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We report on the development of the first-ever inorganic radiation-hard moisture-insensitive large volume spectroscopic semiconductor-based scintillator with less than 2 ns decay time and light yields as high as 8000 ph/MeV. Despite extensive research into scintillator materials, the quest for an ideal scintillator combining ultrafast decay times (akin to BaF2 and Yb-doped scintillators such as Lu2O3:Yb), high light yields (exceeding 2000 photons per MeV), spectroscopic capabilities, and exceptional radiation hardness remain unfulfilled. In this study, we demonstrate and report for the first time the viability of large-volume (up to 20 mm thickness) gallium oxide (β-Ga2O3) semiconductor-based scintillators for applications requiring these properties. These β-Ga2O3 scintillators were grown using the fast turnaround (∼2 days) crucible-free optical float zone (FZ) technique. The high light yield and ultrafast decay time of these high-purity n-type semiconductors with free carrier concentration of 6 × 1017 cm−3 are attributed to native defects, specifically oxygen vacancies (VO) and gallium–oxygen vacancy pairs (VGa–VO), generated during optimized FZ growth. The ultrafast decay, along with high light yield, enables excellent timing resolution and high count rate detection for applications like time-of-flight positron emission tomography, physics experiments, and nuclear safety. The radiation hardness of these devices has been documented in a separate publication. [ABSTRACT FROM AUTHOR]

A new one-dimensional hybrid [APCHA]Cu2I4 was designed and applied as an X-ray scintillator. It exhibits broad-band green emission with a high PLQY of 74.80% and excellent stability. It demonstrates radioluminescence property with a light yield of 28 336 photons MeV−1, detection limit of 41 nGyair s−1, and high spatial limit of 13.95 lp mm−1 in X-ray imaging. [ABSTRACT FROM AUTHOR]

Vacuum‐evaporated metal halides (MHs) scintillator thick films have received much attention in the X‐ray imaging field due to their excellent light yield and uniform large‐area preparation. However, the inevitable heteromorphic homologs in MHs (e.g., Copper‐based MHs (Cu‐MHs): CsCu2X3∖Cs3Cu2X5) and change of film structural backbone will result in spectral hybridization (phase purity), and the film eventually detaches (lattice mismatches). Herein, a single‐source vacuum evaporation method to prepare a thick film (≈10 µm) of Cu‐MHs (as an example) scintillators is realized: 1) Presynthesis of pure phase materials by solution method with a protective agent to ensure phase purity without precise control of component ratios in evaporation process; 2) One‐shot formation of film structural backbone avoids stress accumulation and utilize the longitudinal growth characteristics of crystalline films to obtain crystal orientations with better optical outputs. Finally, the films obtained have a light yield comparable to a partially single‐crystal (53 983 photons MeV−1) and an imaging resolution (14.1 lp mm−1) comparable to the partial template method. The detection system based on the prepared Cu‐MHs scintillator thick films exhibits good response speed and linearity in response to different X‐ray radiation intensities and exposure times. The method will further drive the application of MHs is believed. [ABSTRACT FROM AUTHOR]

ZrO2 samples were obtained using three different synthesis methods (Calcination, Co-precipitation and Hydrothermal). The samples were characterized to analyze the effect of the crystalline phase on their thermoluminescent (TL) and photoluminescent (PL) responses. The ZrO2 phase was analyzed by X-Ray diffraction (XRD) and Raman. Nanoparticle size distribution was obtained by scanning electron microscopy (SEM). For optical analysis, characterizations included absorbance measurements, where samples exhibited modifications in color centers, PL emission and experimental fluorescence lifetime decay ( τ exp) measurements. Additionally, their TL response was studied under UV (245 nm and 385 nm), and 6 MV photon energy from LINAC excitation. The obtained results show the improvement of TL and PL properties due to ZrO2 phase while an amorphous ZrO2 synthesized by hydrothermal method is an excellent prospect to be used as TL material and it may be a promising scintillator material at 254 nm. ZrO2 samples were obtained using three different synthesis methods (Calcination, Co-precipitation and Hydrothermal). The samples were then characterized, TL response was studied under UV (245 and 385 nm), and 6 MV photon energy from LINAC excitation showing an improvement of TL and PL properties due to ZrO2 phase. Amorphous ZrO2 synthesized by hydrothermal method has great potential as a TL material and it may be a promising scintillator material at 254 nm. [ABSTRACT FROM AUTHOR]

Background: High‐resolution brain positron emission tomography (PET) scanner is emerging as a significant and transformative non‐invasive neuroimaging tool to advance neuroscience research as well as improve diagnosis and treatment in neurology and psychiatry. Time‐of‐flight (TOF) and depth‐of‐interaction (DOI) information provide markedly higher PET imaging performance by increasing image signal‐to‐noise ratio and mitigating spatial resolution degradation due to parallax error, respectively. PET detector modules that utilize light sharing can inherently carry DOI information from the multiple timestamps that are generated per gamma event. The difference between two timestamps that are triggered by scintillation photons traveling in opposite directions signifies the event's depth‐dependent optical photon TOF (oTOF). However, light leak at the crystal‐readout interface substantially degrades the resolution of this oTOF‐based depth encoding. Purpose: We demonstrate the feasibility of oTOF‐based depth encoding by mitigating light leak in single‐ended‐readout Prism‐PET detector modules using tapered crystals. Minimizing light leak also improved both energy‐based DOI and coincidence timing resolutions. Methods: The tapered Prism‐PET module consists of a 16 ×$\times$ 16 array of 1.5 ×$\times$ 1.5 ×$\times$ 20 mm3${\rm {mm}}^3$ lutetium yttrium oxyorthosillicate (LYSO) crystals, which are tapered down to 1.2 ×$\times$ 1.2 mm2${\rm {mm}}^2$ at the crystal‐readout interface. The LYSO array couples 4‐to‐1 to an 8 ×$\times$ 8 array of 3 ×$\times$ 3 mm2${\rm {mm}}^2$ silicon photomultiplier (SiPM) pixels on the tapered end and to a segmented prismatoid light guide array on the opposite end. Performance of tapered and non‐tapered Prism‐PET detectors was experimentally characterized and evaluated by measuring flood histogram, energy resolution, energy‐, and oTOF‐based DOI resolutions, and coincidence timing resolution. Sensitivities of scanners using different Prism‐PET detector designs were simulated using Geant4 application for tomographic emission (GATE). Results: For the tapered (non‐tapered) Prism‐PET module, the measured full width at half maximum (FWHM) energy, timing, energy‐based DOI, and oTOF‐based DOI resolutions were 8.88 (11.18)%, 243 (286) ps, 2.35 (3.18) mm, and 5.42 (13.87) mm, respectively. The scanner sensitivities using non‐tapered and tapered crystals, and 10 rings of detector modules, were simulated to be 30.9 and 29.5 kcps/MBq, respectively. Conclusions: The tapered Prism‐PET module with minimized light leak enabled the first experimental report of oTOF‐based depth encoding at the detector module level. It also enabled the utilization of thinner (i.e., 0.1 mm) inter‐crystal spacing with barium sulfate as the reflector while also improving energy‐based DOI and timing resolutions. [ABSTRACT FROM AUTHOR]

Doping in luminescent metal halides has become an effective strategy for tailoring the optoelectronic properties. Herein, Cu+ is introduced into Rb2AgBr3 to design the synthesis of Rb2AgBr3:xCu+, which possess cold‐white light emission at room‐temperature without changing the spectral profiles; however, the Cu+ incorporation significantly enhances the photoluminescence quantum efficiency to 98.8% in Rb2AgBr3:0.05Cu+. Additionally, a high scintillation light yield of up to 79 250 photons MeV−1 and a low detection limit of 714.83 nGy s−1 have been achieved via this Cu+ doping engineering. X‐ray imaging with a spatial resolution of up to 5.8 lp mm−1 is further realized using a large scintillator film prepared by mixing polydimethylsiloxane with Cu+ doped Rb2AgBr3 scintillators. This study provides a Cu+ doping design principle for improving both the photoluminescence and scintillation performances of metal halides. [ABSTRACT FROM AUTHOR]

The photoluminescence and scintillation properties of KI:Eu synthesized by the vertical Bridgman-Stockbarger method were investigated. All the samples showed a broad peak at 430-450 nm under UV and X-ray irradiations, and the origin of emission was ascribed to the 4f65d1-4f7 transition of Eu2+. Furthermore, a tail emission at 500 nm under X-ray irradiation was observed, the origin of which could be ascribed to color centers associated with oxygen impurities. According to the pulse height spectra, the highest light yield (LY) under 241Am ?-ray (60 keV) irradiation was 3400 photons/MeV among the prepared samples. In terms of LY and afterglow, the optimal concentration of Eu was found to be 0.3%. [ABSTRACT FROM AUTHOR]

Tb-doped SrLu2O4 single crystals were grown by the floating zone method, and their optical and scintillation properties were evaluated. Regarding the scintillation properties, all the prepared crystals showed the sharp emission peaks assigned to Tb3+ 4f-4f transitions in the range of 350-650 nm. The obtained decay times of 1.0-1.6 ms were typical values for the Tb3+ 4f-4f transitions. From the results of the pulse area spectra, the 1.0% Tb-doped crystal showed the highest light yield of 19600 photons/MeV among the prepared crystals. [ABSTRACT FROM AUTHOR]

Modern gamma-ray spectrometers based on solid-state scintillators are increasingly being used in fields where previously dosemeters were applied. From the spectra, precise fluence and dose information can be derived. The most important methods of doing this are investigated in detail; the conversion method, which is based on weighing functions; and unfolding, here using the GRAVEL algorithm. Both methods can be used to process any kind of spectra, regardless of the type of spectrometer employed. The GRAVEL algorithm is described in detail. The implementation of both methods is shown and results of examples are compared. Advantages and disadvantages of both techniques are discussed. For the first time, most precise conversion data up to 20 MeV are published, even extending the quantity H *(10) to this energy. They may serve for the improvement and harmonisation of dose rate measurements using scintillation spectrometers, e.g. those used in early warning systems. [ABSTRACT FROM AUTHOR]

A new compact time-of-flight neutron detector is being planned for the identification and energy measurement of neutrons produced in nucleus-nucleus interactions at energies up to 4 AGeV at the BM@N experiment, located at the Nuclotron (Joint Institute for Nuclear Research, Dubna, Russia). This detector will be used to measure neutron yields and azimuthal flows, which should be sensitive to the equation of state of dense nuclear matter, as shown in various theoretical models It is proposed to use plastic scintillators produced at JINR and IFTP and silicon photomultipliers with a sensitive area of 6 × 6 mm2 for photon registration, one for each scintillation cell. To achieve the required neutron energy resolution (of the order of several percent) in the energy range up to 4 GeV, the time resolution of scintillation detectors should be 100−150 ps. The concept of a time-of-flight neutron detector is discussed. The results of measurements of the light yield and time resolution of several scintillation detector specimens of various sizes and two types of silicon photomultipliers are presented. [ABSTRACT FROM AUTHOR]

Mg4Ta2O9 single crystals doped with 0.01, 0.1, and 1% Er were grown using the floating zone method, and their photoluminescence and scintillation properties were studied. X-ray diffraction analysis confirmed that all samples had a hexagonal structure of Mg4Ta2O9. The samples showed that the emission peak at 1550 nm was due to 4f−4f transitions of Er3+ ions, with quantum yields of 32.9, 46.6, and 18.0% for 0.01, 0.1, and 1% doping concentrations, respectively. All samples showed scintillation with a broad emission band at 350 nm due to charge transfer from Ta5+ to O2− ions and emission peak at 1550 nm due to 4f−4f transition of Er3+ ions. The dose rate response functions showed that the detection limit for all samples was 0.06 Gy/h for scintillation detector applications. [ABSTRACT FROM AUTHOR]

All‐inorganic halide perovskites appear as a promising class of scintillators for radiation detection applications due to their excellent optoelectronic properties. Herein, a self‐activated perovskite CsEuBr3 single crystal is developed as an efficient X‐ and γ‐ray scintillator. Single crystals of CsEuBr3 are grown by the Bridgman method. The phase structure, stability, photophysics properties, and scintillation performance of CsEuBr3 single crystals are studied. Under X‐ray irradiation, its emission peaks at 445 and 510 nm, associated with Eu2+ 5d–4f and defect‐related emission, respectively, are studied. Under 137Cs gamma irradiation, it has a decent light yield of 22 000 ± 2000 photons MeV−1 and an energy resolution of 6.2 ± 0.4% at 662 keV with a scintillation decay of 510 ns. [ABSTRACT FROM AUTHOR]

Ce:(MgxCa1-x)HfO3 (x = 0.5, 2.5, 5, and 10%) single crystals were successfully grown by the floating zone method, and their photoluminescence (PL) and scintillation properties were investigated. A broad luminescence band with a maximum at 430 nm was observed in both the PL and scintillation spectra. The PL quantum yield (QY) improved with the substitution of Mg, and the PL QY of Ce:(MgxCa1-x)HfO3 reached 50%. Fast decay due to the 5d-4f transition of Ce3+ was observed for both the PL and scintillation. Ce:(MgxCa1-x)HfO3 (x = 5%) showed the highest light yield of ~9500 photons/MeV among the synthesized samples, and this value is higher than that of common X- and gamma-ray detection scintillators such as Bi4Ge3O12 and Ce:Gd2SiO5 single crystals. [ABSTRACT FROM AUTHOR]

The well-known narrowing of the Mössbaur γ-line with increasing age of the excited energy state ℏω0 of the emitter nucleus (the half-life is T1/2) and broadening of the γ-line with decreasing irradiation time of the absorber nucleus are analyzed. Taking into account the short time of emission of quantum transition energy – much less than T1/2, which can be seen, for example, from the duration of the γ-signal on the scintillator, the analysis leads to the idea of the structure of the γ-quantum (photon) as an electromagnetic wave of frequency ω0 that does not carry energy (0-wave), which is emitted by the nucleus from the moment of formation of the excited state to the quantum transition, with the energy quantum ℏω0 in the form of a short-term singularity on the "tail" of this 0-wave. A possible source of 0-waves can be virtual transitions of the nucleus from the excited state to the ground state and back before the emission of an energy quantum. Detection of 0-waves is possible due to changing the width of the γ‑line with additional irradiation of the absorber nuclei by resonant 0-waves. The possibility of predicting the future decay of an excited state by 0-waves detecting and the prospects of using 0-waves for information transmission are noted. The principle of a 0-wave generator without energy radiation is proposed. [ABSTRACT FROM AUTHOR]

The Nd-doped LaMgAl11O19 single crystals were synthesized by the floating zone method, and the photoluminescence and scintillation properties were evaluated. Under X-ray irradiation, several sharp emission peaks due to the 4f–4f transitions of Nd3+ were observed at 900, 1060, and 1340 nm in the near-infrared range, and the decay curves show the typical decay time for Nd3+. The samples show good afterglow properties comparable with practical X-ray scintillators. The 1% and 3% Nd-doped LaMgAl11O19 samples show a good linearity in the dynamic range from 6–60,000 mGy/h. [ABSTRACT FROM AUTHOR]

In this study, we investigate the halide perovskite material Cs 2 LiLuCl 6 using both density functional theory (DFT) and time-dependent density functional theory (TD-DFT) approaches. Our analysis focuses on the structural, electronic, and optical properties of the material, conducted with the Quantum Espresso code. In order to confirm the structural stability of the material, we performed various tests including analysis of elastic constants, formation energy, tolerance factor, and phonon dispersion. Employing the generalized gradient approximation (GGA) and GGA+U, we determine that the material behaves as an insulator with a direct band gap of 5.3042 eV and 5.4245 eV, respectively. Additionally, DFT+U calculations were performed to study the dielectric function, reflectivity, absorption coefficient, and refractive index, revealing a high transmittance rate exceeding 90%. Under ideal conditions, the upper light yield (LYsc) is estimated to be 75 411 ph/MeV and 73 739 ph/MeV for the DFT and DFT+U methods, respectively. These results, along with the presence of lithium in Cs 2 LiLuCl 6 , highlight its potential for use in scintillation-based thermal-neutron detection applications. • Cs2LiLuCl6 is stable in a cubic structure as shown by its formation energy and phonon data. • Cs2LiLuCl6 exhibits insulating behavior with a direct band gap. • The material has high UV emissivity, improving scintillation applications. • Cs2LiLuCl6 achieves 75,411 photons/MeV (DFT) and 73,739 photons/MeV (DFT+U). [ABSTRACT FROM AUTHOR]

Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 bulk crystals were synthesized using the conventional vertical Bridgman method, and the photoluminescence, radioluminescence, and detector properties were evaluated. The Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 samples show a broad emission band at 750, 690, and 650 nm, respectively, which is attributable to the 5d-4f transitions of Sm2+. The pulse height spectra under 137Cs γ-rays (662 keV) show that the Sm-doped CaCl 2 and SrCl 2 exhibit 9300 and 33000 photons/MeV, respectively. These samples can be used for γ-ray measurements in the red to NIR region. • Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 crystals were synthesized using the conventional vertical Bridgman method. • The photoluminescence, radioluminescence, and detector properties were evaluated. • The samples show a broad emission band at 600–800 nm due to Sm2+. • Sm-doped CaCl 2 , SrCl 2 , and BaCl 2 exhibit light yield of 9300, 33000, and 16000 photons/MeV, respectively. [ABSTRACT FROM AUTHOR]

We present studies of a novel plastic scintillator branded M600, which was developed and provided by Target Systemelektronik. This new material is, in contrast to other solid organic scintillators offered by commercial providers, based on a polyurethane matrix complemented with scintillating and wavelength-shifting additives. This paper covers measurements of absolute light output, LO, (photons per 1 MeV-γ), γ-non-proportionality (NP), light pulse shapes, and neutron-gamma (n/γ) discrimination. The measurements were carried out either using standard calibration gamma sources (LO, NP) or in a mixed field of neutron and γ radiation from an intense (∼4 × 105 neutrons/s/4π) AmBe source (n/γ discrimination). The measured light output was 9650 ± 1000 ph/MeV and the PSD's figure of merit (FoM) was found as 2.2 ± 0.1 at ∼1000 keVee for ∅2.54 cm × 2.54 cm M600 sample. The bigger sample (∅5.08 cm × 5.08 cm) exhibits about 25% lower LO and poorer FoM when compared to the ∅2.54 cm × 2.54 cm M600, due to self-absorption. [ABSTRACT FROM AUTHOR]

Single crystals of Cs 3 Cu 2 I 5 :Tl have gained great attention due to superior scintillation performance. However, the effect of segregation behavior of Tl dopant on scintillation performance of Cs 3 Cu 2 I 5 :Tl single crystals is still unclear. In this work, single crystals of Cs 3 Cu 2 I 5 doped with different Tl concentrations with a diameter of 7 mm and a length of 90 mm were grown by the Bridgman method. The effective segregation coefficient of Tl ions in the Cs 3 Cu 2 I 5 single crystal was determined as 0.2 ± 0.03. The effects of Tl segregation on scintillation properties, such as light yield, energy resolution, and scintillation decay time, were systematically studied. It is found that with the increase of Tl concentration, the energy resolution remains relatively stable, ranging from 3.8 % to 4.4 % at 662 keV, while the light yield increases from 65,000 photons/MeV to 90,000 photons/MeV. [ABSTRACT FROM AUTHOR]

We have developed LiAlO 2 nanoparticle-loaded polystyrene-based plastic scintillators for neutron detection and evaluated the neutron detection properties. The size of LiAlO 2 nanoparticles was ∼150 nm. The distribution of nanoparticles in the plastic scintillator was uniform in the horizontal direction but non-uniform in the vertical direction. The emission peak was observed around 420 nm in the scintillation spectra and is attributed to1,4-Bis[2-(5-phenyloxazolyl)] benzene (POPOP) included as an organic phosphor. The 10 wt% LiAlO 2 nanoparticle-loaded plastic scintillators containing 22 wt% 2,5-Diphenyloxazole (DPO-POPOP (the molar ratio of 80:1) had the highest light yield of 1600 photons/neutron, which is significantly higher than that of a commercially available 10B-loaded plastic scintillators (BC-454) having a light yield of 800 photons/neutron. • We developed LiAlO 2 nanoparticle-loaded plastic scintillators for neutron detection. • The light yield of 1600 photons/neutron was achieved. • The size of LiAlO 2 nanoparticles was ∼150 nm. [ABSTRACT FROM AUTHOR]

Liquid argon time projection chambers (TPC) are widely used in neutrino oscillation and dark matter experiments. Detection of scintillation light in liquid argon TPC's is challenging because of its short wavelength, in the VUV range, and the cryogenic temperatures (∼ 86 K) at which the sensors must operate. Wavelength shifters (WLS) are typically needed to take advantage of the high Photon Detection Efficiency (PDE) in the visible range of most of photondetectors. The Hamamatsu VUV4 S13370–6075CN SiPMs can directly detect VUV light without the use of WLS, which main benefit is an improved PDE at these short wavelengths, but also the visible light from WLS. The manufacturer (Hamamatsu Photonics K.K.) provides a complete characterization of these devices at room temperature; however, previous studies have indicated a decrease of the PDE at cryogenic temperature for VUV light. In this work, we present the measurement of the PDE of VUV4 SiPMs at cryogenic temperature for different wavelengths in the range [270, 570] nm. A dedicated measurement at 127 nm is also shown. [ABSTRACT FROM AUTHOR]

0.5, 1, 2, and 5% Er-doped La 3 Ga 5 SiO 14 (LGS) single crystals were synthesized by the Floating Zone method and the photoluminescence (PL) and scintillation properties were characterized. Emission peaks appeared at visible–near-infrared (NIR) regions. Their spectral features matched with those due to the 4f–4f transitions of Er3+. The PL quantum yields of 0.5, 1, 2, and 5% Er-doped samples were respectively 45.0, 73.3, 82.5, and 69.4%. The decay times due to the 2H 9/2 –4I 15/2 transitions of Er3+ were obtained when visible ranges were monitored under excitation of both visible lights and X-rays. All the prepared samples showed good linearity between the X-ray exposure dose rate and scintillation signals in NIR ranges. The best lower detection limit in prepared samples was 5 mGy/h recorded by the 2% Er-doped LGS. • Er-doped La 3 Ga 5 SiO 14 single crystals were synthesized by the Floating zone method. • Luminescence due to 4f–4f transitions of Er3+ was observed in both visible and near-infrared regions. • Quantum yields of 0.5, 1, 2, and 5% Er-doped samples were respectively 45.0, 73.7, 82.5, and 69.4%. • The best lower detection limit in prepared samples was 5 mGy/h obtained by 2% Er-doped sample. [ABSTRACT FROM AUTHOR]

Ce,Mg:Lu 2 YGa x Al 5-x O 12 (x = 1.5, 2, 2.5, 3) ceramic scintillators were fabricated by oxygen sintering combined with air annealing using nano-powders synthesized by the co-precipitation method. The Ce3+ 5d 1 → 4f (2F 5/2 , 2F 7/2) luminescence band was blue shifted with increasing Ga content due to the decrease in the crystal field splitting of the 5d levels. At room temperature (RT), the decrease of photoluminescence decay time and scintillation decay time was observed with increasing Ga content. At 662 keV γ-rays, the sample Ga2 exhibited high light yield (LY) of 28,700 photons/MeV, fast scintillation decay times of 17.7 ns (17 %) + 45.7 ns (83 %), and good time resolution of ∼220 ps. At RT, the decrease of LY value for the samples Ga2.5 and Ga3 could be attributed to the larger thermal ionization of the excited Ce3+ centers. • Scintillation properties of Ce,Mg:Lu 2 YGa x Al 5-x O 12 (x = 1.5, 2, 2.5, 3) ceramics are investigated. • All ceramic samples show fast effective scintillation decay time less than 47 ns. • Sample x = 2 shows high LY of ∼28,700 ph/MeV @662 keV γ rays. • Samples x = 2 and 2.5 show good coincidence time resolution of 220 ps. [ABSTRACT FROM AUTHOR]

CsI(Tl) scintillator has been widely used in X-ray flat-panel detectors due to excellent performance characteristics including a suitable Si-photodiode emission wavelength, excellent optical output, and fast decay time. Here, a solution-based space-confined growth method was presented to achieve CsI(Tl) scintillator single-crystal flakes with controllable thickness. The grown CsI(Tl) single-crystal flake exhibits a comparable light yield (∼72,000 photons/MeV) and a lower afterglow level (0.1% @ 21 ms, 0.01% @ 118 ms) in comparison to that by the traditional melting method. This space-confined method allows for the achievement of a single crystal thickness of only 0.27 mm, making it suitable for direct application in X-ray detection and other related fields. It may open up new possibilities for the development of halide scintillator single crystals. A solution-based space-confined growth method enables the growth of high-quality CsI(Tl) single crystal flakes with controlled thickness for X-ray flat-panel detectors. [Display omitted] • A space-confined solution method is used to grown CsI(Tl) single-crystal flakes. • The thickness of the CsI(Tl) flake grown using this method can be controlled to be as thin as approximately 0.27 mm. • The CsI(Tl) flake exhibits a lower afterglow and a comparable light yield in comparison to that by the melting method. [ABSTRACT FROM AUTHOR]

This article presents a physics-informed deep learning method for the quantitative estimation of the spatial coordinates of gamma interactions within a monolithic scintillator, with a focus on Positron Emission Tomography (PET) imaging. A Density Neural Network approach is designed to estimate the 2-dimensional gamma photon interaction coordinates in a fast lead tungstate (PbWO 4) monolithic scintillator detector. We introduce a custom loss function to estimate the inherent uncertainties associated with the reconstruction process and to incorporate the physical constraints of the detector. This unique combination allows for more robust and reliable position estimations and the obtained results demonstrate the effectiveness of the proposed approach and highlights the significant benefits of the uncertainties estimation. We discuss its potential impact on improving PET imaging quality and show how the results can be used to improve the exploitation of the model, to bring benefits to the application and how to evaluate the validity of the given prediction and the associated uncertainties. Importantly, our proposed methodology extends beyond this specific use case, as it can be generalized to other applications beyond PET imaging. [ABSTRACT FROM AUTHOR]

Sm-doped SrCl2 crystals were prepared, and the scintillation properties such as emission spectra, decay profiles, and pulse height were investigated. Under X-ray irradiation, a broad band can be observed at 680 nm, which indicates that the major origin is due to 5d-4f transitions of Sm2+. The decay curve is approximated by one exponential function with a decay time of 10 μs, and the decay time constant is typical for Sm2+. From the pulse height of 137Cs γ-rays, 0.1% Sm:SrCl2 shows a light yield of 33,000 photons/MeV. [ABSTRACT FROM AUTHOR]

This manuscript describes measurements of water-based liquid scintillators (WbLS), demonstrating separation of the Cherenkov and scintillation components using a low energy β source and the fast timing response of a Large Area Picosecond Photodetector (LAPPD). Additionally, the time profiles of three WbLS mixtures, defined by the relative fractions of scintillating compound, are characterized, with improved sensitivity to the scintillator rise-time. The measurements were made using both an LAPPD and a conventional photomultiplier tube (PMT). All samples were measured with an effective resolution O 100 ps , which allows for the separation of Cherenkov and scintillation light (henceforth C/S separation) by selecting on the arrival time of the photons alone. The Cherenkov purity of the selected photons is greater than 60% in all cases, with greater than 80% achieved for a sample containing 1% scintillator. This is the first demonstration of the power of synthesizing low light yield scintillators, of which WbLS is the canonical example, with fast photodetectors, of which LAPPDs are an emerging leader, and has direct implication for future mid- and large-scale detectors, such as Theia, ANNIE, and AIT-NEO. [ABSTRACT FROM AUTHOR]

This manuscript describes measurements of water-based liquid scintillators (WbLS), demonstrating separation of the Cherenkov and scintillation components using a low energy β source and the fast timing response of a Large Area Picosecond Photodetector (LAPPD). Additionally, the time profiles of three WbLS mixtures, defined by the relative fractions of scintillating compound, are characterized, with improved sensitivity to the scintillator rise-time. The measurements were made using both an LAPPD and a conventional photomultiplier tube (PMT). All samples were measured with an effective resolution O 100 ps , which allows for the separation of Cherenkov and scintillation light (henceforth C/S separation) by selecting on the arrival time of the photons alone. The Cherenkov purity of the selected photons is greater than 60% in all cases, with greater than 80% achieved for a sample containing 1% scintillator. This is the first demonstration of the power of synthesizing low light yield scintillators, of which WbLS is the canonical example, with fast photodetectors, of which LAPPDs are an emerging leader, and has direct implication for future mid- and large-scale detectors, such as Theia, ANNIE, and AIT-NEO. [ABSTRACT FROM AUTHOR]

When considering X-ray radiation registration by a scintillation detector, A. Bousselham et al. (Photoelectron Anticorrelations and Sub-Poisson Statistics in Scintillation Detectors), introduced two Fano factors (the Fano factor for scintillation photons and the Fano factor for photoelectrons). They stated their experimental data provided direct evidence for sub-Poissonian statistics for light photons in scintillators. An accurate mathematical description of the processes in the X-rays registration by a scintillation detector allows one to obtain the correct formulas for the mean value, the output signal variance of photodetectors, and the formula for the covariance between the signals of photodetectors. An analysis of these formulas allows one to conclude that a scintillation detector should be characterized by only one Fano factor, which determines the fluctuations of the electron–hole pair generation process in the scintillator. Since the Fano factor for electron–hole pairs in scintillators is on the order of 0.1, this fact explains the results obtained in the article. Thus, the discovery of sub-Poissonian statistics for light photons in scintillators did not take place. [ABSTRACT FROM AUTHOR]

In this work, we present the development and application of a convolutional neural network (CNN)-based algorithm to precisely determine the interaction position of γ-quanta in large monolithic scintillators. Those are used as an absorber component of a Compton camera (CC) system under development for ion beam range verification via prompt-gamma imaging. We examined two scintillation crystals: LaBr3:Ce and CeBr3. Each crystal had dimensions of 50.8 mm × 50.8 mm × 30 mm and was coupled to a 64-fold segmented multi-anode photomultiplier tube (PMT) with an 8 × 8 pixel arrangement. We determined the spatial resolution for three photon energies of 662, 1.17 and 1.33 MeV obtained from 2D detector scans with tightly collimated 137Cs and 60Co photon sources. With the new algorithm we achieved a spatial resolution for the CeBr3 crystal below 1.11(8) mm and below 0.98(7) mm for the LaBr3:Ce detector for all investigated energies between 662 keV and 1.33 MeV. We thereby improved the performance by more than a factor of 2.5 compared to the previously used categorical average pattern algorithm, which is a variation of the well-established k-nearest neighbor algorithm. The trained CNN has a low memory footprint and enables the reconstruction of up to 104 events per second with only one GPU. Those improvements are crucial on the way to future clinical in vivo applicability of the CC for ion beam range verification. [ABSTRACT FROM AUTHOR]

Low‐dimensional halide perovskites with excellent luminescent properties have become leading candidates for optoelectronic and radiation‐detection applications. In this work, Tl cation is incorporated into 0D perovskite Cs3Cu2I5 host and an ultrabright and efficient scintillator is developed for X‐ray and γ‐ray detection. The Tl‐doped Cs3Cu2I5 crystals exhibit a high photoluminescence quantum efficiency of 79.2%. The radioluminescence emission of Cs3Cu2I5:Tl crystal under X‐ray excitation consists of a self‐trapped exciton emission at 440 nm and a Tl‐related emission at 510 nm at room temperature. With optimized Tl doping, the Cs3Cu2I5 not only demonstrates about five‐times enhanced steady‐state scintillation yield up to 150 000 photons/MeV and an improvement of X‐ray detection limit from 103.6 to 66.3 nGy s−1, but also maintains an extremely low afterglow of 0.17% at 10 ms after X‐ray cut‐off. The Cs3Cu2I5:Tl also possess a remarkable energy resolution of 3.4% at 662 keV and an ultrahigh light yield of 87 000 photons/MeV under 137Cs γ‐ray radiation. [ABSTRACT FROM AUTHOR]

Scintillators, which can emit visible photons under γ- or X-ray excitation, are widely used in radiation detection. Traditional inorganic scintillators usually have some drawbacks, such as hygroscopicity or a high synthesis temperature, and most of them are poisonous. Hence, we report the synthesis of metal iodate scintillators (Eu(IO3)3 and Tb(IO3)3) by a facile hydrothermal reaction that exhibit good radioluminescence (RL) intensity. To further increase the RL intensities, we prepared Eu(IO3)3:xSm and Tb(IO3)3:xGd with stronger RL intensities and higher sensitivities than BaF2 and PbWO4 powders when x = 3%. Furthermore, we obtained scintillating films consisting of Eu(IO3)3:3%Sm and Tb(IO3)3:3%Gd for X-ray imaging. Our Eu(IO3)3:3%Sm and Tb(IO3)3:3%Gd films revealed excellent luminescence under high-energy X-ray excitation and spatial resolutions down to 9 lp mm−1 and 8 lp mm−1, respectively. Thus, these films can be regarded as candidate materials for X-ray imaging. [ABSTRACT FROM AUTHOR]

External optical crosstalk remains a significant source of correlated noise in scintillation detectors optically coupled to silicon photomultiplier (SiPM) arrays and can influence achievable performance by limiting the maximum overvoltage at which a detector can be operated. This study evaluated the potential benefits of incorporating an optical bandpass filter, which is absorptive to optical crosstalk and transmissive for scintillation photons, between the scintillator and SiPM array. Several SiPM and bandpass configurations were characterized, including single-element and SiPM arrays with bare, filter-coupled, crystal-coupled, and crystal-filter-coupled interfaces. Coupling the optical filter between a 4 × 4 array of Broadcom AFBR-S4N44P164 M (NUV-MT) SiPMs and a 12 × 12 × 20 mm3 LYSO crystal decreased the total number of detected optical photon noise by up to 92%. The impact of the filter on crosstalk probability reduction was also characterized by the single-channel measurements with the same SiPM, suppressing external crosstalk up to 64%. With the filter coupled, SiPMs were operable at very high overvoltage. The results of these studies demonstrate that optical filtering is a promising technique to significantly reduce correlated noise in scintillation detectors employing SiPMs. [ABSTRACT FROM AUTHOR]

0.05, 0.1, 0.5, and 1.0 % Dy-doped YVO 4 single crystals were prepared by the optical floating zone technique to obtain photoluminescence (PL) and scintillation properties. All the samples showed the emission owing to charge transfer from V5+ ions to O2− ions inside [VO 4 ]3- and the 4f–4f transitions of Dy3+ ions. Light yields exhibited 37,000 (0.05 % Dy), 42,000 (0.1 % Dy), 44,000 (0.5 % Dy), and 39,000 photons/MeV (1.0 % Dy), based on the pulse height spectra. In afterglow properties, afterglow levels were 37.7 (0.05 % Dy), 25.7 (0.1 % Dy), 23.2 (0.5 % Dy), and 20.6 (1.0 % Dy) ppm. • We have synthesized Dy-doped YVO 4 single crystals by floating zone method. • We have characterized the photoluminescence, and scintillation properties of the Dy-doped YVO 4 single crystal. • Pulse height spectra revealed that the light yield of 0.05, 0.1, 0.5, and 1.0 % Dy-doped YVO 4 single crystals was 37,000, 42,000, 44,000, and 39,000 photons/MeV, respectively. • In afterglow properties, afterglow levels were 37.7 (0.05 % Dy), 25.7 (0.1 % Dy), 23.2 (0.5 % Dy), and 20.6 (1.0 % Dy) ppm. [ABSTRACT FROM AUTHOR]

(Eu x ,Y 1- x) 3 Al 5 O 12 (x = 0.005, 0.01, 0.05, 0.10, 0.15, and 0.20) single crystals were prepared by the floating-zone method. We investigated their photoluminescence (PL) and scintillation properties including PL excitation/emission contour spectra, PL quantum yields, PL decay times, X-ray-induced scintillation spectra, scintillation decay times, and pulse-height spectra under γ-ray irradiation from 137Cs (662 keV). The PL and scintillation spectra exhibited some emission lines at visible wavelength due to the 4f-4f transitions of Eu3+ ions, and the PL and scintillation decay times resulted several milliseconds. Among all the samples, (Eu 0.1 ,Y 0.9) 3 Al 5 O 12 and (Eu 0.15 ,Y 0.85) 3 Al 5 O 12 single crystals showed the highest PL quantum yield. On the other hand, (Eu 0.01 ,Y 0.99) 3 Al 5 O 12 single crystal showed the highest light yield. The light yield of the sample was estimated to be 36,000 photons/MeV from the pulse height spectrum. • Eu-doped YAG single crystals were grown by the floating zone method. • Scintillation properties of Eu-doped YAG were investigated. • Emission peaks due to 4f-4f transitions of Eu3+ ions were observed. • 1.0 % Eu-doped YAG showed the highest light yield (36,000 photons/MeV). [ABSTRACT FROM AUTHOR]

Antimony based organic–inorganic hybrid compounds (Ph 4 P) 2 SbCl 5 (Ph 4 P: tetraphenylphosphonium) and (DTA) 2 SbCl 5 (DTA: dodecyltrimethylammonium) with a zero-dimensional structure were fabricated, and the optical and scintillation characteristics were evaluated. A broadband photoluminescence possibly due to self-trapped exciton (STE) emission appeared at 692 nm for (Ph 4 P) 2 SbCl 5 and 630 nm for (DTA) 2 SbCl 5 under 370 nm excitation light. The quantum yields were 98 % for (Ph 4 P) 2 SbCl 5 and 97 % for (DTA) 2 SbCl 5. Under X-ray, the broad emission peak was also detected at 670 nm for (Ph 4 P) 2 SbCl 5 and at 615 nm for (DTA) 2 SbCl 5. Furthermore, scintillation decay time constants were 4.9 μs for (Ph 4 P) 2 SbCl 5 and 5.0 μs for (DTA) 2 SbCl 5. Moreover, the scintillation light yield of (Ph 4 P) 2 SbCl 5 was estimated to be about 12,000 photons/MeV, whereas the light of (DTA) 2 SbCl 5 could not be determined. In addition, afterglow levels were 56 ppm for (Ph 4 P) 2 SbCl 5 and 130 ppm for (DTA) 2 SbCl 5. • Antimony based organic–inorganic hybrid compounds (Ph 4 P) 2 SbCl 5 and (DTA) 2 SbCl 5 were fabricated. • The compounds showed a broad emission due to self-trapped excitons with a high quantum yield. • The scintillation light yield of (Ph 4 P) 2 SbCl 5 was estimated to be about 12,000 photons/MeV. [ABSTRACT FROM AUTHOR]

Environmental friendly metal halides have become emerging candidates as energy downconverting emitters for lighting and X‐ray imaging applications. Herein, luminescent single crystals of tetramethylammonium manganese chloride (C4H12NMnCl3) and tetraethylammonium bromide ((C8H20N)2MnBr4) are synthesized via a facile room‐temperature evaporation method. C4H12NMnCl3 and (C8H20N)2MnBr4 with octahedrally and tetrahedrally coordinated Mn2+ have correspondingly exhibited red and green emission peaking at 635 and 515 nm both originating from 4T1–6A1 transition of Mn2+ with high photoluminescence quantum yield (PLQY) of 91.8% and 85.1% benefiting from their specific crystal structures. Thanks to their strong photoexcitation under blue light, high PLQY, tunable emission spectra, good environmental stability, the white light‐emitting diode based on blending of C4H12NMnCl3 and (C8H20N)2MnBr4 delivers an outstanding luminous efficacy of 96 lm W−1, approaching commercial level, and shows no obvious photoluminescence intensity degradation after 3000 h under operation. In addition, manganese halides also demonstrate interesting characteristics under X‐ray excitation, C4H12NMnCl3 and (C8H20N)2MnBr4 exhibit steady‐state X‐ray light yields of 50 500 and 24 400 photons MeV−1, low detectable limits of 36.9 and 24.2 nGyair s−1, good radiation hardness, and X‐ray imaging demonstration with high‐resolution of 5 lp mm−1. This work presents a new avenue for luminescent Mn‐based metal halides toward multifunctional light‐emitting applications. [ABSTRACT FROM AUTHOR]

In this study, the 3-phenylpropionic acid (3-PPA)-modified Bi2O3 nanoparticle-loaded plastic scintillators were synthesized to obtain fast scintillators having high detection efficiency of high-energy X-rays. To reach a high light yield, the content of 2-(4-tert-butylphenyl)-5-(4-phenylphenyl))-1,3,4-oxadiazole (b-PBD) in the plastic scintillators was optimized. The detection efficiency for high-energy photons was enhanced by the incorporation of surface-modified Bi2O3 nanoparticles of less than 10 nm into scintillators at 5 or 10 wt%. In the pulse-height spectra, the photoelectric peak positions were located at the highest channels for the samples containing 0.50 or 1.0 mol% b-PBD regardless of the Bi concentration. The photoelectric peak positions shifted to lower channels with a further increase in the b-PBD concentration, which indicates that the light yield decreased due to concentration quenching. In addition, the time resolution of the detector equipped with the studied samples was of the sub-nanosecond scale, suggesting that they had a very fast response. [ABSTRACT FROM AUTHOR]

We propose and evaluate the performance of an improved preclinical positron emission tomography (PET) scanner design, referred to as Polaroid-PET, consisting of a detector equipped with a layer of horizontal Polaroid to filter scintillation photons with vertical polarization. This makes it possible to improve the spatial resolution of PET scanners based on monolithic crystals. First, a detector module based on a lutetium-yttrium orthosilicate monolithic crystal with 10 mm thickness and silicon photomultipliers (SiPMs) was implemented in the GEANT4 Monte Carlo toolkit. Subsequently, a layer of Polaroid was inserted between the crystal and the SiPMs. Two preclinical PET scanners based on ten detector modules with and without Polaroid were simulated. The performance of the proposed detector modules and corresponding PET scanner for the two configurations (with and without Polaroid) was assessed using standard performance parameters, including spatial resolution, sensitivity, optical photon ratio detected for positioning, and image quality. The detector module fitted with Polaroid led to higher spatial resolution (1.05 mm FWHM) in comparison with a detector without Polaroid (1.30 mm FHWM) for a point source located at the center of the detector module. From 100% of optical photons produced in the scintillator crystal, 65% and 66% were used for positioning in the detectors without and with Polaroid, respectively. Polaroid-PET resulted in higher axial spatial resolution (0.83 mm FWHM) compared to the scanner without Polaroid (1.01 mm FWHM) for a point source at the center of the field of view (CFOV). The absolute sensitivity at the CFOV was 4.37% and 4.31% for regular and Polaroid-PET, respectively. Planar images of a grid phantom demonstrated the potential of the detector with a Polaroid in distinguishing point sources located at close distances. Our results indicated that Polaroid-PET may improve spatial resolution by filtering the reflected optical photons according to their polarization state, while retaining the high sensitivity expected with monolithic crystal detector blocks. [ABSTRACT FROM AUTHOR]

The spatial resolution and imaging characteristics of plastic scintillators are characterized using laser-driven proton beams. Laser-driven proton beams typically have broad energy spectra and are accompanied by relativistic electrons and high-energy photons, both potentially contributing to background noise. Different types and thicknesses of Eljen Technology scintillators are compared to determine their intrinsic point spread function. Point-projection imaging of a mesh is used to compare the imaging resolution of the scintillator to the usual imaging detector, radiochromic film, and is found to be reasonably comparable and sufficient for many experimental applications. [ABSTRACT FROM AUTHOR]

The scintillation characteristics of Lu0.8Gd2.2 (Al5–xGax)O12:Ce,Mg (x = 2.6 and 3) single crystals grown by the micropulling down method are investigated. The light yield of 27600 photons/MeV obtained for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg is higher than that of 25 400 photons/MeV obtained for Lu0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. The photoluminescence and scintillation decays measured at room temperature (RT) for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg are faster than those for Lu0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. Temperature dependence of radioluminescence (RL) intensity indicates a lower quenching temperature for Lu0.8Gd2.2Al2Ga3O12:Ce,Mg. Coincidence time resolution of a Lu0.8Gd2.2Al2Ga3O12:Ce,Mg detector in coincidence experiment with a BaF2 detector was measured to be 410 ps. The afterglow and thermally stimulated luminescence (TSL) characteristics below RT are also measured. [ABSTRACT FROM AUTHOR]

Luminescence and scintillation properties of Eu2+- and Ce3+-doped TlSr2Cl5 crystals are reported for large effective atomic number (Zeff = 63.7) that have potential applications in X-ray and gamma ray detection. We have previously developed TlSr2Cl5 crystalline scintillators. To improve the scintillation properties of TlSr2Cl5, Ce3+ and Eu2+ were doped into the crystals in this study. The scintillation emission bands of Eu2+-doped TlSr2Cl5 were observed at 420 nm and those for Ce3+-doped TlSr2Cl5 were observed at 380, 450, and 500 nm. Band peaks at 450 and 500 nm were similar to those of undoped TlSr2Cl5, which are characteristic of self-activated thallium-based chloride crystals. The light yields of Ce3+- and Eu2+-doped TlSr2Cl5 were estimated to be approximately 16,000 and 21,000 photons/MeV, respectively. The light yield of Eu2+-doped TlSr2Cl5 is higher than that of undoped TlSr2Cl5 crystals (19,000 photons/MeV). It was suggested that Eu2+ is more suitable dopant for TlSr2Cl5 than Ce3+. The higher light yield of Eu2+-doped TlSr2Cl5 is due to the emissions by Eu2+ ions, which makes it easier to distinguish peaks from noise and improve the energy resolution. [ABSTRACT FROM AUTHOR]

A new self-activated X-ray scintillator, BaWO2F4, with an excellent photoluminescence quantum efficiency is reported. Hydrothermally grown single crystals, space group P2/n, exhibit a 3D framework structure containing isolated WO2F4 octahedra. BaWO2F4 exhibits green emission under UV light with a high quantum yield of 53% and scintillates when exposed to X-rays(Cu). [ABSTRACT FROM AUTHOR]

Purpose: In living organisms, the positron-electron annihilation (occurring during the PET imaging) proceeds in about 30% via creation of a metastable ortho-positronium atom. In the tissue, due to the pick-off and conversion processes, over 98% of ortho-positronia annihilate into two 511 keV photons. In this article, we assess the feasibility for reconstruction of the mean ortho-positronium lifetime image based on annihilations into two photons. The main objectives of this work include the (i) estimation of the sensitivity of the total-body PET scanners for the ortho-positronium mean lifetime imaging using 2γ annihilations and (ii) estimation of the spatial and time resolution of the ortho-positronium image as a function of the coincidence resolving time (CRT) of the scanner. Methods: Simulations are conducted assuming that radiopharmaceutical is labeled with 44Sc isotope emitting one positron and one prompt gamma. The image is reconstructed on the basis of triple coincidence events. The ortho-positronium lifetime spectrum is determined for each voxel of the image. Calculations were performed for cases of total-body detectors build of (i) LYSO scintillators as used in the EXPLORER PET and (ii) plastic scintillators as anticipated for the cost-effective total-body J-PET scanner. To assess the spatial and time resolution, the four cases were considered assuming that CRT is equal to 500 ps, 140 ps, 50 ps, and 10 ps. Results: The estimated total-body PET sensitivity for the registration and selection of image forming triple coincidences (2γ+γprompt) is larger by a factor of 13.5 (for LYSO PET) and by factor of 5.2 (for plastic PET) with respect to the sensitivity for the standard 2γ imaging by LYSO PET scanners with AFOV = 20 cm. The spatial resolution of the ortho-positronium image is comparable with the resolution achievable when using TOF-FBP algorithms already for CRT = 50 ps. For the 20-min scan, the resolution better than 20 ps is expected for the mean ortho-positronium lifetime image determination. Conclusions: Ortho-positronium mean lifetime imaging based on the annihilations into two photons and prompt gamma is shown to be feasible with the advent of the high sensitivity total-body PET systems and time resolution of the order of tens of picoseconds. [ABSTRACT FROM AUTHOR]

Purpose: The time-over-threshold (TOT) technique is being used widely due to itsimplications in developing the multi-channel readouts, mainly when fast signal processing is required. Using the TOT technique, as a measure of energy loss instead of charge integration methods, significantly reduces the signal readout costs by combining the time and energy information. Therefore, this approach can potentially be utilized in J-PET tomograph which is built from plastic scintillators characterized by fast light signals. The drawback in adopting this technique lies in the non-linear correlation between input energy loss and TOT of the signal. The main motivation behind this work is to develop the relationship between TOT and energy loss and validate it by the J-PET tomograph setup. Methods: The experiment was performed using a 22Na beta emitter source placed in the center of the J-PET tomograph. This isotope produces photons of two different energies: 511 keV photons from the positron annihilation (direct annihilation or through the formation of a para-positronium atom or pick-off process of ortho-positronium atoms) and a 1275 keV prompt photon. This allows the study of the correlation between TOT values and energy loss for energy ranges up to 1000 keV. Since the photon interacts predominantly via Compton scattering inside the plastic scintillator, there is no direct information of the energy deposition. However, using the J-PET geometry, one can measure the scattering angle of the interacting photon. Since the 22Na source emits photons of two different energies, it is necessary to know unambiguously the energy of incident photons and their corresponding scattering angles in order to estimate energy deposition. In summary, this work presents a dedicated algorithm developed to tag photons of different energies and studying their scattering angles to calculate the energy deposition by the interacting photons. Results: A new method was elaborated to measure the energy loss by photons interacting with plastic scintillators used in the J-PET tomograph. We find the relationship between the energy loss and TOT is non-linear and can be described by the functions TOT = A0 + A1 * ln(E dep + A2) + A3 * (ln(E dep + A2))2 and TOT = A0 - A1 * A2 E dep . In addition, we also introduced a theoretical model to calculate the TOT as a function of energy loss in plastic scintillators. Conclusions: A relationship between TOT and energy loss by photons interacting inside the plastic scintillators used in J-PET scanner is established for a deposited energy range of 100–1000 keV. [ABSTRACT FROM AUTHOR]

The scintillation properties of Mg2+-codoped Lu0.6Gd2.4Al2Ga3O12:Ce (LGAGG:Ce,Mg) single crystal grown by Czochralski’s method are investigated. The light yield (LY), scintillation decay time, and coincidence time resolution are presented in comparison with a GAGG:Ce,Mg reference crystal. The LY of 26 200 photons/MeV obtained for LGAGG:Ce,Mg is lower than that of 39 600 photons/MeV for GAGG:Ce,Mg. Despite a lower LY value, the time resolution of LGAGG:Ce,Mg is comparable to that of GAGG:Ce,Mg due to its faster scintillation decay time. LGAGG:Ce,Mg exhibits a much faster afterglow decay and a lower thermally stimulated luminescence intensity with respect to GAGG:Ce,Mg. [ABSTRACT FROM AUTHOR]

Single crystals of Eu2+-activated SrI2, one of the most leading-edge scintillators for gamma-ray spectroscopy applications, have a low radioactive background, excellent energy resolution of 2.6%–3% at 662 keV, and high light yield of 80 000–120 000 photons/MeV. In this article, tetravalent ions codoping, namely, Hf4+ codoping, was used to enhance its scintillation performance. $\emptyset 12$ mm diameter SrI2:Eu2+ single crystals codoped with 0, 0.05, 0.1, and 0.2 at% Hf4+ were successfully grown by the multiampoule Bridgman method. All grown crystals are highly transparent, crack-free, and inclusion-free. The effects of Hf4+ codoping concentration on the optical and scintillation properties were studied. The gamma-ray energy resolutions of SrI2:Eu single crystals can be improved from 3.4% to 3.1% at 662 keV, and from 6.6% to 6.0% at 122 keV upon 0.05 at% Hf4+ codoping. [ABSTRACT FROM AUTHOR]

The large spread of scintillator performance (light yield and energy resolution) from a theoretical limit shows that we are still far from the deep understanding of the phenomena. Usually, extrinsic aspects of resolution degradation (such as purity, defects, stoichiometry, and so on) are the subject of study. At the same time, intrinsic factors (such as track structure, excitation density, and uniformity) that depend on crystal lattice can play a dominant role in scintillator performance. Some progress in the understanding of these problems is achieved by using the concept of different efficiencies of photon emission from excited regions with different concentrations of electronic excitations. The regions with a high or low concentration of thermalized excitations result in the nonradiative losses of excitations and, therefore, produce additional event-to-event fluctuations. The technique of multidimensional analysis of the time-resolved pulse shape is proposed for the clustering of all the events according to the proximity of the waveform to some centroids of the clusters. This procedure shows that even conventional NaI:Tl and CsI:Tl scintillators allow to achieve an energy resolution of about 3% for 662-keV gamma photons. [ABSTRACT FROM AUTHOR]