Plasma-driven XFEL near the cold beam limit

Plasma-accelerator driven free-electron-lasers require electron beams of the highest quality, in order to overcome the emittance and energy spread thresholds for micro-bunching and lasing. The plasma photocathode wakefield accelerator mechanism [1] promises electron beams of ultralow emittance and low energy spread [2]. This may allow driving XFEL towards sub-Angstrom wavelengths, near the single-spike attosecond pulse, cold-beam limit, at only few GeV electron energies [3]. The plasma photocathode principle was shown with beams from a linac and, via the hybrid LWFA->PWFA approach [4], recently also with electron beams produced by compact laser wakefield accelerators [5]. This contribution will present the status of these developments, their prospects towards democratization of XFELs, and impact for large projects such as the UKXFEL and EuPRAXIA. [1] Deng, Karger et al., Nat. Phys. 15, 1156–1160 (2019) [2] Manahan, Habib et al., Nat. Comm. 8, 15705 (2017) [3] Habib et al., Nat. Comm. 14,1054 (2023) [4] Kurz, Heinemann et al., Nat. Comm.12, 2895 (2021) [5] P. Ufer, A. Nutter et al., under review