Development of new apertures for coherent X‐ray experiments

When one performs a coherent small‐angle X‐ray scattering experiment, the incident beam must be spatially filtered by slits on a length scale smaller than the transverse coherence length of the source which is typically around 10 µm. The Fraunhofer diffraction pattern of the slit is one of the important sources of background in these experiments. New slits which minimize this parasitic background have been designed and tested. The slit configuration apodizes the beam by the use of partially transmitting inclined slit jaws. A model is presented which predicts that the high wavevector tails of the diffraction pattern fall as the inverse fourth power of the wavevector instead of the inverse second power that is observed for standard slits. Using cleaved GaAs single‐crystal edges, Fraunhofer diffraction patterns from 3 and 5.5 keV X‐rays were measured, in agreement with the theoretical model proposed. A novel phase‐peak diffraction pattern associated with phase variations of the transmitted electric field was also observed. The model proposed adequately accounts for this phenomenon.     

DEFORMATION OF SOFT COLLOIDAL CRYSTALLINE STRUCTURE-THEORETICAL CONSIDERATIONS AND EXPERIMENTAL EVIDENCES BY SYNCHROTRON SMALL-ANGLE X-RAY SCATTERING ON TENSILE STRETCHED POLYMERIC LATEX FILM

Films obtained via drying a polymeric latex dispersion are normally colloidal crystalline where latex particles are packed into a face centered cubic (fcc) structure.Different from conventional atomic crystallites or hard sphere colloidal crystallites,the crystalline structure of these films is normally deformable due to the low glass transition temperature of the latex particles.Upon tensile deformation,depending on the drawing direction with respect to the normal of specific crystallographic plane,one ...     

Scattering from polymer-like micelles

Polymer-like micelles are analogs to polymer solutions and provide an exciting class of materials for both applications and fundamental understanding of polyelectrolyte systems. Small angle neutron and X-ray scattering have been key to the characterization of these materials from the first observations of linear micelle growth. As new materials are developed, these techniques continue to be utilized and combined with other analytical tools to characterize the length and time scales of polymer-like micelle behavior. Recent reports on the use of small-angle scattering to characterize polymer-like and wormlike micelles are reviewed, with focus on new materials, improvements in analytical approaches and anisotropic structures.     

Small‐angle scattering of polychromatic X‐rays: effects of bandwidth,spectral shape and high harmonics

Polychromatic X‐ray sources can be useful for photon‐starved small‐angle X‐ray scattering given their high spectral fluxes. Their bandwidths, however, are 10–100 times larger than those using monochromators. To explore the feasibility, ideal scattering curves of homogeneous spherical particles for polychromatic X‐rays are calculated and analyzed using the Guinier approach, maximum entropy and regularization methods. Monodisperse and polydisperse systems are explored. The influence of bandwidth and asymmetric spectra shape are explored via Gaussian and half‐Gaussian spectra. Synchrotron undulator spectra represented by two undulator sources of the Advanced Photon Source are examined as an example, as regards the influence of asymmetric harmonic shape, fundamental harmonic bandwidth and high harmonics. The effects of bandwidth, spectral shape and high harmonics on particle size determination are evaluated quantitatively.     

Characterization of an in‐vacuum PILATUS 1M detector

A dedicated in‐vacuum X‐ray detector based on the hybrid pixel PILATUS 1M detector has been installed at the four‐crystal monochromator beamline of the PTB at the electron storage ring BESSY II in Berlin, Germany. Owing to its windowless operation, the detector can be used in the entire photon energy range of the beamline from 10 keV down to 1.75 keV for small‐angle X‐ray scattering (SAXS) experiments and anomalous SAXS at absorption edges of light elements. The radiometric and geometric properties of the detector such as quantum efficiency, pixel pitch and module alignment have been determined with low uncertainties. The first grazing‐incidence SAXS results demonstrate the superior resolution in momentum transfer achievable at low photon energies.     

Thorough small‐angle X‐ray scattering analysis of the instability of liquid micro‐jets in air

Liquid jets are of interest, both for their industrial relevance and for scientific applications (more important, in particular for X‐rays, after the advent of free‐electron lasers that require liquid jets as sample carrier). Instability mechanisms have been described theoretically and by numerical simulation, but confirmed by few experimental techniques. In fact, these are mainly based on cameras, which is limited by the imaging resolution, and on light scattering, which is hindered by absorption, reflection, Mie scattering and multiple scattering due to complex air/liquid interfaces during jet break‐up. In this communication it is demonstrated that synchrotron small‐angle X‐ray scattering (SAXS) can give quantitative information on liquid jet dynamics at the nanoscale, by detecting time‐dependent morphology and break‐up length. Jets ejected from circular tubes of different diameters (100–450 µm) and speeds (0.7–21 m s^?1) have been explored to cover the Rayleigh and first wind‐induced regimes. Various solvents (water, ethanol, 2‐propanol) and their mixtures have been examined. The determination of the liquid jet behaviour becomes essential, as it provides background data in subsequent studies of chemical and biological reactions using SAXS or X‐ray diffraction based on synchrotron radiation and free‐electron lasers.     

热损伤奥克托金(HMX) 缺陷的X射线小角散射研究

奥克托金(HMX) 在温度作用下, 会发生热膨胀、 相转变、 热分解等物理、 化学变化, 导致在材料内部产生大量缺陷, 进而会对其宏观性能造成明显影响. 为了深入了解热损伤HMX内部的缺陷演化, 本文采用X射线小角散射和原子力显微技术研究了热损伤HMX的内部缺陷. 结果发现HMX在180 °C相变过程中散射曲线有明显的变化, 颗粒内部生成了大量10nm左右的孔洞, 随着加载时间延长, 其尺寸增大到25nm, 数量明显降低. 当HMX在190 °C、 200 °C保温5h时, 由于HMX热分解内部有新缺陷生成, 小角散射发现其尺寸约为5至8nm, 随着加载温度升高, 其数量增加.     

Light scattering of liposomal structure of 1,2-distearoyl-sn-glycero-3-phosphocholine and cholesterol with NaCl

1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol are used to prepare liposome. Dynamic light scattering was used to study the dynamics of different concentration of the DSPC on liposomal structure. The results show that with increase of DSPC concentration the diffusion coefficient decreases. The small angle X-Ray scattering (SAXS) experiments show that an increase of the DSPC of 0.5–5% changes the size of liposomal structure from 35 to 112 nm, this is analysed in leaves of hard sphere core shell model. Moreover, the addition of NaCl at 0.001 molar can decrease the size of liposomal structure.     

An In Situ Small-Angle X-Ray Scattering Study of Propylene-Butene and Propylene-Ethylene Random Copolymers during Heating Process

Summary: The micro-structure evolution of isotactic polypropylene-1-butene (iPPBu) and polypropylene-ethylene (iPPEt) random copolymers with 4 mol% of 1-butene and ethylene was respectively investigated by differential scanning calorimetry (DSC) and in-situ small angle X-ray scattering (SAXS) techniques during heating process. The signal of melting enthalpy of iPPBu disappears a little earlier than that of iPPEt, which keeps consistent with the decay trend of scattering intensity during the late period of melting process. However, the SAXS data further show that the crystal thickness of iPPBu is a little larger than that of iPPEt during heating process. It is suggested that the melting behaviors of such copolymers depend on not only the lamellar thickness but also the crystal stability.