A general purpose sub-keV X-ray facility at the Stanford Synchrotron Radiation Laboratory

Abstract

We describe the design, implementation, and initial performance of the Beam Line VIII sub-keV X-ray facility at the Stanford Synchrotron Radiation Laboratory (SSRL). It consists of two general purpose beam lines branching from the same bending magnet on the Stanford Positron Electron Asymmetric Ring (SPEAR) storage ring. Each branch has appropriate focusing optics, featuring a cooled SiC first mirror, a grating monochromator with three interchangeable ion-etched gratings, a refocusing mirror, and filter and beam diagnostic sections, all operating in ultra-high vacuum. Each monochromator has sine-bar driven grating rotation, fixed in and out beam directions, and moveable exit slits. The toroidal grating monochromator (TGM) optical design is based on proven 6-m TGMs used by the National Synchrotron Light Source at Brookhaven National Laboratory and at the University of Wisconsin Synchrotron Radiation Center. Subtending 12 mrad of bending-magnet radiation, the high-throughput TGM branch provides continuously tunable radiation in the 8–190 eV range. The slit-to-slit spherical grating monochromator (SGM) optics are based on a new design featuring gratings of 55 m radius. Subtending effectively 4 mrad, the SGM branch covers the 60–1200 eV range with good resolution and intensity. These SR beam lines, along with our BL-X wiggler line, have been designed to serve the varied scientific research needs of a participating research team formed by the University of California and the Lawrence Livermore, Los Alamos, and Sandia National Laboratories.