Simulations of the microbunching instability in beam deliverysystems for free electron lasers

In this paper, we examine the growth of the microbunchinginstability in the electron beam delivery system of a free electron laser(FEL). We present the results of two sets of simulations, one conductedusing a direct Vlasov solver, the other using a particle-in-cell codeImpact-Z with the number of simulation macroparticles ranging up to 100million. Discussion is focused on the details of longitudinal dynamicsand on numerical values of uncorrelated (slice) energy spread atdifferent points in the lattice. In particular, we assess the efficacy oflaser heater in suppression of the instability, and look at the interplaybetween physical and numerical noise in particle-basedsimulations