Variational corrections to ELMO Bumpy Torus neoclassical ion plateau transport

Low collisionality corrections to ELMO Bumpy Torus (EBT) ion plateau transport coefficients are calculated using a variational method. Using a bounce-averaged drift kinetic equation and a drift orbit model appropriate to collisionless EBT ion transport, a solution is obtained that is accurate to first order in ∈(Ω₀/ν₀)^2/3 (∈ is the inverse aspect ratio, ν₀ is the 90° deflection frequency, and Ω₀ is the average poloidal gradient B drift frequency). This is substituted into a variational principle (valid over both the plateau and banana regimes) from which particle and energy fluxes are obtained. The sensitivity of the transport rates with respect to variations in the radial and poloidal components of the ambipolar electric field and with respect to variations in the poloidal drift frequency scale length is examined. The transition from plateau to crescent orbit scaling occurs at approximately ν₀/Ω₀ = ∈^3/2.