Exploiting the full potential of the ESRF storage ring sources remains a permanent challenge for the experimentalist. The optics used today to adapt the X-ray beam properties to the experiments are not always of the quality needed to reach the diffraction limit. For example, the spot size produced by focusing elements such as curved mirrors is still about an order of magnitude above the theoretically possible limit, situated at about 50 nanometres. The detector can also severely reduce the data flux compared to what could be reached in an ideal situation, in particular when recording two-dimensional images. Efforts are required to improve the performance of the instrumentation, both before and after the sample, so that our Users will be in a even better position to carry out outstanding experiments. Diversification of both optical elements and detectors is needed to better match the beam properties to the experiment and thus optimise the resolution-flux-count rate chain.

The present chapter reports on several technical developments that go along these lines: to improve the experiments and increase their scope by providing better performance and more diverse choices. We begin with "simple" slit systems, where new "clean" slits have been developed that do not create artefacts by blade roughness and that are compatible with the coherence properties of the X-ray beams. Once its cross-section is well defined, the beam must be further conditioned and in many cases focused to very small dimensions, often below a micrometre, in order to assess structural information on the mesoscopic scale. This can be done by several methods according to the specific experimental technique employed. A beautiful example of a micro-focusing experiment is the microcrystallographic study of samples of historical interest using a recently developed X-ray waveguide that compresses the beam down to 0.1 micrometres. The vertical aperture of this one-dimensional beam condenser is, however, quite small and therefore focusing elements accepting wider beams and able to focusing in two dimensions must be available. A well-known system is the double-focusing Kirkpatrick-Baez (KB) mirror device where two curved substrates, coated either by a single metallic layer or by a stack of multilayers, concentrate the beam to a very small spot. The focusing efficiency depends on the quality, i.e. roughness and figure of the mirrors or multilayers. Here substantial progress has been achieved recently and the fabrication of several KB systems is envisaged.

Focusing can also be produced by single crystals, which, in addition to focusing, select a narrow bandwidth out of a white beam. Usually the crystals must be bent to do so, but the clever use of refraction effects that always occur at single crystal diffraction, allows us to create a converging beam. This very recent and novel technique has the obvious advantage that no complex and accurate mechanical structures are needed for bending. It appears that it also provides some energy tunability. It is very unlikely that focal dimensions smaller than about 10 micrometres can be reached, but this is sufficient for many applications. With respect to more flexibility, the development of "tailored" multilayers with a very wide or a narrow spectral window will allow the user to choose between more possibilities and thus to find a better compromise between resolution and intensity.

Finally, in the last contribution to this chapter the most recent state-of-the-art of detector performance and development at the ESRF is described presenting impressive achievements and perspectives in this very important field of synchrotron instrumentation.