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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]

Lu2O3:Eu3+ nanowire arrays were synthesized by the sol–gel immersion method using anodic aluminum oxide (AAO) templates. The influence of annealing temperature on the morphology, crystallinity, luminescence, and transmittance of the Lu2O3:Eu3+ nanowire arrays in the AAO templates was studied. The results show that the nanowires in the AAO templates are dense and orderly. Their diameters are uniform and defined by the templates. As annealing temperature increases from 500 °C to 900 °C, the shape of the nanowires remains substantially unchanged, but the crystallinity is greatly improved. When the annealing temperature reaches 1000 °C, the AAO template begins to crystallize and the samples begin to deform or even crack. In view of the fact that a scintillation screen for X-ray imaging requires not only high luminous intensity but also high transparency, no deformation, and no crack, the suitable annealing temperature for synthesizing the screen of a Lu2O3:Eu3+ nanowire array in the AAO template was obtained. [ABSTRACT FROM AUTHOR]

In this article, single crystals of a new nonhygroscopic scintillating material of tetrafluoroaluminate (TlAlF4) were grown using the Bridgman–Stockbarger technique. The diffraction pattern obtained from powder X-ray diffraction was found to be in good agreement with the reference data. The X-ray-induced luminescence measurements of the grown crystal sample exhibit a very strong intrinsic emission band in the wavelength range from 300 to 450 nm, with a peak maximum at 390 nm. Scintillation properties, such as pulse height spectra and decay time of the grown crystals, were investigated using γ-rays from the 137Cs radiation source. The scintillation light yield was found to be ~11 800 ph/MeV. At room temperature, the measured decay time profile was fitted with three exponential functions; the result showed a fast component of 194 ns (13.1%), a medium component of 992 ns (84.6%), and a slow component of 3.5 μs (2.3%). Trap centers were studied using the results obtained from thermally stimulated luminescence. The temperature dependence of the scintillation light yield and decay time was also studied. The results showed that TlAlF4 is a promising scintillator crystal, and thus, a potential candidate for X-ray and γ-ray detection. [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]

We fabricate thin films of lead halide perovskite nanocrystals on glass substrates and cerium-doped LYSO substrates (lutetium-yttrium oxyorthosilicate, LuxY2-xSiO5:Ce) using spin-coating and drop-casting methods, respectively. We study their structural and optical properties. The luminescence and scintillation are monitored in both steady-state and time-resolved regimes. We focus on the possibility to exploit these structures in designing a detection system with ultrafast time resolution. [ABSTRACT FROM AUTHOR]

The lead tungstate crystal (PbWO4, PWO) is one of the widely used scintillation materials for electromagnetic calorimeters (EMCs) in high-energy physics experiments. The degradation of the optical transmittance in the range of the luminescence spectrum under ionizing radiation leads to losses of the light output resulting in the deterioration of the energy resolution and limiting the lifetime of the calorimeter. A possible way to restore radiation damage is the in situ illumination by visible or near-infrared light of the whole crystal volume. It allows recovering the transmittance losses due to the depopulation of the color centers. Such a kind of stimulated recovery subsystem based on a blue light-emitting diode is considered for the EMC of the PANDA detector at Facility for Antiproton and Ion Research (FAIR) (Darmstadt, Germany). Here, we report on the stimulated recovery studies of the lead tungstate radiation damage induced by external light from laser diodes at different wavelengths. The level of technological development of laser diodes allows increasing the efficiency of the stimulated recovery. [ABSTRACT FROM AUTHOR]

Scintillation characteristics of Y0.8Gd2.2 (Al5–xGax)O12:Ce,Mg (x = 2.6 and 3) single crystals are presented. At 662-keV γ-rays, the light yield of 35 600 photons/MeV obtained for Y0.8Gd2.2Al2Ga3O12:Ce,Mg is higher than that of 32 600 photons/MeV for Y0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. Scintillation decay components of 32.3 ns (52.4%) + 104 ns (47.6%) obtained for Y0.8Gd2.2Al2Ga3O12:Ce,Mg are faster than those of 11.5 ns (5%) + 51.2 ns (69%) + 302 ns (26%) obtained for Y0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg. The coincidence time resolution of 336 and 389 ps was obtained, respectively, for Y0.8Gd2.2Al2Ga3O12:Ce,Mg-photomultiplier (PMT) and Y0.8Gd2.2Al2.4Ga2.6O12:Ce,Mg-PMT, in coincidence experiment with a BaF2-PMT detector. The radioluminescence yield at room temperature (RT) is comparable for both crystals while the yield below 130 K is about 20% higher for Y0.8Gd2.2Al2Ga3O12:Ce,Mg. Afterglow and thermally stimulated luminescence (TSL) below RT are also measured. [ABSTRACT FROM AUTHOR]

Scintillators with ultrafast response are of demand in medical imaging for time-of-flight positron emission tomography, in high-energy physics calorimetry, and in other applications. There are several fast luminescence processes in solid-state materials, which could be good candidates for fast timing applications. The development of new ultrafast silicon photomultipliers with increased vacuum-ultraviolet to ultraviolet (VUV-UV) sensitivity has renewed interest to one of those, cross-luminescence (CL), emitted in the VUV-UV region with subnanosecond decay time. Previous investigations have shown that CL is mostly situated in the VUV region in binary K and Ba compounds, but ternary fluorides with a complex valence band structure can provide ultrafast emissions in UV. According to the band structure calculations for K2SiF6, its complex valence band is composed of the F 2p, Si 2s, and Si 2p states. Transitions between the valence subbands and the outermost K 3p core band may extend CL from the VUV-UV to the visible region. This motivated us to perform spectroscopic study of phase-pure K2SiF6 micropowders with a high degree of crystallinity. The stationary (10 keV) and pulsed (100 keV, δ t ≈ 55 ps) electron beams were applied in the studies of relaxation processes of K2SiF6 in the temperature range of 77–300 K. At 300 K, the dynamics of ultrafast processes was studied at the FemtoMAX beamline (MAX IV Lab) providing 10-keV X-ray pulses of 100-fs duration. As a result, we revealed multiple CL bands extending from 9 to 4 eV. A nonexponential decay in the subnanosecond time range was revealed for the CL bands at 4.5 and 5.25 eV under both pulsed electron-beam and X-ray excitations. This opens prospects for a band structure engineering approach in developing new ultrafast scintillators with intrinsic emissions. This approach is based on a targeted modification of material composition to influence the density of states in complex valence bands and to provide a favorable shift of CL to lower energies. [ABSTRACT FROM AUTHOR]

This article presents the measurements of the luminescence and scintillation under X-ray of undoped, Si-doped, and Si, B codoped gallium-arsenide (GaAs) samples at cryogenic temperature over a wide infrared (IR) region using Si and InGaAs photodetectors. The undoped GaAs has a narrow emission band at 838 nm (1.48 eV) and a low light output of about 2 ph/keV. The GaAs:Si has three broad luminescence bands at 830 nm (1.49 eV), 1070 nm (1.16 eV), and 1335 nm (0.93 eV) and a light output of about 67 ph/keV. GaAs:(Si, B) has four luminescence bands at 860 nm (1.44 eV), 930 nm (1.33 eV), 1070 nm (1.16 eV), and 1335 nm (0.93 eV) with a light yield of approximately 119 ph/keV. With advances in photodetection, GaAs promises to be a useful cryogenic scintillator for the detection of electron recoils from MeV/c2 dark matter. [ABSTRACT FROM AUTHOR]

Nondoped Cs2HfCl6 (CHC) and alkaline earth metal-doped CHC (AE:CHC) crystals were grown by the vertical Bridgman–Stockbarger method. The spectra of the AE:CHC under X-ray excitation were similar to those for the AE-free crystal; thus, AE doping did not change emission wavelength of CHC. We determined the light outputs and energy resolutions of nondoped CHC and AE:CHC by measuring pulse-height spectra under 662-keV gamma-ray excitation of a 137Cs source. Both light output and energy resolution were deteriorated with AE doping. For example, nondoped CHC had a light output of ~44 000 photons/MeV and energy resolution of ~5.2%; on the other hand, Sr 0.5 at.%-doped CHC had a light output of only ~28 000 photons/MeV and energy resolution of ~10%. Scintillation decay also did not change. The nonproportional response values of light output versus gamma-ray energy did not improve in AE:CHC either. Therefore, doped AEs can be responsible for creation of defect trap levels which would hamper the carrier transport in CHC structure. [ABSTRACT FROM AUTHOR]

Submicrometer diameter phase-separated scintillator fibers (PSSFs) were reported and they possessed both the properties of an optical fiber and radiation-to-light conversion. The PSSFs were fabricated using a directionally solidified eutectic system. High-resolution X-ray imaging can be developed using the PSSFs. In this paper, Tb- and Eu-doped GdAlO3 (GAP)/ $\alpha $ -Al2O3 eutectic scintillator was grown by the micro pulling down method with various growth rates in order to achieve the high light output and the high light-guiding efficiency. Relationship between radioluminescence intensity and dopant concentration of Eu and Tb was investigated. At the optimized dopant concentration, relationship between growth rate, eutectic period structure, diameter of PSSFs, and contrast transfer function was investigated to achieve high-resolution X-ray imaging. [ABSTRACT FROM AUTHOR]

This paper presents our achievement in the development of new types of advanced composite scintillators (CSs) based on the single crystalline films (SCFs) of Lu3Al5O12 (LuAG) garnet, doped with Pr3+ and Sc3+ ions, and substrate from single crystals (SCs) of Ce3+-doped LuAG using the technology of liquid phase epitaxy. We show the possibility of the simultaneous registration of $\alpha$ -particles and $\gamma$ -quanta by means of separation of the decay kinetics of SCF and crystal parts of such CSs. Namely, the significant differences in the scintillation decay kinetics of LuAG:Pr SCF/LuAG:Ce SC and LuAG:Sc SCF/LuAG:Ce SC CSs under excitation by $\alpha$ -particles of 241Am (5.5 MeV) source and $\gamma$ -quanta of 137Cs (662 keV) source are observed. Thus, such types of CSs can be successfully applied for separation of the signals coming from their film and crystal parts at the registration of the mixed radiation fluxes of $\alpha$ -particles and $\gamma$ -quanta. [ABSTRACT FROM AUTHOR]

A novel TlGd2Cl7 single crystal with scintillation properties is presented. TlGd2Cl7 single crystals with different Ce3+-doping concentrations (0, 0.5, 1, and 5 mol%) are grown using the vertical Bridgman technique. All doped samples exhibit typical Ce3+ emission under X-ray excitation between 350 and 550 nm. Among all grown samples, the best light yield (LY) of ~49 700 photons/MeV and good energy resolution of 6% (full-width at half-maximum) are observed for the 5-mol%-Ce3+-doped TlGd2Cl7 crystal under an excitation of 662-keV $\gamma $ -rays at room temperature. Three exponential decay components are observed for all Ce3+- doped samples at room temperature. Faster decays are observed with the increase in the Ce3+ concentration. The effective atomic (Z) number of the proposed crystal is 64; therefore, efficient X- and $\gamma $ -ray detections could be performed with the proposed scintillator. The high LY, high effective Z number, good energy resolution, and fast scintillation response suggest that this scintillator could be employed in various applications. Further investigations are ongoing for the improvement of its scintillation properties with a higher Ce3+ concentration. [ABSTRACT FROM AUTHOR]

We are in the process of developing novel thallium-based inorganic halide compounds for X- and $\gamma $ -ray radiation detections. In this paper, novel cerium-activated single crystals of Tl2GdCl5 are reported along with a pure Tl2GdCl5. The two-zone vertical Bridgman method is used to grow this scintillator from its melt. Luminescence studies are performed under ultraviolet and X-ray excitations at room temperature. All of the Ce-activated samples exhibit similar emission bands in the range of 350–430 nm, with a peak around 388 nm, attributed to the $5d~\to ~4f$ radiative transition of the Ce3+ ion. In the pure sample, an intense luminescence band appeared owing to the presence of the Tl+ ion in the host lattice, along with the typical Gd3+ emission (~310 nm). Scintillation properties, such as energy resolution, light yield, and decay time, are evaluated under the $\gamma $ -ray excitation. The scintillation properties vary with the Ce3+-concentration. The best performances are obtained for the 5-mol% Ce-activated crystal, which, under a 662-keV $\gamma $ -ray excitation, exhibited an energy resolution of 5% (full-width at half-maximum) and light yield of 53 000 ± 5300 ph/MeV. Fast scintillation decay components followed by slow components are observed for all grown samples. The measured scintillation properties of Tl2GdCl5, which has high density and effective Z-number, reveal its large potentials as a radiation detector in medical imaging techniques. [ABSTRACT FROM AUTHOR]

The luminescence and scintillation properties of novel Na2Mo2O7 (NMO) crystals grown by two different techniques, the conventional Czochralski and the low-thermal-gradient Czochralski techniques, were studied. The transmittances of the NMO crystals were measured at room temperature. The luminescence properties and decay times of the crystals from room temperature 300 to 10 K were measured by using an LED diode emitting at the wavelength of 280 nm. Very weak luminescence was observed at the room temperature. The luminescence, however, was enhanced significantly at lower temperatures. The crystals showed a red emission peak of 663 nm at 10 K. The scintillation decay time was $2~\mu \text{s}$ at room temperature and was increased to $\sim 750~\mu \text{s}$ at 10 K. Low-temperature thermally stimulated luminescence measurements were carried out to investigate the presence of trap centers in the grown crystal. The scintillation light yield of the scintillator was measured by a photon counting technique using a 90Sr beta source in the same temperature range from 300 to 10 K. The light yields of the NMO crystals grown at two different institutes were also compared with a standard CaMoO4 crystal. [ABSTRACT FROM AUTHOR]

A Cs2Mo2O7 single crystal, a molybdenum-based crystal as research and development scintillation material for future neutrinoless double beta decay experiments under milli-Kelvin temperatures, was grown by the Czochralski method. The grown crystal was prepared as a sample for measurements of its optical properties. The sample was cooled down from room temperature to 10 K, and temperature dependence of emission spectrum and decay time were measured. We used a light emitting diode as an excitation source for the emission spectra measurements and a pulsed-type laser for the decay time due to its high intensity. The intensity of emission spectrum and the decay time increased as the temperature decreased. We estimated the optical energy bandgap via a transmittance measurement at room temperature. As far as we know, it is the first time to grow a large Cs2Mo2O7 crystal and to study its luminescence properties. Moreover, we grew a well-studied Li2MoO4 crystal as a reference to compare the light output of the Cs2Mo2O7 at 10 K. Through these results, the Cs2Mo2O7 crystal found to be a candidate scintillator for the future neutrinoless double beta decay experiments. [ABSTRACT FROM AUTHOR]

Cerium-doped mixed oxide garnets are promising luminescent materials to use as LED phosphors or scintillators for radiation detectors. In this paper, temperature-dependent characteristics of Ce-doped multicomponent garnets ceramics have been studied under photo and X-ray excitation. Ceramic samples of Y3GaxAl5−xO12:Ce0.006 ($x = 1$ , 2, 3, and 4) and of Gd3GaxAl5−xO12:Ce0.006 ($x = 1$ , 2, and 3) have been used. At high temperature, all samples showed decrease in the Ce3+ luminescence intensity, luminescence decay, and luminescence lifetime due to thermal ionization of Ce3+ excited 5d states. Values of activation energies of the thermal ionization process have been determined from photoluminescence lifetime measurements and shown in comparison with literature data. At low temperature, Gd-containing samples showed significant decrease in light output. In the same temperature range, large thermoluminescence peaks have been observed, indicating that the reduction of Ce3+ emission at low temperatures can be attributed to the localization of charge carriers on traps. [ABSTRACT FROM AUTHOR]

Optical absorption, luminescence spectra, scintillation decay curves, and scintillation light yield were measured in a series of undoped yttrium–aluminum garnet (YAG) crystals of different origins. This paper reveals a correlation between luminescent properties and scintillation efficiency of undoped YAG crystals. All the samples were separated into three groups, Type I, Type II, and Type III, based on their optical properties and scintillation efficiency. The intrinsic ultraviolet luminescence band peaking around 300 nm is found in the samples with high scintillation yield (Type I). Luminescence intensity of this band depends on the crystal purity and on the stoichiometry of the garnets. The UV emission may be related to e–h recombination in vicinity of vacancies. The garnets of Type II contain more impurities which quench the 300-nm emission. The samples of Type III do not exhibit any significant radioluminescence. Light yield of the finest undoped YAG samples in the series, Type I, is similar to the yield of Ce-doped YAG. This Type of crystals can potentially be used in scintillation detectors. [ABSTRACT FROM AUTHOR]

Mixed crystals Li6YxGd1–x(BO3)3:Ce3+ (LYGBO) (where, x = 0.0, 0.2, 0.5, 0.8, 1.0) are grown by using Czochralski method with different proportions of Li6Y(BO3)3 and Li6Gd(BO3)3. All crystals are doped with 3 mole% optimized concentrations of Ce3+ ions. The grown crystals are 20–70 mm in length and 5–10 mm in diameter. Detailed sintering and crystal growth procedure is presented in this study. The required phase of the grown crystals is confirmed by powder X-ray diffraction (XRD) analysis. Ultraviolet (UV) photoluminescence and X-ray induced luminescence of the grown crystals at room temperature are measured. Various scintillation properties such as energy resolution, light yield, $\alpha /\beta $ ratio and fluorescence decay time under the excitation by ^{137}\mathrm {Cs}~\gamma -ray and 241Am particles are also presented. [ABSTRACT FROM PUBLISHER]

The 3 inch size Mg co-doped Ce:Gd3 Al2Ga3 O12 single crystals were prepared by the Czochralski (Cz) 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 Mg co-doping. The timing resolution measurement for a pair of 3 \times 3 \times 3\;\mm^3 size GAGG:Ce.Mg scintillator crystals was performed using Si-PMs. [ABSTRACT FROM AUTHOR]

The crystals of 0.02%, 0.05%, 0.1%, and 0.5% Sn doped LiI are grown by the vertical Bridgman technique. The luminescence and scintillation properties of the grown crystals are investigated. X-ray excited emission spectrum of LiI (Sn) showed a broad emission band between 400–650 nm wavelength range at room temperature. Such emission is attributed to \ Sn^2 + ion. Scintillation properties such as energy resolution, decay time profiles, and light yield are measured under 662 keV (^137\ Cs) $\gamma $-ray excitation at room temperature. A maximum light yield of 6000 \pm 600 \ \ph/MeV is measured at room temperature. LiI (Sn) single crystals showed two exponential decay components under $\gamma $-ray excitation. The dependence of scintillation properties on the temperature is also presented. Changes in the decay time and light yield are measured from 295 K down to 10 K. The light yield of LiI (Sn) at 50 K is found to be nine times higher than that at room temperature. [ABSTRACT FROM AUTHOR]

New single crystals of Ce-doped (1% and 10%) \ Tl_2\ LiYCl_6 (TLYC) were investigated under X-ray and $\gamma $-ray excitation. This material belongs to Chloro-elpasolite crystal family and was grown by the two-zone vertical Bridgman technique. X-ray-induced luminescence shows typical \ Ce^3 + - \ ion emission between 350 and 530 nm peaking at 430 nm. Under 662 keV \gamma $-rays excitation, best energy resolution of 4.8% (FWHM) was found for 1% Ce-concentration. For the same Ce-concentration, a maximum light yield of \sim $30 500 \pm $ 3500 ph/MeV was observed at room temperature. Under \gamma , respectively. Due to highly hygroscopic nature of this compound, extra attention was devoted during handling and data taking processes. Overall, the scintillation properties confirm that this material is a promising candidate for medical imaging and radiation detection. [ABSTRACT FROM AUTHOR]

Cerium-doped lutetium oxyorthosilicate (Lu2SiO5: 0.5 mol%Ce, LSO:Ce) scintillation ceramics was fabricated by pre-sintering at 1650^\circ C for 4 h in air followed by a post hot isostatic pressing (HIP) at 1600^\circ C under 150 MPa for 1 h in Ar atmosphere. Luminescent and scintillation properties of the as-HIPed LSO:Ce ceramics was seriously affected by these oxygen vacancies. They were effectively filled through a post-annealing at 1300^\circ C for 4 h in air. Ce LIII edge X-ray absorption near edge structure (XANES) spectra of LSO:Ce ceramics manifest that most of Ce ions in LSO ceramics still remain Ce(III) valence state after annealing in air. Photoluminescence (PL) and PL excitation (PLE) spectra show that emission intensity of the as-HIPed LSO:Ce ceramics was about 3 times lower than that of post-annealed sample. Light yield of the post-annealed LSO:Ce ceramics reaches 2.7 times of that of the as-HIPed sample, which exceeds 3 times of the light yield of BGO crystal. [ABSTRACT FROM AUTHOR]

A picosecond-range timing of charged particles and photons is a long-standing challenge for many high-energy physics, biophysics, medical and security applications. We present a design, technological pathway and challenges, and some properties important for realization of an ultrafast high-efficient room-temperature semiconductor scintillator based on self-assembled InAs quantum dots (QD) embedded in a GaAs matrix. Low QD density (< 10^15~\cm^-3), fast (\sim 5~\ps) electron capture, luminescence peak redshifted by 0.2-0.3 eV from GaAs absorption edge with fast decay time (0.5-1 ns) along with the efficient energy transfer in the GaAs matrix (4.2 eV/pair) allows for fabrication of a semiconductor scintillator with the unsurpassed performance parameters. The major technological challenge is fabrication of a large volume ( > 1~\cm^3) of epitaxial QD medium. This requires multiple film separation and bonding, likely using separate epitaxial films as waveguides for improved light coupling. Compared to traditional inorganic scintillators, the semiconductor-QD based scintillators could have about 5x higher light yield and 20x faster decay time, opening a way to gamma detectors with the energy resolution better than 1% and sustaining counting rates > 100~\MHz. Picosecond-scale timing requires segmented low-capacitance photodiodes integrated with the scintillator. For photons, the proposed detector inherently provides the depth-of-interaction information. [ABSTRACT FROM AUTHOR]

This paper reports on the preparation and growth of Eu-doped strontium iodide (SrI2) single crystals by modified micro-pulling-down method. Influence of the Eu^2 + and Eu^3 + (introduced in form of EuI2 and EuCl3) on the luminescence and scintillation properties is analyzed. Sufficient optical quality of prepared single crystals was obtained allowing further characterization of their absorption, radio- and photoluminescence spectra. Photoluminescence and scintillation decay time of grown SrI2 crystals irradiated under \gamma -ray source were evaluated as well. [ABSTRACT FROM AUTHOR]

The paper is dedicated to development of the novel scintillating screens based on single crystalline films (SCF) of Ce doped Lu3 - x{Tb_x}{Al5 - y}{Ga_y}{O12} multicomponent garnets at x = 2 - 3 and y = 0 - 2.5 onto Y_3Al_5O12 (YAG) and Gd_3Al2.5{Ga2.5}{O12} (GAGG) substrates using the liquid phase epitaxy (LPE) method. We report the optimized content and high scintillation figure of merit of SCF of these garnets grown by the LPE method with using PbO based flux. Namely, the Tb_3Al2.5{Ga2.5}{O12}:Ce SCFs possess the highest values of light yield (LY) compared to all earlier investigated SCF samples, with their LY exceeding by 2.35 and 1.15 times the LY values for YAG:Ce and LuAG:Ce SCF scintillators, respectively. The SCFs of the mentioned compounds show very lower thermoluminescence in the above room temperature range and relatively fast scintillation decay. [ABSTRACT FROM AUTHOR]

Ga- and In-doped ZnO nanorods were prepared by low temperature hydrothermal method, and their structure, morphology and luminescence properties were investigated through X-ray diffraction, scanning electron microscopy, photoluminescence and X-ray excited fluorescence spectrometers. The results indicated that the nanorods had a hexagonal wurtzite structure, and the average diameter and length of the nanorod were about 1~\mu\m and 10~\mu\m, respectively. Ultraviolet and X-ray excited luminescence spectra of the nanorods show a relatively strong visible emission peak located around 450-750 nm. The In-doped ZnO nanorods exhibited a superior X-ray excited luminescence performance, which implies that it is expected to be a promising candidate for applications in high-spatial-resolution and fast X-ray imaging detector. [ABSTRACT FROM AUTHOR]

This paper is the fifth in a series of articles on the basic physics of light yield nonproportionality in scintillators. Here, we compare and contrast the nonproportionality as registered by gamma rays and high-energy electrons. As has been noted in the past, these two types of data have different curve shapes (for plots of the light yield against electron or gamma energy). Herein, we show how the experimental gamma nonproportionality curve can be calculated from the electron response by accounting for the distribution of high energy electrons created by the gamma photon via the photoelectric interaction. Similarly, we measure and model the gamma-induced resolution as a function of energy and compare this data to predictions from our model. The utility of the model is explored using data acquired with the scintillators SrI2(Eu), GYGAG(Ce) and CsI(Na). [ABSTRACT FROM PUBLISHER]

This paper is the third in a series of articles on the basic physics of nonproportionality in scintillators. Here, we focus on the temperature dependence of six scintillators, NaI(Tl), CsI(Tl), CsI(Na), CeBr_3, LaBr_3(Ce), and undoped SrI_2, and report their nonproportionality curves at -40^\circC, 0^\circC and + 40^\circC. We fit the data to a modified form of our previously employed model, including the competition of carrier trapping with the Onsager-mediated attraction between electrons and holes. [ABSTRACT FROM PUBLISHER]

Experimental studies of LaBr3 doped with 5%, 10%, 20% and 30% Ce^3+ and CeBr3 are performed for application in TOF-PET. X-ray excited emission spectra, decay time constants, photoelectron yields and energy resolutions are measured from 100 K to 600 K. The results show a strong temperature and Ce^3+ concentration dependence, which is mostly explained by Ce^3+ self-absorption. We modeled how self-absorption affects the scintillation pulse shape and what the consequences are for the detector timing resolution. It shows that self-absorption elongates the decay time constant, whilst it does not affect the scintillation rise time. [ABSTRACT FROM PUBLISHER]

1-inch size Ce1%:Gd_2Lu_1Al_2Ga_3O12, Gd_1Lu_2Al_2Ga_3O12, Gd_1Y_2Al1.5Ga3.5O12 and Lu_2Y_1Al_2Ga_3O12 were grown by the Czhocralski (Cz) method. The EPMA techniques is employed to check their chemical composition. Luminescence and scintillation properties were also evaluated. The Ce1%:Gd_1Y_2Al_2Ga_3O12 sample showed the highest light yield of around 40\thinspace000 photon/MeV. The scintillation decay time was 46.6 ns(63%) and 157 ns(37%). [ABSTRACT FROM PUBLISHER]

Results of absolute light yield measurements on strontium and barium fluoride doped with PrF_3 and CeF_3 are presented and compared with light yield of well-known scintillators s(NaI-Tl and CsI-Tl). For pure SrF_2 crystal, we obtain the value of about 29,200 photons/MeV. [ABSTRACT FROM PUBLISHER]

Non-stoichiometric YAG powder samples were prepared via a simple sol-gel combustion method by introducing antisite defects YAl,16a intentionally. The investigation of structure and luminescence properties confirmed that the antisite defects with different concentrations can be created through adjusting the composition in YAG at relatively low (1000^\circC) temperature. The X-ray excited luminescence and vacuum ultra-violet spectroscopies show that the luminescence intensity of non-stoichiometric YAG increases with increasing antisite defects concentration, which is much stronger than that of the stoichiometric counterpart under the same conditions. It indicates that non-stoichiometric YAG with antisite defects YAl,16a might be used as a potential candidate for scintillator. [ABSTRACT FROM PUBLISHER]

New single crystals of Ce-doped Cs2NaGdCl6 are investigated under x-ray and \gamma-ray excitation. These scintillation crystals are grown by two zone vertical Bridgman technique and belong to elpasolite crystal family. Energy resolution, scintillation light yield, non-proportionality, energy resolution as a function of \gamma-rays energies and scintillation decay time measurements are presented. Ce^3+-related x-ray excited emission is observed between 360 and 450 nm wavelength region at room temperature. At higher Ce-concentration both self-trapped exciton (STE) and Gd^3+ emissions are disappeared and enhance Ce^3+ emission. Under 662 keV \gamma-rays excitation, Cs2NaGdCl6 shows an energy resolution of 5.2%, (FWHM) at 1% Ce-concentration. Best energy resolution of 4.8% (FWHM) is obtained for 10% Ce-concentration. No significant improvement is observed in the energy resolution of Cs2NaGdCl6 with the increase of Ce-concentration. The highest light yield of about 21,000 ph/MeV is obtained for 10% Ce-doped crystal. At room temperature three decay time components are found under \gamma-ray excitation for all Ce-doped samples. This material is highly hygroscopic. [ABSTRACT FROM PUBLISHER]

Absorption, excitation and emission spectra of cadmium fluoride crystals doped with rare-earth ions were investigated. In contrast to alkaline-earth fluorides the absorption spectra due to 4f - 5d transitions of Ce^3+, Pr^3+ and Tb^3+ ions are broadened. No 5d-4f emissions were observed. These prove that 5d(eg) levels of rare earth ions lie in conduction band of CdF2 crystal. Emission spectra of Tb^3+ show the group of 4f-4f ^5D4-^{7}F_j lines in contrast to other alkaline-earth fluorides where emission due to ^5D3-^{7}F_j transitions is also observed. The absence of the emission is due to position of ^5D3 level within condution band. Among the all measured crystals doped with impurity ions (Pr, Nd, Eu, Ho, Tb, Tm, Yb, Ga, In or Mn), the CdF2 doped with Pr^3+, Tb^3+, or Mn^2+ ions have the highest light outputs under x-ray excitation. [ABSTRACT FROM PUBLISHER]

Functional possibilities of Pr:LuAG single crystal covered with plastic scintillators are demonstrated. Shift of luminescence wavelength of the hybrid scintillators towards the region of higher spectral sensitivity of photodetectors and radiation responses of the hybrid scintillators were investigated. The Pr:LuAG sample coated with bis-MSBPVD showed the better light output and energy resolution than the Pr:LuAG itself. Light output was increased up to 55% and energy resolution was also improved to 6.5%@662 keV using APD (Hamamatsu S8664-8220). In the case of MPPC (Hamamatsu S10362_33_050 3600 pixel-type), light output was increased up to 35% and energy resolution was also improved to 9.8%@662 keV. Decay curve of the Pr:LuAG sample coupled with the WLS was also measured and successfully modeled. [ABSTRACT FROM PUBLISHER]

Radiative relaxation channels and energy losses in In and Tl doped CsI scintillation crystals have been investigated as a function of temperature and excitation conditions to evaluate scintillation efficiency of the activator channel. Two activator concentration series of crystals were grown by the Bridgman method. Temperature dependence of excitation and luminescence spectra were measured under VUV and X-ray excitation; thermostimulated luminescence was also studied. The observed drop of radioluminescence yield of doped CsI crystals at room temperature relative to the pure crystal is explained by the migration losses caused by charge carrier trapping on the activator centers. The energy losses in CsI:A at low temperatures are due to the trapping of charge carriers on different centers: self-trapping of holes and capture of electrons by the activator centers. We suppose that migration energy losses are the main reason for significantly lower luminescence yield of CsI:A at room temperature than that of self-trapped excitons in pure CsI crystal [ABSTRACT FROM PUBLISHER]

In this work, the scintillation properties of Cs3LaCl6 and Cs3LaBr6 single crystals doped with various Ce concentrations (0.5 at.%–40 at.%) were studied. In the decay time profiles, both the fast (\sim 50 ns) and slow (\sim 500 ns) components decrease with increasing Ce concentration. The fast decay component dominates with high Ce concentration. Cs3LaCl6:Ce has a light yield of \sim 20\ 000 photons/MeV for 20 at.% Ce, while Cs3LaBr6:Ce has a light yield of 35 000 photons/MeV for 10% Ce. Energy resolution was improved from 20 at.% to 8 at.% with higher Ce concentration. Cs3LaCl6:Ce and Cs3LaBr6:Ce are 30 and 8 times less hygroscopic than LaBr3:Ce. [ABSTRACT FROM PUBLISHER]

Photoluminescence, X-ray excited radioluminescence and photoelectron yield characteristics were studied in multicomponent GdGaYAG:Ce and GdGaLuAG:Ce garnet films grown by liquid phase epitaxy. Nonradiative energy transfer from \Gd^3+ to activator \Ce^3+ ions was evidenced. At low Gd doping, < \5\%, two virtually independent emission centers coexist, which compete for intensity: \Ce^3+ with fast 5d-4f emission and \Gd^3+ with slow 4f-4f emission. At higher Gd concentrations, the \Ce^3+ emission retrieves intensity due to the energy transferred from \Gd^3+ donors. At Gd concentration \sim \50\% and above, the \Gd^3+ emission is suppressed due to energy migration and transfer to \Ce^3+ centers. In these samples, the host emission is also completely quenched and the best scintillator performance is achieved. Contrary to melt-grown crystals, no positive role of Ga substitution was found in epitaxial films. [ABSTRACT FROM PUBLISHER]

The paper is dedicated to development of the novel scintillating screens based on single crystalline films of Ce doped multi-component (Gd,Y,Lu)3(Al,Sc)5O12 garnets onto Gd3Ga5O12 substrates using the liquid phase epitaxy method. [ABSTRACT FROM PUBLISHER]

The time resolution of a scintillator-based detector is directly driven by the density of photoelectrons generated in the photodetector at the detection threshold. At the scintillator level it is related to the intrinsic light yield, the pulse shape (rise time and decay time) and the light transport from the gamma-ray conversion point to the photodetector. When aiming at 10 ps time resolution, fluctuations in the thermalization and relaxation time of hot electrons and holes generated by the interaction of ionization radiation with the crystal become important. These processes last for up to a few tens of ps and are followed by a complex trapping-detrapping process, Poole-Frenkel effect, Auger ionization of traps and electron-hole recombination, which can last for a few ns with very large fluctuations. This paper will review the different processes at work and evaluate if some of the transient phenomena taking place during the fast thermalization phase can be exploited to extract a time tag with a precision in the few ps range. A very interesting part of the sequence is when the hot electrons and holes pass below the limit of the ionization threshold. The only way to relax their energy is then through collisions with the lattice resulting in the production of optical and acoustic phonons with relatively high energy (up to several tens of meV) near the ionization threshold. As the rate of such electron/phonon exchange is about 100 events/ps/electron or hole and as the number of electrons/holes generated after mutiplication in a high light yield scintillator like LSO can be as high as 100,000 or more, we end up with an energy deposition rate of about 100 KeV/ps. This energy deposition rate contributes to many fast processes with a characteristic time in the ps range such as band-to-band luminescence, hot intraband luminescence, acoustic shock wave generation, fast local variation of index of refraction, etc. We will discuss if the part of the total energy which is released this way, and which can represent between 50% and 90% of the energy of the incoming ionization radiation, can be efficiently exploited to improve the time resolution of scintillators, presently limited to the 100 ps range. [ABSTRACT FROM PUBLISHER]

We report an investigation on pure and doped PbFCl crystals. Optical and scintillation properties, such as emission and transmittance spectra, light output and decay kinetics, were measured at different temperatures. Three emission bands at 2.27, 2.85 and 3.39 eV are observed at 77 K. Thermal quenching effect is also observed. While a scintillation component peaked at 400 nm with 3 ns decay time is observed in all PbFCl samples, a secondary emission at 550 nm with 360 ns decay time is found in the K doped PbFCl samples. The origins of three emission bands and further development of PbFCl for the HHCAL detector concept are discussed. [ABSTRACT FROM PUBLISHER]

Single Crystal Film (SCF) scintillators are key-components of today's high-resolution 2D X-ray detectors used at synchrotrons for applications such as X-ray Radiography, Computed Tomography (CT), laminography, full-field XANES, and topography. Due to its high density and effective atomic number, LuAlO3 (LuAP) perovskite has a great potential to replace or complement the currently used Eu-doped Gd3Ga5O12 (GGG:Eu) and Tb-doped Lu2SiO5 (LSO:Tb) SCFs. In this article we present the growth of LuAP single crystalline films on undoped YAlO3 (YAP) by the vertical dipping isothermal Liquid Phase Epitaxy (LPE) growth method. For the comparison of the light output of Ce and Tb doped LuAP SCF screens both cathodoluminescence (CL) and X-ray excited luminescence (RL) measurements were used. For investigations of Ce-Tb energy transfer in the afore mentioned oxide hosts, in addition to using traditional spectroscopic methods, we made time-resolved luminescent spectroscopy of Ce-Tb doped LuAP SCFs under excitation by pulsed synchrotron radiation at the Superlumi station (HASYLAB at DESY). Recently we have demonstrated the strong quenching influence of Pb^2+ flux related impurity on the Ce^3+ emission in the Ce-doped LuAP SCF screens. However our present investigation shows that Tb-doped LuAP SCFs are efficient X-ray scintillators, whose light output can be significantly increased by co-doping with Ce^3+ ions. Namely, we demonstrate the efficient Ce\rightarrow Tb energy transfer in LuAP:Tb,Ce SCFs. Finally, as-grown LuAP:Tb and LuAP:Tb,Ce films were evaluated for high-resolution X-ray imaging using a spatial resolution target at the European Synchrotron Radiation Facility (ESRF), and displayed promising results. [ABSTRACT FROM PUBLISHER]

We present the applications of time-resolved spectrometer for soft X-ray (SXR) excited luminescence measurements. We use the spectrometer to monitor the delayed recombination phenomena in the scintillation response of ZnO:Ga nanoparticles, SrHfO3 microcrystalline powder, and rare-earth doped LiCaAlF6 single crystals in an extended time and dynamic range. The nanosecond soft X-ray (E\approx 0.4\ keV) pulse plasma source is used for excitation of a scintillation process. High sensitivity of our experiment is enabled by an intense nanosecond SXR pulse with a very short absorption length (<1\ \mum) in scintillation materials and sensitive fast photomultiplier-based detection. Thus, we are able to measure decay profiles with signal-to-noise ratio as high as 10^5 and with nanosecond resolution over millisecond time range. Moreover, the presented technique allows studying powder materials, due to the aforementioned extremely short absorption length of SXR. [ABSTRACT FROM PUBLISHER]

We study the low temperature contribution to delayed recombination decay in several complex oxide scintillating crystals. We experimentally test the previously suggested hypothesis that the losses of fast scintillation light even at the lowest temperatures can be due to quantum effects. The results obtained for several material systems confirm that quantum tunneling between the luminescence center and a nearby defect is a good candidate for the origin of the observed phenomena. [ABSTRACT FROM PUBLISHER]

Analysis of the last years theoretical studies and track simulations to conclusion that primary stages (electron scattering and e-h thermalization) play the key role in the following scintillator efficiency. The long thermalization length comparing to Onsager radius is the main reason for geminate pair concentration decrease and later luminescence losses. The easiest way for thermalization length decrease is the scintillation crystal doping or even transfer to the mixed crystals (solid solution). The simple model of modification of electrons scattering and e-h pairs thermalization for the mixed crystals is proposed. It is shown that solid solutions have higher light output independently on the crystal type. Analysis of experimental data confirmed this conclusion. This phenomenon is found for halide, oxide and sulfates scintillators. The similar behavior is typical for mixed anion and/or cation systems. The key role of initial track formation stages is illustrated by the same trend for activated scintillators and pure crystal with intrinsic luminescence. These estimations and experimental data lead to the conclusion that the scintillation efficiency improvement by mixed crystal use can play an important role in the search and development of new scintillators. [ABSTRACT FROM PUBLISHER]

Rare-earth (RE=Sm, Pr, Tb, Tm) doped ternary sulfides having the general formula KLn 0.995RE0.005 S 2 (Ln=La, Gd, Lu) and undoped KLnS 2 were synthesized in the form of crystalline hexagonal platelets by a chemical reaction in an electric resistance furnace under the flow of hydrogen sulfide. X-ray powder diffraction confirmed only a single phase of the rhombohedral lattice system (space group R-3 m). Time-resolved luminescence spectroscopy was employed to investigate radioluminescence, photoluminescence, decay kinetics and absorption spectra. The KLnS 2 band edge at 300–330 nm was found and characteristic Pr^3+, Sm^3+, Tb^3+ and Tm^3+~ 4 f -4 f emission lines in the visible spectral range were observed. The charge transfer transitions in the Pr^3+- and Sm^3+-related excitation spectra in the range 330–370 nm are described and the eficient energy transfer from the host to the emission centers is revealed. We discuss the potential for application of these materials in white LED solid-state lighting and X-ray phosphors. [ABSTRACT FROM PUBLISHER]

Monte Carlo simulations were used to investigate the correlation between luminosity parameters and pulse shape discrimination (PSD) and subsequently compared with experimental results from CsI:Tl. Luminosity intensity parameters Af, As (fast and slow initial luminosities) and temporal luminosity parameters \tauf, \taus (fast and slow decay time constants) of a dual decay mode scintillator were applied to create a dynamic model with Crystal Ball simulation system. The simulated pulses were analyzed with charge comparison (CC) and constant time discrimination (CTD) PSD methods followed by quantification of the histogrammed pulse data with Figure of Merit (FoM) and spillover (pulse misclassification). Performance in terms of FoM and spillover is compared with that of fixed reference pulses set at (Af \tauf/As \taus)\gamma = 1 and (Af \tauf/As \taus)\gamma = 0.1. For the CC method, independent of the reference pulse characteristics [(Af \tauf/As \taus)\gamma = 1\ {\or} = 0.1], \taus is the most influential parameter for PSD as compared with Af, As, and \tauf. For the CTD method, Af and As are seen to have less influence over the PSD compared to \tauf and \taus when (Af \tauf/As \taus)\gamma = 1 and \tauf is the most influential parameter for both reference pulses. Using both methods with either reference pulse applied, the scintillator having luminosity parameters such that 0.1 < (Af \tauf/As \taus)\alpha/\gamma < 2 is classified as having poor PSD. Excellent correlation is observed between the simulation and the experimental results with CsI:Tl, which is known for very good \alpha/\beta (\gamma) pulse shape discrimination. This study is useful for describing how the luminosity parameters affects PSD. [ABSTRACT FROM PUBLISHER]

In this study we report for the first time that \ Yb^2+ is an efficient and fast activator in iodide scintillator crystals. In both SrI 2 and CsBa 2 I 5, \ Yb^2+ offers blue luminescence (\lambda max = 414~\ nm), light yield greater than 50,000 Photons/MeV and sub-microsecond decay time. Results on crystal growth and characterization will be presented. [ABSTRACT FROM PUBLISHER]

We demonstrate a new scintillator material that has a one-dimensional eutectic structure and optical light-guiding properties. Our light propagation calculations predicted that a structure where high refractive index luminescence cylinders are embedded in a matrix should show effective light-guiding properties. An inverse structure where a high refractive index luminescence matrix contains low refractive index cylinders was also predicted to possess light-guiding properties. A CsI—NaCl:Tl eutectic phase, which contained NaCl cylinders in a CsI matrix, was grown by a one-dimensional solidification method. This material showed high spatial resolution because of the difference in the refractive indices of NaCl and CsI. [ABSTRACT FROM PUBLISHER]