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S. Chen

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Last Name: Chen

Full Name: S. Chen

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2 papers
title: RADIATION PROPERTIES OF TAPERED HARD X-RAY FREE ELECTRON LASERS
format: conference proceeding
conference: FEL 2014 36th
year: 2014
6 authors: C. Emma | C. Pellegrini | J. Wu | K. Fang | S. Chen | S. Serkez
abstract: We perform an analysis of the transverse coherence of the radiation from a TW level tapered hard X-ray Free Electron Laser (FEL). The radiation properties of the FEL are studied for a Gaussian, parabolic and uniform transverse electron beam density profile in a 200 m undulator at a resonant wavelength of 1.5 Å. Simulations performed using the 3-D FEL particle code GENESIS show that diffraction of the radiation occurs due to a reduction in optical guiding in the tapered section of the undulator. This results in an increasing transverse coherence for all three transverse electron beam profiles. We determine that for each case considered the radiation coherence area is much larger than the electron beam spot size, making coherent diffraction imaging experiments possible for TW X-ray FELs.
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title: Terawatt x-ray free-electron-laser optimization by transverse electron distribution shaping
format: journal article
publisher: Physical Review Accelerators and Beams
year: 2014
6 authors: C. Emma | J. Wu | K. Fang | S. Chen | S. Serkez | C. Pellegrini
abstract: We study the dependence of the peak power of a 1.5 Å Terawatt (TW), tapered x-ray free-electron laser (FEL) on the transverse electron density distribution. Multidimensional optimization schemes for TW hard x-ray free-electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to a Gaussian distribution. The optimizations are performed for a 200 m undulator and a resonant wavelength of λr=¼1.5Å using the fully three-dimensional FEL particle code GENESIS. The study shows that the flatter transverse electron distributions enhance optical guiding in the tapered section of the undulator and increase the maximum radiation power from a maximum of 1.56 TW for a transversely Gaussian beam to 2.26 TW for the parabolic case and 2.63 TW for the uniform case. Spectral data also shows a 30% – 70% reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian. An analysis of the transverse coherence of the radiation shows the coherence area to be much larger than the beam spotsize for all three distributions, making coherent diffraction imaging experiments possible.
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