@misc{DoehringStollenwerkProserpioetal.2015, author = {D{\"o}hring, Thorsten and Stollenwerk, Manfred and Proserpio, Laura and Winter, Anita}, title = {Transfer of astronomical mirror technologies - Project INTRAAST}, year = {2015}, abstract = {Poster}, subject = {Optisches Glas}, language = {en} } @inproceedings{DoehringStollenwerkGongetal.2015, author = {D{\"o}hring, Thorsten and Stollenwerk, Manfred and Gong, Qingqing and Proserpio, Laura and Winter, Anita and Friedrich, Peter}, title = {The challenge of developing thin mirror shells for future X-ray telescopes}, series = {Proceedings of SPIE}, volume = {2015}, booktitle = {Proceedings of SPIE}, number = {9628}, organization = {Hochschule Aschaffenburg}, pages = {962809-1 -- 962809-8}, year = {2015}, abstract = {Previously used mirror technologies are not able to fulfil the requirements of future X-ray telescopes due to challenging requests from the scientific community. Consequently new technical approaches for X-ray mirror production are under development. In Europe the technical baseline for the planned X-ray observatory ATHENA is the radical new approach of silicon pore optics. NASA´s recently launched NuSTAR mission uses segmented mirrors shells made from thin bended glasses, successfully demonstrating the feasibility of the glass forming technology for X-ray mirrors. For risk mitigation also in Europe the hot slumping of thin glasses is being developed as an alternative technology for lightweight X-ray telescopes. The high precision mirror manufacturing requires challenging technical developments; several design trades and trend-setting decisions need to be made and are discussed within this paper. Some new technical and economic aspects of the intended glass mirror serial production are also studied within the recently started interdisciplinary project INTRAAST, an acronym for "industry transfer of astronomical mirror technologies". The goal of the project, embedded in a cooperation of the Max-Planck-Institute for extraterrestrial Physics and the University of Applied Sciences Aschaffenburg, is to master the challenge of producing thin mirror shells for future X-ray telescopes. As a first project task the development of low stress coatings for thin glass mirror substrates have been started, the corresponding technical approach and first results are presented.}, subject = {Astronomie}, language = {en} } @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{DoehringStollenwerkProserpioetal.2016, author = {D{\"o}hring, Thorsten and Stollenwerk, Manfred and Proserpio, Laura and Breunig, Elias and Friedrich, Peter}, title = {The challenging development of lightweight glass mirrors for future X-ray telescopes}, series = {DGaO Proceedings}, volume = {2016}, booktitle = {DGaO Proceedings}, publisher = {Deutsche Gesellschaft f{\"u}r angewandte Optik}, address = {Erlangen}, organization = {Hochschule Aschaffenburg}, issn = {1614-8436}, url = {http://nbn-resolving.de/nbn:de:0287-2016-B018-0}, pages = {2}, year = {2016}, abstract = {Previously used mirror technologies are not able to fulfill the challenging requirements of future X-ray telescopes. A promising new technology under development is the hot slumping of thin glasses. Challenges, design trades and first results are presented, including the thermal shaping process, the development of low stress coatings and the mirror segments integration concept.}, subject = {R{\"o}ntgenteleskop}, 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{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{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{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} } @misc{DoehringProbullaKomziketal.2018, author = {D{\"o}hring, Thorsten and Probulla, Theodor and Komzik, Richard and Mann, Michael and Sivanic, Peter and Stollenwerk, Manfred}, title = {Slovak-Bavarian collaboration on the development of telescope instrumentation}, editor = {Hambalek, Lubomir}, organization = {Hochschule Aschaffenburg}, pages = {1}, year = {2018}, abstract = {Within the project SLOBATCO (Slovak-Bavarian Telescope Collaboration) the Astronomical Institute of the Slovak Academy of Sciences and Aschaffenburg University of Applied Sciences collaborate in the development and commissioning of the new {\O}1.3 m astronomical telescope and the corresponding scientific instrumentation. The project is funded by the Bavarian Academic Center for Central, Eastern and Southeastern Europe (BAYHOST). Technical work packages are targeting filter wheel software for the VIS camera, additional IR filters, and an upgrade of the mirror coating facility by additional sputtering equipment.}, subject = {Spiegelteleskop}, 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{DoehringStollenwerkSchmittetal.2022, author = {D{\"o}hring, Thorsten and Stollenwerk, Manfred and Schmitt, Paul and Szeghalmi, Andrea}, title = {Umweltbest{\"a}ndige Spiegelbeschichtungen aus Iridium f{\"u}r den infraroten Spektralbereich}, series = {DGaO Proceedings}, volume = {2022}, booktitle = {DGaO Proceedings}, number = {123}, publisher = {DGaO}, organization = {TH Aschaffenburg}, issn = {1614-8436}, pages = {1 -- 2}, year = {2022}, abstract = {Das Edelmetall Iridium ist hart; extrem dicht; thermisch, mechanisch und chemisch stabil; weist eine hohe Reflektivit{\"a}t im mittleren und fernen Infrarot auf und hat eine hohe Best{\"a}ndigkeit gegen{\"u}ber Umwelteinfl{\"u}ssen - auch ohne weitere Schutzschichten. Es wurden die komplexen Brechungsindizes f{\"u}r Iridium-Spiegelbeschichtungen bestimmt, welche vorhandene Literaturwerte erg{\"a}nzen.}, subject = {Iridium}, language = {de} } @article{SchmittFeldeDoehringetal.2022, author = {Schmitt, Paul and Felde, Nadja and D{\"o}hring, Thorsten and Stollenwerk, Manfred and Uschmann, Ingo and Hanemann, Kevin and Siegler, Marie and Klemm, Georg and Gratzke, Nancy and T{\"u}nnermann, Andreas and Schwinde, Stefan and Schr{\"o}der, Sven and Szeghalmi, Adriana}, title = {Optical, structural, and functional properties of highly reflective and stable iridium mirror coatings for infrared applications}, series = {Optical Materials Express}, volume = {2022}, journal = {Optical Materials Express}, number = {12 / 2}, doi = {10.1364/OME.447306}, pages = {545 -- 559}, year = {2022}, abstract = {Metallic coatings are essential for numerous optical systems due to their high and broadband refl ectivity in the infrared spectral range. In contrast to well-established (protected)silver and gold mirror coatings, iridium is environmentally durable, referring to ISO 9211-3 and thermally stable up to 600 °C even without protective layers, as demonstrated. Additionally,the optical and related structural properties of atomic layer deposited (ALD) and magnetron sputtered (MS) Ir coatings were investigated using spectrophotometry, FTIR, ellipsometry, WLI,AFM, XRR, XRD, SEM, and electrical resistivity measurements. The properties of Ir ALD and Ir MS coatings diff er due to their topography and microstructure.}, subject = {Iridium}, language = {en} } @article{SchmittFeldeDoehringetal.2022, author = {Schmitt, Paul and Felde, Nadja and D{\"o}hring, Thorsten and Stollenwerk, Manfred and Uschmann, Ingo and Hanemann, Kevin and Siegler, Marie and Klemm, Georg and Gratzke, Nancy and T{\"u}nnermann, Andreas and Schwinde, Stefan and Schr{\"o}der, Sven and Szeghalmi, Adriana}, title = {Optical, structural, and functional properties of highly reflective and stable iridium mirrorcoatings for infrared applications: supplement}, series = {Optical Materials Express}, volume = {2022}, journal = {Optical Materials Express}, number = {12/2}, doi = {10.6084/m9.figshare.17121509}, pages = {545 -- 559}, year = {2022}, abstract = {Metallic coatings are essential for numerous optical systems due to their high and broadband refl ectivity in the infrared spectral range. In contrast to well-established (protected)silver and gold mirror coatings, iridium is environmentally durable, referring to ISO 9211-3 and thermally stable up to 600 °C even without protective layers, as demonstrated. Additionally,the optical and related structural properties of atomic layer deposited (ALD) and magnetron sputtered (MS) Ir coatings were investigated using spectrophotometry, FTIR, ellipsometry, WLI, AFM, XRR, XRD, SEM, and electrical resistivity measurements. The properties of Ir ALD and Ir MS coatings diff er due to their topography and microstructure.}, subject = {Iridium}, language = {en} } @misc{DoehringStollenwerkSchmittetal.2022, author = {D{\"o}hring, Thorsten and Stollenwerk, Manfred and Schmitt, Paul and Szeghalmi, Adriana}, title = {Umweltbest{\"a}ndige Spiegelbeschichtungen aus Iridium f{\"u}r den infraroten Spektralbereich}, publisher = {DGaO}, organization = {TH Aschaffenburg}, pages = {1 -- 1}, year = {2022}, abstract = {Hochreflektierende Metallbeschichtungen sind essenziell f{\"u}r zahlreiche optische Elemente. Bew{\"a}hrte Spiegelbeschichtungen aus Silber und Gold bieten eine hohe und breitbandige Eigenreflexion im infraroten Spektralbereich, sind ohne geeignete Schutzschichten jedoch anf{\"a}llig gegen{\"u}ber Umwelteinfl{\"u}ssen und mechanischer Beanspruchung. Insbesondere im langwelligen Spektralbereich verringern die Absorptionsbanden dieser Schutzschichten teilweise die hohe Spiegelreflektivit{\"a}t wieder. Das Edelmetall Iridium (Ir) ist hart; extrem dicht; thermisch, mechanisch und chemisch stabil; weist eine {\"a}hnlich hohe Reflektivit{\"a}t im mittleren und fernen Infrarot, wie Silber und Gold, auf und hat zus{\"a}tzlich eine hohe Best{\"a}ndigkeit gegen{\"u}ber Umwelteinfl{\"u}ssen - auch ohne Schutzschichten. In diesem Beitrag werden die optischen und strukturellen Eigenschaften von Iridium-Spiegelbeschichtungen, welche mittels Atomlagenabscheidung (ALD) und DC-Magnetron-Sputtern hergestellt wurden, vorgestellt und miteinander verglichen. Die komplexen Brechungsindizes f{\"u}r ALD-erzeugte und gesputterte Iridium-Spiegelbeschichtungen wurden f{\"u}r Wellenl{\"a}ngen von 200 nm bis 20 μm bestimmt, welche nun bereits vorhandene Literaturwerte erg{\"a}nzen.}, subject = {Iridium}, language = {de} } @inproceedings{DoehringStollenwerkSchmittetal.2022, author = {D{\"o}hring, Thorsten and Stollenwerk, Manfred and Schmitt, Paul and Szeghalmi, Adriana}, title = {Environmentally stable iridium mirror coatings for the infrared spectral range}, series = {Proceedings of SPIE}, volume = {2022}, booktitle = {Proceedings of SPIE}, number = {12298}, publisher = {SPIE}, organization = {TH Aschaffenburg}, doi = {https://doi.org/10.1117/12.2632057}, pages = {122980A-1 -- 122980A-08}, year = {2022}, abstract = {Highly reflective metal coatings are essential for numerous optical elements. Established mirror coatings made of silver (Ag) and gold (Au) offer high and broadband self-reflection in the infrared (IR) spectral range but are susceptible to environmental influences and mechanical stress without suitable protective layers. In the long-wavelength spectral range, in particular, the absorption bands of these protective layers partially reduce the high mirror reflectivity again. However, the noble metal iridium (Ir) is hard, extremely dense, and thermally, mechanically, and chemically stable. Iridium provides a similarly high reflectivity in the mid (MIR) and far-infrared (FIR) spectral range, as silver and gold, and high resistance to environmental influences - even without protective layers. In this paper, the different deposition processes, as well as the optical and structural properties of iridium mirror coatings fabricated by atomic layer deposition (ALD) and by magnetron sputtering (MS), are presented and compared with each other. The complex refractive indices for ALD and MS deposited iridium mirror coatings were determined for wavelengths from 200 nm to 20 μm, complementing the existing literature values. We demonstrate that iridium mirror coatings offer a high and broadband reflectivity from the mid to far-infrared spectral range. In contrast to established - protected - silver and gold mirror coatings, the iridium coatings are environmentally durable and thermally stable up to 600 °C, even without protective layers. Therefore, as an interesting mirror coating material, iridium has the potential for special applications in infrared astronomy and probably also for industrial instruments.}, subject = {Iridium}, language = {en} } @misc{DoehringRoedlingKimmeletal.2021, author = {D{\"o}hring, Thorsten and R{\"o}dling, Claudius and Kimmel, Kevin and Zeising, Sebastian and Stadtm{\"u}ller, Johannes and Stollenwerk, Manfred and Verma, Shruti and Rees, Paul}, title = {Optical characterization of reflective coatings for astronomical telescope mirrors}, series = {DGaO Jahrestagung}, volume = {2021}, journal = {DGaO Jahrestagung}, organization = {TH Aschaffenburg}, pages = {1 -- 1}, year = {2021}, abstract = {With ground based optical telescopes astronomers observe celestial objects over a wide spectral range. As usually three or even more reflections at telescope mirrors are involved, good reflection properties of the mirror coatings are important. The aluminum evaporation technique has been - and is still - the standard solution for the reflective coatings of large astronomical mirrors. Such coatings have excellent reflectivity in the ultraviolet and in the visible, but perform poorly in the infrared. Silver is the metal having highest reflectivity for wavelengths longward of 400 nm, but isn´t the best choice for reflectivity in the ultraviolet and for blue light. To avoid degradation by oxidation, durable silver coatings need to be protected by transmitting overcoating layers. In the presented study, different metallic coatings - including unusual ones like sputtered iridium - are characterized to identify a coating that is most suitable for the spectral range from ultraviolet to infrared. Experimental results are compared to simulations based on the complex refractive indices of these materials. Thereby dependence of incidence angle and polarization is also considered.}, subject = {Spiegelteleskop}, language = {en} } @inproceedings{FreudenmannStollenwerkDoehringetal.2021, author = {Freudenmann, Dominic and Stollenwerk, Manfred and D{\"o}hring, Thorsten and Stadtm{\"u}ller, Johannes and Negri, Michele and Lauck, Felix}, title = {Combustion efficiency of iridium coated pellets for environmentally friendly space propulsion}, series = {14th Pico- and Nanosatellite Workshop, W{\"u}rzburg, Germany}, booktitle = {14th Pico- and Nanosatellite Workshop, W{\"u}rzburg, Germany}, year = {2021}, abstract = {Most of the satellite engines still uses critical fuels such as hydrazine, which is chemically aggressive, toxic and carcinogenic. New developments for satellite engines try to avoid such critical propellants. One promising approach is the usage of rocket-grade hydrogen peroxide [H2O2] in mono- and bipropellant driven rocket engines. Catalysts in the rocket engines convert the hydrogen peroxide by an exothermic catalytic reaction; the resulting hot gases oxygen and water vapor provide the thrust. Currently used catalysts are, for example, Al2O3 pellets impregnated with platinum. Within a joint research project of Aschaffenburg University and the German Aerospace Center new catalysts are developed. They consist of ceramic pellets coated with iridium using the magnetron sputtering process. Thereby the surface structure of the iridium layers strongly depends on the used sputtering process conditions [1]. After optimization of the sputtering parameters, it was demonstrated in laboratory experiments that the catalytic effect (measured by the volume of released gas) can be increased by a factor of four compared to platinum impregnated pellets [2]. In first hot firing tests at the test bench complex M11 at the DLR- Institute of Space Propulsion, these new, iridium-based catalysts have been used in a model combustion chamber for hydrogen peroxide decomposition. For this purpose, the reaction chamber was filled with iridium pellets in the high-altitude simulation chamber of the M11.2 test bench. The model chamber was equipped with numerous measuring devices like temperature and pressure sensors (e.g. Tcat, pcat). With the help of the mass flow and the herein obtained data, performance characteristics of the propellant system were accessible. High-concentrated hydrogen peroxide was used in the experiments as monopropellant (~ 87-wt.\% H2O2). During the experiments, the combustion chamber was operated in pulse mode and in continuous mode. Aim of this campaign called MoCa ("Monopropellant Catalytic Demonstrator") is the demonstration of functionality and the performance evaluation of this iridium-based monopropellant system. Recent experimental results will be presented. References: [1] A. B{\"u}ttner et al., Thin Solid Films 2018, 662: 41-46 [2] M. Stollenwerk et al., Journal of Materials Science 2021, 56(16), 9974-9984}, subject = {Satellitentechnik}, language = {de} } @inproceedings{DoehringStadtmuellerStollenwerketal.2021, author = {D{\"o}hring, Thorsten and Stadtm{\"u}ller, Johannes and Stollenwerk, Manfred and Cotroneo, Vincenzo and Pareschi, Giovanni and Gibertini, Eugenio and Magagnin, Luca}, title = {Low-density coatings for enhanced X-ray reflectivity of astronomical telescope mirrors}, series = {DGaO Proceedings}, volume = {2021}, booktitle = {DGaO Proceedings}, number = {122}, publisher = {DGaO}, organization = {TH Aschaffenburg}, issn = {1614-8436}, pages = {1 -- 2}, year = {2021}, abstract = {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.}, subject = {R{\"o}ntgenteleskop}, language = {en} } @inproceedings{DoehringRoedlingKimmeletal.2021, author = {D{\"o}hring, Thorsten and R{\"o}dling, Claudius and Kimmel, Kevin and Zeising, Sebastian and Stadtm{\"u}ller, Johannes and Stollenwerk, Manfred and Verma, Shruti and Rees, Paul}, title = {Optical characterization of reflective coatings for astronomical telescope mirrors}, series = {DGaO Proceedings}, volume = {2021}, booktitle = {DGaO Proceedings}, number = {122}, publisher = {DGaO}, organization = {TH Aschaffenburg}, issn = {1614-8436}, pages = {1 -- 1}, year = {2021}, abstract = {Aluminium evaporation is still the standard solution for reflective coatings of large astronomical mirrors. Silver and gold are also used in specific cases depending on the targeted wavelength. This study characterized different metallic coatings - including unusual ones like sputtered iridium - to identify the most suitable mirror coating for the spectral range from ultraviolet to infrared wavelengths.}, subject = {Spiegelteleskop}, language = {en} } @misc{DoehringStadtmuellerStollenwerketal.2021, author = {D{\"o}hring, Thorsten and Stadtm{\"u}ller, Johannes and Stollenwerk, Manfred and Cotroneo, Vincenzo and Pareschi, Giovanni and Gibertini, Eugenio and Magagnin, Luca}, title = {Low-density coatings for enhanced X-ray reflectivity of astronomical telescope mirrors}, series = {DGaO Jahrestagung}, volume = {2021}, journal = {DGaO Jahrestagung}, organization = {TH Aschaffenburg}, pages = {1 -- 1}, year = {2021}, abstract = {X-ray telescopes usually operate in space and are quite different from astronomical telescopes for visible light. For normal angles of incidence, optical light is reflected on the mirror surface, whereas X-rays are either transmitted or absorbed. However, also high reflectivity X-rays mirrors are possible, when the incident rays direction is almost parallel to the mirror surface. Such grazing incidence mirrors are usually coated with thin layers of precious metals like iridium, gold or platinum, as this result in high X-ray reflectivity. These noble metals offer a wide range of reflection up to high photon energies, but, due to a series of absorption edges, have low reflectivity in the 2 - 4 keV band and below. This contribution presents the development of innovative material combinations based on thin layers of iridium and chromium, followed by an additional layer of carbon-based materials. We also discuss corresponding production methods (like dip coating) for enhanced reflectivity mirror coatings of future X-ray telescopes.}, subject = {R{\"o}ntgenstrahlung}, language = {en} } @inproceedings{StehlikovaDoehringSchaeferetal.2019, author = {Stehlikova, Veronika and D{\"o}hring, Thorsten and Sch{\"a}fer, Tobias and Stollenwerk, Manfred and Friedrich, Peter and Burwitz, Vadim and Hartner, Gisela and Bradshaw, Miranda and Liao, Yingyu and Pelliciari, Carlo}, title = {X-ray reflectivity measurements at chromium-iridium tri-layer coatings}, series = {Proceedings of SPIE}, volume = {2019}, booktitle = {Proceedings of SPIE}, number = {11119}, organization = {Max-Planck-Institut f{\"u}r Extraterrestrische Physik}, doi = {http://dx.doi.org/10.1117/12.2530439}, pages = {111191L-1 -- 111191L-6}, year = {2019}, abstract = {Studying astronomical objects in the X-ray regime, iridium-based layer systems are highly effective reflective materials for telescopes mirrors. Aschaffenburg University and the Czech Technical University in Prague jointly developed stress compensated chromium-iridium coatings. To overcome the disturbing reflectivity reduction of the iridium absorption edge around 2 keV photon energy and improve general reflectivity at lower incident energies, thin overcoat layers of chromium have been applied in addition. Corresponding measurements at several X-ray lines have been performed on these samples at the PANTER test facility of the Max-Planck Institute for extraterrestrial Physics. A part of the experimental results and their comparison with theoretical simulations are presented in this contribution.}, subject = {R{\"o}ntgenastronomie}, language = {en} } @inproceedings{WitteStollenwerk2008, author = {Witte, Gerd and Stollenwerk, Manfred}, title = {Energy saving of cooling water pumps for power plants using adjustable propeller blades}, series = {International Rotating Equipment Conference 2008, D{\"u}sseldorf}, booktitle = {International Rotating Equipment Conference 2008, D{\"u}sseldorf}, year = {2008}, subject = {K{\"u}hlwasseranlage}, language = {en} } @inproceedings{Stollenwerk2005, author = {Stollenwerk, Manfred}, title = {DVD/R 16x high quality mass production - Vortrag auf der Conference Replication Expo, September 2005, Shanghai, China}, year = {2005}, abstract = {Vortrag auf der Conference Replication Expo September 2005, Shanghai, China}, subject = {DVD-R}, language = {en} } @article{MustorphStollenwerkBressau2006, author = {Mustorph, Heinz and Stollenwerk, Manfred and Bressau, Volker}, title = {Current Developments in Optical Data Storage with Organic Dyes}, series = {Angewandte Chemie}, volume = {45}, journal = {Angewandte Chemie}, number = {13}, pages = {2016 -- 2035}, year = {2006}, abstract = {The main motivation for the development of digital data storage has been the improvement in play-back quality and the increase in storage capacity. In 1982 Philips and Sony introduced the first technically and economically successful system based on this—the compact disc (CD) and a compatible player. A very broad diversity of optical data recording formats are available today, and a difference is drawn between prerecorded, recordable, and rewritable media. This Review gives an overview of the systems used, the main features of production, and then concentrates on the properties of the organic dyes that are used in recordable systems. Dyestuffs chemistry has gained the reputation of having become a mature field of activity. Is this prejudice or a justified swan song for dyestuffs chemistry? When applications in optical data storage are considered, it is evident that even today progresses such as CD-R and DVD/R would not be feasible without functional dyes.}, subject = {Optischer Speicher}, language = {en} } @article{DoehringPribullaKomziketal.2019, author = {D{\"o}hring, Thorsten and Pribulla, Theodor and Komzik, Richard and Mann, Michael and Sivanic, Peter and Stollenwerk, Manfred}, title = {Slovak-Bavarian collaboration on the development of telescope instrumentation}, series = {Contributions of the Astronomical Observatory Skalnate Pleso}, volume = {2019}, journal = {Contributions of the Astronomical Observatory Skalnate Pleso}, number = {49 / 2}, pages = {154 -- 158}, year = {2019}, abstract = {Within the project SLOBATCO (Slovak-Bavarian Telescope Collaboration) the Astronomical Institute of the Slovak Academy of Sciences and Aschaffenburg University of Applied Sciences collaborate in the development and commissioning of scientific instrumentation for the new {\O}1.3 m astronomical telescope at the Skalnat{\´e} Pleso observatory. The joint project is funded by the Bavarian Academic Center for Central, Eastern and Southeastern Europe (BAYHOST). Planned technical work packages are targeting the filter wheel software for the VIS camera, additional IR filters, and an upgrade of the mirror coating facility by additional sputtering equipment.}, subject = {Spiegelteleskop}, language = {en} } @misc{MannDoehringPribullaetal.2019, author = {Mann, Michael and D{\"o}hring, Thorsten and Pribulla, Theodor and Komzik, Richard and Sivanic, Peter and Stollenwerk, Manfred}, title = {Power quality evaluation for observatories}, editor = {Skopal, Augustin}, organization = {TH Aschaffenburg}, pages = {1}, year = {2019}, abstract = {Within the project SLOBATCO the question did arise, to what extend observatories have to rely on adequate power quality, e.g. the perfect sinusoidal shape of supply voltage and current, in order to ensure safe operation and accurate measurement results. International power quality standards are put in perspective with requirement specifications. Telescope operators indicate partial or total loss of function of measurement instruments. Measurements conducted during SLOBATCO project substantiate the need for power quality measurement campaigns.}, subject = {Sternwarte}, language = {en} } @inproceedings{Stollenwerk2006, author = {Stollenwerk, Manfred}, title = {The Energy Market within the next 20 years}, series = {6 MEAI, Wien}, booktitle = {6 MEAI, Wien}, year = {2006}, subject = {Energiemarkt}, language = {en} } @article{StollenwerkGattinger2005, author = {Stollenwerk, Manfred and Gattinger, P.}, title = {Process challenges of high Speed DVD/R manufacturing}, series = {One to One magazine}, volume = {2005}, journal = {One to One magazine}, number = {March}, pages = {55 -- 58}, year = {2005}, subject = {DVD-R}, language = {en} } @inproceedings{Stollenwerk2005, author = {Stollenwerk, Manfred}, title = {Efficient DVD/R Production}, series = {Optical Disc Seminar Asia ODSA, Teipei}, booktitle = {Optical Disc Seminar Asia ODSA, Teipei}, year = {2005}, subject = {DVD-R}, language = {en} } @misc{Stollenwerk2005, author = {Stollenwerk, Manfred}, title = {Die optische Datenspeicherung auf CD und DVD}, series = {{\"U}bersichtsvortrag auf der Fachtagung „Die Kunststoffoberfl{\"a}che" des S{\"u}ddeutschen Kunststoffzentrums W{\"u}rzburg}, journal = {{\"U}bersichtsvortrag auf der Fachtagung „Die Kunststoffoberfl{\"a}che" des S{\"u}ddeutschen Kunststoffzentrums W{\"u}rzburg}, year = {2005}, abstract = {Vortrag}, subject = {Optischer Speicher}, language = {de} } @misc{Stollenwerk2003, author = {Stollenwerk, Manfred}, title = {Basics of Recordable Media Production}, series = {Vortrag auf dem "International Recordable Media Technology Seminar", Dubai}, journal = {Vortrag auf dem "International Recordable Media Technology Seminar", Dubai}, year = {2003}, abstract = {Vortrag}, subject = {CD-R}, language = {en} } @misc{Stollenwerk2003, author = {Stollenwerk, Manfred}, title = {Correlation of DVD-Recordable Disc Performance and Process Parameters}, series = {Vortrag auf der „Replication EXPO 2003", Shanghai, China}, journal = {Vortrag auf der „Replication EXPO 2003", Shanghai, China}, year = {2003}, abstract = {Vortrag}, subject = {DVD-R}, language = {en} } @misc{Stollenwerk1998, author = {Stollenwerk, Manfred}, title = {CD-Recordable CD-Rewriteable}, series = {Vortrag auf der REPLItech Summit (Conference) S{\~a}o Paulo, Brazil}, journal = {Vortrag auf der REPLItech Summit (Conference) S{\~a}o Paulo, Brazil}, year = {1998}, abstract = {Vortrag}, subject = {CD-R}, language = {en} } @article{StollenwerkAlexanderShortetal.1996, author = {Stollenwerk, Manfred and Alexander, Morgan and Short, Robert and Jones, Frank and Zabold, Jochen and Michaeli, Walter}, title = {An X-ray photoelectron spectroscopic investigation into the chemical structure of deposits formed from hexamethyldisiloxane/ oxygen plasmas}, series = {Journal of Materials Science}, volume = {31}, journal = {Journal of Materials Science}, number = {7}, pages = {1879 -- 1885}, year = {1996}, abstract = {The effect of oxygen addition to microwave-sustained plasmas of hexamethyldisiloxane (HMDSO) has been investigated. Attention was directed to the solid products formed on aluminium substrates (plasma deposits). To enable a quantitative analysis of these, X-ray photoelectron spectroscopy (XPS) of standard silicon-containing materials was carried out. When suitable charge correction is applied to the XP spectra of HMDSO/O2 plasma deposits, a number of very clear trends emerge. From changes in elemental composition, core line binding energies (Si2p, C 1s, and O 1s) and widths, we show how oxygen addition to the plasma affects the chemical nature of the plasma deposit. The data reported also provide (some limited) information on the reactions taking place in the plasma.}, subject = {Photoelektronenspektroskopie}, language = {en} } @article{AlexanderShortJonesetal.1995, author = {Alexander, Morgan and Short, Robert and Jones, Frank and Stollenwerk, Manfred and Mathar, Gerd and Zabold, Jochen and Michaeli, Walter}, title = {The heterogeneous nature of deposits from hexamethyldisiloxane/oxygen plasmas}, series = {Ceramic films and coatings}, volume = {1995}, journal = {Ceramic films and coatings}, number = {54}, pages = {87 -- 99}, year = {1995}, subject = {Hexamethyldisiloxan}, language = {en} } @book{WoltersStollenwerkBerthold1994, author = {Wolters, Leo and Stollenwerk, Manfred and Berthold, J.}, title = {Die Plasmatechnologie und ihre Einsatzm{\"o}glichkeiten}, address = {Aachen}, year = {1994}, subject = {Plasmatechnik}, language = {de} } @misc{MichaeliStollenwerkZell1994, author = {Michaeli, Walter and Stollenwerk, Manfred and Zell, Harald}, title = {Variation der Oberfl{\"a}chenspannung bei fl{\"a}chigen Substraten und Verst{\"a}rkungsfasern sowie der Einfluß auf die Faser/Matrix-Haftung bei faserverst{\"a}rkten Kunststoffen}, year = {1994}, subject = {Faserverst{\"a}rkter Kunststoff}, language = {de} } @inproceedings{MichaeliStollenwerkSteinkampetal.1994, author = {Michaeli, Walter and Stollenwerk, Manfred and Steinkamp, F. and Zell, Harald}, title = {Plasmabehandlung von Glasfasern f{\"u}r faserverst{\"a}rkte Kunststoffe}, series = {6. Bundesdeutsche Fachtagung Plasmatechnologie, Wuppertal}, booktitle = {6. Bundesdeutsche Fachtagung Plasmatechnologie, Wuppertal}, year = {1994}, subject = {Faserverst{\"a}rkter Kunststoff}, language = {de} } @misc{StollenwerkZell1994, author = {Stollenwerk, Manfred and Zell, Harald}, title = {Veredeln von Kunststoffoberfl{\"a}chen mittels Mikrowellenplasmapolymerisation}, year = {1994}, subject = {Plasmapolymerisation}, language = {de} } @article{MichaeliTelgenbuescherStollenwerketal.1994, author = {Michaeli, Walter and Telgenb{\"u}scher, Klaus and Stollenwerk, Manfred and Mathar, Gerd and Zell, Harald}, title = {Plasmapolymerisierte Schichten: Neue Vielfalt der Funktionen}, series = {Schweizer Maschinenbau}, volume = {1994}, journal = {Schweizer Maschinenbau}, number = {41}, pages = {90 -- 93}, year = {1994}, subject = {Plasmapolymerisation}, language = {de} } @misc{Stollenwerk1993, author = {Stollenwerk, Manfred}, title = {Das Abscheiden von kratzfesten, hydrophilen und hydrophoben Schichten mittels Plasmapolymerisation}, year = {1993}, subject = {Plasmapolymerisation}, language = {de} } @article{LeiberMichaeliTelgenbuescheretal.1993, author = {Leiber, J{\"o}rn and Michaeli, Walter and Telgenb{\"u}scher, Klaus and Stollenwerk, Manfred}, title = {UV protecting layers on PVC made by plasma polymerization}, series = {Journal of Vinyl Technology}, volume = {15}, journal = {Journal of Vinyl Technology}, number = {2}, pages = {57 -- 61}, year = {1993}, subject = {Plasmapolymerisation}, language = {en} } @article{MichaeliStollenwerkTelgenbuescher1993, author = {Michaeli, Walter and Stollenwerk, Manfred and Telgenb{\"u}scher, Klaus}, title = {Plasmabehandlung - Ein umweltfreundliches Verfahren zur Oberfl{\"a}chenvorbehandlung und -reinigung}, series = {Scope-Journal Special}, volume = {1993}, journal = {Scope-Journal Special}, number = {16}, pages = {21 -- 23}, year = {1993}, subject = {Plasmatechnik}, language = {de} } @misc{ZellTelgenbuescherStollenwerk1993, author = {Zell, Harald and Telgenb{\"u}scher, Klaus and Stollenwerk, Manfred}, title = {Kratzfeste Beschichtungen von Kunststoffen mittels Plasmapolymerisation}, year = {1993}, subject = {Plasmapolymerisation}, language = {de} } @inproceedings{MichaeliLeiberTelgenbuescheretal.1993, author = {Michaeli, Walter and Leiber, J{\"o}rn and Telgenb{\"u}scher, Klaus and Stollenwerk, Manfred}, title = {Plasma polymerization in automotive industries - A possibility for the reduction of permeation in plastic fuel tanks}, series = {26th intern. Symposium on Automotive Technology and Automation, Aachen Tagungsband}, booktitle = {26th intern. Symposium on Automotive Technology and Automation, Aachen Tagungsband}, pages = {469 -- 476}, year = {1993}, subject = {Plasmapolymerisation}, language = {en} } @misc{Stollenwerk1993, author = {Stollenwerk, Manfred}, title = {Oberfl{\"a}chenmodifikation mittels Plasmatechnik}, year = {1993}, subject = {Plasmatechnik}, language = {de} } @article{MeyerHardtdegenGruetzmacheretal.1992, author = {Meyer, R. and Hardtdegen, Hilde and Gr{\"u}tzmacher, Detlev and Carius, R. and Stollenwerk, Manfred and Balk, Peter}, title = {Optical and structural properties of MOVPE grown GaxIn1-xAs/InP strained multiple quantum well structures}, series = {Journal of Electronic Materials}, volume = {21}, journal = {Journal of Electronic Materials}, number = {3}, pages = {293 -- 298}, year = {1992}, abstract = {This paper presents a study of the structural and optical properties of strained GaInAs/ InP multiple quantum well (MQW) structures fabricated by LP-MOVPE. The composition of the Ga x In1-x As films ranged fromx = 0.17 tox = 1.0 and was determined by sputtered neutral mass spectrometry (SNMS) on thick layers. The structures of the MQW samples with well widths from 1.5 to 5 nm were investigated by high resolution x-ray diffraction (HR-XRD). Simulations of the diffraction patterns showed that transition layers of approximately 2 monolayer (ML) thickness with high lattice mismatch exist at the interfaces. Photoluminescence (PL) measurements indicate well widths of a multiple of a monolayer with local variations of one monolayer. The PL peak energies vary smoothly with the Ga concentration. These results were confirmed by optical absorption measurements.}, subject = {Galliumarsenid}, language = {en} } @article{OschinowoForchelDreybrodtetal.1992, author = {Oschinowo, John and Forchel, Alfred and Dreybrodt, J{\"o}rg and Emmerling, Monika and Gyuro, Imre and Speier, Peter and Gr{\"u}tzmacher, Detlev and Stollenwerk, Manfred}, title = {Lateral thermal stability modulation for the definition of InGaAs/InP wires}, series = {Microelectronic Engineering}, volume = {17}, journal = {Microelectronic Engineering}, number = {1-4}, pages = {505 -- 508}, year = {1992}, abstract = {We have investigated a novel technique for the definition of semiconductor wires. By the selective local removal of the InP top barrier layer wire patterns in which the top material varies between InP and InGaAs are formed from an InGaAs/InP quantum well. In a subsequent annealing step the top InGaAs layer shows substantially stronger interdiffusion than the InP covered regions (wires). By using luminescence spectroscopy we show that this defectfree enhanced interdiffusion can be used to obtain a lateral energy barrier.}, subject = {Indiumarsenid}, language = {en} } @article{WolterSchwedlerGallmannetal.1991, author = {Wolter, Karl and Schwedler, Ralf and Gallmann, B. and Jaekel, Christian and Stollenwerk, Manfred and Camassel, Jean and Laurenti, Jean Pierre}, title = {Optical characterization of strained InGaAs/InP quantum well structures}, series = {Microelectronic Engineering}, volume = {15}, journal = {Microelectronic Engineering}, number = {1-4}, pages = {593 -- 596}, year = {1991}, abstract = {The effects of strain on the optical properties ofmultiple-quantum well structures grown by low pressure metal organic vapor phase epitaxy have been investigated by photoluminescence spectroscopy. The investigated composition range is varied between 0.17 ≤ xGa ≤ 1.00. Sputtered neutrals mass spectroscopy has been used to calibrate the growth interpolated nominal compositions. Distinct peaks from monolayer variations of well thickness are observed from all samples. The analysis of the PL-spectra leads to the assumption of an intermediate layer of InAs0.65P0.35 at the InP to In1-ϰGaχAs(lower) interface.}, subject = {Indiumarsenid}, language = {en} } @article{SchwedlerWolterGallmannetal.1991, author = {Schwedler, Ralf and Wolter, Karl and Gallmann, B. and Gr{\"u}tzmacher, Detlev and Stollenwerk, Manfred and Kurz, H.}, title = {Optical characterization of In-rich strained In1-xGaxAs/InP single- and multiple-quantum-wells}, series = {Materials Science and Engineering: B}, volume = {9}, journal = {Materials Science and Engineering: B}, number = {1-3}, pages = {297 -- 300}, year = {1991}, abstract = {We report on the photoluminescence spectroscopy of a large set of strained In1-xGaxAs/InP quantum well structures grown by low pressure metallo-organic vapour phase epitaxy. Distinct peaks from monolayer steps are observed in all samples. For the first time, data on indium-rich In1-xGaxAs/InP structures with complementary gallium contents as low as xGa = 0.07 and xGa = 0.11 are reported. The sample quality appears independent of the number of quantum wells stacked in the structure. With decreasing gallium content, a decrease in luminescence intensity is observed, which is related to an increase in the number of non-radiative recombination centres with respect to lattice-matched samples.}, subject = {Photolumineszenzspektroskopie}, language = {en} } @inproceedings{MahlzahnHeukenGruetzmacheretal.1991, author = {Mahlzahn, Erik and Heuken, Michael and Gr{\"u}tzmacher, Detlev and Stollenwerk, Manfred and Heime, Klaus}, title = {Advanced InGaAs/InP p-type sydomorphic MODFET}, series = {Proceedings of the SPIE}, volume = {1362}, booktitle = {Proceedings of the SPIE}, pages = {199 -- 204}, year = {1991}, subject = {Indiumarsenid}, language = {en} } @inproceedings{GladeHergethStollenwerketal.1990, author = {Glade, M. and Hergeth, J. and Stollenwerk, Manfred and Gr{\"u}tzmacher, Detlev and Balk, Peter}, title = {Effects of zinc diffusion during MOPVE on performance of InP/InGaAsP double heterostructure lasers}, series = {Proceedings of the 17th International Symposium of GaAs and related Compounds, Jersey, UK}, booktitle = {Proceedings of the 17th International Symposium of GaAs and related Compounds, Jersey, UK}, pages = {579 -- 584}, year = {1990}, subject = {Indiumphosphid}, language = {en} } @inproceedings{MahlzahnHeukenGruetzmacheretal.1990, author = {Mahlzahn, Erik and Heuken, Michael and Gr{\"u}tzmacher, Detlev and Stollenwerk, Manfred and Heime, Klaus}, title = {High mobility and high sheet density p-type pseudomorphic MODFET}, series = {Proceedings of the 17th International Symposium of GaAs and related Compounds, Jersey, UK}, booktitle = {Proceedings of the 17th International Symposium of GaAs and related Compounds, Jersey, UK}, pages = {579 -- 584}, year = {1990}, subject = {HEMT}, language = {en} } @article{AlexanderShortJonesetal.1996, author = {Alexander, Morgan and Short, Robert and Jones, Frank and Stollenwerk, Manfred and Mathar, Gerd and Zabold, Jochen and Michaeli, Walter}, title = {An XPS investigation into the chemical structure of deposits formed from hexamethyldisiloxane/oxgen plasmas}, series = {Journal of Materials Science}, volume = {31}, journal = {Journal of Materials Science}, pages = {1879 -- 1885}, year = {1996}, subject = {Hexamethyldisiloxan}, language = {en} } @article{MichaeliStollenwerkTelgenbuescheretal.1993, author = {Michaeli, Walter and Stollenwerk, Manfred and Telgenb{\"u}scher, Klaus and Leiber, J{\"o}rn}, title = {Vorbehandeln und Beschichten von Kunststoffteilen in PE-CVD-Anlagen}, series = {Maschinenmarkt}, volume = {99}, journal = {Maschinenmarkt}, number = {29}, pages = {42 -- 48}, year = {1993}, subject = {Kunststoffprodukt}, language = {de} } @article{MichaeliTelgenbuescherLeiberetal.1992, author = {Michaeli, Walter and Telgenb{\"u}scher, Klaus and Leiber, J{\"o}rn and Stollenwerk, Manfred}, title = {Plasmapolymerisation zur Veredelung von Kunststoffoberfl{\"a}chen}, series = {D{\"u}nne Schichten}, volume = {1992}, journal = {D{\"u}nne Schichten}, number = {3}, pages = {34 -- 38}, year = {1992}, subject = {Plasmapolymerisation}, language = {de} } @article{MichaeliLeiberTelgenbuescheretal.1992, author = {Michaeli, Walter and Leiber, J{\"o}rn and Telgenb{\"u}scher, Klaus and Stollenwerk, Manfred}, title = {Plasmapolymerisation: Kunststoffe beschichten}, series = {Industrieanzeiger}, volume = {1992}, journal = {Industrieanzeiger}, number = {43}, pages = {58 -- 60}, year = {1992}, subject = {Plasmapolymerisation}, language = {de} } @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} }