A new small‐angle X‐ray scattering set‐up on the crystallography beamline I711 at MAX‐lab

A small‐angle X‐ray scattering (SAXS) set‐up has recently been developed at beamline I711 at the MAX II storage ring in Lund (Sweden). An overview of the required modifications is presented here together with a number of application examples. The accessible q range in a SAXS experiment is 0.009–0.3 Å^?1 for the standard set‐up but depends on the sample‐to‐detector distance, detector offset, beamstop size and wavelength. The SAXS camera has been designed to have a low background and has three collinear slit sets for collimating the incident beam. The standard beam size is about 0.37 mm × 0.37 mm (full width at half‐maximum) at the sample position, with a flux of 4 × 10¹⁰ photons s^?1 and λ = 1.1 Å. The vacuum is of the order of 0.05 mbar in the unbroken beam path from the first slits until the exit window in front of the detector. A large sample chamber with a number of lead‐throughs allows different sample environments to be mounted. This station is used for measurements on weakly scattering proteins in solutions and also for colloids, polymers and other nanoscale structures. A special application supported by the beamline is the effort to establish a micro‐fluidic sample environment for structural analysis of samples that are only available in limited quantities. Overall, this work demonstrates how a cost‐effective SAXS station can be constructed on a multipurpose beamline.     

The application of hybrid pixel detectors for in‐house SAXS instrumentation with a view to combined chromatographic operation

This study analyses the potential for laboratory‐based size‐exclusion chromatography (SEC) integrated small‐angle X‐ray scattering (SAXS) instrumentation to characterize protein complexes. Using a high‐brilliance home source in conjunction with a hybrid pixel X‐ray detector, the efficacy of SAXS data collection at pertinent protein concentrations and exposure times has been assessed. Scattering data from SOD1 and from the complex of SOD1 with its copper chaperone, using 10 min exposures, provided data quality in the range 0.03 < q < 0.25 Å^?1 that was sufficient to accurately assign radius of gyration, maximum dimension and molecular mass. These data demonstrate that a home source with integrated SEC–SAXS technology is feasible and would enable structural biologists studying systems containing transient protein complexes, or proteins prone to aggregation, to make advanced preparations in‐house for more effective use of limited synchrotron beam time.     

Small Angle X-Ray Scattering of Hematite Aggregates

Small angle X-ray scattering has been utilised to study the structure of hematite aggregates. The small angle X-ray scattering (SAXS) spectra obtained provided insight into structure of the hematite aggregates and the size of the primary particles. The structural analysis results obtained by SAXS are consistent with previous results obtained from static light scattering studies. Both techniques indicate that the mass fractal dimensions of hematite aggregates are markedly higher than those obtained for other particle systems.     

Investigation of surface topology of printed nanoparticle layers using wide‐angle low‐Q scattering

A new small‐angle scattering technique in reflection geometry is described which enables a topological study of rough surfaces. This is achieved by using long‐wavelength soft X‐rays which are scattered at wide angles but in the low‐Q range normally associated with small‐angle scattering. The use of nanometre‐wavelength radiation restricts the penetration to a thin surface layer which follows the topology of the surface, while moving the scattered beam to wider angles preventing shadowing by the surface features. The technique is, however, only applicable to rough surfaces for which there is no specular reflection, so that only the scattered beam was detected by the detector. As an example, a study of the surfaces of rough layers of silicon produced by the deposition of nanoparticles by blade‐coating is presented. The surfaces of the blade‐coated layers have rough features of the order of several micrometers. Using 2 nm and 13 nm X‐rays scattered at angular ranges of 5°≤θ≤ 51° and 5°≤θ≤ 45°, respectively, a combined range of scattering vector of 0.00842 Å^?1≤Q≤ 0.4883 Å^?1 was obtained. Comparison with previous transmission SAXS and USAXS studies of the same materials indicates that the new method does probe the surface topology rather than the internal microstructure.     

Diagnostic imaging by energetic radioactive particle beams: applications in Bragg Peak cancer therapy

Researchers explore the use of Bragg Ionization Peak in radiotherapy for tumors. Considerations for the production of a high quality radioactive beam include secondary beam production efficiency, primary beam survival, and multiple scattering. A Positron Emitting Beam Analyzing camera was developed and tested at BEVALAC using a neon-19 beam stopping point. Results indicate that in homogeneous brain tissues, CT measurements and radioactive beam measurements are between 1-2 mm; there can be substantial difference between CT measurements and radioactive beam estimates if the beam stopping point crosses the fossae; random coincidences due to detector activation also appear as diffused images in the image plane of the beam stopping point; and further enhancements are necessary to make reliable measurements in the human trunk and complex brain regions.     

In situ SAXS study on size changes of platinum nanoparticles with temperature

Poly(vinylpyrrolidone) (PVP)-coated platinum (Pt) nanoparticles were prepared in methanol-water reduction method. In situ small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD) techniques were used to probe the size change of particles and crystallites with temperature. Tangent-by-tangent (TBT) method of SAXS data analysis was improved and used to get the particle size distribution (PSD) from SAXS intensity. Scherrer’s equation was used to derive the crystallite size from XRD pattern. Combining SAXS and XRD results, a step-like characteristic of the Pt nanoparticle growth has been found. Three stages (diffusion, aggregation, and agglomeration) can be used to describe the growth of the Pt nanoparticles and nanocrystallites. Aggregation was found to be the main growth mode of the Pt nanoparticles during heating. The maximum growth rates of Pt nanoparticles and Pt nanocrystallites, as well as the maximum aggregation degree of Pt nanocrystallites were found, respectively, at 250 °C, 350 °C and 300 °C. These results are helpful to understanding the growth mode of nanoparticles, as well as controlling the nanoparticle size.     

Performance of the micro‐PIC gaseous area detector in small‐angle X‐ray scattering experiments

The application of a two‐dimensional photon‐counting detector based on a micro‐pixel gas chamber (µ‐PIC) to high‐resolution small‐angle X‐ray scattering (SAXS), and its performance, are reported. The µ‐PIC is a micro‐pattern gaseous detector fabricated by printed circuit board technology. This article describes the performance of the µ‐PIC in SAXS experiments at SPring‐8. A dynamic range of >10⁵ was obtained for X‐ray scattering from a polystyrene sphere solution. A maximum counting rate of up to 5 MHz was observed with good linearity and without saturation. For a diffraction pattern of collagen, weak peaks were observed in the high‐angle region in one accumulation of photons.     

Time‐ and spatial‐resolved XAFS spectroscopy in a single shot: new analytical possibilities for in situ material characterization

A new concept that comprises both time‐ and lateral‐resolved X‐ray absorption fine‐structure information simultaneously in a single shot is presented. This uncomplicated set‐up was tested at the BAMline at BESSY‐II (Berlin, Germany). The primary broadband beam was generated by a double multilayer monochromator. The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by either an energy‐sensitive area detector, the so‐called color X‐ray camera, or by an area‐sensitive detector based on a CCD camera, in θ–2θ geometry. The first tests were performed with thin metal foils and some iron oxide mixtures. A time resolution of lower than 1 s together with a spatial resolution in one dimension of at least 50 µm is achieved.     

Nanoscale Structure of Urethane/Urea Elastomeric Films

The nanostructure of urethane/urea elastomeric membranes was investigated by small-angle X-ray scattering (SAXS) in order to establish relationships between their structure and mechanical properties. The networks were made up of polypropylene oxide (PPO) and polybutadiene (PB) segments. The structural differences were investigated in two types of membranes with the same composition but with different thermal treatment after casting. Type I was cured at 70–80 °C and type II at 20 °C. Both membranes showed similar phase separation by TEM, with nanodomains rich in PB or PPO and 25 nm dimensions. The main difference between type I and type II membranes was found by SAXS. The type I membrane spectra showed, besides a broad band at a 27-nm q value (modulus of the scattering vector), an extra band at 6 nm, which was not observed in the type II membrane. The SAXS spectra were interpreted in terms of PPO, PB soft segments, and urethane/urea links, as well as hard moiety segregation in the reaction medium. This additional segregation (q = 7 nm), although subtle, results in diverse mechanical behavior of in both membranes.     

A dedicated small‐angle X‐ray scattering beamline with a superconducting wiggler source at the NSRRC

At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5 GeV storage ring, a dedicated small‐angle X‐ray scattering (SAXS) beamline has been installed with an in‐achromat superconducting wiggler insertion device of peak magnetic field 3.1 T. The vertical beam divergence from the X‐ray source is reduced significantly by a collimating mirror. Subsequently the beam is selectively monochromated by a double Si(111) crystal monochromator with high energy resolution (ΔE/E? 2 × 10^?4) in the energy range 5–23 keV, or by a double Mo/B₄C multilayer monochromator for 10–30 times higher flux (～10¹¹ photons s^?1) in the 6–15 keV range. These two monochromators are incorporated into one rotating cradle for fast exchange. The monochromated beam is focused by a toroidal mirror with 1:1 focusing for a small beam divergence and a beam size of ～0.9 mm × 0.3 mm (horizontal × vertical) at the focus point located 26.5 m from the radiation source. A plane mirror installed after the toroidal mirror is selectively used to deflect the beam downwards for grazing‐incidence SAXS (GISAXS) from liquid surfaces. Two online beam‐position monitors separated by 8 m provide an efficient feedback control for an overall beam‐position stability in the 10 µm range. The beam features measured, including the flux density, energy resolution, size and divergence, are consistent with those calculated using the ray‐tracing program SHADOW. With the deflectable beam of relatively high energy resolution and high flux, the new beamline meets the requirements for a wide range of SAXS applications, including anomalous SAXS for multiphase nanoparticles (e.g. semiconductor core‐shell quantum dots) and GISAXS from liquid surfaces.     

Biomolecular solution X-ray scattering at the National Synchrotron Light Source

In recent years there has been a growing interest in the application of X-ray scattering techniques to biomolecules in solution. At NSLS, a new undulator-based beamline, X9, has been constructed to address the oversubscribed user demand for X-ray scattering. Beamline X9 has the capability to perform small/wide-angle X-ray scattering (SAXS/WAXS) all in one single instrument. This is accomplished by utilizing a vacuum sample/detector chamber that is an integral part of the SAXS scattering flight path. This vacuum chamber allows a WAXS detector to be positioned at a close distance from the sample, while not interfering with scattered X-rays at small angles from reaching the SAXS detector. A regular training program, the X9 workbench, has also been established to allow users to become familiar with beamline X9 for solution X-ray scattering.     

Beamline setup for in situ measurements of particles in turbulent spray flames using small angle X-ray scattering

The particle formation in spray flame synthesis (SFS) is a fast and complex process involving many sub-steps that may happen simultaneously. To investigate the mechanisms that typically lead to small aggregated primary particles, a sophisticated technique for in situ measurements in the flame is necessary to provide information about primary particles and the aggregates as well. This work describes the development of an in situ measurement setup using small angle X-ray scattering (SAXS) to investigate the entire particle formation mechanism of zirconia nanoparticles in and above a turbulent spray flame. In preparation for the in situ measurements, a beamline for single crystal diffractometry at Karlsruhe Research Accelerator (KARA) was adapted for low scattering SAXS experiments including optimizations of the optics and measurement protocol. As a result, a significant dependence of scattering intensity was detected as a function of the height above the burner. A detailed analysis of the SAXS data and comparison with TEM images allow insights into the primary particle growth, the development of fractal properties and the aggregation process.     

Sensitive and accurate dual-wavelength UV-VIS polarization detector for optical remote sensing of tropospheric aerosols

An UV-VIS polarization lidar has been designed and specified for monitoring aerosols in the troposphere, showing the ability to precisely address low particle depolarization ratios, in the range of a few percent. Non-spherical particle backscattering coefficients as low as 5×10^?8 m^?1?sr^?1 have been measured and the particle depolarization ratio detection limit is 0.6 %. This achievement is based on a well-designed detector with laser-specified optical components (polarizers, dichroic beamsplitters) summarized in a synthetic detector transfer matrix. Hence, systematic biases are drastically minimized. The detector matrix being diagonal, robust polarization calibration has been achieved under real atmospheric conditions. This UV-VIS polarization detector measures particle depolarization ratios over two orders of magnitude, from 0.6 up to 40 %, which is new, especially in the UV where molecular scattering is strong. Hence, a calibrated UV-VIS polarization-resolved time-altitude map is proposed for urban and free tropospheric aerosols up to altitude of 4 kilometers, which is also new. These sensitive and accurate UV-VIS polarization-resolved measurements enhance the spatial and time evolution of non-spherical tropospheric particles, even in urban polluted areas. This study shows the capability of polarization-resolved laser UV-VIS spectroscopy to specifically address the light backscattering by spherical and non-spherical tropospheric aerosols.     

同步辐射SAXS技术在TATB含能材料微孔结构研究中的初步应用

TATB含能材料的微结构对该材料的感度等有明显的影响,因而对于材料的安全性有着特别重要的意义.小角X射线散射(SAXS)技术是一种分析物质微观结构的重要手段,应用SAXS分析技术可以获取材料中几纳米到几百纳米尺度范围的亚微结构信息.利用同步辐射作为X射线源对TATB钝感炸药进行了小角散射实验测量,获得了SAXS测量谱.对实验谱数据进行处理,可得到样品材料的颗粒分布及内部微孔大小等微结构参数.     

Streuung von Helium-Atomstrahlen in Edelgasen

The scattering of Helium atomic beams in rare gases is investigated by measurements of total elastic scattering cross sections. With the device described the dependence of total scattering cross sections of the relative velocity of the scattering atoms was measured. For variation of the beam velocity in the range of 1:8 a He beam source was used which could be cooled down with liquid helium from room temperature to 4.8 °K. The detector is of the universal-detector-type. A Wien filter is used as mass filter. The lowest detectable particle density is 6.3 · 10³ He-atoms/cm³. The measured scattering cross sections are in qualitative agreement with the theory ofBernstein.     

Laser-based volumetric colour-coded three-dimensional particle velocimetry

We present a method of three-dimensional particle velocimetry with a single digital colour camera using multiple colour illumination to encode image depth over a large volume. A copper vapour laser operating at 511 nm is used to pump an optical fibre producing a multiple-wavelength beam via multiple order stimulated Raman scattering. The beam is dispersed and formed into a stack of thin sheets to illuminate a volume of space. The spatial co-ordinates of particles imaged within the illuminated volume are obtained from their imaged x,y positions with depth discerned from particle hue (set by the wavelength of illumination). The method exhibits an RMS depth error of 3% in relation to the thickness of the illuminated region. This paper reports a proof-of-principle of three-dimensional particle imaging using a multi-wavelength laser source with a view to 3D-3C particle velocimetry.     

光复散射对消光法粒径测量的影响:复散射模型与数值模拟

复散射效应在光散射颗粒测量中不仅重要．且尚未得到很好解决。采用蒙特卡罗方法,对不同的光波长,颗粒浓度以及收接器条件下的光复散射进行了数值模拟．数值算法程序经与四通量模型进行对比验证,数值结果与单散射条件的郎伯-比尔模型进行比较．进而讨论了复散射效应对消光法颗粒粒径测量影响。表明复散射对消光法颗粒测量的影响不仅取决于颗粒系自身的浓度．而且接收器的几何尺寸和接收位置起着非常重要的作用,减小颗粒介质层厚度和减小光接收器接收面积．增大接收距离以及减小接收角都能减小复散射效应对消光法粒径测量的影响。     

Characterization of nanosized partly crystalline photocatalysts

A thorough analysis of nanosized partly crystalline photocatalysts has been carried out. X-ray diffraction (XRD), Small angle X-ray Scattering (SAXS), Scanning electron microscope (SEM), and BET measurements have been applied to study the particle properties of different photocatalysts. The study permitted the determination of absolute crystallinity of partly and fully crystalline photocatalysts by XRD. The absolute crystallinity was determined with CaF₂ as a reference. SAXS measurements were used to study the morphology and to determine the primary particle size of the investigated photocatalysts. The study showed that the commercially available photocatalyst Hombikat UV100 consisted of a great fraction of amorphous material whereas Degussa P25 was found to be almost crystalline. A homemade sample was found to be 63% crystalline anatase and 37% amorphous. The study also revealed that there was a deviation between the primary particle size and the crystal size for the partly crystalline samples caused by the amorphous fraction; however, the fully crystalline Degussa P25 had agreement between the primary particle size and the crystal size.     

Density Fluctuations as Precursors of Crystallization in Polyamide 6,6 Using Time-Resolved X-Ray Scattering Techniques

In the present study, attempts are made to throw light on the mechanisms leading to primary nucleation in polymer crystallization. Previous studies in this field are not conclusive. Aiming to investigate the induction period prior to crystallization, time-resolved simultaneous small- and wide-angle X-ray scattering (SAXS and WAXS) measurements have been made in situ for polyamide 6,6, while it was crystallized from the melt. For this polymer, it is confirmed that at a low supercooling (ΔT≈28°C), during the induction period, a well-resolved SAXS pattern appears. The time evolution of this scattering pattern can be described by the kinetics of spinodal decomposition, as previously reported for the glass crystallization of PEKK and TPI. According to this analysis, a value for the most probable scattering vector q of density fluctuations at around 0.43 nm^?1 is found. It corresponds to a characteristic wavelength of 14.7 nm of long-range density fluctuations growing with time.     

One‐dimensional small‐angle X‐ray scattering tomography of dip‐coated polyamide 6 monofilaments

A synchrotron study is presented in which the concept of one‐dimensional tomographic reconstruction of small‐angle X‐ray scattering patterns is applied to investigate polyamide 6 monofilaments, dip‐coated with alumina particles. The filaments are scanned with a focused synchrotron beam and the resulting scattering patterns are recorded with a PILATUS 2M detector. The reconstructed sequence of SAXS images reflects the local nanostructure variation along the filament radius. In particular, the influence of coating process parameters on the polyamide 6 is investigated.