Macroclump model of the nonlinear evolution of the sideband instability in a helical wiggler free-electron laser

Journal Article · Sat Dec 01 04:00:00 EST 1990 · Physics of Fluids B; (USA)

DOI:https://doi.org/10.1063/1.859221· OSTI ID:5992534

Yang, T B; Davidson, R C ^[1]

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1. Plasma Fusion Center, Massachusetts Institute of Technology, Cambridge, MA (USA)

The nonlinear evolution of a helical wiggler, free-electron laser is investigated within the framework of a macroclump model for the trapped electrons. The model describes the nonlinear evolution of a right-circularly polarized electromagnetic wave with frequency {omega}{sub {ital s}} and wave number {ital k}{sub {ital s}}, and slowly varying amplitude {ital {cflx a}}{sub {ital s}}({ital z},{ital t}) and phase {delta}{sub {ital s}}({ital z},{ital t}) (eikonal approximation). The model further assumes that the trapped electrons can be treated as tightly bunched macroclumps that interact coherently with the radiation field. The analysis is carried out in the ponderomotive frame, which leads to a substantial simplification in both the analytical and numerical studies. As a first application, the nonlinear evolution of the primary signal is examined when {partial derivative}/{partial derivative}{ital l}{prime}=0 (no spatial variation of the wave amplitude and phase). The evolution equations are reduced to quadrature, and the maximum excursion of the wave amplitude {ital {cflx a}}{sub {ital s},max} is calculated analytically. Subsequently, the nonlinear evolution of the sideband instability is investigated, making use of the equations describing the self-consistent evolution of the wave amplitude {ital {cflx a}}{sub {ital s}} and phase {delta}{sub {ital s}}, which vary slowly with both space and time, together with the macroclump orbit equation.

• OSTI ID: 5992534
• Journal Information: Physics of Fluids B; (USA), Journal Name: Physics of Fluids B; (USA) Vol. 2:12; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
426002* -- Engineering-- Lasers & Masers-- (1990-)
AMPLITUDES
BEAM BUNCHING
BEAM DYNAMICS
CONFIGURATION
CORRELATIONS
ELECTRICAL EQUIPMENT
ELECTROMAGNETIC RADIATION
ELECTROMAGNETS
EQUIPMENT
FREE ELECTRON LASERS
HELICAL CONFIGURATION
INSTABILITY
LASERS
MAGNETS
NONLINEAR PROBLEMS
NUMERICAL SOLUTION
ORBITS
POLARIZATION
RADIATIONS
TRAPPING
VARIATIONS
WIGGLER MAGNETS