Output characteristics of SASE-driven short-wavelength FELs

William M. Fawley

doi:10.1117/12.274372

15 May 1997 Output characteristics of SASE-driven short-wavelength FELs

William M. Fawley

Proceedings Volume 2988, Free-Electron Laser Challenges; (1997) https://doi.org/10.1117/12.274372
Event: Photonics West '97, 1997, San Jose, CA, United States

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.

Citation Download Citation

William M. Fawley "Output characteristics of SASE-driven short-wavelength FELs", Proc. SPIE 2988, Free-Electron Laser Challenges, (15 May 1997); https://doi.org/10.1117/12.274372

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