部分相干光在大气湍流中斜程传输路径上的展宽与漂移

基于Andrews和Philips经典漂移方差模型,利用部分相干高斯-谢尔光束在大气湍流中斜程传输的光束扩展半径,推导出考虑外尺度情况时部分相干高斯-谢尔光束斜程情况下的漂移方差表达式,应用随高度变化的大气结构常量模型进行数值计算,对比分析了部分相干光和完全相干光在大气湍流中的展宽和漂移特性.结果表明:相同的传输条件下,部分相干光比完全相干光的光束扩展更迅速,受湍流的影响也更小;初始半径越大,接收机高度越高,光束的扩展效应越小;随着传输距离的增大,光束的质心漂移方差随光束初始半径的增大而减小,不同相干性的光束漂移方差变化很小;完全相干光的光束漂移受波长的影响较小,而部分相干光的波长越长,漂移越明显.     

束流位置监测系统的研制及其在国家同步辐射实验室二期工程中的应用

 介绍一种储存环束流位置监测系统的标定装置。这套标定装置是为NSRL二期工程储存环注入段真空盒改造而研制的。系统的标定精度达±0.01mm。该装置已用于新增注入段真空管的束流位置探测器的定标，获得了探头定标值，并根据其拟合和计算结果对注入段真空管进行了筛选，被选中的真空管已装入储存环注入段。     

Effect of annular apodization and pupil beam parameter in the focal region of high NA lens

Focusing properties of the radially polarized axisymmetric Bessel-modulated Gaussian beam with quadratic radial dependence (QBG beam) and annular aperture are investigated theoretically by vector diffraction theory. Simulation results show that the intensity distribution in the focal region of the radially polarized axisymmetric QBG beam can be adjusted considerably by small beam parameter (μ) and annular aperture (δ). When μ increases, the focal spot may change to focal hole and changes focal pattern remarkably. On introducing annular aperture, focus can split or extends along the optical axis for different μ. In this paper, we have shown the generation of the focal spot, dark focal spot, focal split and increase in focal depth in the axial direction of the incident beam propagating through the aligned optical system.     

神龙一号电子束质心运动测量研究

 在强流直线感应加速器中,电子束质心位置的控制是一项重要技术,要达到较好的控制效果,前提是对电子束质心位置进行准确的测量和定位。针对具有时间分辨的电子束质心位置的测量和确定,介绍了测量实验系统的建立和数据处理两个方面的研究工作。该处理方法在实际应用时能够将电子束质心位置的误差控制在1～2个像素内。用高速分幅相机以10 ns的时间间隔、3 ns的曝光时间获得了神龙一号加速器在漂移段出口处的电子束质心运动情况。结果表明：束的质心主要在半径为0.5 mm的区域内运动,束斑直径dFWHM值分别为8.4,8.8,8.5,9.3和7.6 mm,测量结果可以为束的调控提供准确参数。     

沿Z型光传输管道轴向吹气对激光传输的影响

针对在Z型管道中传输的高能量密度激光束受到的气体热效应问题,采用光波标量衍射方程计算光传输、N-S方程计算管道内流场,仿真计算了以不同的速度沿管道轴向吹入对激光能量无吸收的气体时,由于气流扰动对出射光束远场光斑质量的影响。结果表明,在采用纵向吹气减小气体热效应对光束传输的影响时,应尽可能采用大气量、低流速的方案,既有利于排空管道中的杂质气体,减小气体热效应,又有利于减小管道中流场密度分布的不均匀性,从而保证出射光束的质量。     

光学渡越辐射测量中能量分辨精度分析

 基于光学渡越辐射原理的用于高能强流电子束束流参数在线测量及诊断系统,具有时间响应快、分辨率高等特点,可以测量电子束的束剖面、发散角、能量等多个参数。分析了测量系统的结构参数（包括了透镜的焦距、成像面位置、CCD像元尺寸）对电子束能量测量精度的影响,并在理论上模拟了电子束的发散角的影响。还根据系统数据的特点,阐述了数据噪声对能量测量结果精度的影响,指出了光学渡越辐射测量中电子束能量分辨精度受到多种因素的影响,需要在数据处理时考虑修正。     

A volume integral equation method for periodic scattering problems for anisotropic Maxwell's equations

This paper presents a volume integral equation method for an electromagnetic scattering problem for three-dimensional Maxwell's equations in the presence of a biperiodic, anisotropic, and possibly discontinuous dielectric scatterer. Such scattering problem can be reformulated as a strongly singular volume integral equation (i.e., integral operators that fail to be weakly singular). In this paper, we firstly prove that the strongly singular volume integral equation satisfies a Gårding-type estimate in standard Sobolev spaces. Secondly, we rigorously analyze a spectral Galerkin method for solving the scattering problem. This method relies on the periodization technique of Gennadi Vainikko that allows us to efficiently evaluate the periodized integral operators on trigonometric polynomials using the fast Fourier transform (FFT). The main advantage of the method is its simple implementation that avoids for instance the need to compute quasiperiodic Green's functions. We prove that the numerical solution of the spectral Galerkin method applied to the periodized integral equation converges quasioptimally to the solution of the scattering problem. Some numerical examples are provided for examining the performance of the method.     

飞秒激光微细加工中光耦合器参数的数值模拟

用有限差分迭代求解光束传输方程,对1×2(Y型)耦合器和2×2(X型)耦合器分路的夹角大小对分路中光束分配比例的影响进行了模拟研究.模拟结果显示：耦合器夹角控制在一定的范围内,对分路中光束能量分配影响不大;2×2耦合器对分路夹角以及波导宽度的变化敏感.为飞秒激光加工光纤无源器件的可行性做了理论上的分析.     

平面光波导器件时域有限差分束传输法分析中边界和初始条件的处理

从慢变包络（SVEA）时域光传输方程出发,对比了综合道格拉斯（GD）和传统的中心差分（CN）两种离散化格式,指出GD法比CN法精度有了很大提高.重点讨论了GD法的TD-BPM边界处理问题,给出了吸收边界和透明边界离散的显式和隐式表达式,分析并确定了交替方向隐式法（ADIM）的边界处理方式;同时,对激励源加入的连接边界进行了仔细讨论.结果表明对于隐式GD-TD-BPM法边界处理应采用隐式,中间激励更能反映光波导反射场的情况.     

Periodic Solutions for a Damped Rayleigh Beam Model with Time Delay

Vibrations of a beam can be described as an Euler-Bernoulli beam,or as a Rayleigh beam or as a Timoshenko beam. In this paper, we establish the existence of periodic solutions in time for a damped Rayleigh beam model with time delay, which is treated as a bifurcation parameter. The main proof is based on a Lyapunov-Schmidt reduction together with the classical implicit function theorem. Moreover, we give a sufficient condition for a direction of bifurcation.