An assessment of diamond turning for the production of silicon X-ray optical elements

A number of high-perfection single-crystal silicon specimens have been diamond turned under various conditions. Surface roughness was assessed visually and with a Talysurf 5 machine and lattice perfection monitored by double-axis X-ray diffractometry. No significant variation in roughness was found with turning speed and the flatness was approximately 0.1 μm. An increase of integrated intensity and full width at half maximum of the X-ray rocking curve of up to a factor of nine was observed. Most of this damage was shown to be confined to within the first few micrometers from the surface. It is concluded that diamond turning is a viable technique for the fabrication of a range of intricately figured X-ray optical elements including mirrors and high-energy-resolution monochromators, and also medium-band-pass high-intensity-beam conditioners where only one Bragg reflection is used. It is also concluded that X-ray diffractometry is a powerful technique for the investigation of the material damage in advanced machining processes.