Design of a hybrid undulator for free-electron lasers

This work presents the design of a hybrid undulator for an amplifier free-electron laser (FEL) that is composed of a periodic magnetic structure of permanent magnets and soft ferromagnetic poles. The basic parameters of the project were obtained by means of computational calculations with a two-dimensional code for the magnetic field and numerical integration of the small-signal gain of the FEL, taking into account four harmonics of the magnetic field.