Dokument: Optical Emission Spectroscopy of ultra-short Laser-induced Plasmas
| Titel: | Optical Emission Spectroscopy of ultra-short Laser-induced Plasmas | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=61964 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20230213-110712-9 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Mittelmann, Steffen [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Pretzler, Georg [Gutachter] Dr. Lehmann, Götz [Gutachter] | |||||||
| Stichwörter: | LIBS, Optical Emission Spectroscopy, fs-Laser, Laser-induced Plasma | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 530 Physik | |||||||
| Beschreibung: | Optical Emission Spectroscopy (OES) is widely known and applied to classical plasmas found
in industry and laboratories for various applications. These plasmas exhibit temperatures of a few eV, which is “cold” compared to early stage laser-induced plasmas. Still, those are of high interest in material diagnostic application, which is called Laser-Induced Breakdown Spectroscopy (LIBS). LIBS is a powerful, versatile, low invasive tool to quickly analyze the material composition of diverse kinds of samples. For example, it can be used to detect minor elements and isotopes in alloys or other material mixtures, independent of their state of matter and physical form. Moreover, it brings material information without the need for any sample preparation, which makes it suitable for on-line and hands-off experiments in inaccessible areas, for example in space or in nuclear safety zones. For these reasons, LIBS and a few other laser-induced diagnostics are proposed to be used to detect depositions and fuel retention in plasma-facing components of the inner walls of magnetic confinement fusion reactor vessels as in-situ techniques. Their applicability can be tested in experimental fusion facilities like, without limitation, EAST in China, ITER in France, or Wendelstein 7-X in Germany. This thesis intends to describe the ultra-short laser-induced plasma expansion dynamic in different environments with the focus on femtosecond lasers in high vacuum conditions. The research question treated is whether ultra-short femtosecond LIBS can be a reasonable alternative in the described context inside the fusion vessel. Here, a collection of different experiments is presented using several laser systems. In the beginning, the laser ablation characteristic of lasers with strongly deviating pulse duration in vacuum will be compared in an extensive study on the test material tantalum. This comparison will be followed by comprehensive examinations of the plasma induced by sub-10-fs pulses in vacuum using an imaging system and time resolved OES. Regarding the initial objective, this part will demonstrate some challenges in the use of these laser pulses in LIBS analyses and propose a tool to improve their applicability. This tool is a pre-pulse module that brings the opportunity to enhance the emitted spectral intensity of the expanding plasma and decreases the detection limit of certain species in the plasma. The fuels in the fusion reactor are basically the heavier isotopes of hydrogen: deuterium and tritium. As the objective of this thesis includes the quantification of fuel retention in the plasma-facing components, two closing experiments will be presented demonstrating the feasibility of hydrogen isotope detection in high-Z metals tungsten and tantalum with a nanosecond- and a femtosecond laser. Here, a calibration free LIBS approach is applied to determine the total amount of deuterium retention in these metal tiles. The results are shown to be in good agreement with Thermal Desorption Spectroscopy (TDS) data, which makes this a meaningful proof-of-principle experiment for further applications in this context. To gain a deeper understanding of the fundamentals of laser-plasma coupling, ablation processes, and plasma expansion, this thesis aspires to give a review on the physical concepts behind the effects observed in experiments integrated in published literature in the field. | |||||||
| Lizenz: |  Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Physik » Laser- und Plasmaphysik | |||||||
| Dokument erstellt am: | 13.02.2023 | |||||||
| Dateien geändert am: | 13.02.2023 | |||||||
| Promotionsantrag am: | 08.11.2022 | |||||||
| Datum der Promotion: | 27.01.2023 |
