An investigation was carried out looking into the process of laser wakefield acceleration of electrons, for the possible application to the generation of multi-MeV γ-rays via nonlinear Thomson scattering. The effects of introducing a gas density gradient just after the accelerating gas cell was tested with the intention of observing an increase in the energy of electrons and an improvement on several other parameters of the beam after acceleration (divergence, relative peak width, and beam pointing). It was found that a density gradient was able to accelerate the electrons to higher energies owing to the longer acceleration lengths, with the final energy being up to 85% larger than the initial energy when shots were averaged out every 5 points. The pointing of the beam relative to the laser axis was also found to stabilise around the zero point after 70 shots, whereas the divergence and relative width of the monoenergetic peaks (∆E/E)remained relatively constant, with values of ∼ 1mrad and ∼ 15% the maximum energy respectively. These findings are in line with the hypothesis that stated divergence should not be affected, but energy will be. Further improvements on these results could be obtained with the implementation of hydrodynamic and particle-in-cell simulations of the interactions and experimentation with gas cells of varying density gradients, in order to develop a fully quantitative theory of the laser-gas interaction.
|Date of Award||Mar 2015|
- Queen's University Belfast
|Supervisor||Gianluca Sarri (Supervisor)|