VARIABLE POLARIZED HARMONIC-UNDULATOR FREE ELECTRON LASER AND EFFECT OF BEAM ENERGY SPREAD

In the recent past Variable Polarized Harmonic Undulators are proposed for obtain radiation at all polarization. The scheme has been further modified to variable polarized harmonic undulator scheme. The scheme consists of two identical linear polarized magnets with high permeable shim in the gap of the undulator magnets. In this paper we include the important effects of beam energy spread and the variable polarized harmonic undulator radiation and free electron laser gain. We have considered both single and two-peak gaussian beam energy distribution to calculate intensity and gain reduction. We show that the variable polarized harmonic scheme compensates the undesired effects of the beam energy spread in comparison to the standard variable polarized undulator scheme.