Longitudinal losses from a mirror trap: When neither kinetic nor collisional

Steady-state losses of a plasma from a mirror trap in an L∼λ/R regime existing between the kinetic and collisional extremities have been explored (λ is the mean free path; L is the trap length, R is the mirror ratio). A numerical scheme has been developed to treat the kinetic equation. The self-consistent ambipolar plasma potential has been calculated by an iteration procedure. The L∼λ/R regime, in which the ions escaping from the trap form a relatively narrow “beam” in velocity space, has been explored. A self-consistent analytical solution for point mirrors has been derived. Suppression of longitudinal ion losses using an ambipolar mirror has been modeled. It has been shown that once that “beamed” regime has settled in, losses can be substantially suppressed even when the ambipolar barrier is not too high.