Laser-plasma interactions used for the acceleration of electrons.

Abstract

This thesis deals with the interaction of short-pulse lasers with plasmas to accelerate electrons to high energies. Three different studies are included: two involve the driving of plasma waves and one the optical injection of electrons as a source of particles. First, a method for the control of stimulated Raman scattering in short-pulse laser-plasma interactions is proposed. The method relies on a linearly chirped non-bandwidth-limited pulse to affect control. Theoretical calculations show that a 20% chirp is needed to eliminate forward Raman scattering, which is confirmed in two-dimensional particle-in-cell simulations. Second, a method for generating large-amplitude plasma waves using multiple tailored pulses is studied. Analysis for sine-shaped pulses has shown that the optimum pulse length decreases and pulse spacing increases with plasma-wave amplitude. This effect was verified with particle-in-cell simulations. These simulations included damping due to particles trapped from the background, an effect not present in any previous analysis. Third, a novel laser-plasma-based source of relativistic electrons is proposed and studied in detail. Two laser pulses are used, one to excite the wave and the second to alter locally the trajectories of some electrons to induce trapping in the wave. One and two-dimensional particle-in-cell simulations demonstrated that bunches with 3.0 x 10<super>7</super> electrons could be produced. At 20 MeV these bunches had a length of 3 m m (9 fs), an energy spread of about 20%, and a normalized transverse emittance of 1 - 2 p mm &middot; mrad. All analyses are done using both theoretical and numerical techniques. Specifically, particle-in-cell simulations are performed for all studies. The larger two dimensional simulations are written to run on massively parallel computers.