Beam emittance growth in high intensity CW FEL injectors

We discuss beam emittance growth in high intensity CW FEL injectors due to space charges in DC laser guns, phase space bifurcation, skew-quad effect, longitudinal momentum modification by space charges in bends, and equipartitioning, etc. We generalize Kimʹs RF laser gun theory to DC laser guns. We discuss the traditional free energy theory of emittance growth. The best strategies for designing high-intensity CW FEL injectors are derived, and their application to the design analysis of the CEBAF 10 MeV DC laser gun CW FEL injector test stand is discussed.