Spectroscopy beamline at the Advanced Photon Source for the photon energy region from 0.5 to 3 keVa)

Abstract

Interest in the 0.5 to 3 keV, intermediate x-ray, energy region has recently intensified as this spectral region covers, among others, the important L and M edges of transition-metal and rare-earth magnetic materials, respectively. Third-generation synchrotron facilities with their inherent high brightness have the unique potential to cover this energy region with high-resolution, high-flux x-ray beams ideal for spectroscopic studies. A 5.5-cm-period, planar undulator to be installed on the 7-GeV Advanced Photon Source will produce a high brightness source of intermediate-energy x rays. The 0.5- to 3-keV spectroscopy beamline is based on the spherical grating monochromator design that has already been shown to yield high resolution and throughput in the soft-x-ray region, below 1 keV. The beamline has been designed to cover the entire region with a peak resolving power of 6000–10 000. Photon flux at the sample is calculated to be in the range from 1011 to 1013 photons/s into a spot size of 1 mm2. A refocusing mirror will be used to further demagnify the image size at a second experimental station. As a second phase to the spectroscopy program, an elliptically polarized insertion device will be used. The polarization preserving nature of the grazing incidence optical elements in the SGM is crucial to obtain x rays of well-defined polarization. The beamline layout, together with calculations of resolution, throughput, power loading, and high harmonic suppression, will be presented. The photoemission experimental end stations for the spectroscopy station will also be briefly described.