Nanoparticles of Al2O3:Cr as a sensitive thermoluminescent material for high exposures of gamma rays irradiations

Aluminum Oxide (Al₂O₃) doped with proper activators is a highly sensitive phosphor commonly used for radiation dosimetry using thermoluminescence (TL) technique. Nanoparticles of this material activated with Chromium (Cr) have been synthesized using the propellant chemical combustion technique and studied for their TL response. They were characterized by X-ray diffraction and scanning electron microscope. The synthesized material has spherical nanoparticles with grain size around 25 nm. These nanoparticles were exposed to heavy doses from γ-rays of ¹³⁷Cs. The TL glow curves show a prominent peak at around 474 K. This peak is found to be sensitive for high exposures of γ-rays and has linear response in the range of 100 Gy-20 kGy without showing saturation. This remarkable result suggests that Al₂O₃:Cr nanoparticles might be used for the dosimetry of food and seed irradiations.     

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

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

Thermoluminescence properties of irradiated chickpea and corn

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

The thermoluminescence properties of natural CaF2 after β-irradiation

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

Investigation of the stability of the radiation sensitivity of TL peaks of quartz extracted from tiles

One of the most important mineral in dosimetric investigation is quartz, which is found abundantly in archaeological and geological materials. Although there are many studies about its thermoluminescence (TL) properties in the literature, it may exhibit different properties for each quartz mineral extracted from the different region of the world. In the present work, the stabilities and dose responses of glow peaks of quartz obtained from the tiles of Kubad Abad Palace in central Turkey were investigated after annealing at 500 and 600 °C for 1 h. The variation of radiation sensitivity of TL peaks of the quartz grains extracted from tiles are found to be more stable after annealing at 600 °C than 500 °C for 1 h. The TL dose responses of glow peaks of annealed and unannealed quartz samples were also studied up to approximately 3 kGy. It was observed that the pre-irradiation heat treatments affect the dose response behaviors of glow peaks.     

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

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

Study of the luminescent properties of KMgF3:Sm

The photoluminescence (PL), radioluminescence (RL) and thermoluminescence (TL) of KMgF₃ doped at several Sm concentrations have been investigated. The maximum TL and RL yield under beta irradiation has been observed in KMgF₃:Sm 0.02 mol%. The glow curve of this doped perovskite is made up of at least five peaks located at 95, 120, 160, 270, and 330 °C. The third peak appears to be the most convenient for personal or environmental dosimetry, since it shows no fading and good linearity within the investigated dose range (0.020-200 Gy). From the RL and PL spectra it has been found that most of KMgF₃:Sm emission is located at wavelengths higher than 650 nm. This emission, which is characteristic of Sm²⁺, makes this doped compound attractive for fiber-optic dosimetry.     

A versatile integrated system for thermoluminescence and optically stimulated luminescence measurements

A versatile integrated reader system for TL and OSL measurements of phosphor materials has been described for luminescence research applications. The developed integrated reader system works either in TL or OSL or TL-OSL mode. In the OSL operation, besides the conventional CW-OSL, POSL and LM-OSL modes a novel non-linear OSL (NL-OSL) method has been incorporated in the reader system. The optical stimulation unit consists of four high power LEDs fitted in four channels and optically focused on the sample. Each of the LED is capable of delivering up to 80 mW/cm² light power at the sample position. The LEDs with peak wavelength λ_p ≈ 470 nm and 530 nm and Δλ ≈ 20 nm have been used for optical stimulation of the samples. A PID temperature controller has been used for generating and controlling user defined heating profiles for the TL measurements in the reader system. The reader system covers a wide dynamic dose range of 10 μGy to 10³ Gy for TL/OSL measurements. The OSL grade α-Al₂O₃:C phosphor was used to test the reader system and investigate its impact on low dose assessment for personnel and environmental monitoring. The design concept of the reader system and the results of dose measurements are discussed.     

Thermoluminescence properties of nanocrystalline K2Ca2(SO4)3:Eu irradiated with gamma rays and proton beam

Thermoluminescence properties of nanocrystalline K₂Ca₂(SO₄)₃:Eu prepared by ball milling technique have been studied and the nanophosphor’s suitability as an effective gamma radiation and proton beam dosimeter material has been examined. It is found that the nanophosphor is suitable for dosimetry over a very wide range of doses ∼1 Gy to 1 kGy for gamma radiation. And for proton beam the same nanophosphor shows a more or less linear response for the dose range 0.1-100 Gy. A comparative study of this nanophosphor with its corresponding microcrystalline form (prepared by solid-state diffusion method) as well as the nanocrystalline form prepared by (the more conventional) co-precipitation technique has shown that the nanophosphor prepared by the ball milling technique is in almost all respects better than the other two forms reported earlier.     

Optical absorption and thermoluminescence studies in 100 MeV swift heavy ion irradiated CaF2 crystals

Pure and Ytterbium (Yb) doped Calcium fluoride (CaF₂) single crystals were irradiated with 100 MeV Ni⁷⁺ ions for fluences in the range 5 × 10¹¹-2.5 × 10¹³ ions cm⁻². The irradiated crystals were characterized by Optical absorption (OA) and Thermoluminescence (TL) techniques. The OA spectra of ion irradiated pure CaF₂ crystals showed a broad absorption with peak at ∼556 nm and a weak one at ∼220 nm, whereas the Yb doped crystals showed two strong absorption bands at ∼300 and 550 nm. From the study of OA spectra, the defect centers responsible for the absorption were identified. TL measurements of Ni⁷⁺ ion irradiated pure CaF₂ samples indicated a strong TL glow with peak at ∼510 K. However, the Yb doped crystals showed two TL glows at ∼406 and 496 K. The OA and TL intensity were found to increase with increase of ion fluence upto 1 × 10¹³ ions cm⁻² and thereafter it decreased with further increase of fluence. The results obtained are discussed in detail.     

Thermoluminescence, photoluminescence, photo-stimulated luminescence and optical studies on X-ray irradiated KBr:Ce crystals

This paper reports thermoluminescence (TL) glow and emission, optical absorption and optically stimulated emission studies made on Ce³⁺ doped KBr single crystals irradiated at room temperature. Optical absorption and photoluminescence studies confirm the presence of cerium ions in the trivalent state. A broad and intense blue emission around at 290 and 390 nm, attributable to the transition from 5d excited state to the 4f¹ ground state of Ce³⁺ ions could be observed in the photoluminescence emission. Two TL glow peaks were observed at 374 and 422 K. Presence of characteristic emission due to Ce³⁺ ions in the optically stimulated emission at the F-band confirms the participations of the Ce³⁺ ions in the defect production and recombination processes.     

Thermoluminescent characteristics of topaz from Sabser mine near Sakardu in northern Pakistan

Topaz, a naturally occurring aluminium fluorosilicate mineral, shows thermo-luminescence (TL) after irradiation to gamma rays. The TL characteristics (glow curve, dose response/intensity, sensitivity, energy response, fading, reusability and mechanical stability) of topaz collected from the Sabser mine in the vicinity of Sakardu in northern Pakistan were studied. The purpose of this study was to design and develop a TLD (thermoluminescence dosimeter) based on topaz. The samples of topaz from this mine were cut into square chips of dimensions 3.2 × 3.2 mm with thickness 0.9 mm, which are suitable for the TLD reader. Gamma dose was given to the chips from ⁶⁰Co and/or ¹³⁷Cs gamma irradiators. The TL glow curves of the chips revealed stable peak at about 260 °C. The height of this peak rose linearly with increase of dose levels. The TL response versus dose (calibration curve) showed the linear behaviour between 10⁻² and 10² Gy without saturation. Dose response was independent of gamma energies of ⁶⁰Co and ¹³⁷Cs. The response of standard sized chips of topaz remained constant within ±11% deviation from initial value after 30 cycles of reuse. The rate of fading of topaz chips of this mine were studied up to four months, which was fast for initial few hours and slowed after a few days. The chips remained mechanically stable during handling in all types of experiments. Standard sized topaz chips of Sabser mine can effectively and efficiently be used as a TLD.     

Luminescence studies on gamma irradiated RbCl:Sm and RbBr:Smcrystals

This paper presents and discusses the results obtained on the thermoluminescence (TL) and other optical studies of gamma irradiated RbCl:Sm³⁺ and RbBr:Sm³⁺ crystals. Samarium when doped into the RbCl and RbBr is found to enter the host lattice in its trivalent state and act as electron trap during gamma irradiation, there by partially converting itself to Sm²⁺. The photoluminescence (PL) spectra of both RbCl and RbBr crystals doped with Sm exhibit the strong red/orange emissions of Sm corresponding to ⁴G_5/2 → ⁶H_9/2 (red) and ⁴G_5/2 → ⁶H_7/2 (orange) transitions. Z₃ centers are observed in RbBr on F bleaching subsequent to gamma irradiation and a TL glow peak attributable to the same has been identified. The thermoluminescence (TL) glow curve explains the defect annihilation process to be due to the mobilization of two different kinds of traps created as a result of exposure to high energy irradiation in both the cases. Spectral distribution under the thermoluminescence emission (TLE) and optically stimulated emission(OSL), support the idea that defect annihilation process to be due to thermal release of F electron in RbCl:Sm³⁺ and in RbBr:Sm³⁺ crystals. Both Sm³⁺ and Sm²⁺ emissions were observed in the thermoluminescence emission of the crystals.     

Thermoluminescence properties of isostructural K2YF5 and K2GdF5 crystals doped with Tb in response to α, β and X-ray irradiation

The thermoluminescence (TL) properties of isostructural fluoride K₂YF₅ and K₂GdF₅ crystals doped with Tb³⁺ of different concentrations have been studied in the temperature range from 30 to 500 °C after α, β and X-ray irradiation. Strongly different structures of TL glow curves following α or β irradiation have been found for Tb³⁺ doped K₂YF₅ for all studied concentrations of Tb³⁺ whereas for K₂GdF₅ crystals the different TL curves after α or β irradiation are detected only for heavily doped samples. On the other hand, all the studied materials show similar TL glow curves after β or X-ray irradiation. It has been discovered that K₂YF₅ doped with 1 at.% Tb³⁺ has TL radiation sensitivity to β irradiation of the same order as that of the well known TLD-100 (LiF:Mg,Ti) phosphor and much higher sensitivity to α irradiation. The TL mechanism in K₂YF₅ and K₂GdF₅ doped with Tb³⁺ is discussed by taking into account the TL emission spectra from irradiated samples, which are identical to the emission spectra of the Tb³⁺ ions in these hosts under photo-excitation, and the kinetics parameters obtained with the method of various heating rates.     

Studies on new neutron-sensitive dosimeters using an optically stimulated luminescence technique

The neutron response of detectors prepared using α-Al₂O₃:C phosphor developed using a melt processing technique and mixed with neutron converters was studied in monoenergetic neutron fields. The detector pellets were arranged in two different pairs: α-Al₂O₃:C + ⁶LiF/α-Al₂O₃:C + ⁷LiF and α-Al₂O₃:C + high-density polyethylene/α-Al₂O₃:C + Teflon, for neutron dosimetry using albedo and recoil proton techniques. The optically stimulated luminescence response of the Al₂O₃:C + ^6,7LiF dosimeter to radiation from a ²⁵²Cf source was 0.21, in terms of personal dose equivalent H_p(10) and relative to radiation from a ¹³⁷Cs source. This was comparable to results obtained with similar detectors prepared using commercially available α-Al₂O₃:C phosphor. The H_p(10) response of the α-Al₂O₃:C + ^6,7LiF dosimeters was found to decrease by more than two orders of magnitude with increasing neutron energy, as expected for albedo dosimeters. The response of the α-Al₂O₃:C + high-density polyethylene/α-Al₂O₃:C + Teflon dosimeters was small, of the order of 1% to 2% in terms of Hp(10) and relative to radiation from a ¹³⁷Cs source, for neutron energies greater than 1 MeV.     

Ion irradiation effects on tungsten-oxide films and charge state effect on electronic erosion

We have studied electronic- and atomic-structure modifications of polycrystalline WO₃ films (bandgap of ∼3 eV) by ion irradiation. WO₃ films were prepared by oxidation of W films on MgO substrates and of W sheets. We find disordering or amorphization, the lattice expansion of ∼1.5% and bandgap increase of 0.2 eV after 90 MeV Ni ion irradiation at ∼3 × 10¹² cm⁻². A broad peak of optical absorption appears around 1.6 μm by ion irradiation. We also find that the erosion yield by high-energy ions with the equilibrium charge exceeds 10⁴ and that the erosion yield under ion impact with non-equilibrium charge (90 MeV Ni⁺¹⁰) is ∼1/5 of that with the equilibrium charge (89 MeV Ni⁺¹⁹). Effects of depth dependence of the ion mean charge on the erosion yields are discussed. The erosion yield by low-energy ions is also presented.     

Investigation and application of hollow anode glow discharge ion source

In the present work, a new shape of a glow discharge ion source has been designed, fabricated and constructed at Accelerators and Ion Sources Department, Nuclear Research Center, Egyptian Atomic Energy Authority, Egypt. The discharge and output beam characteristics of the ion source at different operating gas pressures have been measured at the optimum distance between the anode and the cathode (3.5 mm) using hydrogen and nitrogen gases. Furthermore, mixture of different gases was studied, e.g., addition of H₂ gas to N₂ gas with different ratios has been investigated. Finally, as an application of this new ion source, ion beam modification of insulators (glass) which depends on glass structure has been achieved. It has been found that, the transmission of light is decreased by coating the glass surface with Ar ion beam more than coating with plasma of Ar gas at the same pressure and the same exposure time. So we could use this ion source as a coating tool for borate glass surface. The parameters affected the glow discharge ion source efficiency have been examined carefully using a mixture of gases. Using helium gas, the glow discharge is in a turbulent state due to instabilities. An investigated H₂-N₂ mixture has been used in order to obtain an optimum percentage of the mixture of the two gases to increase the electric field necessary for ionization balance.     

Determination of self attenuation coefficient and relative TL efficiency of CaSO4:Dy, LiF:Mg,Cu,P and LiF:Mg,Ti TLDs - An alternate approach

Self attenuation of TL and relative TL efficiency of polytetra fluoro ethylene (PTFE) embedded CaSO₄:Dy disc, LiF:Mg,Ti (MTS) disc and LiF:Mg,Cu,P (MCP-N) chip were determined in the present study for photons of energy 10-34 keV. The relative TL efficiency was determined using an alternative approach in which ratio of experimental response and corrected theoretical response was used instead of measuring the absolute TL emission in photon counting mode. For CaSO₄:Dy disc, it was found that with increasing the proportion of CaSO₄:Dy phosphor in the disc, the light attenuation coefficient increases. The light attenuation coefficient of MTS disc and MCP-N chip was found to be 23.4 and 45.5 cm⁻¹, respectively. The relative TL efficiency in the photon energy range of 10-34 keV for MTS discs and MCP-N chips, evaluated in the present study matches well with the reported values in the literature.     

DyF3: A promising new TL material for gamma dosimetry

This research describes preliminary investigation of some radiation dosimetry characteristics of commercial dysprosium fluoride powder. The as-received aliquot has strong thermoluminescence (TL) emission with one sharp peak at ∼234 °C. The TL characteristics have been examined under excitation of gamma (γ) doses in the range 1 Gy-50 kGy from a ⁶⁰Co gamma source. The dose response was linear up to 100 Gy and a sub-linear response was observed at higher doses. The TL signal is observed to remain stable for aliquots irradiated to γ-doses in the range 1-10 Gy over one month storage period in dark at ambient temperature and humidity conditions. This paper recommends using DyF₃ in doping of TL materials which may be promising for future dosimeter development.