LBNL, Berkeley, California, USA
Advances in numerical methods for free-electron-laser~(FEL) simulation under wiggler period averaging~(WPA) are presented. First, WPA is generalized using perturbation Lie map method. The conventional WPA is identified as the leading order contribution. Next, a widely used shot-noise modeling method is improved along with a particle migration scheme across the numerical mesh. The artificial shot noise arising from particle migration is suppressed. The improved model also allows using arbitrary mesh size, slippage resolution, and integration step size. These advances will improve modeling of longitudinal beam profile evolution for fast FEL simulation.
