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Metal halide perovskite‐based high‐performance X‐ray scintillator is considered as one of the most favorable candidates applied in the fields of medicine, industry, and science. However, the current X‐ray scilltillators based on perovskites still suffer from the issue of poor stability, which impedes their further wide applications. Herein, a template assembled method to prepare large‐size, flexible, and stable CsPbBr3@Polymethyl methacrylate composite films in ambient conditions is developed and their detection performance is studied. The composite films can maintain 94% and 81% of the initial PL intensity after 2000 cycles bending and storing in water over 2520 h, respectively. In addition, the prepared scintillators exhibit not only a low detection limit of 40.1 nGyair s−1 and a high spatial resolution of 8.0 lp mm−1, but also an excellent tolerance against radiation (108 h). Thus, this simple but yet effective method would not doubt pave the way for further development of scintillators and might be well applicable to other metal halides. [ABSTRACT FROM AUTHOR]

A latent image of the target after the X‐ray irradiation induced via a 980 nm laser or thermal excitation provides great potentials for healthcare diagnostics and nondestructive inspection. Taking the advantage of X‐ray time‐lapse imaging, simplified facilities and visualized information can be achieved. However, information acquisition with higher resolution, combined with long‐term storage for the corresponding X‐ray images remains a challenge. Herein, Tb3+‐doped Ba2LaF7 nanocrystals (NCs) grown in situ and dispersed uniformly in an amorphous glass matrix is explored, which performs a fascinating X‐ray response for imaging with an impressive spatial resolution reaching 20.0 lp mm−1. Moreover, the as‐developed corresponding scintillators exhibit excellent optical storage capability upon X‐ray irradiation for the constructed deep traps, and a controllable release of the captured carriers induced by thermal disturbance, and 980 nm laser stimulation can be achieved. Notably, the imaging resolution is well preserved to be 20.0 lp mm−1 even recorded after 10 days. The as‐explored Ba2LaF7:Tb3+ NCs embedded within an amorphous matrix realize a feasible approach for a simplified X‐ray imaging system with high‐resolution information production. [ABSTRACT FROM AUTHOR]

Inorganic perovskite quantum dots CsPbX3 (X = Cl, Br, and I) has recently received extensive attention as a new promising class of X‐ray scintillators. However, relatively low light yield (LY) of CsPbX3 and strong optical scattering of the thick opaque scintillator film restrict their practical applications for high‐resolution X‐ray microscopic imaging. Here, the Ce3+ ion doped CsPbBr3 nanocrystals (NCs) with enhanced LY and stability are obtained and then the ultrathin (30 µm) and transparent scintillator films with high density are prepared by a suction filtration method. The small amount Ce3+ dopant greatly enhances the LY of CsPbBr3 NCs (about 33 000 photons per MeV), which is much higher than that of bare CsPbBr3 NCs. Moreover, the scintillator films made by these NCs with high density realize a high spatial resolution of 862 nm thanks to its thin and transparent feature, which is so far a record resolution for perovskite scintillator‐based X‐ray microscopic imaging. This strategy not only provides a simple way to increase the resolution down to nanoscale but also extends the application of as‐prepared CsPbBr3 scintillator for high resolution X‐ray microscopic imaging. [ABSTRACT FROM AUTHOR]

Low‐dimensional perovskite halides have shown a great potential as X‐ray detection materials because of efficient exciton emissions originating from strongly spatially localized charge carriers. Nonetheless, most of them have a scintillation yield far below their theoretical limits. Here, it is found that the harvesting efficiency of produced charge carriers can be significantly enhanced via a small amount of In+ doping in these highly localized structures. A bright and sensitive zero‐dimensional Cs3Cu2I5:In+ halide with efficient and tunable dual emission is reported. The radioluminescence emission of Cs3Cu2I5:In+ crystals under X‐ray excitation consists of a self‐trapped exciton emission at 460 nm and an In+‐related emission at 620 nm at room temperature. In+ doping enhances the photoluminescence quantum efficiency (PLQY) of Cs3Cu2I5 from 68.1% to 88.4%. Benefiting from the higher PLQY, Cs3Cu2I5:In+ can achieve an excellent X‐ray detection limit of 96.2 nGyair s−1, and a superior scintillation yield of 53 000 photons per MeV, which is comparable to commercial CsI:Tl single crystals. As a result, a remarkable X‐ray imaging resolution of 18 line pairs mm–1 is demonstrated, which is so far a record resolution for single crystal perovskite‐based flat‐panel detectors. These results highlight the importance of efficient harvesting of carriers (and excitons) in low‐dimensional perovskites for radiation detection applications. [ABSTRACT FROM AUTHOR]

Plastic scintillators (PS) allow design of portative lightweight devices for quantification of low‐activity radiation sources. We have recently suggested a new type of organic fluorophores based on triphenyl pyrazoline (PZ) derivatives with high fluorescence quantum yield showing high radioluminescence when combined with a polyvinyltoluene (PVT) matrix. In this publication we report on radioluminescence properties of the PZ−X family with various halogen substitution (X=F, Cl, Br, I), or having vinyl functional group (vPZ, X=vinyl). PS based on such fluorophores and PVT matrix can be prepared as bulk samples, micrometer size beads or cladding on optical fibers. Application of fluorophores with vinyl functional groups enabled their enhanced interaction with the matrix due to covalent bonding between the components. We demonstrate high performance of PZ−X fluorophores and especially vPZ fluorophore in fabrication of nanocomposites for detection of various types of radiation. Scintillators have enhanced gamma ray detection capabilities with an addition of triphenyl Bi, or Gd2O3 nanoparticles. High fluorescence quantum yield and luminosity of PZ fluorophores allows dramatical reduction of their content in PS systems. Mechanisms of energy transfer and conversion during scintillation process are discussed. Special consideration is given to enhancement of α/β and neutron/gamma (n/γ) pulse shape discrimination (PSD) function of the developed scintillators. [ABSTRACT FROM AUTHOR]

Scintillation detectors are commonly used for detecting radiation in various situations. NaI:Tl, CsI:Tl, BaF2 and CaF2:Eu are a few compounds that act as scintillation crystals for these detectors. The efficiency of a scintillation detector is one of the most important factors in improving the detector's performance. The present work shows that the efficiency of a scintillation detector can be increased by increasing the valence‐band electron density as a result of changing the crystal structure of the scintillating material. This will enhance the image quality of all imaging techniques based upon scintillation detectors. The results reveal that by changing the structure of the crystal from simple cubic to body‐centered cubic or face‐centered cubic the efficiency of the detector increases. The packing of more atoms into the crystal increases the number of atoms per unit cell and the density of the crystal. It is also observed that the increase in the number of atoms per unit cell and the density of the crystal will equally increase the efficiency of the detector. The additional atoms from changing the crystal structure contribute more valence‐band electrons, which allows for a higher chance of interaction between the incoming radiation and the valence‐band electrons to absorb more radiation energy. [ABSTRACT FROM AUTHOR]

A special group of luminescence materials are scintillators for thermal neutron detection. Due to the properties of neutrons (contrary to e.g. electrons or gamma photons), a different approach has to be utilized—the high content of atoms with the sufficient absorption cross‐section toward neutrons and lower material density are needed. This work pursues a basic study of LiSrBO3 and LiSr4(BO3)3 doped with cerium or europium—materials promising as thermal neutron scintillators. These borates exhibit promising properties such as the high content of lithium and boron, suitable density, and proper environment for luminescent ions. Radioluminescence of these ceramic borates doped with cerium and europium was examined and promising samples were further characterized by photoluminescence spectroscopy and radioluminescence and photoluminescence kinetics measurement. The radioluminescence study of these borates is published for the first time. Cerium‐doped borates, in particular, exhibit a very promising response to an X‐ray excitation. [ABSTRACT FROM AUTHOR]

In this work, we introduce an indirect X‐ray detector with organic photodiode (OPD). OPD, as a photodetector, is attractive due to its easy fabrication of even large area or flexible form factor. The top electrode of OPD is fabricated with a translucent organic‐metal‐organic (OMO) structure to absorb more light energy by the surface plasmonic effect at the organic‐metal interface. In addition, the new fabricated OPD has a microcavity effect, which is generated between the top and bottom electrodes, makes the broad absorption spectrum of CuPc (active layer) narrower, and tune to the narrow Gd2O2S scintillator emission wavelength. Through X‐ray experiments, the microcavity effect was shown to be useful and controllable by varying the thickness of C60 in the bulk heterojunction (BHJ) structure of the active layers which are composed of C60 and CuPc. [ABSTRACT FROM AUTHOR]

Scintillators are critical in medical imaging, non‐destructive security screening, and space exploration applications. However, it still remains a challenge to achieve large‐area and high‐transparency scintillators by a low‐cost and easy‐to‐implement way. Herein, a large transparent medium with a diameter over 10 cm is prepared via a facile melt‐quenching strategy using a stoichiometric mixture of ethyltriphenylphosphonium bromide (ETPBr) and MnBr2 as raw materials. Benefiting from the crystallization behavior of high‐efficiency green‐emitting (ETP)2MnBr4 nanocrystals hybridized with amorphous phase in the transparent wafer, the (ETP)2MnBr4‐based transparent medium as a scintillator evidences a high transparency (over 80%, ranging from 500 to 800 nm), a high light yield of ≈35 000 ± 2000 photon per MeV, a low detection limit of 103 nGy S–1, and a competitive spatial resolution of 13.4 lp mm–1 for X‐ray imaging. This work offers a distinctive simple and fast melt‐quenching methodology to fabricate (ETP)2MnBr4 metal halide X‐ray scintillator wafer with large‐area and shape flexibility, excellent transparency, and high scintillation performance for the medical or industrial X‐ray imaging application. [ABSTRACT FROM AUTHOR]

Background: Indirect detection flat‐panel detectors (FPDs) consisting of hydrogenated amorphous silicon (a‐Si:H) thin‐film transistors (TFTs) are a prevalent technology for digital x‐ray imaging. However, their performance is challenged in applications requiring low exposure levels, high spatial resolution, and high frame rate. Emerging FPD designs using metal oxide TFTs may offer potential performance improvements compared to FPDs based on a‐Si:H TFTs. Purpose: This work investigates the imaging performance of a new indium gallium zinc oxide (IGZO) TFT‐based detector in 2D fluoroscopy and 3D cone‐beam CT (CBCT). Methods: The new FPD consists of a sensor array combining IGZO TFTs with a‐Si:H photodiodes and a 0.7‐mm thick CsI:Tl scintillator. The FPD was implemented on an x‐ray imaging bench with system geometry emulating intraoperative CBCT. A conventional FPD with a‐Si:H TFTs and a 0.6‐mm thick CsI:Tl scintillator was similarly implemented as a basis of comparison. 2D imaging performance was characterized in terms of electronic noise, sensitivity, linearity, lag, spatial resolution (modulation transfer function, MTF), image noise (noise‐power spectrum, NPS), and detective quantum efficiency (DQE) with entrance air kerma (EAK) ranging from 0.3 to 1.2 μGy. 3D imaging performance was evaluated in terms of the 3D MTF and noise‐equivalent quanta (NEQ), soft‐tissue contrast‐to‐noise ratio (CNR), and image quality evident in anthropomorphic phantoms for a range of anatomical sites and dose, with weighted air kerma, Kw${K_w}$, ranging from 0.8 to 4.9 mGy. Results: The 2D imaging performance of the IGZO‐based FPD exhibited up to ∼1.7× lower electronic noise than the a‐Si:H FPD at matched pixel pitch. Furthermore, the IGZO FPD exhibited ∼27% increase in mid‐frequency DQE (1 mm−1) at matched pixel size and dose (EAK ≈ 1.0 μGy) and ∼11% increase after adjusting for differences in scintillator thickness. 2D spatial resolution was limited by the scintillator for each FPD. The IGZO‐based FPD demonstrated improved 3D NEQ at all spatial frequencies in both head (≥25% increase for all dose levels) and body (≥10% increase for Kw${K_w}$ ≤2 mGy) imaging scenarios. These characteristics translated to improved low‐contrast visualization in anthropomorphic phantoms, demonstrating ≥10% improvement in CNR and extension of the low‐dose range for which the detector is input‐quantum limited. Conclusion: The IGZO‐based FPD demonstrated improvements in electronic noise, image lag, and NEQ that translated to measurable improvements in 2D and 3D imaging performance compared to a conventional FPD based on a‐Si:H TFTs. The improvements are most beneficial for 2D or 3D imaging scenarios involving low‐dose and/or high‐frame rate. [ABSTRACT FROM AUTHOR]

Metal halide semiconductors have huge potential on X‐ray detection, due to their high atomic number, adjustable photoluminescence wavelength, superior stability, and simple fabrication process. Here, cesium lead halide nanocrystals (CsPbX3 NCs) are fabricated on paper substrate as scintillator screen for the first time. By means of all‐solution processed spray‐coating method with optimization of polymethyl methacrylate, large‐area (>600 cm2) and low‐cost (0.0975 dollar cm−2) flexible scintillator screens are obtained with high resolution (≈5 lp mm−1), low detection limit (2.97 μGy s−1), high light yield (≈30000 photons/MeV), and fast response speed (<15 ms). The screen can achieve high‐resolution X‐ray non‐distortion imaging for non‐planar objects and realize battery check and safety monitoring at a broad range of photon energy (10–160 keV). In addition, real‐time dose rates can be easily estimated through counting the luminous arcs of the designed visible indicator. More important, the screen shows remarkable tolerance to high‐dose X‐ray radiation (tolerance over 60 Gyair continuous radiation with only 3% performance degradation), water soaking (2000 h), and conventional storage (over 300 days without apparent deterioration under ambient conditions). Hence, this work may provide huge potential in the field of medical diagnosis, non‐planar detection, and safety monitoring in the future. [ABSTRACT FROM AUTHOR]

Zero‐dimensional Cs3Cu2Cl5 exhibits intriguing optical properties, which can meet the basic requirements of ideal scintillator application. Here, green emitter Cs3Cu2Cl5 nanosheets are successfully synthesized, and by doping with 2% potassium (K+), their photoluminescence quantum yield (70.23% to 81.39%), radioluminescence intensity, and stability are improved. Further experimental and theoretical studies point out that: (1) K+ brings the neighboring [Cu2Cl5]3− dimers groups closer, leading to lattice shrinkage and lower lattice constants; (2) such compact crystal structure results in stronger exciton–photon coupling and reduced phonon–electron coupling strength, which is beneficial to form self‐trapped excitons and enhanced luminescence; (3) lower lattice constants also induce decreased bandgap (2.58 to 2.51 eV) and increased Stokes shift (217 to 223 nm), for less self‐absorption and higher quantum efficiency. Finally, area‐controllable uniform flexible Cs3Cu2Cl5:2%K+–polystyrene film is successfully achieved with excellent X‐ray sensibility. Such flexible film shows low cost (2.8223 $/g), broadband response (20–160 keV), and high spatial resolution (5 lp mm−1) that is comparable to commercial CsI:Tl wafer. Moreover, it fits well with nonplanar surfaces for high‐quality medical and industrial flexible images applications. It is believed that this work can provide a viable tactic to enhance X‐ray detection in metal halide scintillators. [ABSTRACT FROM AUTHOR]

X‐ray imaging technology covers a wide range of applications in the medical, industrial, and scientific research fields. Highly sensitive, flexible, and cost‐effective scintillation screens are of great importance for X‐ray imaging applications. In this paper, manganese (II) activated 2D butylammonium lead bromide perovskite, namely BA2PbBr4:Mn (II), is demonstrated as a highly efficient and low‐cost X‐ray scintillator. The appropriate amount of Mn (II) dopant can act as an activator for achieving the optimization of luminescence performance through efficient energy transfer. This produces a large Stokes shift thus almost eliminates the effect of self‐absorption. As a result, the optimal BA2PbBr4:10% Mn (II) perovskite scintillator demonstrates an ultrahigh sensitivity for X‐ray, with a high X‐ray scintillation light yield of up to 85 ± 5 photons keV−1 and low detection limits of 16 nGyair s−1 at the signal‐to‐noise ratio (SNR) of 3. Well‐resolved X‐ray images of several planar and nonplanar objects are obtained using a flexible large‐dimensional scintillation screen fabricated by blade‐coating strategy, featuring high spatial resolution of 10.7 lp mm−1 at modulation transfer function = 0.2. These results indicate that Mn (II) activated BA2PbBr4 perovskite with remarkable scintillation performances can serve as a highly promising scintillator for commercial high‐resolution X‐ray imaging applications. [ABSTRACT FROM AUTHOR]

Scintillators, as the core materials for X‐ray imaging, have received great attention in radiation detection, security inspection, and biomedical applications. However, the current single crystal and thin film scintillators have encountered several issues, such as high cost, insufficient stability, and uneven distribution, which undoubtedly limit the development of high‐quality X‐ray imaging. Herein, the Y3Al5O12:Ce3+ (YAG:Ce3+) transparent ceramics (TCs), which presented a high transmittance of 82% and a steady‐state light yield of 24 600 photons MeV−1, are prepared by the vacuum solid‐state reactive sintering method. The fabricated YAG:Ce3+ TCs exhibit X‐ray imaging with an excellent spatial resolution (≈34.7 lp mm−1). Moreover, because of the structural stability of YAG:Ce3+ TCs, long‐term stable work under X‐ray irradiation is realized successfully. This work indicates that the TC scintillators provide a new opportunity for the development of high‐quality X‐ray imaging. [ABSTRACT FROM AUTHOR]

Cu halide materials with low electronic dimension show great scintillation properties with high photoluminescence quantum yield (PLQY) and large Stokes shift, which can result in reabsorption‐free scintillators. However, there is still a need for a large‐scalable method to fabricate large amount of scintillation powder and large‐size scintillation films. In this regard, a high scintillation yield Cu3Cu2I5−PDMS flexible film utilizing ball‐milled Cu3Cu2I5 powder is developed. The ball‐milled Cu3Cu2I5 powder shows a high PLQY of 74.5%, narrow emission peak of 80 nm and good ambient stability, demonstrating the potential of ball‐milling method for large‐scale scintillator production. Furthermore, the Cu3Cu2I5−PDMS film shows even high PLQY exceeding 90%, which may be ascribed to the passivation effect of PDMS resulting in a little longer carrier lifetime. The flexible Cu3Cu2I5−PDMS film can further deliver high spatial resolution of 6.8 lp mm−1@0.2 MTF in X‐ray imaging and good stability under steady X‐ray illumination. This work demonstrates that the ball‐milling method could be an effective approach for large‐scale fabrication of low electronic dimensional scintillation materials. [ABSTRACT FROM AUTHOR]

Purpose: Key factors in FLASH treatments are the ultra‐high dose rate (UHDR) and the time structure of the beam delivery. Measurement of the time structure in pencil beam scanning (PBS) proton FLASH treatments is challenging for many types of detectors since high temporal resolution is needed. In this study, a fast scintillator detector system was developed and used to measure the individual spot durations as well as the time when the beam moves between two positions (transition duration) during PBS proton FLASH and UHDR treatments. The spot durations were compared with machine log‐file recordings. Methods: A detector system based on inorganic scintillating crystals was developed. The system consisted of four detector probes made of a sub‐millimeter ZnSe:O crystal that was coupled via an optical fiber to an optical reader with 50 kHz sampling rate. The detector system was used in two experiments, both performed with a PBS proton beam with 250 MeV beam energy and 215 nA requested nozzle beam current. The sampling rate enabled multiple measurements during each spot delivery and during the beam transition between spots. First, the detector was tested in a phantom experiment, where a total of 305 scan sequences were delivered to the four detectors. The number of spots delivered without beam interruption in a single scan sequence ranged from one to 35. The spot duration and transition duration were measured for each individual spot. Secondly, the detector system was used in vivo in preclinical experiments with FLASH irradiation of mouse legs placed in the entrance plateau of the beam. A single detector was placed 1 cm downstream of the irradiated mouse leg. The mouse dose ranged from 30.5 to 44.2 Gy and the field consisted of 35 spots. The spot durations as well as the mean dose rate (field dose divided by the measured field duration) for each mouse were determined using the detector and then compared with the corresponding log files. Results: The phantom experiment showed that the logged total duration of an uninterrupted spot sequence was consistently shorter than the measured duration with a difference of −0.252 ms (95% confidence interval: [‐0.255, −0.249 ms]). This corresponded to 0.05%–0.07% of the spot sequence duration in the mice experiments. For individual spots, the mean ± 1SD difference between logged and measured spot duration was −0.39 ± 0.05 ms for the first spot in a sequence, 0.13 ± 0.04 ms for the last spot in a sequence, and −0.0017 ± 0.09 ms for the intermediate spots in a sequence. The measured spot transition durations were 0.20 ± 0.04 ms (5.1 mm horizontal steps) and 0.50 ± 0.04 ms (5.0 mm vertical steps). For the mouse experiments, the mean dose rate calculated from the measured field duration was 84.1–92.5 Gy/s. It agreed with log files with a root mean square difference of 0.02 Gy/s. Conclusions: Fiber‐coupled scintillator detectors were designed with sufficient temporal resolution to measure the spot and transition duration during PBS proton UHDR deliveries. Their small volume makes them feasible for in vivo use in preclinical FLASH studies. The logged spot durations were in excellent agreement with measurements but showed small systematic errors in the logged duration for the first and last spot in a sequence. [ABSTRACT FROM AUTHOR]

Purpose: Detector arrays and profile‐scans have widely replaced film‐measurements for quality assurance (QA) on linear accelerators. Film is still used for relative output factor (ROF) measurements, positioning, and dose‐profile verification for annual Leksell Gamma Knife (LGK) QA. This study shows that small‐field active detector measurements can be performed in the easily accessed clinical mode and that they are an effective replacement to time‐consuming and exacting film measurements. Methods: Beam profiles and positioning scans for 4‐mm, 8‐mm, and 16‐mm‐collimated fields were collected along the x‐, y‐, and z‐axes. The Exradin W2‐scintillator and the PTW microdiamond‐detector were placed in custom inserts centered in the Elekta solid‐water phantom for these scans. GafChromic EBT3‐film was irradiated with single uniformly collimated exposures as the clinical‐standard reference, using the same solid‐water phantom for profile tests and the Elekta film holder for radiation focal point (RFP)/patient‐positioning system (PPS) coincidence. All experimental data were compared to the tissue‐maximum‐ratio‐based (TMR10) dose calculation. Results: The detector‐measured beam profiles and film‐based profiles showed excellent agreement with TMR10‐predicted full‐width, half‐maximum (FWHM) values. Absolute differences between the measured FWHM and FWHM from the treatment‐planning system were on average 0.13 mm, 0.08 mm, and 0.04 mm for film, microdiamond, and scintillator, respectively. The coincidence between the RFP and the PPS was measured to be ≤0.5 mm with microdiamond, ≤0.41 mm with the W2‐1 × 1 scintillator, and ≤0.22 mm using the film‐technique. Conclusions: Small‐volume field detectors, used in conjunction with a clinically available phantom, an electrometer with data‐logging, and treatment plans created in clinical mode offer an efficient and viable alternative for film‐based profile tests. Position verification can be accurately performed when CBCT‐imaging is available to correct for residual detector‐position uncertainty. Scans are easily set up within the treatment‐planning‐system and, when coupled with an automated analysis, can provide accurate measurements within minutes. [ABSTRACT FROM AUTHOR]

The increasing demand for radiation detection in many applications has led to demanding requirements for scintillators. Realizing low‐dose, pollution‐free, and reliable X‐ray detection has become a key technical challenge. Here, a triplet‐enhanced lanthanide radioluminescence (RL) material Ga3+/Tb3+ metallacrowns (Tb‐1) is reported. This Tb‐1 crystal emits bright green luminescence under ultraviolet light or X‐ray excitation, and the emission intensity is 286 and 242 times that of Tb3+ in inorganic salt, respectively. Tb‐1 crystal is further passivated by trioctylphosphine oxide (TOPO), and the enhanced RL intensity is equivalent to that of commercial Tl‐doped cesium iodide scintillator. In addition, RL of Tb‐1–TOPO has an extremely narrow full width at half maximum and an excellent linear response to the X‐ray dose rate. The detection limit is calculated to be 0.146 μGy s−1, which is 38 times lower than typical medical imaging doses. Triplet‐enhanced lanthanide RL provides new ideas for replacing scintillators that require high temperature synthesis processes such as inorganic phosphors and ceramics, and provides a new alternative scintillator material for flexible X‐ray monitoring, bioimaging, radiotherapy, and other applications. [ABSTRACT FROM AUTHOR]

Europium-doped lutetium oxide (Lu2O3:Eu) single crystal is grown by vertical Bridgman method for the first time. Correlated measurements of X-ray diffraction, X-ray fluorescence spectra, optical transmittance, photoluminescence excitation, photoluminescence (PL), PL decay, and X-ray excited luminescence (XEL) spectra are performed. The transmittance of about 80% above 300 nm indicates that the crystal is of good optical quality. By measuring actual Eu3+ concentration, the effective segregation coefficient of Eu3+ in the Lu2O3:Eu crystal is calculated to be 0.75. In the PL spectrum, the dominant emission peaks at 612 and 630 nm originate from the 5D0→7F2 transitions of Eu3+ in C2 site. It is worth mentioning that several emission peaks between 575 and 605 nm mainly ascribe to the transitions of different 5D0 levels to the split 7F1 levels of Eu(C2) or Eu(C3i). PL decay spectra indicate the decay time of 612 nm emission can be determined about 1.0 ms. The decay curve of 582.6 nm emission can be fitted into triple components, and the 5.3 and 1.4 ms components are attributed to Eu3+(C3i) and Eu3+(C2), respectively. The XEL strongest emission of Lu2O3:Eu sample is around 612 nm with a bright red luminescence that matches silicon photodetectors sensitivity. [ABSTRACT FROM AUTHOR]

Scintillators, which can convert high‐energy ionizing radiation into visible light, have been serving as the core component in radiation detectors for more than a century of history. To address the increasing application demands along with the concern on nuclear security, various strategies have been proposed to develop a next‐generation scintillator with a high performance in past decades, among which the novel approach via structure control has received great interest recently due to its high feasibility and efficiency. Herein, the concept of "structure engineering" is proposed for the exploration of this type of scintillators. Via internal or external structure design with size ranging from micro size to macro size, this promising strategy cannot only improve scintillator performance, typically radiation stopping power and light yield, but also extend its functionality for specific applications such as radiation imaging and therapy, opening up a new range of material candidates. The research and development of various types of structured scintillators are reviewed. The current state‐of‐the‐art progresses on structure design, fabrication techniques, and the corresponding applications are discussed. Furthermore, an outlook focusing on the current challenges and future development is proposed. [ABSTRACT FROM AUTHOR]

Halide perovskites are an emerging scintillator material for X‐ray imaging. High‐quality X‐ray imaging generally requires high spatial resolution and long operation lifetime, especially for targeted objects with irregular shapes. Herein, a perovskite "polymer–ceramics" scintillator, in which the halide perovskite nanocrystals are grown inside a pre‐solidified polymer structure with high viscosity (6 × 1012 cP), is designed to construct flexible and refreshable X‐ray imaging. A nucleation inhibition strategy is proposed to prevent the agglomeration and Ostwald ripening of perovskite crystals during the subsequent precipitation process, enabling a high‐quality polymer–ceramics scintillator with high transparency. This scintillator‐based detector achieves a detection limit of 120 nGy s–1 and a spatial resolution of 12.5 lp mm–1. Interestingly, due to the anchoring effect of the exfoliated atoms provided by the polymer matrix, the scintillator film can be refreshed after a long duration (≥3 h) and high dose (8 mGy s–1) irradiation. More importantly, this inherent characteristic overcomes the long operation lifetime issue of perovskites‐based scintillators. Hence, the authors' exploration of the polymer–ceramics scintillator paves the way for the development of flexible and durable perovskite scintillators that can be produced at a low operation cost. [ABSTRACT FROM AUTHOR]

Lithium iodides are very efficient single‐crystal scintillators for thermal neutron detection. Doping with silver, as activator ions, has shown to improve its limitation of discriminating gamma background by introducing pulse shape discrimination ability. To improve the scintillation performance, single crystals of LiI:Ag, codoped with different concentration of Sr ions, are grown and characterized in details. A systematic investigation of radioluminescence, thermoluminescence, and scintillation properties along with the decay kinetics provides better understanding about the role of defect structure in scintillation mechanism. The extra charge, provided by Sr2+ ions, is found to alter the defect structure with relative reduction of the contribution from the deeper trap centers in comparison with the shallow traps. Consequently, it leads to a significant improvement of light yield quenching under higher excitation density of charged particle irradiation. The 0.1% Sr codoped crystals provide a better discrimination ability of neutron and gamma radiations for simultaneous detection. [ABSTRACT FROM AUTHOR]

Purpose: Long‐axial field‐of‐view (FOV) positron emission tomography (PET) scanners have gained a lot of interest in the recent years. Such scanners provide increased sensitivity and enable unique imaging opportunities that were not previously feasible. Benefiting from the high sensitivity of a long‐axial FOV PET scanner, we studied a computed tomography (CT)–less reconstruction algorithm for the Siemens Biograph Vision Quadra with an axial FOV of 106 cm. Methods: In this work, the background radiation from radioisotope lutetium‐176 in the scintillators was used to create an initial estimate of the attenuation maps. Then, joint activity and attenuation reconstruction algorithms were used to create an improved attenuation map of the object. The final attenuation maps were then used to reconstruct quantitative PET images, which were compared against CT‐based PET images. The proposed method was evaluated on data from three patients who underwent a flurodeoxyglucouse PET scan. Results: Segmentation of the PET images of the three studied patients showed an average quantitative error of 6.5%–8.3% across all studied organs when using attenuation maps from maximum likelihood estimation of attenuation and activity and 5.3%–6.6% when using attenuation maps from maximum likelihood estimation of activity and attenuation correction coefficients. Conclusions: Benefiting from the background radiation of lutetium‐based scintillators, a quantitative CT‐less PET imaging technique was evaluated in this work. [ABSTRACT FROM AUTHOR]

Purpose: To fabricate a 1D stemless plastic scintillation detector (SPSD) array using organic photodiodes and to use the detector to measure small field profiles and output factors. Methods: An organic photodiode array was fabricated by spin coating a mixture of P3HT and PCBM organic semiconductors onto an ITO‐coated glass substrate and depositing aluminum top contacts. Four bulk scintillators of various dimensions were placed on top of the photodiode array. A fifth scintillator was used that had been segmented by laser etching and the septa filled with black paint. Each detector array was first calibrated using a reference field of 95 cm SSD, 5 cm depth, and 10 × 10 cm2 field size for a 6 MV photon beam. After calibration, profiles were measured for three small field sizes: 0.5 × 0.5 cm2, 1 × 1 cm2, and 2 × 2 cm2. Using the central pixel of the array, output factors were measured for field sizes of 0.5 × 0.5 cm2 to 25 × 25 cm2. Small field profiles were compared to film measurements and output factors compared to ion chamber measurements. Results: The segmented scintillator measured profiles that were in good agreement with film for all three field sizes. Output factors agreed to within 1.2% of ion chamber over the field size range of 1 × 1 cm2 to 25 × 25 cm2. At 0.5 × 0.5 cm2 the segmented scintillator underestimated the output factor compared to film and a microDiamond detector. Bulk scintillators failed to produce a good agreement with film for measured profiles and deviations from ion chamber for output factors were apparent at field sizes below 5 × 5 cm2. In comparison to a bulk scintillator of dimensions 5 × 5 × 0.5 cm3 the etched scintillator saw a reduction of 5.1, 7.1, and 10.5 times the signal for field sizes of 0.5 × 0.5 cm2, 1 × 1 cm2, and 2 × 2 cm2, respectively. The reduction of signal comes from reduced cross‐talk that was present in all of the bulk scintillator geometries to various degrees. Conclusion: A 1D SPSD array was demonstrated with various scintillator designs. The etched scintillator array demonstrated excellent small field profile measurements when compared to film and output factors (down to 1 × 1 cm2 field size) when compared to micro ion chamber and diamond detector measurements. [ABSTRACT FROM AUTHOR]

In this paper, it is recently discovered that mixed‐anion Cl‐Br halide scintillator K2LaClxBr5−x:Ce (x = 0, 1, 2, 3, 4, 5) has promising performance. The mixed crystal polycrystalline materials are synthesized by high‐temperature solid‐phase method, and transparent cylindrical crystals of K2LaClxBr5−x:Ce are grown successfully by the vertical Bridgman technique. The crystals are measured by powder X‐ray diffraction, X‐ray‐induced luminescence spectra, optical transmittance, photoluminescence spectrum, photoluminescence decay time, and pulse height spectrum. Under the UV and X‐ray excitation, all of the crystal samples have the typical Ce3+ 5d1→2F5/2 and 5d1→2F7/2 double peaks, emission centered between 350 and 400 nm. The photoluminescence decay time of the K2LaClxBr5−x:Ce crystal is about 30 ns under the UV excitation. The energy resolution of the crystal is generally less than 10%. As the proportion of Br‐ ions increases, the luminescence intensity is enhanced, the photoluminescence decay speed increases, and energy resolution of these crystals is optimized. The simplicity of the growth of small‐sized crystals is promising for expanding the growth process to larger sizes. [ABSTRACT FROM AUTHOR]

There are few reports about purely organic phosphorescence scintillators, and the relationship between molecular structures and radioluminescence in organic scintillators is still unclear. Here, we presented isomerism strategy to study the effect of molecular structures on radioluminescence. The isomers can achieve phosphorescence efficiency of up to 22.8 % by ultraviolet irradiation. Under X‐ray irradiation, both m‐BA and p‐BA show excellent radioluminescence, while o‐BA has almost no radioluminescence. Through experimental and theoretical investigation, we found that radioluminescence was not only affected by non‐radiation in emissive process, but also highly depended on the material conductivity caused by the different molecular packing. This study not only allows us to clearly understand the relationship between the molecular structures and radioluminescence, but also provides a guidance to rationally design new organic scintillators. [ABSTRACT FROM AUTHOR]

Scintillators, converting the absorbed high‐energy X‐ray photons into to visible ones, have been used in fields as medical diagnostics, radiation dosimetry, and security inspection. Commercial bulk scintillators generally suffer from time‐consuming production, high‐cost operation, and deteriorated performance especially exposed to humidity. Here, in situ precipitated CdS quantum dots (QDs) within the transparent glass matrix are achieved feasibly. The CdS QDs glass‐ceramic (GC) is explored to be a superior scintillator with an outstanding weather resistance. A profound radioluminescence behavior and long‐term (≈3600 s) stability under X‐ray irradiation of the scintillator with the dose rate of 1 mGyair s−1 are demonstrated. Moreover, the indirect X‐ray imaging of the CdS GC reaches excellent resolution of 10 lp mm−1. Furthermore, the damaged scintillator under a long‐term cumulative dose up to 288 Gyair is recovered via a subsequent thermal treatment. Herein, the explored scintillator of CdS GC executes a promising cost‐effective X‐ray imaging for long‐term operation of the corresponding optoelectronic devices. [ABSTRACT FROM AUTHOR]

The luminescent property of 2D perovskite materials promotes their applications in light emitting diodes, phosphor powders, and scintillators. Recently, an interesting extrinsic low‐energy broadband luminescence is hotly investigated. However, the understanding of such emissions is still at the early stage. In this study, based on a modified solvent evaporation method, centimeter‐size (BDA)PbI4 (BDA = NH3C4H8NH32+) single crystals are grown which, besides the band–band emission, show a large Stokes‐shifted broadband luminescence. We find such emission can be effectively excited by sub‐gap photons and conclude defects‐induced shallow traps are the corresponding luminescence centers. Density functional theory (DFT) calculations indicate that in‐plane iodine vacancies can introduce shallow electron traps in the band gap and give rise to the broadband emission. [ABSTRACT FROM AUTHOR]

A scintillation screen with ultrahigh spatial resolution, fast decay time, and high stability is the key to commercial application. Herein, a pixelated‐structure scintillation screen of CsPbBr3 nanocrystal arrays based on anodized aluminum oxide (AAO) is reported, and its scintillation properties for X‐ray imaging are explored. It is of note that ultrahigh spatial resolution (2 µm), fast photoluminescence decay time (9 ns), and high stability (>42 d) are successfully achieved by the pixelated CsPbBr3‐AAO arrays scintillation screen. Considering the decent scintillation properties and high stability, one has reason to assume that the pixelated CsPbBr3‐AAO arrays scintillation screen may find an application as a new X‐ray scintillation screen. [ABSTRACT FROM AUTHOR]

Scintillators are widely utilized as X‐ray imaging detectors. Pixelated scintillator films with optical‐waveguide‐effect are preferred to realize high‐resolution X‐ray imaging. However, it remains a great challenge to rapidly fabricate high‐resolution pixelated scintillator film. Herein, a new strategy is developed to solve the problem by embedding metal halide scintillators into an anodic aluminum oxide (AAO) via a facile hot‐pressing method. Cs3Cu2I5 is selected as the prototype to fabricate pixelated scintillator films with targeted thickness, denoted as Cs3Cu2I5−AAO. The light confinement effect provided by AAO is validated by finite‐difference time‐domain simulations. In particular, the as‐prepared Cs3Cu2I5−AAO film demonstrates higher spatial resolution (10.4 lp mm−1 at modulation transfer function = 0.2), higher UV and X‐ray imaging performances compared to the homogeneous counterpart and commercialized terbium‐doped gadolinium oxysulfide. These results can inspire further research on the design of nanostructured metal halide perovskites for high‐resolution X‐ray imaging. [ABSTRACT FROM AUTHOR]

Both semiconductors and scintillators have their own advantages in direct and indirect X‐ray detection, respectively. However, they are also limited by their intrinsic properties and detection mechanisms. Here, a low‐cost and large‐area flat X‐ray detector is reported by combining a cesium silver bismuth bromide (Cs2AgBiBr6) perovskite semiconductor with a ethylenebis‐triphenylphosphonium manganese (II) bromide ((C38H34P2)MnBr4) scintillator through fast tableting processes. Cs2AgBiBr6 and (C38H34P2)MnBr4 can attenuate the X‐ray photons to induce charge carriers that are collected through the continuous Cs2AgBiBr6 grains. (C38H34P2)MnBr4 blocks the Cs2AgBiBr6 ions migration paths at the grain boundaries to reduce the device dark current/noise and improves the working stability. Most charges generated by (C38H34P2)MnBr4 are transferred to the adjacent Cs2AgBiBr6, and recombined charges radiate light through scintillation, which will be further absorbed by the surrounding Cs2AgBiBr6 perovskite, and further induce collectable charges for indirect X‐ray detection, avoiding the unwanted light scattering, self‐absorption, or afterglow effects of scintillators. The hybrid X‐ray detector displays a high sensitivity of 114 µC Gyair−1 cm−2 to 120 keVp hard X‐rays with a lowest detectable dose rate of 0.2 μGyair s−1, showing 75 times lower detection limit compared to (C38H34P2)MnBr4 scintillator, which provides a new path for X‐ray flat‐panel design. [ABSTRACT FROM AUTHOR]

Ce‐doped yttrium aluminum garnet (YAG) is among the efficient rare‐earth garnet scintillators and phosphors. Herein, a computational and experimental study of complex F‐type defect centers formed in YAG by doping with cerium and carbon is addressed. The formation energies determined by ab initio calculations of different defects and atomic chemical potentials in YAG:Ce,C are discussed in O‐poor and O‐rich conditions corresponding to the crystal growth under Ar+CO reducing atmosphere, and postgrowth annealing in air, respectively. It is shown that as‐grown crystals contain numerous positively charged defects responsible for F‐type center formation, whereas mainly negative‐charged defects are remained after the annealing in air. The negatively charged defects located nearby Ce luminescence center occupying Y site may stabilize cerium in the tetravalent state and promote a hole transport to this luminescence center. This describes a high scintillation efficiency of Ce,C‐doped garnets. Furthermore, YAG:C and YAG:Ce,C with a high carbon concentration, in addition to luminescence peaked at 400 ns ascribed to F+‐type centers, possess a fast luminescence peaked around 650 nm that may be attributed to the complex defect centers. These unveiled features of the luminescence process in rare‐earth garnets may contribute to the development of efficient luminescence materials. [ABSTRACT FROM AUTHOR]

Purpose: Detectors for positron emission tomography (PET) typically use two types of scintillation crystals, pixelated or monolithic. A variant of these types of scintillators are the so‐called semi‐monolithic crystals. They consist of a monolithic crystal segmented in one direction in pieces called slabs. These scintillators have the potential to successfully combine the benefits of pixelated and monolithic configurations, providing good timing and spatial resolutions as well as the capacity to decode the depth of interaction (DOI) information. In this work, the timing performance of a detector based on semi‐monolithic crystals was studied in depth. The energy response was also evaluated. Methods: The semi‐monolithic detector consists of 1 × 24 LYSO slabs of 25.4 × 12 × 0.95 mm3 each. The bottom surface of the slabs is coupled to an array of 8 × 8 silicon photomultipliers (SiPMs) of 3 × 3 mm2 active area, 50 μm cell size and 3.2 mm pitch. The 64 output signals were independently readout by the TOFPET2 ASIC. In order to achieve the best coincidence time resolution (CTR), four different time walk corrections were tested. Additional work investigated the best method of combining the timestamps belonging to the same event. Results: The resolvability of the slabs in the measured flood maps improves with the thickness of a light guide placed in between the scintillators and photosensors. The energy resolution does not change significantly with values as good as 13.7%. Regarding the CTR, values of 335.8, 363, 369.8, and 402.5 ps have been obtained for the whole detector for no light guide, 0.5, 1.0, and 1.5 mm thickness light guide cases, respectively. These values further improve to 276.1, 302.6, 305.6 and 336.2 ps, respectively, when energy‐weighted averaging of timestamps is applied. Conclusions: We have shown both an excellent timing resolution and good energy resolution for a PET detector based on semi‐monolithic crystals. The use of light guides of different thicknesses does not significantly affect the energy resolution of the whole detector, but the timing capabilities slightly worsen with the increasing thickness of the light guide. [ABSTRACT FROM AUTHOR]

Inorganic scintillating crystals can be modelled as continua with microstructure. For rigid and isothermal crystals, the evolution of charge carriers becomes in this way described by a reaction‐diffusion‐drift equation coupled with the Poisson equation of electrostatic. Here, we give a survey of the available existence and asymptotic decays results for the resulting boundary value problem, the latter being a direct estimate of the scintillation decay time. We also show how to recover various approximated models which encompass also the two most used phenomenological models for scintillators, namely, the kinetic and diffusive ones. Also for these cases, we show, whenever it is possible, which existence and asymptotic decays estimate results are known to date. [ABSTRACT FROM AUTHOR]

Ionospheric scintillations caused by equatorial plasma bubbles (EPBs) can seriously affect various high technology systems based on Global Navigation Satellite System (GNSS) signals at equatorial and low latitudes. A reliable prediction of ionospheric scintillation occurrence is critical to relieve the effect. Using the long‐term ground‐based GNSS receiver and ionosonde data collected in the Brazilian longitude sector during 2012–2020, an ionospheric strong scintillation prediction model based on the gradient boosting algorithms extreme gradient boosting (XGBoost), light gradient boosting machine (LightGBM), and CatBoost is created and tested. It is for the first time that the XGBoost, LightGBM, and CatBoost are utilized to predict the day‐to‐day occurrence of regional ionospheric scintillation during post‐sunset hours. The relative importance of different parameters affecting EPB/scintillation occurrence for building the prediction model is examined. A comparison of daily scintillation occurrence from the modeled and observed results during 2014 (solar maximum) and 2020 (solar minimum) shows that the gradient boosting algorithms are effective for predicting strong scintillations over low latitude, with a prediction accuracy of ∼85%. The results suggest that the trained model with input of total electron content, equatorial F layer peak height and critical frequency before sunset could be well employed to predict the occurrence/nonoccurrence of intense scintillations over low latitude after sunset on a daily basis. Plain Language Summary: Ionospheric scintillation is the rapid fluctuation of radio signals traversing through ionospheric irregularities. Severe scintillation can cause loss of lock for the systems using Global Navigation Satellite System signals. The dependences of scintillation on seasonal, solar and geomagnetic activities have been widely studied, but its day‐to‐day variability and prediction still remain a challenge. The relationship between scintillation occurrences and a variety of factors is complex. The machine learning algorithm could handle nonlinear problems and thus uncover the implicit correlations between multiple factors. The gradient boosting, which is a type of machine learning technique, has been demonstrated to be effective in many fields, such as in the field of intrusion detection. Here, we employ the gradient boosting algorithm, together with long‐term observations in the Brazilian longitude sector to investigate if the day‐to‐day occurrence of low latitude ionospheric scintillation could be predicted. The results show that with limited input parameters, the prediction accuracy for scintillation occurrence on a daily basis reach ∼85%, suggesting that the gradient boosting algorithms are effective for predicting strong scintillations over low latitude. This opens a possibility for scintillation forecasting with acceptable accuracy under the conditions without physical model and powerful computing capability. Key Points: A model for predicting low latitude scintillation occurrence after sunset is created based on gradient boosting algorithmThe model with input of total electron content, equatorial hmF2 and foF2 before sunset, can well capture strong scintillation occurrence after sunsetThe gradient boosting algorithm is suggested to be effective in predicting low latitude strong scintillation occurrence on a daily basis [ABSTRACT FROM AUTHOR]

The correlation of mechanical properties of polymer materials with those of their molecular constituents is the foundation for their holistic comprehension and eventually for improved material designs and syntheses. Over the last decade, optical force probes (OFPs) were developed, shedding light on various unique mechanical behaviors of materials. The properties of polymers are diverse, ranging from soft hydrogels to ultra‐tough composites, from purely elastic rubbers to viscous colloidal solutions, and from transparent glasses to super black dyed coatings. Only very recently, researchers started to develop tailored OFP solutions that account for such material requirements in energy (both light and force), in time, and in their spatially detectable resolution. We here highlight notable recent examples and identify future challenges in this emergent field. [ABSTRACT FROM AUTHOR]

0D halide perovskite Cs3Cu2I5‐based nanocrystals and bulk crystals are proven to be sensitive and efficient scintillators for X‐ray and γ‐ray detection. Herein, undoped and Tl‐doped Cs3Cu2I5 microcrystalline films are synthesized by a thermal evaporation method. Both films crystallize into a Pnma space group of orthorhombic crystal lattice with preferred (004) growth orientation. The undoped Cs3Cu2I5 thin film shows a sole emission peaking at 440 nm associated with the self‐trapped exciton emission. Doping of Tl+ ions introduces another emission that peaks at 520 nm. The scintillation efficiency of both undoped and Tl‐doped Cs3Cu2I5 thin films is about one‐third of that of CsI:Tl thin film with the same size and thickness. Within the first 5 s after X‐ray cutoff, afterglow signals of both the undoped and Tl‐doped Cs3Cu2I5 thin films are over one order of magnitude lower than that of CsI:Tl thin film. [ABSTRACT FROM AUTHOR]

Purpose: High‐dose rate (HDR) and pulsed‐dose rate (PDR) brachytherapy would benefit from an independent treatment verification system to monitor treatment delivery and to detect errors in real time. This paper characterizes and provides an uncertainty budget for a detector based on a fiber‐coupled high‐Z inorganic scintillator capable of performing time‐resolved in vivo dosimetry during HDR and PDR brachytherapy. Method: The detector was composed of a detector probe and an optical reader. The detector probe consisted of either a 0.5 × 0.4 × 0.4 mm3 (HDR) or a 1.0 × 0.4 × 0.4 mm3 (PDR) cuboid ZnSe:O crystal glued onto an optical‐fiber cable. The outer diameter of the detector probes was 1 mm, and fit inside standard brachytherapy catheters. The signal from the detector probe was read out at 20 Hz by a photodiode and a data acquisition device inside the optical reader. In order to construct an uncertainty budget for the detector, six characteristics were determined: (1) temperature dependence of the detector probe, (2) energy dependence as a function of the probe‐to‐source position in 2D (determined with 2 mm resolution using a robotic arm), (3) the signal‐to‐noise ratio (SNR), (4) short‐term stability over 8 h, and (5) long‐term stability of three optical readers and four probes used for in vivo monitoring in HDR and PDR treatments over 21 months (196 treatments and 189 detector calibrations, and (6) dose‐rate dependence. Results: The total uncertainty of the detector at a 20 mm probe‐to‐source distance was < 5.1% and < 5.8% for the HDR and PDR versions, respectively. Regarding the above characteristics, (1) the sensitivity of the detector decreased by an average of 1.4%/°C for detector probe temperatures varying from 22 to 37°C; (2) the energy dependence of the detector was nonlinear and depended on both probe‐to‐source distance and the angle between the probe and the brachytherapy source; (3) the median SNRs were 187 and 34 at a 20 mm probe‐to‐source distance for the HDR and PDR versions, respectively (corresponding median source activities of 4.8 and 0.56 Ci, respectively); (4) the detector response varied by 0.6% in 11 identical irradiations over 8 h; (5) the sensitivity of the four detector probes decreased systematically by 0–1.2%/100 Gy of dose delivered to the probes, and random fluctuations of 4.8% in the sensitivity were observed for the three probes used in PDR and 1.9% for the probe used in HDR; and (6) the detector response was linear with dose rate. Conclusion: ZnSe:O detectors can be used effectively for in vivo dosimetry and with high accuracy for HDR and PDR brachytherapy applications. [ABSTRACT FROM AUTHOR]

Purpose: To present an x‐ray tube system capable of in vitro ultrahigh dose‐rate (UHDR) irradiation of small < 0.3 mm samples and to characterize it by means of a plastic scintillation detector (PSD). Methods and materials: A conventional x‐ray tube was modified for the delivery of short UHDR irradiations. A beam shutter system with a sample holder was designed and installed in a close proximity of an x‐ray tube window to enable <1 s irradiations at UHDR. The dosimetry was performed with a small 0.5‐mm long 0.5‐mm in diameter PSD irradiated with 80, 100, and 120 kVp beams and beam currents of 1–37.5 mA. The PSD signal was recorded at frame rates of 20 and 50 fps for shutter exposure between 100 and 1125 ms. Irradiation reproducibility was studied with the PSD. The x‐ray tube irradiation setup was modeled with Monte Carlo (MC) and dose on a surface of a phantom was also measured with films. The effect of dose delivery uncertainty to 300‐μm spheroids due to positioning and spheroid size was evaluated. Results: MC simulations showed good agreement with PSD measurements acquired at both frame rates of 20 and 50 fps in terms of beam temporal profile. PSD‐measured dose exhibited excellent linearity as a function of instantaneous dose rate from 3.1 to 118.0 Gy/s as well as shutter exposure time from 100 and 1125 ms for all investigated beam energies. PSD absorbed dose for the 80, 100, and 120 kVp beams agreed with MC simulations to within 5%. The total delivered doses ranged from 0.4 Gy for a 1‐mA, 80 kVp beam, and 100 ms shutter exposure to 166.9 Gy for a 37.5‐mA, 80 kVp beam, and a 1125 ms exposure. PSD irradiation reproducibility was < 0.5%. Simulated and measured dose fall off agreed and it was steep along the axis of the shutter slit (1%/0.1 mm) and with depth (2%/0.1 mm at 1‐mm depth). Spheroid positioning uncertainty of 300 μm resulted in dose difference of < 3% for x and y shifts but up to 7% uncertainty for a z‐shift parallel to the beam axis. A 16% difference in spheroid size resulted in <5% dose difference in spheroid absorbed dose. Conclusions: We have presented a cost‐effective x‐ray tube‐based system with a beam shutter designed for in vitro UHDR delivery and reaching dose rates of up to 118.0 Gy/s. The described shutter system can be easily implemented at other institutions, which might enable new researchers to investigate the radiobiology of UHDR irradiations in vitro. [ABSTRACT FROM AUTHOR]

Nowadays, the development of X‐ray imaging has promoted the demand for new‐type scintillators, among which low‐toxic manganese(II) complexes have attracted burgeoning research interest. Herein, a highly stable manganese(II) complex with peculiar five‐coordinated modes is reported, which exhibits strong yellow emission peaked at 583 nm originating from d‐d transition of Mn2+ with high photoluminescence quantum yield (PLQY) up to 93%. The five‐coordinated manganese(II) complex has been rarely reported so far which is an innovative spot in the field of photofunctional metal complex. Thanks to the high PLQY and relatively large stokes shift, the manganese(II) complex yields bright yellow emission under low‐dose X‐ray irradiation and delivers excellent linear response to X‐ray, highlighting its suitability for X‐ray contrast imaging. Based on this, highly resolved X‐ray imaging is successfully achieved that can meet the requirements of many application scenarios. In addition, this manganese(II) complex demonstrates excellent radiation hardness, humidity resistance, and heat stability, indicating the application potential of scintillators in harsh environments. This research not only provides guidance for the design and fabrication of highly luminescent manganese(II)‐based complexes, but also demonstrates the potential of manganese(II)‐based complexes as scintillators for X‐ray imaging technology. [ABSTRACT FROM AUTHOR]

Strong sporadic E (Es) irregularities over China are investigated based on high‐temporal‐resolution total electron content (TEC) derived from two crossed chains of Beidou geostationary satellite (BD‐GEO) TEC receivers along 110°E and 23°N, respectively. The high resolution rate of TEC index (HR‐ROTI) calculated at an interval of 30 s, is proposed to characterize small‐scale strong Es irregularity structures. Based on the HR‐ROTI measurements and the typical drift velocity of Es 60 m/s, the scale sizes of strong Es irregularity structures were revealed to be mainly ∼7 km. The structures were mostly quasi‐periodically separated with distances of 7–16 km. Through a further statistical analysis of strong Es irregularity structures along the two chains, it was found that the Es irregularity structures predominantly occur during local summer at middle and low latitudes, with the occurrence rate peaking at ∼30°N. On average approximately 2–5 small‐scale strong Es irregularity structures may be embedded in one larger‐scale structure. Unlike the equatorial and low‐latitude F‐region irregularities which cause scintillations under most conditions, the strong Es irregularity characterized by HR‐ROTI caused scintillation with relatively low occurrence rates of 37% and 12% at middle and low latitudes, respectively. Plain Language Summary: The ionospheric sporadic E (Es) layer and associated irregularities were traditionally investigated and characterized based on observations from ground‐based radars, for example, ionosondes and very high frequency radars, which usually suffer from a small spatial distribution. Ever since strong Es were revealed to be detectable by ionospheric total electron content (TEC) measurements from ground‐based Global Navigation Satellite Systems (GNSS) receivers, the morphology of large‐scale strong Es structures has been studied over different regions. However, the occurrences of strong Es irregularity structures, with scale sizes down to a few kilometers along the same latitude/longitude are not clear. Whereas GNSS observations in a dense network provide a valuable dataset for Es investigation, the most commonly used measurements such as the L‐band amplitude scintillation index and the well‐defined rate of TEC index (ROTI) are for F‐region irregularities. No index specialized in identifying strong Es irregularities has been proposed. In this regard, the high resolution ROTI (HR‐ROTI) calculated at 30‐s interval is proposed to characterize Es irregularity structures with scale sizes down to a few kilometers. Based on the HR‐ROTI measured along two crossed GNSS receiver chains, the occurrences of strong Es irregularities along a specific longitude/latitude over China are investigated, which exhibited distinct features over different latitude regions. Key Points: High Resolution Rate‐Of‐TEC Index (HR‐ROTI) is introduced to characterize strong Es irregularity structures with scale sizes down to a few kilometersStrong Es over China tends to occur more frequently around 30°N, and be embedded with approximately 2–5 small‐scale structures in one larger structureThe occurrence rates of amplitude scintillations under strong Es (with HR‐ROTI > 0.1 TECU/min) at middle and low latitudes are 37% and 12%, respectively [ABSTRACT FROM AUTHOR]

We propose a new technique to infer the horizontal speed of ionospheric irregularity at high latitudes from the refractive components of the global positioning system (GPS) L1 (1575.42 MHz) and L2 (1227.60 MHz) carrier phases using only a single ground‐based receiver that can log measurements at 50–100 Hz. The test data at Jang Bogo Station (geographic: 74.6°S and 164.2°E; geomagnetic: 77.2°S) in Antarctica and at Sachs Harbor (geographic: 71.9°N and 234.7°E; geomagnetic: 75.6°N) in the Arctic were analyzed for a one‐year period in 2019. The results were compared with data from ground‐based radar observations, the Vertical Incidence Pulsed Ionospheric Radar (VIPIR) in Antarctica and the Canadian Advanced Digital Ionosonde (CADI) in the Arctic, which measures the ion drift velocity at the apex. Although it is difficult to directly compare GPS and radar measurements due to the steep gradient of fast plasma motion in narrow regions at high latitudes, the probability density of the ionospheric irregularity speeds from the two different instruments were consistent with the correlation coefficients of 0.81 and 0.85 in the Southern and Northern hemispheres. Plain Language Summary: Radio waves, such as global positioning system (GPS) signals, can be disrupted as they traverse through the ionosphere. Irregular ionospheric electron densities with sizes smaller than the Fresnel radius mainly cause amplitude fluctuations, while large ionospheric irregularities of several kilometers lead to phase variations. In particular, diffraction, which is a stochastic variation with a high frequency greater than the Fresnel frequency, is called ionospheric scintillation. Refraction, that is, deterministic variations with low frequencies that are frequently misinterpreted as ionospheric scintillation can be removed using a bandpass filter rather than a high‐pass filter when the ionospheric plasma speed is known. Conversely, the Fresnel frequency can be inferred by locating the refractive components at high latitudes, where the plasma moves very quickly. In this study, the Fresnel frequency was converted into ionospheric irregularity horizontal speed. It can also be used to investigate ongoing problems such as the "phase without amplitude" scintillation phenomenon. Key Points: Ionospheric Fresnel frequency can be inferred from high resolution dual‐frequency measurements using a single GPS receiver at high latitudesHorizontal speed of an ionospheric irregularity is determined from inferred Fresnel frequencyProbability densities of inferred ionospheric irregularity speeds from GPS and radar are statistically compared in both hemispheres [ABSTRACT FROM AUTHOR]

Patterning graphene into strips with nanometer‐scale widths, i.e. graphene nanoribbons, is an effective approach to customize different properties of the material. Narrowing a large sheet of graphene via conventional top‐down approaches meets the intrinsic resolution limitations of lithography. Process residuals as a result of using sticky polymeric templates may also influence the performance of the eventual device, in addition to altering the chemistry of the ribbons. Here, a facile approach for pattering graphene nanoribbons via an inert metallic mask lithography is reported. The masks are prepared by the microtomy of metallic thin films, embedded within polymeric scaffolds and precisely deposited on top of a graphene monolayer. The inertness of the masks allows the precise narrowing of the graphene under different etching environments, permitting the control over the edge chemistry. Remarkably a mild ultrasonication is enough to remove the mask entirely at the end of the process, without leaving any residue. For electronic applications, however, partial removal of the metallic mask using a laser power, in situ realizes a pair of electrodes, hence avoiding the often difficult issue of electrode alignment. The method proposes a simple and direct approach towards the design of chemically tailored, scalable, and electrically connected graphene nanoribbons. [ABSTRACT FROM AUTHOR]

Lead halide perovskites (LHP) are rapidly emerging as efficient, low‐cost, solution‐processable scintillators for radiation detection. Carrier trapping is arguably the most critical limitation to the scintillation performance. Nonetheless, no clear picture of the trapping and detrapping mechanisms to/from shallow and deep trap states involved in the scintillation process has been reported to date, as well as on the role of the material dimensionality. Here, this issue is addressed by performing, for the first time, a comprehensive study using radioluminescence and photoluminescence measurements side‐by‐side to thermally‐stimulated luminescence (TSL) and afterglow experiments on CsPbBr3 with increasing dimensionality, namely nanocubes, nanowires, nanosheets, and bulk crystals. All systems are found to be affected by shallow defects resulting in delayed intragap emission following detrapping via a‐thermal tunneling. TSL further reveals the existence of additional temperature‐activated detrapping pathways from deeper trap states, whose effect grows with the material dimensionality, becoming the dominant process in bulk crystals. These results highlight that, compared to massive solids where the suppression of both deep and shallow defects is critical, low dimensional nanostructures are more promising active materials for LHP scintillators, provided that their integration in functional devices meets efficient surface engineering. [ABSTRACT FROM AUTHOR]

Purpose: To test the measurement technique of the three‐dimensional (3D) dose distribution measured image by capturing the scintillation light generated using a plastic scintillator and a scintillating screen. Methods: Our imaging system constituted a column shaped plastic scintillator covered by a Gd2O2S:Tb scintillating screen, a conical mirror and a cooled CCD camera. The scintillator was irradiated with 6 MV photon beams. Meanwhile, the irradiated plan was prepared for the static field plans, two‐field plan (2F plan) and the conformal arc plan (CA plan). The 2F plan contained 16 mm2 and 10 mm2 fields irradiated from gantry angles of 0° and 25°, respectively. The gantry was rotated counterclockwise from 45° to 315° for the CA plan. The field size was then obtained as 10 mm2. A Monte Carlo simulation was performed in the experimental geometry to obtain the calculated 3D dose distribution as the reference data. Dose response was acquired by comparing between the reference and the measurement. The dose rate dependence was verified by irradiating the same MU value at different dose rates ranging from 100 to 600 MU/min. Deconvolution processing was applied to the measured images for the correction of light blurring. The measured 3D dose distribution was reconstructed from each measured image. Gamma analysis was performed to these 3D dose distributions. The gamma criteria were 3% for the dose difference, 2 mm for the distance‐to‐agreement and 10% for the threshold. Results: Dose response for the scintillation light was linear. The variation in the light intensity for the dose rate ranging from 100 to 600 MU/min was less than 0.5%, while our system presents dose rate independence. For the 3D dose measurement, blurring of light through deconvolution processing worked well. The 3D gamma passing rate (3D GPR) for the 10 × 10 mm2, 16 × 16 mm2, and 20 × 20 mm2 fields were observed to be 99.3%, 98.8%, and 97.8%, respectively. Reproducibility of measurement was verified. The 3D GPR results for the 2F plan and the CA plan were 99.7% and 100%, respectively. Conclusions: We developed a plastic scintillation dosimeter and demonstrated that our system concept can act as a suitable technique for measuring the 3D dose distribution from the gamma results. In the future, we will attempt to measure the 4D dose distribution for clinical volumetric modulated arc radiation therapy (VMAT)‐SBRTplans. [ABSTRACT FROM AUTHOR]

The high‐profile candidacy of low‐dimensional metal‐halide single crystals as promising light emitters originates from the intriguing emission properties (e.g., extremely broad luminescence spectra, large Stokes shift, high color rendition), which have enabled the recent great achievements on their application in lighting, artificial illumination, and scintillators. Among the family of low‐dimensional metal‐halide single crystals, zero‐dimensional (0D) materials have been featured in the lowest dimensionality, and as a consequence, strongest quantum confinement, softest lattice, and strongest electron–phonon coupling have been further translated into near‐unity photoluminescence (PL) efficiency with broadband emission. However, as far as it is known, 0D structures are significantly underexplored. Herein, an overview is provided on recent advances of 0D metal‐halide single crystals, with a focus on comprehensive understanding and insightful perspectives behind the photophysical mechanism. Additionally, the challenges and future opportunities currently faced by 0D bulk metal halides are discussed in order to provide a roadmap for the future development of novel materials with versatile optical properties suited for practical applications. [ABSTRACT FROM AUTHOR]

Purpose: Designing and optimizing scintillator‐based gamma detector using Monte Carlo simulation is of great importance in nuclear medicine and high energy physics. In scintillation detectors, understanding the light transport in the scintillator and the light collection by the photodetector plays a crucial role in achieving high performance. Thus, accurately modeling them is critical. Methods: In previous works, we developed a model to compute crystal reflectance from the crystal 3D surface measurement and store it in look‐up tables to be used in the Monte Carlo simulation software GATE. The relative light output comparison showed excellent agreement between simulations and experiments for both polished and rough surfaces in several configurations, that is, without and with reflector. However, when comparing them at the irradiation depth closest to the photodetector face, rough crystals with a reflector overestimated the predicted light output. Investigating the cause of this overestimation, we optimized the LUT algorithm to improve the reflectance computation accuracy, especially for rough surfaces. However, optical Monte Carlo simulations carried out with these newly generated LUTs still overestimate the light output. Based on previous observations, one probable cause is the erroneous assumption of perfect couplings between the reflector and crystal and between the crystal and photodetector, which likely results in an important overestimation of the light output compared to experimental values. In practice, several factors could degrade it. Here, we investigated possible suboptimal optical experimental configurations that could lead to a degraded light collection when using Teflon or ESR reflectors coupled to the crystal with air or grease. We generated look‐up tables with a mixture of air and grease and showed the effect of three possible sources of light loss: the presence of a small gap between the crystal and the reflector edges close to the photodetector face, the infiltration of grease in the crystal–reflector coupling, and the presence of inhomogeneities in the photodetector–crystal interface. Results: The strongest effect is linked to the presence of a small gap of grease between the edges of the reflector material and the crystal (light loss of 10%–12% for 0.2 mm gap). The optical grease infiltrating the crystal–reflector air coupling decreases the light output, depending on the infiltration's extent and the amount of grease infiltrated. Five percent of air in the crystal–photodetector coupling can cause a light output decrease of 2% to 4%. The individual and combined effect of these advanced models can explain the discrepancy of the relative light output obtained with ESR in simulations and experiments. With Teflon, the study indicates that the light output loss strongly depends on the reflectance deterioration caused by grease absorption. Conclusions: Our results indicate that when studying scintillation detector performance with different finishes, performing simulations in ideal coupling conditions can lead to light output overestimation. To perform an accurate light output comparison and ultimately have a reliable detector performance estimation, all potential sources of practical limitations must be carefully considered. To broadly enable high‐fidelity modeling, we developed an interface for users to compute their own LUTs, using their surface, scintillator, and reflector characteristics. [ABSTRACT FROM AUTHOR]

Single crystal scintillators have become one of the most common materials used in technologies that use radiation detectors. Unfortunately, as technology demands improved detectors, research into better single crystal scintillators has nearly reached its limit. Ceramics provide many benefits over single crystal scintillators and have emerged as a promising new production process. Recent research into ceramic scintillators has mostly dealt with oxides as they are relatively easy to handle and are typically non‐hygroscopic. Among single crystal scintillators, a trend has emerged indicating that the addition of halide ions into the crystal structure improves the light yield and energy resolution of the scintillation material but also tends to make the material hygroscopic and in some cases intrinsically radioactive. Little research is devoted to the investigation of undoped halide ceramic scintillators. Transparent halide Cs2HfCl6 ceramics are developed by hot uniaxial pressing, and the scintillation properties are compared to that of its single crystal counterpart. The energy resolution of the ceramic is found to be 6.4% at 662 keV. The initial results indicate that ceramic scintillators are a viable alternative and a promising new direction in scintillator material technology. [ABSTRACT FROM AUTHOR]

A limitation to the use of Global Navigation Satellite System (GNSS) for precise and real‐time services is introduced by irregularities in the ionospheric plasma density. An EISCAT UHF/ESR experiment was conducted to characterize the effect of electron density irregularities on temporal fluctuations in TEC along directions transverse to GPS ray paths in the high latitudes ionosphere. Two representative case studies are described: Enhancements in temporal TEC fluctuations originating (a) in the auroral ionosphere following auroral particle precipitation and (b) in the polar ionosphere following the drift of a polar patch as well as particle precipitation. The results indicate that the origin of enhancements in TEC fluctuations is due to the propagation through large‐to‐medium scale irregularities (i.e., ranging from few kilometres in the E region to few tens of kilometres in the F region) and occurring over spatial distances of up to approximately 400km in the E region and up to approximately 800km in the F region with a patchy distribution. Furthermore, the results indicate that enhancements in TEC fluctuations produced by polar plasma patches and particle precipitation occur over similar temporal scales, thus explaining the overall observation of higher phase scintillation indices in the high‐latitude ionosphere. The similarity in the temporal scales over which enhancements in TEC fluctuations occur in the presence of both particle precipitation and plasma patches suggests an intrinsic limitation in the monitoring and tracking of plasma patches through ground GNSS observations. Key Points: Measurements indicate that the observed auroral and polar irregularities were distributed over large distancesPolar plasma patches and auroral particle precipitation enhance temporal fluctuations in Global Positioning System (GPS) Total Electron ContentEnhanced fluctuations in Total Electron Content occur over similar temporal scales for plasma patches and particle precipitation [ABSTRACT FROM AUTHOR]

Hybrid manganese halide has attracted much attention in the field of environment friendly ferroelectric and photo‐responsive multifunctional materials. Here, the highly efficient photoluminescent inorganic framework MnBr42− is utilized to conceive and synthesize a series of hybrid manganese bromide compounds [RQ]2MnBr4 by introducing precisely designed quasi‐spherical cations [RQ]+ (R = H, Me, Et, FEt, Q = quinuclidine). The accurate and effective modification of cations not only achieves the satisfactory ferroelectricity, but also enhances the photoluminescence quantum yield from 38.7% to 83.65%. Moreover, [FEtQ]2MnBr4 shows a highly efficient X‐ray scintillator performance, including a large range of linear response to X‐ray dose rate from 0.3 to 414.2 μGyair s−1, a high light yield of 34 438 photons per MeV, and a low detection limit of 258 nGyair s−1. This work provides an efficient strategy for the preparation of hybrid manganese halide ferroelectrics with highly efficient light‐emission and X‐ray detection. [ABSTRACT FROM AUTHOR]