As the Energy-velocity (E-(v) mass spectrometer garners increasing attention, researchers have observed that the temporal resolution of time-of-flight detectors has become a limiting factor in ...enhancing the detection efficiency of E-v devices. Consequently, this necessitating higher time-resolution requirements for these detectors. SED-MCP, or Secondary Electron Time Detector based on Micro-Channel Plate, is a type of detector capable of accurately measuring the flight time of particles without significantly interfering with their motion. In this study, we optimized the design parameters of SED-MCP through electron optical simulation and achieved a secondary electron flight time spread of less than 20 ps. Furthermore, we established a digital electronic system and a scaling-free digital timing method to minimize timing uncertainties and improve detection efficiency. As a result of these efforts, a SED-MCP with an intrinsic time resolution of 57 ± 5 ps was developed. This resolution surpasses those of similar detectors used in E-v mass spectrometers and holds substantial significance for improving the mass resolution and detection efficiency of the E-v mass spectrometer.
In the scope of solar cell characterisation, spatially resolved imaging (SRI) methods (EL, PL and LBIC) have long been a standard procedure for valuable in-depth evaluation and extraction of various ...spatially resolved material properties, especially those related to the electrical behaviour. While this extraction can be straightforward in the case of laterally homogeneous devices, the situation is vastly different when the structural features are laterally varying, such as in the case of interdigitated back contact (IBC) solar cells. We show that in the case of laterally varying devices inherent device optical properties play a far more important role in determining the measured profile in this case and may indeed overshadow any underlying electrical effects. We therefore propose and validate a methodology that couples SRI characterisation with advanced bottom-up simulation of IBC solar cells. The method fully accounts for lateral device variability and allows for accurate extraction of the underlying electrical phenomena. We demonstrate the applicability of the method on state-of-the-art high-efficiency IBC solar cells, and explain the key factors, which could lead to misinterpretation of the results obtained solely by SRI measurements.
•Interpretation of measured IBC electroluminescence profiles through opto-electrical simulation.•Decoupling of underlying optical and electrical phenomena.•Device optics overshadows recombination driven fluctuations of luminescence profiles.•Rear interface strongly influences the shape of the extracted luminescence profile.•Shape of the luminescence profile is highly dependent on imaging system’s aperture.
The risk of vacuum loss in linear solar heat collection elements (HCEs) is one of the major practical challenges that are facing the parabolic trough solar concentrator (PTSC) systems in ...concentrating solar power (CSP) plants. Despite the long-life span of CSP systems, HCEs are frequently replaced due to permeated hydrogen (due to saturation of getters) or leaked air (due to failures in end metal-to-glass welding or cracked glass shells). This study proposes a low-tech solution for boosting the performance of PTSCs with partial or lost vacuum through rotating the HCEs. A carefully validated integrated 3D optical-thermal model is developed and used to quantify the energetic and exergetic performances of PTSCs with rotated and fixed HCEs for both cases of lost and maintained vacuum. Both steady and unsteady simulations are reported using high-precision ground measurements of direct irradiance and meteorological parameters. As the rotational speed increases from 0 to 20 rad/s, the energy efficiency of PTSCs with new and damaged HCEs is improved by ∼47 and 52%, respectively, at a Reynolds number of 4000 and an inlet temperature of 350 °C. By rotating a damaged HCE at only 10 rad/s, maximum improvements of ∼26 and 53% in the useful heat gain are obtained, compared to non-rotating evacuated and non-rotating damaged HCEs, respectively, at the same operating conditions. Overall, the advantage of the proposed concept is more pronounced when the PTSC is operating at relatively low flow rates, high temperatures, or under high irradiance levels.
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We report on high-quality InGaAs/GaAs multi-quantum well waveguide photodetectors, monolithically integrated through metalorganic vapor-phase selective-area epitaxial growth and contact metallization ...in a 300-mm CMOS pilot line. The photodetectors are implemented using the nano-ridge engineering concept, leveraging aspect-ratio trapping in combination with precise control of the nano-ridge cross section dimensions and composition. The InGaAs/GaAs p-i-n nano-ridge photodetectors are shown to achieve high internal responsivities of up to 0.65 A/W at −1 V bias and 1020 nm wavelength. A clear correlation is observed between measured responsivity and contact-plug design, correlating well with simulation models. In addition, a record-low dark current density of 1.98 × 10 −8 A/cm 2 and low absolute dark currents of <1 pA are demonstrated, illustrating the high quality of the III-V materials and effective in-situ InGaP surface passivation layers. Initial RF measurements suggest RC-limited photodetection bandwidths in the GHz range. These results illustrate the strong potential of the III-V/Si nano-ridge epitaxy and waveguide device concept, to complement the Silicon Photonics toolbox with high-quality, high-throughput III-V functionality.
In this paper, an annular Fresnel solar concentrator (AFSC) is proposed. This novel concentrator was incorporated with a series of annular mirrors, and its performance was simulated using MATLAB ...software. The influences of different structures were also simulated. The tracking deviation, device deviation, and comprehensive deviation were analysed using different deviation angles. The results demonstrated that this concentrator could simply adjust the concentrating ratio, which reached 300 when the maximum concentrator height was 0.78 m and the maximum diameter was only 1.72 m. Non-linear changes in the performance of the annular Fresnel reflector occurred when the structure size increased linearly. Further, the radiation distribution and performance of the annular Fresnel reflector were found with different deviations. When the tracking deviation angle was 0.5°, the receiving rate was 98.37%. This new AFSC has excellent concentrated solar power (CSP) application prospects.
•This paper designs one high concentrated solar concentrator with annular Fresnel method.•The performance with different structure parameters is analysed.•The tracking deviation, device deviation and comprehensive deviation are analysed.
Passive daytime radiative cooling (PDRC) devices have enabled subambient cooling of terrestrial objects without any energy input, offering great potential to future clean energy technology. Among ...various PDRC structures, random dielectric particles in a polymer matrix or paint-like coatings have displayed powerful radiative cooling performances with excellent scalability and easy fabrication. While modeling and analyzing such a system is nontrivial to enhance the cooling effect and engineer the structures to be utilized in various applications, it is essential to understand its complex physical relations and determine the optimal design conditions. In this work, we have thoroughly analyzed the optical properties and radiative cooling performances of PDRC paints composed of two-material particles (SiO2 and Al2O3) using 2D FDTD simulation and investigated the optimal design conditions. Specifically, we have studied the effects of design parameters, such as particle size, size distribution, binder volume ratio, and coating thickness. Subsequently, we have conducted an outdoor cooling measurement of the fabricated PDRC paints to demonstrate their radiative cooling potential and to analyze and understand their performance based on our numerical investigations. The fabricated PDRC paints exhibited high solar reflectance (0.958) and strong long-wave infrared emission (0.937) in the atmospheric transparency window, achieving a maximum temperature drop of 9.1 °C. This comprehensive study provides a detailed characterization of the structure and material parameters of the multimaterial PDRC paint system.
In the context of simulating precision laser interferometers, we use several examples to compare two wavefront decomposition methods—the Mode Expansion Method (MEM) and the Gaussian Beam ...Decomposition (GBD) method—for their precision and applicability. To assess the performance of these methods, we define different types of errors and study their properties. We specify how the two methods can be fairly compared and based on that, compare the quality of the MEM and GBD through several examples. Here, we test cases for which analytic results are available, i.e., non-clipped circular and general astigmatic Gaussian beams, as well as clipped circular Gaussian beams, in the near, far, and extremely far fields of millions of kilometers occurring in space-gravitational wave detectors. Additionally, we compare the methods for aberrated wavefronts and their interaction with optical components by testing reflections from differently curved mirrors. We find that both methods can generally be used for decomposing non-Gaussian beams. However, which method is more accurate depends on the optical system and simulation settings. In the given examples, the MEM more accurately describes non-clipped Gaussian beams, whereas for clipped Gaussian beams and the interaction with surfaces, the GBD is more precise.
Aiming at the problem of gas holdup measurement in horizontal shale gas wells with low flow rates, a fiber-optic probe array sensor for horizontal gas-liquid stratified flow is designed and ...developed. The Fluent fluid volume method is used to establish a simulation model of gas-liquid two-phase flow in the horizontal collecting pipe, and a study on the flow characteristics and flow patterns in the gas-liquid two-phase flow in the horizontal collecting pipe with low gas flow is carried out. Based on the acquisition of the fluid flow pattern is stratified flow characteristics, the design of the fiber-optic probe array structure with different numbers and positions of the probes, and the fiber-optic probe array sensor is modeled using the ZEMAX ray tracing software, simulation analysis of its response characteristics in different flow patterns and the array structure selection. Finally, based on the above research, the fiber-optic probe array sensor for gas holdup measurement is designed and developed, and the platform for gas-liquid two-phase flow is constructed and experimentally verified. The experimental results show that the developed fiber-optic probe array sensor has good applicability for gas holdup measurement under stratified flow, and the error of the measurement does not exceed 0.1.
•Research on the flow pattern of horizontal gas-liquid two-phase flow under gas flow velocity ranges from 2.36 × 10−5 m/s to 2.21 × 10−2 m/s, and liquid flow velocity ranges from 2.36 × 10−5 m/s to 2.21 × 10−2 m/s.•The effects of the fiber-optic probe array structure on its measurement performance were discussed.•The software ZEMAX is used to conduct and gas holdup response experiments on the two optimized array structures.•We developed the fiber-optic probe array prototype and built a multi-phase flow experimental platform.
Transparent ceramics are a kind of optical materials which have a wide range of applications in various engineering sectors, including the medical devices (implants, anti-wear coatings), cars, ...smartphones (anti-wear and shockproof plates), watches (anti-wear and anti-shock lenses with high strength), optical lenses, etc. Control of various parameters like the volume fraction of secondary phase, the grain size of the main and secondary phase, and the number of pores in unit volume, which affect the absorption, reflection and finally the transparency of ceramics, is a vital issue. Studying the physical aspects besides applying the principles of simulation is a very efficient way to achieve this aim. Simulation of the behavior of ceramics helps to attain optimized parameters. Therefore, to accomplish an optical ceramic with prominent transparency and admissible transmittance in selective wavelengths, the appropriate simulation theory should be used. In this paper, first, the physical basis of optical ceramics including band gaps, absorption, reflection, diffraction, refractive index, refraction, dispersion, etc., are briefly presented. Additionally, different simulation theories are reviewed and discussed.
•Critical reviewing of basic requirements for optically transparent ceramics.•Introducing the most important factors, which affect the transparency of ceramics.•Comparing the scattering theories presented to investigate the transparency of the ceramics.
A PTC (parabolic trough solar collector) focuses direct solar radiation reflected by the reflector onto a receiver located on its focal line. The solar flux distribution on the absorber is ...non-uniform generally, thus it needs to carry out optical simulation to analyze the concentrated flux density and optical performance. In this paper, three different optical models based on ray tracing for a PTC were proposed and compared in detail. They were proved to be feasible and reliable in comparison with other literature. Model 1 was based on MCM (Monte Carlo Method). Model 2 initialized photon distribution with FVM (Finite Volume Method), and calculated reflection, transmission, and absorption by means of MCM. Model 3 utilized FVM to determine ray positions initially, while it changed the photon energy by multiplying reflectivity, transmissivity and absorptivity. The runtime and computation effort of Model 3 were approximately 40% and 60% of that of Model 1 in the present work. Moreover, the simulation result of Model 3 was not affected by the algorithm for generating random numbers, however, it needed to take account of suitable grid configurations for different sections of the system. Additionally, effects of varying the geometric parameters for a PTC on optical efficiency were estimated. Effect of offsetting the absorber in width direction of aperture was greater than that in its normal direction at the same offset distance, which was more obvious with offset distance increasing. Furthermore, absorber offset at the opposite direction of tracking error was beneficial for improving optical performance. The larger rim angle (≤90°) was, the less sensitive optical efficiency was to tracking error for the same aperture width of a PTC. In contrast, a larger aperture width was more sensitive to tracking error for a certain rim angle.
•Three different optical models for parabolic trough solar collectors were derived.•Their running time, computation effort, and characteristics were compared.•It can analyze optical performance of a PTC (parabolic trough solar collector).•Effects of varying PTC's geometric parameters on optical efficiency were estimated.•The simulated results were essential for optimizing the PTC's geometric parameters.
