Scintillation Properties Research Articles

Water-based quantum dots liquid scintillator for particle physics

Liquid scintillators are typically composed from organic compounds dissolved in organic solvents. However, usage of such material is often restricted due to fire safety and environmental reasons. Because of this, R&D of water-based liquid scintillators is of extreme relevance; yet, no such scintillators have been made commercially available as yet. Here, we investigate an alternative, water-based quantum dots liquid scintillator. Pre-determined and controllable optical properties of the quantum dots, as well as the existence of large libraries of established protocols for their dispersion in aqueous solutions, make them an attractive option for nuclear and particle physics applications. We characterize the optical properties of water-based quantum dots liquid scintillator and find that most of its optical properties are preserved upon quantum dots' phase transfer into water, through the addition of an oleic acid hydrophilic layer. Using the developed scintillator, the time and charge responses from atmospheric muons are measured, highlighting the practical viability of water-based quantum dots liquid scintillators for nuclear and particle physics, special interest on neutrino physics.

On the properties of lower mid-latitudes ionospheric scintillation observed over Chengdu, China

Low and high-latitude ionospheric scintillations are well-documented, but data on lower mid-latitude scintillations are scarce. Moreover, there is limited public reporting for the Chengdu station, which makes the data for the consecutive three years particularly valuable. This paper analyzes three years of ionospheric scintillation data from Chengdu and compares it with Chongqing. GNSS receivers in Chengdu (104.07°E, 30.67°N) and Chongqing (106.55°E, 29.57°N) recorded the data from 2018 to 2020. A custom data processing program for GPS/BDS/Galileo monitors was used. Results show diurnal and seasonal variations in the occurrence rate (OR) of scintillation events, with higher OR in spring and autumn, predominantly at night. There is a positive correlation between the annual OR of weak, moderate, and strong scintillations. Besides, moderate scintillation and strong scintillation events mainly occur at azimuth angles of 30°-90°, 150°-210°, and 300°-330° due to the aspect sensitivity of ionospheric irregularities. Solar activity, mesospheric winds, and ionospheric tides also influence scintillations. Notably, intense events were observed in May 2018(a year of low solar activity) due to post-sunset occurrences influenced by neutral wind and ionospheric tides, suggesting that in addition to solar radiation, neutral wind and ionospheric tides may serve as substantial driving mechanisms for ionospheric scintillation. This study provides a reference for the construction of a scintillation prediction in lower mid-latitudes.

Ga/Al ratio induced afterglow behavior of Ce3+:GAGG scintillation ceramics

This work investigated the optical and scintillation properties of cerium-doped gadolinium aluminum gallium garnet (Ce:GAGG) ceramics with different gallium-to-aluminum (Ga/Al) ratios. The optical transmittance, fluorescence spectra, fluorescence lifetime, light yield, scintillation decay, and afterglow characteristics of the ceramic samples were studied. The experimental results reveal that the decay time of Ce:GAGG ceramic is significantly decreased with the increase of Ga content. The mean decay time of 60 ns is achieved when the Ga/Al ratio is 3:2 in our experiment. The light yield of ceramics varies from 12,140 to 44,825 ph/MeV with the change of Ga content, and the highest light yield is achieved when the Ga/Al ratio is 2.4:2.6. Noteworthy fluctuation in the afterglow performance is affected by the Ga content significantly. The afterglow intensity of the sample with Ga/Al = 2:3 is approximately 0.5 % of its initial intensity after the X-ray excitation was turned off for 5 s. The formation mechanism of defects which is related with the afterglow behaviors were investigated and discussed.

Investigation of scintillation properties of a CsI(Tl) crystal at low temperature for dark matter search

The Korea invisible mass search (KIMS) experiment used CsI(Tl) crystals coupled with photomultiplier tubes (PMTs) to detect signals from weakly interacting massive particles (WIMPs) at room temperature. It is expected that combining CsI(Tl) crystals with silicon photomultipliers (SiPMs) will enhance the detection performance. However, SiPMs must operate at low temperatures to reduce the dark count rate. In this study, we examined the temperature dependence of CsI(Tl) crystal properties, including light yield, α/β ratio, decay time, and pulse shape discrimination, before integrating it with a SiPM. The CsI(Tl) crystal was placed in a low-temperature chamber with a radiation source, and scintillation photons were detected by a PMT positioned outside the chamber. The response of CsI(Tl) to α-particles and γ-rays was examined across temperatures ranging from 10 K to 300 K.

Crystal Growth of Quaternary AkRE2Si2S8 (Ak = Ca and Sr; RE = La-Tb) Thiosilicates Using Flux-Assisted Boron Chalcogen Mixture Method: Exploring X-ray Scintillation, Luminescence, and Magnetic Properties.

We report on the detailed structural analysis of a series of 11 new quaternary rare earths containing thiosilicates, AkRE2Si2S8 (Ak = Ca and Sr; RE = La, Ce, Pr, Nd, Sm, Gd, and Tb), synthesized using the flux-assisted boron chalcogen mixture method. High quality crystals were grown and used to determine their crystal structures by single crystal X-ray diffraction. All members of the AkRE2Si2S8 series crystallize in the trigonal crystal system with space group R3̅c (space group no. 167). Polycrystalline powders were used for physical property measurements, including magnetic susceptibility, diffuse reflectance in the UV-visible range, and scintillation. Magnetic measurements indicated that CaRE2Si2S8 (RE = Nd and Tb) exhibits paramagnetic behavior with a slightly negative Weiss constant. The band gaps of the materials were determined from diffuse reflectance data, and optical band gaps were estimated to be 2.5(1) and 2.9(1) eV for CaCe2Si2S8 and CaGd2Si2S8, respectively. CaCe2Si2S8, CaTb2Si2S8, and SrCe2Si2S8 exhibited intense green luminescence upon irradiation with 375 nm ultraviolet light and, furthermore, scintillated when exposed to X-rays. Radioluminescence measurements of CaCe2Si2S8 powder revealed green emission with an intensity approximately 14% of that emitted by bismuth germanium oxide powder.

Optimizing doping thresholds for enhanced scintillation in 2D hybrid organic–inorganic perovskites

Two-dimensional hybrid organic–inorganic perovskite (2D-HOIP) crystals, in particular lead-bromide perovskites, exhibit great promise as scintillators due to their superior environmental stability compared to their 3D counterparts, offering high light yields and rapid decay times. These cost-effective, solution-processable materials demonstrate potential for efficient wide-energy radiation detection. In this paper we focus on investigating the effect of partial substitution of n-butylammonium (BA) cation with tert-butylammonium (t-Bu) cation within the butylammonium lead bromide (BA2-xtBuxPbBr4) structure and its impact on luminescence and scintillation properties. We observe that inclusion up to 5 % of t-Bu (x = 0.1) within the structure leads to a narrowing of the bandgap, leading also to an improvement of the light yield by 10 % and lowering of the energy resolution, compared to pristine BA2PbBr4. The bandgap widens, compared to pristine BA2PbBr4, with higher concentrations above 5 %, resulting in effects for the scintillating properties of the 2D-HOIP at room temperature at t-Bu concentrations above 5 %, with reduced light yield and broadened energy resolution. Higher t-Bu concentration (x = 0.4) show very poor room temperature scintillation but increased efficiency at cryogenic temperatures below 50 K. The results shown in this paper demonstrate the fundamental limitation of organic cation mixing levels for scintillation efficiency enhancement.

Optical, scintillation, and dosimetric properties of undoped and Mn-doped MgGa2O4 single crystals

Optical, scintillation, and thermally and optically stimulated luminescence (TSL and OSL) properties of the undoped and Mn-doped MgGa2O4 single crystals were investigated. All the crystals showed a luminescence peak at 500 nm caused by the 3d–3d transitions of Mn2+. The 0.03 %-Mn-doped crystal exhibited the highest OSL intensity, whereas the 0.3 %-Mn-doped crystal exhibited the highest photoluminescence quantum yield and scintillation intensity. There was an inverse relationship between the scintillation and OSL intensity in the 0.03–0.3 % Mn-doped crystals. The results indicated that the 0.03 % Mn-doped crystal exhibits the highest efficiency during carrier trapping. In the OSL dose response functions, the lower detection limit of the 0.03 % Mn-doped crystal was 0.01 mGy, which was comparable with that of a commercial product.

Scintillation and structural properties of copolymers and mixtures of styrene, 9-vinylcarbazole and 4-vinylbenzyl chloride based plastic scintillators

The research team has developed new plastic scintillators in the form of microspheres, called PSm, by combining styrene, 9-vinylcarbazole (VK), and 4-vinylbenzyl chloride (VBC). The primary objective of this study was to explore the feasibility of incorporating the fluorescent solute (VK) into the polymer structure to prevent its leaching out when PSm are utilized in liquid flow through detection systems or organic solvents. The secondary aim was to examine the impact of adding the chlorine functional group to the scintillation polymer, with the intention of replacing it with an extractant in the future to create covalently linked PSresins.The findings of the study reveal that the homopolymer of polyvinylcarbazole (PVK) performs poorly while used as a unitary scintillator system for plastic scintillation measurements. However, the incorporation of monomers in the form of copolymers with styrene has a more significant impact on scintillation properties compared to the mixture of homopolymers. In the case of 9-vinylcarbazole (VK), its presence at a weight proportion of 10% leads to an increase in scintillation efficiencies, although it is still inferior to the classical PS. Conversely, the situation is different for 4-vinylbenzyl chloride (VBC), where the chlorine in the copolymer results in higher quenching, and the polymer is also less resistant to organic solvents due to the formation of short polymer chains. For VBC, the mixture of polymers yields better results and enables the production of covalently linked PSresins.

Probing the optical properties and toxicological profile of zinc tungstate nanorods.

Zinc tungstate is a semiconductor known for its favorable photocatalytic, photoluminescence, and scintillation properties, coupled with its relatively low cost, reduced toxicity, and high stability in biological and catalytic environments. In particular, zinc tungstate evinces scintillation properties, namely the ability to emit visible light upon absorption of energetic radiation such as x rays, which has led to applications not only as radiation detectors but also for biomedical applications involving the delivery of optical light to deep tissue, such as photodynamic therapy and optogenetics. Here, we report on the synthesis of zinc tungstate nanorods generated via an optimized but facile method, which allows for synthetic control over the aspect ratio of the as-synthesized anisotropic motifs via rational variation of the solution pH. We investigate the effect of aspect ratio on their resulting photoluminescent and radioluminescent properties. We further demonstrate the potential of these zinc tungstate nanorods for biomedical applications, such as photodynamic therapy for cancer treatment, by analyzing their toxicological profile within cell lines and neurons.

A Review of Recent Improvements in Novel Liquid Scintillator Materials

Liquid scintillator detectors have great advantages in the field of radionuclide detection because of their low detection limit, high sensitivity, and diverse functions. However, the material properties of liquid scintillators directly determine their detection effectiveness, which leads to their poor vertex resolution and particle identification. In this work, we introduce the improvement methods, choices, and properties of different novel liquid scintillator materials in recent years. This article is expected to provide references for the development and research of liquid scintillator materials in various application fields.

Neutron detection properties of Ti-doped LiGaO2 single crystalline scintillator

Photoluminescence (PL) and scintillation properties of undoped and Ti-doped LiGaO2 single crystals were investigated. In both PL and scintillation, the Ti-doped LiGaO2 crystals showed luminescence due to charge transfer between Ti4+–O2- while the undoped LiGaO2 crystal showed luminescence due to oxygen vacancies. Under thermal neutron irradiation, all the LiGaO2 crystals exhibited a clear thermal neutron peak, and the highest light yield was observed from the 3% Ti-doped LiGaO2 crystal. The light yield of the 3% Ti-doped LiGaO2 crystal was ten times higher than that of the undoped LiGaO2 crystal and comparable with that of a commercial neutron scintillator GS20. In addition, the Ti-doped LiGaO2 crystals showed high α/γ ratios up to about 0.7.

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.

Development of Tm-doped CaHfO3 single-crystal-scintillators for application to integrated-type detectors

Photoluminescence and scintillation properties of Tm:CaHfO3 single crystals were investigated. From the results of photoluminescence properties, all the Tm:CaHfO3 samples showed emission bands due to the 4f–4f transitions of Tm3+, and the 1.0% Tm:CaHfO3 sample showed the highest quantum yield among all the samples upon excitation at 360 nm. The afterglow levels at 20 ms after X-ray irradiation for 2 ms were approximately 12 000 ppm. Pulse height spectra using 137Cs as γ-ray source revealed the 1.0% Tm:CaHfO3 sample showed the highest light yield of 1250 photons MeV−1 among all the samples.

Energy transfer study on dense and transparent Eu3+/Tb3+-coactivated TeO2-Gd2O3-WO3-ZnO glass scintillators☆

Tb3+-, Eu3+-activated and Eu3+/Tb3+-coactivated TeO2-Gd2O3-WO3-ZnO (TGWZ) glasses with the density of about 6.60 g/cm3 were successfully synthesized by a melt-quenching method. These glass scintillators show a line transmittance coefficient in excess of 80% in the strongest green-emitting regions of Tb3+ ions. The optimal concentration of incorporated Tb3+ and Eu3+ ions and the corresponding interaction mechanism are determined in both Tb3+ and Eu3+-activated TGWZ glasses. Compared with that of Tb3+-activated TGWZ glasses, the luminous intensity of the Eu3+/Tb3+-coactivated TGWZ glasses is enhanced by 7.6 times, which can be attributed to the effective energy transfer (ET) from Tb3+ to Eu3+ ions. By investigating the concentration-dependent optical properties of these glasses including transmittance, photoluminescence (excitation and emission spectra), photoluminescence decay, the mechanism of ET in Eu3+/Tb3+-coactivated TGWZ glass scintillators is obtained. Also, the potential scintillation properties of the TGWZ glass scintillators are discussed by X-excited luminescence (XEL) spectra and the corresponding X-ray dose response tailored by various current intensity within 0–240 μA (which corresponding to 0–40000 mGy).

Scintillation properties of Eu-doped LiBr crystalline scintillators under X-, γ-ray, and neutron irradiation

Scintillators for neutron detection have been required as alternative detectors for 3He gas proportional counters, which are in short supply. Therefore, Eu-doped LiBr single crystals as new scintillators for neutron detection were synthesized by the vertical Bridgman method, and the photoluminescence and scintillation properties were evaluated. Under ultraviolet light and X-ray irradiation, the emission due to 4f65d1–4f7 (8S7/2) transitions of Eu2+ was observed at 440 nm. According to pulse height spectra under 252Cf neutron irradiation, 0.01 % Eu-doped LiBr showed the highest light yield of 4600 ph/n among the prepared samples, and the α/γ ratio of 0.01 % Eu-doped LiBr was 0.37, which was better than that of commercial GS20 scintillator.

Study on scintillation properties and proton-induced radiation damage of LaCl[formula omitted] crystals

A Cs2LiYCl6 (CLYC) scintillation crystal is a promising candidate for fast neutron spectroscopy due to its dual mode gamma/neutron capability and good energy resolution. Despite promising features, CLYC’s limited radiation tolerance and inability to separate alpha/proton particles using pulse shape discrimination (PSD) method restrict its applicability in fast neutron spectroscopy. The significant cross-sections for 35Cl(n,p)35S and 35Cl(n, α)32P reactions make 35Cl-containing crystals attractive candidates for fast neutron detection, prompting their development as a promising new solution. This study reports the growth of LaCl3 crystals via the Bridgman technique, enabling further exploration of their scintillation and material properties for fast neutron detection applications. The effects of the proton irradiation on LaCl3 crystals were investigated by irradiating them with a 100 MeV proton beam at the Korea Multi-purpose Accelerator Complex. The study quantified radiation damage by comparing the pre- and post-irradiation scintillation properties and PSD of the LaCl3 crystals. The results of the measurements demonstrate that LaCl3 crystals are promising candidates for applications in fast neutron identification, spectroscopy, and space mission, maintaining performance even under high-radiation environments.

Novel Tb3+ doped borophosphate glass scintillator for X-ray imaging

In this study, we introduce an efficient green-emitting material made from Tb3+ doped borophosphate scintillating glass for X-ray imaging. An influence of Tb2O3 concentration on the physical, optical, luminescent, and scintillation properties of glasses were investigated. The glass density and refractive index increase, while the molar volume and Tb3+ inter-ionic distance decreases with Tb2O3 addition. These glasses absorb the photons in range of UV, Vis, and NIR. The excitations by UV and X-ray on glasses causes the strong green emission centered around 545 nm by the 5D4 → 7F5 transition of Tb3+. The energy transfer from Gd3+ to Tb3+ was occurred in this emission. The glass doped with 4 mol% of Tb2O3 demonstrates the highest emission intensity at 545 nm due to the concentration quenching. The decay time of glasses are in few milliseconds. The integral X-ray scintillation efficiency of 4 mol% doped glass is 52% compared to that of BGO crystal. Additionally, this glass was proceeded in the X-ray imaging and yielded the image with satisfied resolution, characteristics and MTF values, compared to that obtained from YAG:Ce crystal. The developed glass has a potential for X-ray imaging applications, especially in the medical imaging, flaw detection, and security inspection.

Improvement of scintillation light yield of Tb:CaHfO3 by Mg-substitution

1.0 % Tb:Ca1-xMgxHfO3 (x = 0.05, 0.075, and 0.1) single crystals were synthesized by the floating zone technique, and their photoluminescence and scintillation properties were evaluated. The x = 0.1 sample showed the highest quantum yield of 18.7 % under excitation at 250 nm among all the samples. All the samples showed scintillation with multiple emission lines originating from the 4f–4f transitions of Tb3+. From the pulse height spectra, the highest light yield was 17,400 photons/MeV in the x = 0.075 sample among the samples, and all the samples outperformed the light yield of the unsubstituted one.

Temperature dependence of photoluminescence kinetics and scintillation properties of LuY2(Al5-xScx)O12:Ce (x = 1, 1.5, 2) garnet single-crystalline films

The temperature dependence of photoluminescence (PL) kinetics and scintillation properties were investigated in LuY2(Al5-xScx)O12:Ce (x = 1, 1.5, 2) garnet single-crystalline films grown by the isothermal liquid phase epitaxy method. With the increase of Sc content, the Ce3+ 5d1 level was shifted to higher energy while the Ce3+ 5d2 level was shifted to lower energy due to the decrease in crystal field splitting of the 5d levels. Activation energy of thermal quenching, determined from temperature-dependent PL decay times, decreased with increasing Sc content. At room temperature, the decrease of light yield (LY) value with increasing Sc content is caused by the thermal ionization process. LuY2(Al4Sc)O12:Ce showed a LY value of 510 photons/MeV when excited by 5.5 MeV α-particles, which is ∼21 % larger than that of Lu2Y(Al4Sc)O12:Ce due to a smaller bandgap Eg of the former.

Modulation of components toward blue light emission and scintillation properties of Eu2+ activated Sr1-xLaxMgxAl12-xO19 crystal

The development of Eu2+-activated oxide materials with high efficiency, fast decay and narrow bandwidth emission in the visible region is still challenging for the field of luminescence and scintillation applications. Generally, Eu2+ in oxide hosts can emit intense and broad 5d-4f emission in the visible region, but efficient emitting with stable bivalence of Eu is rare in inorganic oxide system. In this work, a series of ASL:Eu2+ (Sr1-xLaxMgxAl12-xO19) powder samples with various La, Mg doping ratios were designed and synthesized to modulate the UV or X-ray excited luminescence properties, including redshift, quantum yield, and decaying lifetime. Moreover, an ASL:Eu2+ crystal with the optimal ratio x = 1/3 was grown, its scintillation performance was compared with standard Bi4Ge3O12 crystal sample and evaluated in detail. These results indicate that the ASL:Eu2+ crystal is potential scintillator as a kind of X-ray detection and provide a reference for the further development of high-performance Eu-activated oxide scintillation materials.