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

Technical Report · Wed Dec 01 00:00:00 EST 1982

OSTI ID:5881330

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 to the second power/R to the second power sub b) to the - second power and plasma return current J sub p(r)=-fJ sub b(0)(1 + r to the second power/R to the second power sub p) to the - second power, 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 0(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 to beam current (-I sub p/I sub b=fR to the second power sub p/R to the second power sub b) largely determines the stability character of the beam. Furthermore, for the same fractional current neutralization f, the modes are highly unstable for smaller ratio of plasma to beam radius R sub p/R sub b. As comparing to the resistive hose instability, the growth rates for hollowing mode could be larger than those of 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, Silver Spring, MD (USA)
• OSTI ID: 5881330
• Report Number(s): AD-A-126117/1
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAM-PLASMA SYSTEMS
PARAMETRIC INSTABILITIES
DENSITY
ELECTRON BEAMS
PINCH EFFECT
PLASMA DIAGNOSTICS
BEAMS
INSTABILITY
LEPTON BEAMS
PARTICLE BEAMS
PHYSICAL PROPERTIES
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
700107* - Fusion Energy- Plasma Research- Instabilities