Numerical simulations of chirped pulse amplification at FEL

Linear chirped pulse amplification at single pass free-electron laser（FEL） amplifier has been performed by means of the modified 1D time-dependent FEL code，and the averaged output power of pulses as functions of undulator length at different chirped parameters is given through numerical simulations．The peak power and width of the final compressed pulse with different chirped parameters have been computed．The results of numerical stimulations show that the peak power and width of the final compressed pulse are influenced mainly by the chirped parameter and the FEL bandwidth，and compressing the pulse amplified by single pass FEL is a feasible means of producing ultra short FEL pulses．