Diamond: a multilayer and sagittally focusing crystal as optical elements on the ID14/Quadriga-3 beamline at ESRF

Abstract

ID14/Quadriga at the ESRF is an undulator beamline dedicated to monochromatic macromolecular crystallography. Based on the Troika concept, this beamline has four simultaneously operating experimental stations: three side stations using thin diamond crystals, and an end station with a fast-scan double-crystal monochromator and a toroidal mirror. Two undulators with 23 mm and 42 mm periods and a minimum gap of 16 mm on a high-beta section provide a high brilliance X-ray beam between 6.2 keV and 35 keV. The principle of a multiple station beamline on an undulator X-ray source has been developed by Als-Nielsen. We use the (111) reflection of an (100) oriented diamond in asymmetric Laue mode or a (111) oriented diamond in Bragg mode in order to select a wavelength for the side station. Compared to the Troika beamline at ESRF, the optical system is more complex comprising a sagitally (vertically) focusing Ge(220) crystal and a multilayer on a bimorph bender for horizontal focusing. Independent focusing in the horizontal and vertical planes allows the use of both a Bragg-Bragg setup of the monochromator and a Laue-Bragg setup where difficulties arise from energy dispersion and focusing effects of the Laue crystal. The properties of a thin diamond crystal in asymmetric Laue mode are discussed. The optical system provides a high brilliance monochromatic X-ray beam with focal spotsize down to 0.2*0.06 mm 2 FWHM and a flux of about 1*10 11 photons/s at 13.2 keV. The opticl system of the first side branch, Quadriga-3, is operating since summer 1997.