Longitudinal Beam Characterisation on VELA using a Transverse Deflecting Cavity



Mckenzie, J
(2019) Longitudinal Beam Characterisation on VELA using a Transverse Deflecting Cavity. PhD thesis, University of Liverpool.

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Abstract

This thesis presents the design and commissioning of a system to characterise the longitudinal beam properties of VELA (Versatile Electron Linear Accelerator) based around a transverse deflecting cavity, and the first measurements made using it. VELA at Daresbury Laboratory consists of an S-band RF photoinjector, which accelerates electrons to approximately 5 MeV/c. VELA was intended as the injector for the CLARA Free Electron Laser test facility. The gun is operated in the ``blow-out'' regime, driven by a laser of pulse length 76 fs rms, with the electron beam distribution formed by the space-charge of the bunch. The transverse deflecting cavity is a 9-cell standing wave S-band cavity and the design was intended to provide 10 fs temporal resolution for the 250 MeV beam from CLARA. This thesis shows how the design of the cavity evolved via beam dynamics simulations to reduce unwanted transverse beam offset and momentum change through the cavity. Bunch length measurements are presented using the deflecting cavity to characterise the ``blow-out'' regime of the gun at bunch charges from 40 fC to 215 pC, and as a function of gun phase and beam momentum. Investigations into measurements of the longitudinal phase space distribution of the beam are also presented.

Item Type: Thesis (PhD)
Divisions: Fac of Science & Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 26 Mar 2019 11:48
Last Modified: 03 Mar 2021 10:12
DOI: 10.17638/03031981
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3031981