Surface wave enhanced collisionless transport in a bounded crossed-field non-neutral plasma

Electron transport across the magnetic field in a cutoff planar smooth-bore diode is described on the basis of surface waves perpendicular to the magnetic field and along the cathode. A self-consistent (two spatial dimensions and three velocity components) electrostatic particle-in-cell (PIC) simulation of a crossed-field diode produces a near-Brillouin flow which slowly expands across the diode, punctuated by sudden transport across the diode. The theory of slow transport across the diode is explained by the addition of perturbed orbits to the Brillouin shear flow motion of the plasma in the diode. The wave results from the sheared flow instability, so that a definite mechanism behind the surface waves is established. The growth and wavelength of this wave are compared to PIC simulations. A slow drift compared to the shear flow is described which results from an electrostatic ponderomotive-like force in a dc external magnetic field. The slow drift obtained from single particle motion compares well to the expansion of the hub in PIC simulations. The slow expansion of the Brillouin hub leads to configurations that are not stable and quickly decay via a large transport of charge to the anode. Both the slow transport of electrons and current spikes have been observed in experiments. (C) 2000 American Institute of Physics. [S1070-664X(00)91105-4].