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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]

Abstract: Zinc selenide scintillation crystals isoelectronically doped with aluminum and oxygen by introducing Al2O3 into the charge were grown, and their emission was studied under photo- and X-ray- excitation, and comparison of their emission properties to those of the conventional scintillator ZnSe(Te) was accomplished. It is demonstrated that this technique for oxygen introduction enables the formation of oxygen-related deep donor–acceptor pairs (DAPs) acting as radiative recombination centers in ZnSe(O,Al) up to the densities exceeding the density of the corresponding Te-related DAPs in ZnSe(Te) at the doping level of 1wt%. ZnSe(O,Al) exhibits a higher photoluminescence intensity than that in ZnSe(Te) because of more efficient light absorption, while the photoluminescence quantum yield and the emission intensity under X-ray excitation show an opposite trend. [Copyright &y& Elsevier]

Abstract: Calcium metaborate CaB2O4 single crystals were grown by the Czochralski (CZ) method with the radio-frequency (RF) heating system. In these crystals, a plane cleavage was observed along the growth direction. The crystals had an 80% transparency, and no absorption bands were detected in the 190–900nm wavelength range. The 241Am 5.5MeV α-ray-excited radioluminescence spectrum of CaB2O4 demonstrated a broad intrinsic luminescence peak at 300–400nm, which originated from the lattice defects or an exciton-based emission. According to the pulse height spectrum, when irradiated by neutrons from a 252Cf source, the scintillation light yielded approximately 3200 photons per neutron (ph/n). [Copyright &y& Elsevier]

Abstract: Presently a growing interest to time-of-flight PET is observed in a number of experimental works using LSO as scintillation crystals. We propose to use as scintillators BaF2 crystals and ceramics produced from identical material but with essentially more high light yield in the fast component of emission spectra. A light yield amplification of BaF2 single crystal fast component of 2 to 2.5 times is achieved in crystals annealed in CF4 and doped by scandium at concentration of 0.5 to 2.0mol%. Ceramics from BaF2 doped by Sc have amplification factor order of 1.7 to 2.5. One can consider to produce scintillator of size 10×10×20mm3with an improved light transmission of ceramics in the range (200–250)nm up to single crystal level and with a light yield of 0.9ns component at the level of 3000 to 4000ph/MeV. Another promising scintillator obtained in our collaboration is BaF2:Tm3+. In this case one can have a scintillator in UV range with a time decay 0.9ns and a strongly decreased yield of BaF2 slow component. [Copyright &y& Elsevier]

Abstract: In this study, the scintillation properties of Eu2+ activated CsBa2Br5 are reported. It is an analog of Eu2+ doped CsBa2I5 scintillator that exhibits excellent scintillation properties. Microcrystalline powder samples of this compound were synthesized by reaction in the molten state of cesium bromide, barium bromide and europium bromide. The concentration of an Eu was varied from 0% to 10%. The luminescence was studied under UV and X-ray excitation. The light output is strongly Eu2+ concentration dependent, reaching an estimated maximum of about 92,000photons/MeV at 2% Eu under X-ray excitation. About 50% of the scintillation light decays in less than 1μs. CsBa2Br5:Eu2+ exhibits a complex concentration dependent emission centered around 435nm. [Copyright &y& Elsevier]

Abstract: We report the scintillation luminosities, decay times, and emission wavelengths for 19 Ce3+ activated scintillators, 18 Eu2+ activated scintillators, and 4 self-activated scintillators. Of these, 18 have not been previously reported either as phosphors or scintillators. Their luminosities range from 40,000 to under 1000photons/MeV. While these scintillators may not have properties that make them top candidates for widespread use, their data will contribute to a deeper understanding of factors that limit scintillator performance. [Copyright &y& Elsevier]

Abstract: In this paper we discuss two novel methods of measuring afterglow in scintillators. One method is designed for X-ray detection and the other for neutron detection applications. In the first method a commercial fan-beam scanner of basic design similar to those seen at airports is used to deliver a typically 12ms long X-ray pulse to a scintillator by passing the test equipment through the scanner on the conveyor belt. In the second method the thermal neutron beam from a research reactor is incident on the scintillator. The beam is cut-off in about 1ms using a 10B impregnated aluminum pneumatic shutter, and the afterglow is recorded on a dual range storage oscilloscope to capture both the steady state intensity and the weak decay. We describe these measurement methods and the results obtained for a range of developmental ceramic and glass scintillators, as well as some standard scintillators such as NaI(Tl), LiI(Eu) and the plastic scintillator NE102A. Preliminary modeling of the afterglow is presented. [Copyright &y& Elsevier]

Abstract: We have successfully grown crack free BSO (Bi4Si3O12) single crystal using Czochralski pulling technique. A detailed description of the crystal growth procedure and the solutions of the difficulties during the growth process are presented. Results of X-ray diffraction (XRD) showed a single phase of the grown crystal. Photoluminescence and X-rays induced emission spectrum showed a broad emission band in the wavelength range from 350 to 650nm. The energy resolution for 662keV gamma rays is measured to be 22% (FWHM) at room temperature. We measured a light output of 1400 photons/MeV for absorbed γ-ray energy. The decay time spectrum contained three components of 2.2ns (2%), 78.4ns (42%) and 125.6ns (56%) at room temperature. [Copyright &y& Elsevier]

Abstract: Nd 0.1, 1.1, 2, 4, and 6mol% doped YAG transparent ceramics are manufactured by the sintering method and their scintillation properties are compared with those of single crystalline Nd 1mol% doped YAG grown by the micro-pulling down method. They show ∼80% transmittance at wavelengths longer than 300nm and strong emission lines due to Nd3+ 4f–4f emission in their radio-luminescence spectra. Among them, the single crystalline sample shows the highest light yield of 11,000ph/MeV under γ-ray excitation and the second highest one is from Nd 1.1mol% doped transparent ceramic, which shows 6000ph/MeV. In these scintillators, dominant decay time constant is around 2–3μs due to Nd3+ 4f–4f transitions. [Copyright &y& Elsevier]

Abstract: Red Bi4Ge3O12 (BGO) crystals were obtained by the vertical Bridgman method. The absorption/transmittance spectra of red BGO in the visible and near-infrared (NIR) regions were measured at room temperature. The luminescence and decay time in the NIR region were then measured down to a temperature of 8K. A broad emission band was found at approximately 1150nm at T<200K, and the luminescence lifetime was measured at several hundred microseconds. Decreased temperature led to increased luminescence intensity. We report that red BGO is a promising cryogenic scintillator for experimental rare-event research. [Copyright &y& Elsevier]

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]

Abstract: The crystal growth and scintillation properties of Ba2CsI5:Eu2+ are reported. Crystals were produced by the vertical Bridgman technique in a sealed quartz ampoule. Ba2CsI5:Eu2+ presents excellent scintillation properties. An estimated light yield of 97,000±5,000 photons per MeV (ph/MeV) of absorbed gamma-ray energy was measured. An energy resolution (FWHM over peak position) of 3.8±0.3% was observed for the 662keV full absorption peak. Pulsed X-ray luminescence measurements show a relatively complex time response with four exponential decay components of 48,383, 1500 and 9900ns with a contribution to the total light output of 1%, 26%, 68% and 25%, respectively. Under X-ray and UV excitation, the emission corresponds to a broadband centered at 2.85eV. First principles calculations show strong localization of the excited state on the Eu site. Ba2CsI5:Eu2+ has a density of about 5g/cm3. These first reported scintillation properties make Ba2CsI5:Eu2+ a very high-performance scintillator. [Copyright &y& Elsevier]

Abstract: This paper presents the growth of negative ions (F−, Cl−, I− and S2−)-doped PbWO4 crystals by the modified Bridgman method and the influence of negative ions doping on the scintillation properties of PbWO4 crystals. Based on the results of measuring the optical transmission, X-ray excited luminescence, light yield and decay time of negative ion-doped and non-doped PbWO4 crystals, it can been seen that at the concentration involved in the study F− ion greatly increased the luminescence intensity and light yield of PbWO4 crystals. Compared to non-doped PbWO4 crystals, however, F− doping results in a relatively slower decay component. The doping of Cl− and I− ions causes no evidently positive improvement on the scintillation properties of PbWO4 crystals, and doping of S2− ion jeopardizes the scintillation properties of PbWO4 crystals. [Copyright &y& Elsevier]

Abstract: We have manufactured thallium-doped cesium iodide (CsI:Tl) scintillator thin films by the thermal deposition method. The scintillation characteristics of the CsI:Tl thin films were studied by X-ray-induced luminescence for different Tl doping concentrations between 0.05 and 1.0mol%. The wavelength of the main emission peak was about 550nm and the light intensity was increased and the emission peak shifted toward the long wavelength for higher Tl concentration in the X-ray luminescence case. X-ray diffraction (XRD) and scanning electron microscopy (SEM) for observation of structural properties was used to investigate the relationship between the microstructure affected by the evaporation condition and post-heat treatment, and the scintillation properties of samples. The imaging performance of the various CsI:Tl films fabricated will also be evaluated by an X-ray radiographic test after coupling to a CCD sensor. [Copyright &y& Elsevier]

Abstract: We report on several methods for synthesizing the ultra-fast scintillator ZnO(Ga), and measurements of the resulting products. This material has characteristics that make it an excellent alpha detector for tagging the time and direction of individual neutrons produced by t–d and d–d neutron generators (associated particle imaging). The intensity and decay time are strongly dependent on the method used for dopant incorporation. We compare samples made by diffusion of Ga metal to samples made by solid-state reaction between ZnO and Ga2O3 followed by reduction in hydrogen. The latter is much more successful and has a pure, strong near-band-edge fluorescence and an ultra-fast decay time of the X-ray-excited luminescence. The luminescence increases dramatically as the temperature is reduced to 10K. We also present results of an alternate low-temperature synthesis that produces luminescent particles with a more uniform size distribution. We examine possible mechanisms for the bright near-band-edge scintillation and favor the explanation that it is due to the recombination of Ga3+ donor electrons with ionization holes trapped on H+ ion acceptors. [Copyright &y& Elsevier]

Abstract: This paper concerns the influence of wavelength shifting (secondary) luminescent additive (LA2) on the light yield of polystyrene-based plastic scintillator (PS) taking self-absorption into account. Calculations of light yield dependence on concentration of 1.4-bis(2-(5-phenyloxazolyl)-benzene (POPOP) as LA2 were made for various path lengths of photons in PS. It is shown that there is an optimal POPOP concentration (C opt), which provides a maximum light yield for a given path length. This optimal concentration is determined by the competition of luminescence and self-reflection processes. C opt values were calculated for PS of different dimensions. For small PS, C opt≈0.02%, which agree with a common (standard) value of POPOP concentration. For higher PS dimensions, the optimal POPOP concentration is decreased (to C opt≈0.006% for 320×30×2cm sample), reducing the light yield from PS by almost 35%. [Copyright &y& Elsevier]

Abstract: A coded mask instrument based on Silicon Drift Detectors coupled to scintillators operated with a pulse shape discrimination technique is presented as a candidate wide field monitor for forthcoming gamma-ray burst (GRB) search missions. Such an instrument would allow an energy range extended from 1keV to 1MeV, in a single compact device, providing both a significant detection efficiency for the softest GRB (X-ray flashes), and the sensitivity to high energy necessary to constrain GRB spectral parameters. [Copyright &y& Elsevier]

Abstract: For a multi-layer depth-of-interaction (DOI) detector using different decay times, pulse shape analysis based on two different integration times is often used to distinguish scintillators in DOI direction. This method measures a partial integration and a full integration, and calculates the ratio of these two to obtain the pulse shape distribution. The full integration time is usually set to integrate full width of the scintillation pulse. However, the optimum partial integration time is not obvious for obtaining the best separation of the pulse shape distribution. To make it clear, a theoretical analysis and experiments were conducted for pulse shape analysis by changing the partial integration time using a scintillation detector of GSOs with different amount of Ce. A scintillation detector with 1-in. round photomultiplier tube (PMT) optically coupled GSO of 1.5mol% (decay time: 35ns) and that of 0.5mol% (decay time: 60ns) was used for the experiments. The signal from PMT was digitally integrated with partial (50–150ns) and full (160ns) integration times and ratio of these two was calculated to obtain the pulse shape distribution. In the theoretical analysis, partial integration time of 50ns showed largest distance between two peaks of the pulse shape distribution. In the experiments, it showed maximum at 70–80ns of partial integration time. The peak to valley ratio showed the maximum at 120–130ns. Because the separation of two peaks is determined by the peak to valley ratio, we conclude the optimum partial integration time for these combinations of GSOs is around 120–130ns, relatively longer than the expected value. [Copyright &y& Elsevier]

Abstract: Results are presented of measurements of high-energy hadronic shower profiles with a copper-based fiber calorimeter. This calorimeter was equipped with a mixture of scintillating fibers and undoped (quartz or plastic) fibers. The latter measured the spatial distribution of shower particles with velocities above the Cherenkov threshold, whereas the scintillating fibers measured the distribution of the deposited energy. Both the lateral and longitudinal characteristics of these profiles were measured for pions, with energies ranging from 20 to 300GeV. The scintillator and Cherenkov profiles exhibit some striking differences, which are discussed and compared with results of Monte Carlo simulations. [Copyright &y& Elsevier]

Abstract: We have studied the energy resolution, ratio, temperature dependence of the scintillation properties, and the radioactive contamination of CaMoO4 crystal scintillators. We have also examined the use of pulse-shape discrimination to distinguish rays and particles. A high sensitivity experiment to search for the decay of using CaMoO4 scintillators is discussed. [Copyright &y& Elsevier]

Abstract: As a novel scintillation material, the use of Ce-doped Gd2Si2O7 was investigated. In fact, (Gd0.9Ce0.1)2Si2O7 powder showed about 1.2 times greater light output than Gd2SiO5 (GSO) single crystals for alpha particles of 241Am. Furthermore, a fast decay constant of 52ns was obtained for alpha-particles of 241Am. Relations between the Ce concentration, crystal structure, and luminescence characteristics were also elucidated. Results of these studies show that heavy Ce doping alters the Gd2Si2O7 crystal structure and that the luminescence intensity is dependent not on Ce concentration, but on the triclinic structure formed by heavy Ce doping. [Copyright &y& Elsevier]

Abstract: In the framework of an assessment of lanthanum halide scintillators, such as LaBr3:Ce and LaCl3:Ce on their suitability for space based gamma-ray spectroscopy, proton induced activation of the materials has been studied. One inch scintillators were subjected to proton irradiations in the range of 60–184MeV, where after the activation was measured. The activation was analyzed by identifying the decaying isotopes by means of gamma-ray spectroscopy and lifetime measurements using both a germanium detector and the activated scintillator itself. It was found that the dominant source of activation in the scintillators originates from the lighter elements in the materials: bromide and chloride, respectively. The activation of LaBr3:Ce manifest itself through gamma-decay, which partly leaves the volume. Activation of LaCl3:Ce originates mainly from beta decay, which is confined to the volume itself. [Copyright &y& Elsevier]

Abstract: It is known that the impurities In in CdS and Ga in ZnO act as donors to generate a population of electrons near the bottom of the conduction band. Fast luminescence is observed from these materials but the intensity of the luminescence is strongly dependent on the method used for dopant incorporation. Therefore, it is suspected that an additional dopant is responsible for trapping ionization holes and promoting rapid radiative recombination and these compete with native non-radiative centers. To verify this conjecture and to optimize the luminosity of this class of scintillators, we have been exploring the possibility of introducing dopants that act as efficient hole traps and radiative centers. In this work, we report on the luminosities and decay times of crystalline powders of ZnO doped with the donor Ga3+ and treated with H, doped with the acceptor N3− and with the isoelectronic hole trap S2−. Co-doped samples exhibit a large increase in luminosity and a fast mono-exponential decay. We also report on PbI2 doped with the donors Bi3+, La3+, and In3+ and co-doped with Ga3+ and P3−. PbI2 is dense (d=6.2g/cm3) and is a candidate material for gamma-ray detection. [Copyright &y& Elsevier]

Abstract: We report the scintillation properties of a new material, K2CeCl5, which was grown by vertical Bridgman technique. Under excitation of 4.5MeV α-particles, the Ce3+ emission had a single peak centered at 370nm with a width of 20nm. The scintillation light output was estimated to be ∼30,000photons/MeV for γ excitation at 662keV and ∼24,000photons/MeV γ equivalent (assuming an α/γ ratio of 0.34) under α excitation. The smaller light yield for αs can be partly explained by surface damage of the sample during polishing and subsequent partial oxidation of the Ce luminescence centers. The energy resolution at 662keV was measured to be about 5.8%. Importantly, K2CeCl5 is found to be much less hygroscopic than lanthanum halide scintillators and may therefore preferred in applications where enclosing the material is not feasible. [Copyright &y& Elsevier]

Abstract: For rapid, unambiguous isotope identification, scintillator detectors providing high-resolution gamma ray spectra are required. We have fabricated Lutetium Aluminum Garnet (LuAG) using transparent ceramic processing, and report a 2-mm thick ceramic exhibiting 75% transmission and light yield comparable to single-crystal LuAG:Ce. The LuAG:Ce luminescence peaks at 550nm, providing an excellent match for Silicon Photodiode readout. LuAG is dense (6.67g/cm3) and impervious to water, exhibits good proportionality and a fast decay (∼40ns), and we measure light yields in excess of 20,000 photons/MeV. [Copyright &y& Elsevier]

Abstract: A novel class of scintillating materials, which are nanocomposites of known scintillators, is described. These nanocomposite materials are expected to have improved properties with respect to the properties of the bulk scintillators from which they are derived. Improvements include enhanced light output, reduced cost and greater size scalability. Optical properties of the nanocomposite phosphor components are described, with emphasis on the origin of the enhanced light yield. Finally, results from our first nanocomposite scintillator, including photopeak measurements, are described. The photopeak measurements demonstrate the proof-of-principle of the nanocomposite scintillator concept. [Copyright &y& Elsevier]

Abstract: The spatial, energy, and time resolutions of 10cm long polished YAP:Ce and LYSO:Ce crystals have been measured. The work is part of the novel HPD-PET concept, based on a full three-dimensional, free of parallax errors, reconstruction of the γ-ray interaction point in 10–15cm long scintillators. The effective light attenuation length, a key parameter of the HPD-PET concept, and the resolutions have been measured for various wrappings and coatings of the crystal lateral surfaces. Even if the final HPD-PET prototype could use scintillators and/or wrappings different from those tested, the results here presented prove the feasibility of the concept and provide hints on its potential capabilities. [Copyright &y& Elsevier]

Abstract: The Monte-Carlo refractive index matching (MCRIM) technique was developed to determine the physical properties of heavy inorganic scintillators (HIS) which are difficult to measure experimentally. It was designed as a method for obtaining input parameters for Monte-Carlo (MC) simulations of experimental arrangements incorporating HIS in their setups. The MCRIM technique is used to estimate the intrinsic light yield, the scattering coefficient and the absorption coefficient, herein referred to as indirect measurement properties. The MCRIM technique uses an experiment/MC combination to determine these indirect measurement properties. The MCRIM experimental setup comprises a crystal placed on a photomultiplier tube window with the possibility of introducing materials of different refractive indices in a small gap between the crystal and photomultiplier tube (PMT) window. The dependence of the measured light yield on the refractive index of the material in the gap can only be reproduced by simulations if the correct values of scattering, absorption and intrinsic light yield are used. The experimental setup is designed to minimise the presence of optical components such as unpolished surfaces and non-ideal reflectors, which are difficult to simulate. The MCRIM technique is tested on a 1.03×1.00×0.82cm3 crystal of CaWO4 which is found to have a scattering coefficient of 0.061±0.005cm−1, an absorption coefficient of 0.065±0.005cm−1, and an intrinsic light yield of 22700±1700 photons/MeV. [Copyright &y& Elsevier]

Abstract: We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to readout the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal. Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10–30keV energy range. The scintillation light was readout with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT. [Copyright &y& Elsevier]

Abstract: Lutetium–yttrium-based scintillators, such as LYSO:Ce, have a high effective atomic number, are non-hygroscopic, fast emitting materials, and promising candidates for use in positron emission imagers. The present study investigates the light emission characteristics of (Lu, Y)2SiO5:Ce (LYSO:Ce) single-crystal scintillator under X-ray imaging conditions. Also, the parameters related to the luminescence emission spectrum and emission efficiency were studied using experimental methods. Various X-ray tube voltages currently employed in X-ray imaging techniques were used. Measurements were performed using an experimental set-up based on a photomultiplier coupled to an integration sphere. In addition, the emission spectrum under UV and X-ray excitation was measured using an optical grating monochromator to determine the spectral compatibility of optical photon detectors incorporated in medical imaging systems. The absolute efficiency of LYSO:Ce was found to increase with increasing X-ray tube voltage (from 2.2EU at 22kVp to 22.4EU at 140kVp), while its spectrum, peaking at about 430nm, was found compatible with most optical detectors (photodiodes, photocathodes, charge coupled devices, etc.). The matching factor was estimated to range from 0.76 to 0.92 (for a silicon photodiode and for a GaAsP photocathode, respectively). [Copyright &y& Elsevier]

Abstract: X-ray absorption and X-ray fluorescence properties of medical imaging scintillating screens were studied by Monte Carlo methods as a function of the incident photon energy and screen-coating thickness. The scintillating materials examined were Gd2O2S, (GOS) Gd2SiO5 (GSO) YAlO3 (YAP), Y3Al5O12 (YAG), LuSiO5 (LSO), LuAlO3 (LuAP) and ZnS. Monoenergetic photon exposures were modeled in the range from 10 to 100keV. The corresponding ranges of coating thicknesses of the investigated scintillating screens ranged up to 200mgcm−2. Results indicated that X-ray absorption and X-ray fluorescence are affected by the incident photon energy and the screen''s coating thickness. Regarding incident photon energy, this X-ray absorption and fluorescence was found to exhibit very intense changes near the corresponding K edge of the heaviest element in the screen''s scintillating material. Regarding coating thickness, thicker screens exhibited higher X-ray absorption and X-ray fluorescence. Results also indicated that a significant fraction of the generated X-ray fluorescent quanta escape from the scintillating screen. This fraction was found to increase with screen''s coating thickness. At the energy range studied, most of the incident photons were found to be absorbed via one-hit photoelectric effect. As a result, the reabsorption of scattered radiation was found to be of rather minor importance; nevertheless this was found to increase with the screen''s coating thickness. Differences in X-ray absorption and X-ray fluorescence were found among the various scintillators studied. LSO scintillator was found to be the most attractive material for use in many X-ray imaging applications, exhibiting the best absorption properties in the largest part of the energy range studied. Y-based scintillators were also found to be of significant absorption performance within the low energy ranges. [Copyright &y& Elsevier]

Abstract: We report upon the performance of an analog hadron calorimeter prototype, where plastic scintillator tiles are read out with wavelength-shifting fibers coupled to avalanche photodiodes. This prototype configuration has been tested using a positron beam at DESY with energies between 1 and 6GeV. We present different detector calibration methods, show measurements for noise, linearity, and energy resolution and discuss gain monitoring with an LED system. The results are in good agreement with our simulation studies and previous measurements using silicon photomultiplier readout. [Copyright &y& Elsevier]

Abstract: The purpose of the present study was to evaluate, under X-ray medical imaging conditions, the X-ray luminescence efficiency (XLE) and the optical quantum gain (OQG) of the Gd2SiO5:Ce scintillator in single crystal form, suitable for tomographic applications. Intrinsic physical properties and light emission characteristics of the Gd2SiO5:Ce scintillator, were also studied. Both experimental and Monte Carlo techniques were used. Various X-ray tube voltages (40–140kV), currently employed in X-ray imaging applications, were used. XLE was found to vary slowly with X-ray tube voltage from (0.021±0.003) to (0.017±0.003). OQG varied from (317±18) to (466±23) light photons per incident X-ray. These values were adequately high for imaging applications using the particular energy range. Additionally, it was found by Monte Carlo simulations that for crystal thicknesses higher than 0.5cm both XLE and OQG reached saturation levels, indicating that higher thickness crystals are of no practical use in X-ray medical imaging. [Copyright &y& Elsevier]