The Physikalisch-Technische Bundesanstalt (PTB) has used synchrotron radiation for the characterization of optics and
detectors for astrophysical X-ray telescopes for more than 20 years. At a dedicated beamline at BESSY II, a
monochromatic pencil beam is used by ESA and cosine Research since the end of 2005 for the characterization of novel
silicon pore optics, currently under development for the International X-ray Observatory (IXO). At this beamline, a
photon energy of 2.8 keV is selected by a Si channel-cut monochromator. Two apertures at distances of 12.2 m and
30.5 m from the dipole source form a pencil beam with a typical diameter of 100 μm and a divergence below 1". The
optics to be investigated is placed in a vacuum chamber on a hexapod, the angular positioning is controlled by means of
autocollimators to below 1". The reflected beam is registered at 5 m distance from the optics with a CCD-based camera
system.
This contribution presents design and performance of the upgrade of this beamline to cope with the updated design for
IXO. The distance between optics and detector can now be 20 m. For double reflection from an X-ray Optical Unit
(XOU) and incidence angles up to 1.4°, this corresponds to a vertical translation of the camera by 2 m. To achieve high
reflectance at this angle even with uncoated silicon, a lower photon energy of 1 keV is available from a pair of W/B4C
multilayers. For coated optics, a high energy option can provide a pencil beam of 7.6 keV radiation.
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