High Scintillation Research Articles

Two-Dimensional Mapping of Ionospheric Total Electron Content over the Philippines Using Kriging Interpolation

Monitoring of ionospheric total electron content (TEC) was made possible with the help of satellite data, albeit in one dimension. However, ionospheric TEC maps can be produced from a collection of one-dimensional satellite data over a geographic area. Multiple mapping methods have been recognized; however, this study tried to test one of those methods: kriging interpolation. An algorithm was developed and used to reconstruct GIMs. The optimum number of stations and the semivariogram model were evaluated using GIM maps modeling 12 days of March 2015, accounting for different ionospheric conditions. This includes days of high scintillation and an ionospheric storm due to the St. Patrick’s Day geomagnetic storm of 2015. It was found that 12 stations and the linear semivariogram model had the least mean error in 5 days and had the least standard deviation in 7 days, making it the optimum parameter set. This optimum set was then used to map and analyze the ionosphere using actual satellite data from the Philippine Active Geodetic Network (PAGeNet). From this, it was observed that there is a north–south gradient in VTEC in the region during the day. The VTEC in the north reaches more than 100 TECU, and, in the south, generally around 60–90 TECU depending on the ionospheric condition. VTEC was at a minimum during the night when the VTEC level decreases to around 10 TECU.

High scintillation yield and fast response to alpha particles from thin perovskite films deposited by pulsed laser deposition

Although the field of solar cells is the most popular application of perovskite materials, their use in radiation detection applications is emerging. The success of perovskites as radiation detectors rests partly on the same material properties that have led to successful optoelectronics applications, meaning that other specific properties, like large stopping power, high mobility lifetime product, fast response, and large bulk resistance, play a role. In this respect, inorganic perovskites are attracting a lot of attention as scintillator materials with performances sensitive to material shape (single crystals, nanocrystals, and thin films) and growth methods. In this study, we report on the morphological, structural, and optical response of thin CsPbBr3-based perovskite films, deposited by Pulsed Laser Deposition (PLD) and post-growth annealed at 350°C in air, following excitation by different particle sources. The annealing treatment resulted in a prompt structural refinement, grain growth, and oxygen bonding to the Pb phase together with an enrichment of the surface in chemo-adsorbed oxygen probably due to Cs–O interactions, as evidenced by X-ray photoelectron spectroscopy. The film behavior under 2 MeV H+ ion beam irradiation at different fluences was analyzed together with its scintillation properties following an interaction with α particles from an Am-241 radioactive source demonstrating a very fast response for an inorganic material (∼5ns) and a photoelectron yield of about ∼47% with respect to a commercial CsI:Tl scintillator.

Simulation of a micron resolution capillary liquid scintillation detector for 14 MeV fusion neutrons

Aiming to improve the spatial resolution of a neutron imaging system (NIS) for 14 MeV fusion neutrons, an ideal micron resolution capillary detector filled with a high optical index liquid scintillator was simulated. A threshold for each capillary pixel and a threshold for each cluster were applied to suppress the gamma-induced background. In addition, by using a pattern recognition algorithm and an optimized Hough transform, the accuracy of determining the neutron impinging positions and the dynamic range of this detector were enhanced. For an ideal capillary array detector, the spatial resolution is expected as one capillary size of 20μm. The dynamic range of ∼1000 is reachable while the accuracy of neutron impinging position determination keeps better than 85%. The ionization quenching, light sharing and energy resolution of the detector were applied to the simulated data to understand the capillary array detector.

Heavily cerium-doped (Gd,La)AlO3 ceramic scintillators: Material optimization study

Cerium-doped aluminates with a perovskite structure are studied for their prospective material properties aiming at their application in scintillation detectors. These materials exhibit high density, and thermal and chemical stability and thanks to the allowed 5d-4f transition of Ce3+ also high scintillation emission intensity and fast decay can be obtained. Commercially successful perovskite scintillator is the cerium-doped yttrium aluminium perovskite (YAlO3:Ce) produced in single crystal form by the Czochralski method. To overcome its disadvantage of low density and effective atomic number the single crystal of gadolinium aluminium perovskite doped with cerium (GdAlO3:Ce) was studied, but has shown significantly lower light. This work pursues a new approach to improve the scintillation properties of this material. Ceramic pellets of gadolinium aluminium perovskite doped with cerium and admixed with lanthanum ((Gd,La)AlO3:Ce) were prepared using co-precipitation method. The effect of cerium and lanthanum content was studied using the radioluminescence and luminescence spectroscopy. An improvement of scintillation properties (emission intensity and decay kinetics), in comparison to GdAlO3:Ce reported so far, was achieved.

Feasibility study to use neutron capture for an ultralow energy nuclear-recoil calibration in liquid xenon

The feasibility of an ultra-low energy nuclear-recoil measurement in liquid xenon using neutron capture is investigated for a small (sub-kilogram) liquid xenon detector that is optimized for a high scintillation gain, and a pulsed neutron source. The measurement uses the recoil energies imparted to xenon nuclei during the de-excitation process following neutron capture, where promptly emitted $\gamma$ cascades can provide the nuclei with up to $0.3$ keV$_\text{nr}$ of recoil energy due to conservation of momentum. A successful calibration of scintillation photon and ionization electron yields below this energy will contribute to a greater sensitivity for liquid xenon experiments in searches for light WIMPs.

Performance of a scintillation imaging system for relative dosimetry in pencil beam scanning proton therapy

The proton spot scanning system requires extensive periodic quality assurance procedures to guarantee the conformality of planned dose distribution to the tumor. Detectors with stable, accurate, and fast data acquisition properties make the quality assurance procedures more efficient. For this purpose, a camera-based scintillation imaging system has been developed. A high scintillation efficiency screen coupled with a high-performance camera improved the dose sensitivity and precision required for the measurements. The dose distribution within the scintillating screen can be analyzed from the captured light distribution image in a relatively straightforward way.In this study, we investigated the performance of a 2D detection system by using a scintillating screen (silver-activated zinc sulfide powder deposited on the surface of a plastic scintillator HND-S2) for dose distribution measurement. The characteristics of the system in terms of response reproducibility, linear dose–response, and beam spot size dependence on proton dose were assessed in a series of proton irradiations. To evaluate the accuracy of lateral dose profiles measured by the ZnS: Ag based scintillating screen, we compared the results with plastic scintillator BC-408 and some commercial quality control devices. Several measurements were conducted with proton energies ranging from 70–235 MeV. We found that the detector showed stable response reproducibility (better than 1.6%) and good dose–response linearity (R2¿0.999). The beam spot size was independent of proton dose when the response of the pixel value was between 10% and 90% of the maximum. The in-air spot size measured by the ZnS: Ag based scintillating screen was found to be slightly smaller than the Lynx detector while the BC-408 showed a slightly bigger spot size. The inter-comparison results for scanned fields showed good agreements. The observed differences in beam profile measurement between the inorganic and organic scintillating screens were mainly due to their optical properties and structures. The developed scintillation imaging system with an effective resolution of 0.12 mm proved to be a reliable device for efficiently performing the quality checks for two-dimensional proton dosimetry.

Mechanical Properties of High Temperature Resistant Energy Storage Dielectric Materials and Radiation Scintillation Detection Composite Materials in Bridge Construction

With the rapid development and utilization of energy by human beings, the preparation of high-efficiency energy storage materials has become a current hot spot. This article mainly studies the mechanical properties of high temperature resistant energy storage dielectric materials and radiation scintillation detection composite materials in bridge construction. In this paper, the dispersion conditions of PBI on carbon nanomaterials were optimized, and PBI derivatives with different chemical structures were synthesized to enhance the interface force between them and carbon nanomaterials. By means of physical blending and chemical reaction grafting, the non-covalent modification or covalent modification of the surface of CNTs and graphene by the polymer was realized. In this paper, FTIR can be used to characterize the molecular structure and segment conformation (crystal phase) of PVDF-based polymers. The attenuated total reflection (ATR) mode of the E55 + FRA106 instrument was used to directly test the polymer film. In this paper, MCNP is used to simulate the interaction between Y-rays and crystal, and the structure of the detector probe is designed, including the selection of crystal material, the design of crystal size, and the requirements of structural packaging. A self-made plastic light cone is used for the coupling between the scintillator and the transmission fiber. With the increase of TPU content, the breakdown strength of the composite film showed a trend of first increasing and then decreasing. TPUs with three hardnesses all showed the highest breakdown field strength at a content of 3 vol%. The results show that changing the direct connection between the scintillator and the PMT to the light guide connection can effectively improve the light collection efficiency of the detection system. Under the simulation conditions in this article, the increase is about 30%, which is considerable and has a certain energy resolution capability.

0D Organic Manganese(II) Bromide Hybrids as Stable and Efficient X‐Ray Scintillator

Low‐dimensional organic–inorganic hybrids have emerged as promising X‐ray scintillators due to efficient radioluminescence properties. Herein, stable and efficient X‐ray scintillator based on 0D (C40H38P2)MnBr4 hybrid single crystals grown by a facile solution‐processing method is reported. Its crystal structure is determined to be triclinic with P space group. It has good stability against moisture and irradiation. (C40H38P2)MnBr4 with tetrahedrally coordinated Mn2+ exhibits green emission peaking at 518 nm originating from d–d 4T1→6A1 transition of Mn2+ ion with a high photoluminescence quantum yield (PLQY) of 74.2%. Under X‐ray excitation, it shows high scintillation yield of 32 000 photons MeV−1, a decent detection limit of 288 nGyair s−1, and a low afterglow comparable to that of Bi4Ge3O12 (BGO).

Monte Carlo calculations of the extraction of scintillation light from cryogenic N-type GaAs

The high scintillation luminosity of n-type GaAs at 10 °K is surprising because (1) with a refractive index of 3.5, escape is inhibited by total internal reflection and (2) narrow-beam experiments at 90 °K report infrared absorption coefficients of several per cm. This paper presents Monte Carlo calculations showing that the high luminosity at 10 °K can be explained if (1) the narrow-beam absorption is almost all optical scattering and (2) the absolute absorption coefficient is below 0.1 per cm. Sixteen surface reflector configurations are simulated for a range of internal scattering and absolute absorption coefficients, and these can guide the design of cryogenic scintillating GaAs targets for the direct detection of dark matter. The discussion section presents a possible infrared scattering mechanism based on the metallic nature of n-type GaAs. A supplement file describes (1) the Monte Carlo program steps in detail and (2) how narrow-beam and integrating sphere experiments can measure the cryogenic optical scattering and absolute absorption coefficients.

Ultrathin, Transparent, and High Density Perovskite Scintillator Film for High Resolution X-Ray Microscopic Imaging.

Inorganic perovskite quantum dots CsPbX3 (X = Cl, Br, and I) has recently received extensive attention as a new promising class of X‐ray scintillators. However, relatively low light yield (LY) of CsPbX3 and strong optical scattering of the thick opaque scintillator film restrict their practical applications for high‐resolution X‐ray microscopic imaging. Here, the Ce3+ ion doped CsPbBr3 nanocrystals (NCs) with enhanced LY and stability are obtained and then the ultrathin (30 µm) and transparent scintillator films with high density are prepared by a suction filtration method. The small amount Ce3+ dopant greatly enhances the LY of CsPbBr3 NCs (about 33 000 photons per MeV), which is much higher than that of bare CsPbBr3 NCs. Moreover, the scintillator films made by these NCs with high density realize a high spatial resolution of 862 nm thanks to its thin and transparent feature, which is so far a record resolution for perovskite scintillator‐based X‐ray microscopic imaging. This strategy not only provides a simple way to increase the resolution down to nanoscale but also extends the application of as‐prepared CsPbBr3 scintillator for high resolution X‐ray microscopic imaging.

A new optical photon transport model for application to high aspect ratio scintillation pillars

A new Monte Carlo model of optical photon transport has been developed for application to scintillation pillars with side surfaces modeled using their measured 3D topography. The model addresses deficiencies of existing models specifically pertinent to high aspect ratio scintillator geometries. Inaccuracies with these models’ description of the reflectance of scintillation photons at media boundaries are exacerbated by the high number of surface interactions in such geometries. These models rely either on (a) user-specified parameters that are challenging to set, or (b) pre-computed look-up tables that assume geometrically unconstrained photon incidence on uniform surface finishes, an assumption that is invalid in high aspect ratio geometries. Alternatively, the new model reconstructs the side surfaces of a pillar from 3D topographic measurements and uses first-principles physics of reflection and transmission to transport photons over the surfaces’ microscopic features and throughout the entire pillar volume. It takes advantage of the recent availability of open-source software capable of complex surface modeling and ray-tracing, as well as high performance computing. The model was validated against measurements of the number of photoelectrons (PEs) generated in two silicon photomultipliers (SiPMs) located at the ends of 5 mm × 5 mm × 200 mm EJ-204 scintillation pillars with different surface finishes. It was also validated against the relative amplitudes and arrival time difference of the SiPMs’ signals. The model accurately predicts the measurements as function of the scintillation position along the pillars’ length with 2% mean-absolute-percentage error (MAPE) in the number of PEs, and 16% in the relative amplitudes. The root-mean-squared error (RMSE) in the arrival time difference is 0.114 ns. The model also predicts the experimentally observed higher scintillation light collection in pillars with smoother side surfaces. A proof-of-concept code of the model is available as open source.

Lead-Free Zero-Dimensional Organic-Copper(I) Halides as Stable and Sensitive X-ray Scintillators

Low-dimensional organic-metal halides are regarded as an emerging class of X-ray scintillation materials, but most of the discovered compounds are confronted with challenges of toxicity and instability. To address these challenges, we herein report two lead-free zero-dimensional (0D) hybrid halides, (Bmpip)2Cu2Br4 and PPh4CuBr2 single crystals, grown by the low-cost solution-processing method. By single-crystal X-ray diffraction refinement, the crystal structures of (Bmpip)2Cu2Br4 and PPh4CuBr2 were determined to be orthorhombic and monoclinic crystal systems, respectively. (Bmpip)2Cu2Br4 and PPh4CuBr2 show broadband orange and yellow emissions peaking at 620 and 538 nm, respectively. Different from the emission nature of the recent reported Cu-based halide hybrids, both (Bmpip)2Cu2Br4 and PPh4CuBr2 emit from excitons bound to defects featuring spin-allowed transition, enabling them to possess fast scintillation decay time of tens of nanoseconds, respectively. In particular, the (Bmpip)2Cu2Br4 single crystal has a high photoluminescence quantum yield of 48.2%, a high scintillation yield of 16,000 photons/MeV, and a low detection limit of 710 nGyair/s. Due to the combination of nontoxicity, long-term stability, and decent detection performance, (Bmpip)2Cu2Br4 could be regarded as a promising X-ray scintillator.

First Directional Measurement of Sub-MeV Solar Neutrinos with Borexino.

We report the measurement of sub-MeV solar neutrinos through the use of their associated Cherenkov radiation, performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso. The measurement is achieved using a novel technique that correlates individual photon hits of events to the known position of the Sun. In an energy window between 0.54 to 0.74MeV, selected using the dominant scintillation light, we have measured 10 887_{-2103}^{+2386}(stat)±947(syst) (68%confidence interval) solar neutrinos out of 19 904 total events. This corresponds to a ^{7}Be neutrino interaction rate of 51.6_{-12.5}^{+13.9} counts/(day·100 ton), which is in agreement with the standard solar model predictions and the previous spectroscopic results of Borexino. The no-neutrino hypothesis can be excluded with >5σ confidence level. For the first time, we have demonstrated the possibility of utilizing the directional Cherenkov information for sub-MeV solar neutrinos, in a large-scale, high light yield liquid scintillator detector. This measurement provides an experimental proof of principle for future hybrid event reconstruction using both Cherenkov and scintillation signatures simultaneously.

Zero‐Dimensional Luminescent Metal Halide Hybrids Enabling Bulk Transparent Medium as Large‐Area X‐Ray Scintillators

AbstractScintillators are critical in medical imaging, non‐destructive security screening, and space exploration applications. However, it still remains a challenge to achieve large‐area and high‐transparency scintillators by a low‐cost and easy‐to‐implement way. Herein, a large transparent medium with a diameter over 10 cm is prepared via a facile melt‐quenching strategy using a stoichiometric mixture of ethyltriphenylphosphonium bromide (ETPBr) and MnBr2 as raw materials. Benefiting from the crystallization behavior of high‐efficiency green‐emitting (ETP)2MnBr4 nanocrystals hybridized with amorphous phase in the transparent wafer, the (ETP)2MnBr4‐based transparent medium as a scintillator evidences a high transparency (over 80%, ranging from 500 to 800 nm), a high light yield of ≈35 000 ± 2000 photon per MeV, a low detection limit of 103 nGy S–1, and a competitive spatial resolution of 13.4 lp mm–1 for X‐ray imaging. This work offers a distinctive simple and fast melt‐quenching methodology to fabricate (ETP)2MnBr4 metal halide X‐ray scintillator wafer with large‐area and shape flexibility, excellent transparency, and high scintillation performance for the medical or industrial X‐ray imaging application.

Neutron transmission imaging with a portable D-T neutron generator

A portable fast-neutron imaging system is being developed to provide complementary information to field X-ray imaging. Applications include inspection of vehicles and infrastructure for corrosion, measurement of material levels in containers, and inspection of munitions and suspicious packages. While fast-neuron imaging generally provides lower imaging resolution compared to X-rays, fast-neutron interaction cross-sections have a weak dependence on material Z. This enables imaging of low-Z materials inside high-Z materials. Here, we discuss the limitations and current improvements in fast-neuron imaging. Limitations in portable fast-neutron imaging systems include low D-T neutron generator output, low light production in ZnS(Cu) imaging scintillators, low resolution due to scintillator thickness and D-T spot size, and digital-panel darknoise that varies in time and position and that can be 100× larger than the neutron signal. We have made improvements in these areas through development of a segmented high light yield scintillator, panel noise mitigation techniques, and testing of new high-output, small spot size D-T neutron generators. The segmented high light yield fast-neutron scintillator demonstrated 5× increase in light compared to ZnS(Cu). An additional 2× improvement in signal-to-noise was demonstrated with panel-noise mitigation techniques. Our MCNP calculations also show good agreement with neutron imaging results We have demonstrated improvements in fast-neutron imaging through development of a segmented high light yield neutron scintillator, mitigation of digital panel noise, and preliminary testing with new high-output, small spot size D-T neutron generators. We have also demonstrated good results modeling fast-neutron images and scatter effects using MCNP.

Optical, luminescence, and scintillation properties of advanced ZnWO4 crystal scintillators

Zinc tungstate (ZnWO4) crystal scintillators are promising detection material for the experiments searching for double beta decay, dark matter, and investigating rare alpha decays. An extended R&D was performed to develop advanced quality ZnWO4 crystal scintillators. The R&D programme included the selection of the initial materials, the variation of the compound stoichiometry, the application of single and double crystallization, and the annealing of the crystal boules. The optical transmittance of the produced boules was measured, and the luminescence under X-ray excitation in the temperature region from 85 K to room temperature was studied (thermally stimulated luminescence was measured till 350 K). The energy resolution and the relative scintillation pulse amplitude were measured with gamma-sources demonstrating high scintillation properties of the samples produced by single crystallization from deeply purified zinc and tungsten oxides, with stoichiometric composition, annealed in air atmosphere.

Statistical Analysis of Refractive and Diffractive Scintillation at High Latitudes

AbstractA comprehensive statistical analysis was performed on Global Positioning System scintillation data acquired at high latitudes from 2014 to 2017 after separating phase scintillation events originating from refraction and/or diffraction. Events exceeding a prescribed threshold were identified and analyzed statistically as a function of time, latitude, and propagation angle. The statistical analysis indicates that at high latitudes phase scintillation, which occurs more frequently than amplitude scintillation, is generated through refractive processes which can typically be treated as a stochastic Total Electron Content effect at high latitudes for Global Navigation Satellite System frequencies, and have the highest probability around magnetic noon in the Cusp. On average the phase scintillation index values decrease as a function of latitude, particularly during the first 6 hr of the evening. In addition, irregularities on the poleward side of the aurora are predominantly smaller than the Fresnel scale, when amplitude scintillation events are observed. By comparison, the mean of the phase scintillations on the equatorial side of the aurora, when amplitude scintillations are also present, indicates the existence of irregularities which are larger and smaller than the Fresnel scale. We also found that, during the day and at dusk, the spectral content of the irregularities apparently changes with decreasing off‐B Angle. No such increase is readily apparent at night or at dawn.

(Gd,Ce)2O3-Al2O3-SiO2 scintillation glass

Heavy scintillation glass of Gd2O3-Al2O3-SiO2 composition doped with Ce, combining high light yield and fast scintillation kinetics, was developed. The glass samples were prepared at 1500 °C by a melt-quench technique; the resulting glass was colorless and satisfactorily homogeneous. A photoluminescence study showed that a variety of sites for the Ce3+ ion stabilization exists in the glass, but the phenomenon was found less pronounced compared to BaO-Gd2O3-SiO2 glass. The glass has demonstrated ∼4 times faster scintillation kinetics and a minor drop of the light yield related to barium-gadolinium-silica glass, which makes this material of particular interest for large volume detectors in high energy physics, medical imaging, and other applications due to a low-cost production capability.

Flexible, High Scintillation Yield Cu3Cu2I5 Film Made of Ball‐Milled Powder for High Spatial Resolution X‐Ray Imaging

AbstractCu halide materials with low electronic dimension show great scintillation properties with high photoluminescence quantum yield (PLQY) and large Stokes shift, which can result in reabsorption‐free scintillators. However, there is still a need for a large‐scalable method to fabricate large amount of scintillation powder and large‐size scintillation films. In this regard, a high scintillation yield Cu3Cu2I5−PDMS flexible film utilizing ball‐milled Cu3Cu2I5 powder is developed. The ball‐milled Cu3Cu2I5 powder shows a high PLQY of 74.5%, narrow emission peak of 80 nm and good ambient stability, demonstrating the potential of ball‐milling method for large‐scale scintillator production. Furthermore, the Cu3Cu2I5−PDMS film shows even high PLQY exceeding 90%, which may be ascribed to the passivation effect of PDMS resulting in a little longer carrier lifetime. The flexible Cu3Cu2I5−PDMS film can further deliver high spatial resolution of 6.8 lp mm−1@0.2 MTF in X‐ray imaging and good stability under steady X‐ray illumination. This work demonstrates that the ball‐milling method could be an effective approach for large‐scale fabrication of low electronic dimensional scintillation materials.

Monte Carlo study of plastic rod scintillators for use in industrial computed tomography

Industrial gamma-ray computed tomography systems have found different applications and have become an important tool for non-destructive testing. In this work, high aspect ratio rod plastic scintillators were assessed for use in this type of tomography system. All analyses were performed using Monte Carlo simulation by geant4 toolkit. Validation of the results was done using a 50 cm rod plastic scintillator with a diameter of 5 cm. The results showed that the rod plastic scintillators can be employed in industrial tomography systems for scanning large objects. The spatial resolution of the detection system was estimated more than 1 cm. Finally, the simulated parameters of the selected rod plastic scintillator were compared with an identical NaI(Tl) rod scintillator to find a better understanding about its performance.