Precision-mechanisms for high accuracy beamline instruments at the ESRF: A review

High accuracy beamline instruments have been designed and developed for 12 years at the ESRF with an increasing demand of static and dynamic qualities. Over the last five years, microscopy beamlines, and more generally, the need for micro positioning when using small X-ray beams, has been a driving force for improving instrument compactness when combining movements, and a consequence has lead to a high level of intricacy. Even if resolutions of 0.1 μm, and high quality guiding (70 μrd), are easily found in commercially available translation stages, overall sizes and lever arms can lead to larger spheres of confusion. Moreover, environmental considerations such as vacuum compatibility can further restrict the choice of appropriate translations. To meet the various needs of the micro-focusing beamlines, compact and high-resolution micro-jacks, and xyz vacuum compatible cross tables have been developed in-house. A series of standard low profile components such as elevators (1 μm10mm), μ rotary tables (Laue angle rocking curve), sample slits, inserted with either pico motors or stepper Hacks are now available. Using this approach an integrated all in one experimental station was designed for X-ray microscopy beamlines, like the scanning X-ray microscope for ID21, (10 sub-micron axes operated at 10-6mbars). Other versions are currently being developed for micro-fluorescence beamlines or post monochromators. The development programme has benefited greatly from the presence of the ESRF precision engineering laboratory (PEL), which allowed high quality metrology measurements to be performed on both the prototype and the final systems.