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Shen, Y.

Paper Title Page
TUPMS088 Efficiency Enhancement Experiment with a Tapered Undulator in a Single-pass Seeded FEL at the NSLS SDL 1371
 
  • T. Watanabe, D. A. Harder, R. K. Li, J. B. Murphy, G. Rakowsky, Y. Shen, X. J. Wang
    BNL, Upton, Long Island, New York
  
  Funding: This work is supported by the Office of Naval Research under contract No. N0002405MP70325 and U. S. Department of Energy under contract No. DE-AC02-98CH1-886.

We report the experimental characterization of the FEL efficiency enhancement using a tapered undulator in a single-pass seeded FEL amplifier at the NSLS SDL. The last 3 m of the 10 m NISUS undulator was linearly tapered so that the magnetic field strength at the end of the undulator was reduced by 5 %. The FEL energy gain along the undulator was measured for both the tapered and un-tapered undulator. The FEL energy with the taper was measured to be about 3.2 times higher than that without the taper. We also experimentally characterized the spectrum and the transverse distribution of the FEL light for both the tapered and un-tapered undulator. The experimental results are compared with the numerical simulation code, GENESIS 1.3.