Plasma boundary layer with an active surfaceFunded under: EAEC-FUSION 12C
In this paper the influence of electron emission from the wall (i.e. of an active surface) on the parameter of the space charge sheath is investigated, applying simple balance equations as a first step towards an explanation of the transition from a homogeneous to an inhomogeneous boundary layer. Several variations of such models are calculated, using typical plasma parameters. A crucial result is the dependence of the sheath potential and of the surface power density on the emission yield and on the net current density. Irrespective of the chosen constants, the potential drop between plasma and wall is higher the lower the electron emission and the higher the net current. The dependence of the energy flux to the wall passes a minimum and increases rapidly again near the maximum current. As a consequence, the wall loading is strongly enhanced both in the case of high negative net currents and intense electron emission, and near the maximum net current. This will tend to promote an instability of the boundary layer, resulting with high probability in the decay of the layer into plasma-induced arc spots.
Bibliographic Reference: Report: IPP 8/6 DE (1995) 32 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
Record Number: 199510865 / Last updated on: 1995-08-03
Original language: de
Available languages: de