Performance simulation and parameter optimization for high gain short wavelength FEL amplifiers

The designers of short wavelength FELs must rely on theoretical and numerical predictions since no experimental data are available for this region. The numerical codes which have been developed, and are being used to design systems at SLAC, BNL, Duke, LBL, CEBAF, LANL and UCLA among others, contain our best theoretical understanding of these systems. This paper analyses the present simulation capabilities for short wavelength designs. We discuss how codes are used to design these new systems, which aspects of our models are well implemented and which are not, methods of verifying the models, comparison with experiment, and finally comments on extrapolating to short wavelengths.