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High energy density physics in cluster media

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Title: High energy density physics in cluster media
Authors: Olsson Robbie, Stefan Ian
Item Type: Thesis or dissertation
Abstract: Gases comprised of atomic clusters have in the past been shown to exhibit extremely strong absorption of high-intensity laser pulses. By using this target medium, it is possible to use laser systems with only modest energies to create High Energy Density Plasmas. Not only are the plasmas created in this way of interest in themselves, but when properly designed, these experiments can be used as a platform for Laboratory Astrophysics studies of radiative blast waves. This thesis describes experiments which investigate the evolution of radiative blast waves, the interaction of relativistic laser pulses with large atomic clusters and the nature of the post laser-cluster interaction upstream medium into which the shock propagates. Experiments were carried out to diagnose the properties of the upstream medium into which radiative shocks launched by the laser-cluster interaction propagate. This experiment was conducted using the Blackett Laboratory Laser Consortium Nd:Glass laser system with a novel perpendicular heating beam geometry. By introducing a time delay between the perpendicular beams, it was possible to track the propagation of a ballistic cluster disassemble wave. This wave was shown to be the product of ~200 keV ions ejected by the initial laser cluster-interaction. Also discussed in this thesis are the results of the first laser-cluster experiment to be conducted on the Central Laser Facility's Astra-Gemini system. Here the interaction of large atomic clusters with relativistic laser pulses is investigated. X-Ray pinhole camera images have been captured of the early time plasma created by the laser-clusters interaction. For the first time the absorption properties of large atomic clusters irradiated by a femtosecond high energy, ~14 J, laser pulse have been studied. Furthermore, the temporal evolution of radiative blast waves launched from the laser-cluster interaction is described. In the past the Vulcan laser system at RAL was used to launch blast waves which displayed velocity domain oscillations driven by the radiation emitted by the blast wave. This instability has again been observed in the work reported here and the threshold for onset has been investigated.
Content Version: Open Access
Issue Date: Jul-2013
Date Awarded: Dec-2013
URI: http://hdl.handle.net/10044/1/18394
DOI: https://doi.org/10.25560/18394
Supervisor: Smith, Roland
Department: Physics
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Physics PhD theses

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