Neumann, Nico Wilfrid (2018)
Fabrication of micro-structured surfaces with increased light absorption and their influence on intense laser-plasma experiments.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
The thesis reports on the influence of customisable and highly light absorbing surfaces on laser-plasma experiments. For the first time, a thin microstructured silicon substrate is interacting with a short laser pulse with peak intensity exceeding 1020 W=cm2. In this process, electrons are accelerated and pushed into the target to relativistic energies. Furthermore, ions are accelerated perpendicular to the target surfaces and electromagnetic radiation is generated. In the framework of this work, a fabrication setup is developed that produces customisable structured silicon surfaces using a laser-assisted ablation and etching process with light pulses of femtosecond pulse length and the effect of laser-induced periodic surface structures (LIPSS). The evolving structure consists of conical silicon spikes with a significant increase in light absorption over a broad spectral range in the visible and infrared region. The experimental setup is demonstrated together with a characterisation of the resulting surface structures. Thereby, a precise prediction of needle height and separation is possible. Following, these structured silicon targets are compared to flat foils and different periodic geometric structures, typically used in laser-plasma experiments, in an experimental campaign using the petawatt class Vulcan laser system of the Central Laser Facility, Oxfordshire, UK. Spectral and spatial investigation of reflected laser light, X-ray generation, electron and ion acceleration in the experiment demonstrate an enhanced performance of the robust microstructured silicon needle structure facing the incident laser pulse. A significant increase in high energetic electrons, ions and brilliant X-ray radiation is observed in comparison to flat foils and targets with geometric structures. Reflection losses from the interaction area are decreased substantially. With the results of the experimental campaign a combination of the microstructured silicon surfaces with different materials is motivated. E.g. proton-rich materials can generate a reliable and auspicious source of laser-accelerated protons. Joining the structured target with a confined piece of material, pointlike sources of brilliant X-ray radiation of selectable photon energy become available. Employing the fabrication setup developed within the framework of this thesis a valuable addition to the scope of the Detektor & Targetlabor is given. The further development of the setup towards high-repetition rate laser facilities, production of customisable and more complex targets and evaluation of applications for highly light absorbing surfaces is promising.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2018 | ||||
Autor(en): | Neumann, Nico Wilfrid | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Fabrication of micro-structured surfaces with increased light absorption and their influence on intense laser-plasma experiments | ||||
Sprache: | Englisch | ||||
Referenten: | Roth, Prof. Dr. Markus ; Walther, Prof. Dr. Thomas | ||||
Publikationsjahr: | 2018 | ||||
Ort: | Darmstadt | ||||
Datum der mündlichen Prüfung: | 6 Juni 2018 | ||||
URL / URN: | http://tuprints.ulb.tu-darmstadt.de/7480 | ||||
Kurzbeschreibung (Abstract): | The thesis reports on the influence of customisable and highly light absorbing surfaces on laser-plasma experiments. For the first time, a thin microstructured silicon substrate is interacting with a short laser pulse with peak intensity exceeding 1020 W=cm2. In this process, electrons are accelerated and pushed into the target to relativistic energies. Furthermore, ions are accelerated perpendicular to the target surfaces and electromagnetic radiation is generated. In the framework of this work, a fabrication setup is developed that produces customisable structured silicon surfaces using a laser-assisted ablation and etching process with light pulses of femtosecond pulse length and the effect of laser-induced periodic surface structures (LIPSS). The evolving structure consists of conical silicon spikes with a significant increase in light absorption over a broad spectral range in the visible and infrared region. The experimental setup is demonstrated together with a characterisation of the resulting surface structures. Thereby, a precise prediction of needle height and separation is possible. Following, these structured silicon targets are compared to flat foils and different periodic geometric structures, typically used in laser-plasma experiments, in an experimental campaign using the petawatt class Vulcan laser system of the Central Laser Facility, Oxfordshire, UK. Spectral and spatial investigation of reflected laser light, X-ray generation, electron and ion acceleration in the experiment demonstrate an enhanced performance of the robust microstructured silicon needle structure facing the incident laser pulse. A significant increase in high energetic electrons, ions and brilliant X-ray radiation is observed in comparison to flat foils and targets with geometric structures. Reflection losses from the interaction area are decreased substantially. With the results of the experimental campaign a combination of the microstructured silicon surfaces with different materials is motivated. E.g. proton-rich materials can generate a reliable and auspicious source of laser-accelerated protons. Joining the structured target with a confined piece of material, pointlike sources of brilliant X-ray radiation of selectable photon energy become available. Employing the fabrication setup developed within the framework of this thesis a valuable addition to the scope of the Detektor & Targetlabor is given. The further development of the setup towards high-repetition rate laser facilities, production of customisable and more complex targets and evaluation of applications for highly light absorbing surfaces is promising. |
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Alternatives oder übersetztes Abstract: |
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URN: | urn:nbn:de:tuda-tuprints-74808 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 500 Naturwissenschaften 500 Naturwissenschaften und Mathematik > 530 Physik |
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Fachbereich(e)/-gebiet(e): | 05 Fachbereich Physik 05 Fachbereich Physik > Institut für Kernphysik 05 Fachbereich Physik > Institut für Kernphysik > Experimentelle Kernphysik 05 Fachbereich Physik > Institut für Kernphysik > Experimentelle Kernphysik > Laser- und Plasmaphysik |
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Hinterlegungsdatum: | 01 Jul 2018 19:55 | ||||
Letzte Änderung: | 01 Jul 2018 19:55 | ||||
PPN: | |||||
Referenten: | Roth, Prof. Dr. Markus ; Walther, Prof. Dr. Thomas | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 6 Juni 2018 | ||||
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