Fusion-born alpha-particle confinement in complex 3-D magnetic fields: a comparison of particle orbit solvers

Good confinement of fusion-born alpha-particles is needed to achieve self-sustained thermonuclear burning plasmas and to avoid damage of plasma facing components of fusion reactors. Therefore, accurate modeling and simulation of alpha-particle dynamics is required to provide robust guidance on design and operation of fusion reactors.

We perform an analysis of alpha-particles confinement in both axisymmetric tokamak and 3-D stellarator magnetic fields solving the particles orbits using the guiding-center (GC) and full-orbit (FO) models. We find that GC simulations of fusion-born alpha-particles estimate lower particle losses with respect to FO simulations. We also perform a comparison of methods for solving the FO dynamics of alpha-particles while keeping all other parameters fixed, finding that different methods give different estimates of alpha-particle confinement. In each case we compute the conservation of energy and canonical toroidal momentum of particles to guide the selection of the better performing method for solving the FO dynamics of alpha-particles.