ESA Science & Technology - Silicon Pore Optics: novel lightweight high-resolution X-ray optics

Publication date: 01 January 2004

Authors: Marco Beijersbergen, Stefan Kraft, Ramses Guenther, Arjan Mieremet, Maximilien Collon, Marcos Bavdaz, David Lumb, Anthony Peacock

The next generation astronomical X-ray telescopes (e.g. XEUS) require extremely large collecting area (10 m²) in combination with good angular resolution (5 arcsec). The existing technologies such as polished glass, nickel electroforming and foil optics would lead to excessively heavy and expensive optics, and/or are not able to produce the required large area or resolution. We have developed an entirely novel technology for producing X-ray optics which results in very light, stiff and modular optics which can be assembled into almost arbitrarily large apertures, and which are perfectly suited for XEUS. The technology makes use of commercially available silicon wafers from the semiconductor industry. The latest generation silicon wafers have a surface roughness that is sufficiently low for X-ray reflection, are planparallel to better than a micrometer, have almost perfect mechanical properties and are considerably cheaper than other high-quality optical materials. The wafers are bent into an accurate cone and assembled to form a light and stiff pore structure with pores of the order of a millimeter. The resulting modules form a small segment of a Wolter-I optic, and are easily assembled into an optic with large collecting area. We present the production principle of these silicon pore optics, the facilities that have been set up to produce these modules and experimental results showing the excellent performance of the first modules that have been produced. With further improvement we expect to be able to match the XEUS requirements for imaging resolution and mass.