Structure of the sideband spectrum in free-electron lasers. Interim report

Technical Report · Thu Nov 19 04:00:00 EST 1987

OSTI ID:5647184

Riyopoulos, S; Tang, C M

The one-dimensional, fast-time averaged Hamiltonian is derived in a free-electron laser (FEL) for electrons passing through a constant parameter wiggler and a radiation field. The exact unperturbed orbits without sidebands are obtained for all particles and arbitrary separatrix height delta sub gamma. Integration, in action-angle variables, of the linearized kinetic equation with perturbing sidebands over the unperturbed orbits yields the sideband growth rate including both trapped and untrapped particles. The structure and scaling of the unstable spectrum are different from previous results obtained for electrons localized at the bottom of the ponderomotive well. Upper and lower sidebands that are symmetric relative to the FEL frequency have opposite growth rates. There is no differentiation in the magnitude of the gain between upper and lower sidebands. The stability is determined by the sign of df sub 0/d omega sub b, the relative population of quantized oscillators with energy quantum h-bar, omega sub b where omega sub b is the synchrotron frequency in resonance with the sideband. The shear d omega sub b/dJ, where J is the action variable, is stabilizing and distributions wth gradients of df sub 0/dJ localized near the separatrix have the minimum growth rates.

• Research Organization: Naval Research Lab., Washington, DC (USA)
• OSTI ID: 5647184
• Report Number(s): AD-A-186952/8/XAB; NRL-MR-6118
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
BAND THEORY
DIMENSIONS
DOCUMENT TYPES
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
EMISSION SPECTRA
EQUIPMENT
FREE ELECTRON LASERS
HEIGHT
LASERS
MAGNETS
PROGRESS REPORT
SPECTRA
STABILIZATION
WIGGLER MAGNETS