• H. Freund, W.H. Miner
  SAIC, McLean
• S.V. Benson, M.D. Shinn
  JLAB, Newport News, Virginia
• K.-J. Boller, P.J.M. van der Slot
  Mesa+, Enschede

We describe a procedure for the simulation of free-electron laser oscillators. The simulation uses a combination of the MEDUSA simulation code for the FEL and the OPC code to model the resonator. The simulations are compared with recent observations of the oscillator at the Thomas Jefferson National Accelerator Facility and are in substantial agreement with the experiment.

Slides

• X.J. Wang, D.A. Harder, J.B. Murphy, H.J. Qian, Y. Shen, X. Yang
  BNL, Upton, Long Island, New York
• H. Freund, W.H. Miner
  SAIC, McLean

We report the first experimental characterization of efficiency and spectrum enhancement in a laser-seeded free-electron laser (FEL) using a tapered undulator. Output and spectra in the fundamental and 3rd harmonic were measured versus distance for uniform and tapered undulators. With a 4% field taper over 3 m, a 300% (50%) increase in the fundamental (3rd harmonic) output was observed. A significant improvement in the spectra with the elimination of side-bands was observed using a tapered undulator. The experiment is in good agreement with predictions using the MEDUSA simulation code.

Slides