Optically Stimulated Luminescence Materials Research Articles

Giant enhancement of a long afterglow and optically stimulated luminescence phosphor BaCaSiO4: Eu2+ via Pr3+ codoping for optical data storage

The need for data storage is growing in modern society, and optical data storage (ODS) is considered one of the most promising storage techniques. However, significant challenges must be overcome, including improving the performance of volatile memory and expanding its storage capacity. In this study, we report a novel ortho-silicate phosphor, BaCaSiO4, doped with Eu2+, which exhibits sustained luminescence and optically stimulated luminescence (OSL). Following the Pr3+ co-doping, the long afterglow and OSL performance of BaCaSiO4: Eu2+ significantly improved owing to the substantial increase in trap density. Owing to numerous trapped and released electrons, the optical storage capacity of the OSL material significantly increased. As a proof-of-concept, ODS flexible media were fabricated using the obtained OSL material, based on which reversible information write-in and read-out were implemented using ultraviolet irradiation and optical/thermal stimulation, respectively. Furthermore, the OSL-based ODS mechanism was revealed through a comprehensive study of electron trapping, storage, and release kinetics.

Optically Stimulated Luminescence in LiF–MgF2 system and its response as medical radiation dosimeter

Optically Stimulated Luminescence (OSL) based dosimeters are garnering attention in the field of radiation dosimetry due to a number of benefits like portable equipment, easy and efficient excitation and read out process, re-readability of the dose etc.. Though varieties of fluoroperovskites have been studied as OSL materials, no research on LiMgF3 (Lithium Magnesium Fluoride) as an OSL material has yet been conducted. In the current work, LiF–MgF2 system with a low effective atomic number was synthesized using the high temperature solid state reaction approach and its OSL dosimetry properties were investigated. The prepared sample was thoroughly characterized by employing a variety of techniques, such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV–Vis (ultraviolet–visible) spectrophotometry. The structure of the sample was found to be polycrystalline with size in the micrometre range. OSL properties of LMF have been investigated for different doses of gamma and beta along with related OSL kinetic parameters. It exhibits good dose linearity under blue stimulation for gamma (100 mGy - 700 Gy) and beta (30 mGy - 5Gy) radiation. We have also investigated the reusability (3%), reproducibility (2–3%), and fading (45% in 40 days) of the phosphor. To check the viability of the sample in radiation dosimetry under medical treatment in radiotherapy, various dosimetric properties were studied in Linear Accelerator (LINAC) x-rays in MV energy range and Cobalt-60 gamma radiation. These studies include the response of the phosphor to various energies (called energy dependence), field size effect, the effect of the dose rate of the radiation beam, and relative depth dose response. The overall response of the phosphor (comparable with ion chamber in RT experiments) makes the material a potential candidate to be used as an OSL phosphor in medical radiation dosimetry.

Optically stimulated luminescence dosimetry on tissue equivalent LiF: Mg, Cu, Na, Si phosphor

Lithium fluoride (LiF) is one of the best tissue equivalent materials exhibiting good thermoluminescence (TL) properties, however it shows weak optically stimulated luminescence (OSL) response with blue light (470 nm) stimulation. Several research groups are working on improving the OSL properties of LiF phosphor. In an attempt, a thorough investigation on tissue equivalent LiF: Mg,Cu,Na,Si (MCNS) as a possible OSL material has been done in the current work. As the preparation route and particle size can modify the energy levels and optical transitions, the striking improvement is expected by preparing it in nanocrystalline form. The structural and morphological characterization has been done using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The OSL emission is observed in continuous wave mode under blue (460 nm) light stimulation. The OSL decay curve exhibits a significant increase in intensity which is ~2 times higher than LiF based commercial phosphor (TLD-100) irradiated with gamma dose of 0.1 Gy. The phosphor shows a linear dose response in the range of 0.1–20 Gy with almost constant decay rate. The phosphor has shown low residual signal which is good for its repetitive use. The OSL decay curve has been analysed and related parameters such as photoionization cross-section and decay constant are determined. ESR study has been done to identify the defect centres and describing the role of point defects and charge compensators involved in the luminescence process. This reveals the existence of Cu in Cu+ or Cu0 state. Good OSL properties suggests MCNS phosphor has a potential as a OSL dosimeter. The current study adds new knowledge and opens a new window to improve the OSL sensitivity of LiF material.

Demonstration of an optically stimulated luminescence (OSL) material with reduced quenching for proton therapy dosimetry: MgB4O7:Ce,Li

The objective of this work is to demonstrate that MgB4O7: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). MgB4O7: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 Al2O3: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 MgB4O7:Ce,Li would offer minimum quenching in proton beams of energies relevant to radiotherapy. This prediction was confirmed by irradiations of MgB4O7:Ce,Li and Al2O3: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.

Regulating electron traps of Eu2+-doped Ba1.6Ca0.4SiO4 persistent and optically stimulated luminescence phosphor toward optical data storage

Nowadays, the optical data storage (ODS) has already become one of the most promising data storage technologies in this digital era. Optically stimulated luminescence (OSL) material has recognized as a considerable potential candidate for the new-generation ODS. The improvement of volatile memory performance and the increase of storage capacity are two critical challenges to be solved. In this work which is reporting on, a new novel Eu2+-doped orthosilicate phosphor has been studied showing both persistent luminescence and OSL. The trap density is significantly enhanced by 10-fold via Dy3+ codoping. Information can be reversibly written into the traps by UV light illumination and then read out by optical or thermal stimulus. The capture and release dynamics of electrons by traps are studied in detail to reveal the OSL-based ODS mechanism. Moreover, as a proof-of-concept, ODS flexible medium is fabricated using the as-obtained OSL material to certify the application feasibility for erasable optical data write-in and read-out.

Application of optically stimulated luminescence in tandem systems for diagnostic radiology

The present work investigates the potential use of luminescent materials in tandem systems for diagnostic radiology. MgB4O7:Ce,Li (MBO) (Zeff = 8.1), borate glass (80–20MBO) (Zeff = 8.3) and Al2O3:C (Zeff = 10.9) are tested as optically stimulated luminescence (OSL) detectors. The first part of this work evaluates the energy response of the detectors exposed to standard radiation qualities, followed by the calculation of the tandem curve based on the ratio of the energy responses of the 80–20MBO/Al2O3:C and MBO/Al2O3:C detector pairs. The results indicate that the energy response of the OSL materials overresponds, for a low energy photon beam, by an order of 6 for Al2O3:C, 3.5 times for 80–20MBO and 1.7 times for MBO. The highest uncertainty in this measurement is found for Al2O3:C (16.6%). The results of the tandem analyses indicate that both pairs of detectors can be used for this application, although MBO/Al2O3:C had higher efficacy, compared to 80–20MBO/Al2O3:C. In both cases, the tandem curves are effective for energies below 50 keV, where steep energy behavior is observed and the highest uncertainty is observed for MBO/Al2O3:C (~18%).

Evaluation of MgB4O7:Ce, Li and Ce-doped 80MgB2O4–20MgB4O7 as alternative OSL materials for use in quality assurance of 6 MV photon beams

We investigated the potential use of two new borate matrices for quality assurance (QA) tests in radiotherapy. Both matrices, MgB4O7:Ce, Li (MBO) and Ce-doped 80MgB2O4–20MgB4O7 (80-20MBO), were doped with 0.5% cerium oxide. The following dosimetric properties of these materials prepared as pellets were tested: optically stimulated luminescence (OSL) sensitivity, dose response, fading, reproducibility, and the supralinearity index. Subsequently, the pellets were exposed to a 6 MV photon beam, and the percentage depth dose (PDD) curve, OSL response to different dose rates, and radiation field size dependencies were compared with those obtained with a reference detector (ionization chamber, I.C.) used in QA. The results indicated a higher OSL sensitivity of 80–20MBO as compared with MBO, on the order of 6- to 8-fold. The dose response of MBO presented a linear behavior within the range evaluated (20 mGy–2 Gy), unlike 80-20MBO, which had a supralinear behavior. The OSL signal of 80–20MBO was also marked by 60% fading within 5 h post irradiation; afterwards, the OSL signal stabilized. A better reproducibility of 80–20MBO compared with MBO was also observed. No dose rate dependence of the OSL response was observed; moreover, a maximum 5% standard deviation was seen in this test. For the field size tests, the pellets over-responded by 3.1% (80-20MBO) and 3.4% (MBO), in a 3 × 3 cm2 field, compared with the I.C. For the PDD, a high deviation was observed if compared with the I.C. data at the build-up region (at a depth d ≤ 2 cm), maximum 4.3% and 7.8% for 80-20MBO and MBO, respectively, and beyond this value, good agreement among detectors was seen. Our preliminary results indicate the potential utility of these pellets in QA for radiotherapy.

Optically Stimulated Luminescence Materials: Optically Stimulated Luminescence Phosphors: Principles, Applications, and Prospects (Laser Photonics Rev. 14(12)/2020)

Optically stimulated luminescence (OSL) materials enable energy storage and then energy conversion to light upon photostimulation, with applications spanning from radiation dosimetry, optical data storage and security, environmental monitoring, biomedicine, clinical diagnostic, to archaeology and geology. In article number 2000123, Yahong Jin, Yihua Hu, Shihe Yang, and co-authors give a comprehensive review on the fundamental principle, design, preparation, characterization, optimization, research progress, application, mechanism, and prospect of OSL materials. The focus is placed on the discussion and summarization of trap engineering, study methodologies, the challenges, and outlooks.

Optically stimulated luminescence of MgO:Na,Li phosphor prepared using solution combustion method

Abstract The purpose of this study is to synthesize magnesium oxide polycrystals doped with sodium and lithium (MgO:Na,Li) using Solution Combustion Synthesis (SCS) technique for developing a storage material with required Optically Stimulated Luminescence (OSL) properties. In this work, we investigated the dosimetric and luminescence characteristics of the synthesized MgO:Na,Li ceramic in pellet form. The phase identification and morphology of the samples were performed using x-ray diffraction (XRD) and scanning electron microscope (SEM) analysis. The radioluminescence (RL) emission of the obtained MgO:Na,Li pellet samples showed two different emissions bands that are dominant at ∼730 nm, and with a weak and broad emission between 300 and 590 nm. The samples characterized by a Thermoluminescence (TL) glow curve having dominant TL peaks at around 80, 155 and 315 °C at a heating rate of 5 °C/s. We carried out a step-annealing procedure to investigate the depth of the trapping centers associated with the OSL signal. The thermally affected OSL traps seems to be originated mostly from practically a single deconvoluted TL peak between 170 and 250 °C with intensity comparable to Al2O3:C when Hoya U-340 filter was used. The stability of the OSL signal was tested for shorth-term and long-term fading in dark. We determined that the total OSL area decayed around 15% after 5 weeks. We evaluated the kinetic parameters of the MgO:Na,Li using the computerized glow curve deconvolution (CGCD), Tm-Tstop method and extended initial rise method (IRM) for the TL traps, and isothermal annealing method for the OSL traps. We presented MgO:Na5%,Li5% as a workable OSL material sensitive to ionizing irradiation with suitable dosimetric properties.

Lanthanide-doped MgO: A case study on how to design new phosphors for dosimetry with tailored luminescent properties

In this work we systematically investigated undoped and lanthanide(Ln)-doped MgO with diverse dopant combinations, MgO:Ce,Ln and MgO:Tb,Ln, where Ln=Eu, Yb, Tm, Sm, Dy, Nd, as well as the same combinations with an additional 3 mol% Li dopant. We characterized the thermoluminescence (TL), optically stimulated luminescence (OSL), radioluminescence (RL), TL emission spectra and OSL emission spectra. Our investigation indicates that Ce3+ and Tb3+ act as recombination centers and their characteristic spectra are observed under thermal or optical stimulation. Conversely, TL measurements suggests that Sm3+, Tm3+ and Yb3+ probably act as electrons traps. The role of Li was investigated, since it was found to increase the RL, TL and OSL intensities in MgO. As part of the present investigation, we identified promising OSL materials sensitive to ionizing irradiation with distinct luminescent properties.

Design optimisation of C ion implantation of α-Al2O3 for medical dosimetry

The present work reports the fabrication and characterization of α–Al2O3:C, a highly sensitive low effective atomic number (Zeff = 10.7) OSL material for medical dosimetry, through a new approach of doping via implantation. In this study, a Single Crystalline α–Al2O3 (SCALO) and a Sapphire α–Al2O3 (SALO) are used and implanted with 100 keV of C+ at various fluences (mol%) from 2.5 × 1014 ions cm−2 (~0.04%) to 6.25 × 1015 ions cm−2 (~1%) and are pre-heated up to 220 °C. The structural, optical, morphological and luminescent studies of the Carbon doped α–Al2O3 (α–Al2O3:C) are carried out using X-ray diffraction, Ultraviolet-visible spectroscopy (UV–Vis), Photo-luminescence (PL), Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS), Optically Stimulated Luminescence (OSL), and Thermo-Luminescence (TL). The doping of ~1 mol% of C+ is found at an optimized doping level due to its high intensity of luminescence. This phenomenon is studied for heavy charged particle (HCP) dosimetry, which might prove effective for cancer treatment. It is found that α –ALO:C (both the single crystalline and the sapphire alumina) has the capability to measure large radiation doses (~kGy). This is attributed to the generation of stable defects after the incorporation of Carbon that results in a linear response with the dose and in extraordinary efficiency. Thus, this study confirms the development of α–Al2O3 by the novel approach of C+ implantation method and the findings result in an efficient medical radiation dosimeter.

Correction of quenching effect of a small size OSL dosimeter using Eu:BaFBr and Ce:CaF2

To accurately estimate an actual dose during radiotherapy treatment, dosimeters are required to be inserted into the affected region in a patient's body. Therefore, we are developing a small size dosimeter consisting of optical fibers and optically stimulated luminescence (OSL) elements. We fabricated two types of small size dosimeters using Eu:BaFBr and Ce:CaF2. We measured the Bragg peak of high energy carbon ions in a water equivalent material. OSL materials showed the quenching effect when irradiated by high linear energy transfer (LET) particles. The sensitivity of Eu:BaFBr and Ce:CaF2 monotonically decreased with different coefficients. The ratio of the signal intensity of these two OSL materials can uniquely determine the sensitivity of each OSL material. We corrected the quenching effect of the OSL dosimeters in the spread out Bragg peak with this relationship.

A new luminescent material based on CaB6O10:Pb to detect radiation

This work describes the synthesis of a new photostimulable phosphors based on Pb-doped CaB6O10, and presents an investigation on its luminescence and dosimetric properties. The crystalline phase was confirmed by X-ray diffraction. We performed radioluminescence (RL), thermoluminescence (TL) and optically stimulated luminescence (OSL) measurements to determine the material׳s luminescence sensitivity as a function of Pb concentration, dose response to ionizing radiation, as well as the luminescence emission spectra, thermal stability of the luminescence signal, and lifetime of the associated luminescence centers. The results shows that the material is highly sensitive to ionizing radiation, comparable or surpassing commercially available luminescence materials such LiF:Mg,Ti and Al2O3:C, with a dominant TL peak at ~200°C and an OSL signal that can be ~99% read within ~20s under current experimental conditions. The RL, TL and OSL signals are dominated by an emission band at ~320nm, probably associated with 3P1→1S0 transition of Pb2+. Although the optimum Pb concentration was 3mol% (nominal concentration used for synthesis), high sensitivity was observed for Pb concentrations >0.1mol%. The luminescence decays with a 0.55μs and a 5.1μs lifetime and the dose response was linear in the range investigated (~2mGy–1Gy). A signal fading of up to 50% within 8 days was observed, the majority of this fading taking place in the first 5h (40%) following irradiation. This study shall motivate further fundamental investigations on this material, which may lead to an alternative OSL material for dosimetry.

SU‐E‐T‐264: Preliminary Results On New Optically Stimulated Luminescent Materials for Proton Therapy Dosimetry

Purpose:The objective of this work is to test the premise that luminescence materials with less under‐response to proton beams can be identified by testing their dose response to low‐LET radiation. The goal is to develop new Optically Stimulated Luminescence (OSL) materials with improved response for proton therapy dosimetry.Methods:We first measured the dose response of new OSL materials, synthesized in our laboratory, to low‐LET radiation (beta rays from a 9 0Sr/9 0Y source) and selected two materials having different OSL saturation characteristics and good dosimetric properties, namely MgB4O7:Ce,Li and MgO:Li. Commercial Al2O3:C was also used for comparison. These materials were then irradiated at several depths along a pristine proton beam. The luminescence responses of the materials, relative to the entrance response, were compared with the depth dose profile measured by a multiple‐layer ion chamber.Results:The OSL signals of MgB4O7:Ce,Li and MgO:Li were characterized for signal stability, dose response, and response to a clinical proton beam. The materials were also compared with the commercial Al2O3:C. The signals from both MgB4O7:Ce,Li and MgO:Li were relatively stable after a one day delay following irradiation. The low‐LET dose response of the materials showed that, over the dose range investigated (up to ∼800 Gy), MgB4O7:Ce,Li did not saturate, whereas MgO:Li and Al2O3:C saturated at doses of ∼100 Gy. MgB4O7:Ce,Li showed less underresponse to proton beams than MgO:Li and Al2O3:C.Conclusion:In general the material with the highest saturation doses for low‐LET radiation (MgB4O7:Ce,Li) showed the least under‐response to proton beams, which suggests that it may be possible to develop better OSL materials for proton dosimetry if the dose response can be controlled during synthesis. Nevertheless, the degree in which the response to proton beams can be controlled remains to be determined.The research is funded by the Oklahoma Center for the Advancement of Science and Technology (OCAST), project number HR12‐055.

Energy absorption buildup factors, exposure buildup factors and Kerma for optically stimulated luminescence materials and their tissue equivalence for radiation dosimetry

Optically stimulated luminescence (OSL) materials are sensitive dosimetric materials used for precise and accurate dose measurement for low-energy ionizing radiation. Low dose measurement capability with improved sensitivity makes these dosimeters very useful for diagnostic imaging, personnel monitoring and environmental radiation dosimetry. Gamma ray energy absorption buildup factors and exposure build factors were computed for OSL materials using the five-parameter Geometric Progression (G-P) fitting method in the energy range 0.015–15MeV for penetration depths up to 40 mean free path. The computed energy absorption buildup factor and exposure buildup factor values were studied as a function of penetration depth and incident photon energy. Effective atomic numbers and Kerma relative to air of the selected OSL materials and tissue equivalence were computed and compared with that of water, PMMA and ICRU standard tissues. The buildup factors and kerma relative to air were found dependent upon effective atomic numbers. Buildup factors determined in the present work should be useful in radiation dosimetry, medical diagnostics and therapy, space dosimetry, accident dosimetry and personnel monitoring.

Investigations of MgO:Li,Gd thermally and optically stimulated luminescence

The purpose of this work is to investigate the thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of MgO:Li,Gd synthesized by solution combustion synthesis as a function of different synthesis parameters. In addition to TL and OSL, characterization techniques include x-ray diffraction (XRD) and radioluminescence (RL). We also investigated undoped and singly-doped samples for comparison. We show that MgO:Li,Gd may serve as the basis for a new OSL material with intensity comparable to commercial Al2O3:C and narrow emission at 315nm associated with Gd3+. Li co-doping has increased the OSL signal by several orders of magnitude when compared to MgO undoped or MgO:Gd. However, elimination of shallow trapping centers (associated with TL peaks <100–150°C) is necessary to reduce OSL signal fading at room temperature.

Development of prototype fiber optics dosimeter for remote radiation level measurements

Measurement of radiation levels in difficult-to-access and hazardous areas, such as hot cells, high active source storage areas, require refined and sensitive remote radiation level measurement techniques. Optical fiber dosimetry has been studied as an emerging method of monitoring radiation remotely and is suitable for use in confined environments that may be inaccessible using existing conventional electronic dosimeters or radiation survey meters. Being light weight and nonintrusive, optical fibers based dosimeters provide several advantages in the field of remote radiation dosimetry and in-vivo medical applications. A prototype fiber optic dosimetry system with extrinsic architecture is designed and developed using optically stimulated luminescence (OSL) technique at Radiological safety division, Indira Gandhi Centre for Atomic Research. The fiber optic dosimetry system uses OSL material like BaFBr: Eu to detect radiation and a bifurcated optical cable to illuminate the sensor with the suitable light source and also to guide the light from the sensor to the detector. Indigenously developed hardware is used for pulse processing and application software of the system is developed in Microsoft Visual Basic.Net. This paper depicts the characterization of the dosimetric material, development of hardware and software for the system and calibration of the system using standard source. The system uses Advantech APAX 5570 base controller with suitable modular add-on cards for data acquisition and controlling. Indigenously developed electronics is used for processing the pulses from the sensor attached to the tip of the bifurcated optical cable. The acquisition of the counts from the electronic circuit and illumination and bleaching time for the sensor pellet is controlled by application software developed in VB.Net. The system is calibrated by irradiating the pellet with different absorbed doses. The system explores the possibility of remote radiation monitoring using OSL technique in real time. The system is portable, simple to use and requires less user intervention to operate.

선량 판독용 OSL 측정장치의 개발

Design and performance test results of a newly developed optically stimulated luminescence (OSL) measurement system are presented in this paper. Generally, different types of optical filters are used in OSL reader system to minimize the interference of the stimulation light in the OSL signal. For optically stimulation of , we have arrived at an optimal combination of the filters, i.e., GG420 filter for filtering the stimulating light source, and a combined UG11 and BG39 filter at the detecting window (PMT). By using a high luminance blue LED (Luxeon V), sufficient luminous intensity could be obtained for optically stimulation. By using various control boards, the OSL reader device was successfully interfaced with a personal computer. A software was developed to deliver required commands to operate the OSL reader by using the LabView program (National Instruments, Inc.). In order to evaluate the reliability and the reproducibility of newly designed-OSL reader. Performance testing of the OSL reader was carried out for OSL efficiency, OSL decay curve and signal to noise ratio of the standard OSL material. It was found to be comparable with that of commercial Riso reader system.

Systematic development of new thermoluminescence and optically stimulated luminescence materials

This paper presents an overview of a systematic study to develop new thermoluminescence (TL) and optically stimulated luminescence (OSL) materials using solution combustion synthesis (SCS) for applications such as personal OSL dosimetry, 2D dose mapping, and temperature sensing. A discussion on the material requirements for these applications is included. We present X-ray diffraction (XRD) data on single phase materials obtained with SCS, as well as radioluminescence (RL), TL and OSL data of lanthanide-doped materials. The results demonstrate the possibility of producing TL and OSL materials with sensitivity similar to or approaching those of commercial TL and OSL materials used in dosimetry (e.g., LiF:Mg,Ti and Al2O3:C) using SCS. The results also show that the luminescence properties can be improved by Li co-doping and annealing. The presence of an atypical TL background and anomalous fading are discussed and deserve attention in future investigations. We hope that these preliminary results on the use of SCS for production of TL and OSL materials are helpful to guide future efforts towards the development of new luminescence materials for different applications.

Prediction of neutron-induced signals in OSL materials by track structure calculations

Track structure calculations have been performed in order to predict the neutron dose equivalent response of Al 2 O 3 :C optically stimulated luminescence (OSL) materials mixed with neutron converters. The results of the calculations were compared to measurements available in the literature. The calculations yield neutron responses which agree within 35% with the results of the measurements for grain diameters of 10 μm–20 μm, both for Al 2 O 3 :C mixed with 6 LiF and for Al 2 O 3 :C mixed with polyethylene. For increasing grain sizes of Al 2 O 3 :C material – 10 μm to 100 μm – the calculations predict a decrease of the neutron response by about a factor of three.