Extreme Electron Beams and Brilliant X-rays : Generation, Manipulation and Characterization of Relativistic Electron Beams for and from Plasma-Based Accelerators

Abstract: This thesis is based on work done by the author on the development of plasma-based electron accelerators driven by ultra-intense laser pulses and dense electron bunches. Plasma based accelerators have several benefits, such as accelerating fields around 1000 times stronger than in “conventional” radio-frequency accelerators, which can allow for shrinking the overall footprint of the accelerator. They can also allow for generating electron beams with unprecedented peak currents and ultra-low emittances, meaning that a large number of electrons can be packed into a very short time duration and that the quality of the bunches is high. They can also be used to generate X-ray pulses with durations only otherwise achievable at a few large accelerator facilities, using a laboratory setup the size of a large living room. These characteristics make plasma-based accelerators interesting as a technology for future particle colliders and free-electron lasers, as well as, for example, smaller and more available X-ray sources with particular source characteristics such as ultra-short pulse durations.This thesis describes both numerical and experimental studies on plasma-based accelerators. The experimental work has mainly been on generating electron bunches and X-ray pulses using a laser-wakefield accelerator, as well as applications of the generated X-rays. The results from this branch of the research include the identification and demonstration of a new regime for laser-driven X-ray generation, which produces pulses with significantly reduced divergence compared to the standard method, simplifying the subsequent use of such pulses in applications.The numerical work has been focused towards conventional radio-frequency accelerators, concerning the shaping of electron bunches from such an accelerator for use in electron beam-driven plasma-wakefield acceleration. Themain point in this research has been removing or circumventing detrimental effects that occur during acceleration and transport, to create bunches which can drive stable wakes. One of the results from this research is an optimization strategy for certain bunch compressors, leading to a decrease in chromatic and geometric aberrations in the bunch. The common thread through both experimental and numerical work is plasma-based acceleration of electrons, and as such there is a larger overlap between these two parts than might initially be seen.