TY - CHAP A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine A1 - Stollenwerk, Manfred A1 - Wen, Mingwu A1 - Proserpio, Laura ED - den Herder, Jan-Willem A. ED - Takahashi, Tadayuki ED - Bautz, Marshall T1 - Development of low-stress Iridium coatings for astronomical x-ray mirrors T2 - Proceedings of SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray N2 - 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. KW - telescope KW - mirror KW - coating KW - iridium KW - astronomy KW - Röntgenspiegel KW - Iridium KW - Beschichtung Y1 - 2016 U6 - https://doi.org/10.1117/12.2232074 VL - 2016 IS - 9905 SP - 99056S-1 EP - 99056S-7 ER - TY - CHAP A1 - Probst, Anne-Catherine A1 - Döhring, Thorsten A1 - Salmaso, Bianca A1 - Proserpio, Laura T1 - Shape measurement of thin glass substrates for X-ray mirrors: cross calibration of different equipments T2 - Proceedings of European Optical Society Annual Meeting 2016 N2 - To predict the angular resolution of future X-ray telescopes combined from thermally formed thin glass mirror segments, submicron accuracy is required on the shape measurements of the individual mirror substrates. A dedicated cross-calibration campaign using instruments of different European research institutions is presented. KW - X-ray KW - mirror KW - calibration KW - glass KW - Röntgenspiegel KW - Kalibrieren Y1 - 2016 VL - 2016 PB - European Optical Society ER - TY - CHAP A1 - Probst, Anne-Catherine A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred A1 - Mingwu, Wen A1 - Proserpio, Laura ED - Cugny, Bruno ED - Karafolas, Nikos ED - Sodnik, Zoran T1 - Iridium coatings for space based x-ray optics T2 - Proceedings of SPIE N2 - 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. KW - Iridium KW - coating KW - X-ray KW - astronomy KW - mirror KW - Iridium KW - Spiegelteleskop KW - Röntgenastronomie Y1 - 2017 U6 - https://doi.org/10.1117/12.2296167 VL - 2017 IS - 10562 SP - 105621E-01 EP - 105621E-09 ER - TY - JOUR A1 - Stehlikova, Veronika A1 - Probst, Anne-Catherine A1 - Nentvich, Ondrej A1 - Urban, Martin A1 - Sieger, Ladislav A1 - Döhring, Thorsten A1 - Hudec, René ED - Skopal, Augustín T1 - Study of multiple layers coatings for X–ray mirrors JF - Contributions of the Astronomical Observatory Skalnaté Pleso N2 - 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. KW - X-ray KW - optics KW - coating KW - reflectivity KW - iridium KW - Röntgenspiegel KW - Iridium Y1 - 3018 UR - https://www.ta3.sk/caosp/Eedition/Abstracts/2018/Vol_48/No_3/pp488-497_abstract.html VL - 2018 IS - 48 SP - 488 EP - 497 ER - TY - JOUR A1 - Büttner, Andre A1 - Probst, Anne-Catherine A1 - Emmerich, Florian A1 - Damm, Christine A1 - Rellinghaus, Bernd A1 - Döhring, Thorsten A1 - Stollenwerk, Manfred T1 - Influence of Sputtering Pressure on the Microstructure and Layer Properties of Iridium Thin Films JF - Thin Solid Films N2 - Iridium layers with low stress, high density, and low surface roughness find widespread use in different high-technology applications. This paper presents a study of the influence of the sputtering pressure on the properties of iridium thin films and of its effect on the substrate surface microstructure. We analysed the dependence of the microstructure, crystalline structure, electrical resistivity, and deposition rate on the sputtering pressure and surface defects of the substrate. For the latter, plasma etching of the substrate was performed for different processing times and its effect on the surface roughness of substrates and, subsequently, on the grown iridium films, was examined. The sputtering pressure and the substrate plasma etching time both had a strong influence on the microstructure and surface roughness. These microstructural changes are in good agreement with the tendency described in the Thornton Structure-Zone Model for different sputtering pressures and the microstructure phase map of Alvarez. The electrical resistivity, deposition rate, and crystalline structure were highly dependent on the sputtering pressure. KW - Iridium KW - microstructure KW - TEM KW - sputtering KW - thin films KW - Iridium KW - Dünne Schicht Y1 - 2018 UR - https://doi.org/10.1016/j.tsf.2018.06.056 SN - 0040-6090 VL - 2018 IS - 662 SP - 41 EP - 46 ER - TY - CHAP A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine A1 - Stollenwerk, Manfred A1 - Emmerich, Florian A1 - Stehlíková, Veronika A1 - Inneman, Adolf ED - Hudec, René ED - Pina, Ladislav T1 - Prototyping iridium coated mirrors for X-ray astronomy T2 - Proceedings of the International Society for Optics and Photonics N2 - X-ray astronomy uses space-based telescopes to overcome the disturbing absorption of the Earth´s atmosphere. The telescope mirrors are operating at grazing incidence angles and are coated with thin metal films of high-Z materials to get sufficient reflectivity for the high-energy radiation to be observed. In addition the optical payload needs to be light-weighted for launcher mass constrains. Within the project JEUMICO, an acronym for “Joint European Mirror Competence”, the Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague started a collaboration to develop mirrors for X-ray telescopes. The X-ray telescopes currently developed within this Bavarian- Czech project are of Lobster eye type optical design. Corresponding mirror segments use substrates of flat silicon wafers which are coated with thin iridium films, as this material is promising high reflectivity in the X-ray range of interest. The deposition of the iridium films is based on a magnetron sputtering process. Sputtering with different parameters, especially by variation of the argon gas pressure, leads to iridium films with different properties. In addition to investigations of the uncoated mirror substrates the achieved surface roughness has been studied. Occasional delamination of the iridium films due to high stress levels is prevented by chromium sublayers. Thereby the sputtering parameters are optimized in the context of the expected reflectivity of the coated X-ray mirrors. In near future measurements of the assembled mirror modules optical performances are planned at an X-ray test facility. KW - X-ray KW - iridium KW - mirror KW - lightweight optic KW - Lobster Eye KW - Iridium KW - Röntgenastronomie KW - Spiegelteleskop Y1 - 2017 U6 - https://doi.org/10.1117/12.2265931 VL - 2017 IS - 10235 SP - 1023504-1 EP - 1023504-8 PB - SPIE International Society for Optics and Photonics CY - Bellingham WA ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Urban, Martin A1 - Nentvich, Ondrej A1 - Inneman, Adolf A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine ED - Hudec, Rene T1 - Study of lobster eye optics with iridium coated X-ray mirrors for a rocket experiment T2 - Proceedings of the International Society for Optics and Photonics (SPIE) N2 - 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. KW - Lobster Eye KW - Iridium KW - mirror KW - coating KW - Iridium KW - Spiegelteleskop KW - optische Schicht Y1 - 2017 U6 - https://doi.org/10.1117/12.2265769 VL - 2017 IS - 10235 SP - 1023505-1 EP - 1023505-7 PB - SPIE International Society for Optics and Photonics CY - Bellingham WA ER - TY - CHAP A1 - Probst, Anne-Catherine A1 - Döhring, Thorsten A1 - Zeising, Sebastian A1 - Salmaso, Bianca A1 - Stollenwerk, Manfred A1 - Proserpio, Laura T1 - Challenges in metrology of mirror segments for X-ray telescopes T2 - Proceedings of the 8th High Level Expert Meeting Asphere Metrology N2 - High angular resolution, large collecting area and reduced weight per unit area are required for astronomical X-ray telescopes of the next generation observatories. New technologies for processing X-ray mirrors are under development to fulfill these needs. One option is to realize a Wolter I type telescope constituted of several hundred nested thin and light-weight X-ray mirror segments. The individual mirror segments need to be coated with an about 100 nm thick film of a high-reflective material to enhance the reflectivity for X-rays. Thereby an accurate shape metrology of the segments is necessary to predict the angular resolution of the astronomical telescope as well as to control the development process of X-ray mirrors. We present the challenges in shape measurements of thin glasses used to control the coating process and first experimental results about the repeatability of the measurements. KW - metrology KW - mirror KW - telescope KW - Spiegelteleskop Y1 - 2017 UR - http://www.upob.de/index.php?option=com_phocadownload&view=category&download=198:8th-high-level-expert-meeting-2017-detailed-programme&id=21:upob-high-level-expert-meetings&Itemid=70 VL - 2017 IS - 8 PB - UTOB e.V. CY - Braunschweig ER - TY - CHAP A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine A1 - Emmerich, Florian A1 - Stollenwerk, Manfred A1 - Stehlikova, Veronika A1 - Friedrich, Peter A1 - Damm, Christine T1 - Development of iridium coated X-ray mirrors for astronomical applications T2 - Proceedings of the International Society for Optics and Photonics (SPIE) N2 - 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. KW - X-ray KW - telescope KW - mirror KW - iridium KW - coating KW - Iridium KW - Röntgenteleskop Y1 - 2017 U6 - https://doi.org/10.1117/12.2273988 VL - 2017 IS - 10399 SP - 103991C-1 EP - 103991C-8 PB - SPIE ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Proserpio, Laura A1 - Friedrich, Peter A1 - Madarasz, Emanuel A1 - Breunig, Elias A1 - Burwitz, Vadim A1 - Döhring, Thorsten A1 - Probst, Anne-Catherine T1 - Indirect glass slumping of grazing incidence mirror segments for lightweight x-ray telescopes T2 - Proceedings of the International Society for Optics and Photonics (SPIE) N2 - 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 veri� cation 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. KW - X-ray KW - iridium KW - telescope KW - slumping KW - glass KW - Iridium KW - Röntgenteleskop Y1 - 2017 U6 - https://doi.org/10.1117/12.2272671 VL - 2017 IS - 10399 SP - 103991Z-1 EP - 103991Z-7 PB - SPIE ER - TY - CHAP A1 - Stehlikova, Veronika A1 - Probst, Anne-Catherine A1 - Nentvich, Ondrej A1 - Urban, Martin A1 - Inneman, Adolf A1 - Sieger, Ladislav A1 - Marsikova, Veronika A1 - Döhring, Thorsten T1 - Development of iridium coated silicon X-ray mirrors for Lobster Eye astronomical telescopes T2 - Proceedings of EOSMOS 2017 N2 - In the field of X-ray astronomy different types of telescope optics based on grazing incidence mirrors can be used. This contribution presents a special design of a Lobster Eye wide-field telescope with mirrors based on flat silicon wafers and the task of coating such mirror substrates with reflective iridium layers. KW - X-ray KW - mirror KW - telescope KW - Lobster Eye KW - iridium KW - Iridium KW - Röntgenteleskop Y1 - 2017 VL - 2017 IS - EOSMOS 2017 SP - 1 EP - 2 PB - European Optical Society ER - 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 - Probst, Anne-Catherine A1 - Hitzinger, Hans A1 - Bochtler, Ulrich A1 - Wölfel, Maximilian A1 - Schmitt, Christoph ED - U.R.S.I. Landesausschuss in Deutschland e.V. 2021, T1 - High Frequency Power Amplifier for Wideband Wireless Communication Systems T2 - Proceedings of the 2021 Kleinheubach Conference N2 - Increasing data transmission rates and bandwidth both belong to the challenges of the development of high-performance wireless communication systems. Multi-channel communication systems commonly use several narrowband power amplifiers each one for a single communication channel. Lossy couplers are needed both to separate the different channels from each other at the amplifiers input and to combine the amplified signals on each channel at the output. This approach depicts a poor efficiency and is limited to a few number of channels since each channel duplication involves 3 dB losses due to couplers. Alternatively, broadband radio frequency power amplifiers ensuring the simultaneous transmission of several carriers on a wide frequency range contribute to increase the cost and resource efficiency of transceivers in wireless communication systems. Gain flatness, a high output power, and low power levels of second and third order harmonics are required on the whole operating frequency range of the power amplifier in multi-carrier communication systems since overtones will degrade the quality of the communication. The present work investigates the performances of a broadband push-pull power amplifier based on LDMOS transistors, the input matching network using a 8:1 transmission line transformer. For the first time investigations on harmonic distortions of the amplified signal when using a transformer with 8:1 impedance transformation ratio are presented. Characterisation of the power amplifiers performances is focused on gain flatness, output power, harmonic distortions and efficiency at 110 W. KW - LDMOS KW - broadband RF power amplifier KW - push-pull KW - transmission line transformer KW - harmonic distortion KW - Hochfrequenzverstärker KW - Leistungsverstärker KW - Kommunikationssystem Y1 - 2021 U6 - https://doi.org/10.23919/IEEECONF54431.2021.9598443 VL - 2021 ER - TY - CHAP A1 - Neumaier, Marcel A1 - Probst, Anne-Catherine A1 - Wölfel, Maximilian A1 - Bochtler, Ulrich T1 - Performance Analysis in a Digital TETRA-Simulcast System T2 - 2025 16th German Microwave Conference (GeMiC) N2 - In radio communication of mission-critical services, resilient solutions are strongly required to account for public safety. Additionally to the cellular network based on the professional mobile radio European standard TETRA, a digital TETRA-simulcast system is proposed as a redundant network to ensure area coverage in case of base station failure caused e.g. by disasters. This paper presents a preliminary study about network planning of a frequency-efficient digital TETRA-simulcast system to be physically deployed in a hilly region of Germany. Coverage as well as ray tracing analysis and channel modeling were performed by simulations and prove to be helpful tools for the systematic optimization of system performances, especially with regard to the control of intersymbol interference in overlapping zones. KW - digital radio KW - intersymbol interference KW - overlapping zones KW - quasi-synchronous transmission KW - TETRA KW - TETRA, Telekommunikation Y1 - 2025 ER - TY - CHAP A1 - Probst, Anne-Catherine A1 - Neumaier, Marcel A1 - Hufgard, Christopher A1 - Wölfel, Maximilian A1 - Schmitt, Christoph A1 - Bochtler, Ulrich T1 - Network Planning a Digital TETRA-Simulcast-System T2 - Kleinheubacher Tagung, Miltenberg, 23.09.2025 - 25.09.2025 KW - TETRA, Telekommunikation Y1 - 2025 ER -