Formation of steep gradients with plasma detachment at grazing B-field incidence at a plasma-wall transition

Abstract

We use an Eulerian Vlasov code to study the problem of the formation of a plasma sheath with plasma detachment (i.e. no plasma transport to the wall) at a plasma-wall transition, in front of an absorbing wall. The ions are described by a kinetic equation in the full velocity space which integrates exactly the ion orbits. We consider a one-dimensional slab geometry, where the inhomogeneous direction is perpendicular to the wall. The electrons, assumed to only move along the magnetic field lines, are described by a parallel-B kinetic equation. The magnetized electrons are restricted to move along the magnetic field because the surface-parallel diamagnetic and electric drifts are equal and opposite. The present study shows how an ambipolar flow in the direction normal to the wall is established. For very small values of the angleα between the magnetic field and the plane of the wall, steep density and potential gradients are established in front of the plate surface with almost no plasma transport towards the wall.