Gain in two stream free electron laser with planar wiggler and ion-channel guiding

The theory of two-stream free electron lasers (FELs) consisting of a relativistic two stream electron beam transported along the axis of a planar wiggler in the presence of an ion-channel guiding was proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristics of the linear gain and the normalized maximum gain are studied numerically. The comparison of the normalized gains by employing the axial magnetic field and ion-channel guiding in FEL has been studied numerically. The result shows that the maximum gain of the two-stream FEL is more than ten times stronger than conventional gain. Numerical results shown that in two-stream FEL with ion-channel guiding, the maximum value of maximum gain occurs at special range of two electron beam energy difference (Δγ = γ₂ − γ₁) and energy ratio (γ₁/γ₂). The results show that the normalized maximum gain in FEL with axial magnetic field is more than 20 times larger than that for using ion-channel guiding.