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Phys. Rev. Lett. 94, 074802 (2005) [4 pages]

Nonlinear Harmonic Generation in Free-Electron Lasers with Helical Wigglers

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H. P. Freund1, P. G. O'Shea2, and S. G. Biedron3
1Science Applications International Corporation, McLean, VA 22102, USA
2University of Maryland, College Park, MD 20742, USA
3Energy Systems Division, Argonne National Laboratory, Argonne, IL 60439, USA

Received 2 August 2004; published 25 February 2005

It is widely believed that harmonics are suppressed in helical wigglers. However, linear harmonic generation (LHG) occurs by an azimuthal resonance that excites circularly polarized, off-axis waves, where the hth harmonic varies as exp⁡(ihθ). Nonlinear harmonic generation (NHG) is driven by bunching at the fundamental and has different properites from LHG. While NHG has been studied in planar wigglers, there has been no analysis of NHG in helical wigglers. The 3D simulation code medusa has been modified for this purpose, and it is shown that NHG is substantial in helical wigglers and that the even and odd harmonics have comparable intensities.

© 2005 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.94.074802
DOI:
10.1103/PhysRevLett.94.074802
PACS:
41.60.Cr, 52.59.Rz