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Title: Investigation of Electron Laser Wakefield Acceleration in Novel Plasma Structures
Author: Kamperidis, Christos Antonios
ISNI:       0000 0001 3594 3752
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2008
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This thesis presents experimental and simulation results on electron acceleration from the interaction of ultra-intense, ultra-short lasers with underdense plasmas, based on two schemes of the Laser Wakefield Acceleration (LWFA) mechanism. Using the 100 TW laser, in LUll, France, with pulse durations of 500 fsec and intensities' greater than 5.1018 W/cm2 , electron energies of up to 200 MeV,)Here observed. The spectra of the electron beams exhibit a maxwellian distribution, which together-with the recording of the Raman satellites of the laser spectrum suggest that we operate in the Self Modulated-LWFA, making these beams the highest energy observed to date, in that scheme. Total charge estimates suggest that a 1% energy transfer to the electron beam is possible. Occasional non-maxwellian features in the electron spectra, backed up by simulations, suggest that mechanisms other than SM-LWFA are also present in the interaction. Most importantly, self-guiding channels of - cm scales are observed adding a new perspective in achieving a commercially viable LWF accelerator. In the classical short pulse regime of LWFA, the ASTRA (0.6 J, < 50 fsec) laser is used to compare electron acceleration, with and without an external waveguide. Maximum electron energy results in the self-guided regime are only 2x lower compared to the externally guided case. The stability and reproducibility of the beam however, is improved when the external waveguide is used. Electron beams with 200 MeV maximum energy and narrow energy spread are consistently observed. The appearance of these beams is strongly linked with ionisation effects, either from high ion states of waveguide wall material, or recombined gas. A particle tracking code shows that electrons released from ionisation processes within the laser pulse, and hence within the plasma wake, are trapped by the wake and accelerated, pro.ducing a bunch with low energy spread. These lay the basis for future experiments, envisaging improved stability, wall-plug energy transfer efficiency and high brilliance electron beams.
Supervisor: Not available Sponsor: Not available
Qualification Name: Imperial College, 2008 Qualification Level: Doctoral
EThOS ID:  DOI: Not available