A method for generating femtosecond-duration x-ray pulses with a free-electron laser is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped x-ray pulse by self-amplified spontaneous emission. A short temporal pulse is created by use of a monochromator to select a narrow radiation bandwidth. A second undulator is used to amplify the short-duration radiation. The radiation characteristics produced by a chirped-beam two-stage free-electron laser are calculated, and the performance of the chirped-beam two-stage option for the Linac Coherent Light Source is considered. /home/httpd/docserver/releases/20080613005430/public/paper/file/419/schroeder_2002_0416.pdf schroeder_2002_0416.pdf 1 419 0 2002 Journal of the Optical Society of America B-Optical Physics 416 2007-10-22T17:04:50-07:00 1782-89 2002