Production of the IXO glass segmented mirrors by hot slumping with pressure assistance: tests and results

The large dimensions of the future X-ray telescopes, with diameters ranging from 3.5 m and up to several meters, will require the adoption of segmented optics and hence the development of new technologies for their manufacturing. These technologies are based on lightweight materials and structures to comply with the mass constrains imposed by the launcher. The Astronomical Observatory of Brera (INAF-OAB) is involved in the development of a glass shaping technology for the production of grazing incidence segmented optics to be employed onboard the next generation of X-ray Observatories. This technique, named "Hot slumping technology with pressure", is based on the viscosity change of the glass with the temperature: by applying a suitable thermal cycle the viscosity of the glass is decreased enough to allow its slumping on a mould so to replicate its shape without significantly degrade its surface finishing. Following this replication approach, it is possible to obtain, with the same mould, a number of equal mirror segments that will be integrated and aligned in the telescope aperture so to create a mirror shell in configuration Wolter I. The entire study has been financed by ESA in the context of the International X-ray Observatory (IXO) mission with the aim of developing a back-up technology for the IXO mirror manufacturing. The study started in 2009 and it is scheduled to finish in 2012 with the production of representative module prototypes, named POC and XOU_BB. After a brief review of past results, this paper reports the latest advancement in the slumping of Schott glass D263 foils on Fused Silica and Zerodur moulds and its status as for summer 2011.