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Record Id 63333562
Title Femtosecond Synchronisation for Externally-Injected Laser Wakefield Acceleration at CLARA
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Abstract Conventional particle accelerators have widespread use in science and wider society, but are limited by their maximum accelerating gradient, size, and cost. Laser wakefield acceleration (LWFA) can achieve accelerating gradients an order of magnitude greater, allowing for more compact and thus cheaper accelerators to be built. One LWFA scheme of interest is externally-injected LWFA, where an electron bunch from a conventional accelerator is accelerated further by LWFA, due to its potential for high accelerating gradients and high accelerated electron bunch quality. However, performing externally-injected LWFA experiments at current accelerator facilities requires femtosecond-level synchronisation between the optical master oscillator (OMO) that provides facility-wide timing pulses and the external laser used for the experiment. RF-based synchronisation methods cannot achieve such performance; thus, an improved optical synchronisation method is required. In this thesis, a design for a two-colour fibre-coupled synchronisation system is presented, with the aim of achieving femtosecond optical synchronisation between two lasers of different wavelength. The proposed design can achieve 5 times greater sensitivity to relative timing changes between laser pulses compared to existing free-space coupled synchronisation systems that are currently used. With optimisations to this design, sensitivities more than 10 times greater than current optical synchronisation systems can be achieved. This could allow for few-femtosecond temporal resolution in accelerator-laser experiments performed at Daresbury Laboratory. In particular, Chapter 4 of this thesis investigates externally-injected LWFA driven by a high-power Yb:Fibre laser, with the injected electron bunches provided by the Compact Linear Accelerator for Research and Applications (CLARA) at Daresbury. Simulations of externally-injected LWFA are performed to demonstrate the importance of femtosecond synchronisation between the laser and the external electron bunch and thus the need for an improved synchronisation system. Using feasible Yb:Fibre laser parameters, accelerating gradients larger than 1 GV/m are achieved over 0.5 m of plasma, an order of magnitude greater than conventional RF methods.
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Language English (EN)
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Thesis PhD, University of Liverpool, 2024. 201517411_Jul2024.pdf 2024