The multi-beam electron optical system (MBEOS) is critical for high-throughput electron microscopy and electron beam lithography. However, their performance is constrained by both on-axis and off-axis aberrations, which significantly degrade the final spot size. A systematic approach to control these aberrations and to optimize the overall system design has not yet been fully addressed. In this work, we extend the analytical model proposed by M. J. van Bruggen to develop a simplified method for rapidly determining the optimal operating conditions-specifically, the beam deflection angle at the field lens (an intermediate accelerating lens) and the corresponding field lens strength-that minimize off-axis aberrations in a two-lens demagnification system. Our results reveal that the minimum total aberration occurs when the beamlets pass very close to, rather than exactly through, the center of the second lens. Furthermore, we observe a non‑monotonic relationship between off‑axis aberration and the beamlet's radial distance to the optical axis at the field lens. As this radial distance increases, the aberration first decreases and then increases. After geometric aberrations are minimized, spherical and chromatic aberrations become the dominant contributors to the final spot size. Based on these insights, we propose a practical optimization routine applicable to MBEOS designs employing two-lens demagnification system. Using this method, we demonstrate that a total usable beamlet generation area of up to 480 µm × 480 µm can be achieved while maintaining a spot size near 10 nm. This work provides a practical analytical framework for designing high-performance MBEOS with minimized off-axis aberrations.

To mitigate the impact of positive ions and metal splatters on the signal-to-noise ratio and lifespan of the reflected electron detector during electron beam welding, a four-grid reflected electron detector with a high signal-to-noise ratio and a reflecting surface was designed by using the Monte Carlo method and multi-physics simulation software. The entire process of signal reception by the detector was simulated, and the influence of its structural parameters on the collection efficiency of reflected electron signals was investigated. The simulation results show that under an accelerating voltage of 60 kV and a working distance of 200 mm, the detector achieves the optimal collection efficiency of 2.73% when the reflecting surface tilt angle is 165°, and the collection surface tilt angle is 105°. When the reflecting surface tilt angle (α) and collection surface tilt angle (β) are fixed, the collection efficiency decreases with an increase in the working distance (h). Experimental results verify the simulation results and are compared with metal plate detectors’ imaging results, demonstrating that this reflected electron detector improves the image contrast by 38.8%. The reflected electron detector can also clearly identify tungsten mesh samples with a wire diameter of 100 μm

Conventional homogeneous wettability surfaces rely on macroscopic chemical and topographical uniformity, thereby exhibiting only a single, passive functionality.

The electron gun is a critical component of the X-ray source in X-ray photoelectron spectroscopy (XPS) systems, responsible for generating and directing an electron beam to the target from which X-rays emit. Precise alignment of the electron gun is fundamental for XPS analysis because misalignment can lead to electron beam position shift and reduce signal intensity when the objective lens current (OLC) changes slightly. This work proposes a new electron beam gun alignment method utilizing a Faraday cup fitted with two sharp tungsten edges. Following mechanical alignment, the electrical alignment parameters are optimized incrementally, while the corresponding positions and shapes of beam spots at different OLCs are measured concurrently. The electron beam alignment is considered completed when all the measured beam spots maintain a consistent center position and exhibit regular circular shapes. Employing this method, precise alignment of the electron gun can be accomplished in two types of scenarios: when the beam spot is about 52 mu m or 8 mu m. The alignment is also verified by a series of images captured by a camera when the electron beam bombards tungsten. This is a promising alignment method for other electron or ion guns with a similar beam size.

High-transmission-efficiency, high-beam-current-density electron guns are pivotal components for breakthroughs in electron beam processing and characterization technologies. This work presents an electron-optics design method addressing two critical working modes: achieving a beam density > 1200 A/cm(2) with a spot size <= 10 mu m, and maintaining a transmission efficiency > 85% for spot sizes of 50-65 mu m. Guided by fundamental electron optics theory, a calculation framework for electron focusing and efficient transmission is established, enabling the optimization design of a high-brightness electron source and an electromagnetic focusing lens. The experimental results demonstrate that the discrepancy between simulation and measurement results is within 5% under the condition with an acceleration voltage of 20 kV and a working distance of 20 mm. This study lays a technical foundation for the development of electron guns featuring high transmission efficiency and high beam current density.

Electron beam fluorescence technology is an advanced non-contact measurement in rarefied flow fields,and the fluorescence signal intensity is positively correlated with the electron beam current.The ion bombardment secondary emission electron gun is suitable for the technology.To enhance the beam current,COMSOL simulations and analyses were conducted to examine plasma density distribution in the discharge chamber under the effects of various conditions and the electric field distribution between the cathode and the spacer gap.The anode shape and discharge pressure conditions were optimized to increase plasma density.Additionally,an improved spacer structure was designed with the dual purpose of enhancing the electric field distribution between the cathode-spacer gaps and improving vacuum differential effects.This design modification aims to increase the pass rate of secondary electrons.Both simulation and experimental results demonstrated that the performance of the optimized electron gun was effectively enhanced.When the electrode voltage remains constant and the discharge gas pressure is adjusted to around 8 Pa,the maximum beam current was increased from 0.9 mA to 1.6 mA.

To enhance the throughput of single-beam devices,such as scanning electron microscopes,a multi-beam electron source system utilizing a Schottky gun was developed.This study encompasses the design methodologies and fabrication processes for the collimator lens,aperture array,and micro-arrayed electrostatic lenses.The electrostatic collimator lens was designed based on the emission characteristics of the Schottky cathode,and the performance of the collimated beam was subsequently calculated.Aperture arrays,including configurations of 3×3 and 10×10 for beam splitting,were fabricated utilizing MEMS technology,and a high-precision assembly system was established to enable the assembly of micro-arrayed electrostatic lenses.Experiments concerning beam collimation,splitting,and focusing were conducted on a dedicated multi-beam electron source experimental platform,validating the performance of the 3×3 mul-tibeam electron source.Experimental results indicate that the collimated spot size was measured to be 600 μm with a beam current density of 4.11 A/m² and a uniformity of 6.06%.The average diameter of the fo-cused beamlet is recorded at 5.32 μm,accompanied by size uniformity of 5.91%,intensity uniformity of 4.36%,and pitch uniformity of 3.06%,all of which meet the design criteria of the multi-beam setup.

This study investigates the fabrication of directly heated LaB6 cathodes, with a focus on their applicability in high-power electron-beam welding guns. Experimental results reveal that the LaB6 cathode achieves a current density of 30 A/cm2 at 1627 °C – a temperature 1000 °C lower than that required by W cathodes for comparable performance. Quantitative measurements show the LaB6 cathode produces welds with a depth-to-width ratio of 20:1, doubling the 10:1 ratio achieved with the W cathode.

The micro-arrayed beam blanker is essential for the multi-beam electron beam lithography sys-tem,enabling the rapid exposure of complex graphics by controlling the electron beam's opening and clos-ing. In this study,a 3×3 micro-arrayed beam blanker was designed and fabricated,followed by an experi-ment on multi-beam electron beam deflection. Based on prior optimization,the structural design and MEMS-based processing technology were developed,resulting in successful fabrication of the beam blank-er. A controller capable of independently managing the multi-beam was then created and connected to the beam blanker to validate its deflection speed and functionality. The deflection experiment conducted on a multi-beam test platform examined crosstalk effects. Results indicate that the controller's deflection speed reaches 43.5 MHz,exceeding the design target of 10 MHz. The beam blanker independently opens and closes the electron beam,with a deflection range of 25-30 μm,which is below the predicted 43.29 μm. Crosstalk levels were all under 3％. While the designed micro-arrayed beam blanker effectively controls the multi-beam electron beam,further optimization is needed for deflection accuracy and processing tech-nology.

The incident beam quality at the target determines the resolution and intensity of micro-focus X-ray sources, which depends greatly on the focusing system and the target. To meet different spatial layouts of the focusing system with transmission and reflection targets, three-dimension (3-D) modelling of the focusing system was built with Monte Carlo simulation and coordinate transforming method in this paper. In the proposed approach, the focusing system was first optimized by a 2-D model to achieve a fine beam spot with high effective current at the optimum working distance for the transmission and reflection targets. Then, 3-D practical model of the focusing system was achieved by tracing N electrons from the electron gun in three directions using the 5-order Runge-Kutta method. Finally, examples of the focusing system for 90 key and 30 key X-ray sources were given to get the energy distributions at transmission and reflection targets. Results show that resolutions of 4 mu m and 500 nm have been achieved for 90 key X-ray source with the transmission target and 30 key X-ray source with the reflection target respectively. Compared with the experimental results, 2-D modelling of the focusing system is also applicable for X-ray source with the transmission target while 3-D modelling of the focusing system is essential for X-ray source with the reflection target. In addition, the 3-D electron beam model will simplify the design of the real apertures, liner tubes, beam blankers etc.

A variable axis lens (VAL) concept has been demonstrated an effective method to reduce aberrations of electron beam machines and has been explored to several configurations. To implement the advantages of VAL fully, it is desirable to make the axial potential distribution of the objective lens match the deflection functions of deflectors well. To our knowledge, the electrostatic deflectors applied in electron-optical systems based on VAL concept are all constructed with a “cylindrical” shape. However, when a magnetic objective lens in the VAL configurations is constructed with different radii of upper and lower pole pieces, there is a mismatch between the asymmetric lens and cylindrical deflectors, which would lead to a significant increase in aberrations. With this in mind, we have developed tapered deflectors to address the foregoing problem. A comparative study on variable axis lens systems based on conventional cylindrical deflectors and the proposed tapered ones is undertaken. Simulation results demonstrate the validity and effectiveness of the proposed VALs to reduce aberrations and an electron beam landing angle.

Electron beam (e-beam) with a small spot size is the key to produce microfocus x-ray source. The spot size of the e-beam can be controlled by changing the aperture angle at the target, and the focus size of the microfocus x-ray source is changed accordingly. At the same time, the SNR (Signal-to-Noise Ratio) of the image is reduced because the aperture produces secondary x-ray, which interferes with the x-ray imaging. In this paper, the aperture size and its position are optimized for getting the smallest spot size of the e-beam, and the experimental results show that the resolution is 0.8 mu m with the aperture size of 0.5 mm. In addition, this paper also presents that the image's SNR can be improved by coating carbon film on the back surface of the aperture.

Objective Environmental scanning electron microscopes (ESEMs) are widely employed for high-resolution observation of water containing, oil containing, and biological samples in low vacuum environments. However, at present, the development of ESEMs in China is almost blank, and most of them need to rely on imports. Therefore, the research on ESEMs can help improve China's independent development capability in this field, and provide a theoretical and experimental basis for the development of ESEMs in the future. Compared with conventional electron microscopy, the sample chamber of ESEMs should be in a low vacuum or ambient state. The vacuum value is generally on the order of 100 Pa, while that of the electron beam channel and the electron gun needs to be less than 1x10(-3) Pa and 1x10(-7) Pa respectively. The pressure difference between the electron beam channel and the sample chamber is much larger than that between the electron gun and the electron beam channel. The conventional method is to add a throttle tube between the electron beam channel and the sample chamber. Meanwhile, since the large pressure difference remains much greater than that between the electron gun and the electron beam channel, the conventional method is to add a throttle tube between the electron beam channel and the sample chamber, but the large pressure difference will result in a long throttle tube with a small aperture. This will bring practical problems in imaging, such as the longer throttle tube leading to an increase in the working distance of the objective lens. As a result, it increases the spherical aberration, reduces the imaging resolution, and causes a smaller deflection range to a certain extent. Additionally, the long throttle tube will lead to the presence of residual gas inside the tube, the electron beam will drift in a section of the gas space where there is low gas pressure, and the probability of collision between the electron beam and the gas is high, which will have a greater effect on the resolution at low accelerating voltages. Therefore, the comprehensive design of ESEMs, which plays a key role in the system resolution of the objective lens and vacuum differential structure, is the study focus and difficulty. Methods Starting from the theory of electron optics, we consider the structure of the objective lens and the vacuum differential structure in the ESEM comprehensively. Firstly, two throttle tubes are designed between the sample chamber and the electron beam channel (near the lower pole shoe of the objective lens), and a transition zone is added inside the objective lens to form a three-level vacuum differential structure of the sample chamber, the transition zone and the electron beam channel. The vacuum in the transition zone should be two orders of magnitude higher than that in the sample chamber, and that in the electron beam channel should be two to three orders of magnitude higher than that in the transition zone. Considering the processing cost and difficulty of the elongated throttle tube, we adopt the combination of multiple diaphragms, which can more conveniently change the vacuum level by adjusting the aperture and number of diaphragm sheets in the diaphragm groove to achieve the required differential pressure difference. Then, the optimized design of a high-resolution ESEM objective lens and deflector is carried out based on a double-throttle vacuum resistance structure. Finally, an experimental platform is set up, and the objective magnetic field test, vacuum differential pressure test, and resolution test are carried out for validation. Results and Discussions Considering the objective structure and vacuum differential structure in the ESEM, a double throttle tube vacuum resistance structure as shown in Fig. 2 is designed to form a three-stage differential test structure (Fig. 10). This design can reduce the length of the throttle tube as a whole, which lowers the requirements for the aperture and length of the throttle tube to a certain extent, and thus reduces the influence on the working distance and the deflection field. Meanwhile, it can also reduce the gas residual situation in the narrow throttle tube, and reduce the influence of the electron beam drift in the narrow gas space in the throttle tube. The results of the vacuum differential pressure test show that the vacuum in the transition vacuum zone is two orders of magnitude higher than that in the sample chamber, and the vacuum in the electron beam channel is two to three orders of magnitude higher than that in the transition vacuum zone, which can meet the design requirements. The resolution test results show that in the current experimental conditions and the low vacuum environment mode of 133 Pa, the imaging resolution corresponding to the 20 mu mx20 mu m scanning field is better than 50 nm, and that corresponding to the 80 mu mx80 mu m scanning field is better than 100 nm when the working distance is 15 mm (Fig. 13). Conclusions Starting from the electron optics theory, we consider the objective lens structure and vacuum differential structure in the ESEM comprehensively, and the two are combined for the optimal design to provide a design method for the objective lens with variable vacuum structures. Systematic analyses, calculations, and simulations are carried out. Based on the theoretical analysis and simulation results, a magnetic field test platform and an ESEM experimental test platform are built for experiments, and the results show that in the current experimental conditions and low vacuum environment mode, the imaging resolution of 20 mu mx20 mu m scanning field corresponds to a resolution of better than 50 nm when the working distance is 15 mm. The overall closed-loop design and test of the objective lens with variable vacuum structures provide a theoretical and experimental basis for the development of ESEM.

为了降低微型阵列式束闸边缘场和邻近电场对多束电子束的偏转影响和串扰,本文以3×3阵列束闸为研究对象,利用COMSOL Multiphysics中的静电和带电粒子追踪模块,研究束闸长宽比、隔离接地极和束闸上方增加接地层对电子束偏转的影响.研究表明,在长宽比不变的情况下,边缘场对电子束偏转的影响在总偏转量中的占比与偏转电压无关;而偏转极板的长宽比越大越有利于精确控制电子束的偏转;通过优化隔离接地电极结构与参数,可减小束闸之间的串扰引起的束斑模糊问题.为了减小边缘场和邻近电场对电子束偏转的影响,本研究分析得出,如果束闸上方接地层的作用范围小于100 μm,可在一定程度上抑制串扰的影响.同时,分析表明将接地层上圆孔改为方孔后,也在一定程度上减小了不平衡电场带来的影响.

AbstractPolymer dielectrics with excellent thermal resistance and superior energy storage behaviour are extensively demanded with the increasing development of film capacitors applied in hostile environments. In this study, novel diamine with sulfonyl‐containing side chain was designed and synthesised. The corresponding polyimide (PI) dielectrics derived from the sulfonyl‐containing diamine were prepared, so were the polyimides possessing the same backbone but without side chains. Consequently, superior thermal resistance of glass transition temperature ranged from 162–208°C was obtained. Moreover, the polyimides presented permittivity of 3.34–5.89 at 1 kHz, Weibull breakdown strength of 377–538 MV/m and discharged energy density of 3.82–5.85 J/cm3. In particular, sulfonyl‐containing polyimide of SPI‐2 with flexible backbone and sulfonyl side chain indicates the highest discharged energy density and charge‐discharge efficiency simultaneously. The introduction of the strong polar sulfonyl group in the side chain enhances dielectric and energy storage properties effectively. In addition, it is found that the dipolar moment density (μ/Vvdw) calculated from molecular simulation is closely correlated to permittivity measured from experiments. The combined method of molecular simulation and experiments would offer an effective approach to assist in molecular design of high‐performance polymer dielectrics.

In this paper, the electrical performance of 225 kV electron gun is optimized based on the avalanche theory of secondary electron emission. Due to the electron gun shield, the Angle between the electric field direction of the electron gun insulator and the insulator surface changes in positive and negative directions. Different discussions should be made on the insulators in the acting area of the shield and other areas. Bessel curve and spline curve were selected to parameterize the model of insulator and shield. The ratio of normal electric field and tangential electric field of insulator outer contour, integral value of tangential electric field of insulator outer contour along the outer contour and maximum field intensity of shield surface were taken as the optimization objective function, and the Nelder-Mead approximate gradient algorithm method was used to solve the problem. After optimization, the maximum electric field strength on the shield surface is reduced by 37.3%, the field strength at the cathode triple junction (CTJ) is reduced by 76.7%, and the maximum electric field strength on the insulator surface is reduced by 25.5%. The tangential electric field distribution on the insulator surface is also optimized.

本文对多束电子光学系统的国内外研究现状进行了详细调研,总结了各个系统的特点以及应用领域.多束电子光学系统在生命科学领域、材料领域以及半导体领域具有广泛的应用价值,本文指出了我国需要开展这方面研究的必要性.同时,本文介绍了国内在多束电子光学领域的研究进展.

Objective Wavelength dispersive X-ray fluorescence spectrometer (WDXRF) is widely applied in disparate fields such as metallurgy, building materials, and geological surveys. Its detection principle involves employing a primary X-ray beam to excite a fluorescent beam on the sample, which is then dispersed by a dispersive crystal based on wavelength. The intensities at different wavelengths are measured and a spectrum is generated to qualitatively and quantitatively analyze the elemental composition of the sample. During the test, certain degree of intensity is lost due to the dispersion of X-ray fluorescence by the dispersive crystal. Thus, a higher intensity of the primary X-ray beam is required, which is typically achieved by an X-ray tube with high-power as the excitation source. X-ray tubes with high power can be categorized into two types of side-window and end-window X-ray tubes based on their structural forms. For end-window X-ray tubes, since the window does not absorb backscattered electrons, the beryllium window is relatively thinner, which increases the transmissivity of longer wavelength radiation and facilitates the excitation of light elements. The power of an X-ray tube is determined by the tube voltage and current. Higher tube voltage produces X-rays with higher energy, while larger tube current increases the X-ray brightness. The power of an X-ray tube is influenced by factors such as the distribution of the electric field between the two electrodes inside the tube, cathode material, temperature, surface area, and shape. Currently, Malvern Panalytical is a representative company overseas that produces end-window X-ray tubes with high power, with 75 kV/4 kW being the main specification. In China, end-window X-ray tubes are mainly focused on low-power applications, and no products are available on the market for end-window X-ray tubes with high power. They are still in the design and testing phase, and there is still a gap in power control and target focal spot control compared with the advanced international level. Therefore, further simulation studies are needed for the relevant structures of end-window X-ray tubes with high power. Methods We develop methods to address the problem that the beam current and power of domestically produced end-window X-ray tubes with high power are below the design values. First, the structure of the end-window X-ray tube with high power is analyzed, and the structure is simplified based on the requirements of finite element calculations. The simplification method of the end-window X-ray tube with high power is as follows. 1) The unclosed filament is simplified into a closed ring structure. 2) The influence of the water-cooled structure inside the anode on the simulation results is not considered. 3) As the target and anode are at the same potential, both of them are modeled as a whole. 4) The ceramic column, the support structure of the filament, and the end-window structure of the X-ray tube are ignored. Then, the limiting factors for beam current emission in the end-window X-ray tube with high power are determined based on the thermionic emission theory and the theory of space charge limited emission. Two optimization schemes are proposed based on the analysis of simulation results. Finally, the feasibility of the optimization schemes is verified through simulation analysis and experiments. Results and Discussions In the theoretical simulation calculations, the electron beam trajectory, beam current, and target focal spot are computed for the two theoretical models (Tables 2 and 3). The results based on the thermionic emission theory show that a large number of electrons return to the filament surface due to insufficient initial energy to overcome the potential near the cathode, resulting in a beam current reaching the target material of only 32. 65 mA. Considering the space charge effect, the beam current value obtained from the theory of space charge limited emission is 18. 01 mA. The analysis of simulation results indicates that the potential distribution near the cathode has a significant influence on the beam current reaching the target material. Based on this analysis, we propose two optimization schemes. One scheme is changing the filament potential and increasing the potential gradient near the filament to improve the influence of space charge effects. The other is changing the filament position to increase the accelerating voltage near the filament, thereby better extracting the beam current (Figs. 4 and 5). Conclusions According to the simulation results, both schemes can improve the beam current of existing X-ray tubes with high power. An experimental platform is set up to validate the simulation results. The experimental setup consists of a vacuum pump unit, voltage source, current source, variable resistor, vacuum chamber, X-ray tube filament, and copper electrodes. The experiments confirm the applicability of the emission models adopted in our study to end-window X-ray tubes with high power, and the maximum beam current limited by temperature is obtained when the filament current is 12 A, with a value of 63. 4 mA. The feasibility of the two optimization schemes is also verified.

The development of high temperature resistant dielectrics with excellent dielectric properties and self-healing behavior is crucial for the application of metallized film capacitors. In this work, a series of polyetherimide (PEI) dielectric films are designed and fabricated. The introduction of polar groups is in favor to the increase of permittivity, and the flexible connection such as ether group would facilitate the reduction of dielectric loss. Moreover, the oxygen elements is beneficial to the "self-healing" of metallized film capacitors. Consequently, permittivity of 3.53 ∼ 4.00, dissipation factor of 0.281% ∼ 0.517%, and Weibull breakdown strength of 347 ∼ 674 MV/m are obtained for the polyetherimide dielectrics. In addition, PEI-4 (BPADA-BAPP) and PEI-8 (BPADA-MDA) are selected to further investigate dielectric breakdown (150°C), electrical displacement-electric filed (D-E) loop (at room temperature and 150°C) as well as self-healing performance, which would evaluate their potential in practical applications. The results show that PEI-8 has stable breakdown field strength and high charge-discharge efficiency at elevated temperature. Metallized film capacitor based on PEI-8 exhibited excellent self-healing performance, with pleasing self-clear morphology, high breakdown voltage and reduced self-healing energy. Therefore, PEI-8 is considered as a potential candidate for metallized film capacitors applied under harsh conditions. This article is protected by copyright. All rights reserved.