Search Results (112)

Single-crystal scintillators are used to convert ionizing radiation into optical photons in various medical imaging applications. A promising material is cerium (Ce)-doped gadolinium aluminum gallium garnet (GAGG:Ce) inorganic scintillator. Three GAGG:Ce 10 × 10 × 10 mm³ crystals of different light yield (LY) were exposed in X-ray tube voltage range of 50–140 kVp. Their absolute luminescence efficiency (AE) was experimentally calculated. A theoretical model was employed to simulate the propagation of photons traversing through the crystal mass. The model was utilized to estimate the detector quantum gain (DQG) and the percentage of transmission of the optical photons per elementary thickness $\mathrm{k}$. Their suitability with various optical photodetectors was evaluated by means of the spectral matching factor (SMF). GAGG:Ce presented AE values reaching 60.72 E.U. (where 1 E.U. = 1 μWm⁻²/(mRs⁻¹)) at 140 kVp. The parameter $\mathrm{k}$ ranged from 0.99973 to 0.99980. GAGG:Ce emission spectrum is highly compatible with charged-coupled devices (CCD), complementary metal-oxide semiconductors (CMOS) and silicon photomultipliers (SiPM). These findings may further consolidate the use of GAGG:Ce and could contribute to the future optimization of this inorganic scintillator when applied in X-ray imaging modalities, or as a radiation detector. Full article

Copper(I) halides are promising for X-ray scintillation owing to high luminescence and solution processability, but their poor stability limits practical use. Here we report a zero-dimensional coordinative cluster, (DPPM)₂Cu₄I₄ (DPPM = bis (diphenylphosphino) methane), prepared by a simple anti-solvent crystallization that emits bright orange light with an absolute photoluminescence quantum yield of 91.11%. Spectroscopic analysis (long lifetime, large Huang–Rhys factor) indicates self-trapped-exciton dominated radiative recombination. The cluster shows outstanding thermal (stable to ≈362 °C), solvent (stable after 30 d in H₂O, EA, EtOH, IPA) and air stability (>60 d), addressing common durability issues of copper(I) halides. Using an in situ growth method, microcrystals of (DPPM)₂Cu₄I₄ were uniformly incorporated into a thermoplastic polyurethane (TPU) matrix to form flexible scintillator films. The composite exhibits a high light yield of 17,064 photons MeV⁻¹ and a spatial resolution of 14 lp mm⁻¹, highlighting its great potential for practical X-ray imaging applications. Full article

The search for new bright scintillators with performance close to ideal is the target for many research centers worldwide. This paper presents advanced bright thallium (Tl)-based K₂PtCl₆-type intrinsic scintillators for detection and imaging applications. Dopant-free Tl-based compounds of Tl₂HfX₆ and Tl₂ZrX₆ (X = Cl, Br, or mixed halogens) that were investigated, grown, and published previously are now scaled up to one-inch-diameter crystals. Energy resolutions of 4.1% for Tl₂HfCl₆, 4.4% for Tl₂ZrCl₆, 4.8% for Tl₂Hf(Cl,Br)₆, and 4.1% for Tl₂Zr(Cl,Br)₆, as well as light yields of 22,300 ph/MeV for Tl₂HfCl₆, 38,500 ph/MeV for Tl₂ZrCl₆, 19,000 ph/MeV for Tl₂Hf(Cl,Br)₆, and 39,900 ph/MeV for Tl₂Zr(Cl,Br)₆, are measured. These crystals have generally linear responses to gamma-rays above 100 keV. Because of their many favorable attributes, these novel crystals will be beneficial in many gamma-ray detector applications that require better physical densities, Z_eff values, energy resolutions, and relative detection efficiency than NaI:Tl, without the constraints of light yield and decay time constants. Full article

This paper targets the air-to-ground (A2G) data backhaul scenario of UAVs and proposes a communication system based on coherent optical zero-padding orthogonal frequency division multiplexing (CO-ZP-OFDM), which unifies atmospheric turbulence scintillation, pointing errors, and Doppler frequency shift into a composite channel model. The system employs the Gamma-Gamma (GG) distribution to describe turbulence-induced intensity fluctuations, a Gaussian beam truncation model to characterize pointing errors, and a dual-pilot method to estimate and compensate the Doppler frequency offset. Furthermore, on a polarization-time-frequency (PTF) three-dimensional orthogonal grid pilot structure, we derive theoretical mean square error (MSE) expressions for the zero-forcing (ZF) and minimum mean square error (MMSE) estimators, and analyze their MSE characteristics under the proposed pilot model. Simulation results show that, under moderate turbulence, the shrinkage factor of the MMSE estimator yields only about $0.4$ dB MSE reduction over ZF at $\mathrm{SNR}=10$ dB, whereas the full receiver pipeline that combines coherence-bandwidth pilot averaging with the MMSE and maximum ratio combining (MRC) equalizer reduces the empirical MSE by approximately 15 dB. The bit error rate (BER) performance tests indicate that, under turbulence-free conditions with ideal channel estimation, the system can reduce the BER below ${10}^{-4}$ at an SNR of approximately 12 dB. Under strong turbulence conditions with MMSE channel estimation, the SNR cost required to achieve a BER of ${10}^{-3}$ is approximately 18 dB, which corresponds to a 3 to 5 dB BER gain over the ZF baseline at the same SNR. Further simulation analysis shows that the average pointing loss is highly sensitive to the angular jitter at the 1 km link distance: an angular jitter of 1 mrad incurs about 18 dB of loss, and a sub-mrad pointing stability (i.e., ${\sigma }_{\mathrm{jit}}<0.062$ mrad) is required to keep the average pointing loss below 1 dB. Full article

Alpha/beta (α/β) pulse shape discrimination (PSD) in liquid scintillation counting (LSC) is fundamentally limited by the charge comparison method (CCM) at low energies, where the entire tritium (³H) beta spectrum resides (0–18.6 keVee). The CCM figure-of-merit drops below 0.6 in this region, rendering it inadequate for simultaneous tritium and natural uranium alpha monitoring in nuclear power plant (NPP) liquid effluents. We present a one-dimensional convolutional neural network (1D-CNN) trained on an 80,000-waveform physics-based simulation dataset using established scintillation parameters for Ultima Gold AB. The proposed network achieves 97.4% overall classification accuracy and an area under the receiver operating characteristic curve (AUC) of 0.9981 on the held-out test set, representing improvements of 13.8 percentage points and 0.046 AUC over CCM. In the critical 0–18.6 keVee region, CNN accuracy exceeds 95% compared to below 60% for CCM—a greater than 35 percentage point improvement. Pulse amplitude discrimination (PAD), evaluated as a preliminary screening method, exhibits a 6.3% alpha spillover rate into the beta window, exceeding the regulatory limit of 3%. Gradient-weighted class activation maps (Grad-CAM) confirm that the network exploits physically meaningful pulse features rather than simulation artefacts. A comprehensive background suppression strategy combining dual-SiPM coincidence (24× reduction), anti-coincidence guard detector (5.8× reduction), composite passive shielding (10× reduction), and CNN-assisted discrimination reduces the system equivalent background to 1.83 ± 0.12 cpm, yielding a tritium minimum detectable activity (MDA) of 0.21 Bq/mL (10 mL sample, 30 min count), which satisfies the GB 14587 reference limit of 0.5 Bq/mL. After 8-bit post-training quantisation, the model achieves sub-microsecond inference latency on an embedded Xilinx Artix-7 Field-programmable gate array(FPGA), enabling real-time deployment in portable online monitoring systems. Full article

Pixelated detectors based on inorganic scintillation materials are widely used in radiation detection systems for medical imaging and many other fields of science and technology. A substantial application is X-ray scanning using flat-panel detectors (FPDs) for both fluorography and mammography. In this article, the detection properties of the monolithic planar ceramic scintillation elements are reported for the first time. A high-light yield (Gd,Y)₃Al₂Ga₃O₁₂:Ce,Mg garnet-type scintillation material was used to form square-shaped pixels, while a material of similar composition was used as a substrate. Green bodies were successfully fabricated by a digital light processing (DLP) 3D printing method. Subsequent debinding and pressureless high-temperature sintering resulted in composite elements consisting of two layers with different chemical compositions. The lower bulk layer consisted of transparent, non-luminescent garnet, whereas the upper pixelated layer, with pixel dimensions of 230 × 230 µm, was made of scintillation material. The spatial resolution of the matrices under UV light and alpha-particle excitation was evaluated. It was confirmed that the spatial resolution of the matrices produced by the developed technology is approximately 0.4 times the pixel size. The proven ability of the integrated technology of inorganic scintillation matrix production opens the way for future improvement in spatial resolution through optimizing the printed pixel dimensions. Full article

In this work, we report the fabrication and characterization of single-film and double-film composite epitaxial garnet structures based on single-crystalline films (SCFs) and bulk single-crystal (SC) scintillators for enhanced α–γ discrimination in mixed radiation fields. These composite scintillators consist of TbAG:Ce and YAG:Ce SCFs grown by liquid-phase epitaxy (LPE) on Czochralski-grown Gd₃Ga_2.5Al_2.5O₁₂ (GAGG:Ce) bulk SC substrates. Single- and double-film architectures were designed to optimize the energy absorption and pulse-shape discrimination (PSD) performance for low-penetrating α-particles and high-energy γ-rays. Energy calibration was performed using different γ-ray sources (⁵⁷Co, ⁵¹Cr, and ¹³⁷Cs), enabling the conversion of detector signals to a calibrated electron-equivalent energy scale (keVee). Integration gates were systematically optimized, yielding maximum figures of merit (FOM) of 1.4 for the GAGG:Ce SC substrate, 1.9 for the single-film composite, and 5.0 for the double-film composite, demonstrating a progressive improvement in α–γ discrimination with increasing structural complexity. Two-dimensional PSD density maps reveal well-separated α and γ events, with the highest separation observed for the double-film composite. These results indicate that the engineering of LPE-grown composites provides tunable scintillation decay profiles, enhanced temporal separation, and increased light yields, making them promising candidates for applications such as mixed radiation field detection, dosimetry, and radiation monitoring. Full article

Cs₃Cu₂I₅ single crystals are regarded as promising next-generation scintillators due to their large Stokes shift and low self-absorption characteristics. However, the cost-effective solution growth method faces critical challenges: the instability of colloidal precursors in solutions and the severe oxidation of Cu⁺ during crystal growth. This study innovatively introduces yttrium chloride (YCl₃) as a dual-functional additive to address both issues simultaneously. The hydrolysis of YCl₃ creates a controlled acidic environment, effectively suppressing the oxidation of Cu⁺; meanwhile, it enhances the stability of colloidal precursors by significantly increasing their surface charge and narrowing the particle size distribution. These synergistic effects enable the rapid growth (approximately 100 h) of near-centimeter-sized Cs₃Cu₂I₅ single crystals with high crystallinity, without the need for inert gas protection. The optimized crystals exhibit exceptional performance: a photoluminescence quantum yield (PLQY) of 93.22% ± 0.47%, a scintillation decay time of 210.04 ns, and a light yield of ~738.14 pe/MeV. This YCl₃-mediated growth strategy establishes an efficient approach for the solution-based synthesis of high-quality Cs₃Cu₂I₅ single crystals, holding great significance for advancing high-sensitivity, environment-stable radiation detection applications such as medical diagnostics and nuclear safety monitoring. Full article

Hybrid metal-halide scintillators are promising for X-ray imaging, but direct fabrication of patterned arrays with high spatial precision remains challenging. Here, we report a laser-induced in situ crystallization strategy for constructing pixelated scintillator arrays from a melt-processable manganese(II) bromide glass precursor, (BuTPP)₂MnBr₄ (BuTPP⁺, butyltriphenylphosphonium). The (BuTPP)₂MnBr₄ undergoes low-temperature glass formation and can be selectively recrystallized under femtosecond laser irradiation, enabling programmable spatial patterning. Structural analyses confirm the recovery of the crystalline phase after laser writing, while photophysical measurements show markedly enhanced photoluminescence and radioluminescence compared with the glassy state. Benefiting from efficient X-ray-to-light conversion and precise array definition, the patterned scintillators exhibit a high light yield of 24,600 photons MeV⁻¹, an X-ray detection limit of 4.89 µGy_air s⁻¹, and a spatial resolution of 10 lp mm⁻¹. This work establishes the laser-induced in situ crystallization strategy as an effective route to integrated hybrid scintillator arrays and offers a versatile platform for customizable and low-temperature processed X-ray imaging devices for imaging uses. Full article

With the growing global emphasis on nuclear reactor decommissioning, reliable thermal neutron detection has become increasingly important for ensuring critical safety and for the identification of fuel debris and radioactive waste. In this context, this study developed and characterized a Ce-doped CaF₂/⁶LiF (Ce:CaF₂/LiF) eutectic scintillator for thermal neutron detection with Ce concentrations ranging from 0.5 to 10 mol%. The eutectic samples were grown by the melt-solidification method, and their crystalline properties were evaluated using inductively coupled plasma mass spectrometry, X-ray diffraction, scanning electron microscopy, and field-emission electron probe microanalysis. Radioluminescence, photoluminescence, transmittance, scintillation decay, and pulse-height measurements were conducted to assess their scintillation performance. Structural characterization revealed a well-defined eutectic microstructure together with several Ce-rich phases. The results of the effective neutron sensitivity demonstrated that the Ce concentration was effectively optimized based on the effective neutron sensitivity: the sample with 1 mol% Ce exhibited the highest neutron sensitivity (approximately 1.5 times that of a Ce:LiCaAlF₆ single crystal) and a 1.6-times higher neutron-induced light yield, while maintaining a fast effective decay time of 400 ns. These findings suggest that the Ce:CaF₂/LiF eutectic is a promising candidate for high-performance thermal-neutron scintillators for applications in nuclear decommissioning. Full article

A compact, in situ beta-spectroscopy approach for real-time monitoring of Strontium-90 (Sr-90) in contaminated groundwater has been investigated. Two inorganic scintillators, CaF₂(Eu) and ZnSe(Al,O), were coupled to silicon photomultipliers (SiPMs) and evaluated experimentally using custom front-end electronics. This was also modelled with Monte Carlo simulations using the Geant4 toolkit. Although simulations correctly predicted ZnSe(Al,O) has an advantage due to its higher light yield and optical transport, experimental measurements additionally revealed practical limitations of the readout electronics which were not captured in the simulation model. ZnSe(Al,O) showed excellent agreement with the simulated detector response (R² ≈ 0.86; ${\chi }^2$/NDF ≈ 27). It also attains a higher relative detection efficiency (∼61.5%), yielding faithful capture of the composite Sr-90/Y-90 spectrum with only minor suppression at the extreme high-energy tail. CaF₂(Eu) exhibits a deficit at low-mid energies and an apparent enhancement in the high-energy tail. This is consistent with threshold and photon-statistics losses and leads to poorer agreement with simulation (${\chi }^2$/NDF ≈ 179) and lower overall efficiency (∼22.7%). These findings identify ZnSe(Al,O) as the stronger candidate for an underwater, in situ Sr-90 beta-spectroscopy system and motivate targeted optimisation of SiPM coupling and crystal-edge reflectivity in future designs. Full article

The escalating prevalence of counterfeiting and forgery has imposed unprecedented demands on advanced anti-counterfeiting technologies. Traditional luminescent materials, relying on single-mode or static emission, are inherently vulnerable to replication using commercially available phosphors or simple spectral blending. Multimode luminescent materials exhibiting excitation wavelength-dependent emission offer significantly higher encoding capacity and forgery resistance. Herein, we report the colloidal synthesis of lanthanide-doped Cs₂ZrCl₆ nanocrystals (Ln³⁺ = Tb, Eu, Pr, Sm, Dy, Ho) via a robust hot-injection route. These nanocrystals universally exhibit efficient host-to-guest energy transfer from self-trapped excitons (STEs) under 254 nm, yielding sharp characteristic Ln³⁺ f–f emission alongside the intrinsic broadband STE luminescence. Critically, Tb³⁺ enables direct 4f → 5d excitation at ~275 nm, while Eu³⁺ introduces a low-energy Eu³⁺ ← Cl⁻ LMCT band at ~305 nm, completely bypassing STE emission. Due to their multimode luminescent characteristics, we fabricate a triple-mode anti-counterfeiting label displaying different colors under different types of excitation. These findings establish a breakthrough excitation-encoded multimode platform, offering potential applications for next-generation photonic security labels, scintillation detectors, and solid-state lighting applications. Full article

Cerium (Ce³⁺)-doped gadolinium orthoborate (GdBO₃) phosphor powders were synthesized via an aqueous sol–gel route, with systematic variation in solution pH (2, 5, and 8) and annealing temperature (600–1200 °C, in 100 °C increments) to investigate their influence on structural, optical, and scintillation properties. The materials were comprehensively characterized using thermogravimetric and differential thermal analysis (TG–DTA) to assess thermal behavior, X-ray diffraction (XRD) for crystal structure determination, Fourier-transform infrared spectroscopy (FTIR) for vibrational analysis, and both photoluminescence (PL) and radioluminescence (RL) spectroscopies to evaluate optical and scintillation performance. All samples crystallized in the hexagonal GdBO₃ vaterite phase (space group P6₃/mcm). The PL and RL emission spectra were consistent with the Ce³⁺ 5d–4f transitions, and scintillation yields under X-ray excitation were quantified relative to a standard Gadox phosphor. A decrease in photoluminescence quantum yield (PLQY) was observed at annealing temperatures above 800 °C, which is attributed to the incorporation of Ce³⁺ into the host lattice. Scintillation decay profiles were recorded, enabling extraction of timing kinetics parameters. Overall, the results reveal clear correlations between synthesis conditions, structural evolution, and luminescence behavior, providing a rational basis for the optimization of Ce³⁺-doped GdBO₃ phosphors for scintillation applications. Full article

Scintillator-SiPM Particle Detectors (SSPDs) are compact, low-power devices with applications including particle physics, underground tomography, cosmic-ray studies, and space instrumentation. They are based on a prism-shaped scintillator with corner-mounted SiPMs. Previous work has demonstrated that analytic algorithms based on a physical model of light propagation can reconstruct particle impinging positions and tracks and estimate deposited energy and Linear Energy Transfer (LET) with moderate accuracy. In this study, we enhance this approach by applying machine learning (ML) methods, specifically gradient boosting techniques, to improve the accuracy of spatial location and energy deposition estimation. Using the GEANT4 simulation toolkit, we simulated cosmic muons and energetic oxygen ions traversing an SSPD, and we trained XGBoost and LightGBM models to predict particle impinging positions and deposited energy. Both algorithms outperformed the analytic baseline. We further investigated hybrid strategies, including hybrid boosting and probing. While hybrid boosting provided no significant improvement, probing yielded measurable gains in both position and LET estimation. These results suggest that ML-driven reconstruction provides a powerful enhancement to SSPD performance. Full article

In this study, a two-dimensional gamma-ray source localization system using a mesh array of plastic scintillating fibers and an artificial neural network is presented. The system covers a 200 cm by 100 cm area using SCSF-78 multi-cladded fibers. A novel U-shaped fiber topology connects both fiber ends to one side, requiring only two data-acquisition systems. Silicon photomultiplier arrays measure fast time-of-flight under optimized operating conditions to maximize signal yield. An independent artificial neural network model map measured time-of-flight values to spatial coordinates, compensating for systematic non idealities. Performance was validated using a Cesium-137 source at 20 random test positions. The artificial neural network method achieved a mean full-scale error of 4.6%. This demonstrated a 79.34% accuracy improvement over direct theoretical calculation, which had a mean full-scale error of 22.5%. The system showed consistent performance, achieving a two-dimensional standard deviation of 0.492 cm during repeatability assessment. This methodology provides a practical, efficient approach to two-dimensional radiation source localization suitable for real time monitoring and contamination mapping. Full article