Terahertz-driven manipulation of electron bunches using dielectric-lined waveguides

Abstract

In this thesis the characterisation and implementation of dielectric-lined waveguides (DLW) for Terahertz (THz) driven acceleration and manipulation of electron bunches is presented. THz-driven particle accelerators are very promising for unprecedented control over the phase space of charged particle bunches compared with conventional radio frequency technologies. The modes in a DLW were exploited, allowing certain frequencies to propagate at phase velocities less than the speed of light, achieving extended collinear interaction with electron beams. Here, the first proof-of-principal THz-driven acceleration of relativistic electrons is demonstrated, using the CLARA beamline. Narrowband THz pulses were tuned to the phase velocity-matched operating frequency of the DLW, inducing multicycle energy modulation to 35 MeV, 60 pC, 6 ps-long chirped bunches and energy gain of up to 10 keV to 2 ps-long bunches. The linear and cubic coefficients of 47.3 keV/ps and 0.4 keV/ps^3 were determined for the chirped bunch. Furthermore, THz-driven ultrafast deflection of 100 keV electrons was demonstrated. A DLW was driven by single-cycle THz pulses, achieving a time-dependent deflection. A streaking speed of 28 mrad/ps was measured. The experimental results were supported with simulations, enabling the 3.6 ps bunch duration to be determined. The phase-matching capability of the DLW structures was experimentally investigated through time-frequency analysis, measured in a time-domain THz spectroscopy experiment. From the analysis, the propagation constant of the LSM modes were determined, and supported by a model. These proof-of-principal results establish a route to all-optical control, characterisation and acceleration of ultrafast electron bunches, directly applicable to different energy regimes, thus making a key milestone for future THz-driven electron manipulation and acceleration.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Darren Graham (Supervisor) & Robert Appleby (Supervisor)