Optimisation and control of ion acceleration in intense laser-foil interactions

This thesis reports on experimental and numerical investigations of ion acceleration driven by the interaction of short, ultra-intense (> 1020 Wcm-2), linearly polarised pulses of laser light with thin foil targets. Four investigations were performed to explore various aspects of the acceleration and the physics underpinning potential applications of these sources.;The first investigation explores a hybrid scheme of radiation pressure-sheath acceleration, enhanced by relativistic transparency at an optimum foil thickness. Efficient proton acceleration with energies exceeding 94 MeV is achieved. The range of parameters over which this hybrid scenario occurs is discussed, and implications for ion acceleration driven by next-generation, multi-PW laser facilities are explored.;The second investigation concerns the diagnosis of the highly transient electric field responsible for ion acceleration in the target normal sheath acceleration (TNSA) regime. High resolution, temporally-resolved measurements of the field evolution are obtained using proton deectometry.;In the third investigation, a laser generated proton beam is used to heat and preexpand the rear-surface of a secondary foil. This target is then irradiated by a second laser pulse, with the resultant proton beam spatial-intensity distribution measured. For an increasingly expanded target the maximum proton energy, overall number of accelerated protons and the size of the proton beam consistently decreases. A simple analytical model describing the expansion behaviour is developed.;In the final investigation, initial steps towards proton focusing for the purposes of proton fast ignition (PFI) using novel conical targets are addressed. Clear focusing is observed for an open-tipped conical target. These beams are used to isochorically heat copper, with the X-ray emission imaged. Finally, in order to close in on a realistic PFI scenario, the effects of an external plasma surrounding the cone is explored.This thesis reports on experimental and numerical investigations of ion acceleration driven by the interaction of short, ultra-intense (> 1020 Wcm-2), linearly polarised pulses of laser light with thin foil targets. Four investigations were performed to explore various aspects of the acceleration and the physics underpinning potential applications of these sources.;The first investigation explores a hybrid scheme of radiation pressure-sheath acceleration, enhanced by relativistic transparency at an optimum foil thickness. Efficient proton acceleration with energies exceeding 94 MeV is achieved. The range of parameters over which this hybrid scenario occurs is discussed, and implications for ion acceleration driven by next-generation, multi-PW laser facilities are explored.;The second investigation concerns the diagnosis of the highly transient electric field responsible for ion acceleration in the target normal sheath acceleration (TNSA) regime. High resolution, temporally-resolved measurements of the field evolution are obtained using proton deectometry.;In the third investigation, a laser generated proton beam is used to heat and preexpand the rear-surface of a secondary foil. This target is then irradiated by a second laser pulse, with the resultant proton beam spatial-intensity distribution measured. For an increasingly expanded target the maximum proton energy, overall number of accelerated protons and the size of the proton beam consistently decreases. A simple analytical model describing the expansion behaviour is developed.;In the final investigation, initial steps towards proton focusing for the purposes of proton fast ignition (PFI) using novel conical targets are addressed. Clear focusing is observed for an open-tipped conical target. These beams are used to isochorically heat copper, with the X-ray emission imaged. Finally, in order to close in on a realistic PFI scenario, the effects of an external plasma surrounding the cone is explored