@inproceedings{DoehringProbstStollenwerketal.2016, author = {D{\"o}hring, Thorsten and Probst, Anne-Catherine and Stollenwerk, Manfred and Wen, Mingwu and Proserpio, Laura}, title = {Development of low-stress Iridium coatings for astronomical x-ray mirrors}, series = {Proceedings of SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray}, volume = {2016}, booktitle = {Proceedings of SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray}, number = {9905}, editor = {den Herder, Jan-Willem A. and Takahashi, Tadayuki and Bautz, Marshall}, doi = {10.1117/12.2232074}, pages = {99056S-1 -- 99056S-7}, year = {2016}, abstract = {Previously used mirror technologies are not suitable for the challenging needs of future X-ray telescopes. This is why the required high precision mirror manufacturing triggers new technical developments around the world. Some aspects of X-ray mirrors production are studied within the interdisciplinary project INTRAAST, a German acronym for "industry transfer of astronomical mirror technologies". The project is embedded in a cooperation of Aschaffenburg University of Applied Sciences and the Max-Planck-Institute for extraterrestrial Physics. One important task is the development of low-stress Iridium coatings for X-ray mirrors based on slumped thin glass substrates. The surface figure of the glass substrates is measured before and after the coating process by optical methods. Correlating the surface shape deformation to the parameters of coating deposition, here especially to the Argon sputtering pressure, allows for an optimization of the process. The sputtering parameters also have an influence on the coating layer density and on the micro-roughness of the coatings, influencing their X-ray reflection properties. Unfortunately the optimum coating process parameters seem to be contrarious: low Argon pressure resulted in better micro-roughness and higher density, whereas higher pressure leads to lower coating stress. Therefore additional measures like intermediate coating layers and temperature treatment will be considered for further optimization. The technical approach for the low-stress Iridium coating development, the experimental equipment, and the obtained first experimental results are presented within this paper.}, subject = {R{\"o}ntgenspiegel}, language = {en} } @inproceedings{ProbstDoehringStollenwerketal.2017, author = {Probst, Anne-Catherine and D{\"o}hring, Thorsten and Stollenwerk, Manfred and Mingwu, Wen and Proserpio, Laura}, title = {Iridium coatings for space based x-ray optics}, series = {Proceedings of SPIE}, volume = {2017}, booktitle = {Proceedings of SPIE}, number = {10562}, editor = {Cugny, Bruno and Karafolas, Nikos and Sodnik, Zoran}, doi = {10.1117/12.2296167}, pages = {105621E-01 -- 105621E-09}, year = {2017}, abstract = {Future investigations of astronomical X-ray sources require light weight telescope systems with large collecting areas and good angular resolution. The Wolter I type telescope design offers a suitable possibility for obtaining performant X-ray mirrors with high collecting areas. The technology based on replicated slumped glass optics using thin glasses thereby provides the opportunity to fulfil the light weight and mass production requirements. In NASA's telescope NuSTAR this technology has been proven as advantageous compared to previous systems. Coating thin glasses with iridium, gold or platinum enhances the reflectivity of X-ray mirrors.}, subject = {Iridium}, language = {en} } @article{StehlikovaProbstNentvichetal.2018, author = {Stehlikova, Veronika and Probst, Anne-Catherine and Nentvich, Ondrej and Urban, Martin and Sieger, Ladislav and D{\"o}hring, Thorsten and Hudec, Ren{\´e}}, title = {Study of multiple layers coatings for X-ray mirrors}, series = {Contributions of the Astronomical Observatory Skalnat{\´e} Pleso}, volume = {2018}, journal = {Contributions of the Astronomical Observatory Skalnat{\´e} Pleso}, number = {48}, editor = {Skopal, August{\´i}n}, pages = {488 -- 497}, year = {2018}, abstract = {This paper focuses on a theoretical background that motivated the experimental campaign of multiple layer coatings of X-ray mirrors, and the first results of the testing of the prepared samples. Simulations of the use of different overcoats were performed in order to improve the reflectivity of thin iridium coatings designed for X-ray optics effective in the energy up to 10 keV. Samples based on these simulations were prepared and are being tested for the properties that influence the X-ray optical performance, such as layer homogeneity, density and surface micro-roughness. Further the topic of the coating stress was addressed, as it is an issue in case of thin, lightweight X-ray mirrors and affects the time stability of layers. The discussion and preliminary results conclude our contribution.}, subject = {R{\"o}ntgenspiegel}, language = {en} } @inproceedings{StehlikovaUrbanNentvichetal.2017, author = {Stehlikova, Veronika and Urban, Martin and Nentvich, Ondrej and Inneman, Adolf and D{\"o}hring, Thorsten and Probst, Anne-Catherine}, title = {Study of lobster eye optics with iridium coated X-ray mirrors for a rocket experiment}, series = {Proceedings of the International Society for Optics and Photonics (SPIE)}, volume = {2017}, booktitle = {Proceedings of the International Society for Optics and Photonics (SPIE)}, number = {10235}, editor = {Hudec, Rene}, publisher = {SPIE International Society for Optics and Photonics}, address = {Bellingham WA}, organization = {Czech Technical University in Prague}, doi = {10.1117/12.2265769}, pages = {1023505-1 -- 1023505-7}, year = {2017}, abstract = {In the field of astronomical X-ray telescopes, different types of optics based on grazing incidence mirrors can be used. This contribution describes the special design of a lobster-eye optics in Schmidt's arrangement, which uses dual reflection to increase the collecting area. The individual mirrors of this wide-field telescope are made of at silicon wafers coated with reflecting iridium layers. This iridium coatings have some advantages compared to more common gold layers as is shown in corresponding simulations. The iridium coating process for the X-ray mirrors was developed within a cooperation of the Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague. Different mirror parameters essential for a proper function of the X-ray optics, like the surface microroughness and the problematic of a good adhesion quality of the coatings were studied. After integration of the individual mirrors into the final lobster-eye optics and the corresponding space qualification testing it is planned to fly the telescope in a recently proposed NASA rocket experiment.}, subject = {Iridium}, language = {en} } @inproceedings{DoehringProbstEmmerichetal.2017, author = {D{\"o}hring, Thorsten and Probst, Anne-Catherine and Emmerich, Florian and Stollenwerk, Manfred and Stehlikova, Veronika and Friedrich, Peter and Damm, Christine}, title = {Development of iridium coated X-ray mirrors for astronomical applications}, series = {Proceedings of the International Society for Optics and Photonics (SPIE)}, volume = {2017}, booktitle = {Proceedings of the International Society for Optics and Photonics (SPIE)}, number = {10399}, publisher = {SPIE}, doi = {10.1117/12.2273988}, pages = {103991C-1 -- 103991C-8}, year = {2017}, abstract = {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.}, subject = {Iridium}, language = {en} } @article{ProbstStollenwerkEmmerichetal.2017, author = {Probst, Anne-Catherine and Stollenwerk, Manfred and Emmerich, Florian and B{\"u}ttner, Andre and Zeising, Sebastian and Stadtm{\"u}ller, Johannes and Riethm{\"u}ller, Franziska and Stehlikova, Veronika and Mingwu, Wen and Proserpio, Laura and Damm, Christine and Rellinghaus, Bernd and D{\"o}hring, Thorsten}, title = {Influence of sputtering pressure on the nanostructure and the X-ray reflectivity of iridium coatings}, series = {Surface and Coatings Technology}, volume = {2017}, journal = {Surface and Coatings Technology}, number = {343}, issn = {0257-8972}, pages = {101 -- 107}, year = {2017}, abstract = {Reflective mirror coatings made of iridium are used in X-ray telescopes of the Chandra X-ray Observatory (CXO) launched in 1999 by the National Aeronautics and Space Administration (NASA) to investigate astronomical sources at photon energies below 10. keV. These coatings were produced in a DC magnetron sputtering process and have so far proven their suitability for space-based applications. We are considering in the present paper the processing of thin iridium films for lightweight telescopes using the radio frequency magnetron sputtering technique with an oblique angle deposition. The coating development presented here is focused on the influence of total sputtering pressure on film properties as well as on its impact on the mirror's performance. Characterisation methods such as X-ray diffractometry, X-ray reflectometry, atomic force microscopy and transmission electron microscopy have been used. Correlations between morphology, density, surface micro-roughness, crystal structure of the iridium layer and the expected reflectivity of the X-ray mirror are described and discussed.}, subject = {Iridium}, language = {en} }