| Summary: | <p>The goal of controlled fusion energy has been pursued by the international community for decades. The majority of research into inertial confinement fusion, one branch of fusion research as a whole, has been focused on central hot spot ignition. However, alternative approaches such as fast ignition present the opportunity to achieve higher gains with reduced symmetry requirements, making them ideal for fusion energy production.</p> <p>One important component of the original fast ignition scheme is the formation of a persistent low-density channel through an inhomogeneous plasma. This thesis revolves around channeling with laser pulses of highly relativistic intensities through plasmas relevant to fast ignition research, an intensity regime which has not received thorough attention in the existing literature. In this thesis, several particle-in-cell simulations are run to analyze various schemes in an effort to gain greater control over the channeling process.</p> <p>An expanded physical model of the hosing instability that includes relativistic laser intensities and near-critical densities is presented and derives the density dependence of the hosing equation. This is then tested through simulations, and an examination of its consequences on multiple-pulse channeling schemes is conducted. The results show that the hosing instability grows more rapidly in dense plasmas, reducing the benefits of the multiple-pulse scheme when using realistic pulses of relativistic intensity.</p> <p>Phenomena such as a ponderomotive self-correction mechanism, self-focusing-induced filamentation, and a modulated wavepacket known as the "pathfinder" pulse all become more relevant at higher pulse intensities. These have interesting consequences for future channeling schemes.</p> <p>Finally, an experiment performed at the OMEGA EP facility at the Laboratory for Laser Energetics in Rochester, NY, USA is presented and analyzed. This experiment explored the effects of pulse timing, intensity, and focal position on channel formation. The findings of this experiment have important consequences for experimental design and have already improved the results of integrated fast ignition experiments.</p>
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