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Nonlinear harmonic generation in free-electron lasers with helical wigglers
H P Freund1, P G O'Shea, S G Biedron
1Science Applications International Corporation, McLean, VA 22102, USA.
Physical Review Letters
|March 24, 2005
Summary
Nonlinear harmonic generation (NHG) is substantial in helical wigglers, contrary to popular belief. This study shows that both even and odd harmonics have comparable intensities, challenging previous assumptions.
Area of Science:
- Plasma Physics
- Accelerator Physics
- Nonlinear Optics
Background:
- Harmonic generation in wigglers is crucial for free-electron lasers (FELs).
- Linear harmonic generation (LHG) is understood in helical wigglers, driven by azimuthal resonance.
- Nonlinear harmonic generation (NHG) has been studied in planar wigglers but not helical ones.
Purpose of the Study:
- To analyze nonlinear harmonic generation (NHG) in helical wigglers.
- To investigate the characteristics of NHG in 3D helical wiggler configurations.
- To compare the intensities of even and odd harmonics generated in helical wigglers.
Main Methods:
- Modification of the 3D simulation code 'medusa' to study NHG in helical wigglers.
- 3D simulations to model electron beam dynamics and harmonic generation.
- Analysis of simulation results to quantify harmonic intensities.
Main Results:
- Nonlinear harmonic generation (NHG) is found to be substantial in helical wigglers.
- Both even and odd harmonics exhibit comparable intensities.
- The behavior of NHG in helical wigglers differs significantly from planar configurations.
Conclusions:
- Helical wigglers can support significant nonlinear harmonic generation (NHG).
- The assumption of harmonic suppression in helical wigglers is challenged.
- Further research into NHG in helical configurations is warranted for FEL applications.