Electrostatic shielding of vaporizing surfaces exposed to hot plasmas
Bombardment of solid surfaces by energetic plasma particles may heat them to temperatures at which melting and intense vaporization begin. The incident charge carriers, depending upon their masses and initial energies, penetrate to different depths in the vapour layer, thus setting up there, together with the resident thermal charge carriers, electric fields. Three effects are considered: the electrostatic sheath at the solid surface, the electric field distribution in the vapour layer and the electrostatic sheath forming at the vapour-plasma interface. A self-consistent model is proposed for the transition of an initially negatively biased (with respect to the plasma potential) sheath to a double layer at the vapour-plasma interface; the respective threshold conditions are defined quantitatively. The field strength in the vapour layer and the potential drop at the vapour-plasma interface are functions of the ionization state of the vapour phase and of the electron fluxes available on the two sides of the sheath. The resulting field strengths and potential drops may significantly affect the particle energies and particle fluxes, thus reducing the total energy flux incident at the surface.
Bibliographic Reference: Article: Nuclear Fusion, Vol. 36 (1996) No. 12, pp. 1679-1690
Record Number: 199710072 / Last updated on: 1997-02-26
Original language: en
Available languages: en