@inproceedings{PareschiCivitaniSironietal.2019, author = {Pareschi, Giovanni and Civitani, Marta Maria and Sironi, Giorgia and Yang, Yang and Cotroneo, Vincenzo and Valsecchi, Giuseppe and Magagnin, Luca and D{\"o}hring, Thorsten and Bradshaw, Miranda and Burwitz, Vadim and Pelliciari, Carlo}, title = {Reflectivity-enhancement at low x-ray energies in astronomical telescopes using low-density overcoatings: alternative materials and deposition methods}, series = {Proceedings of SPIE}, volume = {2019}, booktitle = {Proceedings of SPIE}, number = {11119}, publisher = {SPIE}, organization = {Osservatorio Astronomico di Brera}, doi = {https://doi.org/10.1117/12.2532392}, pages = {11119OS-1 -- 11119OS-13}, year = {2019}, abstract = {Low density overcoatings (mainly based on materials containing Carbon) onto usual high-density coatings (based i.e. on materials like e.g. like Ir, Au or Pt) have been proposed since many years ago in order to enhance the X- ray reflectivity at low energy (between 0.5 and 4 keV) of X-ray astronomical optics. The trick is to make use of the total reflection from the thin low-density material (which does not suffer much the photoelectric absorption) at low X-ray energies; the reflection of photons at higher energies (< 4 keV) occurs thanks to the much denser material under the overcoating. For several future projects, like e.g. ATHENA, LYNX and eXTP, it is foreseen the use of low-density overcoatings that will importantly increase the effective area at low X-ray energies. In this paper we will introduce the use of overcoatings based on materials different from the usual ones considered so far like C, B4C and SiC. In particular, we will discuss about a novel approach based on the use of thin layer of a Carbon-like materials deposited using a dip coating method. A possible combination with an intermediate thin layer of Chromium deposited e.g. via sputtering onto the usual high density material (Ir, Au or Pt) before the application of the Carbon-like material is also considered in the study, because it can further greatly enhance the soft X-ray effective area of future X-ray telescopes.}, subject = {R{\"o}ntgenteleskop}, language = {en} } @misc{GiovanniDoehringValsecchietal.2019, author = {Giovanni, Pareschi and D{\"o}hring, Thorsten and Valsecchi, Guiseppe and Magagnin, Luca and Bradshaw, Miranda and Burwitz, Vadim and Civitani, Marta Maria and Cotroneo, Vincenzo and Gibertini, Eugenio and Pelliciari, Carlo and Sironi, Giorgia and Yang, Yang}, title = {Enhancing the ATHENA effective area at low x-ray energies with unconventional overcoatings}, series = {Proceedings of the X-RAY ASTRONOMY 2019 conference}, volume = {2019}, journal = {Proceedings of the X-RAY ASTRONOMY 2019 conference}, organization = {Istituto Nazionale di Astrofisica}, pages = {1 -- 1}, year = {2019}, abstract = {Low density overcoatings (mainly based on materials containing Carbon) onto usual hi Z materials (like Ir, Au or Pt) have been proposed more than 10 years ago for enhancing the X-ray reflectivity at low energy (between 0.5 and 4 keV) in X-ray astronomical optics. The hack is to use the total reflection from the low density material (which do not suffer much the photoelectric absorption) at low energy, while the photons at high energy are reflected by the high density material. Now for several future projects like e.g. ATHENA and eXTP it is foreseen the use of low density overcoatings that will importantly increase the effective area at low energy. In this poster we will discuss about the use of materials different from the ones considered so far, in particular based on a thin layer of Chromium followed by another layer of a Carbon-like material, and of novel approaches for their application.}, subject = {R{\"o}ntgenteleskop}, language = {en} } @article{FranzYangMicheletal.2023, author = {Franz, Daniel and Yang, Yongting and Michel, Luis and Esen, Cemal and Hellmann, Ralf}, title = {Evaluation of an ultrashort pulsed laser robot system for flexible and large-area micromachining}, series = {Journal of Laser Applications}, volume = {35}, journal = {Journal of Laser Applications}, number = {4}, pages = {042057 -- 042065}, year = {2023}, abstract = {We report for the first time on the realization, characterization and application of an ultrashort pulsed laser robot system for flexible and large-area 2D and 3D laser micromachining with 6 articulated axes. To characterize the dynamic positioning of the laser beam during and after axes movement, CMOS image sensors were integrated into the beam path. A method introduced for the alignment of the optical axes allows a reduction of the deviations in laser beam positioning to less than 141.8 ± 92.9 μm within a 110° rotation range of axis 4. In addition, a high laser beam positioning repeatability of less than 102.2 μm is demonstrated over a total period of 14 h for a movement of axis 5 within a range of 0° to 90°. Initial laser cutting, laser structuring and laser marking applications on automotive dashboards and glass substrates are presented for flexible and large area 2D and 3D manufacturing. By applying a special laser cutting strategy for processing AF 32 eco thin glass, high cutting quality is achieved with a taper of up to 96.3\% without the generation of cracks, demonstrating the innovative potential of the high-precision laser robot system. Nonetheless, different identified inherent influences of each axis 1-5 during robot axis movement demand for an innovative beam stabilization concept to achieve high precision in laser beam positioning.}, subject = {Ultrakurzzeitlaser}, language = {en} } @article{KeferDaiYangetal.2020, author = {Kefer, Stefan and Dai, Jixiang and Yang, Minghong and Schmauss, Bernhard and Hellmann, Ralf}, title = {Hypersensitive H2 sensor based on polymer planar Bragg gratings coated with Pt-loaded WO3-SiO2}, series = {Optics Letters}, volume = {45}, journal = {Optics Letters}, number = {13}, doi = {https://doi.org/10.1364/OL.395341}, pages = {3601 -- 3604}, year = {2020}, abstract = {This letter demonstrates a novel hydrogen sensor based on a polymer planar Bragg grating coated with Pt-loaded WO3-SiO2. The reflected Bragg signal shows a distinct peak splitting correlated to substrate anisotropies originating from the injection molding process. Especially at low H2 concentrations, both sensing peaks exhibit an outstanding response to the heat generated by the exothermic reaction between hydrogen molecules and coating. Thereby, a hydrogen volume ratio of 50 ppm leads to a Bragg wavelength shift of -37 pm, which yields an outstandingly low detection limit of only 5 ppm H2 in air. Thus, functionalized polymer planar Bragg gratings are eminently suitable for H2 leak detection applications.}, subject = {Gassensor}, language = {en} } @misc{KeferDaiYangetal.2020, author = {Kefer, Stefan and Dai, Jixiang and Yang, Minghong and Schmauss, Bernhard and Hellmann, Ralf}, title = {Hypersensitive H2 sensor based on polymer planar Bragg gratings coated with Pt-loaded WO3-SiO2: erratum}, volume = {45}, number = {16}, doi = {https://doi.org/10.1364/OL.401819}, pages = {4498 -- 4498}, year = {2020}, abstract = {We present an erratum to our Letter [Opt. Lett. 45, 3601 (2020)]. Labeling errors in two figures and an incorrect sentence are revised. The corrections have no influence on the conclusions of the original Letter.}, subject = {Gassensor}, language = {en} }