Boundary conditions including sheath effects at a plasma-facing surface

It has recently been reported that space-charge saturation occurs adjacent to almost every commonly used plasma-facing material for plasma temperatures above {~}50 eV. An electron emission coefficient, defined as the average number of surface-emitted electrons per incident plasma electron, which is near or above unity is responsible for the occurrence of space-charge saturation. With this motivation, a fully kinetic self-consistent theory capable of describing the plasma sheath under conditions of space-charge saturation is developed. The theory is then used to obtain boundary conditions which are suitable for incorporation into computer programs which simulate plasmas.