Fig. 1: Schematic representation of the self-chirping operation mode at the European XFEL.
From: Terawatt-attosecond hard X-ray free-electron laser at high repetition rate
The layout includes a photocathode electron gun, a 1.3 GHz superconducting booster, a 3.9 GHz third harmonic linearizer, a laser heater (not shown), three bunch compressors (BC0, BC1 and BC2), three superconducting linac sections (L1, L2 and L3), a collimation section and an arc section for transporting the electron beam to the SASE2 undulator. The European XFEL offers the ability to deliver ten bursts (trains) of electron beams every second. Each train is characterized by its flexibility in the number of electron bunches it contains, which can vary from a single bunch to a maximum of 2,700 bunches. The generated X-ray pulse, shown in purple, is analysed by the X-ray gas monitor66,67 and the HIREX single-shot spectrometer68, both depicted in grey and situated downstream from the undulator. a–c, Simulated longitudinal phase spaces of the electron beam at the exits of BC2 (a), the collimation section (b) and the arc section (c), with the beam head to the left. d,e, Simulated XFEL performance at 9 keV including the temporal profile (d) with an FWHM duration of around 110 as and a peak power of 1 TW and the corresponding spectrum (e) with an FWHM bandwidth of about 16 eV.
