Silicon pore optics for astrophysical x-ray missions

Silicon pore X-ray optics enable future astrophysical science missions that require imaging X-ray telescopes with an angular resolution better than 5" and an effective area of several square meters at photon energies of 1 keV. The characteristics of the latest generation of these very light, stiff and modular X-ray optics, termed high-performance pore optics (HPO), are discussed in this paper. HPOs with several tens of silicon plates have been assembled in the course of an ESA technology development program, by bending the plates into accurate shape and directly bonding them on top of each other. Test plates have been coated to enhance the reflectivity of the optic. Several HPOs have been integrated into modules in Wolter-I configuration, some of them with properly wedged plates. Their performance has been measured during test campaigns at X-ray testing facilities using pencil beam and full beam illumination. Pencil beam measurements at BESSY-II yield information on the production process with high spatial resolution and without the need for image deconvolution. It will be shown in this paper that the full beam results on the figure of the optics can be predicted from the pencil beam data. Full beam illumination at PANTER, besides yielding integrated information on the performance of the optic, delivers also unique data on the large angle scattering properties of the system. Experimental results including reflectometry and surface roughness measurements are presented and discussed in this paper.