Regenerative gain and sideband instability in a Raman free-electron laser
A parametric study of gain in a millimeter-wave Raman free-electron laser oscillator and comparisons with linear theory are carried out. The intense (1kA/cm/sup 2/), relativistic (600-800keV), cold electron beam employed is guided by a 9.45 kG magnetic field through a 1.45-cm period, 50-cm long uniform undulator. Operation at <1kG pump field results in a <10% electron quiver velocity. The laser power output was measured at approx. =3MW corresponding to an efficiency of 4% and tunability in the 90-to 170-GHz frequency range was achieved with a narrow linewidth. Using a new technique, linear small-signal growth rates were unfolded from oscillator startup delays. Excellent agreement is found with three-dimensional small-signal calculations. The first experimental evidence of a predicted sideband instability in the saturated Raman FEL spectrum is presented. A new method for the control and possible suppression of the sidebands by elimination of pulse slippage is demonstrated.
- Research Organization:
- Columbia Univ., New York (USA)
- OSTI ID:
- 7074879
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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