An analytical study of a planar wiggler FEL in the cold electron-beam strong-pump regime is presented. Such an FEL can lase at high odd harmonics due to the periodic variation in the longitudinal electron velocity, and can also emit superradiant emission at harmonic frequencies. Based on a parametric interaction approach, we develop an extended gain dispersion equation for a laser operating at the fundamental or high harmonics taking collective effects (Raman regime) into account. The analysis applies also to the case aw (βγ) ∼ 1, where the customary use of the Taylor expansion of V2 does not apply. This case is of interest mostly for mildly relativistic FELs, and allows excitation of very high harmonics.
|Number of pages||6|
|Journal||Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|
|State||Published - 1 Jul 1991|