Ion cyclotron resonance heating induced transport in stellarators and other asymmetric toroid

A Monte Carlo simulation is developed to model minority ion transport and fundamental ion cyclotron resonance heating (ICRH) in asymmetric magnetic field geometries. A discrete event model is used to superimpose resonance heated nonadiabatic changes in an ion's magnetic moment on a Coulomb scattering model that contains the Spitzer coefficients of drag, velocity diffusion, and pitch angle scattering (PAS). Ion drift orbit equations of motion are set in a magnetic flux coordinate system which separate fast motion along the field lines from slow motion across the lines.;The effects of ICRH on minority ion transport are investigated for helium-3 ions in stellarator plasmas. The energy distribution functions of these RF-heated ions develop high energy tails as a result of a preferential gain in velocity in the direction perpendicular to the ambient magnetic field. Estimates of neoclassical flux surface diffusion coefficients indicate that ion losses in a RF-heated stellarator plasma can be increased by as much as ten times non-ICRH ion losses. This can be attributed to an RF-increased fraction of trapped ions which results in increased neoclassical transport across the toroidal flux surfaces.