Free Electron Lasers Using Stable-Unstable Ring Resonators

摘要

The free electron laser (FEL) simulation code FELEX is used to examine the operation of stable-unstable FEL resonators. These resonators are stable along one transverse axis and unstable along the orthogonal transverse axis. The simulations utilize a ring resonator with an intracavity focus in the unstable plane near the center of the wiggler (close to the same axial position as the waist in the stable plane) thereby enhancing the coupling between the optical and electron beams. Asymmetric output scraping is performed in the back leg of the ring using a reflective mirror inserted from one side of the unstable axis. Resonators with relatively low equivalent Fresnel number (/vert bar/N/sub eq//vert bar/ less than or equal to 10) and magnification (/vert bar/M/sub x//vert bar/ approx. = 1.2) are examined. Optical characteristics including the cavity mode profile at various positions inside the resonator are shown. 8 refs., 8 figs. (ERA citation 14:013332)