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Title: Optimisation and applications of Raman plasma amplifiers
Author: Sadler, James
ISNI:       0000 0004 7232 7205
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2017
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Laser pulses have the shortest duration, smallest spatial extent, highest power, longest range and highest electric field of any known physical probe. In just 5 decades, the laser has led to the detection of gravitational waves, quantum optics and computers, worldwide fibre-optic communications, innumerable manufacturing applications and a prime contender for replicating the sun's nuclear fusion on earth. Modern high power lasers achieve intensities exceeding 1021 W/cm-2. Laser powers have increased without bound due to the method of chirped pulse amplification. However, continuing this trend may require new amplifier materials with higher damage thresholds. This work assesses the feasibility of laser amplification in a plasma. Energy is transferred from a long, low power pulse to a short, high power pulse. This is due to the coupling of the light with plasma electron waves, the so called Raman instability. The resulting pulses could ignite a nuclear fusion capsule under the fast ignition scheme, or generate electron positron plasmas. The energy efficiency and coherence of the amplifier are greatly influenced by the plasma conditions, investigated here using large scale computer simulations. The existing analytical solution is then generalised to three dimensions. The simulations show effective amplification, even in non-uniform plasmas. A method for seeding the amplifier was investigated experimentally at the Central Laser Facility. A second experiment at the Laboratory for Laser Energetics in New York, U.S.A., found features of the Raman light that show promise for testing the full scheme in 2019.
Supervisor: Arber, Tony ; Norreys, Peter ; Gregori, Gianluca Sponsor: Engineering and Physical Sciences Research Council ; Euratom
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available