Ion Beam Figuring and Optical Metrology System for Synchrotron X-ray Optics

摘要

Meeting the ever-increasing performance demands of X-ray beamlines at modern synchrotrons, such as Diamond LightSource (DLS), requires the use of ultra-high-quality X-ray mirrors with surface deviations of less than a few nanometresfrom their ideal shape. Ion beam figuring (IBF) is frequently used for creating mirrors of this precision, but achieving thehighest accuracy is critically dependent on careful alignment and precise metrology of defects on the optical surface.Multiple iterations of measurement and correction are typically required, and convergence towards the requisite shape canbe a slow process. DLS have designed and built an in-house IBF system that comprises a large diameter DC gridded ionsource, and a 4-axis motion stage for manipulating the mirror being figured. Additionally, a slope measuring profilometerfor in-situ metrology, and an imaging system for alignment, are also built into the system. The advantages of incorporatingthese extra components are twofold: fast metrology feedback after each figuring run will considerably reduce the timerequired to perform multiple figuring iterations; and alignment and indexing errors will be drastically reduced whentransferring the optic. Complemented by the Optical Metrology Laboratory at DLS and at-wavelength X-ray measurementson the Test beamline B16, it is expected that this system will enable rapid development and testing of high-quality mirrorswith novel designs for micro- and nano-focussing of X-rays.