The novel coronavirus pneumonia triggered by COVID-19 is now raging the whole world.As a rapid and reliable killing COVID-19 method in industry,electron beam irradiation can interact with virus molecules and destroy t...The novel coronavirus pneumonia triggered by COVID-19 is now raging the whole world.As a rapid and reliable killing COVID-19 method in industry,electron beam irradiation can interact with virus molecules and destroy their activity.With the unexpected appearance and quickly spreading of the virus,it is urgently necessary to figure out the mechanism of electron beam irradiation on COVID-19.In this study,we establish a virus structure and molecule model based on the detected gene sequence of Wuhan patient,and calculate irradiated electron interaction with virus atoms via a Monte Carlo simulation that track each elastic and inelastic collision of all electrons.The characteristics of irradiation damage on COVID-19,atoms’ionizations and electron energy losses are calculated and analyzed with regions.We simulate the different situations of incident electron energy for evaluating the influence of incident energy on virus damage.It is found that under the major protecting of an envelope protein layer,the inner RNA suffers the minimal damage.The damage for a^100-nm-diameter virus molecule is not always enhanced by irradiation energy monotonicity,for COVID-19,the irradiation electron energy of the strongest energy loss damage is 2 keV.展开更多
In this study, using a comprehensive numerical simulation of charge and discharge processes, we investigate the formation and evolution of negative charge and discharge characteristics of a grounded PMMA film irradiat...In this study, using a comprehensive numerical simulation of charge and discharge processes, we investigate the formation and evolution of negative charge and discharge characteristics of a grounded PMMA film irradiated by a non- focused electron beam. Electron scattering and transport processes in the sample are simulated with the Monte Carlo and the finite-different time-domain (FDTD) methods, respectively. The properties of charge and discharge processes are presented by the evolution of internal currents, charge quantity, surface potential, and discharge time. Internal charge accumulation in the sample may reach saturation by primary electron (PE) irradiation providing the charge duration is enough. Internal free electrons will run off to the ground in the form of leakage current due to charge diffusion and drift during the discharge process after irradiation, while trapped electrons remain. The negative surface potential determined by the charging quantity decreases to its saturation in the charge process, and then increases in the discharge process. A larger thickness of the PMMA film will result in greater charge amount and surface potential in charge saturation and in final discharge state, while the electron mobility of the material has little effects on the final discharge state. Moreover, discharge time is less for smaller thickness or larger electron mobility. The presented results can be helpful for estimating and weakening the charging of insulating samples especially under the intermittent electron beam irradiation in related surface analysis or measurement.展开更多
A series of synthetic variations of material intrinsic properties always come with charging phenomena due to electron beam irradiation. The effects of charging on the dielectric constant will influence the charging dy...A series of synthetic variations of material intrinsic properties always come with charging phenomena due to electron beam irradiation. The effects of charging on the dielectric constant will influence the charging dynamic in return. In this paper, we propose a numerical simulation for investigating the dynamic characteristics of charging effects on the dielectric constant due to electron beam irradiation. The scattering process between electrons and atoms is calculated considering elastic and inelastic collisions via the Rutherford model and the fast secondary electron model, respectively. Internal charge drift due to E-field, density gradient caused diffusion, charges trap by material defect, free electron and hole neutralization, and variation in the internal dielectric constant are considered when simulating the transport process. The dynamics of electron and hole distributions and charging states are demonstrated during E-beam irradiation. As a function of material nonlinear susceptibility and primary energy, the dynamics of charging states and dielectric constants are then presented in the charging process. It is found that the variation in the internal dielectric constant is more with respect to the depth and irradiation time. Material with a larger nonlinear susceptibility corresponds a faster charging enhancement. In addition, the effective dielectric constant and the surface potential have a linear relationship in the charging balance. Nevertheless, with shrinking charging affect range, the situation with a higher energy primary electron comes with less dielectric constant variation. The proposed numerical simulation mode of the charging process and the results presented in this study offer a comprehensive insight into the complicated charging phenomena in electron irradiation related fields.展开更多
As a typical two-dimensional(2D) coating material, graphene has been utilized to effectively reduce secondary electron emission from the surface. Nevertheless, the microscopic mechanism and the dominant factor of seco...As a typical two-dimensional(2D) coating material, graphene has been utilized to effectively reduce secondary electron emission from the surface. Nevertheless, the microscopic mechanism and the dominant factor of secondary electron emission suppression remain controversial. Since traditional models rely on the data of experimental bulk properties which are scarcely appropriate to the 2D coating situation, this paper presents the first-principles-based numerical calculations of the electron interaction and emission process for monolayer and multilayer graphene on silicon(111) substrate. By using the anisotropic energy loss for the coating graphene, the electron transport process can be described more realistically. The real physical electron interactions, including the elastic scattering of electron-nucleus, inelastic scattering of the electron-extranuclear electron, and electron-phonon effect, are considered and calculated by using the Monte Carlo method. The energy level transition theory-based first-principles method and the full Penn algorithm are used to calculate the energy loss function during the inelastic scattering. Variations of the energy loss function and interface electron density differences for 1 to 4 layer graphene coating Go Si are calculated, and their inner electron distributions and secondary electron emissions are analyzed. Simulation results demonstrate that the dominant factor of the inhibiting of secondary electron yield(SEY) of Go Si is to induce the deeper electrons in the internal scattering process. In contrast, a low surface potential barrier due to the positive deviation of electron density difference at monolayer Go Si interface in turn weakens the suppression of secondary electron emission of the graphene layer. Only when the graphene layer number is 3, does the contribution of surface work function to the secondary electron emission suppression appear to be slightly positive.展开更多
Calculations of secondary electron yield(SEY) by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface ...Calculations of secondary electron yield(SEY) by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface contamination states of real sample result in notable difference between simulations and experiments. In this paper, in order to calculate SEY of metal under complicated surface state accurately, we propose a synthetic semi-empirical physical model. The processes of excitation of internal secondary electron(SE) and movement toward surface can be simulated using this model.This model also takes into account the influences of incident angle and backscattering electrons as well as the surface gas contamination. In order to describe internal electronic states accurately, the penetration coefficient of incident electron is described as a function of material atom number. Directions of internal electrons are set to be uniform in each angle. The distribution of internal SEs is proposed by considering both the integration convergence and the cascade scattering process.In addition, according to the experiment data, relationship among desorption gas quantities, sample ultimate temperature and SEY is established. Comparing with experiment results, this synthetic semi-empirical physical model can describe the SEY of metal better than former formulas, especially in the aspect of surface contaminated states. The proposed synthetic semi-empirical physical model and presented results in this paper can be helpful for further studying SE emission, and offer an available method for estimating and taking advantage of SE emission accurately.展开更多
针对航天有效载荷微波部件频发的微放电现象,采用微陷阱表面构型来抑制微波材料表面的二次电子发射,从而达到微放电抑制效果。通过硅基材料的表面刻蚀和金属Ag的表面溅射获得规整的金属表面微陷阱结构,将表面处理过的金属样品在二次电...针对航天有效载荷微波部件频发的微放电现象,采用微陷阱表面构型来抑制微波材料表面的二次电子发射,从而达到微放电抑制效果。通过硅基材料的表面刻蚀和金属Ag的表面溅射获得规整的金属表面微陷阱结构,将表面处理过的金属样品在二次电子发射平台的电子枪20~4 000 e V照射下,采用电流法获得金属微陷阱表面的二次电子产额曲线及抑制特性。此外,通过将表面出射的二次电子分为弹性背散射电子、非弹性背散射电子和本征二次电子,并跟踪电子在陷阱结构内的级联再入射过程,建立表面圆柱孔和矩形槽微陷阱表面的二次电子发射数值模型,模拟结果与测试结果能很好吻合。采用数值模拟的方法构造不同深宽比的微陷阱结构表面,最大二次电子产额、第一交叉能量以及微放电品质因子的变化规律。研究结果表明:陷阱结构的侧壁遮挡效果能有效抑制二次电子从表面发射,并且深宽比越大的表面陷阱结构抑制效果更强,而在相同深宽比情况下,圆柱孔陷阱结构比矩形槽陷阱结构对二次电子的抑制效果更好,此外,陷阱结构的深宽比不仅能使得最大二次电子产额减小、第一交叉能量增大,还会近线性地增大材料的微放电品质因子F。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61901360)。
文摘The novel coronavirus pneumonia triggered by COVID-19 is now raging the whole world.As a rapid and reliable killing COVID-19 method in industry,electron beam irradiation can interact with virus molecules and destroy their activity.With the unexpected appearance and quickly spreading of the virus,it is urgently necessary to figure out the mechanism of electron beam irradiation on COVID-19.In this study,we establish a virus structure and molecule model based on the detected gene sequence of Wuhan patient,and calculate irradiated electron interaction with virus atoms via a Monte Carlo simulation that track each elastic and inelastic collision of all electrons.The characteristics of irradiation damage on COVID-19,atoms’ionizations and electron energy losses are calculated and analyzed with regions.We simulate the different situations of incident electron energy for evaluating the influence of incident energy on virus damage.It is found that under the major protecting of an envelope protein layer,the inner RNA suffers the minimal damage.The damage for a^100-nm-diameter virus molecule is not always enhanced by irradiation energy monotonicity,for COVID-19,the irradiation electron energy of the strongest energy loss damage is 2 keV.
基金supported by the National Natural Science Foundation of China(Grant Nos.11175140 and 11004157)the Foundation of National Key Laboratory of Space Microwave Technology of China(Grant No.9140C530101130C53013)
文摘In this study, using a comprehensive numerical simulation of charge and discharge processes, we investigate the formation and evolution of negative charge and discharge characteristics of a grounded PMMA film irradiated by a non- focused electron beam. Electron scattering and transport processes in the sample are simulated with the Monte Carlo and the finite-different time-domain (FDTD) methods, respectively. The properties of charge and discharge processes are presented by the evolution of internal currents, charge quantity, surface potential, and discharge time. Internal charge accumulation in the sample may reach saturation by primary electron (PE) irradiation providing the charge duration is enough. Internal free electrons will run off to the ground in the form of leakage current due to charge diffusion and drift during the discharge process after irradiation, while trapped electrons remain. The negative surface potential determined by the charging quantity decreases to its saturation in the charge process, and then increases in the discharge process. A larger thickness of the PMMA film will result in greater charge amount and surface potential in charge saturation and in final discharge state, while the electron mobility of the material has little effects on the final discharge state. Moreover, discharge time is less for smaller thickness or larger electron mobility. The presented results can be helpful for estimating and weakening the charging of insulating samples especially under the intermittent electron beam irradiation in related surface analysis or measurement.
基金supported by National Natural Science Foundation of China(Grant Nos.U1537211 and 11675278)the China Postdoctoral Science Foundation(Grant No.2016M602944XB)
文摘A series of synthetic variations of material intrinsic properties always come with charging phenomena due to electron beam irradiation. The effects of charging on the dielectric constant will influence the charging dynamic in return. In this paper, we propose a numerical simulation for investigating the dynamic characteristics of charging effects on the dielectric constant due to electron beam irradiation. The scattering process between electrons and atoms is calculated considering elastic and inelastic collisions via the Rutherford model and the fast secondary electron model, respectively. Internal charge drift due to E-field, density gradient caused diffusion, charges trap by material defect, free electron and hole neutralization, and variation in the internal dielectric constant are considered when simulating the transport process. The dynamics of electron and hole distributions and charging states are demonstrated during E-beam irradiation. As a function of material nonlinear susceptibility and primary energy, the dynamics of charging states and dielectric constants are then presented in the charging process. It is found that the variation in the internal dielectric constant is more with respect to the depth and irradiation time. Material with a larger nonlinear susceptibility corresponds a faster charging enhancement. In addition, the effective dielectric constant and the surface potential have a linear relationship in the charging balance. Nevertheless, with shrinking charging affect range, the situation with a higher energy primary electron comes with less dielectric constant variation. The proposed numerical simulation mode of the charging process and the results presented in this study offer a comprehensive insight into the complicated charging phenomena in electron irradiation related fields.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61901360 and 12175176)the Natural Science Foundation of Shaanxi Province, China (Grant No. 2020JQ-644)the Scientific Research Projects of the Shaanxi Education Department, China (Grant No. 20JK0808)。
文摘As a typical two-dimensional(2D) coating material, graphene has been utilized to effectively reduce secondary electron emission from the surface. Nevertheless, the microscopic mechanism and the dominant factor of secondary electron emission suppression remain controversial. Since traditional models rely on the data of experimental bulk properties which are scarcely appropriate to the 2D coating situation, this paper presents the first-principles-based numerical calculations of the electron interaction and emission process for monolayer and multilayer graphene on silicon(111) substrate. By using the anisotropic energy loss for the coating graphene, the electron transport process can be described more realistically. The real physical electron interactions, including the elastic scattering of electron-nucleus, inelastic scattering of the electron-extranuclear electron, and electron-phonon effect, are considered and calculated by using the Monte Carlo method. The energy level transition theory-based first-principles method and the full Penn algorithm are used to calculate the energy loss function during the inelastic scattering. Variations of the energy loss function and interface electron density differences for 1 to 4 layer graphene coating Go Si are calculated, and their inner electron distributions and secondary electron emissions are analyzed. Simulation results demonstrate that the dominant factor of the inhibiting of secondary electron yield(SEY) of Go Si is to induce the deeper electrons in the internal scattering process. In contrast, a low surface potential barrier due to the positive deviation of electron density difference at monolayer Go Si interface in turn weakens the suppression of secondary electron emission of the graphene layer. Only when the graphene layer number is 3, does the contribution of surface work function to the secondary electron emission suppression appear to be slightly positive.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1537211 and 11675278)the China Postdoctoral Science Foundation(Grant No.2016M602944XB)
文摘Calculations of secondary electron yield(SEY) by physical formula can hardly accord with experimental results precisely. Simplified descriptions of internal electron movements in the calculation and complex surface contamination states of real sample result in notable difference between simulations and experiments. In this paper, in order to calculate SEY of metal under complicated surface state accurately, we propose a synthetic semi-empirical physical model. The processes of excitation of internal secondary electron(SE) and movement toward surface can be simulated using this model.This model also takes into account the influences of incident angle and backscattering electrons as well as the surface gas contamination. In order to describe internal electronic states accurately, the penetration coefficient of incident electron is described as a function of material atom number. Directions of internal electrons are set to be uniform in each angle. The distribution of internal SEs is proposed by considering both the integration convergence and the cascade scattering process.In addition, according to the experiment data, relationship among desorption gas quantities, sample ultimate temperature and SEY is established. Comparing with experiment results, this synthetic semi-empirical physical model can describe the SEY of metal better than former formulas, especially in the aspect of surface contaminated states. The proposed synthetic semi-empirical physical model and presented results in this paper can be helpful for further studying SE emission, and offer an available method for estimating and taking advantage of SE emission accurately.
文摘针对航天有效载荷微波部件频发的微放电现象,采用微陷阱表面构型来抑制微波材料表面的二次电子发射,从而达到微放电抑制效果。通过硅基材料的表面刻蚀和金属Ag的表面溅射获得规整的金属表面微陷阱结构,将表面处理过的金属样品在二次电子发射平台的电子枪20~4 000 e V照射下,采用电流法获得金属微陷阱表面的二次电子产额曲线及抑制特性。此外,通过将表面出射的二次电子分为弹性背散射电子、非弹性背散射电子和本征二次电子,并跟踪电子在陷阱结构内的级联再入射过程,建立表面圆柱孔和矩形槽微陷阱表面的二次电子发射数值模型,模拟结果与测试结果能很好吻合。采用数值模拟的方法构造不同深宽比的微陷阱结构表面,最大二次电子产额、第一交叉能量以及微放电品质因子的变化规律。研究结果表明:陷阱结构的侧壁遮挡效果能有效抑制二次电子从表面发射,并且深宽比越大的表面陷阱结构抑制效果更强,而在相同深宽比情况下,圆柱孔陷阱结构比矩形槽陷阱结构对二次电子的抑制效果更好,此外,陷阱结构的深宽比不仅能使得最大二次电子产额减小、第一交叉能量增大,还会近线性地增大材料的微放电品质因子F。