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A model using nonlinear fluid equations is presented for describing the physics behind the operation of crossed field amplifiers (CFAs). The model, which is based on electron guiding center orbits, showed the dependence of the electron hub density on the radio frequency (RF) amplification and saturation processes. The passage of a single RF signal through the CFA is discussed along with multipass, steady-state behavior and experimental results.

Electron acceleration by an intense electromagnetic wave incident obliquely to the ambient magnetic field in a plasma is considered. It is shown that the wave amplitude has a stochasticity inducing threshold. Although substantial acceleration can be achieved below this threshold, it is limited to the trapping width of a single resonance. Above threshold, the electrons can accelerate from resonance to resonance. It is also shown that when the parallel phase velocity of the electromagnetic waves is supraluminous, the Hamiltonian surfaces describing the wave-particle interaction are topologically open. In this case, electrons gain large amounts of energy. The mechanism is quite robust, being weakly sensitive to changes in the wave parameters and the electron's initial energy; as a result, it is an ideal mechanism for space applications. As an application, the conditions are obtained for accelerating electrons to energies of several MeV using ground-based transmitters. [ABSTRACT FROM AUTHOR]

Current conduction through a low density (∼1012 cm-3) collisionless plasma injected between two coaxial conducting cylinders is simulated using a 2 (1)/(2) -D, electromagnetic particle-in-cell code. Plasma is injected through the anode towards the cathode with flow velocity, VF, and is assumed to be azimuthally symmetric. Current is driven through the plasma so that the 100 kA level is reached in [bar_over_tilde:_approx._equal_to]5 nsec. The opening process, when current is diverted to a load, is also treated. Electrons are found to carry current in a narrow current channel across the plasma by E×B drift. A large electric field is established by charge separation in the plasma in order to provide the drift. The motion of the anode end of the current channel controls the time of opening and is found to be independent of VF and to depend strongly on density and length. [ABSTRACT FROM AUTHOR]

The stability of high-power magnetically insulated ion diodes is investigated. Interactions between the fields, the electron flow, and the ion beam in the diode gap lead to instabilities. These instabilities are (i) low-frequency (below electron plasma frequency) instabilities that include a two-stream type instability at ω≊0 and ion transit time instabilities at finite frequency, and (ii) high-frequency instabilities (also called ‘‘magnetron instabilities’’) at a frequency above the electron plasma frequency. Under certain experimental conditions, one of the ion transit time instabilities is found to be broadbanded and may become absolutely unstable. Analysis based on realistic parameters shows the elimination of this broadband instability at diode operation close to insulation threshold, and implications of this finding are discussed. [ABSTRACT FROM AUTHOR]

The short wavelength limit of the magnetron instability of a relativistic sharp boundary electron sheath is examined. For short wavelengths the mode is localized to the sheath edge. This localization leads to a simple relationship (essentially a Lorentz transformation) between the relativistic and nonrelativistic growth rates. This relationship involves only equilibrium quantities evaluated at the sheath edge and explains previously noted trends that have been observed numerically. [ABSTRACT FROM AUTHOR]

Magnetically insulated ion diodes are examined for instability using analytical and numerical techniques. Two basic sources which drive instability are found: one due to a two-stream-type interaction between electrons and ions and the other due to ion transit time effects. [ABSTRACT FROM AUTHOR]