Composite Scintillators Research Articles

LuAG:Ce-PDMS composite scintillator films for X-ray imaging

The scintillator film, as a key element affecting X-ray detection imaging resolution, has attracted more and more attention. At present, it is mainly obtained by grinding and polishing of crystal or ceramic scintillators and film evaporation technology, with high cost, limited size and long preparation period. In this work, we propose a simple method to prepare scintillator films by blending (Lu0.995Ce0.005)3Al5O12 nano-powders and polydimethylsiloxane (PDMS), and characterize the uniformity, light absorption, photoluminescence, and X-ray excited luminescence (XEL) of these. The XEL results show that the prepared LuAG:Ce-PDMS composite scintillator films have a clear broadband emission in the region of 480 and 680 nm, which can be well coupled with silicon photodiodes. Its XEL integral intensity is 286% that of commercial BGO scintillators, and the spatial resolution is 25 lp/mm when the film thickness is 100 μm. All of those show the LuAG:Ce-PDMS composite scintillator films have a potential application in scintillator-based indirect-type X-ray imaging.

Radiation Resistance of Composite Scintillators Based on Grains of Oxide Single Crystals

Radiation Resistance of Composite Scintillators Based on Grains of Oxide Single Crystals

In Situ Fabrication of Cs3Cu2I5: Tl Nanocrystal Films for High-Resolution and Ultrastable X-ray Imaging.

Cs3Cu2I5 nanocrystals (NCs) are considered to be promising materials due to their high photoluminescence efficiency and X-ray hardness. However, the present strategy depends on tedious fabrication with excessive chemical waste. The evasive iodide ion dissociation, inadaptable ligand system, low stability, and relatively low light yield severely impede their applications. Herein, we develop an in situ fabrication strategy for a flexible and large-area Tl-doped Cs3Cu2I5 NC-polymer composite scintillation film with a high light yield (∼48800 photons/MeV) and improved stability. Tween 80 and phosphinic acid successfully inhibit the oxidation of iodide ions, and the films can be stored for at least six months. As a result, a high spatial resolution of 16.3 lp mm-1 and a low detection limit of 305 nGyair s-1 were achieved. A radioluminescence intensity of >80% was maintained after a total irradiation dose of 604.8 Gy. These results indicate the promising application of these copper halide NCs in low-cost, flexible, and high-performance medical imaging.

Development of a gamma-ray scintillation detector based on blue-emitting oligomers and ZnO nanoparticles

We report the design of flexible, inexpensive, enduring, and efficient composite scintillation based on polystyrene (PS)/blue-emitting conjugated oligomer (CO)/ZnO nanoparticles. The oligomer utilized was 1,4-bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (ADS086BE or BECV-DHF). Polystyrene was used as a matrix, and ZnO NPs were used as γ-ray stoppers. The formation of blends was analyzed using X-ray diffraction (XRD) and EDS. Field emission scanning electron microscopy (FE-SEM) images showed micron-sized bun (nearly square)-shaped domains, noodle-like structures, and submicron-sized domains with square-shaped nanosized domains for PS, PS/BECV-DHF, and PS/BECV-DHF/ZnO scintillator samples. The optical properties show that PS/BECV-DHF and PS/BECV-DHF/ZnO had absorption peaks at 350 and 375 nm and fluorescence peaks at 455 nm and 475 nm, respectively. The fabricated scintillators were coupled to the R6094 Hamamatsu Photomultiplier and gamma data acquisition system based on a multichannel analyzer (MCA). Gamma spectra were measured via three gamma-ray sources, Am-241, Cs-137 and Co-60. The results show better scintillation counting in the fabricated PS/BECV-DHF/ZnO than PS/BECV-DHF and the PS sample reference samples.

Positive Effects of a Perovskite Film on the Radioluminescence Properties of a ZnO:Ga Crystal Scintillator.

To improve the radioluminescence (RL) performance of ZnO:Ga (GZO) crystal scintillators and overcome the challenge of their self-absorption, we proposed a two-layer composite scintillator consisting of a GZO wafer and a 70 nm lead halide perovskite film(CsPbBr3, CH3NH3PbBr3). The effects of the perovskite film on the RL properties were studied. The results showed that the perovskite quantum dot film substantially changed the RL spectrum of GZO and prevented self-absorption. The RL of the samples were enhanced by 66% to 151% through the photoluminescence (PL) of the perovskite film, while the energy-resolving power and spatial-resolving power were maintained at the same level as that of GZO image converters. The present experiments and discussions confirmed that the perovskite film improved the RL, and this study suggests a new wavelength regulation method among scintillators, converters, and back-end optical devices. The applications of perovskites in the field of radiation detection and imaging have been extended.

Composite Detectors Based on Single-Crystalline Films and Single Crystals of Garnet Compounds.

This manuscript summarizes recent results on the development of composite luminescent materials based on the single-crystalline films and single crystals of simple and mixed garnet compounds obtained by the liquid-phase epitaxy growth method. Such composite materials can be applied as scintillating and thermoluminescent (TL) detectors for radiation monitoring of mixed ionization fluxes, as well as scintillation screens in the microimaging techniques. The film and crystal parts of composite detectors were fabricated from efficient scintillation/TL materials based on Ce3+-, Pr3+-, and Sc3+-doped Lu3Al5O12 garnets, as well as Ce3+-doped Gd3−xAxAl5−yGayO12 mixed garnets, where A = Lu or Tb; x = 0–1; y = 2–3 with significantly different scintillation decay or positions of the main peaks in their TL glow curves. This work also summarizes the results of optical study of films, crystals, and epitaxial structures of these garnet compounds using absorption, cathodoluminescence, and photoluminescence. The scintillation and TL properties of the developed materials under α- and β-particles and γ-quanta excitations were studied as well. The most efficient variants of the composite scintillation and TL detectors for monitoring of composition of mixed beams of ionizing radiation were selected based on the results of this complex study.

Confinement of all-inorganic perovskite quantum dots assembled in metal-organic frameworks for ultrafast scintillator application.

Nucleation and growth of quantum dots (QDs) are thermodynamic processes driven by the total Gibbs free energy change (ΔG). We discuss the nucleation and growth theory of perovskite quantum dots (PeQDs) inside a metal-organic framework (MOF) as a strong constraint framework, which can effectively confine the size of QDs below 3 nm and achieve a scintillator with an ultra-fast transient lifetime of fluorescence. Therefore, based on the requirements for the optical properties of ultra-fast scintillation materials, two kinds of suitable MOFs (UiO-67-bpy and MIL-101(Cr)) were selected for synthesis. The method of 'ship-in-bottle' was adopted to embed perovskite quantum dots CsPbBrCl2 into MOF cages to form PeQDs@MOF composite materials, which is different from the one-pot method. In order to further improve the stability of PeQDs@MOF, polystyrene was used to cure the composite scintillator, which can resist exposure to UV light and withstand the ISO level 4 test, with the fastest transient lifetime of 2.13 ns and a fluorescence emission wavelength of 445 nm.

INFLUENCE OF RADIATION CONDITIONS ON CRACKING OF COMPOSITE SCINTILLATORS

The article analyzes two main hypotheses describing the cracking of a composite scintillator in the irradiation zone. This is the "temperature" and "radiation-chemical" hypothesis of cracking. The analysis is based on experi-mental data that we obtained by irradiating scintillators and the results of model chemical experiments.

INFLUENCE OF RADIATION CONDITIONS ON CRACKING OF COMPOSITE SCINTILLATORS

The article analyzes two main hypotheses describing the cracking of a composite scintillator in the irradiation zone. This is the "temperature" and "radiation-chemical" hypothesis of cracking. The analysis is based on experi-mental data that we obtained by irradiating scintillators and the results of model chemical experiments.

Enhanced luminescence of CsPbBr3 nanocrystals-glass composite scintillators based on Ce3+-doped borosilicate glass

CsPbBr3 nanocrystals-glass composite scintillators based on Ce3+-doped borosilicate glass were prepared by melt-quenching method with further heat-treatment. Incorporating Ce3+ into borosilicate glasses matrix, highly enhanced green emission was observed under 365 nm ultraviolet and X-ray excitation. The transmittance of the prepared CsPbBr3 nanocrystals-glass is as high as 80% at 527 nm, fluorescence lifetime is 21.6 ns, and the luminescent quantum efficiency reaches up to 28% after thermal treatment (550 °C, 12 h). Compared with undoped CsPbBr3 nanocrystals-glass, the X-ray excited luminescence intensity of Ce3+ doped CsPbBr3 nanocrystals-glass is around 190%, which indicates that the issue of absorbing ray energy in glass matrix can be effectively solved by incorporation of Ce3+ ions.

GYAGG/6LiF composite scintillation screen for neutron detection

Composite scintillation screens on a base of Gd1.2Y1.8Ga2.5Al2.5O12:Ce (GYAGG) scintillator have been evaluated for neutron detection. Besides the powdered scintillator, the composite includes 6LiF particles; both are merged with a binder and deposited onto the light-reflecting aluminum substrate. Results obtained demonstrates that screens are suitable for use with a silicon photomultiplier readout to create a prospective solution for a compact and low-cost thermal neutron sensor. Composite GYAGG/6LiF scintillation screen shows a pretty matched sensitivity and γ-background rejection with a widely used ZnS/6LiF screens however, possesses forty times faster response.

Development of CuI:Cl-PS composite scintillator

A promising composite scintillator for used in ultrafast X-ray detection was successfully developed by compounding Cl-doped CuI phosphor with polystyrene (PS) (CuI:Cl-PS), and its crystal structure and luminescence characteristics were investigated in detail. The CuI:Cl-PS composite scintillator only exhibited an intense near-band-edge (NBE) luminescence with a decay time of sub-nanosecond, and the slow luminescence of CuI was entirely suppressed under the excitation of ultraviolet light or X-ray. Furthermore, the intensity of the ultrafast NEB emission for the composite scintillator was not basically deteriorated after storage in air at room temperature for six months. It is expected that the CuI:Cl-PS composite scintillator demonstrates a great potential application in ultrafast hard X-ray detection or imaging.

The ways of characteristics improvement for alpha–beta detectors on ZnSe based composite scintillators

The design and technological scheme of alpha particle detectors based on crystal granules of ZnSe–Al were developed. We have found that the ZnSe–Al semiconductor scintillator has a number of advantages compared to the ZnS–Ag namely the terms of sensitivity and the ability to obtain scintillation powder of the desired dispersion. The results of tests of sensitivity, homogeneity and ability to registration simultaneously both alpha and beta particles are presented. The measured sensitivity of detectors towards alpha particles (239Pu source) was more than 0.3 pulse per sec/Bq (pps/Bq) and towards beta particles (90Sr-90Y source) was more than 0.25 pps/Bq. The light output inhomogeneity of scintillators within the area did not exceed 2%. This makes it possible to produce the large area detectors.An algorithm for separating the scintillation signal from alpha and beta particles during their simultaneous registration is proposed. Potentially, statistical algorithms will allow 100% separation of alpha and beta particle pulses.

High-Efficiency Down-Conversion Radiation Fluorescence and Ultrafast Photoluminescence (1.2 ns) at the Interface of Hybrid Cs4PbBr6-CsI Nanocrystals.

The research of fast scintillators in positron emission tomography and other applications based on time-of-flight technology promotes the development of radiation detection. However, because of the current lack of efficient and fast carrier radiation recombination pathways, the research on scintillator radioluminescence (RL) still faces severe challenges. Here, we propose an effective interface carrier transport mechanism: CsI:Na crystal and Cs4PbBr6 nanocrystals (NCs) interface to form a new phase and a continuous heterostructure, providing an effective channel for X-ray excited carrier transfer to Cs4PbBr6. Then, the excited carriers realize efficient recombination luminescence through the self-trapped excitons inside Cs4PbBr6. On the basis of this mechanism, the heterostructure composite scintillator composed of CsI:Na/Cs4PbBr6 exhibits high-efficiency radiant fluorescence and an ultrafast photoluminescence (PL) decay time of 1.22 ns. The effective interface carrier transport shown in this work provides an optimization idea that can be used for reference in the research of fast scintillators.

Development of Composite Scintillators Based on the LuAG: Pr Single Crystalline Films and LuAG:Sc Single Crystals

The scintillation properties of novel type of composite scintillator based on Lu3Al5O12:Pr (LuAG:Pr) single crystalline film (SCF) and LuAG:Sc substrate grown by the liquid-phase epitaxy method are considered in this work. The registration of α-particles and γ-quanta in such types of composites occurs by means of separation of the scintillation decay kinetics of SCF and crystal parts, respectively. Namely, under excitation by α-particles of 241Am (5.5 MeV) source and γ-quanta of 137Cs (662 keV) source, the large differences in the respective scintillation decay kinetics and decay time values tα and tγ are observed for the LuAG:Pr SCF/LuAG:Sc SC composite scintillator with various film thicknesses. Furthermore, the best tγ/tα ratio above 4.5 is achieved for such types of epitaxial structure with SCF and substrate thicknesses of 17 μm and about 0.5 mm, respectively. The development types of composite scintillators can be successfully applied for simultaneous registration of α-particles and γ-quanta in the mixed radiation fluxes.

Highly Luminescent Zero-Dimensional Organic Copper Halides for X-ray Scintillation

The present work reports highly efficient flexible and reabsorption-free scintillators based on two zero-dimensional (0D) organic copper halides (TBA)CuX2 (TBA = tetrabutylammonium cation; X = Cl, Br). The (TBA)CuX2 exhibit highly luminescent green and sky-blue emissions peaked at 510 and 498 nm, with large Stokes shifts of 224 and 209 nm and high photoluminescence quantum yields (PLQYs) of 92.8% and 80.5% at room temperature for (TBA)CuCl2 and (TBA)CuBr2 single crystals (SCs), respectively. Interestingly, above room temperature, their PLQYs increase with temperature and reach near unity at 320 and 345 K for (TBA)CuCl2 and (TBA)CuBr2, respectively. The excellent properties originate from self-trapped excitons (STEs) in individual [CuX2]- quantum rods, which is demonstrated by the temperature-dependent PL, ultrafast transient absorption (TA) combined with density functional theory (DFT) calculations. The (TBA)CuX2 scintillators show bright radioluminescence (RL), impressive linear response to dose rate in a broad range, and high light yields. Their potential application in X-ray imaging is demonstrated by using (TBA)CuX2 composite scintillation screens. Importantly, flexible scintillators are demonstrated to be superior than flat ones for imaging nonplanar objects by conformally coating, which produce accurate images with negligible distortion.

Test beam study of SiPM-on-tile configurations

Light yield and spatial uniformity for a large variety of configurations of scintillator tiles were studied. The light from each scintillator was collected by a Silicon Photomultiplier (SiPM) directly viewing the produced scintillation light (SiPM-on-tile technique).The varied parameters included tile transverse size, tile thickness, tile wrapping material, scintillator composition, and SiPM model.These studies were performed using 120 GeV protons at the Fermilab Test Beam Facility. External tracking allowed the position of each proton penetrating a tile to be measured. The results were compared to a GEANT4 simulation of each configuration of scinitillator, wrapping, and SiPM.

HETEROSTRUCTURED ORGANIC SCINTILLATORS WITH A HIGH PULSE-SHAPE DISCRIMINATION CAPABILITY FOR RADIOECOLOGY PROBLEMS

Studies of the relative Light output and optical transmission of organic composite scintillators with different grain sizes were performed. The research results showed that for samples with grains 0.06…0.3 mm in size, in contrast to the samples with larger grains, the relative light output and optical transmission are lower.

Improvement in Plastic Scintillator with Loading of BaFBr:Eu²⁺ Radioluminescence Phosphor

This article describes a new concept of developing a composite plastic scintillator (PS) with better light out and detection efficiency of ionizing radiations by loading high Z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> radioluminescence (RL) phosphor powder. Gamma-ray interaction in PSs has been enhanced due to increased photoelectric absorption in the loaded BaFBr:Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> phosphor powder. RL BaFBr:Eu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> powder has been synthesized by a high-temperature solid-state diffusion method in reducing atmosphere. Polystyrene-based PS sheets of 250±50 μm thickness have been prepared with 2.5-diphenyl oxazole (PPO) and 1.4-bis(5-phenyl-2-oxazolyl) benzene (POPOP) as primary and secondary fluors, respectively, mixed with the synthesized phosphor powder in different weight percentages. Radiation detection properties of the composite PS have been studied for alpha, beta, neutron, and gamma radiations of different energies. The composite PS sheet loaded with 20 wt% of phosphor powder showed maximum intensity for RL and photoluminescence (PL). Studies also confirmed a significant increase in the radiation detection efficiency in composite PS for various energies of beta and gamma rays. The lifetime measurement of the composite PS showed same nanosecond lifetime which is appropriate for fast counting and matches closely with the PS without loading. Pulse height analysis for various ionizing radiations of different energies confirmed significant improvement in the detection efficiency of loaded PSs.

Effect of high Z materials loading in the performance of polystyrene-based thin-film plastic scintillators

The paper describes the effect of high effective atomic number (Zeff) materials loading in polystyrene based thin-film Plastic Scintillators (PS). Thin plastic scintillator sheets have been loaded with high Z materials such as BaFBr:Eu, Gd2O2S:Tb, Gd2O3, BaF2, CeO2 and Bi2O3. Polystyrene based PS sheets of 250 ± 50 μm thickness have been prepared by dissolving predetermined quantities of polystyrene, 2,5-Diphenyloxazole (PPO) and 1,4-bis(5-phenyl-2-oxazolyl) benzene (POPOP) in the p-xylene solvent. High Zeff material powders of 23μm size are mixed in the plastic scintillator solution and coated over the cellulose acetate-based transparency sheets. The dried films are peeled off, and their photoluminescence, radioluminescence, pulse height spectrum and response to alpha, beta, gamma and neutron radiations are studied by adopting suitable methods. The high Zeff materials for loading in PS are selected based on their physical properties like refractive index, bandgap, Zeff, Photoluminescence (PL) properties. While the composite scintillator loaded with 14.3 wt% of BaFBr:Eu2+ showed significant increase compare to other high Z materials. The loading concentration has been optimized as 14.3 wt% from the BaFBr:Eu2+ studies. Most of the composite scintillators showed improvement in radioluminescence and pulse height spectra for different radiations.