ZERODUR mandrels for the next generation of X-ray telescopes

Following the actual X-ray satellites XMM-NEWTON and CHANDRA future missions are in discussion. ESA is planning the XEUS-satellite and NASA the CONSTELLATION-X mission. The increasing effective areas of the telescopes require nested thin-walled mirrors of large diameters. For the mass production of segmented shells the techniques of nickel electroforming and of epoxy replication are in evaluation. In both cases ZERODUR glass ceramic was chosen for the replication mandrels due to its high thermal stability and its proven ability to be polished to excellent surface qualities. SCHOTT GLAS has produced pre-shaped prototypes of a-spherical replication mandrels. The final polishing is done at CARL ZEISS, who is also the prime contractor for the finished mandrels. A demonstration mandrel for XEUS has been finished in 2000; the first prototype mandrel for CONSTELLATION-X will be delivered this year. It has been demonstrated that high precision mandrels can be produced with the required accuracy. Thereby ZERODUR is developing from a mirror substrate material (ROSAT, CHANDRA) to the preferred material of mandrels for the replication of X-ray mirrors. This demonstrates the broad variety of applications for this zero expansion glass ceramics.