Speaker
Description
Free Electron Lasers (FELs) are novel light sources capable of generating ultrashort, femtosecond-duration pulses via electron oscillations in electromagnetic fields. A defining advantage of FELs is that the radiation wavelength is inversely proportional to the square of the electron beam energy, allowing continuous and tunable access across the electromagnetic spectrum. At electron energies of 10 GeV, FELs can produce hard X-rays—wavelengths otherwise unattainable with conventional lasers. These X-rays, characterised by their high penetration and ultrashort wavelengths, are uniquely suited for applications such as imaging dense materials (e.g. bone tomography) and time-resolved probing of dynamic processes like shock wave propagation in metals.
Recent progress in compact free-electron laser (FEL) concepts, driven by laser and beam-plasma wakefield acceleration, has demonstrated exponential gain using electron beams with energies of a few hundred MeV. While wakefield acceleration offers a pathway to significantly more compact FEL systems, accurately modelling their performance remains computationally demanding. This challenge arises primarily from the vast scale disparity between the nanometre-scale radiation wavelength and the macroscopic length of the beamline. Moreover, at these relatively low electron energies, space-charge effects and beam emittance critically influence both the beam dynamics and overall FEL performance.
In this work, we employ boosted-frame particle-in-cell (PIC) simulations to perform efficient, start-to-end modelling of the SPARC FEL. The use of a Lorentz-boosted frame leverages the Doppler redshift and length contraction, yielding a substantial computational speed-up that scales as γ². Simulations that would require over a month in the laboratory frame can be completed within hours in the boosted frame. Importantly, PIC simulations inherently capture self-consistent space-charge and emittance effects, making them ideally suited for exploring the beam dynamics and lasing behaviour in compact FEL systems.
