激光微束装置中的聚焦系统

本文提出一种新的激光聚焦系统,用于激光微束装置能获得小于1μm的聚焦光斑。它由一个具有一定倍率的空间滤波系统和一组短焦距、长工作距离的聚焦物镜组成。文中最后给出了测试结果。     

The Stationary Nonlinear Boltzmann Equation in a Couette Setting with Multiple, Isolated L q -solutions and Hydrodynamic Limits

This paper studies the stationary nonlinear Boltzmann equation for hard forces, in a Couette setting between two coaxial, rotating cylinders with given indata of Maxwellian type on the cylinders. A priori estimates are obtained mainly in L², leading to multiple, isolated solutions together with a hydrodynamic limit control, based on asymptotic expansions together with a rest term.     

The Asymptotic Behavior of the Ergodic Measure of a Glauber + Kawasaki model

We consider an interacting particle system given by the Glauber + Kawasaki dynamics. It is known that this process has a reaction diffusion equation as hydrodynamic limit. The ergodicity of this process in the presence of a metastable state (double well potential) was recently proved by S. Brassesco et al. In this Letter we prove that, in the limit, as ε → 0, the expected value of each spin converges to the global minimizer of the potential. We also prove decay of correlations of the ergodic measure.AMS Subject Classification (2000). 60K35 (82C22, 82C31)This work was partially supported by CNPq     

战略性绩效管理系统设计中的决策问题

战略性绩效管理系统的设计中存在很多决策问题,本以一家制造业公司为例,介绍了应用Nash均衡建立绩效监察博弈模型。确定组织的绩效系统规模;通过AHP方法的创新应用,确定组织的关键业务领域,同时对组织关键业绩指标分类分层设计的思路做了简要阐述。     

On the Theory of X-Ray Diffractional Laue Focusing on Two Bent Crystals

The Laue focusing of a spherical x-ray wave onto dynamical diffraction by a double-bent crystal system is studied. The geometrical equations of two-dimensional Laue focusing and the intensity distribution formula are derived. A high sensitivity of the two-dimensional Laue focusing to the crystal thickness and bending radii difference is revealed. It is shown that this sensitivity can be used to control the crystal thickness with accuracy up to 100 and bending radii up to 10^-2 m. The focusing process of the spherical wave inside crystals as well as in vacuum is investigated. The possibility of using the two-crystal Laue system as a lens for x-ray microscopy is studied. The spectral characteristics of a twice-diffracted wave are discussed. The spectral resolution is demonstrated to be 10⁶.     

Sand Erosion in Axial Flow Conditions

A mathematical model of sand erosion in axial flow conditions is presented. The basic mass balance equations and sand erosion constitutive equation were given in Vardoulakis et al. (1996). As opposed to reference Vardoulakis et al. (1996), we consider here the extreme case where convection is null and hydrodynamic dispersion dominates. In addition, Brinkman's extension of Darcy's law is adopted to account for a smooth transition between channel flow and Darcian flow. The set of governing PDE's is presented in dimensionless form and is solved numerically. In concordance with the basic constitutive equation for erosion kinetics, the analysis shows that erosion progresses in time as a front of high transport concentration. This result is justified by the highly non-linear character of the erosion source term which dominates in the diffusion-like governing equation.     

Second class particles as microscopic characteristics in totally asymmetric nearest-neighbor -exclusion processes

We prove laws of large numbers for a second class particle in one-dimensional totally asymmetric -exclusion processes, under hydrodynamic Euler scaling. The assumption required is that initially the ambient particle configuration converges to a limiting profile. The macroscopic trajectories of second class particles are characteristics and shocks of the conservation law of the particle density. The proof uses a variational representation of a second class particle, to overcome the problem of lack of information about invariant distributions. But we cannot rule out the possibility that the flux function of the conservation law may be neither differentiable nor strictly concave. To give a complete picture we discuss the construction, uniqueness, and other properties of the weak solution that the particle density obeys.

     

Progress in direct-drive inertial confinement fusion research at the laboratory for laser energetics

Direct-drive inertial confinement fusion (ICF) is expected to demonstrate high gain on the National Ignition Facility (NIF) in the next decade and is a leading candidate for inertial fusion energy production. The demonstration of high areal densities in hydrodynamically scaled cryogenic DT or D₂ implosions with neutron yields that are a significant fraction of the “clean” 1-D predictions will validate the ignition-equivalent direct-drive target performance on the OMEGA laser at the Laboratory for Laser Energetics (LLE). This paper highlights the recent experimental and theoretical progress leading toward achieving this validation in the next few years. The NIF will initially be configured for X-ray drive and with no beams placed at the target equator to provide a symmetric irradiation of a direct-drive capsule. LLE is developing the “polar-direct-drive” (PDD) approach that repoints beams toward the target equator. Initial 2-D simulations have shown ignition. A unique “Saturn-like” plastic ring around the equator refracts the laser light incident near the equator toward the target, improving the drive uniformity. LLE is currently constructing the multibeam, 2.6-kJ/beam, petawatt laser system OMEGA EP. Integrated fast-ignition experiments, combining the OMEGA EP and OMEGA Laser Systems, will begin in FY08.     

环形光束的非线性传输及聚焦特性研究

针对用于产生光镊的环形光束,利用分步傅里叶-贝塞尔变换算法,对二维环形超高斯光束的非线性传输及聚焦过程进行了数值模拟,给出了环形光束聚焦场附近的光强分布,并分析了非线性调制对聚焦性质(包括焦面中心光强、焦面光强的横向分布、轴上光强和光束质量)的影响.研究表明,从聚焦角度来看,非线性调制中的位相调制比振幅调制对环形光束聚焦性质的影响程度要大;从非线性传输角度来看,随着非线性介质长度的增加,位相调制和振幅调制对环形光束聚焦性质各有不同程度的加剧,其中非线性作用对振幅调制的影响要比位相调制明显.     

LD泵浦腔外倍频高转换效率Nd3+∶GdVO4固体激光器

通过合理设计精密调控各元件和温控电流，得到了平均功率为70 mW，脉冲宽度为22 ns，重复频率为14 kHz，峰值功率高达230 W的Nd3+∶GdVO4/Cr4+YAG红外脉冲激光器.先采用双凸透镜组合成的望远镜系统对1 063 nm的红外激光进行扩束，再对该光束聚焦，最后经双轴晶体LBO倍频后，得到了平均功率为40.6 mW，脉冲宽度为16 ns，重复频率为14 kHz，峰值功率高达181 W的绿光激光输出，1063 nm→532 nm的转换效率高达58%.测量了532 nm的光谱线宽曲线.解释了该聚焦方法比单一薄透镜效果明显好的原因，并指出了这种聚焦方法的使用对象.