Linear analysis of a free-electron laser coupled to betatron oscillations

Journal Article · Sun Oct 01 04:00:00 EDT 1989 · Physics of Fluids B: Plasma Physics; (USA)

DOI:https://doi.org/10.1063/1.859073· OSTI ID:5648335

Latham, P E ^[1]

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1. Laboratory for Plasma Research, University of Maryland, College Park, Maryland 20742 (US)

The dispersion relation is derived for the interaction of a sheet beam propagating between parallel plates in a planar wiggler magnetic field. Instead of the usual free electron laser (FEL) mode, one is considered in which the radiation field is perpendicular to the quiver velocity and couples either to betatron or plasma oscillations. In the cold beam limit, coupling to betatron oscillations leads to an absolute instability. This mode competes with the conventional FEL and can disrupt the beam unless suppressed. The effects of energy spread are investigated, and a critical energy spread is found that suppresses the instability. For ultrarelativistic beams, this energy spread is an exponentially decreasing function of the beam energy. For moderately relativistic high current beams, it is proportional to the square root of the beam current. In this regime, there is a limit to the current that can propagate stably in the FEL circuit. Coupling to plasma oscillations also leads to an instability. However, the instability associated with this mode can be made convective with a suitable choice of parameters, and thus is not particularly dangerous to the conventional FEL. It is, however, interesting because the dispersion relation is characteristic of a second harmonic FEL, even though the wiggler is planar.

• OSTI ID: 5648335
• Journal Information: Physics of Fluids B: Plasma Physics; (USA), Journal Name: Physics of Fluids B: Plasma Physics; (USA) Vol. 1:10; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
ABSOLUTE INSTABILITIES
ACCELERATORS
BEAMS
BETATRONS
COUPLING
CYCLIC ACCELERATORS
DISPERSION RELATIONS
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
ELECTRON BEAMS
ELECTRONIC EQUIPMENT
ENERGY RANGE
EQUIPMENT
FREE ELECTRON LASERS
HARMONICS
INSTABILITY
LASERS
LEPTON BEAMS
MAGNETS
OSCILLATIONS
OSCILLATORS
PARTICLE BEAMS
PLASMA INSTABILITY
PLATES
RELATIVISTIC RANGE
SHEETS
WIGGLER MAGNETS