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The objective of this work is to review and assess the potential of Mg B 4 O 7 :Ce,Li to fill in the gaps where the need for a new material for optically stimulated luminescence (OSL) dosimetry has been identified. We offer a critical assessment of the operational properties of Mg B 4 O 7 :Ce,Li for OSL dosimetry, as reviewed in the literature and complemented by measurements of thermoluminescence spectroscopy, sensitivity, thermal stability, lifetime of the luminescence emission, dose response at high doses (>1000 Gy), fading and bleachability. Overall, compared with Al 2 O 3 : C , for example, Mg B 4 O 7 :Ce,Li shows a comparable OSL signal intensity following exposure to ionizing radiation, a higher saturation limit (ca 7000 Gy) and a shorter luminescence lifetime (31.5 ns). Mg B 4 O 7 :Ce,Li is, however, not yet an optimum material for OSL dosimetry, as it exhibits anomalous fading and shallow traps. Further optimization is therefore needed, and possible avenues of investigation encompass gaining a better understanding of the roles of the synthesis route and dopants and of the nature of defects. [ABSTRACT FROM AUTHOR]

The objective of this work is to review and assess the potential of MgB4O7:Ce,Li to fill in the gaps where the need for a new material for optically stimulated luminescence (OSL) dosimetry has been identified. We offer a critical assessment of the operational properties of MgB4O7:Ce,Li for OSL dosimetry, as reviewed in the literature and complemented by measurements of thermoluminescence spectroscopy, sensitivity, thermal stability, lifetime of the luminescence emission, dose response at high doses (>1000 Gy), fading and bleachability. Overall, compared with Al2O3:C, for example, MgB4O7:Ce,Li shows a comparable OSL signal intensity following exposure to ionizing radiation, a higher saturation limit (ca 7000 Gy) and a shorter luminescence lifetime (31.5 ns). MgB4O7:Ce,Li is, however, not yet an optimum material for OSL dosimetry, as it exhibits anomalous fading and shallow traps. Further optimization is therefore needed, and possible avenues of investigation encompass gaining a better understanding of the roles of the synthesis route and dopants and of the nature of defects.

The present work reports swift heavy ion (SHI) induced thermoluminescence (TL) dosimetric properties and density functional theory (DFT) studies of Eu doped MgB 4 O 7 phosphor. Comparative investigations of structural, and luminescent properties of MgB 4 O 7 :Eu phosphor upon irradiation by 100 MeV Ag7+ and Ni7+ ion beams at the varied fluence range from 1 × 1010 ion/cm2 to 5 × 1012 ion/cm2 are presented systematically. Eu doped MgB 4 O 7 phosphor is prepared by facile hydrothermal method. X-ray diffraction pattern of the material reveals its orthorhombic structure with crystallite size of ∼30 nm. Fourier transform infrared spectroscopy (FTIR) studies demonstrate loss of crystallinity of material after the SHI irradiations. Correlation of stopping powers and projectile range calculations is performed using SRIM software. The investigated photoluminescence properties show emission bands located in the orange-red region with prominent peaks centered at ∼593 nm and ∼625 nm corresponding to 5D 0 →7F 1 and 5D 0 →7F 2 transitions of Eu3+ion. The influence of ion beam fluence on the photoluminescence properties has been explored. Variation in the intensity of the PL peaks without any shift in the peak positions is observed at different ion fluence. The TL glow curve of phosphor exhibits two major dosimetric peaks (a) at 185 °C and 275 °C and (b) at 172 °C and 273 °C upon Ag7+ and Ni7+ ion beam irradiation respectively. The phosphor shows fairly good linear dose response in the range of 1 × 1010 ion/cm2 to 5 × 1012 ion/cm2. Fading measurements reveal 10% and 12% fading for the irradiation of Ag7+ and Ni7+ ions respectively in two months. Trapping parameter calculations of SHI irradiated phosphors are carried out via various TL glow curve analysis methods such as, peak shape method, whole glow peak method, and glow curve deconvolution method. Efficient thermoluminescence properties of MgB 4 O 7 :Eu make it a potential phosphor material and promise to provide avenue into swift heavy ion dosimetry applications. DFT computational studies performed to obtain the electronic structure of Eu doped MgB 4 O 7 phosphor support the experimental results of crystal structure, symmetry and electronic structure studies. • Swift heavy ion induced thermoluminescence (TL) properties of MgB 4 O 7 :Eu phosphor. • TL response of MgB 4 O 7 :Eu phosphor induced by Ag7+ and Ni7+ ion beam irradiation. • Electronic properties of MgB 4 O 7 :Eu phosphor using first principles calculations via DFT. • Determination of trapping parameters via PS, WGP, and GCD method. [ABSTRACT FROM AUTHOR]

The objective of this work is to demonstrate the feasibility of 2D dosimetry using optically stimulated luminescent (OSL) films based on MgB4O7:Ce,Li and to identify current limitations of this material for this application. A small quantity of test films was produced and read using a laser-scanning OSL reader after irradiation. The OSL luminescence and dosimetric properties were also investigated. The results demonstrate the advantage of the fast luminescence lifetime associated with Ce3+ emission (∼31.5 ns) for 2D dosimetry based on laser-scanning readout, since it minimizes the need for pixel-bleeding correction. The signal could be bleached satisfactorily using a fluorescence lamp and a long-pass filter. A dose response curve could be obtained with pieces of films simulating steep dose gradients and the dose response obtained using the signal from the center of such piece films was linear up to 10 Gy. Short and long-term phosphorescence components were observed in the luminescence signal of MgB4O7:Ce,Li, but their contribution with respect to the fast OSL signal is relatively small and should decrease with increasing laser scan rates. In spite of the high OSL sensitivity and linear response, the main disadvantage of MgB4O7:Ce,Li at the moment is the lack of a better understanding of the processes responsible for the sensitivity changes and fading of the OSL signal. Although the bleaching applied here allowed to reduce the residual OSL signal to minimum levels (

This work reports on the advances towards the development of a new optically stimulated luminescence (OSL) material based on MgB 4 O 7 :Ce,Li, which has high sensitivity to ionizing radiation, low effective atomic number (Z eff = 8.2), and fast luminescence when doped with cerium (Ce3+ emission). MgB 4 O 7 samples doped with 0.3 mol% Ce and 10 mol% Li were synthesized by solution combustion synthesis (SCS) and annealed at various temperatures. The samples were characterized using photoluminescence, radioluminescence (RL), thermoluminescence (TL), and both blue- and green-stimulated luminescence (BSL and GSL). The OSL emission spectrum and sensitization were investigated as well. Further measurements of samples prepared with and without urea were carried out using differential scanning calorimetry (DSC), X-ray diffraction (XRD), TL and OSL to investigate the synthesis procedure. The results show that the use of high-purity Mg precursor in the MgB 4 O 7 :Ce,Li synthesis eliminates a competing recombination center emitting at ∼580 nm (possibly Mn2+), resulting in a ∼4.5 increase in the TL and the OSL in the UV region (290–390 nm). We have also confirmed that the OSL emission spectrum is characteristic of Ce3+ emission with two peaks at ∼335 nm and ∼355 nm due to the transition from the 5d to the 2F 5/2 and 2F 7/2 levels of the ground state configuration. Photoluminescence data confirms these emission bands and show the associated 4f → 5d excitation bands of Ce3+ at ∼270 nm, ∼293 nm and ∼320 nm. The luminescence lifetime associated with the Ce3+ emission was determined to be 31.5 ns. The OSL stimulation spectrum shows an increase in the OSL signal with an increase in the photon energy. The best annealing for the material prepared with high-purity Mg precursor was 700 °C for 2 with fast cooling, but no significant dependence on the annealing time or cooling regime was seen in the conditions investigated. Sensitization was observed in all TL and OSL measurements, but the TL sensitization was considerably reduced in the samples synthesized with high-purity Mg precursor. Additional studies by DSC, XRD, TL and OSL showed that, while the reaction was confirmed to be exothermic and higher TL and OSL signals were observed using urea, combustion is not essential to synthesize MgB 4 O 7 :Ce,Li with intense TL and OSL signals. In summary, MgB 4 O 7 :Ce,Li remains one of the most promising alternatives to the only two commercially available materials (Al 2 O 3 :C and BeO) in OSL dosimetry. Remaining challenges include to minimize the presence of shallow traps, which are likely responsible for the initial fading observed in the material, to better understand the nature of the TL and OSL sensitization in this material, and to find the optimum synthesis procedure to produce the material. [ABSTRACT FROM AUTHOR]

Thermoluminescence properties of undoped and Dy doped MgB 4 O 7 compounds were studied with the irradiation of 252Cf source. The TL kinetic parameters of MgB 4 O 7 : Dy were studied by computer glow curve deconvolution (CGCD) method. The glow curve structures of 1% Dy doped magnesium tetraborate compound consists of at least five glow peaks with a main dosimetric peak at about 220 °C. The highest sensitivity which is approximately 1.90 and 1.47 times higher than that of TLD-600 and TLD-700 was found for MgB 4 O 7 : Dy (1 mol%). The results clearly showed that Dysprosium doped magnesium borate has a potential to be considered as the thermoluminescence neutron + gamma dosimeter. • TL properties of MgB 4 O 7 :Dy+3 investigated using 252Cf source for the first time. • The CGCD results show that MgB 4 O 7 : Dy+3 consists of at least five glow peaks. • The crystal structure of the host lattice is not altered with the Dy+3 doping. • The luminescence intensity is higher than TLD-600 and TLD-700 respectively. • So, MgB 4 O 7 : Dy+3 can be considered as neutron + gamma dosimeter. [ABSTRACT FROM AUTHOR]

The aim of this work was to elucidate the role of defects in energy storage and transfer in X-ray irradiated MgB 4 O 7. Pure and terbium- and erbium-doped magnesium tetraborate was synthesized by the solid state reaction method. The band gap value Eg = 9 eV was estimated using the method of X-ray photoelectron spectroscopy (XPS). Absorption attributed to defects with energy levels located in the forbidden band was found from UV–vis spectroscopy. An interpretation of the thermoluminescence and radioluminescence spectra of pure and doped magnesium tetraborate was proposed. Two different mechanisms for enhancing the thermoluminescent response of MgB 4 O 7 upon doping with rare earth elements were demonstrated. • Polycrystalline pure and doped MgB4O7 was synthesized by the solid state route • The band gap value in MgB4O7 equal to 9 eV was obtained by XPS method • RL signal in MgB4O7 at 360 nm is most likely of exciton nature • TL signal at 550 nm is due to oxygen defects in MgB4O7 • The mechanisms of RL and TL in irradiated MgB4O7: Er and MgB4O7:Tb are different [ABSTRACT FROM AUTHOR]

The objective of this work is to demonstrate that MgB 4 O 7 :Ce,Li, a new optically stimulated luminescence (OSL) dosimetric material, shows improved response for proton therapy dosimetry, with less reduction in luminescence detector efficiency with the particle linear energy transfer (LET). MgB 4 O 7 :Ce,Li was synthesized and its luminescence efficiency as a function of LET was characterized for dose-averaged LET values from 0.73 keV/μm up to 74.9 keV/μm using proton, 4He, and 12C ion beams. Commercial Al 2 O 3 :C OSLDs were also used for comparison. Monte Carlo simulations were used to predict the material's response in pristine and spread-out Bragg peaks (SOBP), suggesting the MgB 4 O 7 :Ce,Li would offer minimum quenching in proton beams of energies relevant to radiotherapy. This prediction was confirmed by irradiations of MgB 4 O 7 :Ce,Li and Al 2 O 3 :C along SOBPs from proton beams. The results demonstrate that new OSL materials optimized for proton dosimetry can be developed using their dose response to low-LET radiation as a guide during material development. • A new OSL material, MgB 4 O 7 :Ce,Li, was investigated for proton therapy dosimetry. • Monte Carlo simulations were used to predict the material's response for proton and carbon ion beams. • Simulations indicate that MgB 4 O 7 :Ce,Li should perform well for proton beams. • Predictions were confirmed experimentally using clinically relevant proton beams. [ABSTRACT FROM AUTHOR]

Abstract: Electron paramagnetic resonance (EPR), thermally stimulated luminescence (TSL), photoacoustic spectrometric (PAS) and fluorescence studies were conducted on gamma-irradiated MgB4O7: Tm phosphor. EPR spectra of irradiated samples revealed the formation of , a hole-trapped radical at room temperature. The principal values for the and tensors are , and , , respectively. In addition to this, the radical without any hyperfine structure was identified as and ). TSL studies showed the presence of an intense glow peak around 470K and a weak shoulder at 550K. Temperature dependence studies of the EPR signals in the range 300–600K showed the thermal destruction of radical around 470K. The observed TSL emission is caused by the recombination of thermally released holes from radical with ion. The energy released in the electron–hole recombination process is used for the excitation of resulting in a prominent glow 470K. TSL emission studies confirmed that acts as luminescent center for the prominent peak at 470K. The trap depth for this peak has been determined to be from both TSL and EPR methods. [Copyright &y& Elsevier]

Measurements of entrance doses and extremity doses in mix fields are quite complex, particularly when it comes to neutron radiation. For this reason, films of transparent and flexible polymers loaded with luminescent materials sensitive to photons and neutrons were developed experimentally. However, there is a demand for optimizing the shape and arrangement of the crystals in these films. Using Monte Carlo simulations with the PHITS code, we simulated a geometry so that it would be possible to measure the dose deposited by the primary neutrons and by neutrons scattered backwards by a water phantom. We evaluated the sensitivity of the films loaded with MgB 4 O 7 produced with different boron isotopes. We found that, in the case of a photon source, the energy deposited in the MgB 4 O 7 particles comes from the photons that directly impact the film and that there was no significant difference in sensitivity for the different isotopes. However, using neutron beams, the water phantom is responsible for backscattering the neutrons that deposit the dose in the film produced with B-10, indicating that films can be used to detect albedo neutrons from an irradiated body and differentiate them from gamma irradiation. • Films loaded with MgB 4 O 7 polycrystals using B-10 and B-11 to detect thermal neutrons were simulated. • The dose deposited in the films due to the albedo neutrons was evaluated. • Films of MgB 4 O 7 can detect the differential dose due to albedo neutrons on the surface of the body. [ABSTRACT FROM AUTHOR]