@inproceedings{StollenwerkMichaeliTelgenbuescheretal.1992, author = {Stollenwerk, Manfred and Michaeli, Walter and Telgenb{\"u}scher, Klaus and Leiber, J{\"o}rn and Londschein, Martin}, title = {Verbesserung von Verbundwerkstoffen durch Plasmabehandlung der Verst{\"a}rkungsfasern}, year = {1992}, subject = {Faserverst{\"a}rkter Kunststoff}, language = {de} } @article{StollenwerkGruetzmacher1991, author = {Stollenwerk, Manfred and Gr{\"u}tzmacher, Detlev}, title = {GaInAs/GaInAsP SC-MQW-laser emitting at 1.35 µm grown by LP-MOVPE}, series = {Microelectronic Engineering}, volume = {1991}, journal = {Microelectronic Engineering}, number = {15}, pages = {263 -- 266}, year = {1991}, subject = {Quantenwell-Laser}, language = {en} } @inproceedings{StollenwerkGruetzmacherHeimeetal.1991, author = {Stollenwerk, Manfred and Gr{\"u}tzmacher, Detlev and Heime, Klaus and M{\"o}hrle, Martin and Fidorra, Frank}, title = {GaInAs/GaInAsP SC-MQW Laser mit einer Emissionswellenl{\"a}nge von 1,35 µm deponiert mit Hilfe der LP-MOVPE}, year = {1991}, subject = {Quantenwell-Laser}, language = {de} } @inproceedings{StollenwerkGruetzmacherSchwedleretal.1991, author = {Stollenwerk, Manfred and Gr{\"u}tzmacher, Detlev and Schwedler, Ralf and Meyer, R. and Hardtdegen, Hilde and Kux, A. and Heime, Klaus}, title = {Systematic study of strained GaInAs/InP grown by MOVPE}, year = {1991}, subject = {Galliumarsenid}, language = {en} } @article{OschinowoForchelGruetzmacheretal.1992, author = {Oschinowo, John and Forchel, Alfred and Gr{\"u}tzmacher, Detlev and Stollenwerk, Manfred and Heuken, Michael and Heime, Klaus}, title = {Photoluminescence study of interdiffusion in In0,53Ga0,47/As/InP surface quantum wells}, series = {Applied Physics Letters}, volume = {60}, journal = {Applied Physics Letters}, number = {21}, pages = {2660 -- 2662}, year = {1992}, abstract = {We have investigated the thermal stability and interdiffusion of In0.53Ga0.47As/InP surface quantum wells. In these structures the optically active InGaAs layer is bounded on one side by vacuum and on the other side by InP. We obtain well-defined photoluminescence emission spectra with high intensity. After rapid thermal annealing at temperatures between 500 and 900 °C (annealing time 1 min) we observe strong emission energy shifts of up to 316 meV. By using a simple model of ion intermixing we estimate large interdiffusion coefficients (e.g., 1.7×10-14 cm2 s-1 for T=900 °C) and an activation energy of 1.3 eV for the surface quantum wells.}, subject = {Photolumineszenz}, language = {en} } @inproceedings{OschinowoForchelGruetzmacheretal.1991, author = {Oschinowo, John and Forchel, Alfred and Gr{\"u}tzmacher, Detlev and Stollenwerk, Manfred}, title = {RTA study of thermal stability and interdiffusion of InGaAs/InP quantum wells - the influence of InGaAs cap layers}, series = {Third International Conference Indium Phosphide and Related Materials Cardiff/Wales}, booktitle = {Third International Conference Indium Phosphide and Related Materials Cardiff/Wales}, pages = {606 -- 609}, year = {1991}, abstract = {A study of the thermal stability of InGaAs/InP quantum wells with different top barrier compositions that used rapid thermal annealing at temperatures between 600 degrees C and 950 degrees C (annealing time 1 min) is discussed. The thermal interdiffusion effects were evaluated by photoluminescence spectroscopy. From the temperature dependence of the luminescence energy shifts the interdiffusion coefficients and activation energies are determined.}, subject = {Photolumineszenzspektroskopie}, language = {en} } @article{ShiGruetzmacherStollenwerketal.1992, author = {Shi, Chang-Xin and Gr{\"u}tzmacher, Detlev and Stollenwerk, Manfred and Wang, Qing-Kang and Heime, Klaus}, title = {High-performance undoped InP/n-InP/GaAs MSM photodetectors grown by LP-MOVPE}, series = {IEEE Transactions on Electron Devices}, volume = {39}, journal = {IEEE Transactions on Electron Devices}, number = {5}, publisher = {IEEE}, pages = {1028 -- 1031}, year = {1992}, subject = {Indiumarsenid}, language = {en} } @article{StollenwerkDoehringFreudenmannetal.2021, author = {Stollenwerk, Manfred and D{\"o}hring, Thorsten and Freudenmann, Dominic and Sch{\"a}fer, Tobias and Stadtm{\"u}ller, Johannes and R{\"o}cke, Nicole}, title = {Sputtered highly effective iridium catalysts: a new approach for green satellite propulsion}, series = {Journal of Materials Science}, volume = {2021}, journal = {Journal of Materials Science}, number = {2021}, doi = {https://doi.org/10.1007/s10853-021-05897-z}, pages = {1 -- 11}, year = {2021}, abstract = {This work demonstrated the large potential of sputtered iridium metal for catalytic reactions shown by the example of decomposition of hydrogen peroxide (H2O2) for space propulsion systems. For this purpose, iridium was coated onto Al2O3 pellets by a sputter process under varied process parameters. Depending on previously selected parameters, the obtained metal-loaded pellets offer closed- and/or open-shell structures. Catalytic productivity of these first-generation iridium-sputtered catalysts was estimated in laboratory experiments and compared to platinum-loaded pellets. Under optimized sputter-process conditions, the reactivity is significantly improved compared to the platinum-impregnated pellets. The better catalytic productivity can be explained by the increased active surface area of the iridium layers on the pellets. The surface morphology and the microstructure of the iridium coating can be actively controlled by the sputter pressure. The results are in accordance with the sputtering process pressure tendency described by the Thornton Structure-Zone Model.}, subject = {Iridium}, language = {en} } @misc{DoehringStollenwerkStadtmuelleretal.2021, author = {D{\"o}hring, Thorsten and Stollenwerk, Manfred and Stadtm{\"u}ller, Johannes and Freudenmann, Dominic and R{\"o}cke, Nicole}, title = {Nanostructured iridium catalysts for effective hydrogen peroxide decomposition}, series = {EuroNanoForum}, volume = {2021}, journal = {EuroNanoForum}, organization = {TH Aschaffenburg}, pages = {1}, year = {2021}, abstract = {The EU intends to restrict the use of critical fuels in space propulsion systems. These propellants like hydrazine are chemically aggressive, toxic and carcinogenic. Space propulsion of the future should be environmentally friendly, inexpensive, and easy to handle. Aschaffenburg University and DLR are currently developing environmentally friendly technologies for future satellite engines. Thereby rocket-grade hydrogen peroxide, which is foreseen as a substitute, is converted to uncritical water vapour and oxygen by an exothermic catalytic reaction on nanostructured iridium layers. The resulting hot gases provide the required amount of thrust. The iridium catalyst layers are coated onto ceramic pellets, using RF magnetron sputtering technology. The catalytic functionality was tested afterwards at the chemical laboratories of DLR. First experimental results show a significantly higher catalytic activity for nanostructured iridium surfaces than for smoother crystalline layers.}, subject = {Iridium}, language = {en} } @inproceedings{StanikDoehringPregleretal.2024, author = {Stanik, Eva and D{\"o}hring, Thorsten and Pregler, Jan and Stollenwerk, Manfred and Hildenbrand, Georg}, title = {Spectral measurements and life science experiments using extreme radiation exposures at high altitude}, series = {Proceedings of SPIE}, volume = {2024}, booktitle = {Proceedings of SPIE}, number = {13024}, doi = {10.1117/12.3028519}, pages = {130240M -- 130240M}, year = {2024}, abstract = {The ASTRABAX project ("Aschaffenburg Stratospheric Balloon Experiment"), being funded for the years 2024 to 2026, is designed as a multimodal platform for the investigation of radiation exposures at high altitude. The UV-C spectral region is of special interest. Spectral measurements observe this region of interest using miniature UV-VIS spectrometers. The platform also contains a radiation dosimetry, a power source for on-board electronics, and common shielding setups for multiple spectral combinations. Human cells are exposed simultaneously to radiation of different compositions as particle, X-ray and UV radiation. After the flight, possible changes in the spatial chromatin organization are examined. Material samples intended for the development of satellite components are irradiated also. Investigations under such conditions are realistic and crucial for high altitude flights in the atmosphere, for space flights as well as for comparable exposures on other objects of the solar system, and even for exoplanet habitats to some extent.}, subject = {Spektroskopie}, language = {en} } @misc{DoehringStanikPregleretal.2024, author = {D{\"o}hring, Thorsten and Stanik, Eva and Pregler, Jan and Stollenwerk, Manfred and Hildenbrand, Georg}, title = {Forschung zu Strahlensch{\"a}den mit dem Stratosph{\"a}renballon-Experiment ASTRABAX}, organization = {Technische Hochschule Aschaffenburg}, pages = {1 -- 1}, year = {2024}, abstract = {Das f{\"u}r die Jahre 2024 bis 2026 gef{\"o}rderte Projekt ASTRABAX („Aschaffenburger Stratosph{\"a}renballon- Experiment") ist als multimodale Plattform der Material- und Biowissenschaften f{\"u}r Untersuchungen bei extremen Strahlenbelastungen in großer H{\"o}he konzipiert. Dabei ist der UV-C-Spektralbereich von besonderem Interesse und wird mit Miniatur-UV-Spektrometern untersucht. Die Plattform des Ballonexperimentes umfasst eine gemeinsame Strahlungsdosimetrie, eine Stromquelle f{\"u}r die Bordelektronik und Abschirmungen f{\"u}r mehrere Bestrahlungskombinationen. Biologische Zellen werden Kombinationen aus Partikel-, R{\"o}ntgen- und UV-Strahlung ausgesetzt. Nach dem Flug werden m{\"o}gliche Ver{\"a}nderungen in der r{\"a}umlichen Chromatinorganisation mittels hochaufl{\"o}sender Mikroskopie untersucht. Auswirkungen von Kombinationen aus hoch- und niederenergetischer Strahlung sind bisher nicht ausreichend erforscht und beschrieben. Zus{\"a}tzlich werden auch f{\"u}r Satelliten relevante Materialproben bestrahlt. Untersuchungen unter solchen Bedingungen sind realistisch und relevant f{\"u}r Fl{\"u}ge in der Stratosph{\"a}re, f{\"u}r Raumfl{\"u}ge sowie f{\"u}r vergleichbare Expositionen bei anderen Objekten des Sonnensystems oder Exoplaneten-Habitaten.}, subject = {Stratosph{\"a}ren-Ballon}, language = {de} } @incollection{MannWenzlerDoehringetal.2022, author = {Mann, Michael and Wenzler, Sebastian and D{\"o}hring, Thorsten and Stollenwerk, Manfred and Pribulla, Theodor and Sivanič, Peter and Komž{\´i}k, Richard}, title = {Stromversorgung als Umweltfaktor: Analyse der elektrischen Netzqualit{\"a}t in astronomischen Observatorien}, series = {Umwelteinfl{\"u}sse erfassen, simulieren, bewerten}, volume = {2022}, booktitle = {Umwelteinfl{\"u}sse erfassen, simulieren, bewerten}, editor = {Karl Friedrich, Zieghahn}, publisher = {Gesellschaft f{\"u}r Umweltsimulation e.V.}, isbn = {978-3-9818507-7-2}, pages = {193 -- 207}, year = {2022}, subject = {Sternwarte}, language = {de} } @misc{StanikDoehringPregleretal.2024, author = {Stanik, Eva and D{\"o}hring, Thorsten and Pregler, Jan and Stollenwerk, Manfred and Hildenbrand, Georg}, title = {Spectral measurements and life science experiments using extreme radiation exposures at high altitude}, organization = {Technische Hochschule Aschaffenburg}, pages = {1}, year = {2024}, abstract = {The ASTRABAX project ("Aschaffenburg Stratospheric Balloon Experiment"), being funded for the years 2024 to 2026, is designed as a multimodal platform for the investigation of radiation exposures at high altitude. Miniature UV-VIS spectrometers observe the UV-C spectral region. The platform also contains a radiation dosimetry, a power source for on-board electronics, and common shielding setups for multiple spectral combinations. The effects of combinations of high- and low-energy rays on human cells haven´t been sufficiently investigated and described so far. Investigations under such conditions are realistic and crucial for high altitude flights in the atmosphere, for space flights as well as for comparable exposures on other objects of the solar system, and even for exoplanet habitats to some extent.}, subject = {Stahlenbelastung}, language = {en} } @inproceedings{MannDoehringStollenwerketal.2024, author = {Mann, Michael and D{\"o}hring, Thorsten and Stollenwerk, Manfred and Priebsch, Alessandro and Pribulla, Theodor and Komž{\´i}k, Richard M. and Sivanic, Peter}, title = {Advanced power quality measurement techniques at the electric power grid of astronomical observatories}, series = {Observatory Operations: Strategies, Processes, and Systems X, Conference of SPIE 13098, 17 - 20 June 2024}, booktitle = {Observatory Operations: Strategies, Processes, and Systems X, Conference of SPIE 13098, 17 - 20 June 2024}, editor = {Storrie-Lombardi, Lisa J. and Benn, Chris R. and Chrysostomou, Antonio}, publisher = {SPIE}, doi = {10.1117/12.3016562}, year = {2024}, subject = {Sternwarte}, language = {en} } @inproceedings{MannDoehringStollenwerketal.2022, author = {Mann, Michael and D{\"o}hring, Thorsten and Stollenwerk, Manfred and Wenzler, Sebastian and Pribulla, Theodor and Komž{\´i}k, Richard M. and Sivanic, Peter}, title = {On the importance of the electrical grid power quality for astronomical observatories}, series = {Proceedings of SPIE: Observatory Operations: Strategies, Processes, and Systems IX}, booktitle = {Proceedings of SPIE: Observatory Operations: Strategies, Processes, and Systems IX}, editor = {Benn, Chris R. and Seaman, Robert L. and Adler, David S.}, publisher = {SPIE}, doi = {http://dx.doi.org/10.1117/12.2627227}, year = {2022}, subject = {Elektrizit{\"a}tsversorgung}, language = {en} } @inproceedings{DoehringStanikPregleretal.2024, author = {D{\"o}hring, Thorsten and Stanik, Eva and Pregler, Jan and Stollenwerk, Manfred and Hildenbrand, Georg}, title = {Forschung zu Strahlensch{\"a}den mit dem Stratosph{\"a}renballon-Experiment ASTRABAX}, series = {DGaO-Proceedings}, volume = {2024}, booktitle = {DGaO-Proceedings}, number = {125}, pages = {1 -- 2}, year = {2024}, abstract = {Das Stratosph{\"a}renballon-Experiment ASTRABAX ist als multimodale Plattform der Material- und Biowissenschaften f{\"u}r Untersuchungen bei extremen Strahlenbelastungen konzipiert, mit Fokus auf dem UV-C-Spektralbereich und der kosmischen H{\"o}henstrahlung. Auswirkungen von Kombinationen aus hoch- und niederenergetischer Strahlung sind relevant, jedoch nicht ausreichend erforscht.}, subject = {Stratosph{\"a}ren-Ballon}, language = {de} } @article{AmorimSperaNicoaraetal.2024, author = {Amorim, Isilda and Spera, Natalia C.M. and Nicoara, Nicoleta and Ramasamy, Devaraj and Alves, Diana F. and Stollenwerk, Manfred and Stadtm{\"u}ller, Johannes and D{\"o}hring, Thorsten and Sadewasser, Sascha and Kolen'ko, Yury V. and Sousa, Juliana P.S.}, title = {Overall alkaline water electrolysis over active, stable, low loading iridium catalysts sputtered on nickel foam}, series = {International Journal of Hydrogen Energy}, volume = {92}, journal = {International Journal of Hydrogen Energy}, publisher = {Elsevier BV}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2024.10.306}, pages = {852 -- 864}, year = {2024}, subject = {Iridium}, language = {en} } @incollection{WisselFreudenmannPerezetal.2025, author = {Wissel, Julian and Freudenmann, Dominic and Perez, Nicolas and D{\"o}hring, Thorsten and Stadtm{\"u}ller, Johannes and Stollenwerk, Manfred}, title = {Various highly effective sputtered layer structures as catalysts for H2O2 decomposition for use in satellite engines}, series = {MaterialsWeek 2025 - Book of Abstracts}, booktitle = {MaterialsWeek 2025 - Book of Abstracts}, publisher = {Deutsche Gesellschaft f{\"u}r Materialkunde e.V. (DGM)}, address = {Sankt Augustin}, isbn = {978-3-88355-446-4}, pages = {53 -- 53}, year = {2025}, abstract = {Catalysts are frequently employed in both research and industrial applications to facilitate or accelerate chemical reactions. One such application is in monopropellant thrusters for space propulsion systems, where hydrogen peroxide (H2O2) is used as a liquid propellant. The decomposition of liquid hydrogen peroxide into water and oxygen gas, which ultimately generates thrust, can be achieved using noble metal catalysts from the platinoid group, such as platinum and iridium. This promotes the use of more environmentally friendly and less toxic propellants, such as H2O2, instead of hydrazine and nitrogen tetroxide (NTO). The optimization of coating structures with these catalytic materials is essential for future space applications, as it aims to extend the lifespan of catalyst materials and results in a better utilization of H2O2 in satellite engines. Therefore, different layer structures were deposited onto Duranit D99 pellets using a controlled magnetron sputtering process. Previous studies have shown that the used sputtering pressure has a strong influence on the structure of the deposited coatings [2][3]. Certain parameter combinations produce catalytic layers with rough textures and a highly porous microstructure, see figure 1 [1]. To improve the thermal and mechanical stability of the sputtered layers, thin adhesive layers of Titanium and Zirconium were applied beneath the catalytic layer. The pellets were then heated in an oven at 640°C for one minute to simulate the thermal effects experienced in a satellite engine during ignition. Following this, the catalytic performance of the pellets was tested in laboratory experiments using 30\% H2O2. Pellets with sputtered platinum as the catalytic coating delivered the best results. These coatings will be further evaluated in an engine test conducted at the German Aerospace Centre (DLR). Hydrogen peroxide is also expected to play a crucial role in future lunar and Martian colonization efforts. In this context, catalytic coatings would be used to decompose H2O2 to supply astronauts with water and oxygen, rather than to generate thrust in satellite engines.}, subject = {Satellitentechnik}, language = {en} } @misc{LicciardelloDoehringStollenwerketal.2021, author = {Licciardello, Nadia and D{\"o}hring, Thorsten and Stollenwerk, Manfred and Kolen'ko, Yury V. and Petrovykh, Dmitri Y.}, title = {Innovative nanocomposite coatings for radiation shielding on satellites}, series = {EuroNanoForum}, volume = {2021}, journal = {EuroNanoForum}, organization = {International Iberian Nanotechnology Laboratory}, pages = {1}, year = {2021}, abstract = {The current trend in development of low-cost satellites is based on small dimensions combined with advanced electronics. Traditionally, radiation-sensitive electronics on satellites are protected by tungsten or lead foils, which are high-density materials and contribute significantly to the overall mass of the satellite. Here, we design and investigate temperature-gradient-resistant lightweight silane-based composites containing micro- or nano-particles of W or WO3, taking inspiration from similar approaches in the medical field. While the polymeric matrix provides flexibility under thermal gradients (such as those occurring in satellites during their orbits) and low density, the particles enable shielding from soft X-rays and other radiation. For reference, thin tungsten films were deposited by magnetron sputtering. The properties of the two kinds of coatings were compared and the X-ray protective properties were investigated using both a custom-designed measurement setup and conventional X-ray absorption. The best performing radiation-protective coatings will be launched in a payload experiment on the INFANTE satellite.}, subject = {Satellitentechnik}, language = {en} } @inproceedings{RivoltaBassoCivitanietal.2022, author = {Rivolta, Giacomo and Basso, Stefano and Civitani, Marta Maria and Cotroneo, Vincenzo and D{\"o}hring, Thorsten and Michler, Willy-Leopold and Pareschi, Giovanni and Spiga, Daniele and Stollenwerk, Manfred}, title = {Upgrade of a laboratory X-ray diffractometer to extend its operating range towards soft energies}, series = {Proceedings of SPIE}, volume = {2022}, booktitle = {Proceedings of SPIE}, number = {12181}, publisher = {SPIE}, organization = {Osservatorio Astronomico di Brera}, issn = {0277-786X}, doi = {doi: 10.1117/12.2629940}, pages = {121814S-1 -- 121814s-7}, year = {2022}, abstract = {The optical properties of X-ray mirror samples are commonly measured using diffractometers based on laboratory sources; like the Bede D1 diffractometer operating at INAF-OAB. This instrument can generate a collimated X-ray beam up to 60 keV, even though the most interesting energy region for x-ray astronomy applications is usually below 10 keV. In the softest part of this range (below 6 keV), high X-ray absorption in air hinders a full and precise characterization of optical components. In this work, we present an upgrade of the Bede D1 diffractometer that extends the operative range of the instrument below 6 keV; this is done by maximizing the flux at lowest energies and by reducing absorption by means of a helium-rich atmosphere. The upgraded instrument will be used for the tests of X-ray mirrors with innovative soft X-ray coatings, with potential application to the next generation X-ray telescopes (such as ATHENA and eXTP).}, subject = {R{\"o}ntgenspiegel}, language = {en} } @article{WisselFreudenmannCichockaetal.2024, author = {Wissel, Julian and Freudenmann, Dominic and Cichocka, Magdalena Ola and P{\"o}hl, Almut and Stephan-Hofmann, Iris and R{\"o}cke, Nicole and P{\´e}rez, Nicol{\´a}s and D{\"o}hring, Thorsten and Stadtm{\"u}ller, Johannes and Stollenwerk, Manfred}, title = {Microstructure of highly effective platinum-iridium alloys as catalysts for hydrogen peroxide decomposition}, series = {Research on Chemical Intermediates}, volume = {50}, journal = {Research on Chemical Intermediates}, number = {11}, publisher = {Springer Science and Business Media LLC}, issn = {0922-6168}, doi = {10.1007/s11164-024-05412-4}, pages = {5385 -- 5397}, year = {2024}, subject = {Iridium}, language = {en} } @incollection{StanikStollenwerkHuebneretal.2025, author = {Stanik, Eva and Stollenwerk, Manfred and H{\"u}bner, Sophie and Stadtm{\"u}ller, Johannes and D{\"o}hring, Thorsten}, title = {Experimental studies on iridium catalysts for water PEM electrolysis}, series = {MaterialsWeek 2025 - Book of Abstracts}, booktitle = {MaterialsWeek 2025 - Book of Abstracts}, publisher = {Deutsche Gesellschaft f{\"u}r Materialkunde e.V. (DGM)}, address = {Sankt Augustin}, isbn = {978-3-88355-446-4}, pages = {62 -- 62}, year = {2025}, abstract = {The enhanced use of sustainable energy sources entails strong fluctuations in the availability of electric power. As we need new approaches for energy distribution and energy storage systems, hydrogen is often discussed as a promising energy carrier. PEM electrolysis can be used to transform electrical energy from renewable sources into hydrogen. One challenge in this context is the need for catalysts, as these contribute significantly to the performance of the electrolysis cell. The commonly used platinum group metal (PGM) catalysts like Iridium are quite scarce and therefore expensive. A possible approach to reduce the Ir content is the application of magnetron sputtering for catalyst generation. By selecting the right process parameters, the desired layer properties can be set very precisely during sputtering. This ensures a large surface area with reduced material usage. The introduction of carbon can increase the surface area of the catalyst further and enhance its effectiveness. First results of investigations on the catalytic effect of sputtered Ir catalyst layers will be presented.}, subject = {Iridium}, language = {en} } @inproceedings{StehlikovaDoehringStollenwerketal.2021, author = {Stehlikova, Veronika and D{\"o}hring, Thorsten and Stollenwerk, Manfred and Stadtm{\"u}ller, Johannes and Marsikova, Veronika and Hudec, Rene and Flachs, Dennis and Burwitz, Vadim and Hartner, Gisela and Rukdee, Surangkhana and M{\"u}ller, Thomas and Schmidt, Thomas and Inneman, Adolf and Klementova, Mariana and Zeising, Sebastian and Langmeier, Andreas}, title = {Lobster eye type X-ray telescope with chromium-iridium coated tri-layer mirrors}, series = {Proceedings of SPIE}, volume = {2021}, booktitle = {Proceedings of SPIE}, number = {11776}, publisher = {SPIE}, organization = {Czech Technical University in Prague}, doi = {https://doi.org/10.1117/12.2589266}, pages = {1177605-1 -- 1177605-8}, year = {2021}, abstract = {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.}, subject = {R{\"o}ntgenteleskop}, language = {en} } @inproceedings{DoehringStollenwerkStadtmuelleretal.2021, author = {D{\"o}hring, Thorsten and Stollenwerk, Manfred and Stadtm{\"u}ller, Johannes and Zeising, Sebastian and Flachs, Dennis and Stehlikova, Veronika and Burwitz, Vadim and Krumrey, Michael K. and Cotroneo, Vincenzo and Klementova, Mariana}, title = {Characterisation of X-ray mirrors based on chromium-iridium tri-layer coatings}, series = {Proceedings of SPIE}, volume = {2021}, booktitle = {Proceedings of SPIE}, number = {11776}, publisher = {SPIE}, organization = {TH Aschaffenburg}, doi = {https://doi.org/10.1117/12.2592551}, pages = {1177607-1 -- 11776076}, year = {2021}, abstract = {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.}, subject = {R{\"o}ntgenspiegel}, language = {en} }