Licentiatseminarium: Frida Brogren

Modeling concepts for Laser-Wakefield Acceleration

Abstract

Laser wakefield accelerators have strong potential as future compact sources of high-charge relativistic electrons. However, their practical application is currently limited by significant shot-to-shot variations, large energy spreads, and high emittance. These fluctuations primarily arise from the high sensitivity of the acceleration process on the properties of the driving laser. To increase the knowledge of this interaction, I consider two complementary methods to model laser wakefield acceleration: data-driven modeling and Particle-In-Cell (PIC) simulations. 

The data-driven method employs a neural network to model relationships between laser properties, electron properties and secondary X-ray generation in a laser wakefield accelerator. In experimental setups, measurement errors are prevalent and in particular the developed model mitigates the influence of these by employing a novel optimization criteria. Analysis of the model reveals strong consistency with physics-based simulations and theoretical expectations and, additionally, reveals unknown correlations between laser driver and system output. Thus, the model shows strong potential as a foundation for the stabilization and analysis of laser wakefield accelerators in experimental settings.

On the other hand, for the design and study of laser-plasma interactions, physics-based models, such as particle-in-cell (PIC) simulations are essential. These simulations come at a significant computational cost, which can be levitated by performing them in a Lorentz-boosted frame. However, this approach is often limited by the Numerical Cherenkov Instability (NCI). In this thesis, a lightweight PIC framework, pi-PIC, is introduced to facilitate easy testing and integration of new PIC algorithmic developments. Using this framework, the influence of energy and momentum conservation on NCI growth is examined.

Opponent: Åsa Larson (SU)
Handledare: Arkady Gonoskov
Extra handledare: Mattias Marklund
Examinator: Dag Hanstorp