Free electron laser instability for a relativistic solid electron beam in a helical wiggler field
The free electron laser instability for a solid relativistic electron beam propagating in combined transverse helical wiggler and uniform axial guide fields is investigated within the framework of the linearized Vlasov--Maxwell equations. It is assumed that ..nu../..gamma../sub b/<<1, where ..nu.. is Budker's parameter and ..gamma../sub b/mc/sup 2/ is the electron energy. Stability properties are investigated for the choice of equilibrium distribution function in which all electrons have the same value of the linear combination of transverse and helical invariants, C/sub perpendicular/ -2..gamma../sub b/m..omega../sub b/C/sub h/ = const., and a Lorentzian distribution in the axial invariant C/sub z/. (Here ..omega../sub b/ is a constant.) The instability growth rate is calculated including a determination of the optimum value of the ratio of beam radius to conducting wall radius (R/sub 0//R/sub c/) for maximum growth. It is found that the maximum growth rate for a solid electron beam is comparable to that for a hollow beam with similar parameters. Moreover, the introduction of a small axial momentum spread (..delta../..gamma../sub b/mcroughly-equal a few percent) significantly reduces the instability growth rate.
- Research Organization:
- Naval Surface Weapons Center, White Oak, Silver Spring, Maryland 20910
- OSTI ID:
- 6535124
- Journal Information:
- Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 26:1; ISSN PFLDA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
420300* -- Engineering-- Lasers-- (-1989)
BEAMS
BOLTZMANN-VLASOV EQUATION
CONFIGURATION
DIFFERENTIAL EQUATIONS
DISTRIBUTION FUNCTIONS
ELECTRICAL EQUIPMENT
ELECTROMAGNETS
ELECTRON BEAMS
ENERGY RANGE
EQUATIONS
EQUILIBRIUM
EQUIPMENT
FREE ELECTRON LASERS
FUNCTIONS
HELICAL CONFIGURATION
INSTABILITY
LASERS
LEPTON BEAMS
MAGNETIC FIELDS
MAGNETS
PARTIAL DIFFERENTIAL EQUATIONS
PARTICLE BEAMS
RELATIVISTIC RANGE
WIGGLER MAGNETS