FEL gain reduction due to wiggler errors

We report the results of a study comparing an analytical theory of wiggler errors in free-electron lasers (FEL's) to a numerical simulation. The different mechanisms of reduction in FEL gain due to wiggler errors are reviewed, and in each case analytical results are compared with computer simulation and shown to be in good agreement. We present a study of the proposed UV FEL user facility at BNL and determine the implications of the wiggler errors on the FEL design. >