Investigations on the effect of the electric fields inside the wigglers on the trajectory of the electron beam in the miniaturized FEL module

In the free electron laser (FEL) module, it is important to maintain the symmetrical profile of the e-beam propagation to obtain high-quality EM waves since the electromagnetic (EM) waves are generated directly from the acceleration of the electrons in the FEL module. We have investigated the motion of the electrons in the various types of wigglers of the miniaturized FEL module by using a 3D simulation tool. In the ring-type wiggler, we could obtain the e-beam profile bearing circular symmetry with respect to the optic axis. In the conventional planar-type wiggler, the e-beam went out of the optic axis as it propagated through the wiggler. We have demonstrated that such a deviation could be removed by applying the symmetrical bias to the electrode pairs, which is useful to improve the characteristics of the EM radiation.