Influence of Trapped Electrons on the Plasma Potential in the Expander of an Open Trap

The influence of electrons trapped between the magnetic mirror and the Debye sheath on the potential profile in the expander of an open trap is considered. A numerical model is developed to calculate the electron distribution function in the self-consistent electrostatic potential. Passing electrons are assumed to be collisionless, while the distribution function of trapped electrons is calculated by solving the bounce-averaged kinetic equation with the Landau collision integral. The self-consistent profile of the potential is obtained. The solution is shown to agree well with Ryutov’s semi-analytical model.