Thesis
Investiating relativistic transparency : absorption and propagation of high-intensity laser pulses in plasma
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T17070
- Person Identifier (Local)
- 201992712
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This thesis reports on experimental and numerical investigations of the interaction of intense laser pulses (> 1018 Wcm−2) with ultra-thin (micro and nanometre scale) foils undergoing expansion and relativistic self-induced transparency. Laser energy absorption and propagation physics is explored to enhance our understanding of how intense laser light interacts with foils in the relativistic transparency regime. This interaction regime is important for the laser-driven generation of high-energy particles such as electrons and ions and for generating x-rays and γ-rays and gigagauss magnetic fields. Aspects of such interactions have immense significance in realising numerous envisioned potential applications that include their use as an driver for inertial fusion and in proton therapy for cancer treatment, while offering valuable insights into underlying fundamental physics. Control of the laser-plasma interaction physics is important for the development of these potential applications. The work reported in this thesis focuses on laser energy absorption and propagation in dense plasma. This involves an in-depth examination of the relativistic self-focusing phenomena and identifies the critical parameters that can be manipulated to enhance or control this. The work is organised into two primary investigations. The first study presents diagnostic methods used to characterise the degree of laser energy absorption in overdense and relativistically transparent plasmas. To begin, the scaling of absorption with peak laser intensity for targets that remain opaque during the interaction was investigated using diagnostic techniques developed specifically for these measurements. The results demonstrate a strong agreement with previously published data. Measurements were conducted to examine how absorption varies in targets undergoing Relativistic Self-Induced Transparency (RSIT) and the impact of this process on the laser pulse propagation. It is found that for targets exhibiting significant transmission of the laser light, the measurements are strongly dependent on the particular design of the diagnostic tools used. This effect can be corrected by modifying the design of the instrument. The result point to a significant degree of collimation of the transmitted laser light. The second focuses on numerical investigation of the underpinning physics, including relativistic self-focusing effects during the propagation of a intense laser pulses in relativistically transparent plasma. PIC simulations were performed with increasing complexity to investigate the underlying physics. It is found that the two most important factors that influence the absorption and propagation of the beam are the focal position of the pulse and the expansion of the plasma. The combination of these two parameters can influence the laser pulse propagation and produce a less divergent pulse far from the target. This study carries significant implications for fundamental comprehension, the advancement of applications, and for refining experimental procedures.
- Advisor / supervisor
- McKenna, Paul
- Resource Type
- DOI
Relazioni
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PDF of thesis T17070 | 2024-10-09 | Pubblico | Scaricare |