@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{ProbstDoehringSalmasoetal.2016, author = {Probst, Anne-Catherine and D{\"o}hring, Thorsten and Salmaso, Bianca and Proserpio, Laura}, title = {Shape measurement of thin glass substrates for X-ray mirrors: cross calibration of different equipments}, series = {Proceedings of European Optical Society Annual Meeting 2016}, volume = {2016}, booktitle = {Proceedings of European Optical Society Annual Meeting 2016}, publisher = {European Optical Society}, organization = {Hochschule Aschaffenburg}, pages = {2}, year = {2016}, abstract = {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.}, subject = {R{\"o}ntgenspiegel}, language = {en} } @inproceedings{DoehringProbstZeising2018, author = {D{\"o}hring, Thorsten and Probst, Anne-Catherine and Zeising, Sebastian}, title = {Analyse der Schichtspannungen von R{\"o}ntgenspiegeln mit einem Weißlichtinterferometer}, series = {DGaO-Proceedings}, volume = {2018}, booktitle = {DGaO-Proceedings}, number = {2018}, publisher = {Deutsche Gesellschaft f{\"u}r angewandte Optik e.V.}, address = {Erlangen}, organization = {Hochschule Aschaffenburg}, issn = {1614-8436}, pages = {P10-1 -- P10-2}, year = {2018}, abstract = {An der Hochschule Aschaffenburg werden iridiumbasierte Schichtsysteme f{\"u}r r{\"o}ntgenastronomische Anwendungen hergestellt. Unter Nutzung eines Weißlichtinterferometers wurde hierf{\"u}r ein Verfahren zur Vermessung der inh{\"a}renten Schichtspannungen entwickelt. Erste vielversprechende Ergebnisse von spannungsarmen R{\"o}ntgenreflexionsbeschichtungen werden vorgestellt.}, subject = {R{\"o}ntgenspiegel}, language = {de} } @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} } @article{BuettnerProbstEmmerichetal.2018, author = {B{\"u}ttner, Andre and Probst, Anne-Catherine and Emmerich, Florian and Damm, Christine and Rellinghaus, Bernd and D{\"o}hring, Thorsten and Stollenwerk, Manfred}, title = {Influence of Sputtering Pressure on the Microstructure and Layer Properties of Iridium Thin Films}, series = {Thin Solid Films}, volume = {2018}, journal = {Thin Solid Films}, number = {662}, issn = {0040-6090}, pages = {41 -- 46}, year = {2018}, abstract = {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.}, subject = {Iridium}, language = {en} } @inproceedings{DoehringProbstStollenwerketal.2017, author = {D{\"o}hring, Thorsten and Probst, Anne-Catherine and Stollenwerk, Manfred and Emmerich, Florian and Stehl{\´i}kov{\´a}, Veronika and Inneman, Adolf}, title = {Prototyping iridium coated mirrors for X-ray astronomy}, series = {Proceedings of the International Society for Optics and Photonics}, volume = {2017}, booktitle = {Proceedings of the International Society for Optics and Photonics}, number = {10235}, editor = {Hudec, Ren{\´e} and Pina, Ladislav}, publisher = {SPIE International Society for Optics and Photonics}, address = {Bellingham WA}, organization = {Hochschule Aschaffenburg}, doi = {10.1117/12.2265931}, pages = {1023504-1 -- 1023504-8}, year = {2017}, abstract = {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.}, subject = {Iridium}, 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{ProbstDoehringZeisingetal.2017, author = {Probst, Anne-Catherine and D{\"o}hring, Thorsten and Zeising, Sebastian and Salmaso, Bianca and Stollenwerk, Manfred and Proserpio, Laura}, title = {Challenges in metrology of mirror segments for X-ray telescopes}, series = {Proceedings of the 8th High Level Expert Meeting Asphere Metrology}, volume = {2017}, booktitle = {Proceedings of the 8th High Level Expert Meeting Asphere Metrology}, number = {8}, publisher = {UTOB e.V.}, address = {Braunschweig}, organization = {Hochschule Aschaffenburg}, pages = {4}, year = {2017}, abstract = {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.}, subject = {Spiegelteleskop}, language = {en} } @inproceedings{DoehringProbstStehlikovaetal.2017, author = {D{\"o}hring, Thorsten and Probst, Anne-Catherine and Stehlikova, Veronika and Skala, Petr and Inneman, Adolf and Hudec, Rene}, title = {JEUMICO - Bayerisch-tschechische Kooperation zur Entwicklung von R{\"o}ntgenteleskopen}, series = {DGaO-Proceedings}, volume = {2017}, booktitle = {DGaO-Proceedings}, number = {2017}, publisher = {DGaO}, organization = {Hochschule Aschaffenburg}, issn = {1614-8436}, pages = {2}, year = {2017}, abstract = {Das Projekt JEUMICO wird vom Projekttr{\"a}ger BAYHOST im Rahmen eines Programms f{\"u}r bilaterale wissenschaftliche Projekte zwischen Tschechien und Bayern gef{\"o}rdert. Inhaltlich werden von der Hochschule Aschaffenburg und der Technischen Universit{\"a}t Prag hier gemeinsam R{\"o}ntgenoptiken f{\"u}r ein geplantes astronomisches Experiment an Bord einer NASA-H{\"o}henrakete entwickelt.}, subject = {R{\"o}ntgenstrahlung}, language = {de} } @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} } @inproceedings{StehlikovaProserpioFriedrichetal.2017, author = {Stehlikova, Veronika and Proserpio, Laura and Friedrich, Peter and Madarasz, Emanuel and Breunig, Elias and Burwitz, Vadim and D{\"o}hring, Thorsten and Probst, Anne-Catherine}, title = {Indirect glass slumping of grazing incidence mirror segments for lightweight x-ray telescopes}, 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}, organization = {Max-Planck Institut f{\"u}r extraterrestrische Physik}, doi = {10.1117/12.2272671}, pages = {103991Z-1 -- 103991Z-7}, year = {2017}, abstract = {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.}, subject = {Iridium}, language = {en} } @inproceedings{StehlikovaProbstNentvichetal.2017, author = {Stehlikova, Veronika and Probst, Anne-Catherine and Nentvich, Ondrej and Urban, Martin and Inneman, Adolf and Sieger, Ladislav and Marsikova, Veronika and D{\"o}hring, Thorsten}, title = {Development of iridium coated silicon X-ray mirrors for Lobster Eye astronomical telescopes}, series = {Proceedings of EOSMOS 2017}, volume = {2017}, booktitle = {Proceedings of EOSMOS 2017}, number = {EOSMOS 2017}, publisher = {European Optical Society}, organization = {CVUT Prag}, pages = {1 -- 2}, year = {2017}, abstract = {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.}, 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} } @article{ProbstBegouDoehringetal.2018, author = {Probst, Anne-Catherine and Begou, Thomas and D{\"o}hring, Thorsten and Zeising, Sebastian and Stollenwerk, Manfred and Stadtm{\"u}ller, Johannes and Emmerich, Florian and Lumeau, Julien}, title = {Coating stress analysis and compensation for iridium-based x-ray mirrors}, series = {Applied Optics}, volume = {2018}, journal = {Applied Optics}, number = {57 (29)}, editor = {Publishing OSA,}, pages = {8775 -- 8779}, year = {2018}, abstract = {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.}, subject = {R{\"o}ntgenteleskop}, language = {en} } @inproceedings{ProbstHitzingerBochtleretal.2021, author = {Probst, Anne-Catherine and Hitzinger, Hans and Bochtler, Ulrich and W{\"o}lfel, Maximilian and Schmitt, Christoph}, title = {High Frequency Power Amplifier for Wideband Wireless Communication Systems}, series = {Proceedings of the 2021 Kleinheubach Conference}, volume = {2021}, booktitle = {Proceedings of the 2021 Kleinheubach Conference}, editor = {U.R.S.I. Landesausschuss in Deutschland e.V. 2021,}, doi = {10.23919/IEEECONF54431.2021.9598443}, pages = {4}, year = {2021}, abstract = {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.}, subject = {Hochfrequenzverst{\"a}rker}, language = {en} } @inproceedings{NeumaierProbstWoelfeletal.2025, author = {Neumaier, Marcel and Probst, Anne-Catherine and W{\"o}lfel, Maximilian and Bochtler, Ulrich}, title = {Performance Analysis in a Digital TETRA-Simulcast System}, series = {2025 16th German Microwave Conference (GeMiC)}, booktitle = {2025 16th German Microwave Conference (GeMiC)}, year = {2025}, abstract = {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.}, subject = {TETRA, Telekommunikation}, language = {en} } @inproceedings{ProbstNeumaierHufgardetal.2025, author = {Probst, Anne-Catherine and Neumaier, Marcel and Hufgard, Christopher and W{\"o}lfel, Maximilian and Schmitt, Christoph and Bochtler, Ulrich}, title = {Network Planning a Digital TETRA-Simulcast-System}, series = {Kleinheubacher Tagung, Miltenberg, 23.09.2025 - 25.09.2025}, booktitle = {Kleinheubacher Tagung, Miltenberg, 23.09.2025 - 25.09.2025}, year = {2025}, subject = {TETRA, Telekommunikation}, language = {en} }