Fig. 1: Layout of the two-chicane HXRSS setup at the SASE2 undulator of European XFEL.
From: Cascaded hard X-ray self-seeded free-electron laser at megahertz repetition rate
The setup comprises three undulator segments (U1, U2 and U3) and two monochromatization stages (consisting of a combination of a four-dipole chicane C1 (C2) and a thin diamond crystal X1 (X2)). a, A narrow-bandwidth notch is created in the spectrum by means of a thin diamond crystal corresponding to the transmission. b, The corresponding intensity profile in the time domain consists of a SASE pulse followed by a trailing wake: red line, calculated (head of the pulse to the right); blue data points, spectrometer peak intensity measured by a delay scan of chicane C2 at 9 keV with a C*(004) reflection. Data are presented as mean values ± standard error of the mean (s.e.m.); sample size, n = 100. The electron bunch (cyan) is overlapped with the seed and amplifies it up to saturation and beyond in U3. The generated X-ray pulse (yellow) is characterized by the XGM pulse energy monitor and the HIREX single-shot spectrometer (grey), located in the photon beam transport approximately 500 m downstream of the undulator.
