Modelling of hybrid plasma accelerators

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Awarding institution
  • University of Strathclyde
Date of award
  • 2022
Thesis identifier
  • T16211
Person Identifier (Local)
  • 201650589
Qualification Level
Qualification Name
Department, School or Faculty
  • A promising scheme for plasma wakefield acceleration is the hybrid plasma acceleration mechanism, which is experimentally connected to worldwide programs at various accelerator facilities. This scheme may lead to extremely high-quality electron bunches, that can be used to drive ultrabright light sources such as free electron lasers. The big challenge for plasma acceleration is to produce electron bunches with high quality in terms of low emittance, energy spread, and high brightness. To overcome this challenge, the Trojan Horse "plasma photocathode" scheme is used to produce designer electron beams. This thesis explores the Trojan Horse mechanism in a systematic simulation based parametric study. Different interaction regimes are explored by variation of the injector laser pulse by normalised vector potential a0, spot size w0 and relative spatiotemporal synchronisation and alignment in the plasma wave at various densities. These parameters define the plasma photocathode process. The general motivation of this work is to investigate the generation of high quality electron beams for light source applications. Several factors and mechanisms impact the witness bunch, affect its beam emittance, and drive its growth. The main driver for emittance growth, particularly at increased witness beam charge levels, is space charge and intra-beam Coulomb repulsion. Although the laser-released electrons from the plasma photocathode are rapidly accelerated and focused by the plasma wakefields, increasing the charge, e.g., by means of increasing the background plasma density from which the plasma photocathode electrons are liberated, produced very strong electric fields inside the bunch and thus triggered and driven rapid emittance growth. The effect of evolving space charge in the formative phase of the witness beam production and acceleration is investigated using tailored particle-in-cell simulations, for example, by scanning the evolution of transverse phase space across different plasma densities, and the illumination of the process by analysis is not available to the experiment but only to high-resolution and high-fidelity simulations. These computational studies provide insight into the sensitivities and robustness of the scheme, which is important for upcoming experiments, e.g., at SLAC, FACET-II, and may allow pushing the emittance and brightness barrier of electron beams produced by the Trojan Horse process. This could dramatically impact applications such as ultrabright, hard x-ray free-electron lasers, particle and strongfield physics.
Advisor / supervisor
  • Hidding, Bernhard
  • McNeil, Brian, 1954-
Resource Type