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International audience; Paleontologists are quite recent newcomers among the users of X-ray synchrotron imaging techniques at the European Synchrotron Radiation Facility (ESRF). Studies of the external morphological characteristics of a fossil organism are not sufficient to extract all the information for a paleontological study. Nowadays observations of internal structures become increasingly important, but these observations should be non-destructive in order to preserve the important specimens. Conventional microtomography allows performing part of these investigations. Nevertheless, the best microtomographic images are obtained using third-generation synchrotrons producing hard X-rays, such as the ESRF. Firstly, monochromatisation avoids beam hardening that is frequently strong for paleontological samples. Secondly, the high beam intensity available at synchrotron radiation sources allows rapid data acquisition at very high spatial resolutions, resulting in precise mapping of the internal structures of the sample. Thirdly, high coherence leads to additional imaging possibilities: phase contrast radiography, phase contrast microtomography and holotomography. These methods greatly improve the image contrast and therefore allow studying fossils that cannot be investigated by conventional microtomography due to a high degree of mineralisation or low absorption contrast. Thanks to these different properties and imaging techniques, a synchrotron radiation source and the ESRF in particular appears as an almost ideal investigation tool for paleontology.

The main limitation of Laue geometry for the achievement of a small focus size is the focus broadening caused by the intrinsic Darwin width and the spread of the beam in the Borrmann triangle, resulting from propagation inside the crystal. A method, based on dynamical focusing, is suggested that allows improvement of the quality of high-energy polychromatic focusing by bent crystals in Laue geometry.

The high-resolution von Hamos Bragg crystal spectrometer was constructed for the study of K X-ray emission from low- Z elements and L and M X-ray spectra of medium to high Z elements. Recently, this instrument was applied to high-resolution XES and RIXS studies using X-ray synchrotron radiation at the ID21 and BM5 beamlines at the ESRF. An outline of the spectrometer design and performance characteristics will be given. The studies deal with the energy dependent KL double photoexcitation of argon, the L 3 and M 1 atomic-level widths of elements 54≤ Z ≤77, and the evolution of the K-edge RIXS spectra of manganese oxides.

The aim of this study was to model the edge enhancement effect in in-line holography phase contrast imaging. A simple analytical approach was used to quantify refraction and interference contrasts in terms of beam energy and imaging geometry. The model was applied to predict the peak intensity and frequency of the edge enhancement for images of cylindrical fibers. The calculations were compared with measurements, and the relationship between the spatial resolution of the detector and the amplitude of the phase contrast signal was investigated. Calculations using the analytical model were in good agreement with experimental results for nylon, aluminum and copper wires of 50 to 240 microm diameter, and with numerical simulations based on Fresnel-Kirchhoff theory. A relationship between the defocusing distance and the pixel size of the image detector was established. This analytical model is a useful tool for optimizing imaging parameters in phase contrast in-line holography, including defocusing distance, detector resolution and beam energy.

The high-resolution spectra of thorium Mα 1,2 (M 5 N 6,7 ) and Mβ(M 4 N 6 ) X-ray lines induced by O and Ne ions with energies 376 and 178 MeV, respectively, have been measured using a von Hamos crystal spectrometer. The measured spectra exhibit the pronounced X-ray satellite structure due to the multiple ionization in the N- and M-shells. In particular the N-shell satellites are well resolved and the M-shell hypersatellites are clearly observed, to the best of our knowledge, for the first time. The observed M-X-ray diagram transitions and their satellites are interpreted using the multi-configuration Dirac-Fock (MCDF) calculations performed for the multi-vacancy configurations including up to two spectator vacancies. The comparison shows that calculations for more vacancies are needed to reproduce the measured X-ray structure. On the other hand, the data are well interpreted qualitatively using a simplified model of the “average” MCDF satellites having binomially distributed intensities. Further MCDF calculations are in the progress, which ultimately allow to extract precise (∼0.5 eV) information on the electronic structure of the multiple ionized thorium.

We report on the fabrication of diamond and silicon refractive X-ray lenses. These are made using e-beam lithography and deep reactive ion etching. The diamond lenses are promising candidates for optics meeting the extreme requirements of planned X-ray sources based on the free electron laser principle. The silicon lenses are well suited for micro-focusing applications at hard X-ray energies above 20 keV. We measured efficiencies up to 78% and a width of the line-focus down to 3 µm for these lenses. The possibility to compensate for lens aberrations using stacked lenses is discussed. A simple method for the stacking of two silicon devices (lenses) by means of micro-mechanical alignment marks is shown, giving an alignment accuracy in the micron range.

The Kβ spectrum of 42Mo bombarded by 20.8 MeV/amu carbon ions was measured with high-resolution using a transmission-type bent crystal spectrometer operated in the modified DuMond slit geometry. The M-shell satellites of the Kβ2 transition could be well resolved, whereas for the Kβ1,3 transitions only a broadening and shift of the line centroid was observed. The composite structure of the satellite lines which consist of many components that vary in energy and strength was analyzed using theoretical energies and relative intensities obtained from multiconfiguration Dirac–Fock calculations. From the data analysis average M-shell satellite-to-diagram line yield ratios were deduced for both the Kβ1,3 and Kβ2 transitions. For the Kβ2 transition for which the relative contributions of the 3s,p and 3d spectator vacancies to the observed Kβ2M1 satellite yield could be determined, separated X(Kβ2M11,2,3):X(Kβ2M0) and X(Kβ2M14,5):X(Kβ2M0) yield ratios could even be extracted.

The fabrication and testing of planar refractive lenses made from diamond and silicon is reported. We obtained efficiencies up to 78% and 31 % for diamond and silicon lenses, respectively. A FWHM of the line-focus down to 3 pm has been achieved for both types of lenses. Using two crossed silicon lenses in series 2-dimensional focusing has been demonstrated, resulting in a micro focus of 7*14 μm at 35 key This demonstrates the feasibility of silicon lenses for micro-focusing applications at extreme photon energies (above approx. 30 keV). Due to the unique physical properties of diamond, diamond lenses should be able to withstand the extreme flux densities expected at future X-ray free electron lasers (X-FELs). This makes diamond refractive lenses very promising candidates for applications at these 4'generation x-ray sources.

The fabrication and testing of planar refractive hard X-ray lenses made from bulk CVD diamond substrates is reported. The lens structures were generated by electron-beam lithography and transferred by reactive-ion etching into the diamond. Various lens designs were fabricated and tested at 12.4 and 17.5 keV photon energy. Efficiencies of up to 71% and gains of up to 26 were achieved. A line focus of 3.2 micro m (FWHM) was measured. These lenses should be able to withstand the extreme flux densities expected at the planned fourth-generation X-ray sources.

High-resolution measurements of the Kα x-ray spectra of metallic Ca, Ti, Cr and Fe were performed with a von Hamos Bragg crystal spectrometer. The target x-ray emission was induced by 34, 72 and 134 MeV C ions, 28, 64 and 230 MeV O ions and 43, 160 and 380 MeV Ne ions. The energies of the resolved KαLN x-ray satellite lines were determined. The possible variation of the energy differences between neighboring KαLN lines with the projectile energy, projectile atomic number and number of target L shell spectator vacancies was probed. No significant dependence on the projectile characteristics was observed. In contrast, the absolute energies of the KαLN satellite lines were found to depend on the projectile velocity. This dependence was attributed to the additional M shell ionization of the target atoms. Copyright © 2003 John Wiley & Sons, Ltd.

The ongoing need for single crystal diamond of high quality in physics research and application, has been amply demonstrated. This need cannot be satisfied by access to natural diamonds. In recent years much progress has been made in the synthesis of diamond at high temperature and high pressure. Several interrogation methods were deployed to ascertain the crystal quality attainable for HPHT diamond. It is shown that the best of such materials can approximate in quantitative terms closely to the theoretical predictions for perfect diamond.

For several years now, the ESRF, the University of the Witwatersrand and Messrs. De Beers Industrial Diamonds (Pty) Ltd. through their Diamond Research Laboratory, have pursued a development programme to assess and improve the quality of synthetic diamonds. Recently, in an effort to study the influence of nitrogen impurities on the defect structure, X-ray excited optical luminescence and spatially resolved double-crystal diffractometry were employed as new techniques. The correlation between nitrogen impurities and the raw defect structure was clearly visible. It was confirmed that concentration variations are related to lattice imperfections, where tilts are much more important than lattice constant variations. High reflectivity was observed and quite large zones of a sample bigger than 1 cm 2 showed to be perfect to within better than 0.5 arcsec.

The aim of this work is to generate the rocking curves of monochromators exposed to heat load in synchrotron radiation beams with a computer code performing diffraction calculations based on the theory of Takagi and Taupin. The model study starts with the calculation of deformation by finite element analysis and from an accurate characterization of the incident wave and includes the simulation of the wavefront propagation between the first and the second crystal (analyzer) of a double crystal monochromator. A monochromatic plane wave as well as a polychromatic spherical wave approach is described. The theoretical predictions of both methods are compared with experimental data measured in Bragg geometry and critically discussed.

In this paper we present the details of the finite element modeling (FEM) procedure used to calculate the thermal deformation generated by the X-ray power absorbed in silicon crystals. Different parameters were varied systematically such as the beam footprint on the crystal, the reflection order and the white beam slit settings. Moreover, the influence of various cooling parameters such as the cooling coefficient and the temperature of the coolant were studied. The finite element meshing was carefully optimized to generate a deformation output that could be easily read by a diffraction simulation code. Comparison with the experiments shows that the peak-to-valley slope error calculated by the FEM is an excellent approximation of the rocking curve width for a liquid nitrogen cooled silicon (3 3 3) crystal, and a quite good approximation for significantly deformed silicon (1 1 1) crystals.

For several years the ESRF, the University of the Witwatersrand and De Beers Industrial Diamonds (PTY) Ltd through their Diamond Research Laboratories have pursued a development programme to improve the quality of synthetic diamond crystals. Recently, in an effort to study the influence of nitrogen impurities on the defect structure, x-ray excited optical luminescence and spatially resolved double-crystal diffractometry were employed as new techniques. Finally, the impurity concentration distribution obtained by optical spectroscopy was superimposed on the defect structure determined by x-ray diffraction. The correlation between nitrogen impurities and the raw defect structure was clearly visible. It was confirmed that concentration variations are related to lattice imperfections, where tilts are much superior to lattice parameter variations.

A multilayer Bragg–Fresnel x-ray lens (MBFL) structure that combines diffraction and geometric focusing on a single device is presented. With the MBFL, the linear BFL focuses the x-ray beam vertically while the bent multilayer focuses x rays horizontally. This combination eliminates the need for a second mirror in the conventional Kirkpatrick–Baez-based microprobe, which will be advantageous in x-ray fluorescence microscopy as well as microdiffraction applications. The characterization of the MBFL was carried out at the European Synchrotron Radiation Facility and a 1.6 μm (vertical)×12 μm (horizontal) focus was obtained from a 250 μm (V)×200 μm (H) incident beam. With a binary Fresnel lens efficiency of about 35% this yields a gain of almost three orders of magnitude compared to obtaining the same spot size by a raw aperture.

The sagittal deviation of a Laue-diffracted X-ray beam caused by the inclination of an exit crystal surface with respect to an entrance crystal surface has been studied both theoretically and experimentally. The use of this effect for sagittal focusing of X-ray synchrotron radiation diffracted by a Laue crystal is suggested. The focusing is based on the refraction effect due to the parabolic profile of an exit or/and entrance surface. The crystal is not bent. In order to achieve a reasonable focusing distance, the crystal should be cut asymmetrically. The experiment was performed at beamline BM5 at the ESRF.

The first experimental results of a high-resolution study of Th and U Lγ-X-rays induced in collisions with 230 MeV and 360 MeV oxygen ions, undertaken to investigate the dynamics of the multiple ionization in M-, N- and O-shells and the structure of M- and N-shell X-ray satellites, are reported. The measurements were performed using the transmission curved- crystal spectrometer installed in DuMond geometry. An instrumental resolution of about 10 eV was achieved for Lγ (L-N,O) X-ray transitions, allowing clear separation of M-shell X-ray satellites for Th and U. Moreover, the N-shell satellite structure in the Lγ6 (L2-O4) X-ray transition was observed for 360-MeV O ion impact on a thorium target. This, to our knowledge, is the first observation of this kind. Other observed Lγ X-ray diagram lines are shifted and widened, with respect to the photoinduced X-ray spectra excited by an X-ray tube, due to the unresolved N-shell and, probable the O-shell, satellite structure.

We propose a novel approach for the theoretical analysis of the photoinduced high-resolution K(h)α(1,2) x-ray hypersatellite spectra, which allows us to obtain reliable values of lifetimes of the doubly K-shell ionized states and fundamental information about the relative role of K-shell double photoionization (DPI) mechanisms. It is demonstrated for the first time that the K(h)α(1,2) hypersatellite natural line broadening observed for selected metal atoms with 20 ≤ Z ≤ 30 can be well reproduced quantitatively by taking into account the influences of the open-shell valence configuration (adopted from predictions of the band-structure method) and the outer-shell ionization and excitation following the DPI process.

Recent X-ray optical experiments have validated previous theoretical work on focusing by bent crystals in Laue geometry. It was shown that a suitable choice of the crystal thickness significantly improves the focusing performance of the crystal by combining the dynamical focusing of the Borrmann triangle with the geometrical focusing obtained by the crystal bending. The best focus size achieved during the experiments was less than 5 µm and is in practice limited by the source demagnification for the considered setup.

The use of fast in-situ X-ray computed micro-tomography with careful 3D image analysis has allowed the development of gas cell structure during dough fermentation to be followed, within a volume close to 0.1 cm 3 with a resolution of 15 μm. Yeast and liquid (water +oil) contents were modified in the dough composition. The evolution of dough was followed until the void volume fraction reached 0.7, after an inflection point. The gas cell and cell wall size distributions were determined by granulometry and their initial values were respectively 180 and 240-300 μm. The evolution of the mean cell wall size displayed a minimum plateau (180-240 μm) in a time interval [ t 1 , t 2 ]. Before t 1 , bubbles grow freely and beyond t 2 , coalescence appears to prevail, as shown by the irregular structure depicted by the cell size distribution. The value of t 1 is found to increase by a factor of 2 when the concentration of yeast is reduced by 2, and replacing 5% water by 10% oil also increases t 1 . Both changes of composition lead to more irregular cellular structures. Similar analyses were performed during the baking step, which allowed the interval of temperature for crumb setting to be determined, and showed that little change of cellular structure occurred during baking.

We report on the fabrication and testing of linear multilevel zone plates made of silicon. The lenses were tilted with respect to the x-ray beam, enabling an increase of the effective height of the diffractive structures in order to obtain optimal efficiency of these devices even for high photon energies. We achieved unprecedented diffraction efficiencies between 64 and 67% (between 47 and 59% considering membrane absorption) for photon energies between 10 and 15 keV. As a linear zone plate acts as a cylindrical lens, two perpendicular lenses have to be put in series to obtain a 2-D focusing. The resulting micro-focusing device has a very high total efficiency (approx. 30%) and can be matched to the asymmetry of synchrotron in order to obtain a symmetric micro-focus.

We demonstrate that in order to interpret the x-ray satellite structure of Pd Lα1,2(L₃M4,5) transitions excited by fast O ions, which was measured using a high-resolution von Hamos crystal spectrometer, the vacancy rearrangement processes, taking place prior to the x-ray emission, have to be taken into account. The measured spectra were compared with the predictions of the multi- con.guration Dirac-Fock (MCDF) calculations using the fluorescence and Coster- Kronig yields which were modiffed due to a reduced number of electrons available for relaxation processes and the effect of closing the Coster-Kronig transitions. We demonstrate that the vacancy rearrangement processes can be described in terms of the rearrangement factor, which can be calculated by solving the system of rate equations modelling the flow of vacancies in the multiply ionized atom. By using this factor, the ionization probability at the moment of collision can be extracted from the measured intensity distribution of x-ray satellites. The present results support the independent electron picture of multiple ionization and indicate the importance of use of Dirac-Hartree-Fock wave functions to calculate the ionization probabilities.

X-ray resonant Raman scattering (RRS) spectra of Al, Al{sub 2}O{sub 3}, Si, and SiO{sub 2} were measured at the European Synchrotron Radiation Facility, using a high-resolution Bragg-type curved crystal spectrometer. The x-ray RRS spectra were collected at several beam energies tuned below the 1s absorption thresholds of Al and Si. Differences in the spectral features between the elemental samples and the oxide ones were clearly observed. The data were interpreted using the second-order perturbation theory within the Kramers-Heisenberg (KH) approach. It is shown that, using the KH formalism, oscillator strengths that are similar to the ones deduced from x-ray absorption measurements can be extracted from emission x-ray RRS spectra. The total cross sections for the x-ray RRS process were derived for the different photon beam energies and compared with theoretical predictions. For elemental silicon, the weak 1s-3p excitation was observed and found to be consistent with results of density of states calculations.

The x-ray satellite structure of Pd Lalpha1,2(L3M4,5) transition excited by an impact of O7+ and Ne6+ ions with energies 279 and 178 MeV, respectively, which were measured using a high-resolution von Hamos crystal spectrometer, is discussed in terms of the multi-configuration Dirac-Fock (MCDF) calculations. We demonstrate, by using the arguments of the general central limit theorem (GCLT), that a structure of complex M-shell satellites of Pd Lalpha1,2(M-m) transitions for a higher number of spectator vacancies (m > 4), which consists of hundreds of thousands of individual x-ray transitions as obtained from the MCDF calculations, can be well described by a single Voigtian profile. The Lorentzian width of such Voigtian line can be well modeled by using the results of the MCDF calculations for simpler configurations with a number of vacancies m < 4 . This method allows one to describe realistically a complex structure of M-shell satellites, thus extending the applicability of the MCDF calculations, which are limited by an increasing complexity of numerical calculations.

We report on the first high-resolution measurements of the K x-ray resonant Raman scattering (RRS) in Si. The measured x-ray RRS spectra, interpreted using the Kramers-Heisenberg approach, revealed spectral features corresponding to electronic excitations to the conduction and valence bands in silicon. The total cross sections for the x-ray RRS at the 1s absorption edge and the 1s-3p excitation were derived. The Kramers-Heisenberg formalism was found to reproduce quite well the x-ray RRS spectra, which is of prime importance for applications of the total-reflection x-ray fluorescence technique.

High-resolution measurements of the resonant X-ray Raman scattering (RRS) of Al and Si and their oxides were performed at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, using a von Hamos Bragg-type curved crystal spectrometer. To probe the influence of chemical effects on the RRS X-ray spectra, Al 2 O 3 and SiO 2 samples were also investigated. The X-ray RRS spectra were measured at different photon beam energies tuned below the K-absorption edge. The measured spectra are compared to results of RRS calculations based on the second-order perturbation theory within the Kramers–Heisenberg approach.

International audience; The use of fast X-ray computed microtomography (CMT) shows that the development of gas cell structures during fermentation first depends on a critical time, t1, determined by overall expansion and before which bubbles grow freely according to a simple exponential law. Afterwards, coalescence rapidly prevails and then leads to a heterogeneous structure, for t≥t2, characterized by a continuous void phase likely to be stabilized by liquid film walls. This result confirms the involvement of minor components in addition to gluten protein for obtaining a desirable bread texture and suggests that their interfacial properties need to be investigated. The use of fast in situ CMT with careful 3D image analysis also provides data for the validation of numerical models of bubble growth. These small scale experiments could be extended to follow the rheological properties of expanding doughs and the temperature-state changes of wheat flour biopolymers which govern bread baking.

K-X-ray spectra of Zr, Nb, Mo and Pd targets bombarded with 250 MeV carbon and 360 MeV oxygen ions are studied with high resolution diffraction spectrometry. Relative yields and natural widths of the Khα1,2 hypersatellite lines are determined and compared with those of the diagram lines. The widths of Khα1,2 lines are compared with the new phenomenological formula which takes into account the retardation of the Khα₁ transition in the LS coupling scheme. The data significantly exceed the expected values. Deduced lifetimes of the double K-hole states are shorter than expected.

In the production of x‐ray microbeams a trade‐off between flux and beam size must often be made, particularly when using a bending magnet synchrotron source since the radiation emitted in the horizontal direction is not collimated. To circumvent this problem we have combined the diffraction from a sagitally‐bent crystal with the meridional focusing of a Kirkpatrick‐Baez (KB) system composed of two reflective surfaces coated with a platinum layer (1st mirror, vertical deflection) and with a Ni/B4C multilayer (2nd mirror, horizontal deflection). The experiments were performed at the ESRF BM5 beamline, for which the most favorable arrangement consisted of illuminating a KB system located faraway from the source with a horizontally converging or diverging beam produced by a sagittally‐bent crystal located closer to the source. The 1st mirror demagnified the vertical dimension of the source whilst the 2nd further decreased the beam in the horizontal direction. Several flux/ spot‐size configurations were tested by changing the position of the image of the sagittal crystal. The best (preliminary) results gave a focus of 2.6 μm (vertical) × 6.8 μm (horizontal) and an irradiance gain of 2.6 104. These figures were limited by the aberrations of the sagittally‐bent crystal.

The BM05 synchrotron X‐ray beamline has been designed to serve as a test and development station. Recently, new instrumentation has been installed to extend its metrology capability. A monochromatic beam can be produced over an energy range spanning from 6 keV to 100 keV using two Bragg Si(111) flat‐crystal monochromators. It is also possible to install a sagittal crystal (6 keV< E< 30 keV) to concentrate the beam horizontally to 300 μm, therefore increasing the photon density by ∼ 2 orders of magnitude. Alternatively, the beam can be concentrated into micrometer or even sub‐micrometer dimensions by placing a Kirkpatrick‐Baez system very close to the sample under study. A double multilayer monochromator mounted in series with the crystal monochromator(s) can retain a fixed‐exit beam and reduce the amount of harmonics by at least 4 orders of magnitude. When used alone, the multilayer monochromator delivers a high‐flux low‐resolution beam. A first set of (Ru/B4C)70 multilayers has been made with a relatively large d‐spacing (4 nm) to match the quality of the mirror substrates and to preserve the coherence properties of the synchrotron source. Ultimately three different coatings will allow to cover the energy band between 6 keV and 30 keV and to vary the energy resolution (ΔE/E) between 5.10−3 and 4.10−2. With two large experimental hutches capable of receiving either white of monochromatic beams and equipped with several diffractometers, optical tables, and detectors, this beamline offers a remarkable and unique flexibility.

The degree of spatial coherence after x‐ray diffraction by synthetic single diamond crystals was investigated. The coherence preservation was measured by means of the Talbot effect for x‐rays at the optics beamline BM5 at the ESRF. The (111)‐ and (100)‐ oriented specimens of type Ib and IIa were grown by De Beers. To establish a correlation between the coherence degradation and the surface quality, 3D surface topography was measured with an optical interferometric profiler and an AFM. Likewise, to pinpoint the relationship with crystalline quality, the samples were characterized by means of double crystal x‐ray diffractometry with microscopic resolution.

In the hard x-ray range, optics based only on refraction, as in the case of visible optics, require extremely small (a few microns) bending radii of the crystal monochromators, since the deviation of the refraction index (δ = 1-n) from unity is of the order of 10 -6 . Based on the principle of a series of N refractive lenses, compound refractive lenses provide an appreciable focus at a reasonable distance, but the photon flux is limited by absorption because of the generally high value of N required. As the effect of refraction is very weak, x-rays deviate considerably when diffraction occurs in a crystal in Bragg geometry: this is the base of many crystal optics devices. Focusing with crystal optics is generally achieved bending the crystals to modify the orientation of the lattices planes or modulating the entrance surface of a flat or curved crystal, the so-called Bragg-Fresnel lens. Sagittal focusing can be also obtained using asymmetrically cut crystals. From a general point of view the focusing by means of bent crystals in Laue geometry is interesting when high energies are used, because the absorption due to the transmission in the crystals is very limited. The use of bent crystals has two big advantages: it allows to accept a great divergence of the incoming radiation, thus increasing the flux of the focused radiation and allowing at the same time to select its frequencies, owing to the Darwin width of the considered reflection. Indeed, the crystal bending enables the diffracting planes to be crossed at the Bragg angle corresponding to each ray of the incident beam and, at the same time, the diffraction process produces a monochromatic beam. Actually, a small Bragg angle implies a rather long beam path in the crystal in the case of Bragg geometry, whereas in Laue geometry the incidence is almost normal: the absorption is therefore minimized upon using a suitably thin crystal. We suggest here a method allowing to improve the quality of high energy polychromatic focusing by bent crystals in Laue geometry.

One of the factors influencing the focus size in diffractive-refractive optics is the quality of diffracting surface. If the surface is uneven, then the diffraction at each point of the surface is a combination of an asymmetric and inclined diffraction (general asymmetric diffraction). This somewhat deviates and spreads the diffracted beam. The integration over the surface hit by an incident beam gives the angular spread of the diffracted beam. It is shown that in some cases (highly asymmetric, highly inclined cut) the etched surface may create the spread of the diffracted beam, such that it causes a significant broadening of the focus. In this case a mechanical-chemical polishing is necessary.

The high resolution, high asymmetric diffractive-refractive x-ray lens was tested at BM5 beamline in ESRF. The lens consists of two Si (111) channel-cut crystals in dispersive arrangement with the angle of asymmetry of 12.7°. The channels have a circular profile with the diameter of 22 mm. The test was performed for the energy of 7.8 - 8.1 keV and the focusing distance of 19 - 20 m. At the place of the focus the beam was squeezed horizontally from 8.8 mm (unfocused beam) to 0.4 mm, i.e. more than 20 times. To get a good reflectivity in such a highly asymmetric diffraction, the cylindrical surface had to be mechanically-chemically polished.

High-resolution measurements of the photoinduced ${L}_{3}\ensuremath{-}{M}_{1}$ and ${L}_{3}\ensuremath{-}{M}_{4,5}$ x-ray emission lines were performed with a reflection-type bent-crystal spectrometer for a variety of elements ranging from xenon $(Z=54)$ to iridium $(Z=77).$ The measurements were performed at the European Synchrotron Radiation Facility in Grenoble, France. From the observed linewidths of the ${L}_{3}\ensuremath{-}{M}_{1}$ x-ray transitions, the widths of the ${M}_{1}$ levels were determined using the ${L}_{3}$ level widths extracted from the measured ${L}_{3}\ensuremath{-}{M}_{5}$ transitions, and assuming for the ${M}_{5}$ levels the widths reported recently by Campbell and Papp [At. Data Nucl. Data Tables 77, 1 (2001)]. In the rare-earth region a Z-dependent broadening of the ${M}_{1}$ level was observed.

The fluorescence $\mathrm{KL}$ x-ray emission of argon induced by impact with monoenergetic photons was observed with a high-resolution reflecting-type bent crystal spectrometer. The measurements were performed at the European Synchrotron Radiation Facility in Grenoble, France. X-ray beam energies in the range $3455 \mathrm{eV}l~\ensuremath{\Elzxh}\ensuremath{\omega}l~6540 \mathrm{eV}$ were used to investigate the $K+L$ double excitation from threshold to saturation. The excitation probabilities were deduced from the satellite-to-diagram line yield ratios $\mathrm{I}(KL\ensuremath{-}{L}_{2,3}L): \mathrm{I}(K\ensuremath{-}{L}_{2,3}).$ Results were compared to predictions based on the model of Thomas and the one of Roy. From the comparison, parameters such as excitation onset energies, high-energy limit shake probabilities, and radius of the $2p$ orbital in ionic Ar were deduced. The satellite line shapes and their evolution with the excitation energy were analyzed with the aid of multiconfiguration Dirac-Fock calculations.

We have conducted a systematic characterization of (111)- and (100)- oriented synthetic diamond crystals comparing the best presently available specimens of two types (Ib and IIa). The samples were grown by the two major diamond producers, namely the De Beers Industrial Diamonds (Pty) Ltd. in South Africa and the Sumitomo Electric Industries Ltd. in Japan. Double-crystal x-ray diffractometry with microscopic spatial resolution and x-ray topography were employed. The type IIa crystals showed much less pronounced defect structure than the Ib crystals for the (100)- orientation, but the (111) samples were comparable. A clear correlation between the distribution of nitrogen impurities in the Ib crystals and the defect structure was observed. The rocking curve widths from small regions of all specimens were very close to theoretical values on the arcsec level, whereas for larger sample areas they were broadened due to both local defects and crystal curvature. The quality of the IIa crystals from De Beers and Sumitomo was comparable.

The synchrotron radiation community has a need for high heat load compatible x-ray monochromators and De Beers Diamond Research Laboratory has made available diamonds that meet these exacting standards. These materials, all Type Ib single crystal diamonds, have been tested at the ESRF on the Optics Beamline BM5 and the Topography Beamline ID19 by x-ray rocking curve and topography techniques for mosaicity, homogeneity, reflectivity and defect types and contents in general. The samples were of orientation (111), (110) and (100) with areal dimensions up to and greater than 10 mm×10 mm and a choice of thicknesses. In addition, the performance of a diamond double crystal arrangement has been evaluated for x-ray energies between 12.4 and 24 keV. Although the quality of the newly grown diamond crystals is high, it is still desirable to further reduce the defect density.

With the ongoing development of insertion devices with smaller gaps the heat load generated by modern synchrotron sources increases continuously. To predict the overall performance of experiments on beam lines it is of crucial importance to be able to predict the efficiency of x-ray optics and in particular that of crystal monochromators. We report on a detailed comparison between theory and experiment for a water-cooled silicon crystal exposed to bending magnet radiation of up to 237 W total power and 1.3 W/mm2 power density. The thermal deformation has been calculated by the code ANSYS and its output has been injected into a finite difference code based on the Takagi-Taupin diffraction theory for distorted crystals. Several slit settings, filters and reflection orders were used to vary the geometrical conditions and the x-ray penetration depth in the crystal. In general, good agreement has been observed between the calculated and the observed values for the rocking curve width.

The trend in synchrotron radiation (x-rays) is towards higher brilliance. This may lead to a very high power density, of the order of hundreds of watts per square millimetre at the x-ray optical elements. These elements are, typically, windows, polarizers, filters and monochromators. The preferred material for Bragg diffracting optical elements at present is silicon, which can be grown to a very high crystal perfection and workable size as well as rather easily processed to the required surface quality. This allows x-ray optical elements to be built with a sufficient degree of lattice perfection and crystal processing that they may preserve transversal coherence in the x-ray beam. This is important for the new techniques which include phase-sensitive imaging experiments like holo-tomography, x-ray photon correlation spectroscopy, coherent diffraction imaging and nanofocusing. Diamond has a lower absorption coefficient than silicon, a better thermal conductivity and lower thermal expansion coefficient which would make it the preferred material if the crystal perfection (bulk and surface) could be improved. Synthetic HPHT-grown (high pressure, high temperature) type Ib material can readily be produced in the necessary sizes of 4-8 mm square and with a nitrogen content of typically a few hundred parts per million. This material has applications in the less demanding roles such as phase plates: however, in a coherence-preserving beamline, where all elements must be of the same high quality, its quality is far from sufficient. Advances in HPHT synthesis methods have allowed the growth of type IIa diamond crystals of the same size as type Ib, but with substantially lower nitrogen content. Characterization of this high purity type IIa material has been carried out with the result that the crystalline (bulk) perfection of some of the HPHT-grown materials is approaching the quality required for the more demanding applications such as imaging applications and imaging applications with coherence preservation. The targets for further development of the type IIa diamond are size, crystal perfection, as measured by the techniques of white beam and monochromatic x-ray diffraction imaging (historically called x-ray topography), and also surface quality. Diamond plates extracted from the cubic growth sector furthest from the seed of the new low strain material produces no measurable broadening of the x-ray rocking curve width. One measures essentially the crystal reflectivity as defined by the intrinsic reflectivity curve (Darwin curve) width of a perfect crystal. In these cases the more sensitive technique of plane wave topography has been used to establish a local upper limit of the strain at the level of an 'effective misorientation' of 10(-7) rad.