Progress In The Indirect Slumping Technology Development At Mpe For Lightweight X-Ray Optics

Large X-ray telescopes for future observatories need to combine a big collecting area, meaning thin mirrors with large diameter, with good angular resolution. Structures have to be stiff enough to guarantee the correct profiles and positioning of such mirrors. Due to the mass limits of the launching rockets, lightweight materials and configurations are required.. The Slumped Glass Optic (SGO) group of the Max-Planck-Institute for Extraterrestrial physics (MPE) is developing the indirect slumping technology to comply with this need. This technique foresees the shaping at high temperature of thin glass foils, originally flat, to Wolter I design X-ray mirror segments, by using suitable moulds. During the thermal cycle inside an electrical oven the glass viscosity is such reduced that it allows its bending onto the mould. So the mould's shape is replicated while still maintaining the original micro-roughness of the glass on the non-contact side that is of fundamental importance for X-ray reflections. This replication process is particularly suitable for the manufacturing of several identical optical elements, which must successively be coated with the necessary reflective layer and then aligned and integrated into supporting structures. Numerous aspects of the technology have been studied in the past, such as the selection of mould and glass materials, and the corresponding optimization of the thermal cycle parameters. During the last year, we focused on different process set-ups. The current results and status of activities will be presented in the paper.