Neoclassical transport coefficients for a bumpy torus have been calculated by solving a bounce-averaged drift kinetic equation locally in radius. In contrast with previous work, where the ambipolar field was assumed to be large relative to the plasma thermal energy (ejϕ/kTj ≫ 1), finite electric fields are considered here [ejϕ/kTj = 0(1)]. Both the Landau operator and the particle and energy-conserving BGK model operator have been used, and a comparison of the two sets of results indicates reasonable agreement. The resulting transport coefficients exhibit a strong dependence on the ambipolar field and on plasma collisionality; in the large-field limit, the present results correlate closely with earlier work.
Stochastic magnetic and ambipolar electric fields in the plasma edge region of RFX