The permanently evolving fields of microimaging and phase-contrast based imaging, time-dependent studies and the ever increasing X-ray power ­ mainly due to new in-vacuum insertion devices ­ give rise to ongoing improvements and create new challenges for beamline instrumentation.

In this chapter, the progress of two very recent imaging techniques, namely holotomography and atomic-resolution X-ray holography, is presented. The first method is based on the phase contrast that can be observed in coherent X-ray beams when the X-rays pass through samples composed of volumes with different refractive indices. The boundaries of these zones can be made visible with much higher sensitivity than when the traditional absorption contrast is used. This opens a wide range of important applications in areas such as medical imaging and materials science. The second technique again studies the local atomic environment by phase-shift effects, but on a much smaller scale, and similar to that of EXAFS experiments. Whereas the first method observes objects of sizes ranging from micrometres up to centimetres (X-ray beam size), the second concentrates on atomic arrangements within a few angstroms.

The other contributions selected for this chapter describe the tools, in particular the properties of the optical elements, that allow us to extend the capabilities of the instrumentation to better resolution and higher sensitivity, or simply to a better conservation of the unique properties of the ESRF X-ray beams. Two of them deal with improvements of optical elements for focusing: blazed Fresnel zone plates and curved multilayers with a gradient in the layer thickness along the beam footprint. Both are diffractive optics as opposed to refractive and specular (mirror) optics, which are also used on ESRF beamlines. We thus have the possibility of choosing the element(s) that are best suited for a given application. Thanks to the development of blazed zone plates and perfectly-shaped and homogeneously-graded multilayers, sub-micrometre resolution can now be achieved with high efficiency. Hence, the term "microfocusing" could even be replaced by "nanofocusing".

The performance of mirrors and multilayers, with respect to both coherence preservation and focusing, critically depends on the surface quality (microroughness and slope or shape errors). Here a big step forward has been achieved by ion-beam figuring which increases the surface quality by one order of magnitude. Furthermore, it is very important to keep the optical quality unchanged when the element is exposed to the very intense X-ray beam. The question of how much we can increase the source strength without substantial losses caused by the thermal deformation of the optics ­ generated by cooling ­ must be addressed. Significant progress has been made to understand the diffraction process in deformed crystals and to predict, with a high level of confidence, the performance of crystal optics by combining finite element analysis with diffraction theory.

Finally, a recent result of time-resolved applications of synchrotron radiation is presented. Here the multiple reflections of X-rays in a channel cut crystal were studied in backscattering geometry; the X-rays were "stored" in a kind of cavity for a few nanoseconds.