A fast and light tool for partially-coherent beamline simulations in fourth generation storage rings based on coherent mode decomposition

A new algorithm to perform coherent mode decomposition of the undulator radiation is proposed. It is based in separating the horizontal and vertical directions, reducing the problem by working with one-dimension wavefronts. The validity conditions of this approximation are discussed. Simulations require low computer resources, and run interactively in a laptop. We study the focusing with lenses of the radiation emitted by an undulator in a fourth-generation storage ring (EBS-ESRF). Results are compared against multiple optics packages implementing a variety of methods for dealing with partial coherence: full 2D coherent mode decomposition, Monte-Carlo combination of wavefronts from electrons entering the undulator with different initial conditions, and hybrid ray-tracing correcting geometrical optics with wave optics.