (E) or trap depth, frequency factor (s) or escape probability, and trap lifetime (τ) were calculated. Different kinds of tiles exhibit distinct scenarios in terms of kinetic characteristics. T1 sample exhibits the highest degree of sensitivity and a highly linear dose response among the tile samples that were evaluated. Also, T1, T3, and T5 samples show minimal loss of TL intensity (∼38–39%) one year after irradiation, making them ideal for use as a retrospective dosimeter.
Thermoluminescent characterization and defect studies of graphite-rich media under high dose neutron exposure
(Daffodil International University, 2023-06-23) Khandaker, Mayeen Uddin; Nawi, S.N. Mat; Lam, S.E.; Sani, S.F. Abdul; Islam, Mohammad Amirul; Islam, M.A.; Naseer, K.A.; Osman, Hamid; Bradley, D.A.
Thermoluminescence (TL) materials have a broad variety of uses in various fields, such as clinical research, individual dosimetry, and environmental dosimetry, amongst others. However, the use of individual neutron dosimetry has been developing more aggressively lately. In this regard, present study establishes a relationship between the neutron dosage and the optical property changes of graphite-rich materials caused by high doses of neutron radiation. This has been done with the intention of developing a novel, graphite-based radiation dosimeter. Herein, the TL yield of commercially graphite-rich materials (i.e. graphite sheet, 2B and HB grade pencils) irradiated by neutron radiation with doses ranging from 250 Gy to 1500 Gy has been investigated. The samples were bombarded with thermal neutrons as well as a negligible amount of gamma rays, from the nuclear reactor TRIGA-II installed at the Bangladesh Atomic Energy Commission. The shape of the glow curves was observed to be independent of the given dosage, with the predominant TL dosimetric peak maintained within the region of 163 °C–168 °C for each sample. By studying the glow curves of the irradiated samples, some of the most well theoretical models and techniques were used to compute the kinetic parameters such as the order of kinetics (b), activation energy (E) or trap depth, frequency factor (s) or escape probability, and trap lifetime (τ). All of the samples were found to have a good linear response over the whole dosage range, with 2B grade of polymer pencil lead graphite (PPLGs) demonstrating a higher level of sensitivity than both HB grade and graphite sheet (GS) samples. Additionally, the level of sensitivity shown by each of them is highest at the lowest dosage that was given, and it decreases as the dose increases. Importantly, the phenomenon of dose-dependent structural modifications and internal annealing of defects has been observed by assessing the area of deconvoluted micro-Raman spectra of graphite-rich materials in high-frequency areas. This trend is consistent with the cyclical pattern reported in the intensity ratio of defect and graphite modes in previously investigated carbon-rich media. Such recurrent occurrences suggest the idea of employing Raman microspectroscopy as a radiation damage study tool for carbonaceous materials. The excellent responses of the key TL properties of the 2B grade pencil demonstrate its usefulness as a passive radiation dosimeter. As a consequence, the findings suggest that graphite-rich materials have the potential to be useful as a low-cost passive radiation dosimeter, with applications in radiotherapy and manufacturing.