Scintillation Decay Time Research Articles

Ca co-doped CsI(Tl) crystal scintillator for γ- and X-ray detecting applications

The vertical Bridgman method is used for the growth of single-doped CsI(Tl) and CsI(Tl:Ca) crystals, which has been evaluated for feasible applications in X-ray imaging and radiation detection. The powder XRD technique study reveals a single-crystalline phase of the grown crystal. The emission spectra show a broad emission band with a maximum of 540 nm under X-ray excitation, along with the characteristic emissions that arose from the Tl+ intra-center transition. The scintillation qualities of the grown crystal were studied via the pulse height spectra, scintillation light yield, energy resolution, and scintillation decay time. Pulse shape discrimination (PSD) was investigated under γ-rays and α-particles excitation sources. Moreover, the X-ray imaging application was investigated by an X-ray synchrotron at the Synchrotron Light Research Institute to study the performance of the grown crystal. These preliminary investigations suggest that the grown CsI(Tl:Ca) crystal can be one of the promising crystals for γ- and X-ray detecting applications.

High transparency Ce3+-doped oxyfluoride glass scintillator for X-ray imaging and γ-ray detection

High transparency Ce3+-doped dense gadolinium aluminum borosilicate (GSx) glass scintillator was synthesized in reducing atmosphere by melt-quenching process. The transmittance of the glasses exceeds 80%, and the light attenuation length is between 5-20 cm within the range of 400–600 nm. GSx glass shows an photoluminescence (PL) in range of 350–550 nm, with the strongest emission peak around 420 nm. The PL decay time of GSx glasses is around 37 ns, with a maximum PL quantum yield of 44.05%. The integrated X-ray excited luminescence (XEL) intensity of GSS glass is 52.5% compared with BGO crystal. For X-ray imaging, GSL glass based imaging system shows a high spatial resolution of 9 lp/mm, which is comparable to CsI:Tl X-ray detectors. Under γ-ray, the highest light yield of GSS glass is 1235 ph/MeV with an energy resolution of 24.0% at 662 keV, close to that of BSO crystal. The scintillation decay time of GSx glasses is consisted of fast (∼100 ns) and slow (∼560 ns) components. In thermally stimulated luminescence (TSL), GSS glass exhibits a strong TSL peak at approximately 440 K, with low intensity shoulders at about 520 K, implying different types of defects and traps. Therefore, GSx glass has promising prospects for X-ray imaging and high-energy physics applications.

Scintillator application of CsPbBr3 quantum dots-embedded SiO2 glasses

CsPbBr3 quantum dots-embedded SiO2 glasses were synthesized by the spark plasma sintering method as novel scintillators for γ-ray detectors. Their optical and scintillation properties were investigated to examine the scintillation performance. The X-ray diffraction patterns observed a halo peak of the SiO2 glass phase and diffraction peaks of CsPbBr3. An emission peak due to CsPbBr3 quantum dots was detected at around 515 nm in both photoluminescence (PL) and scintillation spectra. The PL and scintillation decay time curves included a component of nanosecond order, resulting from CsPbBr3 quantum dots. Under γ-ray irradiation from 137Cs, the light yield (LY) of the 0.2% CsPbBr3-embedded SiO2 glass was 150 photons MeV−1.

Luminescence and scintillation properties of TlCdCl3:Sb crystals

An ideal scintillator for X- and gamma-ray detection should have a high light yield and a high effective atomic number (Zeff). In this study, we developed undoped TlCdCl3 crystals and TlCdCl3:Sb (Sb: 0.5, 1.0 and 1.5 mol%) crystals with high Zeff (TlCdCl3:68.7), as candidate scintillators. The crystals were grown using the self-seeding solidification method, and their photoluminescence (PL) and scintillation properties were investigated. For the undoped TlCdCl3 crystals, emission peaks were observed at 460 nm and 485 nm in the PL and X-ray-induced radioluminescence (XRL) spectra, respectively. For the TlCdCl3:Sb crystals, the PL spectra showed emission peaks at 480, 480 and 500 nm, while the XRL spectra exhibited peaks at approximately 510 nm. The emission bands of the TlCdCl3:Sb crystals were shifted to longer wavelengths than those of the undoped TlCdCl3 crystals. The scintillation decay time constants for the undoped TlCdCl3 crystals were 51 and 2613 ns, whereas for the TlCdCl3:Sb crystals, they were in the range of 65–81 and 4550–7350 ns. These results suggest that the incorporation of Sb3+ ions induces long components of several thousand nanoseconds. The redshift and appearance of these long components indicate that Sb3+ ions act as new luminescence centers in the undoped TlCdCl3 crystal. The scintillation light yield of the TlCdCl3:Sb 1.0 mol% crystal was measured at 10,300 photons/MeV. The doping of Sb3+ ions into the TlCdCl3 lattice improved the scintillation light yield by up to four times compared to the undoped TlCdCl3 crystal.

One-Dimensional Copper-Doped Rb2AgI3 with Efficient Sky-Blue Emission as a High-Performance X-ray Scintillator.

Scintillators have garnered heightened attention for their diverse applications in medical imaging and security inspection. Nonetheless, commercial scintillators encounter challenges with costly rare-earth metals and toxic elements like thallium (Tl), driving the need for sustainable, cost-effective, and eco-friendly alternatives to meet contemporary X-ray detection demands. This study focuses on exploring the potential of Cu+-doped Rb2AgI3 as an effective metal halide (MH) scintillator. One-dimensional (1D) Rb2AgI3 and Cu+-doped Rb2AgI3 single crystals (SCs) were synthesized by using the conventional temperature-lowering crystallization method. When excited by UV light, Cu+-doped SCs emitted a broad sky-blue light at 490 nm with a high photoluminescence (PL) quantum yield (PLQY) of 76.48%. Remarkably, under X-ray excitation, these Cu+-doped SCs demonstrated an outstanding light yield of 36,293 photons MeV-1, a relatively low detection threshold of 1.022 μGyair s-1, and a rapid scintillation decay time of 465 ns. The prepared translucent scintillation film has good uniformity and flexibility, with a high spatial resolution of 10.2 lp mm-1. These results position Cu+-doped Rb2AgI3 as a leading candidate among promising X-ray scintillators, offering superior scintillation light yield, excellent stability, and nontoxicity.

Fabrication and luminescence properties of (K,Rb)2CuCl3 single crystal scintillators with one-dimensional structures

(K,Rb)2CuCl3 single crystal scintillators with one-dimensional structures were successfully fabricated by the slow cooling method, and their luminescence properties were evaluated. Broad photoluminescence (PL) peaks were observed at 350–500 nm, and the highest PL quantum yields were 96.4 % for (K0.5,Rb0.5)2CuCl3 among the samples. Under X-ray irradiation, scintillation peaks attributed to the recombination of self-trapped excitons were observed within the range of 350–500 nm. Both PL and scintillation decay time constants were obtained to be 10–15 μs. The best afterglow levels at 20 ms after X-ray irradiation for 2 ms were 5 ppm for (K0.75,Rb0.25)2CuCl3. The highest scintillation light yield was 16,000 photons/MeV for (K0.75,Rb0.25)2CuCl3 under 137Cs γ-rays (662 keV) irradiation. The results indicate that (K,Rb)2CuCl3 single crystals are promising as scintillators with high LY, low afterglow, and no hygroscopicity.

Effect of Dual-Organic Cations on the Structure and Properties of 2D Hybrid Perovskites as Scintillators.

Two-dimensional (2D) hybrid organic-inorganic perovskite (HOIP) crystals show promise as scintillating materials for wide-energy radiation detection, outperforming their three-dimensional counterparts. In this study, we synthesized single crystals of (PEA2-xBZAx)PbBr4 (x ranging from 0.1 to 2), utilizing phenethylammonium (C6H5CH2CH2NH3+) and benzylammonium (C6H5CH2NH3+) cations. These materials exhibit favorable optical and scintillation properties, rendering them suitable for high light yield (LY) and fast-response scintillators. Our investigation, employing various techniques such as X-ray diffraction (XRD), photoluminescence (PL), time-resolved (TR) PL, Raman spectroscopy, radioluminescence (RL), thermoluminescence (TL), and scintillation measurements, unveiled lattice strain induced by dual-organic cations in powder X-ray diffraction. Density functional theory analysis demonstrated a maximal 0.13 eV increase in the band gap with the addition of BZA cation addition. Notably, the largest Stokes shift of 0.06 eV was observed in (BZA)2PbBr4. The dual-organic cation crystals displayed >80% fast component scintillation decay time, which is advantageous for the scintillating process. Furthermore, we observed a dual-organic cations-induced enhancement of electron-hole transfer efficiency by up to 60%, with a contribution of >70% to the fast component of scintillation decay. The crystal with the lowest BZA concentration, (PEA1.9BZA0.1)PbBr4, demonstrated the highest LYs of 14.9 ± 1.5 ph/keV at room temperature. Despite a 55-70% decrease in LY for BZA concentrations >5%, simultaneous reductions in scintillation decay time (12-32%) may work for time-of-flight positron emission tomography and photon-counting computed tomography. Our work underscores the crucial role of dual-organic cations in advancing our understanding of 2D-HOIP crystals for materials science and radiation detection applications.

Vaporized purification and growth of optically transparent Trans-Stilbene for fast neutron detection applications

The paper reports the successful growth of large, crack-free trans-stilbene (TSB) single crystals using an in-house developed vertical Bridgman setup. The material purification involved a novel vaporized method at 130 °C. Parameters like furnace setup and ampoule’s cone angle were optimized during the growth process. The Powder XRD pattern confirms the phase of material and crystallinity. The crystal exhibited high transmittance (78 %) in the visible region, with an optical band gap of 3.4 eV. Photoluminescence study indicated strong blue emission at 380 nm, with radioluminescence spectroscopy showing emissions at 387 nm under X-ray radiation. The crystal exhibited a scintillation decay time of 6 ns under 137Cs gamma source, highlighting its fast decay and efficient PSD property with a figure of merit of 2.24 for fast neutron detection applications.

Luminescence and scintillation properties of fast Ce,Mg:Lu2YGaxAl5-xO12 ceramic scintillators fabricated from co-precipitated powders

Ce,Mg:Lu2YGaxAl5-xO12 (x = 1.5, 2, 2.5, 3) ceramic scintillators were fabricated by oxygen sintering combined with air annealing using nano-powders synthesized by the co-precipitation method. The Ce3+ 5d1 → 4f (2F5/2, 2F7/2) luminescence band was blue shifted with increasing Ga content due to the decrease in the crystal field splitting of the 5d levels. At room temperature (RT), the decrease of photoluminescence decay time and scintillation decay time was observed with increasing Ga content. At 662 keV γ-rays, the sample Ga2 exhibited high light yield (LY) of 28,700 photons/MeV, fast scintillation decay times of 17.7 ns (17 %) + 45.7 ns (83 %), and good time resolution of ∼220 ps. At RT, the decrease of LY value for the samples Ga2.5 and Ga3 could be attributed to the larger thermal ionization of the excited Ce3+ centers.

Determination of lutetium density in LYSO crystals: methodology and PET detector applications

Objective. Lutetium yttrium oxyorthosilicate (LYSO) scintillation crystals are used in positron emission tomography (PET) due to their high gamma attenuation, fair energy resolution, and fast scintillation decay time. The enduring presence of the 176Lu isotope, characterized by a half-life of 37.9 billion years, imparts a consistent radiation background (BG) profile that depends on the geometry and composition attributes of the LYSO crystals. Approach. In this work, we proposed a methodology for estimating the composition of LYSO crystals in cases where the exact Lutetium composition remains unknown. The connection between BG spectrum intensity and intrinsic radioactivity enables precise estimation of Lutetium density in LYSO crystal samples. This methodology was initially applied to a well-characterized LYSO crystal sample, yielding results closely aligned with the known composition. The composition estimation approach was extended to several samples of undisclosed LYSO crystals, encompassing single crystal and crystal array configurations. Furthermore, we model the background spectrum observed in the LYSO-based detector and validate the observed spectra via simulations. Main results. The estimated Lutetium composition exhibited adequate consistency across different samples of the same LYSO material, with variations of less than 1%. The result of the proposed approach coupled with the simulation successfully models the background radiation spectra in various LYSO-based detector geometries. Significance. The implications of this work extend to the predictive assessment of system behaviors and the autonomous configuration parameters governing LYSO-based detectors.

Optical properties of pure and Sn-doped β-Ga2O3 single crystals grown by optical float zone technique

High-quality single crystals of both pure and Sn:β-Ga2O3 single crystals weregrown using the optical floating zone technique and a comprehensive study of its luminescence and scintillation properties was carried out. The pure and Sn:β-Ga2O3 grown crystals were oriented along (100) by Laue diffraction pattern and its monoclinic structure was confirmed using a single crystal XRD. X-ray induced luminescence spectrum shows a maximum emission peak at 365 nm. The cut off wavelength was observed around 258 nm and the optical band gap was calculated to be 4.64 eV from UV–Vis-NIR transmission spectroscopy. The room temperature Raman spectra were recorded and the various vibration modes were investigated. Low temperature (10 to 300 K) and high temperature (325 to 675 K) TL measurements were carried out on X-ray irradiated crystals and its TL kinetic parameters such as activation energy (eV) and frequency factor (S) were calculated. Scintillation decay time profiles were measured for both pure and Sn-doped crystals under 137Cs γ-ray excitation. The calculated scintillation light output is 2300 Ph/5.5 Mev for Sn:β-Ga2O3 crystal under α-particle excitation from 241Am radiation source.

Scintillation and photoluminescence performance of Ce3+-doped high gadolinium oxyfluoride glass for circular electron-positron collider (CEPC)

The large size (4 cm × 4 cm × 1 cm) Ce3+-doped high gadolinium oxyfluoride glass with density of 5.83 g/cm³ was prepared by the melt quench method at 1220 °C. The glass is colorless and transparent over the visible range. The prolonged decay time under 275 nm UV light demonstrates the energy transfer from Gd3+ ions to Ce3+ ions. The X-ray excited luminescence spectra (XEL) show the emission peak corresponds to the 5d→4f transitions of Ce3+ ion. The integral emission intensity of glass was compared with that of bismuth germanate oxide (BGO) crystals. The scintillation property of glass was studied under the γ-ray from 137Cs source and a clear energy peak was observed with light yield (LY) over 1100 ph/MeV. The scintillation decay time comprises fast and slow components. All results presented in this work indicate the appropriate potential to be high-energy rays detecting material for CEPC.

Characteristics of Ce-doped phosphate inorganic glass scintillators for gamma- and X-ray detection

We report on the structural, photoluminescence (PL), and scintillation properties of Ce-doped P2O5–Al2O3–Cs2O–BaO glass scintillators having different Ce concentrations (1.96, 3.85, 7.41, 10.7, and 13.8 mol%) for gamma- and X-ray detection. The highest density (3.57 g/cm3) was achieved with Ce concentration of 13.8 mol%. The PL emission and X-ray-induced radioluminescence spectra showed emission peaks corresponding to the allowed transition from the Ce3+ 5d excited state to the 4f ground states. The highest scintillation light yields (approximately 2200 photons/MeV) were achieved with Ce concentrations of 7.41, 10.7, and 13.8 mol%. These light yields are higher than those previously reported for glasses containing heavy elements, such as Eu-doped SiO2–Al2O3–HfO2 (630 photons/MeV), Ce-doped P2O5–Li2O–GdI3–Al2O3–CaCO3 (1600 photons/MeV), and Ce-doped SiO2–Al2O3–BaF2–Gd2O3 (2050 photons/MeV). For all glasses, short scintillation decay times (28.5–34.0 ns) corresponding to the transition from the Ce3+ 5d excited state to the 4f ground states were observed. These results indicate that the fabricated glass with an optimal Ce concentration of 13.8 mol% is suitable for gamma- and X-ray detection.

Characterization of scintillation properties in Ca(Nb,Ta)2O6 single crystals

CaNb2-xTaxO6 (x = 0, 0.2, 0.5 and 1) single crystals were fabricated by the floating zone method, and their photoluminescence (PL) and scintillation properties were evaluated. Under excitation at 280 nm, CaNb2-xTaxO6 single crystal showed a broad emission band at 400–600 nm. From the decay time constant, the observed emission was attributed to the charge transfer (CT) from the Nb5+ to the O2−. Under X-ray irradiation, an emission peak was observed at 470 nm, and the scintillation decay time profile suggested that the origin of the emission was also CT from the Nb5+ to the O2−. CaNb2O6 showed the highest light yield of 15,000 ph/MeV and the lowest afterglow level of 6.03 ppm among the synthesized samples.

Growth difficulties and growth of crack free Eu2+ activated KSr2I5 scintillator single crystal by vertical bridgman-stockbarger technique for radiation detection applications

Europium activated potassium strontium iodide (KSr2I5:0.5Eu2+) compound was synthesized and refined by indigenous zone-refinement experimental set-up. The impurities that are insoluble in the KSr2I5:Eu2+ compound was filtered by using a specifically programmed dual chamber quartz ampoule with frit filter method. Temperature profile of this in-house built vertical transparent Bridgman-Stockbarger technique growth furnace is optimized to grow quality single crystals of KSr2I5:Eu2+. From the photoluminescence emission spectrum a typical 4f6 5d1 – 4f7 transition is observed for a broad emission peak at 432 nm whereas a broad emission peak at 448 nm was obtained from the X-ray excited radioluminescence spectrum. The gamma ray spectrometer was administered to detect the scintillation properties of the grown crystal. The scintillation decay time was calculated for the KSr2I5:Eu2+ crystal wherein the energy resolution under 137Cs sealed gamma source is found to be 3.5 % at 662 KeV.

Temperature dependence of photo- and radio-luminescence and scintillation properties of Lu2YAl2.5Ga2.5O12:Ce,Mg multicomponent garnet crystals

Luminescence and scintillation properties of Lu2YAl2.5Ga2.5O12:Ce,Mg (0.02, 0.05 %) garnet crystals grown by the micro-pulling down method were investigated. The onset temperature for luminescence quenching at ∼365 K is determined from the temperature dependence of photoluminescence decay time. At room temperature, the Mg (0.05 %) sample exhibits high integral scintillation efficiency of ∼445 % of BGO crystal, light yield value of 23,500 photons/MeV, and fast scintillation decay times of 20 ns (15 %) + 54 ns (85 %). The higher radioluminescence intensity of the Mg (0.05 %) sample correlates with an appearance of its lower themally-stimulated luminescence intensity in 77–500 K range.

Optical and scintillation properties of Lumilass-G and -R glasses

Commercial phosphor glasses, namely, Lumilas-G9 and -R7 were investigated on their optical and scintillation characteristics. In transmittance, close to 90% transmission was achieved in both glasses at visible wavelength, and some specific absorption lines due to 4f-4f transitions of Tb3+ and Eu3+ were detected in Lumilass-G9 and -R7, respectively. In photoluminescence and scintillation, several sharp emission lines were observed in both glasses, and the emission origins of them were attributed to 4f-4f transitions of Tb3+ and Eu3+. Under pulse X-ray irradiation, the scintillation decay time of both Lumilas-G9 and -R7 resulted in 1.3 ms. To determine the scintillation light yield, α-rays from 241Am were irradiated to these samples, and the light yields of Lumilas-G9 and -R7 estimated by pulse area measurements turned out to be 700 and 1800 ph MeV−1, respectively.

Photoluminescence and scintillation properties of Pr-doped (Lu, Y)2Si2O7 crystals

Pr-doped (Lu1−x , Y x )2Si2O7 (x = 0.25, 0.5, and 0.75) crystals were synthesized by the floating zone method. Emission peaks due to 5d–4f transitions of Pr3+ were observed at 300 nm under excitation of both UV light and X-rays. Scintillation decay times of 19–22 ns were obtained, and they originated from the 5d–4f transitions of Pr3+. Afterglow levels became high from 64.7 to 541 ppm as the Y-admixed concentration increased. The light yields were estimated to be 560–700 photons MeV−1 by comparing the channels of photoabsorption peaks from the pulse height spectra of 137Cs γ-rays measured using prepared crystals and commercial Gd2SiO5 reference.

Eu concentration dependence of photoluminescence and scintillation properties on Eu-doped Y3Al5O12 single crystals

(Eux,Y1-x)3Al5O12 (x = 0.005, 0.01, 0.05, 0.10, 0.15, and 0.20) single crystals were prepared by the floating-zone method. We investigated their photoluminescence (PL) and scintillation properties including PL excitation/emission contour spectra, PL quantum yields, PL decay times, X-ray-induced scintillation spectra, scintillation decay times, and pulse-height spectra under γ-ray irradiation from 137Cs (662 keV). The PL and scintillation spectra exhibited some emission lines at visible wavelength due to the 4f-4f transitions of Eu3+ ions, and the PL and scintillation decay times resulted several milliseconds. Among all the samples, (Eu0.1,Y0.9)3Al5O12 and (Eu0.15,Y0.85)3Al5O12 single crystals showed the highest PL quantum yield. On the other hand, (Eu0.01,Y0.99)3Al5O12 single crystal showed the highest light yield. The light yield of the sample was estimated to be 36,000 photons/MeV from the pulse height spectrum.

Evaluation of rate capability of SiPM-based X-ray counting detector

Scintillation radiation detectors based on silicon photomultipliers (SiPMs) are widely used nowadays both in various medical apparatus and physics experiments, e.g., in PET. At the same time, this technology has great potential in terms of creating X-ray photon counting detectors, which are in demand both in medicine and applied research. In this work, we investigate the influence of main SiPM parameters on the overall system performance, as well as different methods of data readout. It is shown that the use of SiPMs with shorter cell recovery time and larger number of microcells makes it possible to achieve a rate capability of 12 Mcps (mega counts per second) per channel. At the same time, the scintillator decay time is still among the limiting factors for such systems.