Attosecond-Angstrom free-electron-laser towards the cold beam limit

TL;DR

This paper demonstrates that plasma wakefield accelerators can produce ultrabright, sub-femtosecond electron beams capable of driving attosecond-Angstrom free-electron lasers, enabling coherent X-ray pulses at unprecedented scales.

Contribution

It introduces a method to generate ultrabright electron beams from plasma photocathodes and use them in FELs to reach the cold beam limit at much shorter undulator lengths than traditional setups.

Findings

Electron beams from plasma photocathodes are many orders of magnitude brighter than current sources.

Ultrabright electron beams can generate coherent X-ray pulses of attosecond-Angstrom scale.

FEL saturation can be achieved after only 10 meters of undulator using plasma-accelerated beams.

Abstract

Electron beam quality is paramount for X-ray pulse production in free-electron-lasers (FELs). State-of-the-art linear accelerators (linacs) can deliver multi-GeV electron beams with sufficient quality for hard X-ray-FELs, albeit requiring km-scale setups, whereas plasma-based accelerators can produce multi-GeV electron beams on metre-scale distances, and begin to reach beam qualities sufficient for EUV FELs. We show, that electron beams from plasma photocathodes many orders of magnitude brighter than state-of-the-art can be generated in plasma wakefield accelerators (PWFA), and then extracted, captured, transported and injected into undulators without quality loss. These ultrabright, sub-femtosecond electron beams can drive hard X-FELs near the cold beam limit to generate coherent X-ray pulses of attosecond-Angstrom class, reaching saturation after only 10 metres of undulator. This plasma-X-FEL opens pathways for novel photon science capabilities, such as unperturbed observation of electronic motion inside atoms at their natural time and length scale, and towards higher photon energies.