Characterization of a Hard X-ray Telescope at Synchrotron Facility SPring-8

Space-borne astronomical instruments require extensive characterization on the ground before launch. In the hard X-ray region however, it is difficult for a laboratory-based beamline using a conventional X-ray source to provide a capability sufficient for pre-flight high-precision calibration. In this paper, we describe an experiment to characterize a hard X-ray telescope at a synchrotron facility, mainly on the basis of experimental setup and examples of measured results. We have developed hard X-ray telescopes consisting of Wolter-I grazing incidence optics and platinum-carbon multilayer supermirror coatings. The telescopes have been characterized at the synchrotron facility SPring-8 beamline BL20B2. The measurements at BL20B2 have great advantages such as extremely high flux, large-sized and less-divergent beam, and monochromatic beam covering the entire hard X-ray region from 8 to over 100 keV. The telescope was illuminated by monochromatic hard X-rays, and the focused image was measured by high resolution hard X-ray imagers. The entire telescope aperture was mapped by a small beam, and the effective area and the point spread function were obtained as well as local optical properties for further diagnostics of the characteristics of the telescope.