Conceptual design of the vacuum system of the Spanish synchrotron light source (ALBA) storage ring

ALBA will be a third generation synchrotron light facility to be built near Barcelona (Spain). The design phase of ALBA is almost completed and the first components are ready to be ordered. Commissioning of the storage ring is foreseen to start at the end of 2008. The circumference of the storage ring of ALBA is 268.8 m and it will be divided into 16 vacuum sections by ultra high vacuum (UHV) gate valves. The vacuum chamber will be made of stainless steel with vertical aperture of 28 mm and 72 mm width. The vacuum chamber will be connected to an antechamber with a slot of 10 mm height. The antechamber will have the crotch absorbers which will absorb the unwanted synchrotron radiation. The pumping will be by sputter ion pumps (SIP), NEG pumps and titanium sublimation pumps (TSP), with an overall pumping speed from SIP of 57,400 l/s. This will maintain an average dynamic pressure of around 1 × 10⁻⁹ mbar to achieve a beam lifetime >15 h at the designed current.     

Storage ring vacuum system pressure modelling at Diamond

Two complementary vacuum system simulation programs, “MCTPVac” and “Pressure Profile”, have been developed and tested at Diamond and used to model sections of the Diamond storage ring. The MCTPVac program implements the Monte Carlo Test Particle (MCTP) method in 3 dimensions. The Pressure Profile program uses a 1-dimensional method based on a steady-state diffusion equation. The validity of the MCTPVac program is confirmed by comparison with previously-published results and formulae for simple geometries. The pressure predictions made by the two methods for the Diamond storage ring injection straight are then compared with each other and to actual observed pressures.     

Improvement of beam lifetime and vacuum system of the PF-AR

Successive improvements have been performed on the vacuum system for the Photon Factory Advanced Ring (PF-AR) at the High Energy Accelerator Research Organization (KEK). The main purpose is to prolong electron beam lifetime for stable operation as an intense pulsed X-ray source. In the past three years, a total of 61 sputter ion pumps (SIPs) were additionally installed, and the increased effective pumping speed amounts to 13% of total. Comparison between calculated and observed beam lifetimes indicates that the lifetime is restricted mainly by the residual gas scatterings and that improvement of the vacuum will realize still longer lifetime. Sudden beam lifetime drops caused by dust trappings have been investigated for many years. The frequency of the lifetime drops has decreased as operation time elapsed after a large-scale reconstruction. Effect of distributed ion pumps (DIPs) on the lifetime drops has also been investigated experimentally.     

北京正负电子对撞机储存环真空系统运行和改进

目前BEPC储存环真空系统已经运行了十五年,系统运行良好,当有束流存在时,储存环的平均动态压强低于2.6×10-7Pa,束流寿命大于10 h。尽管真空系统部件多,结构复杂,但由于真空泄漏造成停机的次数并不多,大多数的泄漏能在抽真空和系统检漏期间排除。为了提高北京正负电子对撞机的性能,BEPC储存环真空系统进行了一系列的改进,例如,重新改造铝真空盒用来引出同步辐射光束线,在正负电子对撞区安装NEG泵来提高真空度。特别是真空内的扭摆磁铁被安装到储存环真空系统,通过在永久磁块表面镀氮化钛和合理的排气技术,静态压强已经达到了2.6×10-8Pa。     

13 years’ operational experience of SPring-8 vacuum system

The first electron beam was stored in SPring-8 storage ring in March 1997. An overview of the 13 years’ operational experience concerning the vacuum system of the SPring-8 storage ring is presented. The evolution of the vacuum system and their performance are summarized. Moreover, the main vacuum failures and their impact on accelerator operation are described in detail. We analyze the relationship between the difference types of vacuum failure and downtime of user experiment.     

Calculation of the pressure in the unit-cell vacuum system of Taiwan Photon Source

Taiwan Photon Source is a third-generation 3-GeV synchrotron light source under construction. The electron storage ring of circumference 518.4 m contains 24 unit cells and 24 long straight sections. Each cell of length about 14 m contains two bending chambers and two short straight chambers. To estimate the pressure distribution in the cell vacuum system, a program combining an iterative method and a Monte-Carlo method was used to calculate the pressure. In the modeling, the rate of thermal outgassing of the chamber surfaces and the yield of photon-stimulated desorption of the absorbers are obtained from the experimental results. To provide the effective pumping speed of various pumps that depends on the gas, the composition of residual gases from photon-stimulated desorption was assumed to be 80% H₂ and 20% CO. The pressure calculation for the vacuum cell compares the beam cleaning efficiency during the early commissioning stage when the accumulated beam dose attained 1 A h and 100 A h. The effects of the confined pumping design are evaluated through the modeling to assess whether the commissioning can be accelerated. The result of the pressure calculation obtained with the Monte-Carlo method shows that a mean pressure rise per beam current at 1.9 × 10⁻¹⁰ Pa mA⁻¹ after beam cleaning to a beam dose 100 A h is reasonable and within typical specifications of the synchrotron light source.     

水环离心真空泵在氧气充装系统中的应用

为保证气瓶充装的安全性,武钢氧气公司在新建氧气充装站时配置了一套气瓶抽真空装置。介绍选用的水环离心真空泵的工作原理和技术参数以及氧气充装系统的工艺流程。使用效果证明,在氧气充装系统安装气瓶抽真空装置,不仅可以降低氧气瓶发生化学爆炸的危险性,而且可以提高产品合格率。     

车灯线光源的优化设计方案

本问题是一个车灯线光源的优化设计问题。 首先,我们建立了一个连续的数学模型来描述这个优化问题,此模型研究了线光源上任意一点发出的光线 经过抛物面反射后到达光屏的情况,对于给定的考察点(B或C)得到一个联系该点与光的发射点,反射点这3 个点关系的方程组。由于光在传播过程中会有发散的现象,我们用Jacobi行列式做了一个变换来描述这种散射。 根据C点的光强度必须大于一个确定的值(文中设为1),B点的光强度必须大于该值的2倍的约束条件将这个 问题抽象成一个非线性规划问题。 由于解非线性规划问题是很复杂的过程,我们选择了将连续模型简化成一个离散模型。但是离散模型将光 离散成一条一条光线时,一般不能考虑光在传播过程中的散射问题。根据我们连续模型中用Jacobi行列式算出 的结果知可以考虑光在传播过程中的散射问题,但是Jacobi行列式是很难求出来的,为了解决这个困难我们将光 的散射用连续的方法做了一个简化。简化的方法是用向量投影的方法粗略作出了两个面积微元之间的关系,从 而得到了光线打在光屏上的散射效果与光线的起始单位方向向量和该光线经抛物面反射时的反射点的坐标的 关系。 运用以上的离散模型的算法,得到最优的线光源长度为3.39mm。     

LED背光源发展透视

液晶显示器（LCD）现在已经广泛应用于电视、计算机、手机、监控器等电器上，但液晶本身并不发光，因此需要背光照明。目前多数LCD采用冷阴极射线荧光灯（CCFL）作为背光源，但其亮度输出均匀度差，而且使用寿命不长；使用LED作为LCD的背光源，可以缩小LCD的体积，提高其可靠性和稳定性，并大大延长其使用寿命。本文详述LED作为LCD背光源的种种优缺点和发展趋势。     

Dynamical model of total and partial pressures in a vacuum system due to intermittent desorption

The dynamical characteristics of a vacuum system in respect of pressure are critical for studying the dynamical desorption processes such as those produced by mechanically stimulated desorption in vacuum. In the present work, a mathematical model of the instant pressure in a vacuum system has been developed assuming an intermittent square-wave desorbed gas flow. In this case, the duration of the pressure transient is proposed to be used as a generalized criterion of the rate of the desorbed gas flow and, consequently, of the instant pressure behaviour. The dependences of the transient duration on the pumping speed, system volume, molar mass of the desorbed gas as well as on the period and the on-off ratio of the desorption process have been revealed. The developed model made no assumptions on the physical nature of the gas source, i.e. desorption, leaking, etc., and can be used for different applications.     

Improvement of the beam lifetime by applying an rf electric kick field in the compact storage ring

The lifetime of the stored electron beam in the compact storage ring AURORA is governed by the Touchek effect. It has been shown that it is appreciably increased by applying a vertical rf kick field to the electron beam without giving harmful effect to the beam stability. Interferometric measurement of the radiation beam profile showed an increase in the beam size, indicating the reduction of the Touchek effect. Application of the field with increase in power has induced collective excitation of the betatron oscillation.     

基于SMS法的大功率COB光源窄光束设计

针对集成光源难以实现小发光角的问题,提出了一种大功率COB光源实现窄光束的设计方法。根据COB光源的出射光分布以及预设的光分布范围选用折射-折射(RR)系统。以选定的COB光源的光谱分布及配光曲线为标准建立光源模型,由复合抛物面(CPC)实现朗伯光源60°的聚光之后,再利用光学扩展量守恒以及同步多曲面方法(SMS)求得透镜前后两个曲面轮廓上点的坐标,进行曲线拟合获得轮廓曲线,进而得到透镜的三维模型。采用光学仿真软件对系统进行光线追迹,结果表明:系统在出光口处的发散角控制在30°之内,半光强度角为11.336°,整体光效达到89.398%,效果良好。     

直读光谱双光源法在炼钢分析中的应用

介绍了以双光源激发试样与一组曲线分析多种钢种的方法，其特点是省时省力、快速准确。     

大靶面光幕靶中发光二极管阵列线光源的设计

采用发光二极管阵列构造线了一种大尺度线光源．文中分析了发光二极管阵列光源能量在空间上的分布,用光照度计实测能量分布数据．以二维坐标给出了能量平面分布图．设计的线光源满足大靶面弹丸测速光幕靶的要求,文中给出了在光幕靶接收器件处阵列线光源光能量的计算公式．实验验证了分析的正确性．     

基于光源平移恢复物体法线和材质的算法

提出了一种基于光源平移恢复物体法线和材质的算法.光源平移时获得一组输入图像.根据输入图像将物体表面上的点分成纯漫反射点和混合点(包含漫反射和镜面反射的点).首先,根据镜面反射的原理求出混合点的法线.然后根据求出的法线用全局优化的迭代方法来恢复物体的材质.最后,根据不同输入图像中光源与物体的相对位置的不同,通过一个三角函数来恢复物体表面纯漫反射点的法线.分析对比实验结果和场景的真实参数表明,算法能够有效地恢复物体的法线和材质.     

手指静脉识别系统矩形阵列光源特性分析及优化设计

手指静脉图像质量的高低直接影响手指静脉的识别效率。针对单个近红外LED的光照均匀度相对较差,如何利用多个近红外LED构造一个高质量的光源进行了研究。讨论了矩形阵列光源的结构、空间、形状等参数对静脉图像影响,利用斯派罗法则对各种参数极值找出最优解,再结合手指个体的差异和指型特性,设计照度面为25mm×25mm矩形光源阵列。通过对比实验,利用最优参数设计的阵列光源,能够采集到高质量的手指静脉图像,为手指静脉采集设备光源设计提供参考,同时为后续的手指静脉图像的识别打下基础。     

LED光源在航站楼节能减排中的应用实践

为响应国家节能减排的号召,根据航站楼区域的特点,利用LED光源的优点,通过各种比较和试验分析,更换航站楼贵宾室小灯杯光源,达到节能减排的目的。     

Wake field analysis and modelling of microwave instability in the ILC damping ring

Wake field simulations are performed for given technical designs of the vacuum chamber components for the 6.4 km ILC damping ring, in order to calculate longitudinal wake functions. Modelling of the microwave instability based on multi-turn tracking with many particles is described. A comparison is presented between the potential well distortion found from solving the Haissinski equation and the results of tracking simulations. The threshold for the microwave instability is found for the given designs and lattice parameters.     

关于“车灯线光源的优化设计”问题的光学思路

本文运用光源的朗白定律、光线反射定律的向量方程、照度分布和同心光束等光学方法,并且对近似平行光束进 行家散光束分析,讨论了车灯线光源的优化设计问题的解题思路。     

Design and storage cycle time analysis for the automated storage system with a conveyor and a rotary rack

In this paper, we analyse the performance of an automated Work-In-Process (WIP) storage system consisting of a conveyor and a rotary rack. The stability condition and the expected storage cycle time are derived to analyse the performance of the WIP storage system. As part of the storage cycle time analysis, the derived expected waiting times at the conveyor and the rotary rack are important performance measures that can be used for buffer-sizing purpose in such systems. Given the fixed storage space of the rotary rack, we also develop a heuristic approach to determine the near optimum ‘shape’ of the rotary rack so that the expected storage cycle time is minimized. Numerical results are presented to examine the storage cycle time model and the proposed shape design. The analytical model introduces a simple approach over simulation with acceptable accuracy; it is useful when designing such WIP storage systems. Moreover, it can be expanded to model more complex systems. The derived model also provides insightful information on the design parameters that a typical simulation tool can hardly provide.