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Search Results: 1 - 10 of 47193 matches for " 唐天同 "
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磁浸没透镜的宽束曲轴像差理论
程敏,
电子学报 , 2001,
Abstract: 本文采用宽束曲轴电子光学理论,研究了磁浸没透镜的电子光学特性,得出了主轨迹方程和曲近轴轨迹方程,并利用数学软件Mathematica推导出了其全部二级像差系数.针对轴上磁场分布具有解析表达式的磁浸没透镜,文中还计算了它的曲轴二级像差,并给出了其孔径像差的弥散图形情况,从而得出了磁浸没透镜的特殊的电子光学像差特性.
微分代数方法在静电电子透镜任意高阶像差分析中的应用
程敏,,姚振华
电子学报 , 2002,
Abstract: 微分代数是计算机数值分析领域中的一个非常有效的方法,它以非标准分析理论为基础,可以实现任意高阶微分的准确计算.本文根据微分代数方法的基本原理,将其引入到静电电子透镜的任意阶像差分析的计算中.通过计算例子,可以看出微分代数方法的计算结果非常精确,精度仅受限于机器精度和算法误差.同时结合微分代数方法可以很方便地计算到任意高阶像差的特性,给出了所研究的透镜的全部五阶像差的分布图形.
磁浸没透镜的宽束曲轴像差分析的微分代数方法研究
程敏,,姚振华,王振华
电子学报 , 2002,
Abstract: 微分代数是计算机数值分析领域中的一个非常有效的方法,可以实现任意高阶微分的准确计算.本文根据微分代数方法的基本原理,将其引入到磁浸没透镜的宽束曲轴像差的分析计算中,得到了任意阶曲轴像差的微分代数表达式.文中针对轴上磁场具有某种解析表达式的一个实际的磁浸没透镜系统,利用微分代数的曲轴像差分析方法,计算了它的曲轴像差,并给出了全部二阶和三阶几何像差的分布图形.
变像管相机中空间电荷效应的统计动力学分析
王超,康轶凡,
强激光与粒子束 , 2008,
Abstract: ?从boltzmann积分微分方程出发推出了保守势场中电子数密度按势能的分布规律,即boltzmann统计分布。以此为基础,从统计动力学的角度详细分析了变像管相机中超短电子脉冲内部的空间电荷效应,通过求解poisson方程得出了表征空间电荷效应的两个特征参量:空间电荷密度分布函数和速度分布函数,并对其按电位的动态变化规律进行了定性讨论。结果表明,限制变像管中的低电位区域和其中光电子脉冲从高电位向低电位传输的区域都将有助于优化整个变像管的性能。同时也重新讨论了光电阴极附近强加速场对光电子脉冲时间弥散的抑制作用,最终确定了其物理机制为不等位区间中电子脉冲空间分布的高度集中性。
非线性相移对z-scan曲线对称性的影响
王超,,康轶凡
强激光与粒子束 , 2007,
Abstract: ?基于由光束传输的abcd矩阵得出的z-scan透过率的解析结果,分析了z-scan实验曲线随非线性相移的变化规律。发现随着相移的增加,折射非线性相移比吸收非线性相移对z-scan曲线对称性的影响更大。对于具有强饱和吸收和弱自聚焦特性的非线性介质,其z-scan曲线随非线性折射相移的变小将失去典型的类色散特点。对于1μm厚的zncdse-znse多量子阱,扫描光源采用532nm的基模高斯光束,采用透过率表达式来拟合所得的实验数据,在吸收非线性相移为0.9与耦合因子为-10条件下,推算出三阶非线性吸收系数为2×10-3cm/w,三阶非线性折射系数为8.0×10-8cm2/w,这与j.ma等人的结果吻合。最后对曲线特征参数随非线性相移变化进行了数值计算,得到的曲线所对应的非线性相移与曲线谷位置的乘积近似为一常量,值为0.166。
抑制超短电子脉冲展宽的补偿方法
王超,康轶凡,
强激光与粒子束 , 2008,
Abstract: ?提出了一种有效的利用补偿元件抑制空间电荷效应所致脉冲展宽的方法。此元件为一轴对称的圆柱形空腔,金属侧壁和供脉冲输出的端面金属栅网接地以保持0电位,供脉冲进入空腔的端面小孔的内壁涂导电层并施以正电位,通过选择此端面的介电常数分布而在此端面上形成特定的电位分布。如此形成的补偿元件内部电场能够在不引入附加电子能量弥散的基础上,在空点电荷效应所致脉冲展宽极为严重的纵向和横向这两个主要方向上,均能够有效地抑制空间电荷效应,从而起到补偿电子脉冲展宽的作用。
阴极透镜层流电子枪调制特性
王超,,康晓辉
强激光与粒子束 , 2008,
Abstract: ?通过求解第一类边界条件的拉普拉斯方程,获得了典型的三电极阴极透镜中轴上电位的解析表达式。以此为基础,分析了阴极透镜各几何参数及电位参数对其聚焦性能的影响,得知通过增大调制极电位或其孔径、增加调制极与加速极的间距或缩小调制极与阴极的间距的方法,可以保证在改善初始粒子时间、空间弥散特性的基础上,相对减小轴向电场的非均匀性以减弱其会聚电场强度,从而使带电粒子束在阴极透镜区域中不能形成交叠点,达到构成其中电子运动具有层流性质的阴极透镜层流电子枪的工程应用目的。另外也获得了采用厚度较小的调制极有助于整个电子光学系统性能优化的结论。
SPATIAL SOLITONS IN PHOTOVOLTAIC PHOTOREFRACTIVE CRYSTALS IN AN EXTERNAL BIAS FIELD
有偏压的光伏光折变晶体中的空间孤子

LU KE-QING,TANG TIAN-TONG,
卢克清
,

物理学报 , 1999,
Abstract: Bright and dark spatial solitons are predicted for biased photovoltaic photorefractive crystals, which are due to both the spatially nonuniform screening of the external electric field and the photovoltaic effect. These solitons differ form previously observed photorefractive spatial solitons in their properties. When external electric field is of a certain value, these solitons may be switched from bright to dark both by changing the polarity of the external electric field and by rotating the polarization of the light. In case the effect of the external bias field is much stronger than the photovoltaic effect and the latter can be neglected, these solitons are similar to screening solitons. In case the external bias field is absent, these solitons are similar to photovoltaic solitons in the open-circuit case.
Modeling of Subthreshold Characteristics of Deep-Submicrometer FD Devices
深亚微米FD-SOI器件亚阈模型

程彬杰,邵志标,,沈文正,赵文魁
半导体学报 , 2001,
Abstract: A third order quasi cubic silicon film potential function in the vertical direction is assumed for FD SOI device,and the surface potential formula is obtained via solving the two dimensional Poisson equation in the subthreshold region.The surface potential model in the deep submicrometer FD device is presented by introducting some new parameters to describe the DIBL effect.Based on it,a drain current model in the subthreshold region is developed,which can predict the accurate subthreshold drain current characteristics.The models are verified by comparing with the two dimensional device simulator,MEDICI.
Study on the Optical Near Field of Metal-clad Optical Fiber Probes
金属覆层光纤探针近场特性研究

王学恩,范兆忠,张禄,
光子学报 , 2004,
Abstract: Distributions of the near-field electromagnetic field and its energy density of rotationally symmetrical optical fiber probes used in scanning near-field optical microscopes (SNOM) are numerically studied using finite integration method (FIM). The results indicate that an evanescent wave exists out of the probe and that the polarization direction of the near field is related to that of the excitation field of the fiber probe. An edge enhancement effect,caused by the induced charges on the surface of metal cover,is observed along the polarization direction. The computed results also prove that the resolution of the probe and the electromagnetic energy within the samples are mainly determined by the aperture size of the probe and the distance between the sample and the probe aperture.
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