Dosimetric Material Research Articles

Study on the preservation effect of 60Co-γ ray irradiation on potatoes

To evaluate the effect of irradiation on the preservation of potatoes, fresh potatoes were selected as the irradiation objects, and irradiated with 60Co-γ radiation source for 0, 100, 200, 500 and 1000 Gy, respectively. During the irradiation, the well-packaged Y1.79Bi0.01Eu0.2MgTiO6 novel thermoluminescence dosimeter material was placed together with the potatoes at the same position. Then, the potatoes were stored in the same temperature and humidity environment, and the quality changes of the potatoes were observed. The Y1.79Bi0.01Eu0.2MgTiO6 material had good performance indicators, and was used to measure the irradiation dose of the potatoes. The experiment showed that irradiation could appropriately extend the storage time of potatoes, and gamma irradiation of about 1000 Gy could achieve the best preservation effect. The main pathogenic fungi that cause dry rot of potatoes were Fusarium solani and Fusarium oxysporum, and the appropriate dose of 60Co-γ irradiation could effectively inhibit the spread and growth of these fungi.

Impact of sample preparation temperature on Li and Ce co-doped MgB4O7 dosimetry performance: A plausible scenario for controlling defect clustering

MgB4O7 co-doped with Ce and Li has been recognized as a promising dosimetric material for spatially-resolved optically stimulated luminescence (OSL) measurements. Nevertheless, conflicting information exists in the literature regarding its dosimetric characteristics. These include discrepancies in fading, the proportion of shallow traps, the range of linear dose response, and a notable absence of direct sensitivity comparisons. These discrepancies are likely attributed to variations in the synthesis methods utilized to produce this material. As part of our research initiative aiming at elucidating the influence of synthesis on the luminescence properties, we are examining in this contribution a single parameter – specifically, the sample preparation temperature – and assessing its impact on the luminescence properties. For the first time, we identified a correlation between the width of the thermoluminescence (TL) glow curves, the TL, optically stimulated luminescence (OSL), and radioluminescence (RL) intensities, as well as the fading characteristics over time and annealing temperature. We show that annealing at higher temperature leads to narrowing of the main TL peak (c.a. 240 °C at 5 °C/s heating rate) compared with samples prepared at lower temperatures, which in turn leads to a decrease in the integrated TL intensity of that peak. Despite exhibiting lower intensity, samples prepared at temperatures above 800 °C show less than 10 % TL/OSL fading over 60 days. Our measurements suggest an involvement of clustered defects for the samples prepared at 600 °C, with a shift towards a scenario of delocalized transitions in samples prepared at higher temperatures.

Effect of synthesis conditions on the thermoluminescence of Li9Mg3[PO4]4F3 fluorophosphate

The Li9Mg3[PO4]4F3 fluorophosphate, which is considered as a promising dosimetric material, was prepared by the conventional solid-phase and microwave-assisted methods. The dosimetric properties of the obtained materials were examined and compared. The results revealed that the microwave-assisted synthesis leads to a fourfold enhancement of the thermoluminescence. Analysis of structural data showed that prolonged contact with the atmosphere can cause the loss of fluorine, resulting in the deterioration of material properties. This effect is also evidenced by the increase in the ESR signal, which is associated with a larger number of antisite defects, for the fluorophosphate obtained by the microwave-assisted method. The additional synthesis of Li9Mg3[PO4]4F3 with an excess of LiF allowed us to suppress the fluorine losses, thereby leading to an additional manifold increase of the thermoluminescence.

Radiophotoluminescence response of LiF:Mg,Ti pellets irradiated with clinical proton beams in the 70–200 MeV energy range

Lithium fluoride doped with Mg and Ti (LiF:Mg,Ti) has been used for several decades as thermoluminescent dosimeter material, but recently also its radiophotoluminescence has been investigated for applications in dosimetry. In this work, LiF:Mg,Ti pellets (TLD-100) were irradiated in a water phantom at CNAO (Pavia, Italy) with therapeutic proton beams at five energies from 70 to 200 MeV in the dose range from 2 to 20 Gy. After irradiation, their visible radiophotoluminescence spectra were measured in controlled conditions and the spectrally-integrated red emission response of radiation-induced color centers has been investigated. The radiophotoluminescence signal, excited by a 445 nm continuous wave laser, was integrated within a 50 nm-wide band around the emission peak of the F2 color centers, located around 670 nm in LiF. The spectrally-integrated signal of the samples irradiated at the energy of 147.7 MeV exhibited a linear dependence with dose. Moreover, this radiophotoluminescence response appears independent from Linear Energy Transfer in the range from 0.8 to 1.6 keV/μm in all the samples irradiated at the dose of 5 Gy. Such independence was found up to 10.3 keV/μm in samples irradiated within two spread out Bragg peaks made of 36 energy components in the entire investigated proton energy range. The radiophotoluminescence response of the TLD-100 pellets was compared to that of nominally-pure LiF crystals irradiated in the same conditions, which show a similar behavior. The results are encouraging for the exploitation of TLD-100 pellets as passive solid-state radiophotoluminescent dosimeters for proton therapy.

OSL and PTOSL of dosimetric materials: Observation of the luminescence after exposure to 90Sr+90Y source and LEDs in ultraviolet range

The study of luminescence phenomena by crystal-based radiation detectors is suitable for radiation dosimetry, once the light emitted by them enables the quantification of their deposited radiation energy. The light emission can be promoted when a material is illuminated with a certain wavelength and time interval, as in the optically stimulated luminescence (OSL) and photo-transferred OSL (PTOSL) processes. The objective of this work is to evaluate the OSL and PTOSL responses of commercial dosimeters (LiF:Mg,Ti, CaF2:Dy, CaF2:Mn and CaSO4:Dy) in order to study their luminescence and the possibility of use in radiation dosimetry with the PTOSL technique. OSL and PTOSL responses of LiF:Mg,Ti, CaF2:Dy, CaF2:Mn and CaSO4:Dy dosimeters, commercially sold as TLD-100, TLD-200, TLD-400 e TLD-900, respectively, by Thermo Fischer Scientific, were studied. The samples were irradiated with the 90Sr+90Y source of the TL/OSL reader system Risø, and the measurements were taken using the same system and blue LEDs. For the PTOSL signal, the dosimeters were irradiated, thermally treated and illuminated with LEDs with wavelengths between 265 nm and 420 nm. The most intense OSL signal occurred for TLD-100. Comparing the OSL and PTOSL results, it is possible to observe clearly the photo-transferred effect for TLD-100. For TLD-200 and TLD-400, no effects were noted. In the case of TLD-900, it presented a PTOSL signal in a small-scale when analyzing the curve integral.

Towards liquid EPR dosimetry using nitroxides in aqueous solution.

Objective. Water-equivalent dosimeters are desirable for dosimetry in radiotherapy. The present work investigates basic characteristics of novel aqueous detector materials and presents a signal loss approach for electron paramagnetic resonance (EPR) dosimetry.Approach. The proposed principle is based on the radiation dose dependent annihilation of EPR active nitroxides (NO·) in aqueous solutions. Stable nitroxide radicals (3-Maleimido-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (MmP), 3-Carbamoyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (CmP)) in aqueous solutions containing dimethyl sulfoxide (DMSO) as an additive were filled in glass capillaries for irradiation and EPR readout. Radiation doses ranging from 1 to 64 Gy were applied with a clinical 6 MV flattening filter free photon beam. EPR readout was then performed with a X-band benchtop spectrometer. The dose response, temporal stability and reproducibility of the samples' EPR signal amplitudes as well as the influence of the nitroxide concentration between 10 and 160μM on the absolute signal loss were investigated using MmP. CmP was used to examine the dependence of the dose response on DMSO concentration between 0 and 10 vol%. An indirect effect model was fitted to the experimental data assuming irradiation induced radical reactions as the underlying mechanism.Main results. For an initial MmP concentration of 20μM, absolute EPR signal loss is linear up to a dose of 16 Gy with a yield G(-NO·) of approximately 0.4μmol J-1. Within five weeks upon sample irradiation to doses between 0 and 32 Gy relative EPR signal fluctuations were on average (126 readouts) below 1% (1σ). For c(MmP) ≥ 20μM, absolute signal loss is only weakly dependent on c(MmP), whereas it increases strongly with increasing c(DMSO) in the range 0-5 vol%. An indirect effect model is applicable to describe the reaction mechanism resulting in the observed dose response curve.Significance. Liquids consisting of nitroxides in aqueous solution and small amounts of DMSO (2 vol%) show promising basic characteristics for application as water-equivalent EPR dosimeter materials in radiotherapy. The EPR signal loss is based on an indirect effect mediated by diffusing radicals originating from the radiolysis of the water/DMSO mixture.

Effects of UVC irradiation on polystyrene for healthcare packaging: Study by FTIR and Raman spectroscopy with thermoluminescence

The interaction between ultraviolet C radiation (UVC) and polystyrene (PS) materials has been investigated, particularly in post-packaging irradiation processes for healthcare applications. Effective UVC penetration through PS materials, regardless of their thickness (0.16 and 0.40 mm) has been observed. However, the penetration effectiveness could be affected by the thickness of the PS material. Achieving optimal post-packaging UVC treatment requires a thorough evaluation of chemical composition and material thickness, especially in pharmaceutical and medical packaging industries.Preliminary results reveal minimal degradation in UVC-irradiated PS packaging samples, as supported by FTIR and Raman spectroscopy characterization. Minor variations could be attributed to intrinsic PS materials properties and/or their respective background, rather than the influence of UVC radiation. Consequently, PS materials exhibit resilience under the experimental conditions following UVC irradiation treatment. Furthermore, a comprehensive analysis of thermoluminescence (TL) emissions evaluates several commercial dosimeter materials for UVC radiation detection. The TLD-100 and TLD-200 dosimeters show potential as UVC detectors, displaying distinct responses linked to the non-ionizing component of UVC radiation at 310 °C and in the range of 150–250 °C, respectively. However, the TLD-400 and GR-200 dosimeters are not suitable for UVC detection due to their spread TL emissions considering intensity and curve shape.This UVC-TL analysis consistently detects radiation in the proposed commercial dosimeter materials one-hour post-exposure, providing assurance that healthcare materials have been irradiated. Such analysis enhances reliability during extended UVC exposures, offering valuable insights for industries employing UVC-irradiated materials, particularly in healthcare applications.

Correlation between thermoluminescence and optically stimulated luminescence signal in BeO

Beryllium Oxide (BeO) is a promising dosimetric material that is rapidly becoming an essential instrument in Optically Stimulated Luminescence (OSL) dosimetry applications. Despite the potential of BeO as a luminescence dosimeter, gaps remain in understanding how its Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) signals are connected. Our study aimed at examining Residual Thermoluminescence (R-TL) glow curves after various bleaching times to find an association between TL traps and OSL components across a wide range of doses, at 40 mGy and from 10 to 100 Gy. OSL decay curves and intensities of R-TL glow curves were fitted to either pure exponential decay functions or to stretched exponential decay functions, due to optical attenuation, to determine the OSL components and the bleaching decay rates of each TL peak, respectively. A good correlation between the decay rates of the OSL components and bleaching decay rates of each TL peak for both high and low-dose irradiations was found only for the model functions considering optical attenuation in the material. Taken together, this qualitative method helped to identify various traps, and results revealed a more consistent luminescence mechanism between TL and OSL signals than was previously assumed. Further support for the correlation between TL and OSL was derived from thermal stability studies of the OSL signal and from the dose response of the TL peaks and the OSL signal after different thermal pretreatments. Different bleaching models were discussed to define the appropriate one for BeO. These results may enhance our understanding of BeO as a dosimeter.

3D2: Three Decades of Three-Dimensional Dosimetry

The development of three-dimensional (3D) dosimetry was motivated by its promise as an effective methodology for the validation of the complex dose distributions achieved by modern techniques such as Intensity Modulated and Volumetric Arc Radiation Therapy. 3D techniques were first proposed in the 1980s when clinics were just starting to move from two-dimensional contour plan based delivery to more conformal techniques. Advances in dosimeter materials, readout systems, and workflow and software systems for the registration and analysis of the volumetric dose data have made 3D dosimetry more attainable, yet to date it has not made major inroads into the clinic. This keynote address will highlight some 3D dosimetry developments over the years, many of which were first revealed through the past twelve International Conferences on 3D and Advanced Radiation Dosimetry (IC3Ddose). These conferences resulted in the publication of more than 130 didactic review articles and over 650 proffered research papers, the majority openly available on the internet (years before the current drive to publishing in open access journals). In this joint keynote address to the IC3Ddose community (at the end of its conference) and to attendees of the Canadian Organization of Medical Physicists annual scientific meeting (at its start), I will briefly review the radiation sensitive materials used for 3D dosimetry, the imaging systems required to read out the volumetric dose information, the workflows and systems required for efficient analysis, and the protocols required for reproducible dosimetry, and how the dosimetry has come into the clinic. The address includes some personal reflections of the motivational and practical changes in 3D dosimetry over time. And as we are all meeting in person for the first time in over two years, the address will end with some observations on the importance of conferences for the exchange of ideas and associated debate necessary for scientific advancement.

Charting the development of optical CT and allied methods for 3-D radiation dosimetry: 2022 update - mapping the global research community

To recognise the many and varied contributions from groups around the world over more than 25 years of research into 3-D radiation dosimetry using optical imaging (primarily optical computed tomography), a systematic review has been conducted with the aim of charting the development of this field. Some 493 publications matched the criteria of the review, and these have been coded with information relating to the category of research, the type of dosimeter material used and the geographical location where the research was conducted. The results of the analysis demonstrate a steady growth in the number of academic groups involved, from 4 at the first DOSGEL meeting in 1999 to over 30 in 2016. The important role played by the DOSGEL and IC3Ddose conference series is demonstrated by the marked biennial trend in publications. The division of publications between categories was 36% materials development, 34% scanner technology, 24% applications, 5% review and 1% teaching. The most common application areas were brachytherapy, proton/particle therapy and IMRT/VMAT. Prior to the introduction of PRESAGE® in 2003, polymer gels were the most popular material, whilst radiochromic dosimeters have dominated in recent years. These and other trends are discussed on the basis of the data presented. A brief discussion of the future of the field, including some personal opinions, ends this brief review.

Surface mount multilayer ceramic capacitors as optically stimulated luminescent dosimeters

The choice of dosimetric materials for precise retrospective dose assessment in case of any emergencies is very challenging. Since few decades, electronic components like ceramic resistors, inductors, IC chips, surface mount resistors and inductors have been proven to be suitable candidates for dose estimation using thermoluminesce (TL)/optically stimulated luminescence (OSL) techniques. In this work, OSL technique is applied to study dosimetric properties of surface mount multilayer ceramic capacitors (SM MLCC) available in commonly used instruments like printer, computer mouse, USB flash drive and personal gadgets like mobile phone etc. To understand the OSL process involved, the elemental composition and crystallinity of the SM MLCCs were analyzed using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) techniques. It is found that the main constituent is barium titanate with aluminium silicate as major impurity along with some trace elements and is responsible for the origin of the radiation induced OSL signal. Some important dosimetric characteristics like OSL sensitivity, repeatability, OSL dose response, and OSL signal stability upon storage were studied. The stimulation time was optimized as 50 s and used for all OSL measurements. The dose response was found to be linear from 500 mGy to 15 Gy and simply increased (up to 40 Gy). Fading analysis showed that the OSL signal decreases by ∼ 25 % in 1 day, ∼ 50 % in 4 days, and remained stable after that at least up to 8 days. The dose was recovered using single aliquot regenerative-dose (SAR) technique with very good accuracy. These results of dosimetric studies and validation study suggest that surface mount multilayer ceramic capacitors have potential use as retrospective dosimeters.

Investigation of the dosimetric properties of potassium hydrogen tartrate using EPR

Use of electron paramagnetic resonance (EPR) in radiation dosimetry means more accurate and reliable evaluation of radiation doses. The search for new dosimeter material is continuing to overcome some drawbacks of available ones. In current work potassium hydrogen tartrate is presented as a new EPR dosimeter material where its radiation dose dependency, effects of the change in microwave power and modulation amplitude on the peak-to-peak intensity were studied. Response of potassium hydrogen tartrate to gamma radiation was studied in two ranges: the first starts at 1.4 Gy and ends at 84.2 Gy, and the second from 42.1 Gy to 2415.6 Gy. Calibration curves were obtained with associated combined uncertainties range from 0.5% and up to 27.4% for the first peak and from 0.5% up to 10.2%, for the second peak. Calibration curves were plotted and compared to alanine. Time dependence of the EPR spectra of the radiation-induced radicals was monitored over short term (10 h) and long-term (28 days) following irradiation.

The energy dependence of BaSO4: Eu nanophosphors for thermoluminescence dosimetry of orthovoltage X-rays and low energy protons

Accurate dosimetry of ionizing radiation requires careful consideration of the absorption properties of the dosimeter material in question. The energy dependence of a dosimeter signifies the variation in dosimeter signal per absorbed dose to water with radiation type and energy. The nanophosphor BaSO4: Eu is a radiosensitive material for thermoluminescence (TL) dosimetry. However, the energy dependence of the material for orthovoltage X-rays and low energy protons has not previously been investigated, which is the purpose of the current work. We irradiated BaSO4 doped with 0.5 mol% of europium with 100, 160 and 225 kV X-rays and 2 and 9 MeV protons. Co-60 γ-rays were used for reference irradiation. Absolute dose-to-water dosimetry was ensured with an ion chamber. Delivered calibration doses ranged from 0.01 to about 2 Gy. TL output was measured at a heating rate of 5 K/s, where the maximum intensity of the dominant glow peak at about 212 °C defined the dosimeter signal. The signal was found to increase linearly with absorbed dose for both radiation types and all energies. The measured energy response, defined as the ratio of the TL calibration slope at a given radiation type and energy to that following Co-60 γ-irradiation, varied between 47 and 62 for X-rays and between 0.41 and 0.61 for protons. Theoretical modelling of the energy response and proton detector efficiency gave similar trends. The findings show that BaSO4 is an energy-dependent material, especially for X-rays, but may still prove valuable for accurate dose determination if the dosimeter is calibrated in the user beam.

Deciphering the Role of Gamma Ray Induced Radicals in the Thermoluminescence Process of a Neutral to Cool Daylight Emitting Sr1–xB4O7–Dyx Phosphor through Electron Paramagnetic Resonance (EPR) Spectroscopy

A number of researchers have reported on the thermoluminescence (TSL) properties of many borates activated with rare earths and transition metal ions. However, there are not many reports that pinpoint the role and chemical nature of the gamma induced radicals. Further, there are even fewer reports highlighting the multifunctional characteristics of a single TSL phosphor. In this work, we showcase SrB4O7 doped with Dy3+ for the dual role of white light emitting as well as a TSL dosimetric material. We did the PL/TSL/EPR (electron paramagnetic resonance) correlation studies in order to identify the active luminescent centers, the trap parameters and the chemical nature of the radicals responsible for the phenomena. By doing a systematic study on a series of Dy3+ (1–10 mol %) doped samples, we optimized the composition. Colorimetric studies on the optimized sample revealed that it had intense near white light emission with 38.1% color purity when excited by UV-C light (247 nm). The same sample also showed a linear gamma dose response up to 1600 Gy (J/kg). A detailed EPR investigation confirmed the role of a borate based radical in the observed TSL process. We believe that the material can be a good candidate for real life application as a multifunctional material.

Application of Amino Acids for High-Dosage Measurements with Electron Paramagnetic Resonance Spectroscopy.

A comparative investigation of amino acids (proline, cysteine, and alanine) as dosimetric materials using electron paramagnetic resonance (EPR) spectroscopy in the absorbed dosage range of 1-25 kGy is presented. There were no signals in the EPR spectra of the samples before irradiation. After irradiation, the complex spectra were recorded. These results showed that the investigated amino acids were sensitive to radiation. In the EPR spectrum of cysteine after irradiation, RS• radicals dominated. The effects of the microwave power on the saturation of the EPR signals showed the presence of at least three different types of free radicals in proline. It was also found out that the DL-proline and cysteine had stable free radicals after irradiation and represented a linear dosage response up to 10 kGy. On the other hand, the amino acid alanine has been accepted by the International Atomic Energy Agency as a transfer standard dosimetry system. In view of this, the obtained results of the proline and cysteine studies have been compared with those of the alanine studies. The results showed that the amino acids proline and cysteine could be used as alternative dosimetric materials in lieu of alanine in a dosage range of 1-10 kGy of an absorbed dose of γ-rays using EPR spectroscopy. Regarding the radiation sensitivity, the following order of decreased dosage responses was determined: alanine > DL-proline > cysteine > L-proline.

Dosimetric and spectroscopic study of LiMgPO4 doped with Tm3+ and Er3.

Olivine-type phosphate LiMgPO4 doped with rare earth elements is considered a novel dosimetric material with excellent performance that is suitable for thermoluminescence (TL) and optically stimulated luminescence (OSL) measurements. Novel LiMgPO4:Tm,Er samples were synthesized by a high-temperature solid-state reaction method. A detailed study of the TL and OSL of the samples was performed using β-ray irradiation and X-ray-excited optical luminescence (XEOL) spectroscopy. Density functional theory (DFT) calculations were performed to predict the preferential positions of thulium and erbium, and photoluminescence (PL) spectra and TL 3D spectra were analyzed. The DFT calculation results show that Mg is preferentially replaced by Tm/Er in the LiMgPO4 system. The PL/TL3D/XEOL spectra of the samples are dominated by the characteristic luminescence of Tm3+, and the OSL decay curve of photoluminescence has fast and slow decay components with decay constants of 5 s and 42 s, respectively. The TL and XEOL results show that LiMgPO4:Tm,Er has strong emission signals under different types of radiation rays. The PL/TL3D/XEOL spectral results show that Er3+ has no radiative excitation, but Tm3+ has strong luminescence, such that the sample still emits strong TL and PL signals. Two TL emission peaks occur at approximately 120 °C and 300 °C, where the high-temperature peak is significantly more intense than the low-temperature peak, promoting the stability of the TL and OSL signals of the samples. The TL curve consists of 6 general TL dynamic peaks. The nonlinear parameters of the TL dose response are R = 0.08 and D 0 = 479 Gy, and the OSL dose response is linear in the range of 0.2-1000 Gy. The TL and OSL signals of the LiMgPO4:Tm,Er phosphor have good repeatability. Therefore, the LiMgPO4:Tm,Er phosphor can be used for radiation dose measurement.

Design of an Instrumented Fuel Rod for Intra-pin Neutron Flux Measurements in the CROCUS Experimental Reactor

In response to the need for validating high-fidelity deterministic neutronics solvers capable of pin-resolved neutron flux distributions, an instrumented fuel rod was designed for the experimental reactor CROCUS, operated by EPFL’s Laboratory for Reactor Physics and Systems Behaviour. This rod aims at obtaining intra-pin data using activation dosimetry techniques. Placed in the outer region of the reactor core, the rod utilizes spaces between four metal uranium cigars (25 cm each) to house various disk dosimeters, targeting different neutron energy ranges and allowing retrieval of radial and azimuthal intra-pin neutron reaction rates. A design of experiment (DOE) study, aided by Serpent2 Monte Carlo calculations, facilitated the selection of dosimeter material and rod design, ensuring detection of within-pin neutron flux v ariations w hile adhering to mechanical and regulatory constraints. Azimuthal divisions of activation dosimeters were irradiated at the core center and subsequently subjected to activity determination using an HPGe gamma spectrometer. The objectives were met, detecting expected azimuthal variations within dosimeters and confirming uncertainties on reconstructed activity to be smaller than the amplitude of the observed variations. A permit from the Swiss nuclear regulatory authority ENSI-IFSN was obtained, allowing installation and usage of the instrumented fuel rod in CROCUS, known as the NECTAR experiments.

Study of thermoluminescence, photoluminescence and dosimetry for the YAGG:Ce (Y2.96Al3.4Ga1.6O12:0.04Ce) phosphor

The comprehensive effect of ionizing radiation should be considered in the use and or analysis of certain electronic equipment. Fluorescent powders are widely used in electronic equipment, so they are attempted to be used as thermoluminescence (TL) dosimeter directly. Green YAGG:Ce phosphors were prepared by a high-temperature solid-state reaction method. The TL glow curves, TL dose response, TL three-dimensional (3D) spectra (80 K–800 K) and photoluminescence spectra for the phosphors were measured. The measurement results show that the luminescence peak temperature for the sample occurs at approximately 458 K and the luminescence peak temperatures in the TL 3D spectra are located at 130 K, 240 K and 458 K; there are four kinds of activation energies of traps in the material; the TL response of each component for the YAGG:Ce phosphor shows good linearity and the detection sensitivity of the phosphor is estimated to be less than 2 mGy. TL 3D spectra and PL spectra show that the luminescence from the phosphors arises from the 2D3/2 → 2F5/2,7/2 transition of Ce ions, and the TL 3D spectra at 130 K, 240 K and 458 K are almost the same, which proves that the temperature can hardly change the relative probability of the 2D3/2 → 2F5/2,7/2 transitions. The results show that YAGG:Ce could be used as dosimeter material.

Thermally stimulated luminescence properties of transparent ceramics for personal dosimetry

Transparent ceramics have attracted attention as a new optical material that can replace glasses and single crystals. In this study, we investigated the application of transparent ceramics as dosimeter materials. Specifically, thermally stimulated luminescence (TSL) properties of MgO, Al2O3, and CaF2: Mn transparent ceramics were evaluated in comparison with those of single crystals and opaque ceramics. As a result, transparent ceramics of three chemical compositions exhibited the highest TSL intensity.

Radiation Response Properties of Tb-Doped MgGa2O4 Single Crystals

Tb-doped MgGa2O4 single crystals (0.3, 1, 3, and 5%) were synthesized by the floating zone method. The synthesized crystals had a single phase of MgGa2O4 confirmed by X-ray diffraction and high transparency in the visible wavelength. Tb3+ acted as a luminescence center in both photoluminescence (PL) and thermally stimulated luminescence (TSL) processes. In the TSL dose response functions, the minimum detectable dose of the crystals was 0.01 mGy, which was comparable with some commercial dosimetric materials. In the X-ray imaging test taken based on TSL, the spatial resolution of the 1% Tb-doped crystal was estimated to be 8.90 LP/mm (56.2 μm).