Detectors and Calibration Concept for the European XFEL

The European X-ray Free Electron Laser (XFEL.EU) is an international research facility presently under construction in the area of Hamburg, Germany, which will start its operation at the end of 2016 [1 M. Altarelli, European X-ray Free Electron Laser, European XFEL GmbH, Technical Design Report (2006). [Google Scholar]]. The superconducting linear accelerator of the facility will deliver electron bunches with an energy of up to 17.5 GeV, arranged in trains of typically 2700 bunches at a repetition rate of 4.5 MHz. Each train will be followed by a gap of 99.4 ms. Spatially coherent X-rays are generated from the electron bunches in a series of undulators based on the Self-Amplified Spontaneous Emission (SASE) process, in three photon beamlines extending over a length of up to 200 m. Each beamline serves two experiments with different scientific goals.     

Characterization of an X‐ray mirror mechanical bender for the European XFEL

One of the classical devices used to tune a mirror on an X‐ray optical setup is a mechanical bender. This is often designed in such a way that the mirror is held with clamps on both ends; a motor is then used to put a torque on the clamps, inducing a cylindrical shape of the mirror surface. A mechanical bender with this design was recently characterized, to bend a 950 mm‐long mirror up to a radius of curvature of 10 km. The characterization was performed using a large‐aperture Fizeau interferometer with an angled incidence setup. Some particular and critical effects were investigated, such as calibration, hysteresis, twisting and long‐term stability.     

纯永磁波荡器磁场计算的三维修正

 用归一化量对纯永磁波荡器的磁场进行三维计算分析,讨论了一般情况下有限磁极宽度的三维修正以及对好场区的影响,给出了磁极宽度对通常二维近似的修正曲线以及在不同磁极宽度下相对场强的横向变化曲线。     

X-Ray Photon Correlation Spectroscopy at the European X-Ray Free-Electron Laser (XFEL) facility

The proposed European X-ray Free-Electron Laser source (XFEL) will provide extremely brilliant (B>10³³ ph/s/mm²/mrad²/0.1% bw) and highly coherent X-ray beams. Due to the pulse structure and the unprecedented brightness one will be able for the first time to study fast dynamics in the time domain, thus giving direct access to the dynamic response function S(Q,t), instead of S(Q,ω), which is of central importance for a variety of phenomena such as fast non-equilibrium dynamics. X-ray Photon Correlation Spectroscopy (XPCS) measures the temporal changes in a speckle pattern produced when coherent light is scattered by a disordered system and therefore allows the measurement of S(Q,t). This article summarizes important aspects of the scientific case for an XPCS instrument at the planned XFEL. New XPCS setups taking account of the XFEL pulse structure are described. To cite this article: G. Grübel, C. R. Physique 9 (2008).     

一种现场大尺寸测量精度的评价方法

针对现场全面评价大尺寸测量仪器精度的特殊性,提出了一种采用多仪器站多控制点的精度评价方法.基于四元数的空问数据配准,将多仪器站的测量数据统一到全局坐标系下,基于控制点坐标不变约束,对测量值进行统计得到测量不确定度,并从中提取仪器内部各传感器单元分量的不确定度.利用多传感器信息融合技术求得最优控制点,减小坐标转换误差对结果的影响.以激光跟踪仪为例进行了仿真和现场实验,结果表明,该方法评价测距和测角小确定度的误差可分别降至1 μm和0.1'以内.     

有轴向磁场的平面摆动器自由电子激光的自发辐射

研究了电子在有轴向磁场的平面摆动器中的辐射，得到了一个较普遍的自发辐射谱表达式，谱线的形状也是由函数ｓｉｎｃ（ｕ）决定，当电子的能量较高或者没摆动器轴线观察时，辐射是满圆极化的，数值分析表明，在平面摆动器中附加适当的轴向磁场，可以提高各次谐波辐射的强度，对于基波和较低次谐波，提高更明显。     

大尺寸全视场目标点的自动定位方法

提出了一种目标点全视场自动定位方法,该方法利用回光反射标志点的强反射特性和目标点特征,采用粗精两级定位自动获取目标点中心.实际操作中只需预先设定相关的阈值参量,可快速获取图像中的所有目标点的图像坐标,极大地提高了视觉测量的效率和自动化程度.对于3 008×2 000 pixel大小、包含约140个目标点的RGB图像,利用该方法定位所有目标点的用时为14.9″,定位准确度为1/10 pixel.     

磁传感器与磁场的测量

在中学物理教学中，研究磁场传统的实验方法是用小磁针显示磁场的方向，用小磁针或铁粉显示磁感线分布．磁针和铁粉用来形象描述磁场功不可没，可对磁感强度的定量研究却显得无能为力．学生也只好在题海中领会感受磁感强度B的大小；1特斯拉有多大?在脑子里只有一个模糊抽象的印象．物理学对电磁现象的研究成果为各行各业提供了先进的检测设备，可是在自身的物理教学中对磁场的实验检测仍停留在4大发明的“司南”时代．近来上海的DIS实验(数字化实验系统)，     

Comparing Spectroscopic Techniques for the Measurement of Phosphorus in Wastewater

Animal and plant wastes contain recoverable phosphorus that can be repurposed as fertilizer. Ultraviolet-visible spectroscopy and inductively coupled plasma optical emission spectroscopy are compared for the measurement of phosphorus in salt solutions, then wastes. There is no impact of nitrate or chloride on phosphate measurements by ultraviolet-visible spectroscopy, but high concentrations interfere with phosphorus measurement by inductively coupled plasma optical emission spectroscopy. Greenhouse and swine waste can be analyzed by either technique, but more dilution is required for analysis by ultraviolet-visible spectroscopy and for swine waste. Swine waste has ～8 times more phosphorus than greenhouse waste and is the more viable waste source for phosphorus recovery.     

基于光纤光栅的磁场测量新方法

提出了一种基于光纤光栅中法拉第效应和测量偏振相关损耗的直接测量磁场的新方法,给出了理论分析和实验结果.当有外加磁场时,光纤光栅中的法拉第效应使两个圆偏振光的传播常量改变,从而导致光纤光栅的偏振相关损耗的变化.仿真结果表明,外加磁场与偏振相关损耗峰值在一定的测量范围内存在线性关系,测量结果对温度变化不敏感.分析了光栅的参量对测量性能的影响.实验中得到该方案测量磁场的灵敏度为7.8e-6B/Gs,利用现有精度为10-6 dB的光矢量分析仪得到最小可测磁场为2 Gs.实验与理论吻合较好.     

Electron Motion in the Three-Dimensional Field of Undulator

In this paper we consider the motion of relativistic electrons in an ideal three-dimensional magnetic field of an undulator. The ideality of the magnetic field means that, on the undulator axis, the field is directed strictly vertically upward and has a strictly sinusoidal shape. In the overwhelming majority of cases, only this leading component of the field is taken into account in calculating the electron trajectory. In this paper, in the equations of motion of an electron in the magnetic field of an undulator, all three components of the field are taken into account, so that the undulator field under consideration satisfies the stationary Maxwell equations. In this case, the differential equations of motion of the electron are solved analytically with the help of perturbation theory, and not by the method of averaging over fast oscillations of the electron, as was done in a number of previous papers. These analytic expressions for trajectories describe the behavior of particles in the focusing magnetic field of an undulator much more completely. An analysis of these expressions shows that the behavior of electrons in such a three-dimensional field of the undulator is much more complicated than what follows from the equations obtained by the averaging method. In particular, there is a cross effect when changes in the initial vertical parameters of the electron trajectory cause changes in the horizontal component of its trajectory and vice versa. A comparison of the solutions obtained analytically with the results of numerical calculations of electron trajectories using the Runge–Kutta method demonstrates their high accuracy.     

Scrolled Production of Large-Scale Continuous Graphene on Copper Foils

We report an efficient and economical way for mass production of large-scale graphene films with high quality and uniformity.By using the designed scrolled copper-graphite structure, a continuous graphene film with typical area of 200 × 39 cm² could be obtained in 15 min, and the production rate of the graphene film and space utilization rate of the CVD reactor can reach 520 cm²·min^-1 and 0.38 cm^-1·min^-1, respectively.Our method provides a g...     

Large-Scale Production of CdSe Nanocrystal by a Continuous Flow Reactor

Organically capped CdSe nanocrystals were successfully produced by a continuous flow reactor in 13 g/h rate as isolated CdSe nanocrystal, using trioctylphosphine oxide (TOPO) both as the capping organic reagent and the high-temperature reaction solvent. Relatively high reaction temperature (e.g. 350°C) was necessary for matured crystal growth. The quality of TOPO (i.e. impurity composition such like phosphonic acids) was also influential on the quality of the resulting CdSe nanocrystal. The continuous flow reactor was able to produce highly-luminescence, monodispersed CdSe nanocrystals, confirmed by transmission electron microscope observation. The production rate was stable at least 1 h to allow over 10 g production.     

Microstructure Measurement Techniques for Studying Electromigration in ULSI Interconnects

Electromigration reliability remains a major threat to microelectronic circuits. Microstructure of a thin film conductor used in integrated circuit affects the electromigration lifetime significantly. A wealth of knowledge is acquired on thin film microstructure and electromigration in metallic interconnects from relevant studies in past few decades. However, it is noticed that the various techniques to measure microstructure-related attributes of thin film metallization are not presented in the context of electromigration, since these measurement techniques have their own importance. On the other hand, aggressive scaling of interconnect line-width down to nano regime, poses new challenges to microstructure characterization techniques. This article connects these two aspects of electromigration study, e.g., the characterization of microstructure and measurement techniques for the influential microstructural attributes especially for Cu-based interconnects. The microstructure-related parameters, attributes, and their impacts on electromigration lifetime are discussed. The sample preparation and various techniques to measure attributes of microstructure are presented in detail. This article describes the current state-of-the-art for the advancement of studying microstructure dependent electromigration reliability.     

Optical Measurement Techniques for Optical Fiber and Waveguide Devices

We describe three major optical characterization methods for fiber and fiber devices. A simple servo controlled scanning fiber-optic confocal microscope is proposed for determining the refractive index profile of an optical fiber. To measure the chromatic dispersion of a short length fiber a Mach-Zehnder fiber interferometer with a novel interferometric distance meter is introduced. At the end, a tomographic method is demonstrated for determining the 2-D stress profile of a fiber.     

非接触法测量距离的研究

本文设计制作了用可闻声波和超声波测距离的两种实验装置,比较了这两种测量方法的优缺点。     

Size Measurement of Small Magnetic Particles

Many different methods for size measurement are known and since they differ in their physical principles, different results are also obtained. In the recent past, there were rapid developments in new measurement techniques and one can now quickly and routinely determine particle sizes in the very fine range. Smaller particle sizes, on the other hand, tend to increase the probability of agglomeration. The measurement of the particle sizes for magnetic materials is not well understood and this paper reports results regarding the size determination of very fine magnetic materials. Because of their dipole moment, these particles tend to agglomerate even more, which in turn causes certain difficulties during the measurements. Wet and dry laser measurement systems were compared and also magnetic materials with different permeabilities in order to establish the influence of individual factors on the measurement process and on the accuracy of the results obtained.     

基于扫频采样的飞秒激光大尺寸测距方法研究

作为一种高精度测量工具,飞秒激光具有优于传统激光技术的特性,已被广泛应用于工业生产、航空航天、科学研究等领域。扫频采样法在很大程度上改善了机械振动、扫描速度过慢等问题,对飞秒激光的绝对测距性能提升有着重要的意义。基于扫频采样原理,提出了一种利用飞秒激光的大尺寸距离测量方法,并对该技术的测量原理、干涉光谱和解调算法等方面进行了研究。首先,根据飞秒激光的锁模生成原理和压电陶瓷的压电效应,介绍了飞秒激光器连续扫描重复频率的方法。在此基础上,结合传统的光学采样法原理,解释了扫频采样法的测距原理,推导并讨论了光纤延迟线的长度对扫描距离的影响。然后,搭建了基于扫频采样的飞秒激光测距系统,在线性导轨上进行了远距离的测量实验,同时设计了基于迈克尔逊干涉原理的He-Ne激光参考光路。根据实验环境修正了空气群折射率,分析了测量距离对光谱条纹峰值和宽度的影响,测量了不同目标位置处的激光扫描距离。在50.4 m的测量范围内,扫描距离从0.56 mm增加到1.12 mm,充分验证了光纤延迟线对提升大尺寸测距能力的重要性。周期性的频率扫描可产生互相关条纹,通过对测量光谱条纹进行希尔伯特变换处理,解算出实时的频率变化量和采样倍乘系数,从而获取被测的距离信息。此外,为了减小系统的时间延迟误差,提高测量的准确性,采用差分原理对算法进行了改进。在希尔伯特算法基础上,分别对频率和距离进行差分处理,解算距离信息。实验结果表明,经过对比,采用基于距离差分的改进算法处理数据,性能结果较好。算法改进后,系统在50 m范围内的测量精度从11 μm提高到4 μm,相对精度从2.2×10-9提高到8×10-8,测距准确性明显提高。通过分析重复性测量数据,并与增量式激光干涉仪结果比对,测量误差的标准差从10 μm提高到2 μm,最大相对稳定性从2×10-9提高到4×10-8,测距稳定性明显提高。因此,该方法有较为优秀的大尺寸测距能力,具有同时实现高精度、大尺寸、快速绝对测距的潜力,在未来的精密光谱测量领域有着很大的前景。