A COMPARISON BETWEEN HIGH-GAIN HARMONIC GENERATION AND SELF-SEEDING FOR THE PRODUCTION OF NARROWBANDWIDTH RADIATION IN A FREE-ELECTRON LASER

摘要

In this paper we investigate and compare the proper-ties of two narrow bandwidth free-electron laser (FEL) schemes, one using self-seeding and the other high gain harmonic generation (HGHG). The two systems have been thoroughly studied analytically and numerically in the past. The aim of this work is to compare their performances when the FEL is driven by an electron beam with non-ideal properties, thus including effects such as shot-to-shot en-ergy fluctuations and nonlinear energy chirp. In both cases non-linearities produce a bandwidth larger than the Fourier transform limited value. However the results of our analy-sis indicate that the self-seeding scheme is less affected by non-ideal electron phase space distribution than the HGHG seeding scheme and thus has a larger number of FEL pho-tons per unit frequency. 179