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Lead halide perovskites are reportedly a very promising group of materials for scintillation due to their fast sub-nanosecond exciton luminescence, small band-gaps, and high theoretical light yield. Unfortunately, they only show emission at cryogenic temperatures. In this work single crystals of CsPbBr 3 and CsPbCl 3 are studied at cryogenic temperatures. Upon comparing the 10 K emission spectra measured under X-ray and UV–vis excitation, a new near-infrared emission was found for both CsPbBr 3 and CsPbCl 3 only present under X-ray excitation. The integral light yields of CsPbBr 3 and CsPbCl 3 at 10 K are estimated to be 34,000 and 2,200 photons/MeV under 40 keV X-ray excitation, respectively. The main components of the light yield of CsPbBr 3 at 10 K are the near band-gap free exciton emission that suffers from self-absorption and the broad near-infrared emission that falls outside the typical detection range of a photo-multiplier tube. Due to the combination of the two aforementioned effects it was not possible to measure a γ -ray pulse height spectrum for CsPbBr 3 at 10 K. Despite all the suitable properties, like the fast decay, a small band-gap, and the positive prospects of 3D perovskite based scintillators, we conclude that these materials perform poorly as scintillation crystals. [ABSTRACT FROM AUTHOR]

The HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder mission aims to develop a constellation of nanosatellites to study astronomical transient sources, such as gamma-ray bursts, in the X and soft γ energy range, exploiting a novel inorganic scintillator. This study presents the results obtained describing, with an empirical model, the unusually intense and long-lasting residual emission of the GAGG:Ce scintillating crystal after irradiating it with high energy protons (70 MeV) and ultraviolet light (∼ 300 nm). From the model so derived, the consequences of this residual luminescence for the detector performance in operational conditions has been analysed. The suitability of this detector for the HERMES Pathfinder nanosatellites was demonstrated by the low contribution of the afterglow, 1–2 pA at peak, to the input current of the front-end electronics. [ABSTRACT FROM AUTHOR]

Abstract The paper discusses the possible processes of radiation-induced changes that occur during irradiation of composite scintillators containing grains of inorganic crystals, and investigates the effect of these processes on radiation resistance of composite systems. All crystalline inorganic scintillation materials contain defects, which can play the role of quenching centres. An irradiation destroys and changes not only the main material of a scintillator but such the centres as well. As a result, the luminescence intensity can grow for a while due to weakening the effect of quenching. In this case, the luminescence spectrum of a scintillator does not change its shape under various accumulated doses D because no new luminescence centres appear. A modification of the properties of the luminescence centres arising under the action of irradiation has to lead to a change in the spectral characteristics of the luminescence. Therefore, the appearance or absence of such the changes is evidence of which centres are predominantly damaged because of irradiation with given dose D. The paper as well discusses the possibilities of obtaining radiation-resistant materials for the development of wavelength shifting light guides for composite scintillators. We investigated samples based on non-luminescent transparent silicone elastomer containing p -terphenyl or 1,4-di[2-(5-phenyloxazolyl)]benzene (POPOP) molecules. [ABSTRACT FROM AUTHOR]

Abstract The pixelated scintillation screen as an important component of the X-ray imaging detector effectively solves the issue of the lateral spreading of scintillation light and improves the spatial resolution of X-ray imaging. In this work, the hexagonal as well as square arranged pixelated CsI scintillation screens based on the silicon pore templates with pore pitch about 4 μ m and diameter about 3 μ m were fabricated by vacuum melting injection method. The morphology, crystallinity, X-ray excited optical luminescence and X-ray imaging performance of the screens were investigated. The results show that the CsI scintillator was filled into the silicon pore templates uniformly and compactly without microbubbles even if the depth of the filled CsI microcolumns reaches 100 μ m. The pixelated scintillation screen exhibits good CsI crystallinity with (110) preferred orientation. The intensity of X-ray excited optical luminescence of the hexagonal arranged pixelated CsI scintillation screen increases by 14.3% compared with that of the square arranged screen with same thickness. Furthermore, the intensity of the pixelated CsI screen with 100 μ m thickness is 34.1% higher than that of the screen with 40 μ m thickness. The spatial resolution of the X-ray imaging system with the hexagonal arranged pixelated CsI scintillation screen is about 115 lp/mm and not sensitive to the screen thickness, which is 11.5% higher than that with the square arranged screen. The detective quantum efficiency of the system with the hexagonal arranged pixelated CsI scintillation screen appears relatively higher than that with the square arranged screen with same thickness and increases with the thickness of the screen. This means the X-ray imaging performance of the hexagonal arranged pixelated CsI scintillation screen is better than that of the square array arranged screen. Highlights • The hexagonal arranged pixelated CsI scintillation screens without microbubbles were successfully fabricated by vacuum melting injection method. • The spatial resolution of the X-ray imaging system with the hexagonal arranged pixelated CsI scintillation screen is about 115 lp/mm. • The intensity of X-ray excited luminescence of the hexagonal arranged pixelated CsI scintillation screen increases by 14.3% compared with the same thickness square arranged screen. [ABSTRACT FROM AUTHOR]

Lithium magnesium molybdate (Li 2 Mg 2 (MoO 4 ) 3 ) crystals were grown by the low-thermal-gradient Czochralski method. Luminescence properties of the material (emission spectra, thermally stimulated luminescence, dependence of intensity on temperature, phosphorescence) have been studied under X-ray excitation in the temperature interval from 8 to 400 K, while at the same being operated as a scintillating bolometer at 20 mK for the first time. We demonstrated that Li 2 Mg 2 (MoO 4 ) 3 crystals are a potentially promising detector material to search for neutrinoless double beta decay of 100 Mo. [ABSTRACT FROM AUTHOR]

The influence of co-doping of Gd 3 Al 2 GA 3 O 12 :Ce (GAGG:Ce) scintillator with magnesium on the rise time of luminescence response was studied in two GAGG:Ce crystals grown in nominally identical conditions except of Mg co-doping in one of them. Time-resolved photoluminescence spectroscopy and free carrier absorption techniques were exploited. It is evidenced that the Mg co-doping decreases the rise time down to sub-picosecond domain. Meanwhile, the light yield decreases by ∼ 20%. Thus, the feasibility of exploitation of the fast rise edge in luminescence response for ultrafast timing in scintillation detectors is demonstrated. The role of Mg impurities in facilitating the excitation transfer to radiative recombination centers is discussed. [ABSTRACT FROM AUTHOR]

The effect of irradiation on the scintillation light output, optical transmittance, and luminescent spectra of composite scintillators based on single crystal grains of Al 2 O 3 :Ti, is studied. The dielectric gel Sylgard-184 is the base and the binder for the grains inside the composite scintillator. The paper presents and analyses the results obtained for the scintillators exposed by 10 MeV electrons from the linear electron accelerator at room temperature. For exposure doses at least up to D ∼ 550 Mrad when dose rate is 1500 Mrad/h and D ∼ 125 Mrad when dose rate is 0.2 Mrad/h the composite scintillators are radiation-resistant. [ABSTRACT FROM AUTHOR]

The polystyrene film nanocomposites of 0.3 mm thickness with embedded SrF 2 nanoparticles up to 40 wt% have been synthesized. The luminescent and kinetic properties of the polystyrene composites with embedded SrF 2 nanoparticles upon the pulse X-ray excitation have been investigated. The luminescence intensity of the pure polystyrene scintillator film significantly increases when it is loaded with the inorganic SrF 2 nanoparticles. The film nanocomposites show fast (∼2.8 ns) and slow (∼700 ns) luminescence decay components typical for a luminescence of polystyrene activators (p-Terphenyl and POPOP) and SrF 2 nanoparticles, respectively. It is revealed that the fast decay luminescence component of the polystyrene composites is caused by the excitation of polystyrene by the photoelectrons escaped from the nanoparticles due to photoeffect, and the slow component is caused by reabsorption of the self-trapped exciton luminescence of SrF 2 nanoparticles by polystyrene. [ABSTRACT FROM AUTHOR]

The luminescence and scintillation properties of Gd 1.53 La 0.47 Si 2 O 7 :Ce (GPSLa23.5%:Ce) scintillators were investigated and compared to those of Lu 1.9 Y 0.1 SiO 5 :Ce (LYSO:Ce) scintillators. At 662 keV γ-rays, the light yield of 33,500±3300 ph/MeV obtained for GPSLa23.5%:Ce is higher than that of 28,100±2800 ph/MeV obtained for LYSO:Ce. The energy resolution of 4.8±0.2% obtained for GPSLa23.5%:Ce is much better than that of 8.2±0.3% obtained for LYSO:Ce due to its better intrinsic resolution and proportionality of light yield. The light yield and energy resolution for α- rays, as well as a light yield ratio under excitation with α - and γ - rays (α/γ ratio) were also determined. The intrinsic light yield and light loss coefficient under excitation with 662 keV γ-rays were evaluated. The total attenuation coefficient at 60 keV and 662 keV γ - rays was also determined and compared with the theoretical one calculated using the WinXCom program. [ABSTRACT FROM AUTHOR]

This study presents luminescence and scintillation properties of Silver doped LiI crystals. Single crystals of LiI: x% Ag ( x =0.02, 0.05, 0.1 and 0.5) were grown by using the Bridgman technique. X-ray induced luminescence spectra show emission bands spanning from 275 nm to 675 nm, dominated by Ag + band having a peak at 300 nm. Under UV-luminescence, a similar emission band was observed with the peak excitation wavelength of 265 nm. Energy resolution, light yield and decay time profiles of the samples were measured under a 137 Cs γ-ray irradiation. The LiI(0.1%Ag) showed the highest light yield and the best energy resolution among the samples. The light yield of LiI(0.1%Ag) is higher than commercially available LiI(Eu) crystal (15,000±1500 ph/MeV). The LiI(Ag) samples exhibit three exponential decay time components except the LiI(0.02%Ag), where the fitting found two decay time components. Temperature dependences of emission spectra, light yield and decay time were studied from 300 K to 10 K. The LiI(0.1%Ag) crystal showed an increase in the light yield and a shortening of decay time with a decrease in temperature.. [ABSTRACT FROM AUTHOR]

The luminescent properties of LSO:Ce (1 mol%) scintillators were characterized systematically under vacuum ultraviolet (VUV)–UV excitation. Under 185 nm VUV excitation, a broad emission band was detected in the wavelength range from 350 nm to 600 nm at different temperatures, which is ascribed to the 5d→4f electron transitions of Ce 3+ . Excitation wavelength and temperature effects on luminescent properties of LSO:Ce ceramic scintillators were investigated in this paper. At 50 K, the emission intensity of Ce1 (Ce 3+ locating in seven-oxygen-coordinated site) was much stronger than that of Ce2 (Ce 3+ locating in six-oxygen-coordinated site), and the total emission intensity excited by 355 nm (Ce1) was higher than that excited by 185 nm (host). The total luminescence intensity increases as the rising temperature in the temperature range of 150–300 K, which is originated from thermal enhancement of transportation of free carriers dominating Ce1 emission. [ABSTRACT FROM AUTHOR]

The polydimethylsiloxane (PDMS) luminescence, induced by MeV proton beams, has been investigated in the pure and doped polymer. Gold nanoparticles (AuNPs) and graphene oxide microparticles (GO μ Ps) have been employed at low concentration (0.1 wt%) to modify the PDMS properties. Measurements have demonstrated that AuNPs enhance the PDMS luminescence, while GO μ Ps quench the polymer luminescence. The first ones, embedded into PDMS, produce a visible luminescence whose intensity is proportional to the absorbed proton dose. A linearity between the luminescence intensity and the proton absorbed dose is observed up to about 2.5 kGy, while at higher doses a luminescence saturation region shows up. The polymer can be employed to monitor in vacuum the proton beam spot size and shape and as a plastic scintillator dosimeter with peculiar elastic properties and high biocompatibility, as it will be presented and discussed. [ABSTRACT FROM AUTHOR]

The paper discusses scintillation and luminescence properties of thallium-doped LiI crystals, grown by the Bridgman technique. X-ray induced emission spectrum is obtained between 380 nm and 600 nm, and is attributed to the Tl + ion. The photoluminescence measurement with the excitation wavelength of 305 nm revealed a similar emission spectrum. Light yield, energy resolution and scintillation decay time profiles were studied under 662 keV ( 137 Cs) γ-ray excitation. A maximum light yield of 14,000±1400 ph/MeV and two exponential decay time components were obtained. [ABSTRACT FROM AUTHOR]

A microscale luminescence system was custom-built to investigate crystallinity, crystal quality, and emission homogeneity in scintillator crystals. This system consists of a fluorescence microscope that has been integrated with a spectrometer and custom-software for both manual and automated collection of two-dimensional reflection and emission images and maps of scintillators under excitation. The system’s capabilities are demonstrated through imaging studies on samples of CsBa 2 I 5 (2%Eu) (CBI), CsI (5%Ba, 3%Eu), and SrI 2 (5%Eu). Emission images obtained under 365 nm excitation reveal features that cannot be visualized using light microscopy alone. In the CBI samples, rod-like structures of 100–200 μm in diameter were observed. Using electron probe microanalysis (EPMA), these rods were found to be rich in barium and poor in cesium and europium. In CsI (Ba, Eu), oblong features were observed. Electron probe microanalysis confirmed that these regions varied in composition. Finally, an emission map of a one-inch diameter disk of SrI 2 (Eu) indicated a uniform distribution of the dopant. This study demonstrates that the microscale luminescence system is a valuable complement to the current suite of scintillator characterization tools. Its capabilities for evaluating crystal quality and homogeneity will provide useful feedback for crystal growth optimization. [ABSTRACT FROM AUTHOR]

In this study, the scintillation performance of Ce doped Cs 2 LiYCl 6 (CLYC) from −30 °C to 180 °C is presented. Pulse shape discrimination (PSD) of CLYC at various temperatures is investigated. Previously, it had been shown that PSD based on Core-Valence-Luminescence fades away at temperatures >120 °C. However, it has been discovered that there is a secondary mechanism which can be utilized for neutron-gamma Pulse Shape Discrimination in addition to the well-known Core-Valence-Luminescence (CVL). In contrast to CVL, this mechanism is found to be insensitive to temperature change. Temperature dependent PSD algorithms are developed to enable reliable neutron-gamma PSD up to 180 °C. [ABSTRACT FROM AUTHOR]

The Mg, Ca, Sr and Ba 200 ppm co-doped Ce:Lu 3 Al 5 O 12 single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The scintillation decays were accelerated by both Mg and Ca co-dopants. The Mg co-doped samples showed the fastest decay and the highest light yield among the co-doped samples. [ABSTRACT FROM AUTHOR]

Scintillation properties of CsI:In single crystals have been investigated. Scintillation yield of CsI:In measured with the 24μs integration time is around 27,000ph/MeV, reaching the saturation at 0.005mol% of the activator. However, luminescence yield of CsI:In is close to CsI:Tl scintillation crystals, which is around 60,000ph/MeV. This difference is explained by the presence of an ultra-long afterglow in CsI:In scintillation pulse. Thermoluminescence studies revealed a stable trap around 240K that is supposed to be related to millisecond decay components. The best measured energy resolution of (8.5±0.3)% was achieved at 24μs peaking time for a CsI sample doped with 0.01mol% of In. Temperature stability of CsI:In radioluminescence intensity was found to be remarkably high. Its X-ray luminescence yield remains stable up to 600K, whereafter thermal quenching occurs. The latter property gives CsI:In a potential to be used in well logging applications. [ABSTRACT FROM AUTHOR]

Zinc tungstate (ZnWO 4) crystal scintillators are promising detection material for the experiments searching for double beta decay, dark matter, and investigating rare alpha decays. An extended R&D was performed to develop advanced quality ZnWO 4 crystal scintillators. The R&D programme included the selection of the initial materials, the variation of the compound stoichiometry, the application of single and double crystallization, and the annealing of the crystal boules. The optical transmittance of the produced boules was measured, and the luminescence under X-ray excitation in the temperature region from 85 K to room temperature was studied (thermally stimulated luminescence was measured till 350 K). The energy resolution and the relative scintillation pulse amplitude were measured with gamma-sources demonstrating high scintillation properties of the samples produced by single crystallization from deeply purified zinc and tungsten oxides, with stoichiometric composition, annealed in air atmosphere. [ABSTRACT FROM AUTHOR]

This paper reports proton induced radiation damage in fast crystal scintillators. A 20 cm long LYSO crystal, a 15 cm long CeF 3 crystal and four liquid scintillator based sealed quartz capillaries were irradiated by 800 MeV protons at Los Alamos up to 3.3 × 10 14 p / cm 2 . Four 1.5 mm thick LYSO plates were irradiated by 24 GeV protons at CERN up to 6.9 × 10 15 p / cm 2 . The results show an excellent radiation hardness of LYSO crystals against charged hadrons. [ABSTRACT FROM AUTHOR]

A novel crystal scintillator of RbBa 2 I 5 :Eu 2 + was grown by the Bridgman–Stockbarger method. Its luminescence and scintillation properties were investigated. Under X-ray excitation, the crystal demonstrates blue luminescence peaking at 436 nm associated with 4f65d1 → 4f7 radiative transitions of Eu 2 + ions. The main X-ray luminescence decay constant is 800 ns. The light output of RbBa 2 I 5 :3%Eu 2 + sample under 662 keV excitation is 58,200 ph/MeV. • RbBa 2 I 5 :3%Eu 2 + crystal was grown using the Bridgman–Stockbarger technique. • Its luminescence and scintillation properties have been investigated. • Under 662 keV excitation, RbBa 2 I 5 :3%Eu 2 + showed a light output of 58,200 ph/MeV. [ABSTRACT FROM AUTHOR]

Fast scintillation materials based on ternary halide mixed crystals, Cs(Ca 1−x Mg x)Cl 3 , were synthesized. The luminescence at the defects or impurity sites within the band-gap excitation were observed. Upon X-ray excitation, bands corresponding to the intrinsic Auger-free luminescence (AFL) for CsCaCl 3 and CsMgCl 3 were observed, and the wavelength of the mixed crystals bands was similar to that of CsCaCl 3. Cs(Ca 1−x Mg x)Cl 3 exhibited a short decay time, which is typical for AFL in CsCl-based compounds, and CsMgCl 3 exhibited the shortest decay time of 1.1 ns and the smallest proportion of the first component (65%). On the other hand, CsCaCl 3 exhibited the longest decay time constant of 2.0 ns and the largest proportion of the first component (92%). The light yields of the fast components for CsCaCl 3 were larger than that of BaF 2 , whereas the light yields of the mixed crystals were lower than those of CsCaCl 3 and CsMgCl 3. The proportion of Cs/Mg in the mixed crystals was expected to affect the decay time constants and light yields, but changes in these properties did not vary much with Cs/Mg ratio. • Auger-free luminescence band was clearly observed under X-ray excitation for Cs(Ca 1−x Mg x)Cl 3. • Cs(Ca 1−x Mg x)Cl 3 exhibited short scintillation decay time constants of less than 2.0 ns. • The fast component light yields of CsCaCl 3 was larger than that of BaF 2 [ABSTRACT FROM AUTHOR]

The traditional CsI(Na) single crystal scintillator was studied to improve its scintillation properties, by co-doping Sodium with Europium and Indium ions. The growth was done by the Czochralski technique. Inductively coupled plasma optical emission spectroscopy and UV spectra including the absorption, excitation, and photoluminescence of the cut ingots were obtained in the region of 200 to 800 nm. The results show that the luminescence intensity of Europium-co-doped CsI(Na) is significantly increased compared to CsI(Na) single crystal, however Indium co-dopant has reduced the CsI(Na) luminescence intensity. Eu's high quantum emission efficiency due to its 4f → 5d internal transitions and the radiative energy transfer between Na + and Eu 2 + centers are the possible reason for this enhancement. While decreasing the CsI(Na) luminescence intensity, by adding the In co-dopant, is probably due to non-constructive spectral overlap between emission transition of In + and absorption transition of Na + which results in non-radiative energy transfer between Na + and In +. In this regard, the pulse height spectrum of these crystals was determined under the excitation of the gamma-ray sources. It is observed that Eu co-dopant strongly increases the scintillation light yield of the conventional CsI(Na) detector and improves its energy resolution, however In co-doped CsI(Na) reduces scintillation yield. [ABSTRACT FROM AUTHOR]