Efficient generation of short and high-power x-ray free-electron-laser pulses based on superradiance with a transversely tilted beam

X-ray free electron lasers (XFELs) are innovative research tools able to produce high-power and short radiation pulses for multiple scientific applications. We present a new method to produce XFEL radiation with much higher power and shorter pulse lengths than the ones obtained at standard XFEL facilities. This will enable new kinds of experiments in scientific fields such as nonlinear optics and bioimaging. The scheme is based on introducing a transverse tilt to the electron beam, thus limiting the fraction of the bunch able to produce XFEL radiation. In the first part of the undulator beam line only the tail of the electron bunch lases. Then, by properly delaying and correcting the trajectory of the electron beam between some undulator modules, all the electrons can contribute to the amplification of a very short XFEL pulse. Apart from being efficient, our method is flexible since by tuning the tilt amplitude one can obtain shorter or more energetic XFEL pulses. The scheme can readily be applied since, besides the standard components of an XFEL facility, it only needs small chicanes between certain undulator modules. We have confirmed the validity of our proposal with numerical simulations done for the SwissFEL case.