Multicolor x-ray free-electron laser generation using optical klystron for multiframe diffraction imaging

X-ray free-electron lasers (XFELs) of high brightness have opened new opportunities for exploring ultrafast dynamical processes in matter, enabling imaging and movies of single molecules and particles at atomic resolution. In this paper, we present a straightforward method for multiframe diffraction imaging, using the whole electron beam to generate four-color XFEL pulses with adjustable wavelength separation and time delay. The optical klystron scheme is introduced to enhance the FEL intensity and reduce the total length of the undulators. The time delay is tuned via a magnetic chicane between the undulators for different colors. Using parameters of SHINE, start-to-end simulations demonstrate the effectiveness and tunability of our method, achieving representative results such as time delays of hundreds of femtoseconds and four-color XFEL pulses spanning 1.8 to 2.7 nm with 0.3 nm intervals. The proposed scheme enables the recording of multiframe diffraction images in a single exposure, providing a new perspective for ultrafast molecular and atomic dynamics studies.