A Single Ray Approximation for α Particle Transport

Abstract

We report the development of a one-ray approximation for the numerical transport of 3.5 MeV α particles generated in DT fusion reactions. Similar in spirit to techniques used in photon transport, this method provides respectable accuracy at potentially large savings in time and storage when compared to multigroup diffusion, S n , or Monte Carlo techniques. The approximation works in a restricted, but large, class of plasmas, those in which scattering of the α's and bending of their trajectories by magnetic fields can be neglected. Test cases in planar, cylindrical, and spherical geometry are presented. In another calculation it is demonstrated that the achievement of ignition in an imploding Z pinch may depend sensitively on the degree to which a magnetic field confines the α particles in the dense central core.