Formation mechanisms of radial electron fluxes in a positive column

The main physical formation mechanisms of differential radial electron flux es (i.e., of the fluxes which correspond to different parts of the distribu tion function) in a dc positive column are discussed. It is shown that the magnitude and even sign of these fluxes depend crucially on whether the ele ctron distribution is local or nonlocal and on electron energy. In the case of a nonlocal electron distribution the Bur of slow electrons in the body of the distribution function is directed outward (to the wall),and for the fast electrons both directions are possible. The Aux directed outward resul ts from escape of the electrons to the tube wall, and the flux directed inw ard is caused by inelastic collision with large energy losses. In the local case the flux of the fast electrons, with the exception of a small wall vi cinity, is directed inward, and the fluxes of the electrons in the distribu tion body are directed both inward and outward depending on the energy rela xation law. [S1063-651X(99)01208-8].