Injection and Plasma Waveguides for Multi-Stage Laser Plasma Acceleration

Laser plasma accelerators (LPAs) have shown promise as the next generation of compact particle accelerators. When a high intensity laser pulse propagates through a plasma, the laser can drive a large-amplitude wave which supports accelerating and focusing electric fields. Acceleration gradients three orders of magnitude greater than those found in conventional accelerators have been demonstrated. However, before an LPA-based high energy collider can be built, several advancements are still necessary, including further increases in beam energy and improvements in beam quality.While electron beams have been accelerated to 8 GeV in a 20 cm LPA, the energy gain in a single LPA stage is limited by the laser energy available. To reach the energies needed for high energy physics, coupling of many LPAs is required. In addition, the beams must be injected and accelerated with high beam quality to reach the luminosities needed at the collision point to produce enough events to search for new physics. While enormous progress has been seen in the acceleration of electrons, positron acceleration is more challenging because most of the existing LPA structures are less suitable for positively charged particles.In this thesis, we demonstrate staging of two laser plasma accelerators, injecting electrons in one stage and post-accelerating them in a second. We discuss the development of a high-quality injector stage and demonstrate techniques for controlling the injected electron beam parameters by modifying the plasma density profile. Finally, we detail a novel LPA structure which has demonstrated low-power laser guiding and has the potential to accelerate both electrons and positrons with high quality