Propagation of a nonrelativistic electron beam in a plasma in a magnetic field

The interaction of electron beams with a large variety of materials for information storage has been the subject of numerous proposals and studies in the recent literature. The materials range from photographic to thermoplastic and magnetic, and the interactions with the electron beam for writing and reading the information utilize the energy, or the current, or even the magnetic field associated with the electron beam.

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Double layers in the downward current region of the aurora

Nonlinear Processes in Geophysics ◽

10.5194/npg-10-45-2003 ◽

2003 ◽

Vol 10 (1/2) ◽

pp. 45-52 ◽

Cited By ~ 32

Author(s):

R. E. Ergun ◽

L. Andersson ◽

C. W. Carlson ◽

D. L. Newman ◽

M. V. Goldman

Keyword(s):

Magnetic Field ◽

Electron Beam ◽

Phase Space ◽

Electric Field ◽

Electric Fields ◽

Double Layers ◽

Parallel Electric Field ◽

Electrostatic Waves ◽

Current Region ◽

Decisive Evidence

Abstract. Direct observations of magnetic-field-aligned (parallel) electric fields in the downward current region of the aurora provide decisive evidence of naturally occurring double layers. We report measurements of parallel electric fields, electron fluxes and ion fluxes related to double layers that are responsible for particle acceleration. The observations suggest that parallel electric fields organize into a structure of three distinct, narrowly-confined regions along the magnetic field (B). In the "ramp" region, the measured parallel electric field forms a nearly-monotonic potential ramp that is localized to ~ 10 Debye lengths along B. The ramp is moving parallel to B at the ion acoustic speed (vs) and in the same direction as the accelerated electrons. On the high-potential side of the ramp, in the "beam" region, an unstable electron beam is seen for roughly another 10 Debye lengths along B. The electron beam is rapidly stabilized by intense electrostatic waves and nonlinear structures interpreted as electron phase-space holes. The "wave" region is physically separated from the ramp by the beam region. Numerical simulations reproduce a similar ramp structure, beam region, electrostatic turbulence region and plasma characteristics as seen in the observations. These results suggest that large double layers can account for the parallel electric field in the downward current region and that intense electrostatic turbulence rapidly stabilizes the accelerated electron distributions. These results also demonstrate that parallel electric fields are directly associated with the generation of large-amplitude electron phase-space holes and plasma waves.

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Investigation of plasma parameters created by a fast electron beam in a magnetic field

Vacuum ◽

10.1016/0042-207x(71)90093-5 ◽

1971 ◽

Vol 21 (8) ◽

pp. 355

Keyword(s):

Magnetic Field ◽

Electron Beam ◽

Fast Electron ◽

Plasma Parameters ◽

Fast Electron Beam

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Compton and Raman free electron laser stability properties for a cold electron beam propagating through a helical magnetic wiggler

Journal of Plasma Physics ◽

10.1017/s0022377800002580 ◽

1985 ◽

Vol 33 (3) ◽

pp. 387-423 ◽

Cited By ~ 10

Author(s):

John A. Davies ◽

Ronald C. Davidson ◽

George L. Johnston

Keyword(s):

Magnetic Field ◽

Electron Beam ◽

Dispersion Relation ◽

Free Electron ◽

Free Electron Laser ◽

Relativistic Electron Beam ◽

Cold Electron ◽

Wiggler Magnetic Field ◽

Laser Stability

This paper gives an extensive characterization of the range of validity of the Compton and Raman approximations to the exact free electron laser dispersion relation for a cold, relativistic electron beam propagating through a constantamplitude helical wiggler magnetic field. The electron beam is treated as infinite in transverse extent. Specific properties of the exact and approximate dispersion relations are investigated analytically and numerically. In particular, a detailed numerical analysis is carried out to determine the range of validity of the Compton approximation.

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