Density modifications in a fusion plasma driven by the ponderomotive force

Achieving robust heating of fusion plasmas using wave energy in the ion cyclotron range of frequencies (ICRF) is closely linked to the plasma density in the antenna near field. Experimentally observed density expulsion from the region close to such RF actuators during their operation negatively impacts the coupling of power from the antenna to the plasma waves which heat or drive current. RF wave propagation depends on the properties of the edge plasma, but can in turn modify it, leading to a coupled nonlinear interaction that is currently not well understood. The ponderomotive force has been highlighted as a possible driver of the observed density modifications. This nonlinear force redistributes density where gradients in the magnitude of an oscillating electric field exist, and describes the influence of the fast time scale RF wave dynamics on slow time scale plasma transport. The complex antenna-plasma feedback system requires a self-consistent description in order to understand, and to provide predictive capability for, ICRF power delivery to the core plasma. A computer simulation which couples the cold plasma RF wave physics with a fluid plasma transport model in a one-dimensional (1D) domain parallel to a magnetic field line was developed to describe ponderomotive force e