Trapping and ionization by plasma electrons in IFR beam propagation in the presence of an axial field
As a relativistic electron beam propagates into a plasma channel in the ion-focused regime (IFR), the plasma electrons are ejected under the influence of the beam electrostatic field. If there is an axial magnetic field, it is possible for the plasma electrons to be trapped on orbits within the drift tube radius. These trapped electrons are highly energetic (compared to ionization energies) and thus for long pulse beams it is possible that the channel density would vary as a function of time due to ionization by the trapped electrons. It is also possible that plasma electrons trapped in the vicinity of the beam would cause electron-electron instabilities. Trapping and ionization by plasma electrons is considered in this paper. First, we derive a transcendental equation for the electron trapping radius in terms of the beam parameters and the external field. We then find an expression for the time-averaged plasma electron density profile in the presence of the relativistic beam. Finally, we estimate the ionization rate by these electrons. In the following analysis, it is assumed that only the beam electrostatic forces act on the plasma electrons; that is, forces due to channel ions and electrons are neglected. This limits the applicability of the analysis to problems with small neutralization fractions. We also neglect electrodynamic effects. 1 ref., 2 figs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6854336
- Report Number(s):
- SAND-88-2414C; CONF-8809149-2; ON: DE89000454
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
700103* -- Fusion Energy-- Plasma Research-- Kinetics
ANGULAR MOMENTUM
BEAMS
ELECTRIC FIELDS
ELECTRON BEAMS
ELECTRON DENSITY
ELECTRONS
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
INSTABILITY
IONIZATION
LEPTON BEAMS
LEPTONS
MAGNETIC FIELDS
PARTICLE BEAMS
PLASMA INSTABILITY
RELATIVISTIC RANGE
TRAPPED ELECTRONS