In this paper a model of the quasineutral plasma and the transition between
the plasma and the dielectric wall in a Hall thruster channel is developed
. The plasma is considered using a two-dimensional hydrodynamic approximati
on while the sheath in front of the dielectric surface is considered to be
one dimensional and collisionless. The dielectric wall effect is taken into
account by introducing an effective coefficient of the secondary electron
emission (SEE), s. In order to develop a self-consistent model, the boundar
y parameters at the sheath edge (ion velocity and electric field) are obtai
ned from the two-dimensional plasma bulk model. In the considered condition
, i.e., ion temperature much smaller than that of electrons and significant
ion acceleration in the axial direction, the presheath scale length become
s comparable to the channel width so that the plasma channel becomes an eff
ective presheath. It is found that the radial ion velocity component at the
plasma-sheath interface varies along the thruster channel from about 0.5C(
s) (C-s is the Bohm velocity) near the anode up to the Bohm velocity near t
he exit plane dependent on the SEE coefficient. In addition, the secondary
electron emission significantly affects the electron temperature distributi
on along the channel. For instance in the case of s=0.95, the electron temp
erature peaks at about 16 eV, while in the case of s=0.8 it peaks at about
30 eV. The predicted electron temperature is close to that measured experim
entally. The model predictions of the dependence of the current-voltage cha
racteristic of the ExB discharge on the SEE coefficient are found to be con
sistent with experiment. (C) 2001 American Institute of Physics.