Investigating electronic motions in matter at their natural time and length scale requires
radiation pulses simultaneously providing attoseconds temporal and Ångstrom spatial
resolution. This could reveal a previously unexplored realm of nature. While hard X-ray
Free-Electron Lasers (XFELs) based on radiofrequency technology can routinely produce
coherent radiation pulses with femtosecond durations and Ångstrom wavelengths, they
require optimized kilometre-scale machines with limited beam time. This thesis shows
that plasma-based accelerators can produce multi-GeV electron beams with superior
beam quality on the sub-meter scale, paving the way for ultra-compact hard XFELs
at meter-scale distances. Three innovations constitute the blueprint for the ultracompact, plasma-based attosecond-Ångstrom class free-electron laser with unprecedented
electron and photon beam quality. First, the experimental demonstration of the plasma
photocathode injection in Plasma Wakefield Acceleration (PWFA) at Stanford Linear
Accelerator (SLAC) Facility for Advanced Accelerator Experimental Tests (FACET)
shows the feasibility of the plasma photocathode concept. In-depth simulations revealed
the full reach of the plasma photocathode in PWFA. This study also highlighted that the
impact of injector laser jitter on electron beam stability in the various building blocks is
compatible with the requirements of XFELs, thanks to the fundamental physics of the
mechanisms. Second, the development of a novel energy chirp compensation method
allows for the minimization of the projected relative energy spread of ultra-high 5D
brightness electron beams in the same plasma stage without compromising the nm-rad
normalized emittances of the beams, enabling the preservation of emittances at the
nm-rad level during the extraction from the plasma-stage. Third, an ultra-compact,
plasma-based hard XFEL concept is developed and backed by a high-fidelity start-to-end
simulations framework. A PWFA stage equipped with plasma photocathode injectors
produces electron beams of unprecedented 6D brightness. The electron beam quality
is preserved along the acceleration, dechirping, and extraction from the plasma stage.
Then, an optimized beam transport line captures, isolates, and refocuses these ultrahigh 6D brightness electron beams into an undulator without quality loss. A 10 m long undulator section leverages these electron beams to power a hard XFEL near the cold beam limit. These electron beams straightforwardly generate nearly transform-limited photon pulses at attosecond duration down to sub-Ångstrom wavelength, with prospects towards higher photon energies and fully coherent radiation pulses. An experimental feasibility analysis concludes with prospects and opportunities for realizing the concept at linac-based PWFA facilities and/or at Laser Wakefield Acceleration (LWFA) facilities through the Hybrid LWFA→PWFA approach, which may enable truly ultra-compact plasma-based hard XFELs. The individual findings of this thesis may significantly advance their respective subjects, though a transformative impact emerges from the
combined ramifications of the findings. For example, the realization of the concept
with an all-optical Hybrid LWFA→PWFA system or in combination with a linacbased PWFA facility in collider geometry could enable collocated ultra-high brightness electron beams, TW- to PW-class laser pulses, hard XFEL photon pulses, or γ-ray pulses generated by these electron beams at the interaction point, all intrinsically synchronized. Such a configuration may allow the ubiquitous use of photon and electron beams in various permutations for completely novel photon science, nuclear and particle physics, fundamental science and quantum electrodynamics exploration.
| Date of Award | 11 Sept 2024 |
|---|
| Original language | English |
|---|
| Awarding Institution | - University Of Strathclyde
|
|---|
| Sponsors | EPSRC (Engineering and Physical Sciences Research Council) |
|---|
| Supervisor | Bernhard Hidding (Supervisor) & Brian McNeil (Supervisor) |
|---|