Study of novel electron injection mechanisms for laser-wakefield accelerators

Thesis

Laser-driven plasma wakefields are structures that can sustain large electric fields and offer a promising route to reducing the size and cost of electron (or positron) accelerators with applications in areas such as fundamental research, (biomedical) imaging or radiotherapy. In this thesis, I discuss novel mechanisms through which electrons are injected into the accelerating structure and methods used to achieve better control over experimental conditions. Experimental and numerical results are presented for injection of electrons into a wakefield driven by a short relativistic laser pulse propagating through a plasma of overcritical nanometre-sized clusters. The wakefield structure is found to be modified by the clusters and the creation of high-charge large energy spread electron beams is discussed. Furthermore, experimental and numerical results are presented for externally induced ionisation injection using two pulses of equal wavelength decoupling the processes of driving the accelerating structure from the injection into the structure finding quasi-monoenergetic electron beams. Finally, a reinforcement learning based algorithm for laser beam alignment is introduced and training results of alignment performance for an interferometer set-up as well as an off-axis parabolic mirror are presented.

Authors: von der Leyen, M

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Subjects: Plasma accelerators