Numerical study of focusing lattice impact on the saturation length and power in SASE FEL

Abstract

An adjustment of the electron and photon beams angular and transverse phase-space characteristics along the undulator line and the resonant interaction of the electron beam with co-propagating radiation are of basic conditions to drive the SASE-FEL process. In the real facility the SASE-FEL process can degrade due to electron beam orbit distortion caused by quadrupole misalignments in undulator section. Both those issues are in dependence of the focusing lattice arrangement in undulator section. In this paper the comparative study of the SASE-FEL process for conventional FODO focusing lattices, the undulator section arrangement with central focusing lattice and the FEL performance without external focusing system are presented. The impact of the quadrupole misalignments on the radiation saturation length and power for different focusing systems is analyzed. The numerical simulations for European XFEL project are given. © 2011 IOP Publishing Ltd and SISSA.