International Conference on Space Optics — ICSO 2006 Noordwijk , Netherlands 27 – 30 June 2006 X-ray pore optic developments

In support of future x-ray telescopes ESA is developing new optics for the x-ray regime. To date, mass and volume have made x-ray imaging technology prohibitive to planetary remote sensing imaging missions. And although highly successful, the mirror technology used on ESA’s XMM-Newton is not sufficient for future, large, x-ray observatories, since physical limits on the mirror packing density mean that aperture size becomes prohibitive. To reduce telescope mass and volume the packing density of mirror shells must be reduced, whilst maintaining alignment and rigidity. Structures can also benefit from a modular optic arrangement. Pore optics are shown to meet these requirements. This paper will discuss two pore optic technologies under development, with examples of results from measurement campaigns on samples. One activity has centred on the use of coated, silicon wafers, patterned with ribs, that are integrated onto a mandrel whose form has been polished to the required shape. The wafers follow the shape precisely, forming pore sizes in the sub-mm region. Individual stacks of mirrors can be manufactured without risk to, or dependency on, each other and aligned in a structure from which they can also be removed without hazard. A breadboard is currently being built to demonstrate this technology. A second activity centres on glass pore optics. However an adaptation of micro channel plate technology to form square pores has resulted in a monolithic material that can be slumped into an optic form. Alignment and coating of two such plates produces an x-ray focusing optic. A breadboard 20cm aperture optic is currently being built. 1. BACKGROUND In the energy regime of interest, 0.1 to 10 keV, only grazing incidence reflections can be exploited to focus an x-ray image. In the design of a Wolter I optic the two grazing incidence reflections (around 1 ), from a parabolic then a hyperbolic surface, produce a real image of the x-ray source. In order to increase the effective area of an x-ray optic, the aperture must be packed densely with concentric shells of grazing incidence mirrors, traditionally formed from glass or nickel plates, stacked in a nested structure. To increase effective area the mirror shells must be as thin as possible, which consequentially makes them fragile, prone to distortion, difficult to align and mount. Shell mounts also constrain the inter-plate separation that can be achieved. Fig. 1-1: Conical approximation of the parabolic and hyperbolic sections of a Wolter I optic to focus x-rays. ICSO 2006 International Conference on Space Optics Noordwijk, Netherlands