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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]

La 0.2 Y 1.8 O 3 is a new and promising scintillator which is based on the host material without doping. Here the time gated X-ray excited optical luminescence is measured by using the excitation energy below, above and at the La L 3 -edge. A relatively slow and broad emission with peak at 415 nm has been observed as the dominant emission. Also, a weak emission at 360 nm is observed at the fast window, associated with the recombination of trapped excitons in Y 2 O 3 host. The observations show that the broad emission at 415 nm is most likely due to the recombination of trapped excitons associated with the La 3+ doping into Y 2 O 3 sites. [ABSTRACT FROM AUTHOR]

The moisture sensitivity of LuI 3 :Ce,Hf and luminescent properties of undoped LuI 3 and LuI 3 :M (M=Ce 3+ , Tb 3+ , Dy 3+ ) powders were investigated. The possibility of improving the air and moisture stability of LuI 3 :Ce by Hf doping was tested. It was proven that the Hf contribution to the LuI 3 :Ce stability is very limited and is insignificant to render LuI 3 :Ce scintillator powders suitable for applications. Photoluminescence results of LuI 3 without dopants added on purpose showed luminescence due to a plurality of rare-earth elements׳ impurities. Two types of self-trapped luminescence were found. Energy transfer between host lattice, self-trapped excitons and rare-earth ions was investigated. [ABSTRACT FROM AUTHOR]

Real-time, in-situ ionoluminescence measurements provide information of evolution of emission bands with ion fluence, and thereby establish a correlation between point defect kinetics and phase stability. Using fast light ions (2 MeV H and 3.5 He MeV) and medium mass-high energy ions (8 MeV O, E =0.5 MeV/amu), scintillation materials of a-SiO 2 , crystalline quartz, and Al 2 O 3 are comparatively investigated at room temperature with the aim of obtaining a further insight on the structural defects induced by ion irradiation and understand the role of electronic energy loss on the damage processes. For more energetic heavy ions, the electronic energy deposition pattern offers higher rates of excitation deeper into the material and allows to evaluate the competing mechanisms between the radiative and non-radiative de-excitation processes. Irradiations with 8 MeV O ions have been selected corresponding to the electronic stopping regime, where the electronic stopping power is dominant, and above the critical amorphization threshold for quartz. The usefulness of IBIL and its specific capabilities as a sensitive tool to investigate the material characterization and evaluation of radiation effects are demonstrated. [ABSTRACT FROM AUTHOR]

Ce-doped lutetium aluminum garnet Lu 3 Al 5 O 12 (LuAG) nanoceramics were fabricated at 1600 °C and 1700 °C by spark-plasma sintering (SPS) method from nano-powders prepared by radiation synthesis. Both undoped and Ce-doped LuAG ceramic samples were also prepared from the nano-powders at 1700 °C with significantly increased pre-heating rate. The backscattered electron images revealed large amount of pores in all the Ce-doped samples causing their significant opacity. On the other hand, very large grains and no pores were revealed in the undoped sample, which was the only transparent one. The radioluminescence measurements revealed superior overall scintillation efficiency of the samples sintered at the temperature 1700 °C, and their defect emission in the UV region was ascribed to oxygen-vacancy-related defects such as F + centers. The photoluminescence decay of the defect emission was characterized by an extremely fast decay time of a few nanoseconds. Influence of sintering procedure and subsequent annealing on the luminescence and scintillation properties is discussed. [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]

Large lithium molybdate (Li 2 MoO 4 ) crystal boules were produced by using the low thermal gradient Czochralski growth technique from deeply purified molybdenum. A small sample from one of the boules was preliminary characterized in terms of X-ray-induced and thermally-excited luminescence. A large cylindrical crystalline element (with a size of ⊘40 × 40 mm) was used to fabricate a scintillating bolometer, which was operated aboveground at ∼15 mK by using a pulse-tube cryostat housing a high-power dilution refrigerator. The excellent detector performance in terms of energy resolution and α background suppression along with preliminary positive indications on the radiopurity of this material show the potentiality of Li 2 MoO 4 scintillating bolometers for low-counting experiment to search for neutrinoless double beta decay of 100 Mo. [ABSTRACT FROM AUTHOR]

A method has been standardized for restoring a shifted differential pulse height spectrum from a scintillator based gamma ray spectrometer recorded at measurement temperature, to the position of a desired spectrum, recorded at a reference temperature. The method is based on the assumption that the spectrum obtained at measurement temperature represents the same statistical distribution as that at reference temperature but with different energy scales. A computer program has been developed for calculation of the transformation between the energy scales and for the restoration of the shifted spectrum. The method developed has been successfully applied for the restoration of gamma spectra measured at different temperatures. [ABSTRACT FROM AUTHOR]

Non-stoichiometric Lu 3+ x Al 5 O 12 :Ce (Lu 3+ x AG:Ce, x =1, 2, 3 and 4 %) ceramics were fabricated by solid state reaction method and further optimized by an air-annealing process. Absorption, luminescence spectra and scintillation characteristics such as light yield, scintillation decay times, energy resolution, proportionality and afterglow were measured and compared with those of the latest LuAG:Ce single crystal and stoichiometric LuAG:Ce,Mg ceramic samples. Thanks to the elimination of oxygen vacancies produced in the vacuum sintering process, air-annealing treatment led to a significant decrease of afterglow and a remarkable enhancement of radioluminescence intensity and light yield. The highest light yield was found in annealed 1% Lu 3+ rich Lu 3+1% AG:Ce ceramic, reaching 14,760 ph/MeV (1 μs shaping time) and 22,400 ph/MeV (10 μs shaping time). Scintillation decays of Lu 3+ x AG:Ce ceramics consist of both fast (decay time 65–73 ns) and slow (decay time 740–1116 ns) decay components where the relative intensity of the latter is higher (~58%). A decreasing trend in scintillation efficiency was observed with increasing excess of Lu (with higher x values) in the samples. This can be explained by the existence of various electron traps due to Lu Al antisite defect and structure disorder at the gain boundaries and interfaces. [ABSTRACT FROM AUTHOR]

The optical and scintillation properties of Ce 3+ -doped YGd 2 Al 5− x Ga x O 12 ( x =2,3,4) single crystals were investigated. With increasing Ga content in the garnet host, the 5d 1 absorption and emission bands shift toward higher energy due to the decrease in the crystal field splitting of the 5d levels. Temperature dependences of absorption and emission spectra and of photoluminescence decays of both prompt and delayed components were measured. Light yield (LY) and its dependence on an amplifier shaping time were measured under excitation with γ-rays. High LY value of 38,000 photons/MeV was obtained for a YGd 2 Al 2 Ga 3 O 12 :Ce sample. Scintillation decay was measured with an extended dynamical and temporal scale under the nanosecond-pulsed soft X-ray excitation. The relative content of the fastest component in the scintillation response increases with increasing Ga content. [ABSTRACT FROM AUTHOR]

Evolution of the non-radiative and radiative recombination in GaN and CdS 2.5–20 μm thick layers has been examined by the in situ measurements of the 1.6 MeV proton induced luminescence and laser excited photoconductivity characteristics. The introduction rate of radiation defects has been evaluated by the comparative analysis of the laser and proton beam induced luminescence for the examined GaN and CdS layers. [ABSTRACT FROM AUTHOR]

The introduction of a small quantity of tungsten oxide (in the range 0.2–0.5 wt%) into the melt improves the growth of ZnMoO 4 crystals. No significant difference in the kinetics of scintillation decay, scintillation efficiency, emission spectra, optical transmittance was observed for three ZnMoO 4 crystal samples grown from the melt of stoichiometric composition, with excess of molybdenum and doped with tungsten. Using CaWO 4 as reference, the absolute light yield of ZnMoO 4 is found to be equal to 3550 ± 550 ph/MeV at 77 K. For two ZnMoO 4 samples 20 mm in diameter and 40 mm in length (grown from the melt of stoichiometric composition and doped with tungsten) it is confirmed that scintillation and bolometric response are similar at milli-Kelvin temperature. [ABSTRACT FROM AUTHOR]

Multicomponent garnets (Y 3− x Gd x Al 5− y Ga y O 12 ) doped with Ce 3+ ions are promising scintillators with a high density, fast response time and high light yield. To deepen the knowledge about the transfer stage of scintillation mechanism we discuss the energy migration and energy transfer processes in the set of undoped and Ce 3+ activated multicomponent garnet single crystals. Temperature dependence of Gd 3+ emission intensities as well as decay kinetics in Y 3− x Gd x Al 5− y Ga y O 12 ( x , y =1,2,3) crystals point to the Gd 3+ →Gd 3+ nonradiative energy migration, which is diffusion limited. Concentration quenching of Gd 3+ emission occurs by energy migration to accidental impurities and/or structure defects. Temperature dependence of photoluminescence emission intensities and decay time measurements of Gd 3+ as well as Ce 3+ ions in Gd 3 Ga 3 Al 2 O 12 :Ce 3+ single crystal reveal nonradiative energy transfer Gd 3+ →Ce 3+ (including migration through Gd 3+ sublattice) which is responsible for slow Ce 3+ fluorescence decay component. [ABSTRACT FROM AUTHOR]

The luminescence and optical properties of promising cryogenic scintillator Li 2 MoO 4 were studied in the temperature region of 2–300 K. The data on luminescence spectra and decay characteristics, excitation spectra, thermostimulated luminescence curves and spectra as well as transmission and reflectivity spectra are presented for the single crystals grown by two different procedures, the conventional Czochralski method and the low-temperature gradient Czochralski technique. The bandgap of Li 2 MoO 4 is estimated from the analysis of transmission, luminescence excitation and reflectivity spectra. Up to three luminescence bands with the maxima at 1.98, 2.08 and 2.25 eV are detected in the emission spectra of crystals and their origin is discussed. In the thermoluminescence curves of both studied crystals, two high-intensity peaks were observed at 22 and 42 K, which are ascribed to the thermal release of self-trapped charge carriers. The coexistence of self-trapped electrons and holes allows one to explain the poor scintillation light yield of Li 2 MoO 4 at low temperatures. [ABSTRACT FROM AUTHOR]

High silica glasses containing SnO were prepared by sintering solution-doped porous silica glasses. The sample sintered in the CO reducing atmosphere exhibited a strong emission at 400 nm under 269 nm excitation with a lifetime of 11 μs, and its intensity was much stronger compared to that of the sample sintered in the air atmosphere. Under X-ray excitation, broad radioluminescence ranging from 300 to 600 nm was observed and the maximum integral intensity was 122% of Bi 4 Ge 3 O 12 (BGO). [ABSTRACT FROM AUTHOR]

This work investigates the physical, optical, luminescence, and scintillation properties of borosilicate glasses doped with different concentrations of Gd 2 O 3 and Dy 2 O 3. All glasses were prepared by the melt quenching technique. The density and molar volume value increase as the Gd 2 O 3 and Dy 2 O 3 content increases. Dy3+ in glasses absorb photons in visible light and near-infrared regions, confirmed by the absorption spectra. The emission spectra of glasses show two strong peaks at 575 nm (4F 9/2 →6H 13/2) and 481 nm (4F 9/2 →6H 15/2) under Gd3+, direct Dy3+ and X-ray excitation. The integral scintillation efficiency of 1.50Dy:12.5Gd is 7.22%, compared with BGO crystal. The luminescence of glass can be tuned for different shades of white emission by selecting the excitation source such as photon with 275 nm, 387 nm and X-ray, respectively. The developed glasses are the potential for tunable emitting and scintillation material applications. [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]

• K 2 LaBr 5 :Eu2+ single crystal was obtained successfully by vertical Bridgman method without flux for the first time. • The luminescence phenomenon of K 2 LaBr 5 :Eu2+ was studied. • The optical transmission of K 2 LaBr 5 :Eu2+ single crystal was presented and the bandgap was estimated according to Tauc and Menth's law. • For the first time, the decay time of the heterovalently doped K 2 LaBr 5 :Eu2+ single crystal under gamma rays is nanoseconds. Recent researches have shown that Eu2+ ion heterovalently doped rare earth halide scintillators attract the attention of researchers. In this paper, the transparent K 2 LaBr 5 scintillation crystals of centimeter size doped with heterovalent Eu2+ were successfully grow by the vertical Bridgman technique. X-ray powder diffraction analysis shows that the crystal has an orthonormal structure with space group Pnma(62). A small amount of Eu2+ doping does not change the internal structure of the crystal. The transmittance, the UV–visible excited spectrum and emission spectrum, X-ray excited luminescence spectrum, Photoluminescence decay time and scintillation pulse decay time have been measured at room temperature. The results show that the crystal has strong luminescence intensity, and the maximum emission peak is about 430 nm. The photoluminescence decay time of K 2 LaBr 5 :xmol.%Eu2+(x = 0.5, 1, 2) are 5.56 μs, 5.67 μs and 7.03 μs, respectively. The decay time of K 2 LaBr 5 :Eu2+ crystal under 137Cs 662 keV radiation is nanosecond, indicating that the K 2 LaBr 5 :Eu2+ crystal has fast decay characteristics and excellent time resolution performance. [ABSTRACT FROM AUTHOR]

Mg2+-codoped Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce (YGAGG:Ce,Mg) single crystal was grown by the Czochralski method and its luminescence and scintillation properties were investigated. Temperature dependence of radioluminescence (RL) yield and photoluminescence (PL) decay time was measured, and activation energy of thermal ionization process was determined from temperature-dependent PL decay time measurement. YGAGG:Ce,Mg exhibited high X-ray excited RL yield almost 5 times higher than BGO reference scintillator. Its light yield of 41,500 ph/MeV and scintillation decay times of 12 ns (2%) + 52 ns (65%) + 207 ns (33%) were measured under excitation with 662 keV γ rays from 137Cs source. Afterglow and thermally stimulated luminescence characteristics are also investigated. • Luminescence and scintillation properties of Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce,Mg crystal are investigated. • Temperature dependence of photo-and radioluminescence are presented. • Y 0.6 Gd 2.4 Al 2 Ga 3 O 12 :Ce,Mg shows high light yield of 41,500 photons/MeV. • Luminescence quenching above RT can be caused by thermal ionization. • Afterglow and thermoluminescence characteristics are investigated. [ABSTRACT FROM AUTHOR]

In this work, an anion-alloying strategy using chloride substitution is used to improve the gamma response performance of cutting-edge Cs 2 LiLaBr 6 :Ce single crystal scintillators. Single crystals of Cs 2 LiLa(Br , Cl) 6 :Ce (CLLBC:Ce) with a size of Ф12 mm × 50 mm were successfully grown by the Bridgman method. The effects of chloride substitution amount on crystal structure, band structure, luminescence properties and the scintillation properties were systematically investigated. The light yield and energy resolution of CLLB:Ce were enhanced as the increase of Cl− content. The highest light yield and optimal energy resolution were achieved on the Cs 2 LiLaBr 4 Cl 2 :Ce, about 86% of the commercial LaBr 3 :Ce single crystal and 4.1% at 662 keV. On a basis of the results of first-principle calculation and pure optical method, the band structures of Cs 2 LiLa(Br,Cl):Ce were constructed, indicating a tendency of band-gap to increase as the Cl− content increases. The origin of light yield improvement was also proposed. • The strategy of chloride substitution is used to improve the performance of Cs 2 LiLaBr 6 :Ce single crystal scintillators. • The results of first-principle calculation and pure optical method indicate that the band-gap becomes bigger as the Cl− content increases. • Cs 2 LiLaBr 4 Cl 2 :Ce shows the highest light yield and optimal energy resolution, about 86% of the commercial LaBr 3 :Ce single crystal and 4.1% at 662 keV. • The origin of light yield improvement was also proposed. [ABSTRACT FROM AUTHOR]

In scintillation crystals, at X-ray or gamma quanta registration, a noticeable time delay of the pulse is observed. This is due to the thermal delocalization of charge carriers from traps. The study of phosphorescence and relaxation of the conduction current can give information on these processes. However, their investigation requires knowing theoretical dependences of phosphorescence intensity attenuation and conduction current relaxation. A multicenter model of a crystal is proposed in which at least three types of traps (shallow, phosphorescent and deep) take part in the delocalization of charge carriers at the excitation temperature. For such a model, theoretical dependences for the phosphorescence intensity and the conduction current relaxation are obtained. These dependences take into account the processes of re-trapping of free charge carriers on more shallow traps. They show that the level of filling of different traps depends not only on the total radiation dose, but also on the intensity of excitation. An explanation of an experimental fact of intersection of phosphorescence and conduction current relaxation curves at the same irradiation dose, but at different excitation intensities, contradicting classical kinetic theory of luminescence, is obtained. All experimental dependences of phosphorescence intensity and conduction current relaxation for ZnSe crystals at different temperatures are well described by the obtained theoretical dependences. It is also established that the time of emptying of each type of traps is determined not only by the probability of thermal delocalization, but also by the ratio of the concentration of these traps to the total concentration of deeper traps. • The long-term phosphorescence and conduction current relaxation of specially undoped ZnSe crystals at different temperatures was studied. • Theoretical dependences for the phosphorescence intensity and the magnitude of the conduction current are obtained in analytical form. • An experimental fact that curves of phosphorescence and conduction current relaxation at the same irradiation dose intersect was explained. • It was confirmed that the traps' emptying time is determined also by the ratio of the trap concentration to the total concentration of deeper traps. [ABSTRACT FROM AUTHOR]

Gd 3+ -, Tb 3+ /Gd 3+ -coactivated oxyfluoride borogermanate scintillating glasses with the density of about 6.35–6.61 g/cm 3 were prepared by a melt-quenching method. The luminescent and energy transfer properties were studied by transmittance, photoluminescence and X-ray excited luminescence (XEL) spectra. The total content of rare-earth oxide and fluoride is as high as 49 mol% in oxyfluoride borogermanate glasses, which are necessary to ensure their density up to 6.61 g/cm 3 . Energy transfer efficiency and mechanism from Gd 3+ to Tb 3+ were determined, and the corresponding critical distances for both Gd 3+ –Tb 3+ and Tb 3+ –Tb 3+ ion pairs were calculated, respectively. The optimal concentration of Tb 3+ ions in dense oxyfluoride borogermanate glasses excited by both ultraviolet light and X-ray excitation were also determined. The integral scintillation efficiency of Tb 3+ -activated borogermanate scintillating glass was found to be about 26.9% of the standard Bi 4 Ge 3 O 12 (BGO) scintillating crystal. [ABSTRACT FROM AUTHOR]

The effects of post-fabrication thermal processing in O 2 flux on the luminescence and scintillation of a Y 2 O 3 :Tm transparent ceramic were investigated. The results showed that the strategy of post-fabrication processing can be beneficial to the performance of the ceramics, depending on the cumulative processing time. After the first hour of processing, about 40% enhancement in the luminescence output together with about 20% enhancement in the scintillation light yield were obtained. The enhancements were tentatively assigned to the incorporation of oxygen into vacancy sites. Longer cumulative processing times lead to the incorporation of oxygen as interstitials that is detrimental to scintillation light yield but not to luminescence output. This work also revealed that thermoluminescence measurements are a useful tool to predict scintillation light yield of Y 2 O 3 :Tm. [ABSTRACT FROM AUTHOR]

Silicate oxyfluoride scintillating glasses doped Tb 3 + with different concentrations were prepared by a melt-quenching method. The detailed analyses of photoluminescence spectra and luminescence decay curve testified that the Gd 3 + indeed transfers their energy to Tb 3 + via phonon assistant electric dipole–dipole interaction. The evaluated energy transfer efficiency from Gd 3 + to Tb 3 + increases gradually with increasing the Tb 2 O 3 content and reaches 99% when the content of Tb 2 O 3 exceeds 5 mol%. Due to the more efficient energy transfer from Gd 3 + to Tb 3 + and higher doping concentration of Tb 3 + , the intensity of green emission originated from 5 D 4 → 7 F J reaching the maximum when the content of Tb 2 O 3 is 6 mol%. Meanwhile, a strong 5 D 3 luminescence quenching happens due to the cross-relaxation process. Under X-ray excitation, the intensity of 542 nm emission in our glass doped with 6 mol% of Tb 2 O 3 shows 5.2 times stronger than that of 500 nm emission in the commercial Bi 4 Ge 3 O 12 (BGO) crystal, the integral scintillation efficiency is about 68% of the BGO crystal, which is much useful for reducing radiative dose to obtain high-resolution X-ray imaging. [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]

The results of formation of the high density effective scintillation ceramics consisting of two compounds of the cubic symmetry, LuAG:Ce and Lu 2 O 3 (LuAG:Ce + Lu 2 O 3 ), are described. Powders of a novel material LuAG:Ce + Lu 2 O 3 were synthesized by co-precipitation method. The introduction of Lu 2 O 3 into LuAG:Ce was shown to increase the density of the ceramics obtained and modify its scintillation properties. [ABSTRACT FROM AUTHOR]

The nature of luminescence centers in NaI:Eu scintillation crystals was studied in a wide excitation energy and temperature ranges. Radio- and photoluminescence spectra and TSL curves were measured for crystals with varied activator concentrations. Two main narrow luminescence bands at 2.8 eV (center I) and 2.6 eV (center II) were found at 10 К. Center I dominates for low Eu concentration (<0.07%). Increase of activator content leads to suppression of center I emission and enhancement of center II. Presence of oxygen containing impurities in heavily doped crystals is due to high hygroscopicity of the NaI matrix and EuI 2 dopant. Analysis of emission and thermoluminescence features allows justifying the role of anion impurities (oxygen/hydroxyl ions) in formation of activator center II, which is responsible for scintillation efficiency of NaI:Eu crystals at room temperature. [ABSTRACT FROM AUTHOR]

Growth, luminescence and scintillation characterizations of the new Tl 2 LiGdCl 6 :Ce 3+ (TLGC:Ce 3+ ) single crystals are reported. This crystal was grown by the Bridgman technique and the composition belongs to the elpasolites family. X-ray induced emission spectra of the Ce-doped samples show the emission between 360 and 440 nm and peaking at 387 nm. The emission was attributed to the Ce 3+ ions in the host lattice. The highest light yield of 58,000±6000 ph/MeV and 4.6±0.2% (FWHM) energy resolution was obtained for 10% Ce doped sample. Three decay time components were observed for the 10% Ce-concentration under γ-ray excitation at room temperature. Among the decay time constants, the fast decay time constant of 34 ns (81%) due to Ce 3+ luminescence was obtained. Further investigation to improve scintillation material is underway. [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]

Y 4 Al 2 O 9 :Pr (YAM:Pr) crystals have been grown by the micro-pulling-down method and their scintillation properties have been investigated. YAM:0.1%Pr displays a light yield of about 2000 ph/MeV and its scintillation time profile contains a prompt component with a decay time of 23.5 ns and a contribution of 20%. Radioluminescence spectra show both fast d – f and slow f – f praseodymium emissions. Low temperature glow curves are complex, consisting of discrete peaks and broad bands related to quasi-continuous trap distributions. Overall scintillation performance of YAM:Pr deteriorates with increasing praseodymium concentration. [ABSTRACT FROM AUTHOR]

We have successfully grown a SrWO 4 single crystal using the Czochralski pulling method. X-ray diffraction (XRD) showed a single phase of the grown crystal. Luminescence spectrum under X-ray excitation of a bulk SrWO 4 single crystal showed a broad emission band from 300 to 700 nm at room temperature. The decay time spectrum contained two components of 2.6 ns (5.7%) and 522 ns (94.3%) at room temperature. A change in the light yield and decay time is observed between 10 and 300 K. The luminescence yield of SrWO 4 at 125 K is found to be 8 times higher than at room temperature. The decay time gets longer by a factor of 51 as the temperature decreases down to 10 K. [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]

Lanarkite type Pb 2 MoO 5 single crystals were grown using low temperature gradient Czochralski technique and their optical and luminescent properties were studied. The luminescence band at 590–600 nm was observed under UV and X-ray excitations and ascribed to emission of self-trapped excitons. The band is thermally quenched at T > 15 K with the activation energy of process, E act = 11 meV. The measurements of thermostimulated luminescence demonstrated the presence of shallow traps, which adversely influence the energy transfer to the emission centers. [ABSTRACT FROM AUTHOR]

The work is related to the growth of scintillators based on the single crystalline films (SCF) of Ce 3+ doped Lu 3− Gd x Al 5 O 12 mixed rare-earth garnets by Liquid Phase Epitaxy (LPE) method. We have shown, that full set of Lu 3− Gd x Al 5 O 12 SCFs with x values ranging from 0 to 3.0 can be successfully crystallized by the LPE method onto Y 3 Al 5 O 12 (YAG) substrates from the melt-solutions based on PbO-B 2 O 3 flux. The absorption, X-ray excited luminescence, photoluminescence, thermoluminescence and light yield measurements, the latter under excitation by α-particles of 239 Pu and 241 Am radioisotopes, were applied for their characterization. [ABSTRACT FROM AUTHOR]

Recently, we proposed GdTaO 4 as a promising high-density scintillator but the scintillation mechanism was still unknown. In this paper, we investigated the temperature-dependent luminescent properties of GdTaO 4 crystal. The emission spectra are characterized by a broad band composed of two Gaussian components located at ~2.2 eV and ~2.7 eV of 8–300 K, which are both thermally quenched with the activation energy of 156 meV and 175 meV, respectively. These two bands are believed to be from different luminescent centers, judging from the excitation spectra, thermal activation energy and decay curves. Additionally, it was also found that the annealing atmosphere exerts little influence on the luminescence intensity. Based on the results, we tentatively assigned the high-energy band to self-trapped excitons (STE) localized in TaO 4 3 − groups and the low-energy band to relaxed excitons related to lattice imperfections. [ABSTRACT FROM AUTHOR]

Gd 3+ -doped borosilicate glasses are prepared in different melting atmosphere. Absorption spectra, decay time, luminescence spectra under UV and X-ray excitation are investigated. With melting atmosphere changing from air to CO, the luminescence intensities of Gd 3+ at 313 nm under the excitation of UV and X-ray are both enhanced. This mainly results from the reduction of Gd 3+ , which is validated by electron paramagnetic resonance (EPR). The optimal Gd 2 O 3 content for the glasses prepared under CO atmosphere is 7.5 mol%, whose integral scintillation efficiency is 20% compared with Bi 4 Ge 3 O 12 . [ABSTRACT FROM AUTHOR]

Single crystals of Ce-doped Cs 3 LaCl 6 and Cs 3 LaBr 6 show promising scintillation properties in gamma-ray detection. Their thermal response in the range from 40 K to 500 K is discussed in this work. The steady state photoluminescence spectra, photoluminescence decay time, and X-ray excited radioluminescence of Ce-doped and undoped Cs 3 LaCl 6 and Cs 3 LaBr 6 were studied. The photoluminescence and radioluminescence emission intensity of the Ce-doped crystals decreases less than 25% from 40 K to 500 K. The photoluminescence decay time of Ce 3+ increases with increasing temperature. [ABSTRACT FROM AUTHOR]

The Mg and Ca co-doped Ce:Gd 3 Al 2 Ga 3 O 12 single crystals were prepared by micro pulling down method with a wide concentration range 0–1000 ppm of the codopants. 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 and Ca co-doping. The scintillation decays were accelerated by both Mg and Ca codopants. Comparing to Ca co-doping, the Mg co-doped samples showed much faster decay and comparatively smaller light output decrease with increasing Mg dopant concentration. [ABSTRACT FROM AUTHOR]

The Nd-doped and Er-doped LuF 3 single crystals were grown by the micro-pulling-down method to study their scintillation properties in the vacuum-ultraviolet (VUV) region. The doubly Nd–Er codoped single crystal was grown to study possibility of scintillation performance improvement by energy transfer from Er 3+ to Nd 3+ ions. The LiF flux was to avoid phase transition below melting temperature. The 1%Nd-doped sample showed the highest overall scintillation efficiency under X-ray excitation which was 7 times as high as that of the LaF 3 :Nd 8% standard. The leading Nd 3+ 5d–4f emission was situated at 176 nm, while the Er 3+ 5d–4f emission for Er-doped samples was observed at 163 nm, which better matches the sensitivity of some VUV-sensitive photodetectors. The optimum Er concentration was determined to be around 1–3 mol%. No Er 3+ 5d–4f emission was observed for the doubly Er,Nd-codoped sample due to energy transfer from the Er 3+ to Nd 3+ ions. Slight improvement of the light yield was observed in the doubly-doped sample with respect to the Nd-only doped one. [ABSTRACT FROM AUTHOR]

Nd 1 mol% doped (Lu, Gd) 3 (Ga, Al) 5 O 12 (LGGAG) single crystals were grown by the micro-pulling down (μ-PD) method. Luminescence and scintillation properties such as absorption, excitation and emission spectra, light yield and decay time were evaluated. Nd1%:Lu 3 Al 5 O 12 showed the highest light output of around 8200 photons/MeV among the grown crystals. Scintillation decay time of Nd:Y 3 Al 5 O 12 was 1.32 μs (36%) 2.02 μs (64%). Nd:Lu 3 Ga 3 Al 2 O 12 was relatively high dense scintillator of 7.38 g/cm 3 with good light yield of 6800 photons/MeV and scintillation decay time of 0.20 μs (5%) 2.60 μs (95%). [ABSTRACT FROM AUTHOR]

Ce doped SrHfO 3 /SrAl 12 O 19 eutectics were grown by the micro pulling down (μ-PD) method and their directionally solidified eutectic system has been investigated. Investigations of obtained eutectic structure, luminescence and scintillation performances were also performed. Eutectics were grown at the speed of 0.60–0.90 mm/min. In the eutectics, Ce 3+ 4f–5d emission was observed at 410 nm. The eutectics showed light yield of around 300 photon/5.5 meV alpha-ray by 241 Am excitation. Scintillation decay time was 26.4 ns (45%) with slower decay component of 263 ns (55%). [ABSTRACT FROM AUTHOR]

We study the temperature dependence of delayed recombination decay intensity in a variety of scintillating crystals based on garnet hosts in a wide temperature range 8–500 K. Previous work on several scintillating materials based on silicate hosts showed nonzero constant signal from very low temperatures up to about 120 K. This observation supported a previously suggested hypothesis on low temperature losses of fast scintillation light due to quantum tunneling between the activator and nearby traps. In garnets, the subject of the present article, we observe practically constant signal in the entire monitored temperature range. We thus further test and confirm the quantum tunneling hypothesis in a different class of scintillating materials. We also show that there is no thermal ionization of the activator’s excited state in all materials studied, well above room temperature. [ABSTRACT FROM AUTHOR]

The Ce 3+ doped mixed crystals of Li 6 Y(BO 3 ) 3 and Li 6 Gd(BO 3 ) 3 are grown by Czochralski technique with equal mole ratios of both Yttrium and Gadolinium i.e. Li 6 Y 0.5 Gd 0.5 (BO 3 ) 3 . The grown crystals have the dimensions of ∅10×30 mm 2 . Powder X-ray diffraction (XRD) analysis confirmed single phase of the grown crystals. X-ray and laser induced luminescence spectra are presented. Scintillation properties such as energy resolution, light yield, decay time and α/β ratio under the excitation of 137 Cs γ-ray photons and 241 Am α-particles are also reported in this article. [ABSTRACT FROM AUTHOR]

Ce 1% doped Lu 2 Gd 1 Al 2 Ga 3 O 12 (LGAGG) single crystals with a diameter of 50 mm and length of 150 mm were grown by the Czochralski (Cz) method using an RF heating system. The EPMA techniques is employed to check homogeniousity of chemical composition. Luminescence and scintillation properties were also evaluated. The grown LGAGG showed light yield of around 25,000 photon/MeV and energy resolution was 9.8%@662 keV. The scintillation decay time was 53.6 ns at room temperature. [ABSTRACT FROM AUTHOR]

The luminescence and scintillation properties of SrI 2 :0.5%Yb 2+ have been investigated. SrI 2 :Yb single crystals were grown by the vertical Bridgeman method from the melt. They showed a light yield of 38,400 ph/MeV and energy resolution of 12.5% for the 662 keV full absorption peak. Yb 2+ photoluminescence intensity and decay time were studied between 78 and 600 K. Two emission bands centered at 418 and 446 nm were observed and ascribed to spin-allowed and spin-forbidden Yb 2+ 5d-4f transitions, respectively. Their corresponding room-temperature decay time constants are 710 ns and 77 μs. Both, the emission intensities and the decay time constants vary with temperature. The obtained results were interpreted using a model of self-absorption of Yb 2+ emission and a model of non-radiative relaxation of the electron from the low spin to the high spin 4f 13 5d Yb 2+ excited states. The radiative lifetime of the low spin Yb 2+ excited state was determined as 400 ns. [ABSTRACT FROM AUTHOR]

Novel Lu 2 WO 6 :Eu 3+ films with excellent luminescence performance were successfully prepared by Pechini method for the first time and characterized with X-ray diffraction (XRD), micro X-ray fluorescence imaging (μ-XRF), atomic force microscope (AFM), and X-ray excited luminescence (XEL), etc. Eu 3+ -doped films emitted strong red light peak wavelength at 612 nm under both UV light or X-ray excitation. The optimal annealing temperature and Eu 3+ -doped concentration are around 950 °C and 10 mol%, respectively. In addition, luminescence mechanism associated with Eu 3+ site occupation and possible energy transfer of Lu 2 WO 6 :Eu 3+ films have also been proposed. The optimized thin film shows great potential for applications as a candidate for X-ray imaging due to its high density, suitable emission wavelength and high light yield. [ABSTRACT FROM AUTHOR]

Ce3+-doped lutetium aluminum garnet (LuAG) phosphors have been successfully synthesized by a facile carbon-free sol-gel method without using any organic gelling agent. Phase transitions from gel to LuAG were well investigated by X-ray diffraction and thermal analysis. The results confirmed that a pure LuAG phase can form at around 920 °C by directly crystallizing from amorphous material. Particle size of the LuAG phosphor can be controlled by adjusting the heat treatment process; therefore, both nano and micron-scale products can be obtained and they are suitable for the fabrication of laser scintillators and white light emitting diodes, respectively. Agglomeration can be observed in the nano-sized phosphor. For the micron-sized LuAG, a two-step process was used to avoid hard agglomeration. Particles of the obtained micron-sized phosphor are uniform and well-dispersed. Luminescence properties of the phosphors were characterized. Relative intensity of the micron-sized product is comparable with commercial phosphor. [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]