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Optimisation of An HHG-Seeded Harmonic Cascade FEL Design for the NLS Project

Description: Optimization studies of an HHG-seeded harmonic cascade FEL design for the UK's proposed New Light Source (NLS) facility are presented. Three separate FELs are planned to meet the requirements for continuous coverage of the photon energy range 50-1000 eV with variable polarization, 20 fs pulse widths and good temporal coherence. The design uses an HHG seed source tuneable from 50-100 eV to provide direct FEL seeding in this range, and one or two stage harmonic cascades to reach the higher photon energies. Studies have been carried out to optimize a harmonic cascade FEL operating at 1 keV; topics investigated include modulator configuration, seed power level and ef- fects of the HHG seed structure. FEL simulations using realistic electron beam distributions are presented and tolerance to increased emittance has been considered.
Date: June 25, 2012
Creator: Dunning, David; /Daresbury; Thompson, Neil; /Daresbury; Bartolini, Riccardo; /Oxford U., JAI et al.
Partner: UNT Libraries Government Documents Department

Polarization Analysis for Seeded FELs in a Crossed-Planar Undulator

Description: The crossed-planar undulator is a promising scheme for full polarization control in x-ray FELs. For SASE FELs, it has been shown a maximum degree of circular polarization of about 80% is achievable at fundamental wavelength just before saturation. In this paper, we study the effectiveness of a crossed undulator for a seeded x-ray FEL. The degree of circular polarization for both the fundamental and the harmonic radiation are considered. Simulations with realistic beam distributions show that a degree of circular polarization of over 90% and 80% is obtainable at the fundamental and 2nd harmonic frequencies, respectively.
Date: June 25, 2012
Creator: Geng, Huiping; /SLAC; Ding, Yuantao; /SLAC; Huang, Zhirong; /SLAC et al.
Partner: UNT Libraries Government Documents Department