FUNDAMENTAL DESIGN OF THE HIGH-ENERGY UNDULATOR PILOT BEAMLINE FOR MACROMOLECULAR CRYSTALLOGRAPHY AT THE SPRING-8

The SPring-8 project team adopted our proposal for public beamline as one of two pilot beamlines for standardizing the beamline elements. The light source of this beamline is an in-vacuum-type undulator of magnetic periodicity of 3.2 cm, which emits highly brilliant x rays in a wide energy range between 9 and 38 keV. The highest power emitted from the light source is 5 kW. The corresponding power density is 300 kW/mrad2. To handle the tremendous power density, grazing incidence diffraction with variable glancing angle will be used for the first crystal of a fixed-exit double-crystal monochromator. To focus the high energy x rays up to 38 keV, two supermirrors (Ovonic Synthetic Materials Co.) will be installed in vertical and horizontal directions independently to get a quasi-isotropic and small beam profile at a focal position. In the experimental station, the sample crystals will be mounted on the κ-type goniostat, and the Weissenberg photographs will be recorded by on-line mode on an imaging plate detector of high-speed readout. Based on the excellent performance of the beamline, the routine structure determination of macromolecules will become available by using the newly constructed software system corresponding to the multiple isomorphous replacement technique with optimized anomalous scattering. The structure analyses with smaller sample crystals than that usually used and with the specimen of the larger unit cell will also become possible. © 1995 American Institute of Physics.