Free electron laser sideband instability reconsidered

Technical Report · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6032526

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 wiggler and a radiation field. The exact unperturbed orbits without sidebands are obtained for all particles and arbitrary separatrix width delta sub gamma. Integration in action-angle variables of the linearized Vlasov equation with perturbing sidebands over the unperturbed orbits yields the sideband gain for both trapped and untrapped particles. The unperturbed distribution f/sub 0/is in an adiabatic equilibrium with the main signal field. It is found that 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, i.e., the relative population of oscillation quanta h-bar omega sub b, omega sub b = bounce frequency around resonance. The shear d omega sub b/dJ, where J is the action variable, is stabilizing and distributions with gradients df/sub 0//dJ localized near the separatrix have the minimum growth rates. The structures and scaling of the unstable spectrum are different from previous results obtained for electrons localized at the bottom of the ponderomotive well.

• Research Organization: Naval Research Lab., Washington, DC (USA)
• OSTI ID: 6032526
• Report Number(s): AD-A-182153/7/XAB
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
AMPLIFICATION
BEAMS
DIMENSIONS
DISTRIBUTION
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
ELECTRON BEAMS
ENERGY TRANSFER
EQUATIONS
EQUIPMENT
FREE ELECTRON LASERS
GAIN
LASERS
LEPTON BEAMS
MAGNETS
ORBITS
PARTICLE BEAMS
PARTICLES
SIGNALS
SPECTRA
STABILIZATION
WIDTH
WIGGLER MAGNETS