Nonresonant electron transport in the ELMO Bumpy Torus experiment using a BGK operator

For the experimentally measured parameters in the ELMO Bumpy Torus (EBT) experiment, the electrons in the core plasma are nonresonant; that is, the average ∇BXB and EXB precessional drifts are in the same direction. Analytic transport rates exist for the electrons in the case where the ambipolar field is large relative to the plasma thermal energy. For finite fields, the diffusion coefficients have been calculated numerically. An analytic expansion away from the large field case that provides corrections to the results of Kovrizhnykh for finite fields has been developed from a BGK operator. These expressions are compared with the numerical calculations for parameters of experimental interest and it is shown that a substantially improved approximation over the Kovrizhnykh results can be obtained.