Glass Scintillator Research Articles

Multipurpose Ce-doped Ba-Gd silica glass scintillator for radiation measurements

A new inorganic scintillation material based on Ba-Gd silica glass doped with cerium (BGS) is fabricated and studied. With the highest light yield among heavy glasses at the level of 2500 ph/MeV and fast scintillation response, the new scintillator ensures a good coincidence time resolution of < 230 ps FWHM for 511 keV γ-quanta from a 22Na source and SiPM readout. In addition to good performance in γ-quanta detection, the material demonstrates capability for efficient detection of low-energetic​ neutrons. The scintillator is produced by exploiting the standard industrial glass technology, which allows for an unlimited scaling up the conversion of raw material into a high-quality scintillator at a high rate. The glass can be casted in application-specific molds, so minimizing the material losses. The presented glass scintillator has potential for further improvement of its light output and scintillation response time.

Organic glass scintillator bars with dual-ended readout

Organic glass scintillator (OGS) bars (6 × 6 × 50 mm3) were melt-cast and characterized with dual-ended readout by silicon photomultiplier arrays. The results were compared to trans-stilbene bars of the same size. Energy resolution was measured via a 137Cs Compton-coincidence experiment. Time resolution was determined via a 22Na coincidence-timing experiment. Depth-of-interaction resolution was measured by moving a gamma-ray fan beam along the major axis of the bars. Pulse shape discrimination capability and neutron light output were determined via a time-of-flight measurement of a 252Cf source. The OGS bars exhibited better energy resolution at 478 keV (10.3±0.5% vs. 11.2±0.5%), better time resolution from 200–341 keVee (270ps vs. 340ps FWHM), slightly poorer depth-of-interaction resolution, poorer PSD performance, and higher neutron light output than the stilbene bars. The low cost, ease of manufacturing, brightness, and excellent time resolution make OGS a strong candidate for use in compact radiation imaging systems.

Gadolinium contained scintillation glass for neutron detection in a wide energy range.

Inorganic scintillation glasses form a domain of rapidly evolving detector materials used to measure various types of ionizing radiation. The most widespread are lithium-silicate glasses enriched with the 6Li isotope, which are used to register thermal neutrons. At the same time, due to the specificity of the energy dependence of the neutron cross-section of light nuclei, such materials are of little use for the evaluation of epithermal and more highly energetic neutrons. The use of rare earth elements in the composition of glasses makes it possible to increase the sensitivity to neutrons. In the BaO–Gd2O3–SiO2 system, doped with Ce ions, a scintillation glass with a yield of at least 2500 photons / MeV was created for the first time, which permits to create inexpensive detector elements of a significant volume for registering neutrons. It has been shown that a detector based on BaO–Gd2O3–SiO2 glass has satisfactory properties when detecting neutrons in a wide spectrum of their energies.

Frequency-dependent optimal weighting approach for megavoltage multilayer imagers

Multi-layer imaging (MLI) devices improve the detective quantum efficiency (DQE) while maintaining the spatial resolution of conventional mega-voltage (MV) x-ray detectors for applications in radiotherapy. To date, only MLIs with identical detector layers have been explored. However, it may be possible to instead use different scintillation materials in each layer to improve the final image quality. To this end, we developed and validated a method for optimally combining the individual images from each layer of MLI devices that are built with heterogeneous layers. Two configurations were modeled within the GATE Monte Carlo package by stacking different layers of a terbium doped gadolinium oxysulfide Gd2O2S:Tb (GOS) phosphor and a LKH-5 glass scintillator. Detector response was characterized in terms of the modulation transfer function (MTF), normalized noise power spectrum (NNPS) and DQE. Spatial frequency-dependent weighting factors were then analytically derived for each layer such that the total DQE of the summed combination image would be maximized across all spatial modes. The final image is obtained as the weighted sum of the sub-images from each layer. Optimal weighting factors that maximize the DQE were found to be the quotient of MTF and NNPS of each layer in the heterogeneous MLI detector. Results validated the improvement of the DQE across the entire frequency domain. For the LKH-5 slab configuration, DQE(0) increases between 2%–3% (absolute), while the corresponding improvement for the LKH-5 pixelated configuration was 7%. The performance of the weighting method was quantitatively evaluated with respect to spatial resolution, contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of simulated planar images of phantoms at 2.5 and 6 MV. The line pair phantom acquisition exhibited a twofold increase in CNR and SNR, however MTF was degraded at spatial frequencies greater than 0.2 lp mm−1. For the Las Vegas phantom, the weighting improved the CNR by around 30% depending on the contrast region while the SNR values are higher by a factor of 2.5. These results indicate that the imaging performance of MLI systems can be enhanced using the proposed frequency-dependent weighting scheme. The CNR and SNR of the weighted combined image are improved across all spatial scales independent of the detector combination or photon beam energy.

Strong emission from Ce3+ doped gadolinium oxyfluoroborate scintillation glasses matrix

The gadolinium oxide and oxyfluoride borate glasses doped with cerium ion (Ce3+) were studied comparatively in the physical, glass network, optical, luminescence and scintillation properties. The average values of glass density and molar volume represent that oxide glass is heavier and possesses larger molar-size than oxyfluoride glass. FTIR measurement confirms the main glass network of both glass series are based on BO4 unit, and the OH group amount in oxide glass is higher than in oxyfluoride glass. Oxide and oxyfluoride glasses in this work absorb the photons in ultraviolet and initial visible light region proved by the absorption spectra. The ultraviolet, with 275 and 310 nm wavelengths, and X-ray radiation were used to excite the glass samples to investigate the luminescence spectra. The emission broad bands around 300 – 500 nm (excited by ultraviolet) and 350 – 650 nm (excited by X-ray) exhibit the luminescence under electronic transition of Ce3+. The emission intensity of oxyfluoride glass is beyond intensity of oxide glass due to less amount of OH group vibration. The X-ray integral-scintillation efficiency of CeF3 doped oxide and oxyfluoride glass is 8.98% and 45.89%, respectively, compared to BGO crystal. The oxyfluoride borate glasses doped with Ce3+ performs the high potential for using as a glass scintillator in the X-ray and possibly in the neutron scintillation detector.

Optical and radiation response characteristics of Eu2O3-doped K2O–Bi2O3–Ga2O3 glasses

Glass compounds have gained attention as scintillating materials owing to their large production possibility, easy shaping and flexible glass composition, and various glasses such as silicate, germanate and borate glasses have been considered for scintillator applications. Herein, Eu2O3-doped bismuth gallate glasses having a composition of 5K2O–70Bi2O3–25Ga2O3 were synthesized for the development of new glass scintillators by the melt-quenching method. After the fabrication of the undoped and Eu2O3-doped bismuth gallate glasses, their optical and scintillation characteristics were evaluated. The Eu2O3-doped bismuth gallate glasses showed photoluminescence (PL) and scintillation with sharp peaks centered at approximately 596 and 612 nm due to the electronic 4f → 4f transitions of Eu3+. The PL and scintillation spectra revealed that the concentration dependence of the PL quantum efficiency for the Eu2O3-doped bismuth gallate glasses was well correlated with that of the scintillation intensity. The decay time constants of the 0.5% and 1.0% Eu2O3-doped bismuth gallate glasses under visible light and X-ray irradiation were approximately 0.55 ms and 0.15 ms, respectively. In addition, the undoped and Eu2O3-doped bismuth gallate glasses exhibited afterglow levels of 330–660 ppm, and their moderate levels were found to be almost comparable to the afterglow level of Tl-doped CsI.

Spectroscopic investigation on Eu3+-doped TeO2-Lu2O3-WO3 optical glasses

Eu3+-doped tellurite glasses with the nominal composition of 64TeO2-20WO3-(16-y)Lu2O3-yEu2O3 were prepared by melt-quenching method. The glass stability was evaluated by some thermodynamic temperature derived a DTA curve. Their optical properties are revealed by transmittance, excitation, emission and XEL spectra, together with the luminescence decay curves. The optimal content of Eu2O3 was determined to be 8 (under 394 nm excitation) and 10 mol% (under X-ray excitation), respectively. The highly transparent Eu3+-doped TeO2-Lu2O3-WO3 with density of 6.35 g/cm3 shows the lifetime of about 0.725 ms, and gives red emission at 613 nm under X-ray excitation, which implies the potential detection application of the slow events as a novel glass scintillator.

Development of a portable Single Sphere Neutron Spectrometer

A portable Single Sphere Neutron Spectrometer (SSNS) is designed to measure the neutron energy spectrum in the mixed radiation field. The spectrometer consists of a 30 cm diameter single polyethylene moderating sphere with 19 pieces 6Li and 1-piece 7Li glass scintillator detectors located at the orthogonal X/Y/Z axis. The output signals from each detector are processed and readout by the Silicon Photomultipliers (SiPMs) and the Application Specific Integrated Circuit (ASIC) electronic system. The neutron energy responses of portable SSNS are calibrated in the mono-energetic neutron reference fields (144 keV, 1.2 MeV, 5 MeV, 14.8 MeV) based on the 5SDH-2 tandem accelerator in China Institute of Atomic Energy, which are also simulated from 0.0253 eV to 20 MeV by Monte Carlo simulation. The performance of portable SSNS is tested at different distances in 241Am–Be neutron reference radiation field in National Institute of Metrology, China. The fluence response of SSNS is about 0.28 cm2 for 241Am–Be neutron source.

Boron-loaded organic glass scintillators

Herein we report the progress towards an organic glass scintillator with fast and thermal neutron sensitivity providing “triple” pulse shape discrimination (PSD) through the inclusion of a boron-incorporated aromatic molecule. The commercially available molecule 2-(p-tolyl)-1,3,2-dioxaborinane (TDB) can be readily synthesized in one step using inexpensive materials and incorporated into the organic glass scintillator at 20% by weight or 0.25% 10B by mass. In addition, we demonstrate that TDB can be easily scaled up and formulated into organic glass scintillator samples to produce a thermal neutron capture signal with a light yield equivalent to 120.4 ± 3.7 keVee, which is the highest value reported in the literature to date.

Comparative scintillation performance of EJ-309, EJ-276, and a novel organic glass

An organic glass scintillator developed by Sandia National Laboratories was characterized in terms of its light output and pulse shape discrimination (PSD) properties and compared to commercial liquid (EJ-309) and plastic (EJ-276) organic scintillators. The electron light output was determined through relative comparison of the 137Cs Compton edge location. The proton light yield was measured using a double time-of-flight technique at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. Using a tunable broad-spectrum neutron source and an array of pulse-shape-discriminating observation scintillators, a continuous measurement of the proton light yield was performed for EJ-309 (200 keV–3.2 MeV), EJ-276 (170 keV–4.9 MeV), and the organic glass (50 keV–20 MeV) . Finally, the PSD properties of the organic glass, EJ-309, and EJ-276 were evaluated using an AmBe source and compared via a figure-of-merit metric. The organic glass exhibited a higher electron light output than both EJ-309 and EJ-276. Its proton light yield and PSD performance were comparable to EJ-309 and superior to that of EJ-276. With these performance characteristics, the organic glass scintillator is well poised to replace current state-of-the-art PSD-capable scintillators in a range of fast neutron detection applications.

Backside Illuminated 3-D Photosensitive Thin-Film Transistor on a Scintillating Glass Substrate for Indirect-Conversion X-Ray Detection

A conventional large-area indirect-conversion X-ray detector usually adopts front side illumination (FSI) of a scintillator atop a photodiode-integrated thin-film transistor (TFT) array. This work however proposes a backside illuminated (BSI) three-dimensional dual-gate photosensitive a-Si:H TFT (3-D DGTFT) on a scintillating glass substrate, aiming for indirect-conversion X-ray detection. It not only improves the sensitivity with a 3-D photosensitive TFT as an active pixel sensor, but also enhances the resolution and photon utilization by reducing photon scattering and optical crosstalk. Backside illumination of 3-D photosensitive TFT-integrated scintillating glass therefore provides an alternative approach to large-area indirect-conversion X-ray imaging.

Laboratory Evaluation of Beauveria bassiana ARP14 Against Grapholita molesta (Lepidoptera: Tortricidae).

Entomopathogenic fungi often have wide host range and can be important biological control agents against the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a significant pest of stone and pome fruits. The virulence of six entomopathogenic fungi, including three strains of Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) (ARP14, GHA, A) and one strain each of Metarhizium robertsii Bischoff, Rehner, & Humber (Hypocreales: Clavicipitaceae), Metarhizium brunneum (Petch) (Hypocreales: Clavicipitaceae), and Isaria farinosa (Holmsk.) (Hypocreales: Cordycipitaceae) was assessed against first instars (< 5 h old) of G. molesta held in glass scintillation vials. Compared to commercialized strain of B. bassiana (GHA), B. bassiana ARP14, which was recovered from a cadaver of Riptortus pedestris (F.) (Hemiptera: Alydidae), killed first instar larvae 2.6 times faster at 12 h after exposure to 1 × 108 conidia/ml concentration at 95.9% RH and 25.4 °C. However, the mycosis rate after 14 days was similar to that of B. bassiana GHA in all treatments. Beauveria bassiana ARP14 also killed adult moths 2.7 (males) and 2.2 (females) times faster than did B. bassiana GHA, measured 168 h (7 days) after exposure. However, the mycosis rate after 14 days was similar from both fungi. In assay using three conidial concentrations (1 × 107, 1 × 108, and 1 × 109 conidia/ml) and three RHs levels (55, 75, and 95%). Mortality became higher as concentration and RH increase, but mycosis rate at 14 days wasn't significantly different among treatments. These results suggest that B. bassiana ARP14 can be a potential biological control agent against G. molesta.

Multiphase Transition toward Colorless Bismuth-Germanate Scintillating Glass and Fiber for Radiation Detection.

The applications of scintillating fiber in high-resolution medical imaging, remote radiation monitoring, and microbeam radiation therapy have raised a growing demand of bismuth-germanate (BGO) glass fiber. However, the task of construction of colorless BGO glass fiber has been met with limited success. Here, we present a renewable process that can help to achieve BGO scintillating fiber, based on glass relaxation and crystallization mediated dissolution of unexpected Bi center. The experimental results indicate that the strategy can improve the optical transmittance up to more than 73.17% at 483 nm, which is ∼6.28 times higher than that of the conventional material. Importantly, the obtained nanostructured BGO exhibits bright visible luminescence under excitation with X-ray. Furthermore, it can host various types of rare-earth dopants, and the radiation-induced luminescence can be tuned in a wide waveband region from visible to infrared waveband. In addition, colorless BGO fiber with bright emission is also successfully constructed, and the radiation probing test demonstrates the achievement of ∼19.48 times improvement in the detection sensitivity. Our results highlight the approach based on the dynamic glass relaxation may provide new opportunities for construction of scintillating glass fiber and compact radiation fiber detector.

Photoluminescence and scintillation properties of Al(PO3)3–CeCl3–CsCl–CsPO3 glass scintillators

The photoluminescence (PL) and scintillation properties of Al(PO3)3–CsPO3–0.5CsCl–xCeCl3 (x = 0.05, 0.1, 0.2, 0.3, 0.5) glass scintillators were analyzed. Glasses with different concentrations of Ce3+ were fabricated via the melt-quenching method under vacuum. The X-ray diffraction patterns of all the samples except those with x = 0.3 and 0.5 presented only halo features and no sharp diffraction peaks, indicating a crystalline structure and, in turn, the amorphous nature of the glasses. The PL emission and X-ray-induced radioluminescence spectra presented a fluorescence band at ~ 350 nm, which were attributed to allowed transition from the Ce3+ 5d excited state to the 4f ground levels (2F5/2 and 2F7/2). The PL and scintillation decay time were estimated to be ~ 35 ns. The glass scintillators with x = 0.3 exhibited the maximum light yield, which was approximately 2100 photons/MeV.

Design and Optimisation of a Three Layers Thermal Neutron, Fast Neutron and Gamma-Ray Imaging System

The design and configuration of a multi-layered imaging system with the ability to detect thermal neutrons, fast neutrons and gamma rays has been developed and its efficacy demonstrated. The work presented here numerically determines the systems efficiency and spatial resolution, using 252Cf and 137Cs as a case study. The novelty of this detection system lies in the use of small form factor detectors in a three-layer design, which utilises neutron elastic scattering and Compton scattering simultaneously. The current configuration consists of 10 mm thick natural lithium glass (GS10) scintillator integrated with a 20 mm thick plastic scintillator (EJ-204) in the first layer, a 15 mm thick lithium glass (GS10) scintillator in the second and a 30 mm thick CsI(Tl) scintillator forming the final layer. Each of these layers is backed with an 8 x 8 silicon photomultiplier diode (SiPM) array. The overall size of the imaging system is 27 mm x 27 mm x 135 mm. MCNPv6.1 and Geant4-10.04 were alternatively used to optimise the overall configuration and to investigate detection modalities. Results show promising performance with high precision source localisation and characterization abilities. Measurements were virtually obtained of two gamma-ray sources within steel enclosures at angles of 15°, 30° and 50° separation in order to test spatial resolution ability of the system. With the current active size of the system and the 8x8 SiPM configuration, the results estimate the spatial resolution to be close to 30°. The ability of the system to characterise and identify sources based on the type and energy of the radiation emitted, has been investigated and results show that for all radiation types the system can identify the source energy within the energy range of typical reported sources in literature.

Li-Based Glasses for Neutron Detection—Classic Material Revisited

The background and preparation procedures of Li-based scintillation glasses for neutrons detection are reviewed here. The nuclear-physical modeling was used to justify the composition choice. Technological factors, which strongly influence hands-on glass preparation experience, are considered. Particular attention is paid to understanding the stabilization of activator ions, especially Ce, in 3+ oxidation state. A new approach is proposed, which allows to improve the preparation procedure reliability for glasses based on lithium disilicate.

Evaluation of lithium glass scintillation detector responses for tritium production rate measurement in blanket neutronics experiments using the PHITS code

Lithium (Li) glass scintillation detectors were utilized by the neutron response of a 7Li glass subtracted from the neutron response of a 6Li glass to evaluate the tritium production rate (TPR) in the fusion blanket neutronics experiments, which is a so called Li glass method. TPRs in the Li2O blanket and the Li/V-alloy blanket were measured by a 6Li2O and a 6Li2CO3 pellet method, and by the Li glass method in the benchmark neutronics experiment with D-T neutrons at the Fusion Neutronics facility (FNS) of JAERI. TPRs measured by the Li glass method are lower than TPRs measured by the pellet method. The neutron responses of Li glass detectors have been calculated to study the discrepancies of two different methods by using the PHITS code. In the blanket, the neutron spectra change to harder from the backside to the front side of blanket. The reaction rate of several reactions, such as 6Li(n, n’α)D, 7Li(n, n’α)T, 7Li(n, 2n)6Li, and the elastic scattering of 6Li and 7Li increase with the neutron energy. The low-energy neutron peak was considered only for the calculation of TPR from Li glass, which loses the information of the 6Li(n, α)T reaction from high-energy neutron range. In addition, the reaction rate of this peak evaluated by the Li glass method is lower than real TPR of this peak for 6Li glass caused by weakened effect from other reactions. Therefore, the ratios of this peak reaction rate from the Li glass method against the total TPR of 6Li glass were evaluated to be a correction factor to correct Li glass method. After the correction, TPRs measured by Li glass method agree well with TPRs measured by pellet method.

High spatial resolution cold neutron imaging with new Tb3+/Ce3+ co-doped Gd2O3 scintillation glass fiber arrays

Abstract The fiber-array-structured scintillation detectors can achieve both high detection efficiency and high spatial resolution for cold neutron radiography. Three novel Tb 3 + /Ce 3 + co-doped Gd 2 O 3 scintillation glass fiber arrays with different thicknesses (0.3 , 0.4 , 0.5 mm) have been fabricated and tested. These arrays were composed of 10 µm diameter Tb 3 + /Ce 3 + co-doped Gd 2 O 3 glass fibers, cladding glass, and extra-mural absorption (EMA) glass. The spatial resolution and the cold neutron absorption efficiency of the imaging system made of 0.4 mm thick fiber array and an optical readout system were measured to be 10 lp/mm (line pairs per millimeter) and 93.4 % for cold neutrons, respectively. The optical readout system consists of a cooled Andor iKon-LDZ936 charge-coupled device, a mirror, and a Nikon Nikkor 135 mm lens. The spatial resolution of the cold neutron imaging system is mainly limited by the low resolution of the optical readout system. To further characterize the spatial resolution of these arrays, a higher resolution optical readout system is desired.

Construction and test of a single sphere neutron spectrometer based on pairs of 6Li-and 7Li-glass scintillators

A single sphere neutron spectrometer (SSNS) was designed to measure the neutron energy spectrum in mixed radiation fields. The spectrometer consisted of a 30 cm diameter single polyethylene moderating sphere with 19 pairs of 6Li- and 7Li-glass scintillator detectors located at the orthogonal x-, y-, z-axis. The glass scintillator detector was composed of glass scintillator, light guide and photomultiplier tube. The output signals from each detector were processed and read out by a charge division resistance network and an electronic system. The thermal neutron counts were discriminated by subtracting the signal counts of 7Li-glass scintillator detector from the signal counts of 6Li-glass scintillator detector at the same position. The neutron energy response of the SSNS was calibrated in mono-energetic neutron fields (144 keV, 250 keV, 565 keV, 1.2 MeV, 2.5 MeV, 14.8 MeV) based on the 5SDH-2 tandem accelerator in China Institute of Atomic Energy, which was also simulated from 0.0253eV to 19 MeV by the Monte Carlo method. Finally, a241Am–Be neutron energy spectrum and the ambient dose equivalent values were measured using the SSNS. The deviation between the experimental result of the SSNS and the reference value was 2.6%.

Measured neutron light-output response for trans-stilbene and small-molecule organic glass scintillators

Abstract The neutron light-output response from quasi-monoenergetic neutrons was measured for a O5.08 × 5.08 cm trans-stilbene and a O5.08 × 5.08 cm small-molecule organic glass scintillator . Quasi-monoenergetic neutrons were isolated from a time-of-flight measurement of a Cf-252 spontaneous fission source with a flight distance of 200 cm. Two different methods of waveform analysis were implemented, where the neutron light output response proportional to the detected pulse height distribution (PHD) and pulse integral distribution (PID) were extracted for both types of scintillators. The light output response proportional to the pulse integral was determined by integrating the digitized waveform with an integration window length of 150 ns, which contained > 90% and > 95% of the scintillation light for an averaged neutron and photon waveform above 0.5 MeVee. The extracted light-output data were fitted with a semi-empirical function based on the Birks’ formula. The results show that the small-molecule organic glass scintillator produced more light than the trans-stilbene scintillator for a range of neutron energies of 0.79 ± 0.04 MeV to 3.65 ± 0.38 MeV. The fitted semi-empirical function was used in MCNPX-PoliMi with MPPost to simulate the detector response from an independent measurement of a Cf-252 spontaneous fission source to test the fidelity of the extracted light output response functions. The simulated and measured total neutron count rate agreed to within ± 3 % and ± 1% for the trans-stilbene and small-molecule organic glass scintillators. Due to the different light-output response of the two scintillators, the intrinsic neutron detection efficiency was calculated for equal observable ranges in light output and neutron-equivalent energy units. The intrinsic neutron detection efficiency in the observable light-output range of 0.06 MeVee to 2.4 MeVee was calculated to be 28.66 ± 1.43 % and 34.66 ± 1.73 % for pulse height and pulse integral analysis, respectively. For the same observable light-output range, the intrinsic efficiency of small-molecule organic glass was calculated to be 32.54 ± 1.63 % and 37.39 ± 1.87 % for pulse height and pulse integral analysis, respectively. When observing equal light-output ranges, the small-molecule organic glass was 11.92 ± 6.23% and 7.88 ± 7.35% more efficient than the trans-stilbene using pulse height and pulse integral analysis, respectively. When observing equal neutron-equivalent energy ranges, the trans”–stilbene scintillator was 8.4 ± 6.46% and 11.95 ± 6.23% more efficient than the small-molecule organic glass for pulse height and pulse integral analysis, respectively.