NSLS-II Colloquium

Future X-ray Free-Electron Lasers (XFELs) will produce coherent X-rays with energies greater than 20 keV, which will require electron beams with lower laboratory emittances and relative energy spreads than those in current XFELs such as LCLS or the European XFEL. To satisfy this requirement, electron beam energies will need to be higher than in current XFEL designs if conventional accelerator architectures are used, leading to increased construction and operation costs. To provide design margin for these future XFELs at the lowest possible electron beam energies, novel schemes may be employed to suppress or eliminate the present limitations in XFEL performance. This talk will describe the dominant electron-beam instabilities and other effects (coherent synchrotron radiation, undulator resistive wall wakes, microbunch instability, and intrabeam scattering) and will describe a novel accelerator architecture to suppress the worst effects from them. Design trades to improve performance at lower beam energies will also be described. The baseline parameters for the proposed XFEL at Los Alamos (the MaRIE XFEL, designed to have an X-ray energy of 42 keV) will be used to illustrate these effects.