Thesis
Controlled injection and hybrid staging in plasma wakefield accelerators
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2026
- Thesis identifier
- T17592
- Person Identifier (Local)
- 201671959
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Plasma wakefields, driven by either a short, highly intense laser pulse or a short and dense, highly relativistic charged-particle beam, can provide electric field strengths orders of magnitude beyond what is in reach with conventional accelerator technology. They could therefore drastically reduce the size and costs of particle accelerators and, accordingly, their applications. Prospects for miniaturised light sources based on electron beams delivered by compact plasma wakefield accelerators are particularly attractive, however, require substantial improvements in beam quality. An important compound quality parameter is the beam brightness. The beam brightness attainable in plasma wakefield accelerators is largely determined by the mechanism through which the electrons are injected into the accelerating wakefield. A particularly promising method is the plasma photocathode, which utilises a comparatively low-intensity laser pulse to release electrons at precisely controlled locations directly inside the wake structure. Plasma photocathodes offer a pathway for generating electron beams of highest brightness, and unfold their full potential in particle beam-driven plasma wakefield accelerators (PWFAs). However, establishing wakefield conditions suitable for plasma photocathode injection requires particularly strong drivers with high peak-currents. Such drivers are challenging to produce, and could thus far only be delivered by a kilometre-scale conventional accelerator. Meanwhile, laser-driven wakefield accelerators (LWFAs) are realised in many comparatively small-scale high-power laser facilities all over the world. Compact LWFAs nowadays excel in generating short, high peak-current electron beams that may provide superb drivers for a subsequent PWFA stage. Such a hybrid LWFA-PWFA staging concept (LPWFA) thus offers to combine and exploit the individual advantages of both laser- and particle beam-driven methods. This thesis explores these two approaches – plasma photocathode injection and hybrid staging – conceptually and experimentally. The first part of this thesis introduces fundamental concepts of plasma wakefield accelerators, briefly discusses differences in LWFA and PWFA approaches, and provides an overview of common injection methods. The second part of this thesis focuses on plasma photocathode injection and presents a first proof-of-principle experiment conducted at the Facility for Advanced Accelerator Tests at the SLAC National Laboratory (USA), utilising its ∼2 km long conventional accelerator to provide electron drive beams. While this experiment was not yet designed for delivering highest output beam quality, it demonstrates the feasibility of plasma photocathode injection, showcases the production of electron beams with substantially better emittance compared to the original driver, and provides valuable insights for further implementations. The third part of this thesis discusses prospects of the hybrid staging concept and presents a first experimental realisation of a hybrid plasma wakefield accelerator prototype. This experiment was conducted at the DRACO laser facility at the Helmholtz-Zentrum Dresden–Rossendorf (Germany), utilising a ∼3 mm long LWFA stage powered by a ∼150 TW laser pulse to generate electron drivers for the subsequent PWFA stage. The main result of this experiment is the acceleration of electrons up to ∼ 130 MeV in a discrete, ∼1.5 mm long PWFA section. This achievement constitutes the first demonstration of electron acceleration in a separate PWFA stage powered by LWFA-generated electron drivers. The results presented in this thesis demonstrate the feasibility of plasma photocathodes and establish hybrid LPWFA systems as novel accelerator platform. In the future, a variety of PWFA concepts can therefore be explored and further developed at widely accessible, compact LWFA systems, including advanced injection schemes such as the plasma photocathode. Ultimately, the combination of hybrid staging and plasma photocathodes may lead to a new class of truly compact accelerator systems delivering electron beams of unprecedented brightness.
- Advisor / supervisor
- Hidding, Bernhard
- Resource Type
- DOI
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PDF of thesis T17592 | 2026-02-24 | Public | Download |