X-ray ptychography is an ultrahigh-resolution scanning coherent diffractive imaging technique, allowing quantitative measurements of extended samples and a simultaneous reconstruction of the illuminating wavefront. Recent development of the mixed-state reconstruction algorithm has triggered a certain interest in utilizing partially coherent X-ray sources for ptychography. Here, we study how finite spatial coherence influences the reconstructed image of a test structure. Our work shows that use of a highly coherent illumination provides images with better spatial resolution and fewer artefacts than the approach with partial coherence.
The bio-imaging and diffraction beamline P11 at PETRA III is dedicated to structure determination of periodic (crystalline) and aperiodic biological samples. The beamline features two experimental endstations: an X-ray microscope and a crystallography experiment. Basis of design was to provide an extremely stable and flexible setup ideally suited for micro and nano beam applications. The X-ray optics consist of a HHL double crystal monochromator, followed by two horizontal deflecting and one vertical deflecting X-ray mirrors. All mirrors are dynamically bendable and used to generate an intermediate focus at 65.5 m from the source with a size of 37 × 221 µm2FWHM (v × h). All experiments are installed on an 8 m long granite support which provides a very stable setup for micro beam experiments. The crystallography endstation is located at the end of the granite at 72.9 m from the source. The experiment is equipped with a high precision single axis goniostat with a combined sphere of confusion of less than 100 nm. X-ray energies are tunable between 5.5 and 30 keV. A second focusing bendable KB mirror system can be used for further demagnification of the secondary source. In this way the beam size can be freely adjusted between 4 × 9 µm2and 300 × 300 µm2FWHM (v × h) with 1013ph/s at 12 keV. Smaller beam sizes down to 1 × 1 µm2with more than 2 × 1011ph/s in the focus can be realized by slitting down the secondary source at the cost of flux. The crystallography endstation is equipped with a Pilatus 6M-F detector which allows fast data collection with up to 25 Hz. Due to the very small beam divergence of the X-ray beam P11 is ideally suited to measure large unit cell systems, such as viruses or large molecular complexes. In addition, the beamline is capable of high-throughput crystallography and fast crystal screening. Crystals can be mounted in less than 10 s using an automatic sample changer. The large sample dewar provides space for 368 crystals.
BioStruct aims to unify PhD-students within molecular and structural biology by establishing National/Nordic meeting places through conferences, workshops and national PhD-courses, and quite important; grant all those activities for the participating students. The activities are expected to improve the scientific quality of the PhD-education, unify the structural biology scientists in Norway and the Nordic countries as well as familiarize the students with innovation processes, and thereby improve career opportunities. BioStruct offers a research education in structural biology, and covers projects within e.g. biomedicine, plant biology, marine biology, microbiology, basic biomolecular research and (bio)nanoscience, with focuses on molecular analysis using structural data. The school is as such technologically based rather than thematic, and it is open to all PhD-students using both experimental and theoretical methods for obtaining structural information of biological molecules. The Norwegian Graduate School in Structural Biology is led and administered by the Norwegian Structural Biology Centre (NorStruct) at the University of Tromsø. The graduate school includes at present 60 PhD students from 45 research groups, covering 12 Departments from 6 Norwegian universities. The partners, as a whole, generate a unique group of expertise and experimental facilities in structural biology in Norway that ensures a high quality PhD-education. The graduate school will interact closely with relevant industry and is also a member of the Nordic network of PhD schools administered by ISB (The National Doctoral Programme in Informational and Structural Biology).
The safety and quality of products made from different materials depend on the quality of metrological assurance used for characterization of the composition and properties of these materials. Modern diffractometric systems have new components which increase the productivity of these systems, whereas they may cause new uncertainties in the results of determining of the characteristics based on the diffraction pattern measurement data. Therefore of the considerable changes are needed in the Testing Program for Type Approval. Note that some manufacturers and users may not pay due attention to the metrological assurance, and the reliability and repeatability of characteristics. Some types of diffractometers are tested only for one and unconventional characteristic of the diffraction pattern, for example, angular position at small angles of diffraction reflections. As results is allows provide assurance for approximate phase analysis only. The accuracy for the positions of these reflections can be lower by one order of value than for the reflections whose positions are at very high values of angles, but it is based on these values that the uncertainty of crystal lattice parameters is determined just. In order to provide a more profound and overall testing of diffractometers for Russian Federation have been developed a new programs and certified measurement procedures and the system of Certified Standard Reference Materials (CSRM) of diffraction properties, based on stable physical characteristics and related to the parameters of the diffraction pattern [1-2]. Note that the results of comparative measurements show that the achieved accuracies for our CSRM and for the similar SRM systems available at NIST are alike. This CSRM system allows to conduct tests of X-ray diffractometers for conventional and new purposes: 1) a quantitative phase analysis based on the ratio of reflection intensities and on the results of measuring of a complete diffraction pattern using the Rietveld methods; 2) determining of micro-structural characteristics (grain sizes, sizes of nano-fragments and the value of micro-distortions of a crystal lattice) which are in demand especially in the machine-building, microelectronics and bio-nanotechnology. For this purpose we use CSRM and Measures with different levels of micro-distortions and taking into account the atomic weights of components; 3) determining of the life-service of a product on the basis of residual stress. The use is made of tablet-shaped, sintered CSRMs and measures; 4) for single crystal diffractometers we have developed new relevant and required CSRMs also.
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