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Free-electron laser design operating in the SASE mode using the PALADIN wiggler

It is commonly assumed that a matched electron beam optimizes free-electron laser (FEL) performance; however, this assumption has not been proven for FELs operating in the high gain regime. We test this hypothesis using a 3D multimode analysis which is capable of modeling matched and unmatched electron beams and for design parameters suitable for a SASE experiment at Duke University using the PALADIN wiggler. The gain length predicted for a matched beam is in good agreement with analytic theory. Further, the simulation indicates that while the gain length is optimized for a matched beam the saturated power is not necessarily optimized.