Electron beam matching and its influence on the performance of high-gain free-electron lasers

We consider the influence of electron beam on the performance of high-gain FELs. We test this hypothesis for a SASE configuration using a 3-D multimode simulation. The gain length predicted for a matched beam agrees well with analytic theory, and the simulation indicates that while the gain length is optimized for a matched beam the saturated power may not be optimized. In previous work we have considered a flat-top beam model while we also consider a Gaussian beam model, and conclude the two are in substantial agreement.