A multi-frequency 2D SASE FEL simulation code has been developed using the
Source Dependent Expansion (SDE) method. With this code we calculated the e
volution of the radiation amplitude and the spectrum of a SASE FEL using th
e beam parameters of FELI and the micro-wiggler developed by ILT/ILE/OSU. T
he effect of beam energy spread is also clarified. (C) 2000 Elsevier Scienc
e B.V. All rights reserved.