Axisymmetric instability of a self-pinched beam with rounded radial density profile

Journal Article · Tue Nov 01 04:00:00 EST 1983 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.864077· OSTI ID:5537704

Chen, H C; Uhm, H S

The axisymmetric perturbations (sausage and hollowing modes) of an intense relativistic self-pinched electron beam propagating in a resistive plasma background are studied, especially for a beam with rounded radial density profile. The Bennett profiles are assumed for both the equilibrium beam current J/sub b/(r) = J/sub b/(0) (1+r/sup 2//R/sup 2//sub b/)/sup -2/ and plasma return current J/sub p/(r) = -fJ/sub b/(0) (1+r/sup 2//R/sup 2//sub p/)/sup -2/, where R/sub b/ and R/sub p/ are the characteristic radii of the beam and plasma return currents, respectively. It is further assumed that the electric conductivity sigma(r) of the plasma channel is proportional to the return current. For a paraxial electron beam with complete space-charge neutralization by the ambient plasma, the axisymmetric modes can be destabilized by the phase lag between the magnetic field and beam current, even without the plasma return current. The plasma return current significantly modifies the growth rate of the instability such that the ratio of plasma current to beam current (-I/sub p//I/sub b/ = fR/sup 2//sub p// iR/sup 2//sub b/) largely determines the stability character of the beam. Furthermore, for the same fractional current neutralization f, the modes are highly unstable for a smaller ratio of plasma to beam radius R/sub p//R/sub b/. As compared to the resistive hose instability, the growth rates for the hollowing mode can be larger than those of the hose mode, while the sausage mode is much stabler than the hose mode. Stability properties are illustrated in detail for various system parameters.

• Research Organization: Naval Surface Weapons Center, White Oak, Silver Spring, Maryland 20910
• OSTI ID: 5537704
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 26:11; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107* -- Fusion Energy-- Plasma Research-- Instabilities
700108 -- Fusion Energy-- Plasma Research-- Wave Phenomena
BEAM CURRENTS
BEAM-PLASMA SYSTEMS
BEAMS
CURRENTS
DISTRIBUTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON BEAMS
ELECTRON DENSITY
ENERGY RANGE
EQUILIBRIUM
HOSE INSTABILITY
INSTABILITY
INSTABILITY GROWTH RATES
LEPTON BEAMS
PARTICLE BEAMS
PHYSICAL PROPERTIES
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PLASMA MICROINSTABILITIES
RELATIVISTIC RANGE
SAUSAGE INSTABILITY
SPACE CHARGE
STABILITY