Theory of plasma-wall transition with account of variable ion temperature

The fluid model describing a transition from a weakly ionized collision-dominated plasma to a negative wall is supplemented with the ion energy equation, accounting for thermal energy exchange with atoms, expansion/compression work, and heating due to conversion of kinetic energy of the ion flow into thermal energy in collisions of ions with atoms. An asymptotic solution is obtained for the limit case when the Debye length is much smaller than the mean free path for collisions ion-neutral. If the electron temperature exceeds the temperature of the atoms, the distribution of the ion temperature in the (quasineutral) Knudsen layer is nonmonotonic. In the case when the electron temperature exceeds the temperature of the atoms by two orders of magnitude or more, the ion temperature in the bulk of the Knudsen layer exceeds substantially the atom temperature, although it does not exceed about 8% of the electron temperature. (C) 2000 American Institute of Physics. [S1070-664X(00)00801-6].