Dynamical diffraction of ultrashort X-ray free-electron laser pulses

Calculations are presented for the femtosecond time-evolution of intensitie s of beams diffracted by perfect Bragg crystals illuminated with radiation expected from X-ray free-electron lasers (XFELs) operating through the self -amplified spontaneous emission (SASE) process. After examining the case of transient diffraction of an electromagnetic delta-function impulse through flat, single- and double-crystal monochromators, the propagation of a 280 fs-duration SASE XFEL pulse of 8 keV photons through the same optics is dis cussed. The alteration of the sub-femtosecond spiky microbunched temporal s tructure of the XFEL pulse after it passes through the system is shown for both low-order (broad bandwidth) and high-order (narrow bandwidth) crystal reflections. Finally, the shot-to-shot statistical fluctuations of the inte grated diffracted intensity is simulated. Implications of these results for XFEL applications are addressed.