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Previously used mirror technologies are not able to fulfil the requirements of future X-ray telescopes due to challenging requests from the scientific community. Consequently new technical approaches for X-ray mirror production are under development. In Europe the technical baseline for the planned X-ray observatory ATHENA is the radical new approach of silicon pore optics. NASA´s recently launched NuSTAR mission uses segmented mirrors shells made from thin bended glasses, successfully demonstrating the feasibility of the glass forming technology for X-ray mirrors. For risk mitigation also in Europe the hot slumping of thin glasses is being developed as an alternative technology for lightweight X-ray telescopes. The high precision mirror manufacturing requires challenging technical developments; several design trades and trend-setting decisions need to be made and are discussed within this paper. Some new technical and economic aspects of the intended glass mirror serial production are also studied within the recently started interdisciplinary project INTRAAST, an acronym for “industry transfer of astronomical mirror technologies”. The goal of the project, embedded in a cooperation of the Max-Planck-Institute for extraterrestrial Physics and the University of Applied Sciences Aschaffenburg, is to master the challenge of producing thin mirror shells for future X-ray telescopes. As a first project task the development of low stress coatings for thin glass mirror substrates have been started, the corresponding technical approach and first results are presented.
Future X-ray telescopes aim for large effective area within the given mass limits of the launcher. A promising method
is the hot shaping of thin glass sheets via a thermal slumping process. This paper presents the status and progress of
the indirect glass slumping technology developed at the Max-Planck-Institut for extraterrestrial Physics (MPE). Recent
developments in our research include the use of the mould material Cesic under vacuum, as well as the fabrication of a
high-precision slumping mould, which meets the requirements of large, high angular resolution missions like
ATHENA. We describe the way forward to optimise the slumping process on these materials, the force-free
integration concept and its progress, as well as the first test on reflective coating application.
Previously used mirror technologies are not able to fulfill the challenging
requirements of future X-ray telescopes. A promising new technology under
development is the hot slumping of thin glasses. Challenges, design trades and
first results are presented, including the thermal shaping process, the
development of low stress coatings and the mirror segments integration concept.
Studying astronomical objects in the X-ray regime, iridium-based layer systems are highly effective reflective
materials for telescopes mirrors. Aschaffenburg University and the Czech Technical University in Prague jointly developed stress compensated chromium-iridium coatings. To overcome the disturbing reflectivity reduction of the iridium absorption edge around 2 keV photon energy and improve general reflectivity at lower incident energies, thin overcoat layers of chromium have been applied in addition. Corresponding measurements at several X-ray lines have been performed on these samples at the PANTER test facility of the Max-Planck Institute for
extraterrestrial Physics. A part of the experimental results and their comparison with theoretical simulations
are presented in this contribution.
Future space-based X-ray observatories need to be very lightweight for launcher mass constraints. Therefore they will
use a reduced mirror thickness, which results in the additional requirement of low coating stress to avoid deformation of
the initial precisely shaped mirror substrates. Due to their excellent reflection properties iridium coatings are sometimes
applied for grazing incidence mirrors in astronomical X-ray telescopes. At Aschaffenburg University of Applied
Sciences the coating of thin iridium films by an RF-magnetron sputtering technique is under development. The work is
embedded in collaborations with the Max-Planck-Institute for Extraterrestrial Physics in Germany, the Czech Technical
University in Prague, the Osservatorio Astronomico di Brera in Italy, the German Leibniz Institute for Solid State and
Materials Research in Dresden, and the French Institute Fresnel. Sputtering with different parameters leads to iridium
films with different properties. The current work is focused on the microstructure of the iridium coatings to study the
influence of the substrate and of the argon gas pressure on the thin film growing process. Correlations between coating
density, surface micro-roughness, the crystalline structure of the iridium layers, and the expected reflectivity of the X-ray
mirror as well as coating stress effects are presented and discussed. The final goal of the project is to integrate the
produced prototype mirrors into an X-ray telescope module. On a longer timescale measurements of the mirror modules
optical performance are planned at the X-ray test facility PANTER.
Indirect glass slumping of grazing incidence mirror segments for lightweight x-ray telescopes
(2017)
The paper provides a description of recent progress in the development of lightweight, precision and highthroughput
grazing-incidence mirrors for X-ray astronomy made of glass. In particular, the indirect slumping
technology under investigation at the Max Planck Institute for Extraterrestrial Physics (MPE) is reviewed and
recent activities are presented together with the research approach. The glass slumping technique foresees
several steps: a thermal forming process using a suitable mould; a re
ective layer application; the alignment
and integration of mirror segments into a supporting structure; and the nal verication of prototype modules
using X-rays. Each step is considered at MPE, with the involvement of partner institutes and universities. The
last year of activities was mainly dedicated to the procurement of new moulds and to the application of Iridium
coating. The main results will be presented.
Im Rahmen einer bayerisch-tschechischen Kooperation entstanden zwei Röntgenteleskope, bestückt mit Gold- und Iridium-beschichteten Planspiegeln. Deren Charakterisierung erfolgte an der Röntgentestanlage PANTER, welche parallel auf die Teleskope einfallendes Sternenlicht simuliert. Die Teleskope haben eine Winkelauflösung von ca. 4 Bogenminuten und eine Brennweite von rund 2 Metern.