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 magn etic field and along the cathode. A self-consistent (two spatial dimensions and three velocity components) electrostatic particle-in-cell (PIC) simula tion of a crossed-field diode produces a near-Brillouin flow which slowly e xpands across the diode, punctuated by sudden transport across the diode. T he theory of slow transport across the diode is explained by the addition o f 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 defini te mechanism behind the surface waves is established. The growth and wavele ngth of this wave are compared to PIC simulations. A slow drift compared to the shear flow is described which results from an electrostatic ponderomot ive-like force in a dc external magnetic field. The slow drift obtained fro m single particle motion compares well to the expansion of the hub in PIC s imulations. The slow expansion of the Brillouin hub leads to configurations that are not stable and quickly decay via a large transport of charge to t he anode. Both the slow transport of electrons and current spikes have been observed in experiments. (C) 2000 American Institute of Physics. [S1070-66 4X(00)91105-4].