Gravitational Effect on Release Conditions of Dust Particle from Plasma-Facing Wall

Abstract

The effect of the gravitational force on release conditions of a spherical dust particle from a plasma-facing wall is studied by one-dimensional analysis. For release of the dust, where the gravitational force is directed toward the wall, the strong enough electric field is required and these exists the threshold wall potential, which does not depend on the plasma quantities, but the shape of the dust particle. At the deeper wall potential than the threshold, we found the critical dust radius for release, where the dust smaller than the critical one is released by the repulsive electrostatic force. The gravitational force decreases the critical radius of the release. In the case of the gravitational force directed from the wall, the dust particle is released by the gravitational force even if the applied potential is shallower than the threshold one. From this analysis we found that the size of the released dust particle is controllable by adjusting the plasma parameters such as plasma density and temperature as well as biasing the wall potential.