X-ray Optics for Synchrotron Radiation; Perfect Crystals, Mirrors and Multilayers

The X-ray optical properties of mirrors and Bragg reflecting perfect crystals are almost perfectly matched to the characteristics of synchrotron-radiation sources. That the X-ray refractive index is close to but less than one was realised early in the history of X-ray scattering – consequences are that mirrors exhibit total external reflection over a small angle range, ca 0.01 rad, and perfect crystals totally reflect X-rays in a small angle range, ∼ a few seconds of arc near the Bragg angle. The theory and application of these unique properties was developed in considerable detail in the three decades before the advent of the synchrotron-radiation era. This historical development is traced with special emphasis on the way in which the optical concepts were then straightforwardly applied to synchrotron-radiation X-ray optical design. In more recent times, the technology of synthetic multilayers has been developed so that these too are widely used in X-ray optics for synchrotron-radiation beamlines. As X-ray synchrotron-radiation sources were born, perfect-crystal X-ray optics and crystal-growth technology matured; this symbiosis was not planned, it could not have been planned … but it works, spectacularly!