Scintillation Decay Time Research Articles

Influence of calcium doping concentration on the performance of Ce,Ca:LuAG scintillation ceramics

Ce,Ca:LuAG scintillation ceramics with different Ca2+ co-doping concentrations were prepared by the solid-state reaction method. The concentration of Ce3+ was fixed at 0.3 at% and the concentration of Ca2+ ranged from 0 to 1.2 at%. We systematically studied how the Ca2+ concentration affects the optical quality of Ce,Ca:LuAG ceramics by influencing the microstructure in the vacuum sintering and HIP post-treatment. Good optical transmittance could be obtained with Ca2+ concentrations between 0.05 and 0.8 at%, which reached 76.0–81.9 % at 520 nm. The PL and scintillation decay times decrease with increasing Ca2+ concentration up to 0.6 at% with no clear trend above this value. The light yield (LY) values at different shaping times decrease with increasing Ca2+ concentration but the fast scintillation component (LY0.5 μs/ LY3.0 μs) increases significantly from 79 % to 97 %. The co-doping of Ca2+ also reduces the afterglow level by more than one order of magnitude.

Heading for brighter and faster β-Ga2O3 scintillator crystals

Czochralski-grown β-Ga2O3 and β-Ga2O3:Si crystals with the free electron concentrations between 2.5·1016 and 4.3·1018 cm−3 have been characterized by means of pulse height and scintillation time profile measurements in order to assess their basic scintillation properties. At room temperature, with increasing free electron concentration in the studied range, the scintillation yields decrease from 8920 to 1930 ph/MeV, while the mean scintillation decay times pare down from 989 to 61 ns. However, when the brightest β-Ga2O3 sample is cooled down below 100 K, its scintillation yield exceeds 20000 ph/MeV.

Fluorene Derivatives for Efficient Prompt Scintillation in Plastic Scintillators

Plastic scintillators have been investigated for γ-ray detection with the promise of fast response, ease of scale up, and mechanical toughness. However, their low light yield has been a major limiting factor in the performance metrics. Herein, we report a cross-linkable fluorene derivative, 9,9-bis(4-vinylbenzyl)-9H-fluorene (SF), copolymerized with the plastic matrix, to facilitate effective Förster resonance energy transfer to boost the light yield. Noncurable 9,9-dimethyl-9H-fluorene (MF) and 9,9′-spirobifluorene (SBF) were also introduced to bridge the energy transfer gap between the polymer matrix and the primary dye. The plastic scintillator comprising 5 wt % SF and 20 wt % MF exhibits a light yield of 11 600 photons/MeV with a scintillation decay time constant of 2.3 ns.

Ce concentration dependence on scintillation properties of Ce-doped yttrium pyrosilicate single crystal

Yttrium pyrosilicate (Y2Si2O7) single crystals are successfully grown by the floating-zone method with 0.5–10.0% of Ce-doping concentration. X-ray diffraction patterns indicate a single phase of Y2Si2O7 without the impurity phase. The series photoluminescence (PL) and scintillation properties are systematically explored in this study, including PL emission, PL decay time, X-ray induced scintillation spectra, X-ray induced scintillation decay time, afterglow profile, and pulse height spectra. Ce-doped Y2Si2O7 is presented interesting properties including the intense emission band at 390 nm from Ce3+ 5d-4f transition on both PL emission contour maps as well as X-ray-induced scintillation spectra in all samples. The afterglow level at 20 ms after X-ray irradiation of the Ce-doped YPS is comparable with commercial scintillators such as CdWO4 and Tl-doped CsI. Under 137Cs (662 keV) γ-ray irradiation 137Cs (662 keV), the highest scintillation light yield of Ce-doped Y2Si2O7 is reach up to 17,200 ph/MeV for 2.0% Ce-doped sample.

Ultrafast (600\xa0ps) \u03b1-ray scintillators

Large-size scintillators with high efficiency and ultrafast radiation fluorescence have shown more potential in the applications to ionizing radiation detection of medical diagnosis, nuclear control and high-energy physics. Currently, although traditional scintillators have made tremendous progress in scintillation efficiency, there are still challenges left in fluorescence lifetime. Faced with that problem, we adopted 2-inch ZnO as the substrate and doped gallium as activator to realize an ultrafast fluorescence excited by α-ray, of which the decay time is only 600 ps that is the shortest scintillation decay time reported so far. The results show that the shallow donor related with gallium not only effectively suppresses band-edge self-absorption, but makes ultrafast radiation possible, which gets gallium-doped ZnO as a potential scintillator for high-quality ultrafast dynamic imaging proved.

Scintillation Properties of Pr-Doped Lanthanum Pyrosilicate Single Crystals

Five samples of lanthanum pyrosilicate (La2Si2O7) single crystals with 0.5–10.0% Praseodymium (Pr)-doping concentrations were synthesized by the floating-zone method. Photoluminescence and scintillation properties of these crystals were investigated in this study for the first time. The multiple emissions from electron transitions of Pr3+ were observed on both a photoluminescence emission map and scintillation spectra, including the desired emission band of Pr3+ 5d–4f transition at 250–310 nm. The major photoluminescence and scintillation decay times were approximately 19 and 26 ns, respectively. When compared with commercial scintillators such as Tl-doped cesium iodide (CsI), the Pr-doped La2Si2O7 samples presented a respectively low afterglow level of 32 ppm after 20 ms of X-ray irradiation. Under 662 keV γ-ray irradiation from 137Cs, the 3.0% Pr-doped La2Si2O7 sample presented a scintillation light yield of 3200 ph/MeV, which was the best value among the tested samples.

Neutron-γ discrimination with organic scintillator crystal: 9-Phenylcarbazole (9-PCz) grown by Bridgman – Stockbarger method

Organic scintillator crystal 9-Phenylcarbazole (9-PCz) has been grown using Bridgman -Stockbarger technique. The crystal structure, lattice parameter and bond angle values are measured from single-crystal X-ray diffraction (SXRD) analysis. C–H inplane bending and out of plane bending and skeletal vibrations of 9-PCz molecule were identified from vibrational spectral analysis. UV–visible NIR spectral study shows that the crystal exhibits around 50% of transmittance in the infrared region and the direct optical bandgap energy is calculated to be 3.36 eV. Thermal properties of grown 9-PCz material were measured using thermogravimetric and differential thermal analyses (TG-DTA). The photoluminescence (PL) measurements show two emission bands with a maximum peak at 365 nm and a shoulder peak at 381 nm. X-ray induced luminescence spectrum of 9-PCz crystal exhibits a maximum emission peak at 381 nm. Scintillation decay time measurement shows the major component of 18 ns decay time. The pulse shape discrimination (PSD) capability of the grown crystal sample was studied for the signals induced by α-particles and γ-rays from 241Am and 137Cs sources, respectively. The figure of merit (FOM) is found to be 2.69. The preliminary results showed that the present studied organic crystal (9-PCz) scintillator can be considered in the field of fast neutron detection application.

Lead-Free Zero-Dimensional Organic-Copper(I) Halides as Stable and Sensitive X-ray Scintillators

Low-dimensional organic-metal halides are regarded as an emerging class of X-ray scintillation materials, but most of the discovered compounds are confronted with challenges of toxicity and instability. To address these challenges, we herein report two lead-free zero-dimensional (0D) hybrid halides, (Bmpip)2Cu2Br4 and PPh4CuBr2 single crystals, grown by the low-cost solution-processing method. By single-crystal X-ray diffraction refinement, the crystal structures of (Bmpip)2Cu2Br4 and PPh4CuBr2 were determined to be orthorhombic and monoclinic crystal systems, respectively. (Bmpip)2Cu2Br4 and PPh4CuBr2 show broadband orange and yellow emissions peaking at 620 and 538 nm, respectively. Different from the emission nature of the recent reported Cu-based halide hybrids, both (Bmpip)2Cu2Br4 and PPh4CuBr2 emit from excitons bound to defects featuring spin-allowed transition, enabling them to possess fast scintillation decay time of tens of nanoseconds, respectively. In particular, the (Bmpip)2Cu2Br4 single crystal has a high photoluminescence quantum yield of 48.2%, a high scintillation yield of 16,000 photons/MeV, and a low detection limit of 710 nGyair/s. Due to the combination of nontoxicity, long-term stability, and decent detection performance, (Bmpip)2Cu2Br4 could be regarded as a promising X-ray scintillator.

Scintillation and thermoluminescence characteristics of Tm-doped BaCaBO3F

Photoluminescence and thermally-stimulated luminescence (TSL) characteristics of BaCaBO3F doped with various amounts of Tm were evaluated. The Tm-doped BaCaBO3F showed an emission with a sharp peak around 460 nm originating from the 4f-4f transition of Tm3+ in photoluminescence and scintillation. Their photoluminescence and scintillation decay times for the Tm-doped BaCaBO3F were 0.68–0.73 and 1.28–1.55 ms, respectively. Furthermore, the TSL dynamic range of the glow peaks at 190 °C for the 0.5% Tm-doped BaCaBO3F was from 0.1 mGy to 1000 mGy. Furthermore, the TSL isothermal analysis of the Tm-doped BaCaBO3F suggested that at least 12 different activation energies related to TSL were confirmed.

Evaluation of photoluminescence and scintillation properties of Yb2+-doped CsMX3 (M = Ca, Sr; X = Cl, Br) crystals

The photoluminescence (PL) and scintillation properties of CsMX3:Yb2+ (M = Ca, Sr; X = Cl, Br) crystals grown using a self-seeding solidification method were demonstrated. During PL and scintillation, spin-allowed and spin-forbidden Yb2+ 4f14–4f135d transitions were observed for CsCaBr3:Yb2+ and CsSrBr3:Yb2+, whereas only spin-forbidden transitions were observed for CsCaCl3:Yb2+ and CsSrCl3:Yb2+. The scintillation decay time constants of the spin-allowed transitions for CsCaBr3:Yb2+ and CsSrBr3:Yb2+ were 210 and 64 ns, respectively, while those for the spin-forbidden transitions of CsMX3:Yb2+ (M = Ca, Sr; X = Cl, Br) were between 57 and 390 μs? Based on the pulse height spectra, light yields of CsMX3:Yb2+ (M = Ca, Sr; X = Cl, Br) were estimated to be between 2700 and 5500 photons/MeV. When the slow components were considered, the estimated range increased to 16,000–120,000 photons/MeV. CsCaCl3:Yb2+ and CsCaBr3:Yb2+ showed high total light yields of 48,000 and 120,000 photons/MeV, respectively, when compared to CsSrCl3:Yb2+ and CsSrBr3:Yb2+, for which the obtained yields were 16,000 and 23,000 photons/MeV, respectively. Owing to their high light yields, CsMX3:Yb2+ (M = Ca, Sr; X = Cl, Br) crystals, including the slow components, therefore have the potential to replace conventional scintillators in current-mode detectors.

A study of Mg2+ ions effect on atoms segregation, defects formation, luminescence and scintillation properties in Ce3+ doped Gd3Al2Ga3O12 single crystals

The undoped, Mg2+ doped, Ce3+ doped as well as Mg2+:Ce3+ codoped Gd3Al2Ga3O12 crystals were grown from the melt by the micro-pulling down method. Ce3+ and Mg2+ ions were codoped in a wide concentration range. A study of Mg2+ ion concentration effect on the luminescence and scintillation properties as well as segregation of atoms and defects creation processes were carried out. Mg2+ doping in Gd3Al2Ga3O12 led to the creation of OO• defects localized next to Mg2+ sites due to charge imbalance compensation. Consequently, neutral (MgGa/Al/GdOO)x defects were formed. In Ce3+ doped crystals, Mg2+ codoping changed the valence state from Ce3+ to Ce4+ to maintain charge neutrality. Hence, additional neutral (CeGd•-MgGa/Al/Gd′)x and (CeGd-MgGa/Al/GdOO)x defects appeared. Moreover, Mg2+ induced charge imbalance in GAGG crystal might also be compensated by the formation of oxygen vacancies (VO••). The Mg2+ ions imposed defects deteriorated the segregation of atoms. Accordingly the radial inhomogeneity of the crystals was diminished. The presence of stable Ce4+ and defects imposed by Mg2+ ions codoping were proved by absorption, photoluminescence, and scintillation decay time analysis. Hence, Mg2+ codoping resulted in quenching of the Ce3+ luminescence, acceleration of scintillation response, reduction of light yield, and thermally stimulated luminescence. The mechanism explaining a strong luminescence quenching with increasing Mg2+ ions concentration was proposed.

Scintillation properties of organic–inorganic layered perovskite-type compounds with a methylphenethylamine

Photoluminescence and scintillation characteristics of organic–inorganic layered perovskite-type compounds with a methylphenethylamine were evaluated for possible scintillator applications, and crystals of (2-CH3C6H4C2H4NH3)2PbBr4 (2CH3Phe), (3-CH3C6H4C2H4NH3)2PbBr4 (3CH3Phe) and (4-CH3C6H4C2H4NH3)2PbBr4 (4CH3Phe) were fabricated by a temperature gradient method. Emissions at 406 nm for 2CH3Phe, 433 nm for 3CH3Phe and 430 nm for 4CH3Phe were observed under X-ray irradiation. The scintillation light yields were 2700 photons MeV−1 for 2CH3Phe, 8200 photons MeV−1 for 3CH3Phe, 5800 photons MeV−1 for 4CH3Phe, which were lower than that of (C6H5C2H4NH3)2PbBr4. In addition, the scintillation decay times were 6.3 ns for 2CH3Phe, 7.6 ns for 3CH3Phe, 7.3 ns for 4CH3Phe, and they were found to be lower than that of (C6H5C2H4NH3)2PbBr4.

Scintillation characteristics of a NaI(Tl) crystal at low-temperature with silicon photomultiplier

The scintillation characteristics of a thallium-doped sodium iodide (NaI(Tl)) crystal with dimensions of 0.6 cm× 0.6 cm× 2 cm were studied by attaching a silicon photomultiplier (SiPM) directly to the crystal over a temperature range of 93–300 K. The scintillation light output and decay time were measured by irradiating 59.54 keV γ-rays with a 241Am source. We observed an approximately 20% increase in the light yield at 230 K compared with that at room temperature. Under these conditions, NaI(Tl) crystals with SiPM readout can be suitable for future dark matter search detectors.

Growth and scintillation properties of Ce doped [formula omitted]LiBr/LaBr[formula omitted] eutectic scintillator for neutron detection

In this study, Ce:6LiBr/LaBr3 eutectic with a high Li concentration was developed as a novel thermal neutron scintillator. Ce served as an activator for the LaBr3 phase, and Ce:6LiBr/LaBr3 eutectics were grown via the vertical Bridgman method in quartz ampoules (inner diameter = 4 mm). In the eutectic, the 6LiBr phase worked as the neutron capture phase by the 6Li (n, a) 3H reaction, and Ce:LaBr3 worked as the scintillator phase. The Ce:6LiBr/LaBr3 eutectic exhibited a lamellar eutectic structure and optical transparency, as well as 350 and 380 nm emission due to Ce3+ 5d-4f transition. The light yield under neutrons excitation was estimated to be 74000 photons/neutron. The scintillation decay time was 18.7 ns.

Growth and scintillation properties of directionally solidified Ce:LaCl3/AECl2 (AE = Mg, Ca, Sr) eutectic Scintillators

Ce-doped LaCl3/AECl2 (AE = Mg, Ca, Sr) system eutectics were explored. Ce-doped LaCl3/ AECl2 (AE = Mg, Ca, Sr) eutectics were grown using the Bridgman–Stockbarger method in quartz ampoules. In the case of AE = Mg, Ca, eutectics with submicron-diameter phase-separated scintillator fibers (PSSFs) structure were observed. In the case of AE = Sr sample, a solid solution of La0.708Sr0.292Cl2.708 was observed. The plate sample from the grown eutectics has some transparency. The grown eutectic structure showed a mixture of rods and plates shape. This mixed structure was aligned with a length of around 100–400 μm. The Ce:LaCl3/CaCl2 eutectic showed 345 nm emission ascribed to Ce3+ 4f-5d transition under X-ray excitation. The Ce:LaCl3/CaCl2 sample resulted in the highest light output of 9,000 photon/MeV, which is comparable to the previously reported eutectic scintillator Ce:GdAlO3/α-Al2O3, 9500 photon/MeV. Scintillation decay time of the Ce:LaCl3/CaCl2 sample under 662 keV gamma-ray excitation was 26.8 ns (26%) and 282 ns (74%).

Synthesis, crystal growth, structural and physicochemical properties of an organic single crystal (C11H16N2O4) for fast scintillation and NLO applications

The value of χ(3) for the present compound is comparable with that of other NLO materials, and it has a fast scintillation decay time of about 12 ns (94% contribution), which is comparable with that of standard organic scintillators.

Growth and scintillation properties of Eu doped Li2SrCl4/LiSr2Cl5 eutectic

In this study, a Eu-doped Li2SrCl4/LiSr2Cl5 eutectic with a high 6Li concentration was developed as a novel thermal neutron scintillator. The doped Eu served as an activator in the Li2SrCl4 and LiSr2Cl5 phases. The Eu-doped Li2SrCl4/LiSr2Cl5 eutectic was grown using the vertical Bridgman method in a sealed quartz ampoule. The eutectic exhibited a lamellar eutectic structure elongated along the pulling direction, and was optically transparent. The emissions at 401 and 412 nm were attributed to the Eu2+ 4f-5d transition in the Li2SrCl4 and LiSr2Cl5 phases, respectively. The light yield under 5.5 MeV α -rays was estimated to be 5,600 photons/5.5 MeV α -rays. The scintillation decay time was 312 ns. In the eutectic, the Li2SrCl4 and LiSr2Cl5 phases contributed to scintillation and neutron capture by the 6Li (n, a) 3H reaction.

Crystal growth and luminescence properties of phenanthrene for neutron detection

Phenanthrene crystals were grown by the self-seeding vertical Bridgman technique as a neutron scintillation material and their luminescence properties were evaluated. As-grown crystals had no secondary phases from the results of the powder X-ray Diffraction and Fourier transform infrared spectrometer measurements. The radioluminescence emission spectrum had a peak at 408 nm and its profile was similar to that of the photoluminescence emission spectrum. The relative light yield under 5.5-MeV alpha-ray was 1.15 times higher than that of lithium glass GS-20. The light yield of phenanthrene under 662 keV gamma-ray is estimated to be 38 ± 2% of NaI:Tl. The scintillation decay time under neutron excitation was estimated to be 7.30 ± 0.14 ns.

Stable and Bright Commercial CsPbBr3 Quantum Dot-Resin Layers for Apparent X-ray Imaging Screen.

CsPbBr3 quantum dots (QDs) have recently gained much interest due to their excellent optical and scintillation properties and their potential for X-ray imaging applications. In this study, we blended CsPbBr3 QDs with resin at different QD concentrations to achieve thick films and to protect the CsPbBr3 QDs from environmental moisture. Then, their scintillation properties are investigated and compared to the traditional commercial scintillators, CsI:Tl microcolumns, and Gadox layers. The CsPbBr3 QD-resin sheets show a high light yield of up to 21 500 photons/MeV at room temperature and a relatively small variation in light yield across a wide temperature range. In addition, the CsPbBr3 QD-resin sheets feature a small scintillation afterglow. The CsPbBr3 QD-resin sheets show a negligible trap density for the concentration below 50% weight, indicating that traps might arise from the aggregation of the QDs. The CsPbBr3 QD-resin sheets are also very stable at low irradiation intensities and relatively stable at higher intensities, with higher CsPbBr3 QD concentrations being more stable. Gamma-ray-excited-time-resolved emission measurements at 662 keV showed that the CsPbBr3 QD-resin sheets have an average scintillation decay time between 108 and 176 ns, which are still 10 000 and 6000 times faster than CsI:Tl and Gadox, respectively. Imaging tests show that the CsPbBr3 QD-resin sheets have a mean transfer function of 50% at 2 lp/mm and 20% at 4 lp/mm, comparable to that of commercial Gadox layers. This feature makes CsPbBr3 QD-resin sheets a good candidate for the low-cost, flexible X-ray imaging screens and γ-ray applications.

Luminescence and scintillation properties of Mo co-doped Y0.8Gd2.2(Al5-xGax)O12: Ce multicomponent garnet crystals

Mo co-doped Y0.8Gd2.2(Al5-xGax)O12:Ce (x = 2.6 and 3) multicomponent garnet crystals were grown by the micro-pulling down method and the luminescence and scintillation properties were investigated. The temperature dependences of radioluminescence yield and photoluminescence decay time were measured to investigate the temperature stability of these crystals. Under excitation with 662 keV γ rays at room temperature, Y0.8Gd2.2(Al2.4Ga2.6)O12:Ce,Mo shows a higher light yield of 53,800 ph/MeV whereas Y0.8Gd2.2(Al2Ga3)O12:Ce,Mo shows a faster scintillation decay times of 50 ns (56%) + 275 ns (44%). A decrease of radioluminescence yield at low temperature observed in correlation with an appearance of the large thermoluminescence peaks can be attributed to the localization of charge carriers at shallow traps.