Scintillator Research Articles

Optical, scintillation, and dosimetric properties of undoped and Tb-doped CaYAlO4 single crystals

Optical, scintillation, and dosimetric properties of the undoped and Tb-doped CaYAlO4 single crystals grown by the floating zone method were evaluated. Several photoluminescence (PL) emission peaks due to the 4f–4f transitions of Tb3+ ion were observed at 385–620 nm under excitation at 250 nm in Tb-doped CaYAlO4 samples. Under X-ray irradiation, scintillation peaks of the Tb-doped CaYAlO4 crystals were consistent with the PL emission peaks. In terms of a dosimetric property, the 0.1% Tb-doped crystal exhibited the highest thermally stimulated luminescence intensity and the widest linear responses in the range of 0.01–1000 mGy among the samples.

Effects of Ce3+ substitution on the local structure of cerium and scintillation properties of CLLBC:Ce crystals

In this work, a strategy of controlling the doping concentration of cerium is adopted to improve the gamma response performance of cutting-edge Cs2LiLa(Br,Cl)6:Ce (CLLBC:Ce) single crystal scintillators. A serial of Ce3+-doped Cs2LiLaBr5.4Cl0.6 single crystals with a size of Ф12 mm × 50 mm were successfully grown by the Bridgman method. Two different lattice positions of Ce3+ in the CLLBC crystal were identified by using spectral and decay kinetics, Raman spectra, X-ray photoelectron spectroscopy, refined XRD. The effects of cerium substitution amount on local structure, crystal structure, luminescence properties and the scintillation properties were systematically investigated. As the Ce3+ content increased, the light yield and energy resolution of CLLBC:Ce were first improved and then deteriorated. The Cs2LiLaBr5.4Cl0.6:2 mol% Ce crystal has a highest light yield and optimal energy resolution of 3.70 % under 137Cs@662 keV excitation.

Novel imaging technique for thermal neutrons using a fast optical camera

A novel imaging technique for thermal neutrons using a fast optical camera is presented. Thermal neutrons are reacted with 6Lithium to produce a pair of 2.73 MeV tritium and 2.05 MeV alpha particles, which in turn interact in a thin layer of LYSO crystal scintillator to produce a localized flash of light. These photons are directed by a pair of lenses to a micro-channel plate intensifier, and its output is connected to the optical camera, TPX3CAM. The results from the camera are reconstructed through a custom algorithm. Various cutting parameters were found through data analysis to eliminate the background, and they were shown effective in matching the simulated rate of the neutron source. The system is fast with 40 ns decay time and allows free-space light collection, both vastly enhances flexibility of neutron detection.

Preparation of Large Volume Solid Argon Crystal and Its Feasibility Test as a Scintillation Material

An important background to the liquid argon detectors is that they are caused by the diffusion of radioactive isotopes in a scintillator (liquid phase). This radioactive isotope is produced in argon’s surrounding devices, such as circulation pipelines and liquid argon containers. The solid argon as a scintillation material in the detector can inhibit the diffusion and drift of radioactive isotopes in a solid phase scintillator. Additionally, the structure of a solid argon detector is simple and reduces the total source of radioactive background. In the CDEX-300 detection system, solid argon could substitute for liquid argon as the veto detector, preventing radioactive isotopes drifting to the central main detector (HPGe detectors array) surface to reduce backgrounds. Therefore, solid argon has great potential in the experiments since it is especially helpful to get the lower background in a larger active volume than liquid argon required in those low background detection experiments. This work introduces the preparation process and device of the large volume transparent crystalline argon, the acquisition of scintillation light, and the pulse amplitude spectrum of 137Cs obtained from a prototype detector of transparent solid argon crystal. The results show that the scheme proposed in this study can successfully produce a large volume transparent crystalline argon detector, the scintillation light signals can be effectively obtained from the solid argon scintillator, and the corresponding pulse amplitude spectrum is given. This work indicates that it is feasible to develop a solid argon crystal scintillation detector by using our approach.

Erratum to: Crystal Scintillators for the Dark Matter Directionality Approach

Erratum to: Crystal Scintillators for the Dark Matter Directionality Approach

X-ray radioluminescent battery with near milliwatt output power using CsI:Tl single crystal scintillator

Low output power has long been the bottleneck of micro-radioisotope batteries as power supplies for the wireless sensor network, implantable medical equipment, and outer space exploration. Recently, x-ray radioluminescent batteries demonstrated the great potential to break the deadlock. In this work, we fabricated an x-ray radioluminescent battery with near milliwatt output power and demonstrated various potential applications. A 100% improvement on the conversion efficiency of 2.46% and the highest output power of 136.1 μW/cm2 were achieved when adopting a thallium doped cesium iodide (CsI:Tl) single-crystal scintillator in the battery. Subsequently, a 2 × 2 battery array was fabricated with a maximum output power of 466.9 μW and was used to power devices including micro-LEDs and a wireless sensor system with temperature monitoring. This demo system shows the feasibility of x-ray radioluminescent batteries as a long-lifetime micropower. The tremendous progress will draw broad attention on micro-nuclear batteries and inspire further exploration on the applications in the field of medical devices, space explorations, and Internet of Things.

Scintillator of Polycrystalline Perovskites for High‐Sensitivity Detection of Charged‐Particle Radiations

AbstractHerein, the first study on the scintillation properties of CsCu2X3 and Cs3Cu2X5 (where X: Cl−, Br−, I−) is presented, describing their charged particle‐induced luminescence involving electrons, protons, α‐particles, and heavy ions, as well as revealing their capabilities on the timing and spectroscopic evaluation of single‐particle events. The thin layers are prepared with a simple and cost‐effective deposition procedure, without the incorporation of external dopants, exploiting the intrinsic radiative recombination observed in low‐dimensional perovskites. The combined effect of the high binding energy and localized stability of self‐trapped excitons, large Stokes shift, defect tolerance, and the high excitation density along the particle track leads to the emergence of boosted scintillation pulses. The observations demonstrate the first use of inorganic thin‐film scintillators with optical pulse characteristics and light yield competitive with doped single crystal scintillators, while also providing improved structural and functional stability under extreme environmental conditions.

Photoluminescence and X-ray induced scintillation in Gd3+-modified fluorophosphate glasses doped with Ce3+

In this work, we report the fabrication of Gd3+-modified fluorophosphate glasses doped with Ce3+ with the new compositions 50NaPO3–20BaF2-(10-x)CaF2-20GdF3-xCeCl3, x = 0.3; 1; 3 and 5 mol% and their promising features as scintillators. The glasses present high molar density values (ρ ≅ 4 g cm−3), comparable to that of crystal scintillators, and distinguished optical properties. By UV–visible absorption, photoluminescence emission and excitation, excited state decay curves and radioluminescence measurements, the photophysical properties of the glasses were fully characterized. In addition, x-ray photoelectron spectroscopy (XPS) was employed to confirm the valence state of Ce ions. The results of emission spectra measured in the visible range upon UV excitation together with the excited state lifetime values of Ce3+ (5d → 4f transition) and Gd3+ (8S7/2→6Ij transition) clearly evidence energy transfer (ET) from the latter to the former ion. Though not quantified, the ET favors the fast decaying (τ = 24 ns) efficient emission of Ce3+ which makes the materials promising for fast response high energy radiation detectors. The response to X-ray excitation associated with the relatively high molar density of the glasses, indicate the promising application of these glasses for medical diagnosis where, in particular, a fast and intense response under high-energy radiation excitation is crucial.

Enhanced light output of scintillators by ZnO nanorod arrays

Scintillators are widely used in national security, industrial and medical fields. The light extraction efficiency of scintillator is quite low due to the total internal reflection. Therefore, enhancement the light output of scintillator is highly important. In this paper, we use ZnO nanorod (NR) arrays fabricated by a simple hydrothermal growth route to enhance the light extraction efficiency of Bi 4 Ge 3 O 12 (BGO) crystal scintillator. The light output results demonstrate that the light extraction efficiency of BGO with ZnO NRs is significantly enhanced, with an enhancement ratio of 4.1 and 3.5 at 510 nm wavelength under 266 nm laser and X-ray excitation, respectively. Our numerically calculated light transmissivity spectra and electric field intensity distributions of BGO with and without ZnO NRs by finite-difference time-domain (FDTD) simulation reveal that the ZnO NRs could reduce the total internal reflection and allow more light to be extracted, resulted in the enhancement of light output of BGO. • BGO with ZnO nanorods modifications yields a significant enhancement of light output. • The enhancement of light output in wide wavelength and angle ranges is demonstrated. • The mechanism of light extraction is revealed by numerical simulations.

The coordinate sensitive detector with high space and time resolution based on the MA-20 multianode PMT

The work is dedicated to the discussion of the possibility of creating a position-sensitive detector with high coordinate reconstruction. The paper presents the simulation results and the experimentally obtained data for a prototype detector based on the MA-20 multianode PMT [1] and a linear stack of scintillating crystal or plastic strips. The multianode position-sensitive PMT MA-20 has a semitransparent bi-alkaline photocathode with the size of the sensitive area of 10 × 200 mm2, 10 evaporated type bi-alkaline type dynodes of the same length, and 20 separated anodes. This PM is the invention of the authors. The maximum gain of the dynode system is 106. The stack of scintillating strips made of GSO (gadolinium orthosilicate) crystals with an element size of 3 × 10 × 50 mm3, of BGO (bismuth germanate) crystals with an element size of 5 × 15 × 40 mm3, and finally stack of strips made of a plastic scintillator with an element size of 5 × 10 × 200 mm3 were used for experimental measurement of a spatial resolution of the detector prototype. Space resolution was determined by the position of the center of gravity of charges of neighboring anodes [2]. As a source of radiation, the collimated 137Cs (γ 0.662 MeV) and 90Sr (β− 2.283 MeV) were used, the measured number of photoelectrons is 10–20 of one element of the stack, depending on the scintillating strip type. The use of a multi-anode photomultiplier in combination with the stack of crystal or plastic scintillators allows one to get a simple linear detector with high performance in spatial resolution and also with a low level of intrinsic noise in comparison, for example, with silicon PMT. A resolution simulation was performed for a system consisting of a one-dimensional stack of scintillation strips placed on the photocathode of a multi-anode PMT for different values of the strips width and the number of photoelectrons of one strip. The experimental dependences of the signal value versus position of optical fiber with a diameter of 1 mm on the photocathode of the 20 anodes PMT were also measured that allowed to specify the coordinate resolution for the described detector. As a result of processing the collected data, spatial resolution was obtained at the level of 1 mm. The obtained results are in good agreement with the simulation results.

Ag Nanocluster-Enhanced Scintillation Properties of Borophosphate Glasses Doped with CsPbBr3 Quantum Dots.

A novel and effective method to improve scintillation properties of glass-ceramics, such as intensity enhancement and decay-time shortening, is reported in this work. Compared with crystal scintillators, glass scintillators always have the problems of low efficiency and long decay; how to solve them has always been a scientific puzzle in the field of scintillation glass-ceramics. The plasma enhancement effect can be predicted to solve the above problems. Ag+ ions were diffused into glasses by ion exchange, and then Ag nanoparticles and CsPbBr3 quantum dots were formed by heat treatment. The structure of the CsPbBr3 perovskite consists of a series of shared corner PbBr6 octahedra with Cs ions occupying the cuboctahedral cavities. By using Ag and the plasma resonance effect, the photoluminescence intensity of CsPbBr3 quantum dot glasses was enhanced by 3 times, its radioluminescence intensity increased by 6.25 times, and its decay time was reduced by a factor of more than one. Moreover, the mechanism of photoluminescence and radioluminescence enhanced by Ag and plasma was discussed based on the experimental results and finite-difference time-domain method. We concluded that the increase in radioluminescence intensity was related to plasma enhancements and the energy exchange between Ag nanoclusters and CsPbBr3 quantum dots. Doping Ag is a valid means to improve the scintillation luminescence of CsPbBr3 quantum dot glasses, which can be applied in the field of scintillation.

Development of novel crystal scintillators for lunar surface science

The development of novel crystal scintillators for a lunar landed mission near future is reported. On that mission, we aim to assess the radiation dose, biological effect, water, and other resources on the lunar surface. To accomplish this, a Lunar Vehicle Radiation Dosimeter (LVRAD) made up of several radiation detectors has been proposed. New scintillation crystals are being developed for neutron and gamma measurements. Stilbene and undoped LaCl3 crystal were selected for fast neutron/gamma spectrometers. The mutual combination of organic and inorganic detectors benefits from direct fast neutron detection via 35Cl(n, p)35S reaction as well as the good gamma resolution of LaCl3 and the high detection efficiency of stilbene. LaCl3 crystals with the diameter of 38.1 mm were grown by a homemade modified Bridgman furnace. For epithermal neutron spectrometer, 6LiI:Ag crystal was selected due to its pulse shape discrimination capability and highest detection efficiency in terms of size for both thermal and epithermal neutron among scintillation materials. Enrich 6LiI was purified using the zone-refining technique. The crystal was then grown by the same Bridgman furnace.

Search for naturally occurring seaborgium with radiopure 116CdWO4 crystal scintillators

A detector containing two radiopure 116CdWO4 crystal scintillators with total mass of 1.2 kg was operated during 35324 h at the Gran Sasso Underground Laboratory (INFN, Italy) with the main aim to investigate double beta decay of 116Cd. As a by-product of the experiment, a new upper limit on atomic abundance of hypothetical naturally occurring long-lived seaborgium (eka-tungsten, Z = 106) in tungsten was set at 5.1 10−15 atom(Sg)/atom(W) with 90% C.L. (assuming the Sg half-life of 109 yr) by the analysis of the alpha decay events. This limit is better than those obtained with a ZnWO4 scintillator and in other types of experiments which used the accelerator mass spectrometry or searched for spontaneous fission of superheavy elements.

Multicolor Phosphate Glasses for Potential White LED Lighting and X‐Ray Detections

AbstractThough widely applied in light‐emitting diode (LED) lighting and X‐ray detection, respectively, rare‐earth ions doped phosphor and scintillating single crystals still face many challenges in practicalities, like aging of package material and difficulty to construct tiny array structure. Using phosphate glass as the host is quite beneficial for solving these problems while enabling distinguished luminescence. Therefore, Eu3+ and Tb3+ doped phosphate glasses which, respectively, show strong red/green emissions are researched. Superior thermal stabilities (78.69% and 89.35% emission intensities remain at 150 °C) and high internal quantum efficiencies (87.3% and 68.6%) are found to guarantee the excellent photoluminescence performances. The brilliant X‐ray excited luminescence properties are demonstrated by general 19.49% and 34.74% integrated emission intensities of that of commercial Bi4Ge3O12 single crystal scintillator with the change of X‐ray power. Meanwhile, Tb3+ doped scintillating fiber is drawn. Finally, excited by 380 nm LED, color manipulation and white light generation are achieved in LEDs with a structure of stacked emitting layers (mainly Eu3+ and Tb3+ doped phosphate glasses). Many of the as‐constructed white LED's performance parameters are much better than the commercial white LED. These results show that Eu3+ and Tb3+ doped phosphate glasses possess promising potential in LED lighting and X‐ray detections.

Photon interaction of molybdenum (Mo) based cesium tri-molybdate (Cs2Mo3O10) and disodium dimolybdate (Na2Mo2O7) single crystal scintillators

Both single crystals, molybdenum-based cesium tri-molybdate and disodium dimolybdate single crystal scintillators were investigated for gamma-rays interaction. The theoretical mass attenuation coefficients have been calculated by the WinXCom program. The 137Cs source was used in the experiment that was irradiated with eight different photon energies using the Compton scattering technique. The theoretical result shows that the mass attenuation coefficient of both scintillators depends on photon energy and decreases with increasing of photon energy. The molybdenum-based cesium tri-molybdate shows higher values of the mass attenuation coefficient than disodium dimolybdate scintillator all the energy range. The experimental result shows the same trend and are good agreement with theoretical. The values of molybdenum-based cesium tri-molybdate show decreased from 22.15 to 7.7 ( × 10−2 cm2/g) and the disodium dimolybdate scintillator shows decreased from 16.05 to 7.4 ( × 10−2 cm2/g). Moreover, the partial interaction, the effective atomic number, and the effective electron density were also investigated.

Crystal growth and scintillation properties of Tm3+ doped LaCl3 single crystal for radiation detection

Single crystal of Tm-doped LaCl3 (LaCl3:Tm3+) with the dimension of diameter 7 mm and length 55 mm was successfully grown using an in-house-developed Bridgman furnace. The grown crystal has the self-trapped exciton (STE) emission in the range of 300–500 nm along with the characteristic emissions corresponding to the 4f-4f transition of Tm3+ ions under X-ray excitation. The scintillation characterizations of the grown crystal were performed by pulse height spectra, scintillation decay time, as well as pulse shape discrimination studies under γ-ray and α-particle excitation sources. The LaCl3:Tm3+ crystal was found to have a high light yield (42,000 ± 4,200 ph/MeV) with 4.2% energy resolution under γ-rays excitation. Moreover, the pulse shape discrimination was studied using 137Cs and 241Am as the radiation sources with a good FOM value. The results conclude the LaCl3:Tm3+ single crystal to be a promising candidate for X-ray and γ-ray detection purposes.

Investigation on Rare Nuclear Processes in Hf Nuclides

In this work, a review of recent studies concerning rare nuclear processes in Hf isotopes is presented. In particular, the investigations using HP-Ge spectrometry and Hf-based crystal scintillators are focused; the potentiality and the results of the “source = detector” approach are underlined. In addition, a short introduction concerning the impact of such kind of research in the context of astroparticle and nuclear physics is pointed out. In particular, the study of α decay and double beta decay of 174Hf, 176Hf, 177Hf, 178Hf, 179Hf, 180Hf isotopes either to the ground state or to the lower bounded levels have been discussed. The observation of α decay of 174Hf isotope to the ground state with a T1/2=7.0(1.2)×1016 y is reported and discussed. No decay was detected for α decay of 174Hf isotope at the first excited level of daughter and of 176Hf, 177Hf, 178Hf, 179Hf, 180Hf isotopes either to the ground state or to the lower bounded levels. The T1/2 lower limits for these decays are at the level of 1016–1020 y. Nevertheless, the T1/2 lower limits for the transitions of 176Hf→172Yb (0+→0+) and 177Hf→173Yb (7/2−→5/2−) are near to the theoretical predictions, giving hope to their observation in the near future. All the other experimental limits (∼1016–1020 y) are absolutely far from the theoretical expectations. The experiments investigating the 2ϵ and ϵβ+ processes in 174Hf are also reported; the obtained half-life limits are set at the level of 1016–1018 y. Moreover, we estimate the T1/2 of 2ν2ϵ of 174Hf decay at the level of (0.3–6) × 1021 y (at now the related measured lower limit is 7.1×1016 y).

Luminescence of ZnWO4 crystals under X-ray excitation

Zinc tungstate crystal scintillator is an interesting detector material for double beta decay, dark matter, and rare alpha decay experiments. The luminescence under X-ray excitation in the temperature region from 85 K to 420 K was studied with five samples of ZnWO4 crystals developed by different methods: with a stoichiometric composition, and with excess of Zn or W. It is found that doping a ZnWO4 crystal with 0.2–0.3% Zn and W does not affect the luminescence properties of the material. A theoretical dependence of the sample luminescence intensity on the competing nonradiative recombination centers and traps is obtained. The main center of the recombination luminescence in a ZnWO4 crystal with a spectral maximum at 2.5 eV is the tungsten complex with a structural defect located next to it.

Convolutional neural network-based reconstruction for positronium annihilation localization

A novel hermetic detector composed of 200 bismuth germanium oxide crystal scintillators and 393 channel silicon photomultipliers has been developed for positronium (Ps) annihilation studies. This compact 4π detector is capable of simultaneously detecting γ-ray decay in all directions, enabling not only the study of visible and invisible exotic decay processes but also tumor localization in positron emission tomography for small animals. In this study, we investigate the use of a convolutional neural network (CNN) for the localization of Ps annihilation synonymous with tumor localization. Two-γ decay systems of the Ps annihilation from 22Na and 18F radioactive sources are simulated using a GEANT4 simulation. The simulated datasets are preprocessed by applying energy cutoffs. The spatial error in the XY plane from the CNN is compared to that from the classical weighted k-means algorithm centroiding, and the feasibility of CNN-based Ps annihilation reconstruction with tumor localization is discussed.

Investigation of the cryogenic scintillation of pure and doped sodium-iodine

We have studied the scintillation of pure and doped sodium iodide crystals handled in low humidity conditions under external α and γ excitation from room temperature down to 4 K. The light yield of pure sodium iodide was seen to increase at low temperatures by a factor 30 compared to room temperature, up to a maximum of 40 photons/keV under γ excitation at 60 K, stabilizing to 30 photons/keV at lower temperatures. Thallium doped sodium iodide fluctuates by 20% around the room temperature value, stabilizing at 40 photons/keV at low temperature. α/γ quenching factor stabilizes at roughly 0.7 for both materials beneath 50 K. Time constants of both materials slow greatly at low temperature, reaching tens of microseconds. Cryogenic applications of these materials are complexified by their mechanical fragility and hygroscopicity.