Recent theoretical results for an rf-linac-driven XUV free electron laser☆

Abstract We present new theoretical results for the characteristics and performance of an rf-linac-driven XUV free electron laser. These results fall into two categories: (1) the dependence of the small-signal gain upon the transverse phase-space distribution of the electron beam and the geometry of the optical resonator, and (2) the optical spectral bandwidth. Concerning (1) we discuss, and present 3-D numerical calculations of, the small-signal gains expected for different phase-space distributions. The gain also varies substantially with the Rayleigh range of the optical resonator. Thus, for maximum small-signal gain, the design of the resonator is coupled to the electron beam characteristics. Concerning (2), we discuss conditions under which there is a spectral broadening of the optical pulse due to the development of sidebands. The basis of these studies are 1-D finite pulse, and 3-D periodic boundary condition, numerical computer codes.