X-ray Detector Research Articles

Multi-Axial Self-Driven X-Ray Detection by a Two-Dimensional Biaxial Hybrid Organic-Inorganic Perovskite Ferroelectric.

Metal halide perovskite ferroelectrics combining spontaneous polarization and excellent semiconducting properties is an ideal platform for enabling self-driven X-ray detection. However, achievements to date have been only based on uniaxiality, which increases the complexity of device fabrication. Multi-axial ferroelectric materials have multiple equivalent polarization directions, making them potentially amenable to multi-axial self-driven X-ray detection, but the report on these types of materials is still a huge blank. Herein, a high-quality (BA)2(EA)2Pb3I10 (1) biaxial ferroelectric single crystal was successfully grown, which exhibited significant spontaneous polarization along the c-axis and b-axis. Under X-ray irradiation, bulk photovoltaic effect (BPVE) was exhibited along both the c-axis and b-axis, with open circuit voltages (Voc) of 0.23 V and 0.22 V, respectively. Then, the BPVE revealed along the inversion of polarized direction with the polarized electric fields. Intriguingly, due to the BPVE of 1, 1 achieved multi-axial self-driven X-ray detection for the first time (c-axis and b-axis) with relatively high sensitivities and ultralow detection limits (17.2 nGyair s-1 and 19.4 nGyair s-1, respectively). This work provides a reference for the subsequent use of multi-axial ferroelectricity for multi-axial self-driven optoelectronic detection.

Non-Centrosymmetric Chiral Structures for Hybrid Bismuth Halides With Stable Self-Driven X-Ray Detection

Non-Centrosymmetric Chiral Structures for Hybrid Bismuth Halides With Stable Self-Driven X-Ray Detection

Superdense Ce3+-activated lutetium silicate scintillating glass for radiation detection

The scintillating photonic glass has the great potential for medicine imaging, nuclear physics, high-energy physics, and national defense. However, the development of the candidate with the high density remains a significant challenge. Herein, the superdense scintillating glasses derived from the Ce3+-activated Lu2O3-SiO2 binary system were successfully fabricated by the strategy of contactless aerodynamic levitation heating under the N2 atmosphere. These glasses are colorless, optical homogeneous, and exhibit superdense density from 6.59 to 7.15 g/cm3, representing the highest density among the fast decay glass systems. The materials present excellent radiation-blocking ability, suitable emission wavelength, and fast response, indicating the promise for fast-event X-ray detection. The micro radiation probe was fabricated by connecting the scintillating glass and the optical fiber. The practical application in remote radiation detection is demonstrated and it exhibits excellent linear response and high signal-to-noise ratio. The results confirm that the fabricated superdense scintillating glass is promising for application in the field of high-energy radiation detection.

Enhanced detection sensitivity of X-ray detectors via CdSe nanoplatelet aspect ratio control

This study investigated the use of inorganic cadmium selenide nanoplatelets (CdSe NPLs) to enhance the performance of X-ray detectors. The active layer of the detector comprised a bulk heterojunction composed of PCDTBT:PC71BM: CdSe NPLs with three different aspect ratios (ARs = 3:1, 1:1, and 6:1). The CdSe NPLs, synthesized with a thickness of five monolayers, were controlled by adjusting the molar mass ratios of Cd(OAc)2 and Cd(OAc)2∙2 H2O. Each detector was characterized by analyzing its series resistance, collection irradiation, dark current density, detection sensitivity, charge mobility, and defect density via the collected charges. The detector containing CdSe NPLs with an aspect ratio of 1:1 demonstrated the most favorable performance, exhibiting improved carrier generation and transport properties, resulting in a 23.36 % increase in sensitivity compared with the detector without CdSe NPLs. Through experimentation, the optimal content of CdSe NPLs in the active layer was determined to be 1 wt%, yielding the highest sensitivity of 3.96 × 103 μC∙Gy−1∙cm−2. This study underscores the potential of CdSe NPLs as promising materials for X-ray detector applications.

Technical challenges and benefits of photon counting detector computed tomography

X-ray detector is the essential part of a computed tomography (CT) system that controls dose efficiency and image quality. All clinical CT scanners utilized scintillating detectors up until the first clinical photon-counting-detector (PCD) system was approved in 2021. These detectors do not record information about individual photons during the two-step detection process. PCDs, on the other hand, employ a single step process that transforms X-ray radiation straight into an electrical signal. This retains information on individual photons, allowing one to count the quantity of X-rays in various energy ranges. Better spatial resolution, reduced dosages of iodinated contrast material, enhanced iodine signal, enhanced radiation dose efficiency, and the lack of electronic noise are the main benefits of PCDs. PCDs with multiple energy thresholds are able to separate detected photons into two or more energy bins, allowing for the availability of energy-resolved data for each record. In the event of dual-source CT, this permits high pitch or high temporal resolution acquisitions in addition to high spatial resolution for tasks involving material quantification or classification. PCDCT imaging of anatomy, where excellent spatial resolution provides clinical benefit, is one of the most promising uses of the technology. Inner ear, bone, small blood artery, heart, and lung imaging are among them. Photon-counting CT will become the wave of the future for workhorse CT imaging systems. An overview of the PCDCT principle, possible clinical benefits, and limitations of conventional CT is provided in this review paper, along with potential future developments for this CT imaging technology.

“Forbidden” stars in the eROSITA all-sky survey: X-ray emission from very late-type giants

We present the results of the first X-ray all-sky survey (eRASS1) performed by the eROSITA instrument aboard the Spectrum-Roentgen-Gamma (SRG) mission on X-ray emitting red giants and supergiants. Focusing on stars positioned at high galactic latitudes above 20°, we constructed a complete sample of such objects using the Gaia DR3 catalog and identified a sample 96 stars that appear as bona fide entries in the eRASS1 source catalog. By again restricting the sample to objects nearer than 1300 pc and eliminating all catalog entries that are due to optical contamination, we ended up with a sample of 16 genuine red giant or supergiant X-ray sources, most of which represent new X-ray detections. We present a low signal-to-noise X-ray spectrum of the nearby low-activity giant Arcturus obtained from a pointed observation with the XMM-Newton satellite and give a detailed account of our data analysis. We show that Arcturus-like X-ray emission cannot be the explanation for the X-ray emissions observed by eROSITA and provide a discussion of the possible nature of the detected X-ray sources.

Perspective of perovskite-based X-ray hybrid pixel array detectors

Compound semiconductors are playing a major role in the production of X-ray pixel detectors for the application in laboratories and beamlines at photon sources. The performance of these detectors has constantly been improved for the last decades but experiments are still limited by the properties of the detector material, especially under high flux illumination. The fast development of perovskite crystals opens the possibility for new materials to be used as highly efficient X-ray pixel detectors. The published data until now, of the transport properties, demonstrate the large potential of perovskite semiconductors. The achieved values are comparable with the ones of CdTe-based detectors. This paper presents potential perovskite-based detector materials and compares their performance with the state-of-the-art CdTe-based detectors. The perspectives of perovskite semiconductors are promising for the production of large area X-ray detectors but still some challenges remain.

Weakly Supervised Object Detection in Chest X-Rays with Differentiable ROI Proposal Networks and Soft ROI Pooling.

Weakly supervised object detection (WSup-OD) increases the usefulness and interpretability of image classification algorithms without requiring additional supervision. The successes of multiple instance learning in this task for natural images, however, do not translate well to medical images due to the very different characteristics of their objects (i.e. pathologies). In this work, we propose Weakly Supervised ROI Proposal Networks (WSRPN), a new method for generating bounding box proposals on the fly using a specialized region of interest-attention (ROI-attention) module. WSRPN integrates well with classic backbone-head classification algorithms and is end-to-end trainable with only image-label supervision. We experimentally demonstrate that our new method outperforms existing methods in the challenging task of disease localization in chest X-ray images. Code: https://anonymous.4open.science/r/WSRPN-DCA1.

Suppressed ion migration for high-performance X-ray detectors based on atmosphere-controlled EFG-grown perovskite CsPbBr3 single crystals

Suppressed ion migration for high-performance X-ray detectors based on atmosphere-controlled EFG-grown perovskite CsPbBr3 single crystals

A General Energy-Puzzle Strategy to Fabricate Efficient Metal–Organic Framework Scintillators for X-ray Detection

A General Energy-Puzzle Strategy to Fabricate Efficient Metal–Organic Framework Scintillators for X-ray Detection

Tailored molecular for ultra-stability and biocompatible pseudohalide metal-free perovskite towards X-ray detectors with record sensitivity

The emerging pseudohalide metal-free perovskite (pseudohalide–MFPs) X-ray detector caters to the demands of timely mobile diagnosis owing to its lightweight, flexibility, and cost-effectiveness. However, the performance of these devices is severely limited by poor X-ray absorption, ultra-wide band gap, relative instability, and their unknown biotoxicity. Herein, we construct heavy atom covalent bonds (C–Br/Cl) on the A-site organic cation to reinforce component coordination to modulate X-ray absorption and band gap in pseudohalide–MFPs and further enhance its stability. Molecular dynamics simulations demonstrate that the introduction of halogen atoms can strengthen hydrogen bonding interactions, thereby improving the coordination between different components. The resultant (MDABCOBr)–NH4(BF4)3 (MDABCO = N-methyl-N’-diazabicyclo[2.2.2]octonium) single crystal significantly increases X-ray absorption cross-section and crystalline density (from 1.728 to 1.950 g cm−3), and synergistically realizes the band nature modulation (from 7.4 to 5.5 eV) and enhanced ionic migration inhibition (628 meV) with optimized stability. As such, our X-ray detectors realized a sensitivity of 2377 μC Gyair−1 cm−2, an ultralow detection limit of 50.1 nGyair s−1, and impressive operation stability. Moreover, cytotoxicity assay confirmed the compatibility of pseudohalide metal-free perovskite. Finally, within this framework, we successfully fabricate the (MDABCOBr)–NH4(BF4)3-based flexible device to create an ideal in vitro wearable X-ray detection.

Research on flexural mechanical properties and mechanism of green ecological coir fiber foamed concrete (CFFC)

To explore the effect and mechanism of coir fiber on the performance of foamed concrete, the flexural performance test, pore characteristics and microstructure test of coir fiber foamed concrete with different content were carried out. First, Image-Pro Plus (image processing software) was used to study the pore morphology, porosity, average pore diameter, and pore roundness of CFFC with various fibers dosage (0, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%) by binarization processing method. Then, a total of eighteen specimens, divided into six groups, were used to investigate the effect of CF dosage on flexural strength, toughness, energy absorption, and failure patterns of FC through a three-point flexural test. Furthermore, the microscopic properties of coir fiber foamed concrete (CFFC) were observed by scanning electron microscope (SEM) and energy dispersive X-ray detector (XRD) to explain the influence mechanism of CF on FC flexural properties. According to the research, CF can affect the pore characteristics of CFFC and improve its flexural performance. When CF content is 1.5–2.0%, the porosity, diameter and roundness of CFFC have lower values of 68.6%, 1.96 mm and 1.29. After the fiber dosage reaches 1.5%, the CFFC failure mode changed to plastic damage, the flexural strength increased from 0.33 to 0.73 MPa, and the toughness energy absorption value was increased from 0.05 to 1.4 J. The optimum dosage of coir fiber is 2.0% for improving the flexural mechanical properties of FC. CF affects the process of hydration reaction of CFFC, but does not change the type of hydration product. However, the flexural performance of FC would decrease with excessive dosage of CF (> 2.0%) due to accelerating the formation of Ca(OH)2. CFFC can solve problems such as brittleness and easy cracking existing in traditional foamed concrete, and it can be used in the field of pavement engineering, foundation backfill and lightweight wall structure with CF dosage of 15–2.0%.

Low gain avalanche diodes for photon science applications

Low Gain Avalanche Diodes (LGADs) are silicon sensors designed to achieve an internal gain in the order of 10 through the impact ionization process. The development of LGADs was pushed forward by their application in High Energy Physics (HEP) experiments, where they will be employed to provide measurements of the time of arrival of minimum ionizing particles with a resolution of around 30 ps. The initial technological implementation of the sensors constrains their minimum channel size to be larger than 1 mm2, in order to reduce inefficiencies due to the segmentation of the gain structure. The gain of the sensors is kept in the order of 10 to limit the sensor shot noise and their power consumption. In photon science, the gain provided by the sensor can boost the signal-to-noise ratio of the detector system, effectively reducing the x-ray energy threshold of photon counting detectors and the minimum x-ray energy where single photon resolution is achieved in charge integrating detectors. This can improve the hybrid pixel and strip detectors for soft and tender x-rays by simply changing the sensor element of the detector system. Photon science applications in the soft and tender energy range require improvements over the LGADs developed for HEP, in particular the presence of a thin entrance window to provide a satisfactory quantum efficiency and channel size with a pitch of less than 100 μm. In this review, the fundamental aspects of the LGAD technology are presented, discussing also the ongoing and future developments that are of interest for photon science applications.

Bottom-up construction of low-dimensional perovskite thick films for high-performance X-ray detection and imaging

Quasi-two-dimensional (Q-2D) perovskite exhibits exceptional photoelectric properties and demonstrates reduced ion migration compared to 3D perovskite, making it a promising material for the fabrication of highly sensitive and stable X-ray detectors. However, achieving high-quality perovskite films with sufficient thickness for efficient X-ray absorption remains challenging. Herein, we present a novel approach to regulate the growth of Q-2D perovskite crystals in a mixed atmosphere comprising methylamine (CH3NH2, MA) and ammonia (NH3), resulting in the successful fabrication of high-quality films with a thickness of hundreds of micrometers. Subsequently, we build a heterojunction X-ray detector by incorporating the perovskite layer with titanium dioxide (TiO2). The precise regulation of perovskite crystal growth and the meticulous design of the device structure synergistically enhance the resistivity and carrier transport properties of the X-ray detector, resulting in an ultrahigh sensitivity (29721.4 μC Gyair−1 cm−2) for low-dimensional perovskite X-ray detectors and a low detection limit of 20.9 nGyair s−1. We have further demonstrated a flat panel X-ray imager (FPXI) showing a high spatial resolution of 3.6 lp mm−1 and outstanding X-ray imaging capability under low X-ray doses. This work presents an effective methodology for achieving high-performance Q-2D perovskite FPXIs that holds great promise for various applications in imaging technology.

TEMPUS, a Timepix4-based system for the event-based detection of X-rays.

TEMPUS is a new detector system being developed for photon science. It is based on the Timepix4 chip and, thus, it can be operated in two distinct modes: a photon-counting mode, which allows for conventional full-frame readout at rates up to 40 kfps; and an event-driven time-stamping mode, which allows excellent time resolution in the nanosecond regime in measurements with moderate X-ray flux. In this paper, the initial prototype, a single-chip device, is introduced, and the readout system described. Moreover, and in order to evaluate its capabilities, some tests were performed at PETRA III and ESRF for which results are also presented.

Observational clues to the magnetic evolution of magnetars

ABSTRACT Utilizing four archival X-ray data sets taken with the Hard X-ray Detector onboard Suzaku, timing studies were performed on three magnetars, 1E 1841−045 (observed in 2006), SGR 0501+4516 (2008), and 1RXS J170849.0−400910 (2009 and 2010). Their pulsations were reconfirmed, typically in an energy range of 12–50 keV. The 11.783 s pulses of 1E 1841−045 and those of SGR 0501+4516 at 5.762 s were periodically phase modulated, with a long period of $\approx 23.4$ and $\approx 16.4$ ks, respectively. The pulse-phase modulation was also observed, at $\approx 46.5$ ks, from two data sets of 1RXS J170849.0−400910. In all these cases, the modulation amplitude was 6 per cent to 16 per cent of the pulse cycle. Including previously confirmed four objects, this characteristic timing behaviour is now detected from seven magnetars in total, and interpreted as a result of free precession of neutron stars that are deformed to an asphericity of $\sim 10^{-4}$. Assuming that the deformation is due to magnetic stress, these magnetars are inferred to harbour toroidal magnetic fields of $B_{\rm t}\sim 10^{16}$ G. By comparing the estimated $B_{\rm t}$ of these objects with their poloidal dipole field $B_{\rm d}$, the $B_{\rm t}/B_{\rm d}$ ratio is found to increase with their characteristic age. Therefore, the toroidal fields of magnetars are likely to last longer than their poloidal fields. This explains the presence of some classes of neutron stars that have relatively weak $B_{\rm d}$ but are suspected to hide strong $B_{\rm t}$ inside them.

Mathematical modeling of radiation transparencies in the countable implementation of the dual energy method based on analog amplitude analysis of original signals

A mathematical model of radiation transparency in the computational implementation of the dual energy method based on analog discrimination of the original signals is given. The generalized mathematical model of radiation transparency in the analyzed implementation of the dual energy method is based on the analog separation of the initial electrical signals from the X-ray detector by amplitude into low-energy and high-energy signals with subsequent counting of these signals. Analog separation of the output signals of the X-ray detector by amplitude is carried out using a two-channel amplitude analyzer. The proposed model takes into account the maximum energy of X-ray photons, the energy threshold for separating signals into low-energy and high-energy signals, materials and sizes of radiation-sensitive detector elements, and parameters of control objects. The model can be used to conduct research on the influence of noise caused by the quantum nature of X-ray radiation on the quality of identification of the attenuating material, for example, by effective atomic number, in relation to the considered implementation of the dual energy method, as well as for a reasonable choice of parameters of the corresponding dual-energy digital radiography systems and X-ray computed tomography.

Surface Chemistry of Solution-Grown CsPbBr3 Single Crystals and Their Selective Cleaning for Linear-Responsive X-ray Detectors

Surface Chemistry of Solution-Grown CsPbBr₃ Single Crystals and Their Selective Cleaning for Linear-Responsive X-ray Detectors

Revisiting the dead time effects of Insight-HXMT/ME on timing analysis

ABSTRACT Dead time is a common instrumental effect of X-ray detectors, which would alter the behaviour of timing properties of astronomical signals, such as distorting the shape of power density spectra (PDS), affecting the root-mean-square of potential quasi-periodic oscillation signals, etc. We revisit the effects of the dead time of Medium Energy X-ray telescope (ME) onboard Insight-HXMT based on the simulation of electronic read-out mechanism that causes the dead time and the real data. We investigate dead time effects on the pulse profile as well as the quasi–periodic oscillation (QPO) signals. The dead time coefficient suggests a linear correlation with the observed count rate in each phase bin of the pulse profile according to the simulation of periodic signal as well as the real data observed on Swift J0243.6+6124. The Fourier-amplitude-difference (FAD) method could well recover the intrinsic shape of the observed PDS in the case that the PDS is from two identical detectors. We apply this technique on ME, by splitting the nine FPGA modules into two groups. The results indicate that the FAD technique suits the case when two groups of detectors are not largely different; and the recovered PDS of Sco X-1 observed by ME slightly enhances the significance of the previously known QPO signal, meanwhile the root-mean-square of QPO is significantly improved. We provide the FAD correction tool implemented in HXMTDAS for users in the future to better analyse QPO signals.

Development of an X-ray imaging camera for targeted radionuclide therapy with astatine-211

The alpha-particle targeted radionuclide therapy (TRT) has been actively investigated for cancer treatment, and astatine-211 (211At) is one of the promising alpha-particle emitters. To evaluate the efficacy of radioactive pharmaceuticals, it is necessary to understand the 211At distribution in a body to accurately assess radiation dose in the targeted cells. In this study, an X-ray imaging camera was developed to investigate an in vivo211At imaging technique for the alpha-particle TRT, especially to apply for small animal investigations. The design of the X-ray imaging camera was optimized to measure Po K X-rays (77–92 keV) emitted during 211At decay. It comprised a monolithic NaI(Tl) scintillator, a position-sensitive photomultiplier, and a tungsten pinhole collimator. The intrinsic performance evaluation of the position-sensitive X-ray detector exhibited good energy resolution, spatial resolution, and response uniformity. Using point-like 211At sources, the 211At distribution was successfully obtained by the X-ray camera with a useful field-of-view of 20.4 × 20.4 mm2, a system spatial resolution of 1.6 mm, and a sensitivity of 2.4 × 10−4, equivalent to 101 cps/MBq, on the collimator axis at a 12.5 mm distance. This study demonstrated the imaging capability of 211At with high sensitivity and spatial resolution by the X-ray imaging camera with a pinhole collimator.