Integrating in situ high pressure small and wide angle synchrotron x-ray scattering for exploiting new physics of nanoparticle supercrystals

Combined small and wide angle synchrotron x-ray scattering (SAXS and WAXS) techniques have been developed for in situ high pressure samples, enabling exploration of the atomic structure and nanoscale superstructure phase relations. These studies can then be used to find connections between nanoparticle surfaces and internal atomic arrangements. We developed a four-axis control system for the detector, which we then employed for the study of two supercrystals assembled from 5 nm Fe(3)O(4) and 10 nm Au nanoparticles. We optimized the x-ray energy and the sample-to-detector distance to facilitate simultaneous collection of both SAXS and WAXS. We further performed in situ high pressure SAXS and WAXS on a cubic supercrystal assembled from 4 nm wurtzite-structure CdSe nanoparticles. While wurtzite-structure CdSe nanoparticles transform into a rocksalt structure at 6.2 GPa, the cubic superstructure develops into a lamellarlike mesostructure at 9.6 GPa. Nanoparticle coupling and interaction could be enhanced, thus reducing the compressibility of the interparticle spacing above ～3?GPa. At ～6.2?GPa, the wurtzite-to-rocksalt phase transformation results in a noticeable drop of interparticle spacing. Above 6.2 GPa, a combined effect from denser CdSe nanoparticle causes the interparticle spacing to expand. These findings could be related to a series of changes including the surface structure, electronic and mechanical properties, and strain distribution of CdSe under pressure. This technique opens the way for exploring the new physics of nanoparticles and self-assembled superlattices.     

Grazing incidence wide angle x-ray scattering at the wiggler beamline BW4 of HASYLAB

We present an upgrade of the available measurement techniques at the wiggler beamline BW4 of the Hamburger Synchrotronstrahlungslabor (HASYLAB) to grazing incidence wide angle x-ray scattering (GIWAXS). GIWAXS refers to an x-ray diffraction method, which, based on the measurement geometry, is perfectly suited for the investigation of the material crystallinity of surfaces and thin films. It is shown that the overall experimental GIWAXS setup employing a movable CCD-detector provides the capability of reliable and reproducible diffraction measurements in grazing incidence geometry. Furthermore, the potential usage of an additional detector enables the simultaneous or successive measurement of GIWAXS and grazing incidence small angle x-ray scattering (GISAXS). The new capability is illustrated by the microbeam GIWAXS measurement of a thin film of the conjugated polymer poly(3-octylthiophene) (P3OT). The investigation reveals the semicrystalline nature of the P3OT film by a clear identification of the wide angle scattering reflexes up to the third order in the [100]-direction as well as the first order in the [010]-direction. The corresponding microbeam GISAXS measurement on the present morphology complements the characterization yielding the complete sample information from subnanometer up to micrometer length scales.     

Calibration of instrument and sample parameters for small angle X-ray scattering

A method for calibrating the parameters of a small angle X-ray scattering instrument using the diffraction ring of a standard sample is presented. A generalized geometric model for small angle X-ray scattering was constructed and detailed mathematical derivations presented to solve for the relevant instrument parameters, which were then used to convert two-dimensional small angle X-ray scattering data to standard curves. The method is valid regardless whether the detector photosensitive plane is perpendicular or tilted with respect to the beam. Small angle X-ray scattering was performed using standard calibration samples to validate the methodology.     

A high pressure cell for small angle neutron scattering up to 500 MPa in combination with light scattering to investigate liquid samples

We report on a high pressure cell to use with small angle neutron scattering (SANS) in a pressure range up to 500 MPa. The cell offers the new possibility to investigate liquid samples by a specially designed sample chamber, which allows changing of samples relatively easily. Since the cell construction uses sapphire as window material, also light scattering investigations can be performed simultaneously to the SANS measurements. In this article we describe the construction of a high pressure cell and we demonstrate the applicability of the construction for SANS in combination with dynamic light scattering showing data on the biological molecule lysozyme.     

An alternative method for measuring small displacements with differential phase difference of dual-prism and heterodyne interferometry

This study proposes an optical method for measuring small displacements. In this method, two semispherical prisms are used as test apparatuses. Because testing lights inside the prisms are at polarization angles, the phase difference can be differentially magnified twice and the measurement resolution can be greatly increased. Furthermore, using common-path heterodyne interferometery ensures that this method is simple to implement, high accurate, and high stability against the vibration of the surrounding environment. The capability of this method was demonstrated with a sensitivity of 42.92°/mm and a resolution of 23.29 nm.     

新型轻武器火控系统测角仪的研究

为提高轻武器的打击精度,为火控系统设计了一种新型测角仪.首次采用光电轴角编码器作为角度传感器.系统采用三个编码器,分别对榴弹发射器的枪管高低角,智能光学瞄具的高低角和枪管的水平位置给出15位二进制实时角度值,高低方向自动测角,水平方向自动测速,测角精度＜80 s.实验结果验证了系统设计的正确性,距离1640 m的射击精度＜15 m,符合战术指标要求.     

光散射法测试粒径的一种优化反演组合算法

在目前常用的激光粒度仪反演算方法的优点和缺点基础上,为了实现各种方法的稳定性与准确性的统一,提出一种基于退火演化算法和遗传算法组合的随机反演方法,该方法具有更强的全局收敛性,也具有对粒径分布形状不敏感、抗噪声能力强等优点。该算法能对具有单峰及双峰分布形式的颗粒尺寸进行精确求解,并获得合理的颗粒粒径分布结果。     

使用山嵛酸银标定中子小角散射谱仪的关键参数

为了快速标定中子小角散射谱仪的关键参数:速度选择器的选择波长和波长分辨率以及谱仪布局下的Q分辨率,采用实验方法对山嵛酸银粉末的中子小角散射实验数据进行了拟合.首先,确定谱仪布局,包括准直光阑孔径大小、准直长度、样品到探测器之间的距离;其次,在中子小角散射谱仪的机械速度选择器设置在3 000、4 000、5 000和6 000r·min-1 4种不同转速下,测定山嵛酸银粉末的中子小角散射谱;最后,对实验数据进行反演分析.通过分析,计算出该机械速度选择器常数为2 329.2 r· m-1·nm,从而得到了4种不同转速所对应的选择波长分别为0.776、0.582、0.466、0.388 nm;通过对实验数据的拟合还得到了该速度选择器的波长分辨率(23.75％),以及在此谱仪布局下的Q分辨率曲线.结果表明,使用山嵛酸银粉末的中子小角散射能够较好地标定谱仪的关键参数,从而支持对中子小角散射数据的正确分析和反演.     

Thermal quenching sample chamber for grazing incidence small angle x-ray scattering studies of polymer films

The second generation of a sample chamber designed for in situ measurement of temperature- and time-dependent polymer film nanostructure using the method of grazing incidence small angle x-ray scattering is presented. An increased operating temperature limit (from 260 to 400 degrees C) with precise control (+/-0.1 degrees C) at fixed temperatures as well as a fourfold increase in maximum instantaneous cooling rate (up to 73 degrees C/s) relative to the first generation chamber [M. N. Groves et al, J. Appl. Crystallogr. 39, 120 (2006)] are reported. Thermal quenches from 220 to 90 degrees C are shown to be reproducible to within +/-1 degrees C of the final temperature. Experimental tests on spin-coated films of symmetric diblock styrene-butadiene copolymer demonstrate the ability to resolve the kinetics of orientation of lamellar domains parallel to the silicon substrate, distinct from the initial formation of randomly oriented lamellar domains immediately following the thermal quench.     

Optical fiber sensor for small angle and infinite angle detection

An optical fiber angle sensor that consists of a cam, linear displacement attenuators, and a sensitive Fabry-Perot cavity (FPC), is demonstrated to simultaneously measure small angle and infinite angle with high resolution. When the cam is driven to rotate by a fixed rotary shaft, a linear displacement transformed from an angle will be further attenuated by linear displacement attenuators and will subsequently modulate the FPC, which causes the reflected interference intensity of FPC to vary. By using the method of interferometric fringe counting, we can measure an infinite angle accurately and continuously. Moreover, a small angle measurement can be performed in a locally linear region. Experimental results show that two resolutions of 0.5 and 1.5 s in the angle range of 0.1944 degrees and 3.5496 degrees are achieved, respectively.     

广角极光成像仪滤光片的热设计及试验

针对广角极光成像仪对其光学系统温度的特殊需求,对成像仪使用的高温滤光片进行了热设计及相关试验。介绍了广角极光成像仪的光机结构,尤其是滤光片组件的结构。通过建立传导和辐射热阻的计算方程组,分析了由滤光片到镜筒整个换热路径中存在的热阻及其影响因素。然后,以影响热阻的因素作为设计变量,分析了影响镜筒温度的敏感变量。最后,提出了高温滤光片的热设计方案。真空验证试验表明:在高温和低温两种极端工况下,滤光片温度水平分别稳定在105.8℃和138.2℃,其控温准确度优于±2.5℃,控温稳定度优于0.75℃/min;反射镜组和探测器窗口温度水平和温差都满足热控指标。得到的结果显示,基于热阻和温度灵敏度分析的设计方法,能够快速明确影响热阻的敏感设计变量,减少设计过程的盲目性。空间高温滤光片的热设计满足了光学系统的要求,保证了广角极光成像仪滤光片组件与反射镜之间的温差。     

Capacitance-torsion balance for measuring small stresses and strains

A versatile and inexpensive capacitance-torsion balance has been developed to measure, simultaneously and continuously, small forces and displacements in remotely located samples. It can also be used as a sensitive dilatometer or as a microbalance. The present instrument provides an output voltage change of 1 V for a load change of 3 g and a displacement of 5x10(-5) m. These load and displacement ranges can be independently chosen by adjusting the geometrical configuration of the balance, whereas the sensitivity is independent of the range.     

Wide angle crystal spectrometer for angularly and spectrally resolved X-ray scattering experiments

A novel wide angle spectrometer has been implemented with a highly oriented pyrolytic graphite crystal coupled to an image plate. This spectrometer has allowed us to look at the energy resolved spectrum of scattered x rays from a dense plasma over a wide range of angles (approximately 30 degrees ) in a single shot. Using this spectrometer we were able to observe the temporal evolution of the angular scatter cross section from a laser shocked foil. A spectrometer of this type may also be useful in investigations of x-ray line transfer from laser-plasmas experiments.     

Correlation method for processing speckle patterns of dynamic light scattering by small particles based on spatial averaging of data

A correlation method for processing dynamic light scattering patterns resulting from laser radiation propagation through solutions and suspensions is proposed which is based on spatial averaging of measurement data on the correlation functions of the intensity of light scattered by small particles.     

一种新型三针法角度精密测量仪的原理与结构

介绍的三针法角度法角度精密测量采用比较测量原理,引入了传递系数的概念,对新型三针法角度精密测量仪的工作原理做了比较详细的介绍,讨论了三针法测量角度精密测量仪标定的可行性,建立了新型三针法角度精密测量仪的工作结构,用测量算例验证了三针法测量角度精密测量仪的工作原理,说明了该角度精密测量仪测量过程,分析了新型三针法角度精密测量仪的工艺特点,总结了测量精度的影响因素并提出了设计注意事项。     

宽覆盖、离轴空间相机光学系统的设计

当前空间相机的光学系统的要求是 :在多光谱范围内,系统要有高分辨率、大视场、小体积、质量轻且像面为平像场,TMA(Threemirroranastigmat)可以满足上述要求。为此给出了这方面的设计,所研究的TMA系统三个反射面都是二次曲面,将主镜和第三镜离轴放置,避免中心遮拦的影响,系统的视场可达到 5°× 0.2°,焦距为 6m,像质接近衍射极限。     

A simple and sensitive apparatus for measuring the magnetization of small ferrite samples

This paper describes an apparatus which allows the routine measurement of the magnetization of small ferrite samples using the well-known extraction method. In contrast to the classical extraction method, however, this device makes use of a high-permeability magnetic circuit that serves both to apply the bias field and to collect the sample flux. This design, together with a signal sampling technique, allows an unusually high sensitivity for this type of method (magnetic moment resolution is 5 x 10(-5) microem). The apparatus is described in detail and a brief theory of its function is given. Finally, the device usefulness is illustrated by some measurement results referring to Ga YIG spheres that are used in ferrimagnetic resonators.     

New reactor dedicated to in operando studies of model catalysts by means of surface x-ray diffraction and grazing incidence small angle x-ray scattering

A new experimental setup has been developed to enable in situ studies of catalyst surfaces during chemical reactions by means of surface x-ray diffraction (SXRD) and grazing incidence small angle x-ray scattering. The x-ray reactor chamber was designed for both ultrahigh-vacuum (UHV) and reactive gas environments. A laser beam heating of the sample was implemented; the sample temperature reaches 1100 K in UHV and 600 K in the presence of reactive gases. The reactor equipment allows dynamical observations of the surface with various, perfectly mixed gases at controlled partial pressures. It can run in two modes: as a bath reactor in the pressure range of 1-1000 mbars and as a continuous flow cell for pressure lower than 10(-3) mbar. The reactor is connected to an UHV preparation chamber also equipped with low energy electron diffraction and Auger spectroscopy. This setup is thus perfectly well suited to extend in situ studies to more complex surfaces, such as epitaxial films or supported nanoparticles. It offers the possibility to follow the chemically induced changes of the morphology, the structure, the composition, and growth processes of the model catalyst surface during exposure to reactive gases. As an example the Pd(8)Ni(92)(110) surface structure was followed by SXRD under a few millibars of hydrogen and during butadiene hydrogenation while the reaction was monitored by quadrupole mass spectrometry. This experiment evidenced the great sensitivity of the diffracted intensity to the subtle interaction between the surface atoms and the gas molecules.