共查询到19条相似文献,搜索用时 55 毫秒
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空间电荷透镜的聚焦特性决定于其电子云的大小、形状和密度分布.本文利用数值与解析方法讨论了这些参量. 相似文献
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给出了强流相对论电子束在磁透镜场中压缩传输系数的理论公式和计算结果,其结果说明能量传输效率随磁透镜比的增大而减小,随阴极处磁感应强度的增大而增大,对于一个特定的系统存在一个能通量密度的极限值。 相似文献
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给出了强流相对论电子束在磁透镜场中压缩传输系数的理论公式和计算结果,其结果说明能量传输效率随磁透镜比的增大而减小,随阴极处磁感应强度的增大而增大,对于一个特定的系统存在一个能通量密度的极限值。 相似文献
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本文报道了对87Rb冷原子云聚焦的微磁透镜实验.磁透镜的核心部件是一个半径为2mm的微型线圈.当冷原子云沿线圈轴向运动到线圈附近时,线圈产生的非均匀磁场会对原子云实现纵向压缩.在线圈电流加载时间为10ms的情况下,原子云纵向尺寸随线圈电流增加先表现为会聚趋势;在某一电流值(0.9A)之后,表现为扩散趋势.与不加载线圈电流的情形相比较,电流为0.9A时的冷原子云纵向尺寸缩小了一个多量级,透镜焦距约为1.3mm.通过同时调节线圈电流的大小和作用时间,可实现对透镜焦距的调节.同时用数值模拟方法模拟了实验过程,模拟结果与实验结果基本符合. 相似文献
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带电粒子在轴对称磁场中一边沿着对称轴向前运动,一边绕对称轴旋转。所以横向运动可以分解为两部分:聚焦运动和子午面的旋转。因此,4维横向传输矩阵可以表示为聚焦矩阵和旋转矩阵的乘积。用旋转矩阵和聚焦矩阵重新推导了总的传输矩阵。然后给出了相应的相椭圆系数矩阵来进一步估算从ECR离子源引出束流的发射度.详细地讨论了束流分布函数的二次矩。 相似文献
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Tight focusing of axially symmetric polarized vortex beams is studied numerically based on vector diffraction theory. The mathematical expressions for the focused fields are derived. Simulation results show that the focused fields and phase distributions at focus are largely influenced by both the polarization order and topological charge of the incident beams. Moreover, focal spots with flat-topped or tightly-focused patterns can be flexibly achieved by carefully choosing the polar- ization order and the topological charge, which confirms the potential of such beams in wide applications, such as optical tweezers, laser printing, lithography, and material processing. 相似文献
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Multiple optical trapping with high-order axially symmetric polarized beams(ASPBs) is studied theoretically,and a scheme based on far-field optical trapping with ASPBs is first proposed.The focused fields and the corresponding gradient forces on Rayleigh dielectric particles are calculated for the scheme.The calculated results indicate that multiple ultra-small focused spots can be achieved,and multiple nanometer-sized particles with refractive index higher than the ambient can be trapped simultaneously near these focused spots,which are expected to enhance the capabilities of traditional optical trapping systems and provide a solution for massive multiple optical trapping of nanometer-sized particles. 相似文献
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A. N. Bogolyubov A. I. Erokhin I. E. Mogilevskii N. E. Shapkina 《Moscow University Physics Bulletin》2009,64(2):124-127
An algorithm is suggested for calculating the resonance frequencies of open dielectric axially symmetric resonators of piecewise constant radius suitable for an arbitrary layered axially symmetric dielectric filling. The resonator is placed into a case with ideally conducting walls of a sufficiently large radius. Cases are analyzed where the resonator structure is partly coated with a perfect conductor. 相似文献
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条纹变像管因其超高时间分辨特性而成为实现皮秒至飞秒量级时间分辨的重要测量仪器.本文设计了一种同时兼顾高时空分辨的行波偏转器前置短磁聚焦条纹变像管.该管型通过减小电子渡越时间以抑制空间电荷效应、采用偏转器前置以及行波偏转方式提高偏转灵敏度,实现整管时空分辨率的大幅提升.利用CST微波工作室有限元法数值计算条纹变像管行波偏转器的通频带宽、偏转灵敏度,结果表明:本设计中的行波偏转器因其较高的通频带宽特性实现了偏转器上的电磁波相速度在很宽频率范围内与电子轴向群速度匹配,产生更有效偏转.利用CST粒子工作室模拟追踪光电子的运行轨迹,通过最佳像面上的时间调制传递函数和空间调制传递函数,计算得到其理论时间分辨率可达220 fs,空间分辨率高于100 lp/mm.同时根据像差定义给出追踪实际电子轨迹的像差计算方法,实现对变像管成像质量评价.最后利用紫外灯对其进行静态测试,获得静态空间分辨率优于35 lp/mm的结果. 相似文献
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A stimulated emission depletion(STED) microscopy scheme using axially symmetric polarized vortex beams is proposed based on unique focusing properties of such kinds of beams. The concept of axially symmetric polarized vortex beams is first introduced, and the basic principle about the scheme is described. Simulation results for several typical beams are then shown, including radially polarized vortex beams, azimuthally polarized vortex beams, and high-order axially symmetric polarized vortex beams. The results indicate that sharper doughnut spots and thus higher resolutions can be achieved, showing more flexibility than previous schemes based on flexible modulation of both phase and polarization for incident beams. 相似文献
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在普通物理光学实验中,焦距的测量通常使用单透镜作为待测透镜,但单透镜存在各种像差,会使测量结果的物理意义变得不清,对此本提出了一些改进意见。 相似文献