X-ray Detector Research Articles

Preliminary design and development of the module back-end electronics for the large area detector onboard the eXTP mission

The Large Area Detector (LAD) is one of the science payloads of the enhanced X-ray Timing and Polarimetry (eXTP) mission. The LAD is a spectral-timing instrument with a broad energy response, covering a range from 2 to 30 keV, a good timing resolution of better than 10 µs, and an expected energy resolution of 260 eV at 6 keV. The LAD consists of 640 large-area multi-anode Silicon Drift Detectors (SDDs). Given the large number of detectors, the LAD uses a modular design. Each module comprises sixteen detectors, and each detector is equipped with dedicated Front-End Electronics (FEE), interfacing with two separate Module Back-End Electronics (MBEEs). Each MBEE is designed to process the data from 1,792 anode channels in 8 FEEs (224 anode channels per FEE), performing the energy reconstruction and time tagging for X-ray events. The MBEE uses the European Field Programmable Gate Array (FPGA) from NanoXplore™, based on a pipeline concept, which reduces dead time, making the LAD suitable for higher flux X-ray detection, and it can handle a sustained flux of >500 mCrab and a continuous flux of >15 Crab for up to 300 minutes (Feroci et al. 2018). Additionally, the MBEE serves as the central hub for configuring the module’s electronics, including the FEEs, the Power Supply Unit (PSU), and the MBEE itself, and it is also responsible for collecting housekeeping data to monitor the system’s status. The prototype MBEE was designed, manufactured, and programmed with FPGA firmware using VHDL. The basic functional test was conducted in this paper, and the results indicated that the MBEE could be operated in different modes to perform the functions mentioned above. Analysis and testing show that it can transmit event packets-containing timing tag, event type, position ID, and energy information-at a baud rate of 2 Mbps with an event loss fraction of 1.5%.

“Trash to Treasure” Recycling of Perovskite Single Crystals for X-ray Detection and Imaging

“Trash to Treasure” Recycling of Perovskite Single Crystals for X-ray Detection and Imaging

Zero-Dimensional Lead-Free Perovskite Single Crystals for the Sensitive Detection of Visible Light and X-Rays.

The excellent performance and facile fabrication process of perovskite semiconductor materials make them highly promising candidates in the field of optoelectronic devices. Whether for visible light or X-rays, detectors with low detection limits can better identify weak light signals, significantly reducing the intensity of the received light source during device operation. In particular, for X-ray detectors, reducing X-ray dosage can greatly enhance the safety of X-ray imaging technology. This work develops detectors with low detection limit based on zero-dimensional (0D) MA3Bi2I9 single crystals. The anisotropy of MA3Bi2I9 and its influence on the detector's performance were investigated in detail. Detectors perpendicular to the (001) crystal plane have better weak light detection capability and require significantly less light intensity compared to devices parallel to the (001) crystal plane. X-ray detector with a limit of detection (LoD) of 0.68 nGyair s‒1 and sensitivity of 5072 μC Gyair‒1 cm‒2 was obtained. The present study offers comprehensive insights into the operational mechanism of layered perovskites, which can provide valuable guidelines for future designs and fabrications of highly sensitive photo and X-ray detectors.

High-Performance Perovskite Flat Panel X-Ray Imagers via Blade Coating.

Perovskite X-ray detectors are recognized as the most promising candidates for low-dose detectors due to their superior performance. However, it is still full of challenging in the fabrication of flat-panel X-ray imagers (FPXIs), primarily due to the absence of large area thick films that exhibit high uniformity and long-term performance stability. A general synthesis route is urgently needed to grow large-scale halide perovskite thick films directly on a pixeled thin-film transistor (TFT) backplane with high uniformity, closing the gap between the great potential of perovskite X-ray detectors and their entry into the market. In this work, an advanced precursor paste suitable for blade coating is developed to enable high-throughput manufacturing of FPXIs. Highly uniform perovskite films with a thickness of 300-micrometers are directly deposited onto pixeled TFT substrates by the blade-coating method using the above paste, which governs a stable dark current and minimal noise of the X-ray detectors. As a result, (BA)2(MA)9Pb10I31 perovskite X-ray detectors achieved a high sensitivity of 15200 µC Gyair -1 cm-2 and a limit of detection (LoD) of 26.8 nGyair s-1. Moreover, FPXIs with a spatial resolution of 0.95 lp mm-1 (0.475 lp pixel-1) are obtained, which exhibits negligible signal crosstalk and excellent X-ray imaging performance.

Chiral-Polar Alternating Cation Intercalation-Type Perovskite Enables Sensitive Self-Driven X-ray Detection with an Ultralow Detection Limit.

Metal halide perovskites (MHPs) have shown great potential for direct X-ray detection, but achieving high sensitivity without external bias remains challenging. Chiral-polar alternating cation intercalation (ACI)-type MHPs, with excellent optoelectronic properties and a robust chirality-induced bulk photovoltaic effect (BPVE), offer a promising platform for self-driven X-ray detection. Herein, impressive self-driven X-ray detection performance was achieved by utilizing chiral-polar 2D ACI-type perovskite single crystals of (R-PPA)PAPbBr4 (1R; R-PPA = R-1-phenylpropylamine; PA = propylamine). The chiral R-PPA cations induce the crystallization of 1R in the chiral-polar space group P21, wherein its spontaneous electric polarization further induces a strong BPVE. Consequently, 1R shows remarkable radiation photovoltaics of 0.75 V, which endows its excellent self-driven X-ray detection with a high sensitivity of 417.2 μC Gy-1 cm-2 and a low detection limit of 24.1 nGy s-1, meeting the state-of-the-art level by leveraging its intrinsic photovoltaic effect. These findings highlight the huge potential of chiral-polar ACI-type MHPs in self-driven X-ray detection applications.

Gradient Distributed and Tightly Integrated Perovskite Heterojunction Constructed by Electric Field-Driven Ion Deposition for High-Performance X-ray Detection.

Perovskite heterojunctions combine the advantages of two different components but suffer difficulties in the tightness of interconnection and limitation of material selection. Here we report an electric field-driven ion deposition (EFID) strategy that controllably deposits perovskite ions on heterogeneous single crystals to form a gradient heterojunction with tight integration. The interconnection force of the gradient heterojunction by the EFID method is much better than that of the solution-grown heterojunction, which is easily decomposed. An EFID-enabled heterojunction was constructed by depositing the 3D MAPbI3 perovskite on the 2D (FPEA)2PbI4 perovskite, exhibiting an excellent X-ray sensitivity of 2.12 × 104 μC Gy-1 cm-2 under an electric field of 500 V mm-1 and a low limit of detection (LoD) less than 12.01 nGy s-1, substantially better than that of the pristine 2D or 3D counterparts. This work expands the methodology for constructing perovskite heterojunctions, offering new perspectives for future perovskite heterojunction engineering.

Structural Reconfiguration via Alternating Cation Intercalation of Chiral Hybrid Perovskites for Efficient Self-Driven X-ray Detection.

2D hybrid perovskites (HPs) have great potential for high-performance X-ray detection due to their strong radiation absorption and flexible structure. However, there remains a need to explore avenues for enhancing their detection capabilities. Optimizing the detection performance through modification of their structural properties presents a promising strategy. Herein, we explore the impact of modifying the organic spacer layer in two distinct 2D layered HPs, namely, Ruddlesden-Popper (R-MPA)2PbBr4 (R-1, R-MPA = methylphenethylammonium) and (R-MPA)EAPbBr4 (EA = ethylammonium) (R-2) with alternating cation intercalation (ACI), on their X-ray detection performance. The insertion of EA into R-2 results in a flatter inorganic skeleton, narrower spacing, and higher density compared to R-1. This structural modification effectively optimizes carrier transport and X-ray absorption in R-2, enhancing the X-ray detection performance. Notably, R-2 exhibits a polar structure with intrinsic spontaneous polarization, contributing to a bulk photovoltaic of 0.4 V. This feature enables R-2 single-crystal detectors to achieve self-driven X-ray detection with a low detection limit of 82.5 nGy s-1 under a 0 V bias. This work highlights the efficacy of the ACI strategy in structural modification and its significant effect on X-ray detection properties, providing insights for the design and optimization of new materials.

Large Scale Lead-Free Perovskite Polycrystalline Wafer Achieved by Hot-Pressed Strategy for High-Performance X-Ray Detection.

Halide perovskites (HPs) have demonstrated excellent direct X-ray detection performance. Lead-free perovskite polycrystalline wafers have outstanding advantages in large-area X-ray imaging applications due to their area-scalability, thickness-controllability, large bulk resistivity, and ease of integration with large-area thin film transistor arrays. However, currently lead-free perovskite polycrystalline wafers possess low sensitivity, typically less than 1000 µC Gy-1 cm-2, which severely limits their X-ray detection applications. Here, high-quality and large scale polycrystalline wafers of AG3Bi2I9 (AG: aminoguanidinium) with short intercluster distances are successfully prepared using a hot-pressing method. The wafers possess high mobility-lifetime product of 5.66 × 10-3 cm2 V-1 and therefore achieve high X-ray sensitivity of 2675 µC Gy-1 cm-2, which can be comparable to those of the high-quality single crystal counterpart reported by the previous research (7.94 × 10-3 cm2 V-1 and 5791 µC Gy-1 cm-2), and represent the best results of the currently lead-free HP polycrystalline wafers. Besides, the wafers exhibit the X-ray detection limit as low as 11.8 nGy s-1, excellent long-term working stability, and high spatial resolution of 5.9 lp mm-1 in imaging. The findings demonstrate that AG3Bi2I9 polycrystalline wafers are feasible for high-performance X-ray detection and imaging system.

Impact of the fiber-optic faceplate on the imaging performance of a CMOS X-ray detector

Complementary metal-oxide-semiconductor (CMOS) active-pixel detectors are widely used in various imaging applications owing to their faster operation with lower noise and higher sensitivity than their conventional amorphous silicon-based counterparts. However, CMOS detectors are vulnerable to radiation damage owing to their crystalline structures. They also suffer from ghosting artifacts and gradual reduction of dynamic range along with their lifetime. Most CMOS detectors employ a fiber-optic faceplate (FOP) between the X-ray converter and CMOS active-pixel array to mitigate the radiation effect and increase longevity. In this study, we investigated the effect of an additional FOP layer on the imaging performance of a CMOS detector, including the modulation-transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). For X-ray energies ranging from 40 to 70 kV, we measured the large-area signal-transfer functions, MTFs, and NPSs and calculated the corresponding DQEs. The FOP degraded the MTF performance over the entire spatial frequency, but improved the NPS performance with increasing spatial frequency. Consequently, the FOP layer enhanced the DQE performance for the given energy ranges. The measured results are discussed in detail using a theoretical cascaded-systems model.

Ultralow Ion Migration and X-Ray Response from Strong Dipole Moments in (Br-EA)2PbBr4 Perovskite Single Crystals.

2D hybrid perovskites composed of quantum-well structures demonstrate immense potential in optoelectronics because of their unique combination of environmental stability and optoelectrical properties. However, improving electrical properties via quantum-well engineering results in severe ion migration and inferior chemical stability. In this study, a novel strategy to avoid the above trade-off between electrical properties and stability for modifying the electric field profile in perovskites through molecular design is proposed. To this end, ethylammonium (EA) cations are substituted with 2-bromoethylamine (Br-EA) cations and fabricate pure 2D perovskite (Br-EA)2PbBr4 single crystals. The molecular dipole moments of the Br-EA cations and induced electric field impart several novel features to the X-ray response, including a ferro-response current, reverse current, and super-high Voc of 95V. The resulting X-ray detectors achieve a sensitivity of 540.7 µC Gyair -1 cm-2 with an extra 38.1% gained from local dipoles, an impressive limit of detection of 9.8 nGyair s-1, and an ultralow dark current drift of 3.69 × 10-8 nA cm-1 s-1 V-1 at -100V. This study presents valuable insights into the novel effects of dipole moments of A-site cations on the properties of perovskite materials and inspires further exploration of their potential applications.

Composição química de revestimentos frios e a influência na refletância solar e emitância térmica

Abstract Cool materials have higher values of solar reflectance and lower values of thermal emittance, although still high when compared to conventional coatings, thus, their surfaces are less heated. In this regard, the goal was to identify the chemical elements present on cool surfaces that influence solar reflectance and thermal emittance. To this end, the spectral reflectance and the thermal emittance were measured with methods and equipment standardized by the Cool Roof Rating Council (CRRC) of 23 elastomeric cool coatings commercialized in the Brazilian market, and the chemical composition of the surfaces with EDS (Energy-dispersive X-ray detector) coupled to the field emission scanning electron microscope (FE-SEM) was analyzed. The presence of the metallic chemical element (titanium) in greater quantities on the surfaces was not decisive for lower thermal emittance values. The surfaces of materials with lower carbon and higher oxygen content have higher near infrared and solar reflectance. Therefore, surfaces with a matte finish have higher solar reflectance values because of the higher ratio of pigments in relation to resin than those with a glossy finish, which are mistakenly associated with higher reflectance due to its high surface gloss.

Recent Progress in Direct X-Ray Detectors Based on Metal Oxide Wide Bandgap Semiconductors: A Review

Recent Progress in Direct X-Ray Detectors Based on Metal Oxide Wide Bandgap Semiconductors: A Review

Phase control and energy-trapping management for high quality X-ray afterglow imaging

Long-persistent radioluminescence (RL) detectors have recently attracted extensive attention in healthcare diagnostics and nondestructive inspection due to their information storage capabilities. Nevertheless, the preparation and RL mechanisms of flexible ultralong-afterglow scintillators remain unexplored. Herein, we first introduce a dopant-driven phase control strategy to greatly enhance RL intensity and X-ray afterglow duration through suppressing the nonradiative recombination pathway and manipulating electron trap distribution in CsCdCl3: Mn2+/M (M = In3+, Sb3+, Bi3+) perovskite. The photophysical studies reveal the multiple energy transfer channels in multi-exciton emissive cubic (Cub.) CsCdCl3: In3+/Mn2+ and the tunability of trap depth ranging from 0.72 to 0.78 eV. Specially, the X-ray flexible detector based on Cub. CsCdCl3: In3+/Mn2+ achieves a low X-ray detection limit of 45.2 nGyair s−1, a high spatial resolution of 12.5 lp mm−1 and X-ray extension imaging longer than 10 h. These findings provide insight into RL dynamics and optimal storage performance, thereby contributing to motivate future research in X-ray storage detector.

Element-specific X-Ray detection of electron paramagnetic resonance in thin films of quantum bits

Element-specific magnetism accessible by synchrotron-based X-ray spectroscopy has proven to be valuable to study spin and orbital moments of transition metals and lanthanides in technologically relevant thin-film and monolayer samples. The access to coherent spin superposition states relevant for emergent quantum technologies remains, however, elusive with ordinary X-ray spectroscopy. Here, we approach the study of such quantum-coherent states via the X-ray detection of microwave-driven electron paramagnetic resonance, which involves much smaller signal levels than X-ray detected ferromagnetic resonance on classical magnets. We demonstrate the feasibility of this approach with thin films of phthalocyanine-based metal complexes containing copper or vanadium centers. We also identify X-ray specific phenomena that we relate to charge trapping of secondary electrons resulting from the decay of the X-ray excited core-hole state. Our findings pave the way toward the element-specific X-ray detection of coherent superposition states in monolayers of atomic and molecular spins on virtually arbitrary surfaces.

The X-Ray Luminous Type Ibn SN 2022ablq: Estimates of Preexplosion Mass Loss and Constraints on Precursor Emission

Type Ibn supernovae (SNe Ibn) are rare stellar explosions powered primarily by interaction between the SN ejecta and H-poor, He-rich material lost by their progenitor stars. Multiwavelength observations, particularly in the X-rays, of SNe Ibn constrain their poorly understood progenitor channels and mass-loss mechanisms. Here we present Swift X-ray, ultraviolet, and ground-based optical observations of the Type Ibn SN 2022ablq, only the second SN Ibn with X-ray detections to date. While similar to the prototypical Type Ibn SN 2006jc in the optical, SN 2022ablq is roughly an order of magnitude more luminous in the X-rays, reaching unabsorbed luminosities L X ∼ 4 × 1040 erg s−1 between 0.2–10 keV. From these X-ray observations we infer time-varying mass-loss rates between 0.05 and 0.5 M ⊙ yr−1 peaking 0.5–2 yr before explosion. This complex mass-loss history and circumstellar environment disfavor steady-state winds as the primary progenitor mass-loss mechanism. We also search for precursor emission from alternative mass-loss mechanisms, such as eruptive outbursts, in forced photometry during the 2 yr before explosion. We find no statistically significant detections brighter than M ≈ −14—too shallow to rule out precursor events similar to those observed for other SNe Ibn. Finally, numerical models of the explosion of an ∼15 M ⊙ helium star that undergoes an eruptive outburst ≈1.8 yr before explosion are consistent with the observed bolometric light curve. We conclude that our observations disfavor a Wolf–Rayet star progenitor losing He-rich material via stellar winds and instead favor lower-mass progenitor models, including Roche-lobe overflow in helium stars with compact binary companions or stars that undergo eruptive outbursts during late-stage nucleosynthesis stages.

Luminescent and scintillating properties of Tb3+-doped fluoroxide glasses

Scintillator can convert ionizing radiation of high-energy ray or particle into ultraviolet/visible light, which is extensively employed for baggage screening and non-destructive testing applications. In this paper, transparent Tb3+-doped fluoroxide glass scintillators were fabricated successfully by melting quenching technique. Tb3+-doped fluoroxide glass possesses commendable luminescent properties. The optimal sample (SACNY-3Tb) has a high transmittance (87.6%@542 nm) and a suitable lifetime (2.24 ms). In addition, SACNY-3Tb has good scintillating properties. The X-ray excited luminescent intensity of SACNY-3Tb is 130% of that of Bi4Ge3O12, and 18 lp/mm of imaging resolution for X-ray can be obtained. In conclusion, the Tb3+-doped fluoroxide glass scintillator possesses potential for use within the application of steady-state X-ray detection.

Polar 3D Perovskitiod Constructed by Asymmetric Diamine for Stable Self-Driven X-Ray Detection.

Polar 3D organic-inorganic hybrid perovskites (OIHPs) with the bulk photovoltaic effect (BPVE) have important application value in self-driven X-ray detection, due to their excellent semiconductor properties. However, A-site cations are limited by the tolerance factor, making it difficult to construct ABX3-type polar 3D perovskites. Therefore, it is necessary to explore polar 3D perovskitiods with excellent semiconductor properties for self-driven X-ray detection. Herein, by introducing an asymmetric diamine 3-methylaminopropylamine (3-MAPA) cation, a polar 3D perovskitiod, (3-MAPA)Pb2Br6 (1) is successfully constructed. Specifically, the dipole-oriented arrangement and intrinsic polarity of 3-MAPA cations endow a non-centrosymmetric structure of 1 single crystal (SC). Notably, under X-ray irradiation, the polar 1 SC exhibits a remarkable bulk photovoltaic of 0.8V, which is beneficial for self-driven X-ray detection. Consequently, the 1-based detector shows a sensitivity of 101 µC Gy-1 s-1 and a low detection limit of 189 nGy s-1 at 0V bias. Meanwhile, 1 SC-based X-ray detector exhibits less ion migration due to the abundant N─H···Br hydrogen bonding interaction within the structure, leading to a smaller dark current drift, which supports stable X-ray detection. This study attains stable self-driven X-ray detection based on polar 3D perovskitiods, which enriches the candidates for self-driven X-ray detectors.

A bulk Schottky junction for high-sensitivity portable radiation detectors

The thickness of X-ray detectors needs to reach hundreds of micrometers to absorb X-ray, and therefore, high voltages over tens or hundreds of volts should be applied to extract X-ray-generated carriers. Here, we propose a bulk Schottky junction for X-ray detection using interpenetrated macroporous-carbon electrodes and metal-halide perovskite networks. The X-ray-generated holes are extracted by the macroporous-carbon electrodes under the built-in electric field, while the electrons in the perovskite phase result in a high gain effect. A high sensitivity of 1.42×105 μC Gyair−1 cm−2 and a low detection limit of 48 nGyair s−1 at a low voltage of −1 V are achieved. We fabricated a dry battery-powered portable X-ray alarm prototype. The pixel detector shows a decent stability under X-ray exposure, and a spatial resolution of up to 5.0 lp mm−1, and the detector arrays also exhibit remarkable uniformity, demonstrating its potential application in X-ray imaging.

An energy-resolving photon-counting X-ray detector for computed tomography combining silicon-photomultiplier arrays and scintillation crystals.

X-ray photon-counting computed tomography (PCCT) has garnered considerable interest owing to its low-dose administration, high-quality imaging, and material decomposition characteristics. Current commercial PCCT systems employ compound semiconductor photon-counting X-ray detectors, which offer good energy resolution. However, the choice of materials is limited, and cadmium telluride or cadmium zinc telluride is mostly used. Although indirect radiation detectors can be used as alternatives to compound semiconductor detectors, implementing fine-pitch segmentation in such detectors is challenging. Here we designed an indirect fine-pitch X-ray photon-counting detector by combining miniaturized silicon photomultiplier arrays and fast scintillation crystals, with a pixel size of 250 µm, for future indirect PCCT. The fabricated array detector has the potential to discriminate photon energies with a 27% resolution at 122 keV, 296 µm spatial resolution, and charge-sharing inhibition ability.

Calibration of the Solar X-ray Detector on-board the Macao Science Satellite-1B for Soft X-ray Detection

Calibration of the Solar X-ray Detector on-board the Macao Science Satellite-1B for Soft X-ray Detection