[en] A double crystal diffractometer (DCD) for testing LiF crystals is presented. It is possible to distinguish in a relatively short measuring time (nearly 10 minutes including change of sample and adjustment) between crystals with block desorientation angles > 1' and <= 1' (1' = 0.291x10^-3 rad). The extention of area registered during a measurement depends on the kind of section of crystal and the kind of reflection; at the examination of |100|-cleavage faces of LiF an elliptical area of a height of 15 mm and a length of 115 mm is registered. (author)

[en] This paper describes a new method for the simultaneous measurement of the integrated reflectivity of a crystal for multiple orders of reflection at a predefined Bragg angle. The technique is demonstrated with a mica crystal for Bragg angles of 43^o, 47^o, and 50^o. The measured integrated reflectivity for Bragg reflections up to the 24th order is compared with new theoretical predictions, which are also presented in this paper

[en] Complete text of publication follows. In the last decade, much effort has been given in development of modern dedicated XUV and x-ray free electron lasers with unique properties. Femtosecond laser plasma sources provide ultra-short x-ray pulses of high peak brilliance and can thus be complementary x-ray sources to the undulator based sources. All these modern x-ray sources need dedicated x-ray optics for diagnostics and applications, respectively. The availability of femtosecond XUV pulses from free-electron lasers such as FLASH in Hamburg (Germany) opens up new possibilities to study dense plasmas. These states of matter are characterized either by XUV self-emission of XUV Thomson Scattering. In any case, high resolution XUV spectrometers are highly desired. Additionally, these diagnostics have to be flexible, comparatively small and highly efficient in order to serve various dedicated experiments. X-ray spectroscopy is one of the most important diagnostics of plasmas in the context of laser fusion. Depending on the aims of these experiments (i) monochromatic x-ray images or (ii) high resolution spectra combined with either spatial or time resolution can be obtained. Sophisticated monochromatic imagers with up to 10 toroidally bent crystals have been developed to study the implosion processes in laser fusion experiments; time-resolved maps of plasma parameters were evaluated from the data. High-power femtosecond lasers provide a practical, relatively inexpensive, powerful x-ray flash source. Information on production efficiency, the energy distribution and transport of hot electrons is needed to maximize x-ray output in desired K-shell emission lines ore continuum ranges so that peak brilliances comparable to those of synchrotrons may be feasible. Combining these new sources with bent crystal optics enables diffraction experiments on sub-picosecond time scales. Laser-pump x-ray probe experiments have shown evidence of structure changes in several crystals within 250 fs. These x-ray optics have been designed in our institute using raytracing and Bragg reflection codes for the 1D or 2D bent crystals or combinations thereof. In the preparation process, extreme care has been taken over crystal perfection, selection of optimum reflections, precision bending, measurement of imaging and reflection properties. X-ray topographic cameras and diffractometers are used to check the relevant properties of the analyzer crystals.

[en] Special minimum requirements on the quality of surface treatment must be fulfilled if we want to characterize the volume quality (e.g. substructure) of monocrystals. These requirements depend on the used X-ray reflection. In LiF-monocrystals one finds damage depths up to several 100 μm caused by surface treatment. The integral intensity and the half-value width of X-ray rocking curve have been measured for different reflections and different surface qualities. It is investigated, if the subsurface slice of plastic deformation corresponds with an 'ideal mosaic crystal' and in which manner the results of measurements are influenced by the surface roughness. The method is useful for the characterization of subsurface damages generated by the surface treatment of crystals. (author)

[en] Theoretical design of a new type of the bent crystal spectrometer based on a combination of the vertical dispersion principle with diffraction of x rays from the asymmetrically cut crystal is reported. The novel instrument produces simultaneously two sets of mirror-symmetric spectra, and provides large dispersion, high spectral and 1D spatial resolution with a variable magnification. The analytic formulas describing the function of the spectrometer are complemented by its detailed quantitative analysis based on the ray tracing procedure. The method for reconstruction of the recorded spectra is described, the parameters influencing the precision of the wavelength determination are discussed. The comparison of the main predicted and experimentally observed characteristics verifies the developed theory and demonstrates the spectrometer performance. The novel instrument is particularly suitable for precise measurements of profiles and positions of the narrow-band spectral features observed in the emission of laser-generated plasmas

[en] The focusing properties of asymmetrically cut bent crystals in Bragg geometry are discussed. The conditions for optimized one- and two-dimensional polychromatic imaging of x-ray sources are proposed. In particular configurations, the schemes with asymmetrically cut crystals provide smaller aberrations and slightly higher collection efficiency than symmetrically diffracting optical elements. The analytical results are cross-checked with ray-tracing simulations, the validity of theoretical predictions is verified experimentally for one-dimensional case. (author)

[en] We have performed an analyzer crystal based phase contrast imaging (ABI) experiment using a rotating anode x-ray source. The use of such an incoherent source demonstrates the potential of ABI as a quantitative characterization tool for the laboratory environment. A phase contrast image of a plastic phantom was recorded on high resolution x-ray film and the projected thickness was retrieved from a single image. The projected thickness recovered from the phase contrast image was shown to quantitatively agree with a reference optical microscope measurement

[en] The linear polarization of the 1s2p¹P₁→1s²¹S₀ resonance line, the 1s2p³P_1,2→1s²¹S₀ intercombination lines, and the 1s2s³S₁→1s²¹S₀ forbidden line was measured in heliumlike FeXXV excited near threshold by a monoenergetic electron beam. The measurement was carried out with a high-resolution x-ray spectrometer employing a set of two analyzing crystals that acted as polarizers by selectively reflecting the individual polarization components. A value of +0.56^+0.17_-0.08 was determined for the polarization of the ¹P₁ line, -0.53^+0.05_-0.02 for the ³P₂ line, -0.22^+0.05_-0.02 for the ³P₁ line, and -0.076^+0.007_-0.007 for the ³S₁ line. The measurements were compared with results from a relativistic distorted-wave calculation, which was carried out for a number of mid-Z heliumlike ions (Mg¹⁰⁺endash Kr³⁴⁺), and good agreement was found. By contrast, disagreement was noted with predictions based on Coulomb-Born calculations, allowing us to distinguish between theoretical approaches. copyright 1996 The American Physical Society

[en] Focal aberrations of large-aperture highly oriented pyrolytic graphite (HOPG) crystals in von-Hàmos geometry are investigated by experimental and computational methods. A mosaic HOPG crystal film of 100 μm thickness diffracts 8 keV x-rays. This thickness is smaller than the absorption depth of the symmetric 004-reflection, which amounts to 257 μm. Cylindrically bent crystals with 110mm radius of curvature and up to 100 mm collection width produce a X-shaped halo around the focus. This feature vanishes when the collection aperture is reduced, but axial spectral profiles show that the resolution is not affected. X-ray topography reveals significant inhomogeneous crystallite domains of 2±1mm diameter along the entire crystal. Rocking curves shift by about ±20arcmin between domains, while their full width at half-maximum varies between 30 and 50 arcmin. These inhomogeneities are not imprinted at the focal spot, since the monochromatically reflecting area of the crystal is large compared to inhomogeneities. Ray-tracing calculations using a Monte-Carlo-based algorithm developed for mosaic crystals reproduce the X-shaped halo in the focal plane, stemming from the mosaic defocussing in the non-dispersive direction in combination with large apertures. The best achievable resolution is found by analyzing a diversity of rocking curve widths, source sizes and crystal thicknesses for 8 keV x-rays to be ΔE/E ∼ 10⁻⁴. Finally a general analytic expression for the shape of the aberration is derived.

[en] We have measured the polarization purity of undulator radiation at 12.9 keV, with hitherto unachievable precision. We could measure a polarization purity of 1.8 × 10⁻⁴ by using a silicon channel-cut crystal with six Bragg reflections at 45° as analyzer.