Enhanced X-ray free-electron-laser performance from tilted electron beams

A transverse tilt of the electron beam is normally not wanted in X-ray free-electron-laser (XFEL) facilities, since in a typical undulator beamline with quadrupole magnets only the central part of the beam with negligibly small betatron oscillations will produce significant XFEL radiation. In this work we present special configurations for which a transverse tilt can actually be used to improve the XFEL performance. In particular, we show with numerical simulations how tilted electron beams can be employed to generate two-color XFEL pulses, ultra-large-bandwidth XFEL radiation, and high-power and short duration XFEL radiation. We present and assess different mechanisms to generate the transverse tilt, namely a transverse deflecting structure, transverse wakeflelds, and introducing dispersion to an energy-chirped beam. (C) 2016 Elsevier B.V. All rights reserved.