X-ray curved-crystal monochromator system at the storage ring DCI

Abstract Focusing in the horizontal plane is achieved by a Ge crystal shaped to an elongated triangle and mounted as a cantilever so that a cylindrical curvature is obtained with a single micrometer screw; thus, the focus distance can be purposely adjusted. With a crystal asymmetrically cut to (111) planes, the wavelength is tuneable from 0.7 to 3.5 A and the higher-order harmonics at the detector level are negligible for λ A (using DCI synchrotron radiation). The optical bench is mounted on a heavy frame with 2 θ rotation. This set-up has been used for small angle scattering and protein crystallography. For this application, actual gain is up to 20 over a 2.4 kW Elliott GX6 rotating anode tube (Ni filtered CuKα radiation), with high spatial resolution and improved S N .