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随着科学技术的发展,出现了多种测定电子比荷的方法,其中在近代物理实验中常用的方法是磁聚焦法.本文在此实验设备和实验方法的基础上,研究了实验测量过程中荧光屏上显示扫描的线段随所加励磁电流的变化关系,并进一步对实验提出了改进意见. 相似文献
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用金属电子逸出功测定仪做设计性扩展实验的实践 总被引:3,自引:1,他引:2
介绍利用金属电子逸出功测定仪研究轴向磁场对自由电子的磁控条件及测定电子比荷,研究真空二极管的伏安特性,研究金属中自由电子的费米-狄拉克能量分布状况等设计性扩展实验的内容和方法。 相似文献
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《中国物理 B》2015,(11)
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 nonfocused 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. 相似文献
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The image theory of wave electron optics is used to study the current density distribution of electron beam spots for high-resolution electron optical systems. Using the wave aberration concept and paraxial expansion of charge density, the space charge effect is taken into consideration by modification of paraxial rays and spherical aberration coefficient of the lens. The point spreading function is obtained by Fourier-Bessel transform of the optical transfer function considering the space charge and partial coherence of the electron source. 相似文献
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采用扩展的SSH模型,加上电子相互作用和长程电子关联,用自洽迭代的方法研究了聚噻吩链中的极化子问题,计算了电子相互作用和长程电子关联对极化子位形和电荷密度的影响,获得了长程电子关联使极化子位形变小,极化子区域变窄,电荷密度震荡减弱,对聚合物中电子的输运的影响不能忽略的有益结果. 相似文献
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The charge composition of an ion beam from an E-Mevva source is calculated within a model of sequential electron ionization of ions in a vacuum arc plasma. The effect of the plasma initial parameters on the charge composition of the ion beam is studied. Possible charge compositions for more than 30 elements omitted from this article are estimated. Also, the charge composition of the ions is calculated for the ultimate current density of the electron beam. 相似文献
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In this second paper, the effect of secondary electrons on the charge and potential of a dust particle immersed in plasma has been studied. The processes of electron‐induced ionization and those of photo‐electron and secondary electron emission from the particle surface as a function of primary electron temperature have been taken into account. Starting from temperatures as low as 6 eV in an Ar plasma, ionization produces an extra ion flux to the dust surface comparable to that of the ion charge exchange effect. For what concerns the surface emission, results show that a transition from negative to positive dust charge/potential takes place, and that the transition regime is characterized by a non‐monotonic behavior of the electric potential around the particle. In the case of photoelectric emission, the dust charge and potential are monotonic decreasing functions of the electron temperature, while in the case of emission induced by primary electrons a minimum charge/potential is reached before they grow towards positive values. In no case multiple dust charge states have been observed due to the presence of the potential well attached to the particle surface. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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V. V. Kashkovskii 《Russian Physics Journal》2006,49(12):1301-1313
The mechanism of electron capture into acceleration that takes into account the electret properties of the accelerating chamber
shell is described. The electron capture into acceleration is a self-consistent problem. It is demonstrated that the electron
capture into acceleration is caused by the interaction of the injected electrons with the electric field of the charge created
on the side interior wall of the chamber by electrons dropped out of the acceleration. The spectrum of the captured electrons
is not normal. A large number of low-energy electrons are presented in the spectrum. Two and more peaks previously unknown
are revealed in the dependence of the captured charge on the injected charge for large values of the injected charge. The
results obtained are in agreement with the data of previous experimental studies. The captured charge and the dose rate of
bremsstrahlung from a target correspond to their actual values for betatrons with accelerated electron energies of 6 and 10
MeV. Results of simulation can be used to design accelerating chambers and electron injection systems of betatrons and other
cyclic accelerators.
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Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 35–45, December, 2006. 相似文献
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微放电是制约航天器微波部件功率容量的主要瓶颈之一。以介质微波部件中典型的介质加载平行板波导为例,基于三维粒子模拟分别对仅考虑外加微波场(情况1)、考虑外加微波场和空间电荷(情况2)以及考虑外加微波场、空间电荷和介质表面电荷(情况3)三种情况下微放电演化过程中电子数目、瞬态二次电子发射系数、归一化反射波电压以及介质表面与上金属板之间的间隙电压随时间的变化进行了仿真,并给出了情况3电子分布和介质表面电荷密度随时间的变化过程。在此基础上,明确了空间电荷和介质表面电荷在微放电过程中所起的不同作用:即空间电荷会使微放电达到饱和状态,介质表面电荷则导致微放电饱和状态无法持续,最后自行熄灭。介质表面电荷导致了微放电过程中介质和金属瞬态二次电子发射系数下降速率不一致,归一化反射波电压幅度随时间变化的包络类似于“眼睛”形状、间隙电压类直流偏置、非对称电子能量分布等特殊现象。 相似文献