Focusing x-ray beamline for macromolecular crystallography at the Photon Factory

Abstract

A beamline (BL 6A) for x‐ray crystallography mainly utilizing photographic methods was designed and constructed at the Photon Factory. A focusing mirror was installed at the beamline in order to obtain a beam with high photon flux while eliminating higher energy x rays in the beam. The mirror chamber located at 11.8 m from the source point is maintained in a high vacuum so as to keep the mirror surface clean. It accommodates a 1.3‐m‐long steel holder on which a mirror block is mounted. Two types of mirror blocks, plane and cylindrical ones of fused quartz, are prepared for alternative use. A radiation shielding hutch placed at around 15 m from the source is sufficiently large for installing a monochromator and various types of cameras. When the plane mirror was bent vertically, the size of the focused beam at 15.3 m was reduced to about 0.18 mm in the vertical direction. By the use of focused x rays, preliminary Laue diffraction experiments were carried out on protein crystals. Good quality diffraction patterns recorded on imaging plates were obtained by exposure of several milliseconds.