The manufacture and properties of compound refractive lenses (CRLs) for hard X-rays with parabolic pro®le are described. These novel lenses can be used up to $60 keV. A typical focal length is 1 m. They have a geometrical aperture of 1 mm and are best adapted to undulator beams at synchrotron radiation sources. The transmission ranges from a few % in aluminium CRLs up to about 30% expected in beryllium CRLs. The gain (ratio of the intensity in the focal spot relative to the intensity behind a pinhole of equal size) is larger than 100 for aluminium and larger than 1000 for beryllium CRLs. Due to their parabolic pro®le they are free of spherical aberration and are genuine imaging devices. The theory for imaging an X-ray source and an object illuminated by it has been developed, including the effects of attenuation (photoabsorption and Compton scattering) and of the roughness at the lens surface. Excellent agreement between theory and experiment has been found. With aluminium CRLs a lateral resolution in imaging of 0.3 mm has been achieved and a resolution below 0.1 mm can be expected for beryllium CRLs. The main ®elds of application of the refractive X-ray lenses are (i) microanalysis with a beam in the micrometre range for diffraction,¯uorescence, absorption, scattering; (ii) imaging in absorption and phase contrast of opaque objects which cannot tolerate sample preparation; (iii) coherent X-ray scattering.

We describe refractive x-ray lenses with a parabolic profile that are genuine imaging devices, similar to glass lenses for visible light. They open considerable possibilities in x-ray microscopy, tomography, microanalysis, and coherent scattering. Based on these lenses a microscope for hard x rays is described, that can operate in the range from 2 to 50 keV, allowing for magnifications up to 50. At present, it is possible to image an area of about 300 m in diameter with a resolving power of 0.3 m that can be increased to 0.1 m. This microscope is especially suited for opaque samples, up to 1 cm in thickness, which do not tolerate sample preparation, like many biological and soil specimens.

Hard x-ray absorption spectroscopy is combined with scanning microtomography to reconstruct full near-edge spectra of an elemental species at each location on an arbitrary virtual section through a sample. These spectra reveal the local concentrations of different chemical compounds of the absorbing element inside the sample and give insight into the oxidation state, the local atomic structure, and the local projected free density of states. The method is implemented by combining a quick scanning monochromator and data acquisition system with a scanning microprobe setup based on refractive x-ray lenses.

The piezo XAFS technique in combination with an in situ cell has been used for the investigation of fast solid-solid transformations with millisecond time resolution. The technique records X-ray absorption spectra (XAFS) in a continuous mode by making use of piezo tilt tables in the X-ray monochromator, which are actuated by an oscillatory high voltage. The application of this technique in the field of solid-state chemistry and catalysis is illustrated by investigations of the X-ray absorption near-edge structure (XANES) of the Cu K edge during the autocatalytic reduction of a Cu/ZnO methanol catalyst and the spontaneous decomposition of (NH 4 ) 2 Cr 2 O 7 to Cr 2 O 3 . The reduction of Cu(II) to Cu(0) occurs within a few seconds. The existence of an intermediate Cu(I) phase could be revealed by the analysis of the preedge position and the white line intensity, but the Cu(I) intermediate is very unstable. The spontaneous decomposition of (NH 4 ) 2 Cr 2 O 7 occurs within about 30 s and shows after a short acceleration period a rather constant reaction rate and a quite long decay period.

The Piezo-QEXAFS technique is a novel tool for time-resolved X-ray absorption spectroscopy in the hard X-ray range. Monochromator components consisting of specialized tilt stages to perform fast energy scans, lightweight crystal holders, bending mechanics, and control electronics are being installed and commissioned. It is planned to perform fast EXAFS scans with time resolution in the millisecond range. With Piezo-QEXAFS all typical X-ray absorption experiments will be possible as it retains the standard linear geometry. The achieved time resolution opens interesting insights into the dynamics of phase transitions and chemical reactions.

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The Piezo-QEXAFS technique is a novel tool for time-resolved X-ray absorption spectroscopy in the hard X-ray range. It makes use of piezo tilt tables mounted below the crystals in a double crystal or channel cut crystal monochromator. Repetitive energy scans are performed by applying an oscillatory high voltage to the piezo translators of the tilt tables. This year, new components consisting of specialized tilt stages, lightweight crystal holders and control electronics have been commissioned to improve the performance. It is now possible to perform fast scans over a larger energy range with a time resolution in the ms range. With Piezo-XAFS all typical X-ray absorption experiments are possible. All detection modes can be used, especially fluorescence detection, which is suitable even for highly diluted systems. The achieved time resolution opens interesting insights into the dynamics of chemical reactions and phase transitions. The method will be described in detail and latest results from performance tests and scientific applications will be discussed.

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