Evaluation of relativistic transport coefficients and the generalized Spitzer function in devices with 3D geometry and finite collisionality

Abstract

The relativistic generalization of the linearized drift kinetic equation solver NEO-2 is presented which is used for computation of neoclassical transport coefficients and the generalized Spitzer function in 3D toroidal fusion devices (tokamaks and stellarators). This upgrade allows computations of the Spitzer function playing the role of current drive efficiency in the whole experimentally relevant temperature range, from mild temperatures where finite plasma collisionality effects are important to high temperatures where relativistic effects should be taken into account. Within the Galerkin method used for problem discretization over energy, relativistic effects are included into a set of matrices constant on a flux surface. Those matrices determine coefficients of a coupled set of integro-differential equations with a reduced dimension which is of the same form as in the non-relativistic case. For energy discretization of the linearized relativistic Coulomb collision operator, it is presented in spherical momentum space variables in the symmetric integral form derived directly from Beliaev-Budker expressions. The cancellation problem pertinent to the fully analytical representation of Braams and Karney [Phys. Fluids B 1, 1355 (1989)] does not appear in this form. Examples of evaluation of relativistic transport coefficients and the Spitzer function are presented.