Venturini, M. TUC01 simulation laser bunching FEL linac 2015 2015-12 The microbunching instability is a pervasive occurrence when high brightness electron beams are accelerated and transported through dispersive sections like bunch-compression chicanes or distributions beamlines. If uncontrolled the instability can severely compromise the performance of x-ray FELs, where beam high brightness is crucial. In this talk we discuss how consideration of the microbunching instability is informing the LCLS-II design and determining the specifications for the laser heater and transport lines. We also review some of the expected and not so-expected phenomena that we have encountered while carrying out high-resolution macroparticle simulations of the instability and the analytical models we have developed to interpret the numerical results.