Figure 4
(Top) Pulse-resolved spectral distributions of a single pulse train with 380 FEL pulses recorded at a repetition rate of 1.0 MHz. The average pulse energy was 50 µJ (each pulse) and the pulse duration was about 100 fs (FWHM). (Bottom) As an example, three individual spectra are shown that have been offset vertically for better distinction. The fluctuations in the spectra result from the SASE amplification process and corroborate the need for pulse-resolved diagnostics at MHz repetition rates. |