CERN Accelerating science

Article
Report number	SLAC-PUB-10713
Title	Current-enhanced SASE using an optical laser and its application to the LCLS
Author(s)	Zholents, A A ; Emma, P ; Fawley, W M ; Huang, Z ; Reiche, S ; Stupakov, G
Affiliation	(LBL, Berkeley) ; (SLAC) ; (UCLA)
Publication	2004
Imprint	Sep 2004
Number of pages	4
In:	26th International Free Electron Laser Conference and 11th FEL User Workshop 2004, Trieste, Italy, 29 Aug - 3 Sep 2004, pp.e-proc. WEBOS01
Abstract	We propose a significant enhancement of the electron peak current entering a SASE undulator by inducing an energy modulation in an upstream wiggler magnet via resonant interaction with an optical laser, followed by micro-bunching of the energy-modulated electrons at the accelerator exit. This current enhancement allows a considerable reduction of the FEL gain length. The x-ray output consists of a series of uniformly spaced spikes, each spike being temporally coherent. The duration of this series is controlled by the laser pulse and in principle can be narrowed down to just a single,  100-attosecond spike. Given potentially absolute temporal synchronization of the x-ray spikes to the energy-modulating laser pulse, this scheme naturally makes pump-probe experiments available to SASE FEL’s. We also study various detrimental effects related to the high electron peak current and discuss potential cures. We suggest a possible operational scenario for the LCLS optimized with respect to the choice of the modulating laser beam and electron beam parameters. Numerical simulations are provided.

Corresponding record in: Inspire