Intense laser-plasma interactions

Sammanfattning: In the interaction of ultra-intense laser fields with matter, the target is rapidly ionized and a plasma is formed. The ability of a plasma to sustain acceleration gradients, orders of magnitude larger than achievable with conventional accelerators, has led to a great interest in laser-driven plasma-based particle and radiation sources, with applications in materials science, biology and medicine. In this thesis, two separate, yet highly related, topics are pursued. The first half of the thesis concerns plasma-based techniques for ion acceleration, through the interaction of intense laser fields with solid density targets. In the most accessible acceleration scheme, the ion acceleration is mediated by a population of suprathermal, hot , electrons produced by the rapid heating of the target surface. We study the effect of adding microstructures to the target surface, show how this affects the distribution of hot electrons and discuss its implications for ion acceleration. We further study a novel acceleration scheme, aimed at achieving controllable ion acceleration using a frequency chirped standing wave. We analyse the robustness of this scheme, named chirped-standing-wave acceleration, under non-ideal conditions and discuss its prospects and limitations. The second half of the thesis concerns laser-matter interactions where the emission of high-energy photons necessitates a quantum mechanical description of radiation reaction and enables a prolific production of electron-positron pairs. In this regime, we study the interaction of an energetic electron beam with an optimally focused laser field, in the form of a dipole wave, and highlight its capabilities as a multi-GeV photon source. We further discuss the phenomena observed in this setup, in particular investigating the emergence of pair production cascades, and provide a review of previous results. Finally, we highlight a number of regimes within reach of upcoming laser facilities.