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Proceedings Paper

Output characteristics of SASE-driven short-wavelength FELs
Author(s): William M. Fawley
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Paper Abstract

This paper investigates various properties of the 'microspikes' associated with self-amplified spontaneous emission (SASE) in a short wavelength free-electron laser (FEL). Using results from the 2-D numerical simulation code GINGER, we confirm theoretical predictions such as the convective group velocity in the exponential gain regime. In the saturated gain regime beyond the initial saturation, we find that the average radiation power continues to grow with an approximately linearly dependence upon undulator length. Moreover, the spectrum significantly broadens and shifts in wavelength to the redward direction, with P(omega) approaching a constant, asymptotic value. This is in marked contrast to the exponential gain regime where the spectrum steadily narrows, P(omega) grows, and the central wavelength remains constant with z. Via use of a spectrogram diagnostic S(omega, t), it appears that the radiation pattern in the saturated gain regime is composed of an ensemble of distinct 'sinews' whose widths (Delta) (lambda) remain approximately constant but whose central wavelengths can 'chirp' by varying a small extent with t.

Paper Details

Date Published: 15 May 1997
PDF: 10 pages
Proc. SPIE 2988, Free-Electron Laser Challenges, (15 May 1997); doi: 10.1117/12.274372
Show Author Affiliations
William M. Fawley, Lawrence Berkeley National Lab. (United States)

Published in SPIE Proceedings Vol. 2988:
Free-Electron Laser Challenges
Patrick G. O'Shea; Harold E. Bennett, Editor(s)

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