Ag-doped Phosphate Glass Research Articles

Single-pulse three-dimensional parallel recording in glass using a feedback system.

High-quality three-dimensional computer-generated holograms (3D-CGHs) are crucial for programmable 3D femtosecond laser parallel recording (3D-FLPR). In this study, we introduced an innovative feedback approach for the rapid optimization of 3D-CGHs by incorporating the superposition of the calculated lens phases (CLPs) onto the 3D-CGHs within a feedback system. This feedback system, governed by coordinated control of a spatial light modulator (SLM) and a camera, served to avoid the poor quality of the ordinary CGH system. As a result, we successfully demonstrated coaxial 3D-FLPR in Ag-doped phosphate glass solely using a single fs laser pulse. Additionally, we regulated the energy distribution of the generated 3D multi-focus (3D-MF) to compensate the laser energy losses inside the glass. The presented single-pulse 3D parallel recording indicated the significant advancement facilitated by our method, particularly in enhancing the writing efficiency of optical storage.

X-ray storage tracks characteristics for Ag-doped phosphate glass based on radio-photoluminescence

Ag-doped phosphate glass (Ag-PG) is an excellent X-ray image storage material applied for recording X-ray tracks. In this work, we used Geant4 software to simulate the energy deposition attenuation and 2D/3D storage tracks characteristics of Ag-PG. The influence of the secondary particles generated by the interaction between X-rays and Ag-PG was analyzed. The storage cutoff depth of Ag-PG was verified at the Shanghai Synchrotron Radiation Facility (SSRF). The results show that the optical transmittance is slightly decreased after X-ray irradiation. The cutoff depth is only 200 μm for complete absorption, when the X-ray energy is 5 keV. The deposited energy is attenuated by 19.8% at the depth of 900 μm, when the X-ray energy is 30 keV. The distribution of deposited energy is primarily influenced by the attenuation of secondary electrons generated by the interaction between X-rays and Ag-PG. Furthermore, the 2D/3D models show that the storage depth is not significantly affected by different doses at the same X-ray energy. The low diffusion of the tracks spread plays a crucial role in achieving high spatial resolution. The storage cutoff depth in Ag-PG is approximately 10 mm at 20 keV. This has been successfully verified by SSRF, and it holds great significance for high-resolution imaging and quantitative storage of X-ray images in Ag-PG.

Storage and encryption of submicron spatial resolution X-ray images based on Ag-doped phosphate glass

The ultrastable encrypted storage of X-ray image with quantitative and ultrahigh-spatial resolution are crucial for a wide range of applications in radiation imaging, and it can be achieved by using the radio-photoluminescence (RPL) material, Ag-doped phosphate glass (Ag-PG), which was fabricated via the melt-quenching method. Under X-ray irradiation, Ag-PG produces a luminescence center, obvious 650 nm emission peak, which can be repeatedly excited by ultraviolet light without intensity attenuation. Quantitative X-ray image storage was realized based on the linear relationship between RPL intensity and X-ray irradiation time. X-ray image with a submicron spatial resolution of 0.7 µm was achieved, which could be stably stored without attenuation for more than 300 days. This submicron level X-ray image can be written into the Ag-PG as an encrypted information, and can only be visualized by an ultraviolet light. Additionally, heat treatment (400 °C for 2 h) could eliminate the influence of X-ray radiation on the Ag-PG, and restore the state of the Ag-PG before X-ray irradiation, which allows the recyclability and reusability of the Ag-PG. This research is of great significance for promoting the encrypted storage of X-ray images based on Ag-PG or other RPL materials.

Recent advances in radiophotoluminescence materials for luminescence dosimetry

Radiophotoluminescence (RPL) is a phenomenon in which a luminescence centre is formed in a medium upon interaction with ionizing radiation. The RPL is observed by a conventional photoluminescence (PL) technique, and the PL intensity is proportional to the dose. With the latter feature, the RPL has found successful applications in personnel and environmental dosimetry. However, the conventional materials considered for radiation measurements may be limited to Ag-doped phosphate glass, LiF, and Al2O3:C,Mg. The recent research works, however, have found a number of additional RPL materials for luminescence dosimetry. The aim of the present paper is to review the series of newly reported RPL materials and potential applications in dosimetry.

RPL properties of samarium-doped CaSO4

Radiophotoluminescence (RPL) properties of Sm-doped CaSO4 for radiation dosimetry applications are reported. The samples with varying Sm concentrations are prepared via the solid-state reaction process. The as-prepared samples show photoluminescence due to typical 4f–f transitions of Sm3+ whereas, after X-ray irradiation, additional emission features appear with a broad band peaking at 630 nm as well as a set of multiple sharp lines across 680–820 nm, which are attributed to the 5d–4f and 4f–4f transitions of Sm2+, respectively. Therefore, the RPL in the present material system relies on the generation of Sm2+ centers. The sensitivity is about 3 times lower than that of Ag-doped phosphate glass, but no fading and build-up of signal are evident even immediately after the irradiation. The signal is reversible by heat-treatment at 500 °C, and is reproducible even after the thermal erasure, especially when the differential signal between pre- and post-irradiation is taken into account.

Elucidation of electron and hole transfer at high temperature in Ag-doped Na and Al phosphate glasses

Ag-doped phosphate glasses are used in radiophotoluminescence (RPL) dosimeters. Ag0, Ag2+ and Ag2 + act as luminescence centers of RPL in the glass, whereas they disappear when annealed. To understand the reason for the RPL disappearance phenomenon, thermoluminescence (TL) glow curves, RPL temperature dependence electron spin resonance spectra were measured for the self-made Na and Al phosphate glass (Na–Al) and Ag-doped Na–Al made by Chiyoda Technol (FD-7). It is shown conclusively that in FD-7, electrons trapped at Ag2 + recombine with a part of holes trapped at hole trapping sites other than PO4 3− tetrahedra at 350–400 K, while electrons trapped at Ag2 + recombine with holes trapped at Ag2+ at 400–500 K. Subsequently, holes trapped at Ag2+ recombine with electrons trapped at electron trapping sites other than Ag2 + to induce TL at 520–650 K.

Ag-doped phosphate glass with high weathering resistance for RPL dosimeter

Ag-doped phosphate glass employed in the commercial dosimeter named FD-7 is used globally as one of the most reliable dosimeter materials. The luminescence phenomenon is well known as radiophotoluminescence (RPL). In this work, a new RPL glass material was developed for dosimeters that are used under high humidity conditions. The glass material that contains Ag2O as an activation center was produced by the melt-quenching method. The radiation properties and the optimal amount of Ag2O concentration required for achieving the best performance of the glass were evaluated using the RPL read-out system employing the photon counting method. On exposure to UV laser light radiation, the new RPL glass developed in this work emitted light of an approximate wavelength of 650 nm after radiation exposure, and the RPL intensity was proportional to the exposed dose. In addition, the glass material exhibited high reusability owing to the repeated operation of irradiation and reset. On conducting the weathering resistance test for a long duration, it was found that the new RPL glass exhibited the same RPL intensity and appearance as its initial values.

Evaluation of quantum yields and thermally stimulated luminescence glow curves of Ag-doped phosphate glasses

The aim of this research is to evaluate quantum yield (QY) values in radiophotoluminescence (RPL) centers and thermally stimulated luminescence (TSL) properties of the Ag-doped phosphate glass. After X-ray irradiation to the Ag-doped phosphate glass, a luminescence center of Ag2+ newly appeared at 650 nm of which QY value was 17.8% when the irradiation dose was 10 Gy. It indicates a monotonic increase with irradiation dose from 0.3 to 30 Gy as the RPL response. On the other hand, the QY value of an original luminescence center of Ag+ decreased from 3.5% to 2.0% by irradiation. The TSL glow curve before preheating consists of two peaks at 80 °C and 350 °C and the initial rise method derived activation energies of 0.48 and 0.93 eV, respectively.

Hole transfer in Ag-doped phosphate glasses having different cations elucidated by measuring variation of electron spin resonance spectra and photoluminescence spectra over time

Ag-doped phosphate glasses are used in radiophotoluminescence (RPL) dosimeters. According to previous papers, Ag0 and Ag2+ emit blue and orange RPL, respectively. However, transfer process of holes to Ag+ from PO43− tetrahedra via heating or time passing is not understood completely. In this study, we aimed to elucidate the cation dependence on the hole-transfer process. To achieve this purpose, we measured variations in electron spin resonance (ESR) and RPL spectra over time in NaPO3 and Ag-doped phosphate glasses with Na (Na/Ag), Na and Al (Na–Al/Ag), Li (Li/Ag), Cs (Cs/Ag), and Rb (Rb/Ag). Based on variations of the ESR signal intensity of holes trapped at PO43− and the RPL intensity, the transfer of holes to Ag+ occurred faster than the recombination of electrons and holes in Na/Ag, Cs/Ag, and Rb/Ag. In Na–Al/Ag, the transfer of holes to Ag+from PO43− and recombination of electrons and holes was completed in nearly the same amount of time. Hole transfer to Ag+occurred faster in the following order: Na/Ag > Cs/Ag > Rb/Ag > Na–Al/Ag > Li/Ag. Electron and hole recombination was completed faster in the following order: Na/Ag > Na–Al/Ag > Li/Ag > Cs/Ag > Rb/Ag. In addition, holes did not transfer back to PO43− from Ag+ during the Ag2+ reduction reaction.

High-dose dosimetry with Ag-doped phosphate glass: Applicability test with different techniques

Ag-doped phosphate glass from Chiyoda Technol Corp. was tested as a potential high-dose dosimeter. Several tens of glass samples were irradiated to different doses in the range 0–300 kGy and measured using radiophotoluminescence (RPL), optical absorption (OA), thermoluminescence (TL) and electron paramagnetic resonance (EPR) techniques. While RPL and TL signals from such glass saturated at the doses of about 1 kGy, OA and EPR (associated with Ag2+ centers) responses demonstrated a monotonic increase with dose up to the maximum tested dose 300 kGy. Fading of the Ag2+-related EPR signal was about 7% at 4 months and about 10% at 10 months after irradiation; no change was observed for OA measured one month after irradiation. It is concluded that with proper calibration, Ag-doped glass may be used for dose assessment in high-dose applications.

Build-up of radiophotoluminescence (RPL) in Ag-doped phosphate glass in real-time both during and after exposure to ionizing radiation: A proposed model

The build-up of radiophotoluminescence (RPL) from Ag-doped alkali-phosphate glass (from Chiyoda Technol Corporation, Japan) was measured both during and immediately following irradiation. The post-irradiation build-up curve was measured at several different temperatures and could be described by the sum of two exponential functions of time. The two processes are thermally activated, with activation energies of 0.45 eV and 0.17 eV, and their relative contributions were observed to behave in opposite senses as the temperature increases. Thermal quenching of the RPL signal with increasing temperature was also observed. The real-time RPL signal during irradiation could be described by the convolution of an intrinsic growth function and the build-up curve. A model is proposed wherein Ag2+-pairs and Ag2+ centers contribute to the RPL signal. A set of non-linear differential equations was written to describe the build-up process and numerical solution of these equations yielded simulated results which qualitatively matched the observed experimental data.

Beta energy dependence of the Ag-doped phosphate glass detector response

The radiophotoluminescent (RPL) signal of Ag-doped phosphate glass detectors to β-radiation is significantly influenced by β-particle energy. We investigate the β-particle energy and angular dependence of incident β radiation on the RPL signal emitted from the detectors. The results of measurements and MCNPX simulations show that the detector sensitivity decreases with increasing β-energy and has little dependence on the angle of incidence. The consequence is that a dose assessment will be strongly biased if the detector calibration is performed with β-rays different from those monitored.

Temperature dependence of radiophotoluminescence in Ag-doped phosphate glasses containing different alkali metals

Ag-doped phosphate glasses containing Na and Al cations have been used in radiophotoluminescence (RPL) dosimeters. The formation mechanism of RPL center (Ag2+ and ) in Ag-doped phosphate glasses, containing various cations, has unresolved issues. Herein, we investigated the mechanism of the RPL center formation in Ag-doped phosphate glasses from the viewpoints of temperature dependence and activation energy of RPL center formation. We estimated the activation energies of RPL center formation in Ag-doped phosphate glasses containing Na and Al (Na–Al/Ag), Na and K (Na–K/Ag), and Al and K (Al–K/Ag) cations. The activation energy of formation did not increase with the first ionization energy of the cations contained in the glasses. This result suggests that electrons are trapped not at cations but at negative ion vacancies before forming Furthermore, the activation energy of formation increased with increasing mean molecular volume as the distance between the electron trapping site and increases. On the other hand, the activation energy of formation decreased with increasing mean molecular volume which is the opposite of the result of Consideration of temperature dependence of RPL intensity, the intensity of the RPL corresponding to in Al–K/Ag increased slightly at 300 K from that at 25 K. In addition, the concentration at 25 K in Al–K/Ag was approximately half of that at 300 K. These results indicate that only holes trapped at shallow trap sites transfer to in Al–K/Ag.

Analysis of radiophotoluminescence center formation mechanism in Ag-doped phosphate glasses

Ag-doped phosphate glasses have widely been used as radiophotoluminescence (RPL) dosimeters. However, the RPL center formation process is not fully understood. In this study, we investigated the RPL center formation process in Ag-doped Na–Al phosphate glasses. We observed that two RPL centers (Ag0 and Ag2+) were formed at temperatures higher than 100 and 250 K, respectively. In addition, activation energies of their formation were estimated to be 20 and 267 meV, respectively. These results suggest that the electron transfer process is not a simple thermally activated process.

Radiophotoluminescence properties of Ag-doped mixed phosphate glasses

Ag-doped phosphate glasses have conventionally been used as materials for passive dosimeters. However, there are unsolved problems, such as the build-up process, and the influence of the composition of the phosphate glasses. It is necessary to elucidate the RPL process to resolve these issues. In this study, we investigated the radiation dose response of various Ag-doped phosphate glasses containing alkali metals as cations to optimize their composition. We further investigated the influence of mixed phosphate composition on the dose dependence of the PL and RPL properties. We found that the peak intensity of RPL increased with exposure dose of X-ray except Bi/Na-Ag, and the increase rate of the peak intensity with dose depends on alkali metals in the host. Furthermore, in the samples whose hosts are composed of Na and another alkali metal phosphate, the spectra are quite different from that of Na phosphate and are similar to those of the other alkali metal phosphates.

Radiophotoluminescence properties of Ag-doped phosphate glasses

The radiophotoluminescence (RPL) of Ag-doped phosphate glass has been used for personal dosimetry for a long time. In this study, we investigated the optical properties of Ag-doped various phosphate glasses. It is revealed that alkali metals in the phosphate are required to achieve the RPL, and that the alkali metals content has an influence on the RPL properties. Also, the ESR signal corresponding to the valence change of Ag was observed only for the phosphate glasses containing alkali metals. These results indicate that the RPL occurs based on the change in Ag valence state, which is consistent with commercial phosphate glasses used for dosimetry. In addition, the decay-time constants of the RPL were on the order of microseconds. Furthermore, initialization of the RPL was observed after heating at 473 K, which indicates that these glasses can be used repeatedly.

Radiation Dose Response of Ag-Doped Phosphate Glasses with Different Alkali Metal Compositions in the Host

Introduction For many years, the radiophotoluminescence (RPL) of Ag-doped phosphate glass has been exploited in personal dosimeters. On exposure to X-ray, gamma ray, and high-intensity laser irradiations, the electrons and holes are captured by the Ag+ ions in the glass structure, thereby changing the Ag+ ions into Ag0 and Ag2+, respectively [1]. Thus, Ag-doped phosphate glasses enable the estimation of the exposure dose due to the correlation between the amount of irradiation and the relative intensity of luminescence of the Ag0 and Ag2+ ions excited with ultraviolet light. In a previous research, we found that the peak wavelengths of the RPL bands depend on the alkali metal species used [2]. In this study, we investigated the radiation dose response of various Ag-doped phosphate glasses, containing alkali metals as cations, to optimize their composition and develop a higher-performance dosimeter. Experimental Methods The glass samples were prepared according to a conventional melt-quenching method in air. The raw materials, AgCl and (LiPO3)n (Li/Ag), were mixed, loaded into an alumina crucible and melted at 1073 K, for 30 min, in an electric furnace. The melt was then quenched on a stainless steel plate at 573 K, which is below the glass transition temperature. The same operations were also performed for NaPO3 (Na/Ag), (KPO3)n (K/Ag)，RbH2PO4 (Rb/Ag)and CsH2PO4 (Cs/Ag) instead of LiPO3. The Ag concentration was 0.1 mol% for all samples. In addition, phosphate glasses with mixed alkali metals were prepared in the same manner Li/Na-Ag, K/Na-Ag, Rb/Na-Ag, and Cs/Na-Ag. The samples were irradiated at room temperature with X-rays using an X-ray tube operating at 40 mA and 40 kV. The PL (photoluminescence) and RPL properties were analyzed using both PL and RPL spectra and the temporal luminescence profiles. The PL and RPL spectra were collected using an F-7000 (Hitachi) fluorescence spectrometer. The temporal profiles were recorded using a DeltaFlex 3000U-TMK2 (Horiba). The absorption spectra were measured using a spectrophotometer (Hitachi U-3500). Results The RPL spectra of the various Ag- doped phosphate glasses, irradiated with a dose of 50-Gy X-rays, are shown in Fig. 1. The sample K/ Na-Ag shows two emission band peaks, observed at 550 nm and 680 nm, with excitation at 310 nm. The peak of K is also detected at 550 nm with a line shapesimilar to that of the sample K/Ag. On the other hand, the peak of K/ Na-Ag observed at 680 nm shows a line shape similar to that of Na/Ag . These results indicate that Na-K/Ag is composed of K/Ag and Na/Ag domains and that Na and K phosphate layers are separately formed around fluorescent centers.

Radiophotoluminescence Properties of Ag-Doped Phosphate Glasses Containing Different Alkali Metal Cations

Radiophotoluminescence Properties of Ag-Doped Phosphate Glasses Containing Different Alkali Metal Cations

Radiophotoluminescence Properties of Ag-Doped Phosphate Glasses Containing Different Alkali Metal Cations

Radiophotoluminescence Properties of Ag-Doped Phosphate Glasses Containing Different Alkali Metal Cations

A comparative study of optical and radiative characteristics of X-ray-induced luminescent defects in Ag-doped glass and LiF thin films and their applications in 2-D imaging

We report novel disk-type X-ray two-dimensional (2-D) imaging detectors utilising Ag-doped phosphate glass and lithium fluoride (LiF) thin films based on the radiophotoluminescence (RPL) and photoluminescence (PL) phenomena, respectively. The accumulated X-ray doses written in the form of atomic-scale Ag-related luminescent centres in Ag-doped glass and F-aggregated centres in LiF thin films were rapidly reconstructed as a dose distribution using a homemade readout system. The 2-D images reconstructed from the RPL and PL detectors are compared with that from the optically stimulated luminescence (OSL) detector. In addition, the optical and dosimetric characteristics of LiF thin films are investigated and evaluated. The possibilities of dose distributions with a high spatial resolution on the order of microns over large areas, a wide dynamic range covering 11 orders of magnitude and a non-destructive readout are successfully demonstrated by combining the Ag-doped glass with LiF thin films.