TY - GEN A1 - Döhring, Thorsten A1 - Stieglitz, Veronika A1 - Burwitz, Vadim A1 - Hartner, Gisela A1 - Müller, Thomas A1 - Schmidt, Thomas A1 - Rukdee, Surangkhana A1 - Friedrich, Peter A1 - Sahin, Fatih A1 - HUdec, Rene T1 - Charakterisierung von Weitwinkel-Röntgenteleskopen in der Testanlage PANTER T2 - DGaO Jahrestagung N2 - Im Rahmen einer bayerisch-tschechischen Kooperation entstanden zwei mechanisch baugleiche Röntgenteleskope, bestückt mit Gold- und Iridium-beschichteten Planspiegeln. Die Charakterisierung der nach dem ägyptischen Gott HORUS benannten Teleskope erfolgte an der Röntgentestanlage PANTER des Max-Plack-Instituts für extraterrestrische Physik. Diese Vakuum-Testanlage simuliert parallel auf die Teleskope einfallendes Sternenlicht, wobei hier die Strahlung aus einer Röntgenquelle in 120 Metern Abstand stammt. Die Messungen selbst fanden in einer daran angebauten 12 Meter langen Testkammer von 3,5 Metern Durchmesser statt. Im März 2021 sahen die HORUS-Teleskope zum erstem Mal Röntgenlicht. Während der Testkampagne von ca. 54 Stunden Dauer wurden 536 Einzelmessungen an den beiden Teleskopen durchgeführt, bei denen Photonenenergien und Einfallswinkel variiert wurden. Von einer empfindlichen CCD-Kamera, einem Prototyp der eROSITA-Satellitenkamera, wurden hierbei insgesamt 11.153.574 Röntgenphotonen individuell detektiert, analysiert und digital verarbeitet. Die beiden Weitwinkel-Röntgenteleskope haben eine Winkelauflösung von circa 4 Bogenminuten und eine Brennweite von rund zwei Metern. N2 - Poster KW - Röntgenstrahlung KW - Spiegel KW - Teleskop KW - Satellit KW - Iridium KW - Röntgenstrahlung KW - Spiegelteleskop Y1 - 2021 UR - https://dgao.de/jahrestagung/ VL - 2021 SP - 1 EP - 1 ER - TY - GEN A1 - Döhring, Thorsten A1 - Stadtmüller, Johannes A1 - Stollenwerk, Manfred A1 - Cotroneo, Vincenzo A1 - Pareschi, Giovanni A1 - Gibertini, Eugenio A1 - Magagnin, Luca T1 - Low-density coatings for enhanced X-ray reflectivity of astronomical telescope mirrors T2 - DGaO Jahrestagung N2 - 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. N2 - Poster KW - X-ray KW - mirror KW - coating KW - iridium KW - satellite KW - Röntgenstrahlung KW - Spiegelteleskop Y1 - 2021 UR - https://dgao.de/jahrestagung/ VL - 2021 SP - 1 EP - 1 ER - TY - CHAP A1 - Schwarz, Simon A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Current results on laser-based production of complex optics in glass T2 - 10. Wetzlarer Herbsttagung "Moderne Optikfertigung", 29. - 30. September 2020, Wetzlar KW - Laserbearbeitung KW - Fertigungstechnik Y1 - 2020 ER - TY - GEN A1 - Schwarz, Simon A1 - Hellmann, Ralf T1 - Rapid laser fabrication of complex glass optics T2 - International Research Days N2 - Poster KW - Laserbearbeitung Y1 - 2021 ER - TY - JOUR A1 - Zettl, Julian A1 - Klar, Maximilian A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Laser turning with ultrashort laser pulses JF - Journal of Manufacturing Processes N2 - We report on a comprehensive micromachining study of rotationally symmetric parts using femtosecond laser. A laser turning process with tangential impingement of the laser radiation complemented by a trepanning optics is implemented as to accomplish a true laser lathe micromachining approach. With the objective of optimized ablation rate and reduced surface roughness, the influence of pulse energy, feed rate, trepanning diameter and angular beam incidence, respectively, is investigated for processing stellite rods. We find the smallest feasible feature sizes of 8.5 μm in diameter and smoothest surfaces with an arithmetic average of the roughness profile as low as 0.18 μm. The surface roughness, however, appears to be limited by the occurrence of laser induced periodic surface structures provoked by the femtosecond laser radiation. Furthermore, the variation of the fluence in accordance to the incidence on a curved surface is discussed and the heat input into the material is examined through a longitudinal cross section. KW - Ultrashort laser pulses KW - Turning KW - Ablation rate KW - Tangential processing KW - Trepanning optic KW - Ultrakurzer Lichtimpuls KW - Laserbearbeitung KW - Mikrobearbeitung KW - Femtosekundenlaser Y1 - 2021 U6 - https://doi.org/10.1016/j.jmapro.2021.06.025 VL - 2021 IS - 68 SP - 1562 EP - 1568 ER - TY - JOUR A1 - Zettl, Julian A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Tangential Laser Turning of Fused Silica Using Ultra-short Laser Pulses JF - Journal of Laser Micro/Nanoengineering N2 - Laser turning with ultra-short laser pulses provides the possibility of manufacturing rotationally symmetric geometries, even of hard to machine materials as fused silica, down to a micrometer scale. In this laser micro machining approach, the laser beam is oriented perpendicularly to the rotational axis and tangentially to the material, whereas the target geometry is realized by moving the constantly rotating specimen according to the specified geometry under the focused laser spot. Due to the fric-tion-less laser ablation it is possible to realize a turning process in fused silica without the use of a contacting tool and therefore without causing mechanical tensions in the work piece. The processing head focuses the laser to a calculated spot size of 18 μm in diameter and the applied processing gas pressure assists in removing the ablated material. In this study, femto-second laser turning of fused silica with a diameter of 3.7 mm is investigated. The influence of the applied pulse energy is stated and the use of a trepanning optic during the turning process is characterized. Furthermore, compre-hensive parameter studies in order to optimize roughness and to find the maximum achievable abla-tion rate are shown. Limited by the mechanical speed of the rotational axis, the highest feasible abla-tion rate is 19.5 mm³/min. A roughness of Ra 0.65 μm are demonstrated. KW - Ultra-short Laser Pulses KW - Laser Turning KW - Fused Silica KW - Ablation Rate KW - Process Efficiency KW - Laserbearbeitung KW - Mikrobearbeitung KW - Quarzglas KW - Ultrakurzer Lichtimpuls Y1 - 2021 U6 - https://doi.org/10.2961/jlmn.2021.01.2008 VL - 16 IS - 1 SP - 42 EP - 46 ER - TY - JOUR A1 - Adelmann, Benedikt A1 - Schleier, Max A1 - Hellmann, Ralf T1 - Laser Cut Interruption Detection from Small Images by Using Convolutional Neural Network JF - Sensors KW - laser cutting KW - remote sensing KW - convolutional neural network KW - cut interruption KW - image processing KW - Laserschneiden KW - Neuronales Netz Y1 - 2021 UR - https://doi.org/10.3390/s21020655 U6 - https://doi.org/10.3390/s21020655 VL - 2021 IS - 21(2) SP - 655 EP - 655 ER - TY - JOUR A1 - Adelmann, Benedikt A1 - Hellmann, Ralf T1 - Simultaneous Burr and Cut Interruption Detection during Laser Cutting with Neural Networks JF - Sensors KW - laser cutting KW - quality monitoring KW - artificial neural network KW - burr formation KW - cut interruption KW - Laserschneiden KW - Neuronales Netz Y1 - 2021 UR - https://doi.org/10.3390/s21175831 U6 - https://doi.org/10.3390/s21175831 VL - 2021 IS - 21 SP - 5831 EP - 5831 ER - TY - JOUR A1 - Schleier, Max A1 - Adelmann, Benedikt A1 - Esen, Cemal A1 - Glatzel, Uwe A1 - Hellmann, Ralf T1 - Development and evaluation of an image processing algorithm for monitoring fiber laser fusion cutting by a high-speed camera JF - Journal of Laser Applications KW - Laser cutting KW - Image processing KW - Optical imaging KW - Image sensors KW - Laser applications KW - Faserlaser KW - Laserschneiden KW - Bildverarbeitung Y1 - 2021 UR - https://doi.org/10.2351/7.0000391 U6 - https://doi.org/10.2351/7.0000391 VL - 2021 IS - 33 SP - 032004 EP - 032004 ER - TY - CHAP A1 - Schwarz, Simon A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - UKP-Prozess mit anschließendem CO2-Laserpolieren zur Fertigung komplexer Optiken T2 - 10. Workshop Laserbearbeitung von Glaswerkstoffen KW - Linse KW - Array KW - Laserbearbeitung KW - Ultrakurzzeitlaser KW - Kohlendioxidlaser Y1 - 2020 ER - TY - JOUR A1 - Schwarz, Simon A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Ultrashort pulsed laser backside ablation of fused silica JF - Optics Express KW - Femtosekundenlaser KW - Quarzglas KW - Mikrobearbeitung Y1 - 2021 VL - 29 IS - 15 SP - 23477 EP - 23486 ER - TY - JOUR A1 - Schwarz, Simon A1 - Götzendorfer, Babette A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Compact Beam Homogenizer Module with Laser-Fabricated Lens-Arrays JF - applied sciences KW - Femtosekundenlaser KW - Linse KW - Array Y1 - 2021 VL - 2021 IS - 11 SP - 1018 EP - 1018 ER - TY - JOUR A1 - Schwarz, Simon A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Enhanced ablation efficiency using GHz bursts in micromachining fused silica JF - Optics Letters KW - Fräsen KW - Mikrobearbeitung KW - Quarzglas KW - Femtosekundenlaser Y1 - 2021 VL - 46 IS - 2 SP - 282 EP - 285 ER - TY - JOUR A1 - Götzendorfer, Babette A1 - Kirchgässner, Hannah A1 - Hellmann, Ralf T1 - Tunable, Anisotropic Permeability and Spatial Flow of SLM Manufactured Structures JF - Materials KW - Permeabilität KW - Selektives Laserschmelzen Y1 - 2021 U6 - https://doi.org/doi.org/10.3390/ma14185205 VL - 2021 IS - 14 SP - 5205 EP - 5220 ER - TY - JOUR A1 - Götzendorfer, Babette A1 - Mohr, Thomas A1 - Hellmann, Ralf T1 - Hybrid Approaches for Selective Laser Sintering by Building on Dissimilar Materials JF - Materials KW - Laserstrahlsintern Y1 - 2020 U6 - https://doi.org/doi.org/10.3390/ma13225285 VL - 2020 IS - 13 (22) SP - 5285 EP - 5296 ER - TY - JOUR A1 - Büdel, Johannes A1 - Teigelkötter, Johannes ED - Schäfer, Heinz T1 - Doppelzweipunktwechselrichter für Elektrofahrzeuge - Systemeigenschaften und Steuerung JF - Elektrische Antriebstechnologie für Hybrid- und Elektrofahrzeuge N2 - Im vorliegenden Beitrag wird die Topologie des Doppelzweipunktwechselrichters für die Anwendung in Elektrofahrzeugen vorgestellt. Dazu werden zunächst der Schaltungsaufbau und die spezifischen Schaltungseigenschaften näher erläutert. Anschließend werden relevante Vorteile dieser Topologie für die Anwendung in Elektrofahrzeugen dargestellt. Für die Kombination unterschiedlicher Energiequellen mit Hilfe des Doppelzweipunktwechselrichters werden geeignete Steuerungsstrategien präsentiert und anhand von realen Messungen am Systemprüfstand verifiziert. Mit dem Vorgestellten Verfahren kann die Leistungsaufteilung auf die beiden Energiespeicher und deren Energieaustausch untereinander mit hohem Freiheitsgrad gesteuert werden. KW - Elektrofahrzeug KW - Wechselrichter Y1 - 2019 VL - 2019 IS - 149 SP - 114 EP - 127 ER - TY - CHAP A1 - Büdel, Johannes A1 - Teigelkötter, Johannes A1 - Stock, Alexander A1 - Kuhlmann, Kai A1 - Lang, Klaus A1 - Ott, Patrick T1 - Testing of High-Power Traction Batteries T2 - SMSI 2021 - System of Units and Metreological Infrastructure N2 - Electric drives in road vehicles with a battery as energy storage are about to be introduced to the mass market. In order to guarantee the quality and operational safety of battery-powered vehicles, considerable efforts must be made by car manufacturers and their suppliers. Since the properties of the batteries significantly determine the performance of the vehicles, special test benches with precise measuring systems are required for the accurate determination of the battery properties. The safety devices of the traction batteries must also be tested on high-performance test benches. In this paper the necessary test benches and the corresponding measuring systems are presented. Estimations of the measurement uncertainty and possibilities to increase measurement accuracy are presented. KW - Traktionsbatterie KW - Elektrofahrzeug Y1 - 2021 UR - https://www.ama-science.org/proceedings/details/4061 SN - 978-3-9819376-4-0 U6 - https://doi.org/10.5162/SMSI2021/C7. SP - 294 EP - 295 ER - TY - CHAP A1 - Büdel, Johannes A1 - Teigelkötter, Johannes A1 - Stock, Alexander A1 - Herkommer, Christian A1 - Kuhlmann, Kai T1 - High Dynamic Power Balancing for Dual Two-Level Inverters during High-Speed Machine Operation T2 - 2020 22nd European Conference on Power Electronics and Applications (EPE'20 ECCE Europe) N2 - This paper aims to present optimized square-wave modulation strategies for the dual two-level inverter, fed by two separate and galvanically isolated energy sources, to balance and control the energy distribution of both inverter systems. Especially for high-speed operation, the methods keep the machine in the required state while decreasing the switching operations to a minimum. Method one aims to compensate voltage fluctuations of variable DC-link voltages, while the second method ensures a symmetrical power distribution for the two inverter systems. In addition, both methods offer the possibility of adapting the amplitude of the usually fixed fundamental load voltage during square-wave modulation. KW - Wechselrichter Y1 - 2020 UR - https://ieeexplore.ieee.org/document/9215695 SN - 978-1-7281-9807-1 U6 - https://doi.org/10.23919/EPE20ECCEEurope43536.2020.9215695 ER - TY - CHAP A1 - Büdel, Johannes A1 - Teigelkötter, Johannes A1 - Stock, Alexander T1 - Optimized Dual Two-Level Inverter for Safe and Reliable Operation of Machines with Superconductive Stator Windings T2 - 2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe) N2 - This paper aims to present an optimized inverter topology, based on the dual two-level inverter, for feeding an open-end winding electrical machine with superconductive stator windings and a superconductive rotor. In order to achieve a high torque density, the stator windings are built of several superconducting tapes being in parallel. One inverter of the dual two-level inverter is equipped with powerful IGBT semiconductors and supplies the machine with energy. The second inverter is a low voltage MOSFET inverter that monitors the superconductor resistance (quench detection) and balances the current on the parallel superconductive tapes for guaranteeing an optimum operation with respect to the superconductive losses. KW - Elektrische Maschine KW - Wechselrichter Y1 - 2019 UR - https://ieeexplore.ieee.org/document/8915524 SN - 978-1-7281-2361-5 U6 - https://doi.org/10.23919/EPE.2019.8915524 ER - TY - CHAP A1 - Stock, Alexander A1 - Teigelkötter, Johannes A1 - Staudt, Stefan A1 - Büdel, Johannes T1 - Highly Dynamic Calculation of Power Quantities and Further Analysis of Inverter-Fed Machines T2 - 2018 20th European Conference on Power Electronics and Applications (EPE'18 ECCE Europe) N2 - In this contribution, a highly dynamic calculation method of power quantities and additional electrical quantities, such as RMS values and fundamental waveforms, is presented. Typically, these quantities are calculated periodically based on the fundamental cycle of the electrical voltages and currents. Hence, they are well defined during steady state conditions for ideal periodical waveforms. During dynamic balancing processes, electrical signals are non-periodic. In a strict sense, the fundamental cycle-based definitions, which are well known from the literature, are not valid for these transient signals. However, this paper presents a novel definition for the calculation of cycle-based quantities based on the switching cycle of the inverter output voltages. This definition delivers instantaneous results during transient balancing processes, whereby it approximates the conventional fundamental cycle-based definitions during the steady state. KW - Elektrische Maschine KW - Umrichter Y1 - 2018 UR - https://ieeexplore.ieee.org/document/8515600 SN - 978-1-5386-4145-3 ER -