CERN Accelerating science

Article
Title	Frequency Modulation Effects in the Photoinjector for the FERMI @ Elettra FEL
Author(s)	Trovò, M ; Danailov, M B ; Penco, G
Affiliation	(ELETTRA, Basovizza, Trieste MIT, Middleton, Massachusetts LBNL, Berkeley, California)
Publication	2005
In:	27th International Conference on Free Electron Lasers, Palo Alto, CA, USA, 21 - 26 Aug 2005, pp.616
Subject category	Accelerators and Storage Rings
Abstract	In the framework of the FERMI@ELETTRA project, aimed to build an X-ray FEL source, a crucial role is played by the electron source, which has to produce a very high quality bunch, in terms of low emittance and uncorrelated energy spread. We have investigated the effects of low- (100-300 5m) and high- ( 10<sup><font size="-1">-50</font></sup> 5m) frequency modulation of the beam charge deriving from intensity modulation of the laser pulse incident on the photocathode on the downstream beam distribution. Following other proposals, we have investigated the use of a short laser 'heater' to increase the effective incoherent energy spread and reduce the gain in the longitudinal density modulation instability. We present results from simulation of the beam generation at the photocathode, and transport through the photoinjector, initial acceleration modules and the laser heater.