Fig. 5: Performance of different HXRSS configurations at 7.5 keV.
From: Cascaded hard X-ray self-seeded free-electron laser at megahertz repetition rate
a, Evolution of the notch down the train with an incident SASE energy of 40 μJ on the second crystal X2. b, Spectrum of the incident pulse at the second crystal X2, averaged over 1,000 pulses. The incident energy is estimated in the several microjoules level. The self-seeded spectral peak at Ec = 7,440.1 eV incident on X2 has an FWHM bandwidth of 1.2 eV and is about five times higher than the SASE peak. c, Colour-coded average spectrum, as a function of the position down trains of 100 pulses, simultaneously seeding with C1 and C2 (one event in four was recorded by the spectrometer). d, Comparison of the best seeded performances with the first chicane C1 (blue), and with the first and second chicanes C1 + C2 (simultaneous seeding) (orange). Both spectra are averaged over 1,000 pulses.
