Effects of neutral beam injection on poloidal rotation and energy transport in tokamaks

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Abstract
The poloidal mass flow and ion energy transport driven by friction between thermal ions and fast ions resulting from neutral beam injection are investigated. Transport coefficients are derived which relate the poloidal mass flow and the radial ion heat flux to the fast ion friction and the radial temperature gradient. An Onsager symmetry condition shows that the coefficient of the fast ion friction in the radial heat flux is the negative of the coefficient of the temperature gradient in the poloidal mass flow. Numerical results are given for the banana regime. The driven poloidal mass flow can be significantly larger than the standard neoclassical poloidal rotation driven by the ion temperature gradient. The resulting viscous heating of the ions can be larger than the standard neoclassical ion heat conduction term in the ion energy equation. The driven ion energy flux contains a convective contribution, due to the diffusional mixing of the fast ions and thermal ions. This energy flux is inward (a heat pinch) in the case of coinjection, and can be significantly larger than the standard neoclassical energy flux.