Charge-coupled Device Research Articles

A method for estimating the incident directions of alpha particles in 2-dimensional trajectory images in a GAGG plate

An imaging technique utilizing a scintillator plate in conjunction with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera shows promise for capturing high-resolution trajectory images. Nevertheless, in the 2-dimensional trajectory images, the incident directions of the alpha particles entering the scintillator plate remained unknown due to the line-shaped trajectories. To elucidate the incident directions in our trajectory images, we conducted experiments capturing trajectory images of alpha particles under off-focus conditions. To capture off-focus images of alpha particles, we systematically varied the distance between the GAGG plate and the lens during imaging using an americium-241 (Am-241) source. Through images obtained at different distances between the GAGG plate and the lens, we successfully acquired trajectory images with varying degrees of off-focus, revealing that trajectory images focused on the upper surface of the GAGG plate exhibited blurred and wider trajectories in the deeper regions, making the incident directions of the alpha particles evident. We conclude that the proposed off-focus method for trajectory imaging of alpha particles holds promise for estimating the incident directions in the trajectory images.

A two-stage framework for pixel-level pavement surface crack detection

Surface crack is one of the most common distresses of pavement structure, impacting its serviceability and sustainability. Over the past decade, many efforts have been devoted to developing computer vision-based models (e.g., image processing- or deep learning-based) for the automatic detection of pavement surface crack. However, there is a great gap between the public image data taken by the phone or other portable devices and the real-world image data acquired by the linear array charge-coupled device (CCD) camera, which usually is high resolution and contains limited crack pixels per image. To improve the pavement surface crack detection efficiency and accuracy in engineering practice, we propose a novel two-stage framework for automatic pavement surface detection at the pixel level. In stage I, the images concluding pixel cracks are selected using a convolutional neural network (CNN)-based classification network. In stage II, the selected images are processed with our proposed separation-combination strategy and the second version of crack transformer (CTv2) for pavement surface crack detection at the pixel level. Comprehensive experimental investigation and comparison have been conducted on training performance and visualization results, validating the superiority of the developed framework. It paves the way for the large-scale application of automatic pavement crack detection in an efficient manner.

Stokes vector characterization by strongly measuring weak values.

We report the implementation of a non-standard procedure to perform Stokes polarimetry, which was recently proposed by considering weak value measurements. Our procedure is not restricted to weak measurements but applies for both weak and strong couplings between the observable being measured; the polarization (spin) vector; and the measuring device, the "pointer." In optics, the polarization-pointer coupling is usually implemented with a birefringent crystal. This applies in the weak coupling regime. We overcame this limitation by using an alternative setup in which one can go from weak to strong couplings by tuning a moveable mirror. We carried out our proof-of-concept experiments with a laser beam, the image of which was recorded and processed on a charge-coupled device. Our results illustrate that some concepts, originally introduced in a quantum context, in fact refer to properties that are common to both quantum and classical phenomena.

Evolution of solid-in-hollow structured plasma bullet: Modulated by pulse repetition frequency and rising time

Plasma bullets in atmospheric pressure plasma jets have drawn much scholarly attention in the past decade, especially its shape. This Letter reports the formation and evolution mechanism of a solid-in-hollow structured bullet. At high pulse repetition frequency (≥20 kHz) and long rising time (≥200 ns), the traditional hollow ring bullet turns into the solid-in-hollow structure, and the plasma plume correspondingly appears as a purple external plume with an extra internal filamentary red core under bare eyes. An image process method based on color recognition and decoupling is designed to separate the images of the external plume and the internal filamentary core and is then used to analyze the discharge mechanism together with the intensified charge-coupled device imaging and spectrum measurement. Analyses reveal that the dominant ionization sources for external ring and internal core are N2 and He, respectively, and the internal discharge can be enhanced by increasing the pulse repetition frequency, which might be explained by the electron oscillating heating in high frequency. Finally, the evolution mechanism of the internal filamentary core is studied, and the internal discharge is initially a hollow ring as well when it just exits the tube end, making the bullet a hollow-in-hollow structure, but quickly contracts into a solid core due to the Coulomb repulsion between the two plasma rings.

Enhanced Performance in Cesium Tellurium Chlorine by Hafnium Alloying for X‐Ray Computed Tomography Imaging

AbstractThe term “light yield” (LY) refers to the ability of scintillator materials to convert high‐energy radiation into visible light. A higher LY corresponds to improved energy and spatial resolution in detectors. The enhancement of scintillator material performance is a crucial aspect of their development. In this study, the Cs2TeCl6 (CTC) double perovskite microcrystals is synthesized, and the broadband yellow emission shows a high degree of matching with the Charge‐coupled Device (CCD). However, the LY of CTC is poor for practical applications in X‐ray imaging. The scintillation performance is significantly enhanced through hafnium alloying. The LY increased from ≈4167 to 38 523 photons/MeV, and the detection limit decreased from 948 to 258 nGy s−1. The underlying mechanism of Te4+ ions emission is systematically explored through density function theory (DFT) analysis, along with investigations into pressure‐dependent photoluminescence, temperature‐dependent photoluminescence, and low‐temperature thermoluminescence. Furthermore, a flexible X‐ray scintillator screen with an outstanding high spatial resolution of 15.9 lp mm−1 is successfully fabricated. This work not only represents a substantial advancement in the scintillation performance of Te4+ ions emission double perovskite microcrystals but also provides an effective strategy for the development of the next generation of halide scintillators.

Penning micro-trap for quantum computing.

Trapped ions in radio-frequency traps are among the leading approaches for realizing quantum computers, because of high-fidelity quantum gates and long coherence times1-3. However, the use of radio-frequencies presents several challenges to scaling, including requiring compatibility of chips with high voltages4, managing power dissipation5 and restricting transport and placement of ions6. Here we realize a micro-fabricated Penning ion trap that removes these restrictions by replacing the radio-frequency field with a 3T magnetic field. We demonstrate full quantum control of an ion in this setting, as well as the ability to transport the ion arbitrarily in the trapping plane above the chip. This unique feature of the Penning micro-trap approach opens up a modification of the quantum charge-coupled device architecture with improved connectivity and flexibility, facilitating the realization of large-scale trapped-ion quantum computing, quantum simulation and quantum sensing.

Exploring diamond multigate FET for next generation three-phase CCD

The escalating demand for imaging devices operating in harsh environments has prompted investigations into the applicability of diamond, often called the ultimate semiconductor material. A multigate field effect transistor (FET) is a crucial component of Charge-Coupled Devices (CCDs) for imaging devices, and we developed it on a hydrogen-terminated diamond (H-diamond) for the first time. This milestone not only showcased the potential realization of diamond CCDs but also provided key insights for future research. Specifically, this paper explores the electrical and structural needs to achieve signal transmission throughout the fabricated diamond multigate FET.

Error Analysis for Rotating-drift-scan Charge-coupled Device Observation of Near-Earth Asteroids

The apparent velocities of near-Earth asteroids (NEAs) are usually high when they pass by Earth. Observing these fast-moving objects with long exposure times would cause their images to streak and significantly decrease the precision of astronomical measurements. The rotating-drift-scan (RDS) charge-coupled device technique is a promising approach to observe fast-moving NEAs during their close approaches to Earth. By rotating the camera of a telescope, an NEA can be observed in the time delay integration mode. This allows the asteroid to be imaged as a point source, even with a long exposure time. Here, we thoroughly present the RDS follow-up observation and orbit determination of a newly discovered NEA 2023 BJ7. This technique makes an impactful contribution to improving the NEA's orbit accuracy by extending the observation arc. A detailed statistical analysis of the astrometric error was conducted, revealing that RDS observations can achieve a competitive accuracy with an rms error of 0.″24 in right ascension and 0.″32 in declination. The instability of the telescope is thought to be the main reason affecting the internal precision. Furthermore, the RDS technique excels at observing fast-moving NEAs, as well as newly discovered NEAs without accurate ephemerides. For NEAs with rates of motion exceeding 10 deg day−1, the rms of RDS observation residuals is 0.″35 in the along-track direction and 0.″23 in the cross-track. With this technique, a network of small-aperture telescopes would substantially benefit our global NEAs monitoring system to ensure Earth’s safety from any asteroid impacts.

Fast breakdown process and characteristics diagnosis of nanosecond pin–pin discharge

In this paper, the characteristics of a nanosecond spark discharge with a pin–pin electrode configuration have been systematically studied. Both a streak camera with high temporal resolution and an intensified charge-coupled device (ICCD) camera are employed together to investigate the breakdown and evolution process of the discharge. The formation of initial breakdown and mode transition from streamer to spark in the electrode gap are clearly observed on the time scale of several nanoseconds with a temporal resolution of 100 ps. In addition, the time-resolved spectra technology is also used to analyze the generation and quenching mechanisms of reactive species, the electron density, and the electron temperature. The results show that there is a 1.25 ns initial discharge breakdown and that a bright cathode spot exists before the transformation from streamer to spark channel. After a faster cathode filament and a slower anode filament propagate and merge at the electrode gap, the spark discharge phase begins. The generation processes of different reactive species depend on the discharge phase to a great extent. The N2* is first generated during the streamer phase while the O*, N*, and N+ are mainly generated under the spark phase, in which the electron temperature calculated by Boltzmann plots is 2.74 eV, and the electron density determined from the Stark broadening of O lines is on the order of 1016 cm−3.

Intermittent discharge in a complex stripe pattern in dielectric barrier discharge

The intermittent discharge that filament only discharges once in a cycle rather than once every half-cycle is observed in all the three substructures of the (bright spots)–(dark spots)-halo stripe pattern (BDHSP) in dielectric barrier discharge. The discharge characteristics are investigated by a high-speed video camera, an intensified charge-coupled device camera, and two photomultiplier tubes. It is found that the direction of the stripe choose to form in BDHSP is determined by the direction in which the surface discharge is stronger in the square pattern. The spatiotemporal dynamics results of BDHSP suggest that bright spot (B) discharges in this half-cycle, and the dark spot (D) and the halo (H) discharge in the next half-cycle of the applied voltage, which is intermittent discharge. Combined with the analysis in the electric field simulation, it can be concluded that the intermittent discharge is the result of the mutual influence between the directional selective surface discharge induced by bright spots and dark spots. Overall, the BDHSP is formed by the self-organization of the wall charge under the interaction between the plasma physical processes and the spatial distribution. The discovery of the intermittent discharge provides insight and enlightenment for the study of plasma physics.

Experimental investigation on dynamic characteristics of single bubble near wall in shear flow

The bubble near the wall of shear flow will be subjected to both wall-induced lift and shear-induced lift. The two-lift interaction will markedly change the dynamic behavior of the bubble. In this experiment, the lateral motion of a single bubble (deq=2.33−3.42 mm, Reb=470−680) rising near the vertical wall in a linear shear flow was studied. The positive-synergy and negative-synergy between the wall- and shear-induced lift effects on bubble dynamics were compared. The experiment was carried out in a vertical water tunnel with a curved screen used to generate a stable linear shear flow. Using the shadow method and two charge-coupled device cameras, the movement parameters of the bubble were captured, including the movement trajectory of the bubble, length–diameter ratio, and instantaneous velocity. The lift coefficient CL and drag coefficient CD were obtained by quasi-steady-state analysis and calculation. By fitting the steady lift coefficient, the relation of CL with dimensionless wall distance S* and the Reynolds number Reb was obtained. The results show that there is a critical value of the initial dimensionless distance S* about [S*] = 1.6. When S* > [S*], the bubble is subjected to both wall-induced lift and shear-induced lift. The lift coefficient CL decreases with the increase in S*. When S* < [S*], the bubble receives additional induced lift from the wall. The CL of the smaller bubble was smaller and increases with the increase in S*, while the deformation of the larger bubble will interact with the wall to produce deformation lift away from the wall, presenting larger CL, and decrease with the increase in S*.

Automatic detection system for steel skeleton size based on machine vision.

Currently, most buildings are constructed using prefabricated concrete slabs supported by a steel skeleton that is generally tied and welded manually. However, if the overall size of the skeleton is incorrect and this error is not noticed before the concrete is poured, then a huge waste is incurred by having to scrap all the prefabricated slabs. Therefore, we propose an automatic system for measuring the frame size needed for prefabricated slabs made of reinforced concrete using LabVIEW and the NI Vision library of machine-vision functions to perform image processing and machine-vision detection. A charge-coupled device camera obtained an overall image, and then, LabVIEW processed the image and extracted its features. The system compared the measured size with the design size and issued a warning if the two differ by more than 0.5cm. From experimental comparison and verification, the maximum measurement error between the test results and the actual size was 2.7% and the root mean square error was 0.66%. This meets the requirements of actual site construction and provides a scientific reference for realizing the automatic detection of the skeleton size for reinforced-concrete precast slabs.

Recovery of polarization entanglement in partially coherent photonic qubits.

Partially coherent photonic qubits, owing to their robustness in propagation through random media compared to fully coherent qubits, find applications in free-space communication, quantum imaging, and quantum sensing. However, the reduction of spatial coherence degrades entanglement in qubits, adversely affecting entanglement-based applications. We report the recovery of entanglement in the partially coherent photonic qubits generated using a spontaneous parametric downconversion process despite retaining their multimode nature. This study utilizes an electron multiplying charge-coupled device (EMCCD) to perform coincidence measurements, eliminating the need for raster scanning of single-pixel detectors, which simplifies optical alignment, enhances precision, and reduces time consumption. We demonstrate that the size of apertures used to select biphotons substantially impacts the visibility and S-parameter of polarization-entangled partially coherent qubits. The entanglement is recovered with partial spatial coherence properties by choosing small sizes of the apertures in the captured image plane. This study could help in the advancement of free-space quantum communication, quantum imaging, and quantum metrology.

Experimental study on the structure and propagation of the stretched hydrogen-rich turbulent premixed flames in the thin-reaction-zone regime

An experimental study on the structure and propagation of the stretched hydrogen-rich premixed turbulent flames in the thin-reaction-zone regime was conducted. A set of optical diagnostic techniques including the 2D/3D-particle image velocimetry, hot wire anemometer, intensified charge-coupled device (ICCD), and laser tomography visualization (LTV) methods were adopted to quantitatively measure the velocity field, turbulent intensity, and thickness of the stretched flame of the under various conditions. A new method to improve the measurements of the flame preheat zone thickness was developed by using the low-temperature available LTV method to identify the onset of the preheat zone and using the peak location of CH* to identify the reaction zone. The results showed that the flow field was in the inertial turbulent subrange and the turbulent flames obtained in the present counterflow configuration were categorized into the thin reaction zone regime in Borghi/Peters turbulent flame diagram. The experimental results showed that the flame structure of a turbulent H2-rich premixed flame was synergistically influenced by the hydrodynamic stretch, turbulence, and preferential diffusion. New evidence of the phenomenon accumulated that large-scale vortices wrinkled the surface of the flame while small-scale vortices penetrated into the flame preheat zone. Scaling laws for the turbulent flame propagation speed, apparent turbulent thermal conductivity, and were given with the consideration of the synergetic effect of hydrodynamic stretch, turbulence, and preferential diffusion. The scaling of the turbulent flame preheat zone thickness turned out to be sensitive, while those of the turbulent flame propagation speed and apparent turbulent thermal conductivity were insensitive, to the bulk flow strain rate.

Conformal Broad‐Spectra Laser Sensing Array from Ferroelectric Polymer Composites

AbstractPhotoelectric sensors based on charge‐coupled device (CCD) and complementary‐metal‐oxide‐semiconductor (CMOS) used to be planar image sensors due to the rigidity of the base materials. Moreover, they are limited to a narrow reaction wavelength range. Here, a conformal broad‐spectra laser sensor based on a flexible metal‐ferroelectric‐metal photocapacitor is promoted. The photocapacitance signal is attributed to the photothermal effect of copper (Cu) electrode and gold nanoparticles (Au NP), and the temperature‐dependent property of the dielectric constant of poly(vinylidene fluoride‐trifluoroethylene) (PVDF‐TrFE). Cu/PVDF‐TrFE/Cu and Cu/Au NP@PVDF‐TrFE/Cu flexible photocapacitors have a reliable photocapacitive response from −60 to 60 °C. Meanwhile, both photocapacitors respond from 265 to 980 nm due to the absorption of light by the composite structure, which can be used for broad‐spectra photodetection. The addition of a small amount of Au NP (0.05 vol%) effectively improves the photoresponsiveness of the device. Real‐time photodetection is realized on a hemispherical surface, and these photocapacitors with conformal characteristics are expected to gain application in an omnidirectional broad‐spectra laser alarming system.

Rapid exchange cooling with trapped ions

The trapped-ion quantum charge-coupled device (QCCD) architecture is a leading candidate for advanced quantum information processing. In current QCCD implementations, imperfect ion transport and anomalous heating can excite ion motion during a calculation. To counteract this, intermediate cooling is necessary to maintain high-fidelity gate performance. Cooling the computational ions sympathetically with ions of another species, a commonly employed strategy, creates a significant runtime bottleneck. Here, we demonstrate a different approach we call exchange cooling. Unlike sympathetic cooling, exchange cooling does not require trapping two different atomic species. The protocol introduces a bank of “coolant" ions which are repeatedly laser cooled. A computational ion can then be cooled by transporting a coolant ion into its proximity. We test this concept experimentally with two 40Ca+ ions, executing the necessary transport in 107 μs, an order of magnitude faster than typical sympathetic cooling durations. We remove over 96%, and as many as 102(5) quanta, of axial motional energy from the computational ion. We verify that re-cooling the coolant ion does not decohere the computational ion. This approach validates the feasibility of a single-species QCCD processor, capable of fast quantum simulation and computation.

Functional characterization of polymeric organic scintillation material for preclinical imaging applications.

This study is aimed at evaluating scintillating plastic blocks with scintillation characteristics matching a highly efficient charge-coupled device (CCD) for preclinical nuclear/radioisotopic imaging. A composite layer formed with an array of plastic blocks is operated as an image collection device. The scintillating layer used four EJ 204 plastic scintillators attached to a 3D-printed supporting piece made from polylactic acid and made up by using an additive manufacturing developing strategy. An image processing algorithm was developed in MATLAB to characterize the response of the scintillation material and to obtain the distribution of radioactive samples in bi-dimensional images. To obtain functional images, a set of correction techniques to reduce scattered radiation was implemented in the collected images. By integrating the radiation detection stage with a robotic rotation system, a three-dimensional reconstruction of a murine model was obtained. The reconstructed preclinical image was overlayed with an X-ray to obtain a functional-anatomical visualization of the radio-pharmaceutical 99mTc-RGD in the studied murine model. The assessed polymeric organic blocks are competitive to professional nuclear/radioisotopic imaging scintillators considering the obtained temporal response and the imaging captured information.

A comparative study of EM-CCD and CMOS cameras for particle ion trajectory imaging

High-resolution and real-time imaging of particle ion trajectories is essential in nuclear medicine and nuclear engineering. One potential method to achieve high-resolution real-time trajectory imaging of particle ions involves utilizing an imaging system that integrates a scintillator plate with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera. However, acquiring an EM-CCD camera might prove challenging due to the discontinuation of CCD sensor manufacturing by vendors. As an alternative imaging approach, a low-noise, high-sensitivity camera utilizing a cooled complementary metal-oxide-semiconductor (CMOS) sensor offers a promising solution for imaging particle ion trajectories. Yet, it remains uncertain whether CMOS-based cameras can perform as effectively as CCD-based cameras in capturing particle ion trajectories. To address these concerns, we conducted a comparative analysis of the imaging performance between a CMOS-based system and an EM-CCD-based system for capturing alpha particle trajectories. The results revealed that both systems could image the trajectories of alpha particle, but the spatial resolution with the CMOS-based camera exceeded that of the EM-CCD-based camera, primarily due to the smaller pixel size of the sensor. While the signal-to-noise ratio (SNR) of the trajectory image from the CMOS-based camera initially lagged behind that from the EM-CCD-based camera, this disparity was mitigated by implementing binning techniques on the CMOS-based camera images. In conclusion, our findings suggest that a cooled CMOS camera could serve as a viable alternative for imaging particle ion trajectories.

Fundamental probing limit on the high-order orbital angular momentum of light.

The orbital angular momentum (OAM) of light, possessing an infinite-dimensional degree of freedom, holds significant potential to enhance the capacity of optical communication and information processing in both classical and quantum regimes. Despite various methods developed to accurately measure OAM modes, the probing limit of the highest-order OAM remains an open question. Here, we report an accurate recognition of superhigh-order OAM using a convolutional neural network approach with an improved ResNeXt architecture, based on conjugated interference patterns. A type of hybrid beam carrying double OAM modes is utilized to provide more controllable degrees of freedom for greater recognition of the OAM modes. Our contribution advances the OAM recognition limit from manual counting to machine learning. Results demonstrate that, within our optical system, the maximum recognizable OAM modes exceed l = ±690 with an accuracy surpassing 99.93%, the highest achieved by spatial light modulator to date. Enlarging the active area of the CCD sensor extends the number of recognizable OAM modes to 1300, constrained only by the CCD resolution limit. Additionally, we explore the identification of fractional high-order OAM modes with a resolution of 0.1 from l = ±600.0 to l = ±600.9, achieving a high accuracy of 97.86%.

Spatial infiltration and redistribution of light crude oil in heterogeneous water-bearing soil layers under different hydrogeological processes.

Two physical models were used to simulate the infiltration and redistribution process of light crude oil after leakage in a heterogeneous soil layer following water level variation and rainfall. Migration fronts and redistribution characteristics of oil during gravity seepage, water level variation, and rainfall were obtained using charge-coupled device (CCD) camera shooting and cyan-magenta-yellow‒black (CMYK)-based gray analysis, which were employed efficiently and at a low cost. Then, the influencing factors and migration mechanisms were examined. Finally, the soil water and oil contents were measured to verify the simulation results. The results are as follows: (1) the geologic lens and fine-coarse interface can intercept oil, resulting in a local highly contaminated area. (2) The crude oil infiltration path and velocity varied greatly with the different soil types and initial water contents. Within a certain range, the higher the initial water content is, the higher the lateral and vertical infiltration speeds. (3) The oil redistribution process was dominated by vertical infiltration under the condition of water level variation or rainfall, but oil-water displacement and the capillary pressure caused some oil to move horizontally near the geologic lens and fine-coarse interface. (4) Water level variation resulted in a synchronous rise or fall of the oil accumulation area, but rainfall caused it to move up. (5) Water level variation and rainfall imposed a certain influence on the periodic accumulation and release of crude oil in heterogeneous soil, especially in the presence of geologic lenses and lithologic interfaces.