Fig. 3: HXRSS performance during user delivery at a high repetition rate.
From: Cascaded hard X-ray self-seeded free-electron laser at megahertz repetition rate
a, Spectra of every fourth pulse within a single train at 2.25 MHz at Ec = 8,996 eV. There is neither a shift in the central photon energy nor a change in the spectrum along the train, indicating the absence of heat-load effects. b, Comparison between seeded and SASE pulses, averaged over 1,000 pulses, with a single pulse per train, for an overall value of ten pulses per second. The spectral density in the seeded mode increased by a factor of 4.5. The central energy of the seeded signal was Ec with a single-shot FWHM bandwidth of about 0.9 eV. The SASE central energy was slightly shifted to Ec2 = 8,999.0 eV with an FWHM bandwidth of about 19.2 eV. c, Pulse energy as a function of pulse number after orbit correction according to the centre of the pulse train in the self-seeding configuration. The red dots are average values; the half-width of the coloured band indicates the standard deviation computed from 1,000 trains.
