Search

In this paper, an overview of wide-bandgap (WBG) semiconductors for radiation detection applications is given. The recent advancements in the fabrication of high-quality wafers have enabled remarkable WBG semiconductor device applications. The most common 4H-SiC, GaN, and β-Ga2O3 devices used for radiation detection are described. The 4H-SiC and GaN devices have already achieved exceptional results in the detection of alpha particles and neutrons, thermal neutrons in particular. While β-Ga2O3 devices have not yet reached the same level of technological maturity (compared to 4H-SiC and GaN), their current achievements for X-ray detection indicate great potential and promising prospects for future applications. [ABSTRACT FROM AUTHOR]

Hybrid pixel detectors have become indispensable at synchrotron and X-ray free-electron laser facilities thanks to their large dynamic range, high frame rate, low noise, and large area. However, at energies below 3 keV, the detector performance is often limited because of the poor quantum efficiency of the sensor and the difficulty in achieving single-photon resolution due to the low signal-to-noise ratio. In this paper, we address the quantum efficiency of silicon sensors by refining the design of the entrance window, mainly by passivating the silicon surface and optimizing the dopant profile of the n+ region. We present the measurement of the quantum efficiency in the soft X-ray energy range for silicon sensors with several process variations in the fabrication of planar sensors with thin entrance windows. The quantum efficiency for 250 eV photons is increased from almost 0.5% for a standard sensor to up to 62% as a consequence of these developments, comparable to the quantum efficiency of backside-illuminated scientific CMOS sensors. Finally, we discuss the influence of the various process parameters on quantum efficiency and present a strategy for further improvement. [ABSTRACT FROM AUTHOR]

Kaonic atom X-ray spectroscopy is a consolidated technique for investigations on the physics of strong kaon–nucleus/nucleon interaction. Several experiments have been conducted regarding the measurement of soft X-ray emission (<20 keV) from light kaonic atoms (hydrogen, deuterium, and helium). Currently, there have been new research activities within the framework of the SIDDHARTA-2 experiment and EXCALIBUR proposal focusing on performing precise and accurate measurements of hard X-rays (>20 keV) from intermediate kaonic atoms (carbon, aluminum, and sulfur). In this context, we investigated cadmium–zinc–telluride (CdZnTe or CZT) detectors, which have recently demonstrated high-resolution capabilities for hard X-ray and gamma-ray detection. A demonstrator prototype based on a new cadmium–zinc–telluride quasi-hemispherical detector and custom digital pulse processing electronics was developed. The detector covered a detection area of 1 cm2 with a single readout channel and interesting room-temperature performance with energy resolution of 4.4% (2.6 keV), 3% (3.7 keV), and 1.4% (9.3 keV) FWHM at 59.5, 122.1, and 662 keV, respectively. The results from X-ray measurements at the DAΦNE collider at the INFN National Laboratories of Frascati (Italy) are also presented with particular attention to the effects and rejection of electromagnetic and hadronic background. [ABSTRACT FROM AUTHOR]

Lead halide perovskites have made remarkable progress in the field of radiation detection owing to the excellent and unique optoelectronic properties. However, the instability and the toxicity of lead‐based perovskites have greatly hindered its practical applications. Alternatively, lead‐free perovskites with high stability and environmental friendliness thus have fascinated significant research attention for direct X‐ray detection. In this review, the current research progress of X‐ray detectors based on lead‐free halide perovskites is focused. First, the synthesis methods of lead‐free perovskites including single crystals and films are discussed. In addition, the properties of these materials and the detectors, which can provide a better understanding and designing satisfactory devices are also presented. Finally, the challenge and outlook for developing high‐performance lead‐free perovskite X‐ray detectors are also provided. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDCs) are demonstrated to be appealing semiconductors for optoelectronic applications, thanks to their remarkable properties in the ultraviolet-visible spectral range. Interestingly, TMDCs have not yet been characterized when exposed to x rays, although they would be ideal candidates for optoelectronic applications in this spectral range. They benefit from the high cross section of the constituent heavy atoms, while keeping the absorption very low, due to the ultrathin structure of the film. This encourages the development of photodetectors based on TMDCs for several applications dealing with x rays, such as radioprotection, medical treatments, and diagnosis. Given the atomic thickness of TMDCs, they can be expected to perform well at low dose measurements with minimal perturbation of the radiation beam, which is required for in vivo applications. In this paper, the use of TMDCs as active materials for direct x-ray detection is demonstrated, using a photodetector based on a MoS2 monolayer (1L-MoS2). The detector shows a response to x rays in the range of 101–102 keV, at dose rates as low as fractions of mGy/s. The sensitivity of 1L-MoS2 reaches values in the range of 108–109µC Gy−1 cm−3, overcoming the values reported for most of the organic and inorganic materials. To improve the x-ray photoresponse even further, the 1L-MoS2 was coupled with a polymeric film integrating a scintillator based on terbium-doped gadolinium oxysulfide (Gd2O2S:Tb). The resulting signal was three times larger, enabled by the indirect x ray to visible photoconversion mechanism. This paper might pave the way toward the production of ultrathin real-time dosimeters for in vivo applications. [ABSTRACT FROM AUTHOR]

X-ray detectors have numerous applications in medical imaging, industrial inspection, and crystal structure analysis. Gallium oxide (Ga2O3) shows potential as a material for high-performance X-ray detectors due to its wide bandgap, relatively high mass attenuation coefficient, and resistance to radiation damage. In this study, we present Sn-doped Ga2O3 microwire detectors for solar-blind and X-ray detection. The developed detectors exhibit a switching ratio of 1.66 × 102 under X-ray irradiation and can operate stably from room temperature to 623 K, which is one of the highest reported operating temperatures for Ga2O3 X-ray detectors to date. These findings offer a promising new direction for the design of Ga2O3-based X-ray detectors. [ABSTRACT FROM AUTHOR]

X-ray detection has widespread applications in medical diagnosis, non-destructive industrial radiography and safety inspection, and especially, medical diagnosis realized by medical X-ray detectors is presenting an increasing demand. Perovskite materials are excellent candidates for high-energy radiation detection based on their promising material properties such as excellent carrier transport capability and high effective atomic number. In this review paper, we introduce X-ray detectors using all kinds of halide perovskite materials along with various crystal structures and discuss their device performance in detail. Single-crystal perovskite was first fabricated as an active material for X-ray detectors, having excellent performance under X-ray illumination due to its superior photoelectric properties of X-ray attenuation with μm thickness. The X-ray detector based on inorganic perovskite shows good environmental stability and high X-ray sensitivity. Owing to anisotropic carrier transport capability, two-dimensional layered perovskites with a preferred orientation parallel to the substrate can effectively suppress the dark current of the device despite poor light response to X-rays, resulting in lower sensitivity for the device. Double perovskite applied for X-ray detectors shows better attenuation of X-rays due to the introduction of high-atomic-numbered elements. Additionally, its stable crystal structure can effectively lower the dark current of X-ray detectors. Environmentally friendly lead-free perovskite exhibits potential application in X-ray detectors by virtue of its high attenuation of X-rays. In the last section, we specifically introduce the up-scaling process technology for fabricating large-area and thick perovskite films for X-ray detectors, which is critical for the commercialization and mass production of perovskite-based X-ray detectors. [ABSTRACT FROM AUTHOR]

High sensitivity and efficient X‐ray detectors are needed to promote and boost their application as tools in medical diagnostics and radiotherapy. Lead halide perovskites have emerged recently as a novel class of material for efficient X‐ray detection. Although 3D perovskites possess very interesting optoelectronic properties they suffer from low environmental and operational stability. Here a strategy based on using starch as a polymeric template for the fabrication of stable thin film perovskite X‐ray detectors is reported. The proposed p‐i‐n photodiodes can operate with no external bias applied (fully passive devices), reaching a top sensitivity of 5.5 ± 0.2 µC Gy−1 s−1. The device degradation is monitored for samples stored in air for a time window of 630 days, demonstrating exceptional stability: 97% of the initial sensitivity is retained for the best perovskite‐starch composite formulation making it the most stable unencapsulated perovskite X‐ray detector reported so far. [ABSTRACT FROM AUTHOR]

Perovskite CsPbBr3 semiconductors exhibit unusually high defect tolerance leading to outstanding and unique optoelectronic properties, demonstrating strong potential for γ-radiation and X-ray detection at room temperature. However, the total dose effects of the perovskite CsPbBr3 must be considered when working in a long-term radiation environment. In this work, the Schottky type of perovskite CsPbBr3 detector was fabricated. Their electrical characteristics and γ-ray response were investigated before and after 60Co γ ray irradiation with 100 and 200 krad (Si) doses. The γ-ray response of the Schottky-type planar CsPbBr3 detector degrades significantly with the increase in total dose. At the total dose of 200 krad(Si), the spectral resolving ability to γ-ray response of the CsPbBr3 detector has disappeared. However, with annealing at room temperature for one week, the device's performance was partially recovered. Therefore, these results indicate that the total dose effects strongly influence the detector performance of the perovskite CsPbBr3 semiconductor. Notably, it is concluded that the radiation-induced defects are not permanent, which could be mitigated even at room temperature. We believe this work could guide the development of perovskite detectors, especially under harsh radiation conditions. [ABSTRACT FROM AUTHOR]

The CsPbX 3 perovskites have demonstrated promising applications in the field of X-ray detection. Appropriate element doping to substitute Pb in CsPbX 3 not only improves the photoresponse performance of the resulting material but also reduces the Pb content for achieving environmental protection. Herein, X-ray detectors based on Sr-doped CsPb 1-x Sr x Br 3 thick films were developed. The effects of Sr doping concentration were investigated. The incorporation of Sr increased the density of the CsPbBr 3 thick film and modulated the bandgap of the materials. CsPb 1-x Sr x Br 3 exhibited good optical responses at different bias voltages and X-ray doses. The X-ray response improved as the Sr-doping concentration increased. Therefore, the partial substitution of Sr into CsPbBr 3 is suitable for reducing the Pb content in X-ray detectors. Furthermore, the development of CsPb 1-x Sr x Br 3 thick films provides a new strategy for the detection of X-rays. [ABSTRACT FROM AUTHOR]

In the past decade, metal halide perovskite (HP) has become a superstar semiconductor material due to its great application potential in the photovoltaic and photoelectric fields. In fact, HP initially attracted worldwide attention because of its excellent photovoltaic efficiency. However, HP and its derivatives also show great promise in X‐ray detection due to their strong X‐ray absorption, high bulk resistivity, suitable optical bandgap, and compatibility with integrated circuits. In this review, the basic working principles and modes of both the direct‐type and the indirect‐type X‐ray detectors are first summarized before discussing the applicability of HP for these two types of detection based on the pros and cons of different perovskites. Furthermore, the authors expand their view to different preparation methods developed for HP including single crystals and polycrystalline materials. Upon systematically analyzing their potential for X‐ray detection and photoelectronic characteristics on the basis of different structures and dimensions (0D, 2D, and 3D), recent progress of HPs (mainly polycrystalline) applied to flexible X‐ray detection are reviewed, and their practicability and feasibility are discussed. Finally, by reviewing the current research on HP‐based X‐ray detection, the challenges in this field are identified, and the main directions and prospects of future research are suggested. [ABSTRACT FROM AUTHOR]

Halide perovskite has remarkable optoelectronic properties, such as high atomic number, large carrier mobility-lifetime product, high X-ray attenuation coefficient, and simple and low-cost synthesis process, and has gradually developed into the next-generation X-ray detection materials. Halide perovskite-based X-ray detectors can improve the sensitivity and reduce the detectable X-ray dose, which is applied in imaging, nondestructive industrial inspection, security screening, and scientific research. In this article, we introduce the fabrication methods of halide perovskite film and the classification and progress of halide perovskite-based X-ray detectors. Finally, the existing challenges are discussed, and the possible directions for future applications are explored. We hope this review can stimulate the further improvement of perovskite-based X-ray detectors. [ABSTRACT FROM AUTHOR]

The new generation of synchrotron light sources are pushing X-ray detectors to their limits. Very demanding conditions with unprecedented flux and higher operating energies now require high-performance X-ray detectors combining sensitivity, efficiency and scalability. Over the years, hybrid pixel detectors have supplemented indirect detectors based on scintillation, with undeniable advantages. Such detectors based on silicon are, however, rather expensive to produce and are no more satisfying in terms of X-ray stopping power when targeting energies above 20 keV. An indirect detector with single X-ray photon sensitivity therefore offers promising opportunities for applications operating over a wide range of energies and fluxes. In this work, the performances of such an approach are investigated with state-of-the-art elements: a commercial sCMOS camera with fiber-optics plate coupling and a Gd2O2S:Tb powder-based scintillator. A simple method is presented for evaluation of the single X-ray photon detection limit and single X-ray sensitivity is demonstrated with the studied detector above 20 keV. Geant4 simulations also provide insight to better define the limiting factors. Finally, guidelines are provided for future R&D in the design and assembly of an innovative detector combining advantages of direct and indirect detection schemes. [ABSTRACT FROM AUTHOR]

[Display omitted] Large-area flexible perovskite films are attracting widespread research interest for applications in wearable solar cells, portable photodetectors, bendable X-ray imaging detectors and other implantable optoelectronic devices. In this work, a facile mobile platform assisted electrospray method is developed to prepare large-area (100 cm2) lead-free Cs 2 TeI 6 film on flexible polyimide substrate. The spraying parameters are coupled with the growth temperature to achieve a dynamic balance. The as-prepared film by optimized process shows high uniformity in grain size, thickness and X-ray response without pinholes and cracks. Moreover, oriented nucleation is more likely to occur on the flexible organic substrates for less growth stress and mismatch stress, leading to preferred (2 2 2) plane orientation. X-ray detectors prepared with the films exhibit a resistivity of 1.9 × 1011 Ω·cm, an X-ray sensitivity of 226.8 μC⋅Gy air -1⋅cm−2 and a transient response rise time as fast as 42 ms under 50 kV X-ray at an electrical field of 6.67 × 103 V·mm−1. The modified electrospray method shows great potential applications for large-area devices of radiography, solar cell and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

With the extensive application of object detection in intelligent security, the demand for detecting prohibited items in X-ray images has become increasingly stringent. Unlike natural images, X-ray images present unique challenges such as complex backgrounds and mutual occlusion between prohibited and normal items. Consequently, applying traditional detection methods to X-ray images remains a significant challenge. To tackle these challenges, we have developed a unique frequency-aware dual-stream transformers (FDTNet) that is specifically designed for analyzing X-ray images. The FDTNet consists of two streams: one handles the original image, while the other deals with an image that has been enhanced with frequency domain features. In order to achieve precise detection of prohibited items, we introduce a frequency-aware module (FAM) that enhances the representation of prohibited items by utilizing information from the frequency domain. This FAM can be easily integrated into other backbones or detectors as it is a plug-and-play module. Additionally, to enhance the fusion of feature maps from both streams, we utilize a global and channel attention module (GCA) that aggregates texture representations for spatial feature streams. Our evaluation of the proposed FDTNet on the OPIXray datasets and PIDray datasets demonstrates that our detection mAP achieves 88.02 and 68.2, respectively. Extensive experiments conducted on publicly available datasets provide substantial evidence that our proposed network significantly improves the detection of prohibited items compared to state-of-the-art methods. [Display omitted] • The dual-stream design is used to extract RGB features and frequency features respectively • Global and channel attention module enhances the features generated by the RGB stream using attention mechanisms. • Frequency-aware module encodes frequency features, enabling better capture frequency information. [ABSTRACT FROM AUTHOR]

Transition-edge sensors (TES) are outstanding calorimeters based on the steep superconductive transition of a metallic film. Among other photon detectors, they are renowned for the fine energy resolution, the photon-number resolving (PNR) capability and an extremely low dark count rate. Due to the broad detection spectrum, from gamma-ray to visible and submillimetre wavelengths, TESs are highly sought-after in a great variety of fields, such as X-ray detection and quantum technologies. Each of these fields demands a step forward in TESs performance with regards to the recovery time and energy resolution. Here we present a program, primarily capable of predicting the performance of TESs. Using established theoretical and empirical methods we developed a software that allows the users to choose active area, thickness, and material composition of a TES and to calculate its performance. Furthermore, the software can simulate TES properties at different working points. The aim of the software is to minimize the production cost and speed up the overall process for the creation of new devices with improved performance. [ABSTRACT FROM AUTHOR]

Perovskite X-ray detectors are actively investigated because of their exceptional properties, including their significant attenuation coefficient, low defect density, excellent transport characteristics, easy growth, and high sensitivity to X-ray photons. However, perovskite-based high-energy X-ray detectors on the MeV scale are rarely explored. In this study, we investigate the optoelectronic characteristics and radiation detection capabilities of triple-cation Cs 0.05 FA 0.9 MA 0.05 PbI 3 single crystals (CSC) grown using the inverse temperature crystallization method. The CSCs with a reduced Goldschmidt tolerance factor owing to the presence of Cs and MA ions exhibit exceptional properties, including a bandgap of 1.447 eV, low dark current, and self-powered response to X-ray irradiation. The X-ray absorption rate of 36 keV exceeded 99% with a CSC thickness of 2 mm, demonstrating its strong stopping power. Moreover, the CSC detectors exhibit precise linear responses to varying X-ray doses and dose rates with R2 values close to 1 and relative standard deviation (RSD) values below 3% under all the tested conditions. In addition, the detector effectively detected high-energy X-rays of up to 15 MV with minimal variations in the RSD values. These findings highlight the potential of CSC as promising materials for high-performance X-ray detectors. • Triple-cation lead–halide perovskites for high-energy X-ray detection were studied. • CSC detector has uniform linear response to varying X-ray doses and rates. • CSC detector can detect high-energy X-rays of up to 15 MeV. • CSC demonstrated remarkable promise as excellent self-powered X-ray detectors. [ABSTRACT FROM AUTHOR]

X-ray detection limit and sensitivity are important figure of merits for perovskite X-ray detectors, but literatures lack a valid mathematic expression for determining the lower limit of detection for a perovskite X-ray detector. In this work, we present a thorough analysis and new method for X-ray detection limit determination based on a statistical model that correlates the dark current and the X-ray induced photocurrent with the detection limit. The detection limit can be calculated through the measurement of dark current and sensitivity with an easy-to-follow practice. Alternatively, the detection limit may also be obtained by the measurement of dark current and photocurrent when repeatedly lowering the X-ray dose rate. While the material quality is critical, we show that the device architecture and working mode also have a significant influence on the sensitivity and the detection limit. Our work establishes a fair comparison metrics for material and detector development. The limit of X-ray detection is an important figure of merit for X-ray detectors, yet the suitability of method adopted from Currie's 1968 paper and the following international standard is in doubt. Here, the authors propose a statistical model that correlates dark current and photo-current, show how it can be used to determine detection limit. [ABSTRACT FROM AUTHOR]

X-ray detection and imaging have arose lots of attentions in modern society, due to its stronger penetrating ability. This review highlights the potential of different kinds of halide perovskites for direct X-ray detector and imager, and systematically summaries current progress on them, as well as a brief outlook presents for further boosting their performances. [Display omitted] X-ray detection has significantly applied in medical diagnostics, railway flaw detection, security screening, non-destructive testing in industrial products and quality inspection in food industry et al. Recently, as one of the alternative materials, halide perovskites show great potential in high-performance X-ray detector for their relatively high atomic number, superior carrier life-time produce, tunable band gap, and low temperature fabrication process. Accordingly, based on halide perovskite, some advanced and meaningful work was conducted, and corresponding performances of X-ray detector have reached a comparative height. Herein, we aim at systematically summarizing current progress on halide perovskite based X-ray detectors: (1) First, an introduction of background and key parameters is provided to understand the X-ray detectors clearly; (2) After that, we put an emphasis on the advanced work for various halide perovskites based X-ray detectors. Meanwhile, their optimized strategies and applications in imaging are presented; (3) Finally, the challenges remained and promising opportunities are also presented, for further boosting the performance of halide perovskites based X-ray detectors. [ABSTRACT FROM AUTHOR]

Immediate and accurate detection of foreign metal objects (FMOs) in clothing products is important for guaranteeing human safety. This article proposes an online detection approach based on deep learning, which is suitable for detecting small FMOs from X-ray images of clothing packages. A conveyor belt X-ray scanning system is developed for image collection. The X-ray images are preprocessed by using the morphological erosion operation to improve the accuracy of FMOs detection. These images are then down-sampled to reduce the computation cost. Feature pyramid network (FPN) is adopted for aggregating feature maps with different resolutions, which proved to be effective for small FMOs detection. The stochastic gradient descent (SGD) is used to optimize a multitask loss. The trained model was tested offline on 200 X-ray images, which achieved precision = 0.999, recall = 0.988, F1-score = 0.993, and AP = 0.946. Compared to original Faster region-based convolutional neural networks (R-CNN), the proposed method significantly improved the performance for small FMOs detection in terms of precision and recall rate. [ABSTRACT FROM AUTHOR]

Direct X-ray detection plays an indispensable role in medical and industrial development. However, developing a stable, low-cost, and sensitive direct X-ray detector is highly desired for future commercial application. In this work, a direct X-ray detector using a straightforward digital printing fabrication process based on nontoxic micropyramid triclinic bismuth oxide (ω-Bi2O3) ink is reported. The printed device exhibits a low detection limit of 56.95 μ Gyair s−1 with a sensitivity of 3.077 μC Gyair−1 cm−2 at 20 V bias voltage, which is better than most of the metal oxide-based direct X-ray detectors reported so far. Furthermore, the ω-Bi2O3 based X-ray detector shows excellent stability without packaging for eight months and exposure to a dose of 5120 mGyair equivalent to 25 000 chest X-ray scans. The applicability of our array device printed in a direct patterning method as an X-ray imaging detector is shown. Our findings inform a qualified competitor in the medical and industrial fields in the future. [ABSTRACT FROM AUTHOR]

We characterized the performance of abiased superconducting nanowire to detect X-ray photons. The device, made of a 10 nm thin NbTiN film and fabricated on a dielectric substrate (SiO2, Nb3O5) detected 1000 times larger signal than anticipated from direct X-ray absorption. We attributed this effect to X-ray induced generation of secondary particles in the substrate. The enhancement corresponds to an increase in the flux by the factor of 3.6, relative to a state-of-the-art commercial X-ray silicon drift detector. The detector exhibited 8.25 ns temporal recovery time and 82 ps timing resolution, measured using optical photons. Our results emphasize the importance of the substrate in superconducting X-ray single photon detectors. [ABSTRACT FROM AUTHOR]

[Display omitted] CsPbBr 3 -CsPb 2 Br 5 wafer is obtained by water-assisted coprecipitation method, and a spray-coating method is further utilized to convert it into CsPbBr 3 -CsPb 2 Br 5 -CsPbI x Br 3-x composite wafer, which exhibits superior performance and reliability of X-ray detection. • Water-assisted coprecipitation is proposed to prepare high-quality CsPbBr 3 -CsPb 2 Br 5 powder. • CsPbBr 3 -CsPb 2 Br 5 wafer is obtained by pressure-induced aggregation of the powder. • Spray-coating of CsI/H 2 O onto CsPbBr 3 -CsPb 2 Br 5 wafer can convert it into CsPbBr 3 -CsPb 2 Br 5 -CsPbI x Br 3-x composite wafer. • X-ray detector with the composite wafer exhibits much improved performance and reliability. Lead halide perovskite wafers with large lateral size, controllable thickness, and desirable optoelectronic characteristics are promising for X-ray detectors. Herein, CsPbBr 3 -CsPb 2 Br 5 -CsPbI x Br 3-x composite wafers are prepared via water-assisted coprecipitation and spray coating. The preparation involved pressure-induced aggregation of the CsPbBr 3 -CsPb 2 Br 5 powder produced through coprecipitation using of H 2 O/MeOH mixed solvent into CsPbBr 3 -CsPb 2 Br 5 wafers, followed by spraying a CsI/H 2 O solution onto the wafer surface to transform it into a CsPbBr 3 -CsPb 2 Br 5 -CsPbI x Br 3-x composite wafer. Multiple favorable properties, including compact surface, high crystallinity, excellent carrier transportation, large/adjustable size, low cost, and mass producibility, can be identified for the CsPbBr 3 -CsPb 2 Br 5 -CsPbI x Br 3-x composite wafer. An X-ray detector with high performance and excellent stability is realized with this wafer. It yields high resistivity (ρ; 1.3 × 109 Ω cm−2, exceptional carrier mobility (μ)/lifetime (τ) (μτ) product (1.01 × 10−3 cm2 V−1), high sensitivity (20555.1 μC Gy air −1 cm−2), and low detection limit (127.7 nGy s−1). Hence, our research provides a reliable strategy for optimizing the structure and performance of perovskite wafer-based X-ray detectors and enabling mass preparation. [ABSTRACT FROM AUTHOR]

In this work, a large size x-ray detector with a 25 mm2 active area is demonstrated based on a thick 4H-SiC p-i-n structure. The detector exhibits obvious merits of high photon sensitivity over 4 × 104μC Gy−1 cm−2, good photon-response linearity, and high-temperature operation compatibility. Meanwhile, due to the ultralow leakage current level achieved, single photon detection performance for x-ray photons is further realized with energy resolutions of 1.1 and 4.9 keV at 5.9 and 59.5 keV, respectively. This work thus suggests the significant potentials of wide-bandgap SiC semiconductor for photon-resolved x-ray detection in a harsh environment. [ABSTRACT FROM AUTHOR]

Indirect flat panel detectors (I‐FPDs) enable digital radiography at high X‐ray energies. However, the performance of these devices is limited due to the large number of X rays that pass through them undetected. The authors hypothesize that a glass‐based scintillator may serve as a substrate for the thin film transistors and photodiodes in an I‐FPD, leading to improvements in X‐ray detection for improved performance. The authors synthesized a series of five glass‐ceramic scintillators based on an oxyhalide glass matrix. Each glass ceramic contains barium chloride crystals which serve as scattering centers to prevent "light trapping" in the material; barium chloride is also a well‐known scintillation crystal. Four of the samples contain trivalent terbium, which serves as a second luminescent center. The light output of each sample was compared against a well‐known X‐ray scintillator, gadolinium oxysulfide (GOS) under RQA9 exposure conditions, in the back‐irradiation configuration. The addition of terbium oxide to the glass composition increases the detected light output, which varies by concentration. The thickness of the glass‐ceramic scintillator has a profound effect on performance, with the results influenced by such factors as self‐attenuation of emission in the thicker samples and decreased X‐ray capture in the thinner samples. The brightest sample tested achieved a light output 13% that of the GOS intensifier screen. The results indicate that the use of scintillating glass‐ceramic substrates should lead to increased performance in indirect digital radiography. [ABSTRACT FROM AUTHOR]

X-ray fluorescence computed tomography (XFCT) with nanoparticles (NPs) as contrast agents shows potential for molecular biomedical imaging with higher spatial resolution than present methods. To date the technique has been demonstrated on phantoms and mice, however, parameters such as radiation dose, exposure times and sensitivity have not yet allowed for high-spatial-resolution in vivo longitudinal imaging, i.e., imaging of the same animal at different time points. Here we show in vivo XFCT with spatial resolution in the 200- $400~\boldsymbol {\mu }\text{m}$ range in a proof-of-principle longitudinal study where mice are imaged five times each during an eight-week period following tail-vein injection of NPs. We rely on a 24 keV x-ray pencil-beam-based excitation of in-house-synthesized molybdenum oxide NPs (MoO2) to provide the high signal-to-background x-ray fluorescence detection necessary for XFCT imaging with low radiation dose and short exposure times. We quantify the uptake and clearance of NPs in vivo through imaging, and monitor animal well-being over the course of the study with support from histology and DNA stability analysis to assess the impact of x-ray exposure and NPs on animal welfare. We conclude that the presented imaging arrangement has potential for in vivo longitudinal studies, putting emphasis on designing biocompatible NPs as the future focus for active-targeting preclinical XFCT. [ABSTRACT FROM AUTHOR]

Cadmium–zinc–telluride (CZT) pixel detectors represent a consolidated choice for the development of room‐temperature spectroscopic X‐ray imagers, finding important applications in medical imaging, often as detection modules of a variety of new SPECT and CT systems. Detectors with 3–5 mm thicknesses are able to efficiently detect X‐rays up to 140 keV giving reasonable room‐temperature energy resolution. In this work, the room‐temperature performance of 3 mm‐thick CZT pixel detectors, recently developed at IMEM/CNR of Parma (Italy), is presented. Sub‐millimetre detector arrays with pixel pitch less than 500 µm were fabricated. The detectors are characterized by good room‐temperature performance even at high bias voltage operation (6000 V cm−1), with energy resolutions (FWHM) of 3% (1.8 keV) and 1.6% (2 keV) at 59.5 keV and 122.1 keV, respectively. Charge‐sharing investigations were performed with both uncollimated and collimated synchrotron X‐ray beams with particular attention to recovering the charge losses at the inter‐pixel gap region. High rate measurements demonstrated the absence of high‐flux radiation‐induced polarization phenomena up to 25 × 106 photons mm−2 s−1. [ABSTRACT FROM AUTHOR]

The sensitive detection of low-dose X-ray radiation is essential to many X-ray applications. In this article, the ultrasensitive X-ray detector based on pure Cs2AgBiBr6 all-inorganic lead-free perovskite film is successfully demonstrated and encapsulated using a metal casing with a Be window. The high-quality Cs2AgBiBr6 films are obtained through the low-cost solution process with long electron–hole diffusion length (~700 nm) and long carrier lifetime (~750 ns). Benefiting from the excellent properties of the Cs2AgBiBr6 film and the stable ambient provided by the packaging module, the resulting device exhibits attractive X-ray detection capabilities with a minimum detectable dose rate of 145.2 nGyairs−1 and a detection sensitivity up to 1.8 × 104μ nGyair−1 cm−2, which is about a thousand times higher than the sensitivity achieved with commercial a-Se X-ray detectors. Besides, the encapsulated device maintains superior detection performance after 2 months of storage, indicating the favorable reliability of the encapsulated device. This article demonstrates a possibility to use Cs2AgBiBr6 perovskite film and Be window for the sensitive X-ray detection, which will inspire further development of radiation electronics by utilizing all-inorganic lead-free perovskite. [ABSTRACT FROM AUTHOR]

(010) EFG-grown Fe-doped β-Ga2O3 was tested as a low-noise X-ray detector with Ti/Au electrodes vertical structure. Its performance at low, high and no applied voltages was examined. The fabricated detector showed high X-ray detection performance manifested in its signal's short fall and rise time (< 0.3 s) in all operation modes, showing two orders of magnitude decrease in response time of β-Ga2O3 X-ray detectors. The same temporal response was exhibited by a tested Au/Ni/β-Ga2O3/Ti/Au device. The detector's signal is also characterized by excellent linear relation with X-ray tube current and high signal-to-noise ratio (SNR) optimized at − 5 V (> 103). Moreover, the X-ray-induced current signal exhibits high stability. Sub-band UV photocurrent signal showed a significantly slower response compared to X-ray-induced conductivity signal. Possible charge transport mechanisms involving ion migration are suggested and discussed. In this study, Fe doping is shown to significantly improve X-ray detection performance of Ga2O3, consolidating the applicability of Ga2O3 as a next-generation X-ray detector functioning with low power, high SNR and linearity, and significantly improved transient characteristics. [ABSTRACT FROM AUTHOR]

In the context of time domain astronomy, we present an offline detection search of gamma-ray transients using a wild binary segmentation analysis called F-WBSB targeting both short and long gamma-ray bursts (GRBs) and covering the soft and hard gamma-ray bands. We use NASA Fermi /GBM archival data as a training and testing data set. This paper describes the analysis applied to the 12 NaI detectors of the Fermi /GBM instrument. This includes background removal, change-point detection that brackets the peaks of gamma-ray flares, the evaluation of significance for each individual GBM detector, and the combination of the results among the detectors. We also explain the calibration of the ∼ 10 parameters present in the method using one week of archival data. Finally, we present our detection performance result for 60 d of a blind search analysis with F-WBSB by comparing to both the onboard and offline GBM search as well as external events found by others surveys such as Swift -BAT. We detect 42/44 onboard GBM events but also other gamma-ray flares at a rate of 1 per hour in the 4–50 keV band. Our results show that F-WBSB is capable of recovering gamma-ray flares, including the detection of soft X-ray long transients. FWBSB offers an independent identification of GRBs in combination with methods for determining spectral and temporal properties of the transient as well as localization. This is particularly useful for increasing the GRB rate and that will help the joint detection with gravitational-wave events. [ABSTRACT FROM AUTHOR]

Detection of heavy elements, such as metals, in macromolecular crystallography (MX) samples by X‐ray fluorescence is a function traditionally covered at synchrotron MX beamlines by silicon drift detectors, which cannot be used at X‐ray free‐electron lasers because of the very short duration of the X‐ray pulses. Here it is shown that the hybrid pixel charge‐integrating detector JUNGFRAU can fulfill this function when operating in a low‐flux regime. The feasibility of precise position determination of micrometre‐sized metal marks is also demonstrated, to be used as fiducials for offline prelocation in serial crystallography experiments, based on the specific fluorescence signal measured with JUNGFRAU, both at the synchrotron and at SwissFEL. Finally, the measurement of elemental absorption edges at a synchrotron beamline using JUNGFRAU is also demonstrated. [ABSTRACT FROM AUTHOR]

Doped and stabilized amorphous selenium (a-Se) alloys in a multilayer form are currently used as a photoconductor in direct conversion flat panel x-ray imagers in mammography and tomosynthesis. While much progress has been made on the physics of such detectors, there are still unresolved questions on such issues as the principles of operation of the so-called p-i-n detector structure in extinguishing the dark current. The present paper examines dark current transients after the application of a voltage in seven types of a-Se alloy based devices: i-layer, i-n, n-i, i-p, p-i, p-i-n, and n-i-p structures. The substrate was ITO coated glass, the top (radiation receiving) electrode was chromium, and the films were fabricated by vacuum deposition. The nominal device thickness was 200 μm, similar to commercial mammographic detectors. It is shown that n-i, i-n, n-i-p, and p-i-n devices have dark currents less than 1 pA mm−2 at an applied field of 10 V/μm. The dark current in the p-i-n device is the lowest at approximately 0.01 pA mm−2 at an applied field of 10 V μm−1. Experiments have been carried out by subjecting the detector to a staircase voltage-time profile during the voltage application (turn-on) and a staircase voltage ramp-down during the turning-off of the bias voltage. Step-voltage ramp-up and step-voltage ramp-down current transient are typical of expected dark current transient behavior in a semiconductor with traps in which carriers are captured and released from various trap centers in the bandgap. The dark current transients are qualitatively similar to those expected from a capacitor in parallel with a large resistor and both in series with a much smaller resistor. Current transients during charging and discharging experiments were integrated to find how much of the injected charge is released during discharge experiments. It is shown that the majority of this trapped charge is stored in the n-type and p-type blocking layers, near the contacts. The trapped carriers in the i-layer represent a very small portion. The evolution of the dark current upon single and repeated x-ray exposure has also been examined in n-i and p-i-n devices. Right after the cessation of irradiation, there is an excess or residual dark current whose magnitude is roughly ∼20 times higher in p-i-n and about ∼2 times higher in the case of n-i under an exposure of 3.36 R and a mean photon energy of 34.2 keV. The absorbed dose is 1.53 Gy. The excess dark current has a fast decay component with a time constant ∼10 s and a slow component with a time constant ∼100 s. It is shown that the decay in the irradiation induced excess dark current is very similar to the initial dark current. There is no permanent change in the dark current, and within a few hundred seconds, the dark current reaches the same level as that in the unexposed detector. The experimental results in this work highlight the distinct advantages of p-i-n and n-i-type a-Se multilayer structures in x-ray detection applications. [ABSTRACT FROM AUTHOR]

Metal halide perovskites have gained significant attention as promising materials for ionizing radiation detection due to their facile fabrication process, exceptional optoelectronic properties and high attenuation coefficients. To effectively absorb the incident X-ray photons, thick active layers have been reported and fabricated via spray-coating. However, the conventional spray-coating method is susceptible to various adverse effects, making it challenging to achieve high-quality thick perovskite films. In this work, we propose the use of antisolvent-assisted spray-coating to deposit perovskite films, which results in small surface roughness, thick films on various substrates. The slow growth of the thick film and the ability to regulate its crystallization through the modulation of processing atmosphere were also carefully studied. The optimized X-ray detector demonstrated a sensitivity of up to 3370.8 μC Gy air −1 cm−2, demonstrating its great potential for X-ray detection applications. • Anti-solvent spray-coating technique was established to deposit perovskite thick films. • The spray-coating process was systematically investigated and optimized. • Optimized devices based on antisolvent-assisted X-ray detectors are promising for real applications. [ABSTRACT FROM AUTHOR]

Recent advances in segmented low‐gain avalanche detectors (LGADs) make them promising for the position‐sensitive detection of low‐energy X‐ray photons thanks to their internal gain. LGAD microstrip sensors fabricated by Fondazione Bruno Kessler have been investigated using X‐rays with both charge‐integrating and single‐photon‐counting readout chips developed at the Paul Scherrer Institut. In this work it is shown that the charge multiplication occurring in the sensor allows the detection of X‐rays with improved signal‐to‐noise ratio in comparison with standard silicon sensors. The application in the tender X‐ray energy range is demonstrated by the detection of the sulfur Kα and Kβ lines (2.3 and 2.46 keV) in an energy‐dispersive fluorescence spectrometer at the Swiss Light Source. Although further improvements in the segmentation and in the quantum efficiency at low energy are still necessary, this work paves the way for the development of single‐photon‐counting detectors in the soft X‐ray energy range. [ABSTRACT FROM AUTHOR]

The influence of line-broadening and zero shift of the sensor on identifying spectral lines was eliminated by an improved K-medoids clustering algorithm after performing principal component analysis on the spectral band of interest. The intensity ratio of the acquired spectral lines was calculated and dealt with by empirical mode decomposition to predict the existence of porosity based on the method given by our previous study. Furthermore, the effect of sheet gap on porosity formation was investigated by the proposed method. The analysis results were verified by X-ray detection, which demonstrated the distribution of porosity as well. The results showed that an appropriate gap could contribute significantly to reducing the porosity. The spectral sensor system and analysis method proposed in this study may help decrease the testing costs and increase productivity, while maintaining high weld quality. [ABSTRACT FROM AUTHOR]

A new technology for detecting a tiny residual core in the small inner cavity of complex castings is proposed. The residual core is identified by using image recognition technology. Tracer processing and image signal processing are combined to enhance the image contrast. The relationships between the concentration of tracer, the size of the residual core, the wall thickness of the castings and the contrast were obtained. Based on the experimental data, the minimum detectable amount of residual core under different conditions was obtained. The results show that the minimum detectable amount decreases from 4.398 mg to 0.438 mg for the 1.0 mm wall thickness casting when the concentration of tracer increases from 0% to 20%. The signal-to-noise ratio (SNR) of the detection results increases by 27.010 by means of average filtering and linear point operation. The subtraction of image and image background was performed, and then the boundary extraction was carried out to obtain a clear and reliable result. The experimental results show that the non-traced residual core cannot be detected for a blade with a thickness less than 5 mm. The residual core of 1 mm thickness can be barely identified by artificial recognition after tracer processing and image processing, while the residual core of 0.6 mm thickness can be detected clearly using image recognition technology. [ABSTRACT FROM AUTHOR]

This paper presents the performance of a single‐photon‐counting hybrid pixel X‐ray detector with synchrotron radiation. The camera was evaluated with respect to time‐resolved experiments, namely pump–probe–probe experiments held at SOLEIL. The UFXC camera shows very good energy resolution of around 1.5 keV and allows the minimum threshold setting to be as low as 3 keV keeping the high‐count‐rate capabilities. Measurements of a synchrotron characteristic filling mode prove the proper separation of an isolated bunch of photons and the usability of the detector in time‐resolved experiments. [ABSTRACT FROM AUTHOR]

X-ray detectors have drawn great attention due to their wide applications in medical imaging and industrial inspection. Lead halide perovskite exhibits excellent X-ray detection merits because of its high-Z element and outstanding photoelectric properties. However, the perovskite-based X-ray detectors exhibit poor stability, low resistivity and large dark leakage current due to the soft lattice and ion migration of perovskite materials. Herein, we used Ga 2 O 3 compact layer to form a heterojunction structure with formamidinum lead iodide (FAPbI 3) to largely ease these issues. Compared with the bare FAPbI 3 detector, the dark current of the FAPbI 3 /Ga 2 O 3 heterojunction detector is reduced by 3 orders of magnitude and the photo-to-dark current ratio (PDCR) increased by 31-fold. The detection limit of 0.23 mGys−1 is obtained which is 20 times lower than the FAPbI 3 detector and short response time of 20 ms is obtained. More importantly, the FAPbI 3 /Ga 2 O 3 device exhibits better repeatability due to the suppression of ion migration by Ga 2 O 3. This work provides an effective strategy to obtain low dark current and stable perovskite-based photodetector. • A coplanar interdigital MSM-structured X-ray detector was fabricated based on FAPbI 3 /Ga 2 O 3 heterojunction. • Low dark current density (4.1 pAmm−2), high PDCR (433) and low detection limit (0.23 mGys−1) were obtained. • The performance improvement of the device is due to the suppression of iodine ions migration by compact Ga 2 O 3. [ABSTRACT FROM AUTHOR]

The proposed spectral CT method solves the constrained one-step spectral CT reconstruction (cOSSCIR) optimization problem to estimate basis material maps while modeling the nonlinear X-ray detection process and enforcing convex constraints on the basis map images. In order to apply the optimization-based reconstruction approach to experimental data, the presented method empirically estimates the effective energy-window spectra using a calibration procedure. The amplitudes of the estimated spectra were further optimized as part of the reconstruction process to reduce ring artifacts. A validation approach was developed to select constraint parameters. The proposed spectral CT method was evaluated through simulations and experiments with a photon-counting detector. Basis material map images were successfully reconstructed using the presented empirical spectral modeling and cOSSCIR optimization approach. In simulations, the cOSSCIR approach accurately reconstructed the basis map images (<1% error). In experiments, the proposed method estimated the low-density polyethylene region of the basis maps with 0.5% error in the PMMA image and 4% error in the aluminum image. For the Teflon region, the experimental results demonstrated 8% and 31% error in the PMMA and aluminum basis material maps, respectively, compared with −24% and 126% error without estimation of the effective energy window spectra, with residual errors likely due to insufficient modeling of detector effects. The cOSSCIR algorithm estimated the material decomposition angle to within 1.3 degree error, where, for reference, the difference in angle between PMMA and muscle tissue is 2.1 degrees. The joint estimation of spectral-response scaling coefficients and basis material maps was found to reduce ring artifacts in both a phantom and tissue specimen. The presented validation procedure demonstrated feasibility for the automated determination of algorithm constraint parameters. [ABSTRACT FROM AUTHOR]

Direct conversion crystalline silicon X-ray imagers are used for low-energy X-ray photon (4–20 keV) detection in scientific research applications such as protein crystallography. In this paper, we demonstrate a novel pixel architecture that integrates a crystalline silicon X-ray detector with a thin-film transistor amorphous silicon pixel readout circuit. We describe a simplified two-mask process to fabricate a complete imaging array and present preliminary results that show the fabricated pixel to be sensitive to 5.89-keV photons from a low activity Fe-55 gamma source. This paper presented can expedite the development of high spatial resolution, low cost, direct conversion imagers for X-ray diffraction and crystallography applications. [ABSTRACT FROM PUBLISHER]

X-ray detectors in clinical computed tomography (CT) usually operate in current-integrating mode. Their complicated signal statistics often lead to intractable likelihood functions for practical use in model-based image reconstruction (MBIR). It is therefore desirable to design simplified statistical models without losing the essential factors. Depending on whether the CT transmission data are logarithmically transformed, pre-log and post-log models are two major categories of choices in CT MBIR. Both being approximations, it remains an open question whether one model can notably improve image quality over the other on real scanners. In this study, we develop and compare several pre-log and post-log MBIR algorithms under a unified framework. Their reconstruction accuracy based on simulation and clinical datasets are evaluated. The results show that pre-log MBIR can achieve notably better quantitative accuracy than post-log MBIR in ultra-low-dose CT, although in less extreme cases, post-log MBIR with handcrafted pre-processing remains a competitive alternative. Pre-log MBIR could play a growing role in emerging ultra-low-dose CT applications. [ABSTRACT FROM AUTHOR]

X-ray detectors that combine two-dimensional spatial resolution with a high time resolution are needed in numerous applications of synchrotron radiation. Most detectors with this combination of capabilities are based on semiconductor technology and are therefore limited in size. Furthermore, the time resolution is often realised through rapid time-gating of the acquisition, followed by a slower readout. Here, a detector technology is realised based on relatively inexpensive microchannel plates that uses GHz waveform sampling for a millimeter-scale spatial resolution and better than 100 ps time resolution. The technology is capable of continuous streaming of time- and location-tagged events at rates greater than 107 events per cm2. Time-gating can be used for improved dynamic range. [ABSTRACT FROM AUTHOR]

This paper presents a high-speed wafer-scale CMOS X-ray detector with an active area of 12~cm \times 12 cm, which features $100~\mu $ m-sized pixels. A horizontal row driver is adopted for implementing a three-side buttable detector with the tiling technique and thereby enabling the extension of the active area. The proposed detector employs 14-b column-parallel extended-counting analog-to-digital converters (EC ADCs) using digital correlated double sampling for high-speed operation and high-gray-scale resolution. The oversampling binning method using a $\Delta \Sigma $ modulator in EC ADCs is proposed for high sensitivity and the pipelined timing method is adopted for a high frame rate, which results in reduction of the X-ray dose. An offset cancellation method for the input buffer is used to improve the uniformity between column ADCs. The proposed CMOS X-ray detector is fabricated using a 0.35- $\mu $ m CMOS process with the stitching technique. The measured differential column fixed pattern noise and random noise without X-ray exposure are 3.01 and 3.06 least significant bits, respectively, at a resolution of 14 b. In the full-resolution mode, the proposed detector operates up to a frame frequency of 108 frames/s with the pipelined timing and 60 frames/s without the pipelined timing. [ABSTRACT FROM AUTHOR]

The energy information acquired using spectral X-ray detectors allows noninvasive identification and characterization of chemical components of a material. To achieve this, it is important that the energy response of the detector is calibrated. The established techniques for energy calibration are not practical for routine use in pre-clinical or clinical research environment. This is due to the requirements of using monochromatic radiation sources such as synchrotron, radio-isotopes, and prohibitively long time needed to set up the equipment and make measurements. To address these limitations, we have developed an automated technique for calibrating the energy response of the pixels in a spectral X-ray detector that runs with minimal user intervention. This technique uses the X-ray tube voltage (kVp) as a reference energy, which is stepped through an energy range of interest. This technique locates the energy threshold where a pixel transitions from not-counting (off) to counting (on). Similarly, we have developed a technique for calibrating the energy response of individual pixels using X-ray fluorescence generated by metallic targets directly irradiated with polychromatic X-rays, and additionally \gamma-rays from ^241Am. This technique was used to measure the energy response of individual pixels in CdTe-Medipix3RX by characterizing noise performance, threshold dispersion, gain variation and spectral resolution. The comparison of these two techniques shows the energy difference of 1 keV at 59.5 keV which is less than the spectral resolution of the detector (full-width at half-maximum of 8 keV at 59.5 keV). Both techniques can be used as quality control tools in a pre-clinical multi-energy CT scanner using spectral X-ray detectors. [ABSTRACT FROM PUBLISHER]

Polycrystalline PbI thick films were grown by using close spaced vapor deposition method on glass substrate with a conducting indium-tin-oxide coating. The morphology shows a uniquely oriented film structure with hexagonal platelets accurately being upright on substrate surface. An array detector with 12 pixels was fabricated based on this structure of the thick film. It is shown that the dark current is lower than 3 nA at bias voltage below 500 V, and the dark resistivity is as high as 10 Ω cm. A mapping of dark current density of the sensitive area of the array detector exhibits a better uniformity in the central area than the fringe area. A quick photocurrent response to X-ray excitation was obtained. The photoresponse rise time about 250 μs was obtained from the detectors and the photocurrent decays in a few seconds. The values of photocurrent are higher about two orders of magnitude than the values of dark current. The distribution of photocurrent is more uniform than that of dark current in the sensitive area of the detector. [ABSTRACT FROM AUTHOR]

Circuits that carry out the signal acquisition and processing by multiple channels are required in digital radiography. These circuits should be tested in order to characterize their performance. This paper describes an automated system to control (by a software, from a personal computer) the characterization of a system based on RX64DTH specific integrated circuits with microstrip detectors. The results are shown. [ABSTRACT FROM AUTHOR]

Superconducting tunnel junctions show an excellent energy resolution in X-ray detection. A simple procedure is employed to give an overview of the detector characteristics regardless of superconductor materials such as Al, Sn and Nb. By introducing an empirical relationship between junction parameters, the detector characteristics of signal magnitude and energy resolution are reproduced to an acceptable degree. This method gives helpful suggestion for understanding detector performance, and also serves as a guide line for designing tunnel junctions. [ABSTRACT FROM PUBLISHER]

In this study, we investigated the characteristics of an organic-inorganic hybrid indirect-type X-ray detector with a CH3NH3PbI3 (MAPbI3) perovskite active layer. A layer with a thickness of 192 nm annealed at 100 °C showed higher absorption, higher crystallinity, and lower surface roughness than did perovskite layers made under different conditions. In the indirect X-ray detector, a scintillator coupled with the detector to convert X-ray photons to visible photons, and the converted photons were absorbed by the active layer to generate charge carriers. The detector with the optimized MAPbI3 (192 nm thick and 100 °C annealing condition) active layer was coupled with a CsI(Tl) scintillator which consisted of 400 μm thick CsI and 0.5 mm thick Al, and achieved the highest sensitivity, i.e., 2.84 mA/Gy·cm2. In addition, the highest short-circuit current density (JSC), i.e., 18.78 mA/cm2, and the highest mobility, i.e., 2.83 × 10−4 cm2/V·s, were obtained from the same detector without the CsI(Tl) scintillator. [ABSTRACT FROM AUTHOR]

• A realistic response function is modeled for the CdTe detectors used in a hard X-ray diagnostic of the TCV tokamak. • The characteristics of the detector observed in the measurement of multiple radioactive. sources are considered in the modeling. • The measured energy spectra of radioactive sources can be correctly reconstructed using the new response function. • The response function is applied to a hard X-ray synthetic diagnostic for the study of energetic electrons. The response function of CdTe detectors used in a hard X-ray spectrometer system (HXRS) on the TCV tokamak fusion experiment is modeled based on the measured energy spectra from multiple gamma-ray sources. The response function consists of an asymmetric Gaussian photopeak, an exponentially inclined shelf structure below the photopeak, and CdTe escape peaks. It is demonstrated that the measured energy spectra of radioactive sources can be correctly reconstructed using this response function. This model is applied to a hard X-ray synthetic diagnostic used to convert a modeled electron distribution function to a measured hard X-ray signal, for the study of energetic electrons in the TCV tokamak. [ABSTRACT FROM AUTHOR]

Silicon shows very high detection efficiency for low-energy photons, and the silicon pixel sensor provides high spatial resolution. Pixelated silicon sensors facilitate the direct detection of low-energy X-ray radiation. In this study, we developed junction field effect transistors (JFETs) that can be integrated into a pixelated silicon sensor to effectively handle many signal readout channels due to the pixelated structure without any change in the sensor resolution; this capability of the integrated system arises from the pixelated structure of the sensor. We focused on optimizing the JFET's switching function, and simulated JFETs with different fabrication parameters. Furthermore, prototype JFET switches were designed and fabricated on the basis of the simulated results. It is important not only to keep the low leakage currents in the JFET but also reduce the current flow as much as possible by providing a high resistance when the JFET switch is off. We determined the optimal fabrication conditions for the effective switching of the JFETs. In this paper, we present the results of the measurement of the switching capability of the fabricated JFETs for various design variables and fabrication conditions. [ABSTRACT FROM AUTHOR]