Moment approach to fast ion neoclassical transport and viscous forces

Fast ion drift kinetic equation is analytically solved in banana regime using a pitch-angle scattering eigenfunction expansion method. The analytical solution of this eigenfunction is made feasible by adopting Cordey's model [Nucl. Fusion 16, 499 (1976)] whereof the flux-surface averaged pitch-angle <νparallel/ν> is replaced by ξ, the pitch-angle at the minimum magnetic field. Then, the flux-surface averaged parallel viscous and heat viscous forces, and , are calculated from the drift-kinetic solution to provide the key closure moments which give rise to radial neoclassical transport and bootstrap current. In combination with the recently derived fast ion friction forces, a moment approach is schemed for fusion plasmas with significant fraction of fast ion component. A new orthogonal polynomial expansion method is presented for the fluid flow distortion from an isotropic distribution and applied to expressing the friction forces between fast ions and thermal ions. (author)