
Accession Number : ADA186952
Title : The Structure of the Sideband Spectrum in Free Electron Lasers.
Descriptive Note : Interim rept.,
Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC
Personal Author(s) : Riyopoulos, S. ; Tang, C. M.
Report Date : 19 NOV 1987
Pagination or Media Count : 67
Abstract : The onedimensional, fasttime 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 actionangle 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 hbar, 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.
Descriptors : *FREE ELECTRON LASERS, *SIDEBANDS, *EMISSION SPECTRA, DISTRIBUTION, ELECTRONS, GROWTH(GENERAL), HAMILTONIAN FUNCTIONS, HEIGHT, KINETIC THEORY, LINEARITY, LOW FREQUENCY, ORBITS, POPULATION, RADIATION, RATES, STABILIZATION, SYNCHROTRONS, YIELD.
Subject Categories : Lasers and Masers
Atomic and Molecular Physics and Spectroscopy
Distribution Statement : APPROVED FOR PUBLIC RELEASE