Development of x-ray laminography under an x-ray microscopic condition

An x-ray laminography system under an x-ray microscopic condition was developed to obtain a three-dimensional structure of laterally-extended planar objects which were difficult to observe by x-ray tomography. An x-ray laminography technique was introduced to an x-ray transmission microscope with zone plate optics. Three prototype sample holders were evaluated for x-ray imaging laminography. Layered copper grid sheets were imaged as a laminated sample. Diatomite powder on a silicon nitride membrane was measured to confirm the applicability of this method to non-planar micro-specimens placed on the membrane. The three-dimensional information of diatom shells on the membrane was obtained at a spatial resolution of sub-micron. Images of biological cells on the membrane were also obtained by using a Zernike phase contrast technique.     

A clamp-type pressure cell for high energy x-ray diffraction

We present a clamp-type pressure cell for high energy x-ray diffraction. The pressure cell was specifically designed for studies of weak superstructure reflections at low temperatures in transition metal oxides, resulting from, e.g., charge density modulations. Using a photon energy of E=100 keV, the bulk properties of single crystals with a volume of typically 2-5 mm3 can be studied in transmission geometry. To demonstrate the performance of the pressure cell, we present data on the charge stripe order in the high-temperature superconductor La1.875Ba0.125CuO4.     

Plastic contact under high normal pressure

The extent of plastic contact under high loads was studied. On the basis of plasticity theory an analytical expression for the relationship between the real contact area and normal pressure was obtained. The analysis shows that the real pressure rises when the real contact area increases beyond some critical value. The real contact area asymptotically tends to the nominal one when the contact pressure tends to infinity. The limit of classical theory validity has been obtained for different modes of contact deformation. Asperity interaction leads to transformation of the initial bearing curve. The relationship between the real contact area and compliance under high normal pressure was obtained.     

Alternating current impedance spectroscopy measurement under high pressure

A microcircuit was designed and fabricated on a diamond anvil cell for alternating current impedance spectroscopy measurement under high pressure. Sputtered molybdenum film on a diamond anvil was used as an electrode, maintained the contact between the sample and the electrode stable, and reduced the electrode effect on the impedance measurement. By the empty cell and short circuit tests, the parasitic capacitive impedance from the sample chamber wall was observed to be larger than 10(5) Ω at a frequency lower than 1.0 MHz and could be ignored for samples with higher conductivity. The wire inductance was only 1.0 μH and just appeared at frequency higher than 20 kHz, which could be subtracted from measured impedance for the samples with higher impedance than several hundred ohms. Using this apparatus, the impedances of the II-VI group cadmium sulfide were measured. The pressure dependence of the grain interior conductance of CdS crystal was obtained, which reflected that the phase transitions of CdS under high pressure are the same as the single crystal measurement results.     

Hard x-ray phase contrast imaging using single absorption grating and hybrid semiconductor pixel detector

A method for x-ray phase contrast imaging is introduced in which only one absorption grating and a microfocus x-ray source in a tabletop setup are used. The method is based on precise subpixel position determination of the x-ray pattern projected by the grating directly from the pattern image. For retrieval of the phase gradient and absorption image (both images obtained from one exposure), it is necessary to measure only one projection of the investigated object. Thus, our method is greatly simplified compared with the phase-stepping method and our method can significantly reduce the time-consuming scanning and possibly the unnecessary dose. Furthermore, the technique works with a fully polychromatic spectrum and gives ample variability in object magnification. Consequently, the approach can open the way to further widespread application of phase contrast imaging, e.g., into clinical practice. The experimental results on a simple testing object as well as on complex biological samples are presented.     

一种高温超高压条件下的三腔压力分隔装置设计

针对高温超高压条件下三腔压力在一个容器内难建立、难传递等问题,设计了一套三腔压力分隔装置。该装置结构简单实用,不仅能稳定建立三腔压力、模拟地层结构环境,且可实现围压和孔隙压力间的有效传递。     

Optimizing the operation of a high resolution vertical Johann spectrometer using a high energy fluorescer x-ray source

This paper describes the operation and testing for a vertical Johann spectrometer (VJS) operating in the 13 keV range. The spectrometer is designed to use thin curved mica crystals or thick germanium crystals. The VJS must have a resolution of E/ΔE=3000 or better to measure the Doppler broadening of highly ionized krypton and operate at a small x-ray angle in order to be used as a diagnostic in a laser plasma target chamber. The VJS was aligned, tested, and optimized using a fluorescer type high energy x-ray (HEX) source located at National Security Technologies (NSTec), LLC, in Livermore, CA. The HEX uses a 160 kV x-ray tube to excite fluorescence from various targets. Both rubidium and bismuth fluorescers were used for this effort. This presentation describes the NSTec HEX system and the methods used to optimize and characterize the VJS performance.     

一种高压大流量自动稳压系统的设计

１　概述在某型导弹的地面试验中,要为其提供一路高压大流量冷气,其要求是：（１）出口压力快速稳定;（２）在一定压力范围内可以自由设定输出压力。在以往的试验中,输出端冷气的稳压完全靠人工机械完成,不仅增加了试验时间、浪费了人力,而且稳压精度差,影响了试验结果。随着试验对象的精密设计,这种操纵方式越来越不适应要求,我们自行设计的反馈式自动稳压系统体积小,结构紧凑,能够自动、迅速地稳压,该系统同样可用于有类似要求的气动试验。２　系统的特点该系统的特点如下：（１）输出端压力可调,当输入压力为２０ＭＰａ时,…     

Characterizing high energy spectra of NIF ignition Hohlraums using a differentially filtered high energy multipinhole x-ray imager

Understanding hot electron distributions generated inside Hohlraums is important to the national ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with target materials. We used an array of 18 pinholes with four independent filter combinations to image entire Hohlraums with a magnification of 0.87× during the Hohlraum energetics campaign on NIF. Comparing our results with Hohlraum simulations indicates that the characteristic 10-40 keV hot electrons are mainly generated from backscattered laser-plasma interactions rather than from Hohlraum hydrodynamics.     

Structural analysis of simple base oils under high pressure using synchrotron radiation X-ray diffraction: First trial

The microscopic structures of two base oils at atmospheric pressure and under high pressure were analyzed using synchrotron radiation X-ray diffraction in this work. The experimental apparatuses we used were designed for structural analysis under high pressure: the ‘MAX80’ X-ray diffractometer with a cubic multi-anvil press at the KEK synchrotron facilities and the ‘SMAP2’ one at the SPring-8 synchrotron facilities. The sample oils were n-hexadecane CH₃(CH₂)₁₄CH₃ and dicyclohexyl C₆H₁₁C₆H₁₁; the former is a chain hydrocarbon, and the latter is a dual-cyclic hydrocarbon. The samples were sealed in a capsule made of Teflon and put under pressure with one of the two apparatuses. Application of synchrotron radiation X-rays to the sample oils at atmospheric pressure produced clear pair distribution functions and under several high-pressure conditions it produced scattering intensity profiles. The results revealed that the oils transitioned from liquid phase to single-crystal phase with increasing pressure. With a constant high pressure, they crystallized over time, making the transition in about an hour.     

Experiments on foam texture under high pressure in porous media

Foam flooding has become one of the most effective methods to improve oil recovery in high water-cut oilfields. In order to obtain images of the texture of foam in the cores under high pressure, this paper developed an experimental real-time image acquisition device for detecting the foam's texture as the bubbles flowed in the porous media. Image processing and statistic analysis methods for describing the foam's texture were also established. Experimental results showed that the bubble distribution became homogeneous and stabilized, and the pressure difference between two ends of the core increased gradually during the process of foam flooding. In the initial stage, the bubbles presented a flake-like distribution. The liquid phase flowed continuously, as did the gas phase. As the displacement continued, the volume of a single bubble lessened, while the number of bubbles increased. When the bubbles reached a steady state, the pressure difference between the two ends of the core was stable, and the bubbles presented a uniform distribution. A larger injection rate, a higher core permeability and a larger gas–liquid ratio all can cause a larger-than-average bubble diameter, poor stability and a decreased degree of homogeneity.     

Dry friction of steel under high pressure in quasi-static conditions

Measurements were carried out for static and kinetic friction coefficients for steel as a function of the normal pressure for two surface roughness conditions of the matrix: ground and sand blasted. The samples were interstitial free steels, the tests were done at room temperature, in quasi-static and dry contact conditions. Very high pressures were applied in the range of 230–1100 MPa in order to simulate the conditions of testing in severe plastic deformation processes of metals. A new device was designed for this purpose. The results showed a decrease of the friction coefficients with the applied normal stress with stronger dependence for sand blasted surfaces.     

高温高压双金属片式疏水阀的设计

介绍了高温高压双金属片式疏水阀的工作原理以及特殊结构的设计,论述了双金属片材料和组合结构的选择,优化了阀门在恶劣工况下阻汽排水性能。     

A miniature cubic anvil apparatus for optical measurement under high pressure

A miniature cubic anvil apparatus was developed for optical measurement on materials in a high-pressure space of 8-10 mm(3) under high pressure, and preliminary experiments were conducted to 3.6 GPa at room temperature with optical visual observation and ruby fluorescence measurement. In the apparatus, a cubic pressure medium was squeezed with six tungsten carbide anvils, which are driven with a pair of guide blocks by tightening four loading screws. Optical access on the sample was made through holes in axial anvils and the guide blocks as well as optical windows made of Al(2)O(3) single crystals embedded in the pressure medium. The apparatus is compact and light, ~53 mm in diameter and height and ~530 g in weight, and the features of the apparatus benefit easy application of the apparatus to various types of standard optical measurement systems. The optical measurement on the sample in the high-pressure space of 8-10 mm(3) should greatly contribute to advancements of studies relevant to high-pressure behaviors of materials.     

Investigation of SrS under high pressure including the role of temperature

In this paper we focus on the structural and elastic properties of the B1 phase of SrS by using the modified TBP model, including the role of temperature. We have successfully obtained the phase transition pressures and volume changes at different temperatures. In addition elastic constants and anisotropy factor (A) of B1 phase of SrS at different temperatures are discussed. Our results are comparable with the previous ones at high temperatures and pressures. The elastic properties of the B1 phase of SrS have been discussed with various temperature and pressure. More over the thermal properties like Debye temperature, Thermal expansion coefficient (α) and Gruneisen parameter (γ) and anisotropy factor at high temperatures have also been discussed successfully.     

Measuring phase distribution in high pressure three-phase flow using gamma densitometry

A large campaign of multiphase experiments using formation water, a North Sea crude oil and a blend of gas produced from different North Sea gas fields was performed in the Porsgrunn Multiphase Flow Loop. The tests were performed under realistic field conditions (p=100 bar and ). Different multiphase flow patterns such as waves and slugs were observed in the experiments. At high pressure conditions it is often difficult to distinguish between these types of flows due to considerable dispersions between the fluid phases.A traversable dual-energy gamma instrument was used to measure phase fractions at different positions at 7 Hz. Careful data analysis was needed to obtain the relevant data from the noisy measurements. Data analysis techniques for three-phase flow were developed and tested against calibration data from single-phase and two-phase flow.In addition it was shown that the averaged density data from the traversable gamma instrument compared favourably to density measurements by a calibrated stationary single-energy gamma instrument.However the traversable densitometer gave much more additional information compared with the single-energy instrument since the transient phase fraction for all three phases could be measured at different positions over the cross section of the pipeline. This information allowed the definite determination of the flow pattern.     

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.     

超高压超临界撞击流实验平台

提出超高压超临界撞击流概念,应用其开发设计超高压超临界撞击流工作平台,应用缓冲罐,及连续工作原理设计了超高压连续进料装置,解决了超高压状态下的连续进料问题,分析了其结构和工作原理,将其应用于超细粉碎,乳化和萃取过程,显示其独特的优越性,在灵芝孢子的破壁实验中效果令人满意.     

A CFD study of wet gas metering over-reading model under high pressure

The venturi flow meter is increasingly being preferred in multiphase flow measurement because of its shorter upstream and downstream straight sections, less influenced by the flow pattern and relatively small pressure loss. However, when the venturi is used for wet gas measurement, the over-reading phenomenon occurs due to the presence of a small amount of liquid. Many scholars have established over-reading models to correct the measured values of wet gas. Regrettably, the applicability of these over-reading models under actual high pressure operating conditions has not been verified. Therefore, this review focuses on numerical simulation of the flow of wet gas in the venturi tube under high pressure conditions (11MPa/13MPa/15 MPa). The discrete phase model (DPM) and the standard k-ε model was employed in this review. The simulations results reveals the flow characteristics of wet gas in venturi tube, which includes the flow field distributions, droplet concentration distributions and wall pressure profile distributions, and indicates that the over-reading values increases with the increase of Lockhart-Martinelli parameters and gas volume flow rate, but decreases with the increase of pressure. Moreover, the ISO model has the best performance under high pressure conditions.     

In situ Hall effect measurement on diamond anvil cell under high pressure

A method for in situ Hall effect measurement under high pressure was developed on a diamond anvil cell. The electrode was accurately integrated on one diamond anvil with regular shape. A uniform and strong magnetic field was introduced into the sample zone. The voltage errors brought by some negative effects during the measurement were well eliminated. The correction factor of the Hall coefficient, brought by the nonpoint contact between the electrode and the sample, was 4.51%. The measurement error of the magnetic field did not exceed 1%. The carrier character of ZnTe powders was studied up to 23 GPa. The evolution of conductivity with pressure was explained based on the variation of the carrier behavior.