Development of a two-dimensionally tunable focusing monochromator for protein crystallography at high-energy...

A two-dimensionally tunable focusing monochromator has been developed for protein crystallography at high-energy undulator beamlines of third-generation synchrotron radiation facilities. This monochromator consists of a silicon wafer fabricated with an oblique-cut angle between the Bragg net plane and the crystal surface, and adhered onto a table-like copper block. The radii of curvatures are altered independently in two directions by expanding the spaces between the table legs. The versatilities of the meridional and sagittal curvatures were confirmed by X-ray experiments and three-dimensional shape measurements, respectively. The two-dimensional focusing ability was demonstrated using high-energy X-rays of 37.7 keV emitted from a bending-magnet source at the Photon Factory. A quasi-isotropic profile of converged X-rays was achieved near the focal position. The apparent gain of photon flux was 21. As a result of these excellent monochromator characteristics, a diffraction pattern of a hen egg-white lysozyme crystal was successfully obtained using high-energy X-rays.