TY - JOUR A1 - Probst, Anne-Catherine A1 - Stollenwerk, Manfred A1 - Emmerich, Florian A1 - Büttner, Andre A1 - Zeising, Sebastian A1 - Stadtmüller, Johannes A1 - Riethmüller, Franziska A1 - Stehlikova, Veronika A1 - Mingwu, Wen A1 - Proserpio, Laura A1 - Damm, Christine A1 - Rellinghaus, Bernd A1 - Döhring, Thorsten T1 - Influence of sputtering pressure on the nanostructure and the X-ray reflectivity of iridium coatings JF - Surface and Coatings Technology N2 - 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. KW - Iridium KW - sputtering KW - microstructure KW - coating KW - X-ray KW - Iridium KW - Röntgenteleskop Y1 - 2017 UR - https://doi.org/10.1016/j.surfcoat.2017.10.062 SN - 0257-8972 VL - 2017 IS - 343 SP - 101 EP - 107 ER - TY - JOUR A1 - Probst, Anne-Catherine A1 - Begou, Thomas A1 - Döhring, Thorsten A1 - Zeising, Sebastian A1 - Stollenwerk, Manfred A1 - Stadtmüller, Johannes A1 - Emmerich, Florian A1 - Lumeau, Julien ED - Publishing OSA, T1 - Coating stress analysis and compensation for iridium-based x-ray mirrors JF - Applied Optics N2 - Iridium-based coatings for mirrors of x-ray telescopes are studied. In particular, stress-induced deformation is characterized and shown to be compressive and equal to −1786  MPa. Two methods for stress compensation are then studied. One relies on the deposition of silica on the back surface of the substrate and a second one relies on the deposition of a chromium sublayer. Advantages and drawbacks of each of these techniques are presented. KW - iridium KW - coating stress KW - X-ray KW - mirror KW - astronomy KW - Röntgenteleskop KW - Iridium KW - Spiegelteleskop Y1 - 2018 UR - https://doi.org/10.1364/AO.57.008775 VL - 2018 IS - 57 (29) SP - 8775 EP - 8779 ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stadtmüller, Johannes A1 - Stollenwerk, Manfred A1 - Cotroneo, Vincenzo A1 - Pareschi, Giovanni A1 - Gibertini, Eugenio A1 - Magagnin, Luca T1 - Low-density coatings for enhanced X-ray reflectivity of astronomical telescope mirrors T2 - DGaO Proceedings N2 - High reflectivity grazing incidence mirrors of astronomical X-ray telescopes are usually coated with thin layers of iridium, gold, or platinum. Due to a series of absorption edges, these noble metals have low reflectivity in the 2 - 4 keV band. We present the development of innovative material combinations using chromium and an additional layer of polydopamine for enhanced reflectivity X-ray coatings. KW - Dopamin KW - Iridium KW - mirror KW - coating KW - X-ray KW - Röntgenteleskop Y1 - 2021 UR - https://www.dgao-proceedings.de/download/122/122_p3.pdf SN - 1614-8436 VL - 2021 IS - 122 SP - 1 EP - 2 PB - DGaO ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Stadtmüller, Johannes A1 - Marsikova, Veronika A1 - Hudec, Rene A1 - Flachs, Dennis A1 - Burwitz, Vadim A1 - Hartner, Gisela A1 - Rukdee, Surangkhana A1 - Müller, Thomas A1 - Schmidt, Thomas A1 - Inneman, Adolf A1 - Klementova, Mariana A1 - Zeising, Sebastian A1 - Langmeier, Andreas T1 - Lobster eye type X-ray telescope with chromium-iridium coated tri-layer mirrors T2 - Proceedings of SPIE N2 - For space-born astronomical X-ray telescopes, iridium-based reflective layer systems are known as highly effective mirrors coatings. During the recent years, Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague jointly developed stress compensated chromium-iridium coatings for this application. To overcome the disturbing reflectivity reduction of the iridium absorption edge around 2 keV photon energy, thin overcoat layers of chromium were applied in addition. Now a prototype of a wide-field, imaging X-ray telescope of Lobster Eye type is assembled at the company RIGAKU. For this purpose a small series of 34 mirrors based on 100 x 50 mm semiconductor grade silicon substrates has been coated at Aschaffenburg University. The applied tri-layer system consists of a stack of 40 nm chromium, which act as adhesive layer and compensates layer stress, a 30 nm iridium thick reflective layer, and an additional overcoat layer of 6 nm chromium. This layer system have been analysed by AFM and TEM images. The mirrors are assembled into an aluminium frame to build a 2D Lobster Eye type telescope. The designed focal length of this wide field X-ray telescope is two meter. To study the performance of the tri-layer coating system, a twin LE telescope with convenient gold coatings was manufactured also. Performance measurements of both telescopes and under same conditions are planned at the PANTER test facility at the Max-Planck Institute for Extraterrestrial Physics. First experimental results, their comparison with theoretical simulations and the comparison between both models will be presented in this contribution. KW - telescope KW - Lobster Eye KW - X-ray KW - mirror KW - iridium KW - Röntgenteleskop KW - Röntgenspiegel Y1 - 2021 U6 - https://doi.org/https://doi.org/10.1117/12.2589266 VL - 2021 IS - 11776 SP - 1177605-1 EP - 1177605-8 PB - SPIE ER - TY - CHAP A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Stadtmüller, Johannes A1 - Zeising, Sebastian A1 - Flachs, Dennis A1 - Stehlikova, Veronika A1 - Burwitz, Vadim A1 - Krumrey, Michael K. A1 - Cotroneo, Vincenzo A1 - Klementova, Mariana T1 - Characterisation of X-ray mirrors based on chromium-iridium tri-layer coatings T2 - Proceedings of SPIE N2 - Iridium-based layer systems are highly effective mirror coatings for space-born X-ray telescopes. During the recent years, Aschaffenburg University of Applied Sciences and its partners developed stress compensated chromium-iridium coatings for such astronomical applications, using chromium as an adhesive layer between iridium reflective layer and mirror substrate. However, there was room for improvement: To overcome the disturbing reflectivity reduction of the iridium absorption edge around 2 keV photon energy, thin overcoat layers of chromium are applied in addition now. This layer system has been analyzed by atomic force microscopy and transmission electron microscopy images. Furthermore, the reflectivity of such innovative X-ray mirrors based on chromium-iridium tri-layer coatings was recently measured at PTB's four-crystal monochromator beamline at the synchrotron radiation facility BESSY II. The experimental results, obtained for photon energies between 1.9 keV and 11 keV at two grazing incidence angles (0.6 degree and 0.9 degree) and their comparison with corresponding simulations are presented in this contribution. When compared to simulations of pure iridium coatings, a significantly higher reflectivity was achieved especially in the soft X-ray regime between 2 keV and 4 keV. Such chromium-iridium tri-layer coatings have high potential to increase the effective area for X-ray telescopes in Lobster Eye Design, for Wolter-I type X-ray optics, and for silicon pore optics as considered for the ATHENA telescope of the European Space Agency. KW - iridium KW - mirror KW - X-ray KW - coating KW - telescope KW - Röntgenspiegel KW - Röntgenteleskop KW - Iridium Y1 - 2021 U6 - https://doi.org/https://doi.org/10.1117/12.2592551 VL - 2021 IS - 11776 SP - 1177607-1 EP - 11776076 PB - SPIE ER -