A general solution of the ripple-averaged kinetic equation (GSRAKE)

Abstract

A general solution of the ripple-averaged kinetic equation, GSRAKE, is presented and used to investigate neoclassical transport in the model magnetic field of a simple stellarator. No assumptions are made as to the relative sizes of the collision frequency, nu , and poloidal precessional frequency, as, so that the solution is valid throughout the entire long-mean-free-path regime. Separate but fully self-consistent treatments of both localized and non-localized particles are provided; the interaction between these two classes of particles is accounted for through a set of appropriate physical boundary conditions. All drift terms present within the framework of the ripple-averaged theory are included; in particular, for localized particles Omega theta = Omega E+ Omega Del B is comprised of both the E*B and Del B precessional frequencies. The solution is thus equally valid in the Omega E>> Omega Del B and the Omega E=0 limits of standard neoclassical theory. A detailed comparison of results with those of the FLOCS code is undertaken; estimates of neoclassical transport coefficients obtained from several codes are also presented. Agreement of results is found in all of these comparisons, GSRAKE requiring but a tiny fraction of the computational time necessary for the other codes.