CERN Accelerating science

Article
Title	Scheme for Generation of Single 100 GW 300-as Pulse in the X-ray SASE FEL with the Use of a Few Cycles Optical Pulse from Ti : sapphire Laser System
Author(s)	Saldin, Evgeny L ; Schneidmiller, Evgeny A ; Yurkov, Mikhail V
Affiliation	(DESY, Hamburg)
Publication	2004
In:	26th International Free Electron Laser Conference and 11th FEL User Workshop 2004, Trieste, Italy, 29 Aug - 3 Sep 2004, pp.e-proc. MOBOS02
Subject category	Accelerators and Storage Rings
Abstract	Femtosecond optical pulse interacts with the electron beam in the two-period undulator and produces energy modulation within a slice of the electron bunch. Then the electron beam enters the first part of the X-ray undulator and produces SASE radiation with 100 MW-level power. Due to energy modulation the frequency is correlated to the longitudinal position, and the largest frequency offset corresponds to a single-spike pulse in the time domain which is confined to one half-oscillation period near the central peak electron energy. After the first undulator the electron beam is guided through a magnetic delay which we use to position the X-ray spike with the largest frequency offset at the "fresh" part of the electron bunch. After the chicane the electron beam and the radiation enter the second undulator which is resonant with the offset frequency where only a single (300 as duration) spike grows rapidly. The final part of the undulator is a tapered section allowing to achieve maximum output power 100-150 GW in 0.15 nm wavelength range.