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.     

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.     

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.     

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。     

Ultra-high-precision time control system over any long time delay for laser pump and synchrotron x-ray probe experiment

An ultra-high-precision clock system for long time delay has been developed for picosecond time-resolved x-ray diffraction measurements using synchrotron radiation (SR) pulses and synchronized femtosecond laser pulses. The time delay control between pump laser pulse and the probe SR pulse was achieved by combining an in-phase quadrature modulator and a synchronous counter. This method allowed us to change the delay time by a nearly infinite amount while maintaining the precision of +/-8.40 ps. Time-resolved diffraction measurements using the delay control system were demonstrated for precise measurement of an acoustic velocity in a single crystal of gallium arsenide.     

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.     

High sensitivity magnetometer for measuring the isotropic and anisotropic magnetisation of small samples

We describe how the full, isotropic and anisotropic, magnetisation of samples as small as tens of micrometers in size can be sensitively measured using a piezoresistive microcantilever and a small, moveable ferromagnet. Depending on the position of the ferromagnet, a strong but highly local field gradient of up to ～4200 T/m can be applied at the sample or removed completely during a single measurement. In this way, the magnetic force and torque on the sample can be independently determined without moving the sample or cycling the experimental system. The technique can be used from millikelvin temperatures to ～85 K and in magnetic fields from 2 T to the highest fields available. We demonstrate its application in measurements of the semimagnetic semiconductor Hg(1 - x)Fe(x)Se, where we achieved a moment sensitivity of better than 2.5 × 10(-14) J/T for both isotropic and anisotropic components.     

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.     

Real time linear simulation and control for small aircraft turbojet engine

The performance of the aircraft gas turbine engine requires optimization because it is directly related to overall aircraft performance. In this study, a modified DYNGEN, a nolinear dynamic simulation program with component maps of the small aircraft turbojet engine, was used to predict the overall engine performance. Response characteristics of various cases, such as 6%, 5% and 3% rpm step models and the real-time linear model of the interpolation scheme within the operating range were compared. Among them, the real time linear model was selected for the turbojet engine with nonlinear characteristics. Finally control schemes such as PI (Proportional-Integral Controller) and LQR (Linear Quadratic Regulator) were applied to optimize the engine performance. The overshoot of the turbine inlet temperature was effectively eliminated by LQR controller with the proper control gain K.     

Operational mode-shape normalisation with a structural modification for small and light structures

When dealing with small and light structures, difficulties occur when measuring the modal parameters. The resonant frequencies are usually relatively high and therefore a wide frequency range is needed for the measurement. Furthermore, the mass that is added to the structure by the sensors causes structural modifications. To overcome these difficulties, an improved method using an operational modal analysis instead of an experimental modal analysis is proposed in this study. It is derived from the sensitivity-based operational mode-shape normalisation with a consideration of the mode-shape variation. The measurement of the excitation force is not needed, because the operational modal analysis is used and only two simultaneous response measurements at an unknown excitation are required. The proposed method includes the cancellation of the added mass, resulting in mode shapes and resonant frequencies of the unmodified structure. The numerical and experimental results on small and light structures are compared with the results of the experimental modal analysis. The comparison shows that the proposed approach allows measurements over a wide frequency range and increases the accuracy of the results compared to the sensitivity-based operational mode-shape normalisation and also compared to the particular experimental modal analysis method that was used in this study. The advantages of the proposed method can be seen whenever the mass that is added to the structure by the accelerometer is not negligible and therefore a variation of the mode shapes occurs.