Novel model of FM-noise conversion in a UMZI using RF external phase modulation of lasers: Theoretical and experimental results

In this paper, we propose and demonstrate a new and original model for theoretical calculation and experimental measurement of the noise power spectral density (NPSD) in phase-modulated optical links. The phase modulation is operated in the RF frequency range by an external phase modulator. The NPSD is derived for the first time in interferometric systems, by considering all effects such as the 1/f FM noise of the laser and white noise applied to light from a 1550 nm DFB laser, with phase modulation. The results show for the first time the influence of the phase modulation index, modulation frequency and interferometric delay in the phase-to-intensity noise conversion. The experimental and simulation results of conversion of FM-noise to intensity noise in an optical link by considering the external RF phase modulation are shown with good agreement.     

Solution of large‐scale weighted least‐squares problems

A sequence of least‐squares problems of the form min_y∥G^1/2(A^T y?h)∥₂, where G is an n×n positive‐definite diagonal weight matrix, and A an m×n (m?n) sparse matrix with some dense columns; has many applications in linear programming, electrical networks, elliptic boundary value problems, and structural analysis. We suggest low‐rank correction preconditioners for such problems, and a mixed solver (a combination of a direct solver and an iterative solver). The numerical results show that our technique for selecting the low‐rank correction matrix is very effective. Copyright © 2002 John Wiley & Sons, Ltd.     

An inner product lemma

Given the operator product BA in which both A and B are symmetric positive‐definite operators, for which symmetric positive‐definite operators C is BA symmetric positive‐definite in the C inner product 〈x, y〉C? This question arises naturally in preconditioned iterative solution methods, and will be answered completely here. Copyright © 2004 John Wiley & Sons, Ltd.     

BEPCII直线加速器相控系统设计研究

为了补偿由于各种因素引起的微波相位漂移,BEPCII直线加速器需要建立微波相位反馈控制系统.能量最大法将用来确定每台功率源的最佳相位.沿直线加速器速调管长廊铺设相位稳定同轴线提供相位参考.现在已经完成了关键部件,如PAD单元、IfA 单元的开发.搭建了相控最小系统对系统进行了验证.     

二维椭圆型方程反问题中优化算法的比较

近年来，决定椭圆型方程系数反问题在地磁、地球物理、冶金和生物等实际问题上有着广泛的应用．本文讨论了二维的决定椭圆型方程系数反问题的数值求解方法．由误差平方和最小原则，这个反问题可化为一个变分问题，并进一步离散化为一个最优化问题，其目标函数依赖于要决定的方程系数．本文着重考察非线性共轭梯度法在此最优化问题数值计算中的表现，并与拟牛顿法作为对比．为了提高算法的效率我们适当选择加快收敛速度的预处理矩阵．同时还考察了线搜索方法的不同对优化算法的影响．数值实验的结果表明，非线性共轭梯度法在这类大规模优化问题中相对于拟牛顿法更有效．     

Differentiability of the Value Function of Nonclassical Optimal Growth Models

We consider an optimal growth (multi-sector) model with nonconvex technology. Using the Clarke results on generalized gradients, we prove that the value function has left and right derivatives with respect to the initial capital stock, without requiring supermodularity assumptions.     

中物院远红外自由电子激光实验研究

中国工程物理研究院基于射频直线加速器技术的远红外自由电子激光(FIR-FEL)实验取得阶段性进展,于2005年3月24晚8时30分首次出光, 并多次重复. 中心波长115μm, 谱宽1%.介绍了实验系统的主要组成部分和主要实验结果.     

X波段盘圈加速结构热阴极微波电子枪的研究

介绍了采用盘圈(DAW)加速结构在11.43GHz下研制的热阴极微波电子枪注入器，分析了注入器中DAW加速结构支撑杆对于微波特性的影响以及加速结构中的模式重叠问题. 针对该结构的强腔间耦合以及次临近耦合不能忽略的特点，对其调谐方法进行了分析研究.给出了该长腔链热阴极微波电子枪注入器的物理设计及粒子动力学计算结果，电子能量为5—6MeV，脉冲流强为40mA，电子束发射度为3.4πmm.mrad. 该微波电子枪的加工焊接已经完成，文中给出了其冷测结果.     

Modeling of RF plasma torch with a metallic tube inserted for reactant injection

Flow, temperature, and electromagnetic (EM) fields in a radio-frequency thermal plasma torch designed for the preparation of superconducting powders or films have been analysed by using a new two-dimensional modeling approach with the electric field intensity as the fundamental EM field variable. The insertion of a stainless steel injection tube into the torch leads to large induction currents in this tube. Although such large induction currents cause pronounced changes of the EM fields near the injection tube, flow and temperature fields are little affected. There exists only one large toroidal vortex in the upper part of the present torch, while the maximum temperature appears at an off-axis location within the coil region.     

三维射频加速腔程序包MAFIA的开发和应用

介绍了三维射频加速器计算机辅助设计(CAD)程序包MAFIA的特点、功能及其应用。用CAD的方法实现了射频加速器特别是非轴对称带耦合腔的加速器的三维腔形设计。同时介绍了节省内存、节约机时的模型方法,使得在中小型机器上运行大程序(八万条)成为可能。文章主要对L波段的加速腔进行了数值模拟,并和实验进行了比较,结果符合较好;通过三维数值模拟及图形模拟的方法比较了各种形状谐振腔的性能;计算分析了输入耦合腔及高阶模耦合器对加速腔电磁场分布等参量的影响;提出了加耦合器后谐振频率改变的补偿方法。